Patent Application
20180207716
The present invention relates to a sand moulding machine for the production of sand mould parts including a moulding chamber formed by a chamber top wall, a chamber bottom wall, two opposed chamber side walls and two opposed chamber end walls, wherein a chamber wall is provided with at least one sand filling opening, wherein at least one of the chamber end walls is provided with a pattern plate having a pattern adapted to form a pattern in a sand mould part, wherein at least one of the chamber end walls is displaceable in a longitudinal direction of the moulding chamber in order to compact sand fed into the moulding chamber, wherein at least one of the pattern plates is associated with at least one reference pattern block positioned in fixed relationship to the pattern of said pattern plate and adapted to form a reference pattern in an external face of a sand mould part, and wherein a non-contact detection system is arranged adjacent a path of travel of the compacted sand mould parts and is adapted to detect a position of a pattern face of the reference patterns of the sand mould parts.
On automated moulding machines, two different types of machines or techniques are often used; the match plate technique such as employed by DISA MATCH (Registered Trademark) horizontal flaskless match plate machines and the vertical sand flaskless moulding technique such as the DISAMATIC (Registered Trademark) technique.
According to the match plate technique, a match plate having moulding patterns on both sides facing away from each other is being clamped between two moulding chambers. During the simultaneous moulding of a first and a second sand mould half part, the patterns of the match plate are extending into each respective moulding chamber. A slit-formed sand inlet opening extending across a wall is arranged at each moulding chamber.
Simultaneously sand is blown in through each slit-formed opening and into each moulding chamber. Thereafter, the sand is being squeezed by the movement of oppositely arranged press plates being displaced simultaneously in direction towards the match plate. After the squeezing, the moulding chambers are moved away from each other, the match plate is being removed and eventually cores are placed in the moulds. The moulds are then closed and pushed out of the chamber and are ready for pouring liquid metal therein in order to produce metal castings.
According to the vertical flaskless sand moulding technique such as the DISAMATIC (Registered Trademark) technique, a first and a second plate, each provided with a pattern plate, are arranged oppositely at either end of a moulding chamber. During the moulding of a single mould part the patterns of the pattern plates are extending into each respective end of the moulding chamber. A slit-formed sand inlet opening extending across a wall is arranged typically at the top of the moulding chamber.
Sand is blown in through the slit-formed opening and into the moulding chamber. Thereafter, by displacement of the first and/or the second plate, the plates move relatively in direction towards each other and squeeze the sand therebetween. After being removed from the moulding chamber, the sand mould part is placed adjacent the previously moulded sand mould part on a conveyer. Thereby, two neighbouring sand mould parts form a complete sand mould. The cavity formed by these two sand mould parts constitutes a cavity for the subsequent casting of the metal product.
U.S. Pat. No. 4,724,886 (Selective Electronic, Inc.) discloses an apparatus and method for detecting the misalignment of cooperating mould sections during operation of a mould making machine. The mould making machine includes a device for forming a rectangular reference mark on the exterior of the mould surface and a non-contact distance measuring device for detecting the misalignment of the internal mould cavities of the mould sections by detecting any misalignment as a step between two adjacent external reference marks. The distance measuring device initially detects a step increase in the measured distance as the reference mark passes into the field of view of the measuring device. If, during the time that the reference mark is within the field of view, this distance changes in a stepwise manner in an amount greater than a previously established threshold tolerance, this indicates an internal misalignment and the operator is signalled, through a display on the system control unit. The operator then has a choice of stopping the advancement of the mould sections and correcting the problem causing the misalignment, or the operator may wait and see if the misalignment was an isolated problem or a persistent problem by checking several subsequent mould sections for misalignment before stopping the production line. However, according to this method, the accuracy of the distance measurement is limited, and an indication of misalignment is only given if a distance change greater than a threshold tolerance is measured. A measure for the degree of misalignment is not indicated to the operator. Furthermore, although this arrangement may detect vertical, lateral and rotational mutual misalignment of adjacent mould sections, other parameters such as the width of a possible gap between adjacent mould sections, mould expansion and mould dimensions cannot be detected by this arrangement.
U.S. Pat. No. 5,697,424 (Dansk Industri Syndikat A/S) describes an automatically operating moulding and casting plant comprising a moulding station for producing moulds by compressing moulding sand, a pouring station and an extraction station. It may happen, without the operator immediately noticing it, that when the newly compacted mould part is released from the pattern or patterns, against which it has been formed by compressing moulding sand, some moulding sand adheres to the pattern, thereby producing an error in the form of a recess in the casting cavity formed. In order to detect such situations, a number of video cameras depicting one or a number of process steps and/or the results of the same transmit the corresponding image information to central control means, in which the image information is compared to “ideal” image information, e.g. image information previously read-in and based on a process step proceeding correctly. On the basis of the results of the comparison, the central control means controls the affected stations in such a manner that undesired operational states or defective castings are avoided. However, this method may not provide sufficiently accurate information about mutual misalignment of adjacent mould sections, such as for instance vertical, lateral and rotational mutual misalignment and the width of a possible gap between adjacent mould sections. Furthermore, mould expansion and mould dimensions cannot be detected very accurately by this arrangement.
JP4190964A discloses a flaskless casting line provided with a sand moulding machine. The boundary area between adjacent sand moulds conveyed on an intermittent conveyor in the sand mould line is picked up by TV cameras, and the video signals are processed. Thereby, the boundary line between the adjacent sand moulds is decided, and the length of the sand mould in the feeding direction is decided by a width between two boundary lines in the feeding direction. In this way, the position of an arbitrary sand mould in the sand mould line on the intermittent conveyor can be decided based on this sand mould length. However, although the thickness of sand moulds may be determined in this way, inaccuracies such as vertical, lateral and rotational mutual misalignment of adjacent mould parts, as well as other parameters such as the width of a possible gap between adjacent mould parts cannot be detected by this system.
U.S. Pat. No. 4,774,751 relates to foundry procedures, particularly in-process and post process inspection with electro-optical sensor units. Principally addressed are: inspection of moulds and cores to assure correctness and control procedures to abort pouring if the moulds are not correct, inspection of cores on the core line, inspection of patterns for sticking sand, inspection of finished castings for extraneous material in passages, excessive or inadequate stock, correct locator relationships, etc., and control of robotic flash grinders. Disclosed is a system to inspect moulds on a continuous mould line for any or all of the following: cores are complete (not missing pieces), cores are properly positioned in drag mould (alignment, height), sand in moulds is correct size and no damage, pins and pin holes in cope and drag mould are correct size and in good enough condition to allow proper mating. Both fixed and programmably moveable sensors are shown in the context of these embodiments. However, this system is not able to detect inaccuracies relating to the mutual positioning of two mould parts forming a complete mould, such as vertical, lateral and rotational mutual misalignment of adjacent mould parts, as well as other parameters such as the width of a possible gap between adjacent mould parts.
DE 42 02 020 A1 discloses a process for positioning the bottom pouring hole of a casting system above the sprue of a mould in a boxless mould making and converging system. The pouring hole position above the sprue is inspected and position errors are detected, as soon as a mould making and conveying operation is ended and the mould is at rest. The positioning equipment includes (i) a measuring system for determining the pouring hole position above the sprue; (ii) a positioning system for longitudinal and transverse adjustment of the casting system with respect to the conveyor system; and (iii) a measurement processing system for controlling the positioning system. The measuring system may have the form of video, laser, radar or ultrasonic camera and is provided with an attached measuring variable processing system. The process is useful in the casting of metal articles in boxless moulds as it allows casting to be carried out without delay and compensates for tolerances in the mould thickness and within the conveyor system for rapid and precise pouring hole positioning.
The object of the present invention is to provide a sand moulding machine and a method of producing sand mould parts, whereby more accurate detection of mutual misalignment of adjacent sand mould parts may be provided.
In view of this object, the at least one reference pattern block includes a face having a tangent varying in the longitudinal direction of the moulding chamber and being adapted to form a corresponding reference pattern including a pattern face having a tangent varying in a corresponding longitudinal direction of the sand mould part, the non-contact detection system is adapted to detect the position of a number of different points distributed over the pattern face of the reference pattern in the longitudinal direction of the sand mould part, and the tangent in the longitudinal direction of the sand mould part is different between at least two of said points.
In this way, based on the detection of the position of a number of different points distributed over the pattern face of the reference pattern, the position and orientation of a known curve representing the pattern face may be determined or estimated, and on the basis thereof, the position or positions of one or more reference points for said known curve may be determined or estimated. The position of such reference points may be compared to the ideal or theoretic position of the reference points. Thereby, mutual misalignment of adjacent sand mould parts may be detected very accurately. Furthermore, among other parameters, the width of a possible gap between adjacent sand mould parts, mould expansion and mould dimensions may be detected by this arrangement. It may thereby be assessed whether the actual situation is acceptable or not.
In an embodiment, the at least one reference pattern block includes a face having a tangent varying in a height direction of the moulding chamber and being adapted to form a corresponding reference pattern including a pattern face having a tangent varying in a corresponding height direction of the sand mould part, in that the non-contact detection system is adapted to detect the position of a number of different points distributed over the pattern face of the reference pattern in the height direction of the sand mould parts, and in that the tangent in the height direction of the sand mould parts is different between at least two of said points. Thereby, by means of a single reference pattern block, the actual three-dimensional position of a point in a corner of a sand mould part may be determined.
In an embodiment, the at least one reference pattern block includes a first face part having a first tangent at a first position in the longitudinal direction of the moulding chamber and a second face part having a second tangent at a second position in the longitudinal direction of the moulding chamber, the second tangent is different from the first tangent, the first and second face parts are adapted to form a corresponding reference pattern including a first pattern face part having a first pattern tangent at a first position in the longitudinal direction of the sand mould part and a second pattern face part having a second pattern tangent at a second position in the longitudinal direction of the sand mould part, the second pattern tangent is different from the first pattern tangent, and the non-contact detection system is adapted to detect the position of a number of different points distributed at least substantially evenly over both the first and the second pattern face part of the reference pattern in the longitudinal direction of the sand mould part.
In an embodiment, the at least one reference pattern block includes a third face part having a third tangent at a third position in the height direction of the moulding chamber and a fourth face part having a fourth tangent at a fourth position in the height direction of the moulding chamber, wherein the fourth tangent is different from the third tangent, wherein the third and fourth face parts are adapted to form a corresponding reference pattern including a third pattern face part having a third pattern tangent at a third position in the height direction of the sand mould part and a fourth pattern face part having a fourth pattern tangent at a fourth position in the height direction of the sand mould part, wherein the fourth pattern tangent is different from the third pattern tangent, and in that the non-contact detection system is adapted to detect the position of a number of different points distributed at least substantially evenly over both the third and the fourth pattern face part of the reference pattern in the height direction of the sand mould part.
In an embodiment, the at least one reference pattern block includes a spherically symmetric face. The centre of the corresponding spherically symmetric pattern face of the reference pattern may serve as a reference point for the reference pattern.
In an embodiment, the at least one reference pattern block includes a set of at least two flat faces following one after the other in the longitudinal direction of the moulding chamber and being adapted to form a corresponding reference pattern including a set of at least two flat surfaces following one after the other in the corresponding longitudinal direction of the sand mould part, wherein each flat face is arranged at an oblique angle to another one of the flat faces. Thereby, based on the measurement of the varying distance to the reference pattern, the position and orientation of straight lines representing each of the at least two flat surfaces may be determined, and on the basis thereof, the position or positions of one or more intersection points between such straight lines may be determined. The position of such intersection points may be compared to the ideal or theoretic position of the intersection points. Thereby, mutual misalignment of adjacent sand mould parts may be detected very accurately. Furthermore, among other parameters, the width of a possible gap between adjacent sand mould parts, mould expansion and mould dimensions may be detected by this arrangement.
In an embodiment, each of said at least two flat faces forms an oblique angle with the longitudinal direction of the moulding chamber. Thereby, the accuracy of the detected parameters may be improved, as the flat surfaces of the reference pattern may be better released from the reference pattern block and may therefore be formed more accurately in the sand mould part.
In an embodiment, the oblique angle between two flat faces measured externally of the reference pattern block is in the range from 95 to 175 degrees or in the range from 185 to 265 degrees. Thereby, the accuracy of the detected parameters may be further improved, as the flat surfaces of the reference pattern may be even better released from the reference pattern block and may therefore be formed more accurately in the sand mould part.
In an embodiment, the oblique angle between two flat surfaces measured externally of the sand mould part is in the range from 115 to 155 degrees or in the range from 205 to 245 degrees. Thereby, the accuracy of the detected parameters may be even further improved, as the flat surfaces of the reference pattern may be even better released from the reference pattern block and may therefore be formed more accurately in the sand mould part.
In an embodiment, the oblique angle between two flat surfaces measured externally of the sand mould part is in the range from 125 to 145 degrees or in the range from 215 to 235 degrees. Thereby, the accuracy of the detected parameters may be optimised, as the flat surfaces of the reference pattern may be even better released from the reference pattern block and may therefore be formed more accurately in the sand mould part.
In an embodiment, the non-contact detection system includes at least one electro-optical sensor unit.
In an embodiment, the non-contact detection system includes at least two electro-optical sensor units, and each electro-optical sensor unit is adapted to detect the position of a number of points located on a pattern face of a respective reference pattern on a compacted sand mould parts. Thereby, a higher accuracy may be obtained, because each electro-optical sensor unit may be dedicated to or focused on a specific reference pattern.
In an embodiment, the electro-optical sensor units are arranged in mutually fixed positions, preferably by means of a boom or frame. Thereby, an even higher accuracy may be obtained, because each electro-optical sensor unit may be accurately positioned in relation to the other electro-optical sensor units.
In an embodiment, the non-contact detection system includes at least one digital camera.
In an embodiment, the non-contact detection system includes at least one 3D scanner.
In an embodiment, the non-contact detection system includes a laser-based illumination system adapted to form an elongated light beam forming an illuminated line on the pattern face of the reference pattern. Thereby, by means of an electro-optical sensor unit, such as a camera, directed at the pattern face at a different angle than that of the elongated light beam, the position and distorted form of the illuminated line on the pattern face may be compared with a theoretic form. Thereby, the position and orientation of a known curve representing the pattern face may be determined or estimated, and on the basis thereof, the position or positions of one or more reference points for said known curve may be determined or estimated.
In an embodiment, the laser-based illumination system is adapted to form the elongated light beam by means of a prism.
In an embodiment, the non-contact detection system includes a laser-based illumination system adapted to sweep a light beam along a line on the pattern face of the reference pattern. Thereby, the above-mentioned advantages of an elongated light beam forming an illuminated line on the pattern face of the reference pattern may be obtained without a prism.
In an embodiment, the non-contact detection system includes a first laser-based illumination system adapted to form a first elongated light beam forming a first illuminated line on the pattern face of the reference pattern, wherein the non-contact detection system includes a second laser-based illumination system adapted to form a second elongated light beam forming a second illuminated line on the pattern face of the reference pattern, said first and second lines extending in the longitudinal direction of the sand mould part, and wherein the second elongated light beam forms an angle of preferably 90 degrees with the first elongated light beam. Thereby, by means of a single reference pattern block, the actual three-dimensional position of a point in a corner of a sand mould part may be determined.
In an embodiment, the non-contact detection system includes a non-contact distance measuring device.
In an embodiment, the non-contact detection system includes a non-contact distance measuring device in the form of a laser-based distance sensor. Thereby, precise measurements may be obtained in an economic way.
In an embodiment, the non-contact distance measuring device is arranged rotatably and thereby is adapted to perform distance measurements to a number of points distributed along a line on the pattern face of the reference pattern when the sand mould part is arranged stationarily. Thereby, measurements may be performed without a linear displacement between the non-contact distance measuring device and the pattern face of the reference pattern.
In an embodiment, a computer system is adapted to receive the detected positions of a number of points located on a pattern face of the reference pattern of the sand mould part, the computer system is adapted to perform curve fitting on the basis of said received detected positions and thereby estimate the respective position of a curve in a coordinate system, the curve representing the pattern face of the reference pattern seen in cross-section, and wherein the computer system is adapted to calculate the position or positions of one or more reference points related to the curve. Thereby, the position or positions of one or more reference points related to the curve may be automatically determined. The position of such reference points may be automatically compared to the ideal or theoretic position of the reference points.
In an embodiment, the non-contact distance measuring device is adapted to measure a varying distance to the reference patterns of the sand mould parts during a relative displacement in a displacement direction between the compacted sand mould parts and the non-contact distance measuring device, and said displacement direction corresponds to the longitudinal direction of the sand mould part.
In an embodiment, the non-contact distance measuring device is arranged to measure a distance in a direction at right angles to the displacement direction. Thereby, calculations in an associated computer system may be simplified.
In an embodiment, at least one of the reference pattern blocks is arranged to form a reference pattern in a corner of a sand mould part, said reference pattern includes a first set of at least two flat surfaces following one after the other in the longitudinal direction of the moulding chamber and being arranged at right angles to the chamber top wall, each flat surface of the first set is arranged at an oblique angle to another one of the flat surfaces of the first set, said reference pattern includes a second set of at least two flat surfaces following one after the other in the longitudinal direction of the moulding chamber and being arranged at right angles to the chamber side walls, each flat surface of the second set is arranged at an oblique angle to another one of the flat surfaces of the second set, a first non-contact distance measuring device is arranged to measure the varying distance to the reference pattern as a result of the at least two flat surfaces of the first set passing relatively the non-contact distance measuring device in succession during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device, and a second non-contact distance measuring device is arranged to measure the varying distance to the reference pattern as a result of the at least two flat surfaces of the second set passing relatively the non-contact distance measuring device in succession during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, by means of a single reference pattern block, the actual three-dimensional position of a point in a corner of a sand mould part may be determined.
In an embodiment, the first non-contact distance measuring device is arranged to measure a distance in a first measuring direction, and the second non-contact distance measuring device is arranged to measure a distance in a second measuring direction being different from the first measuring direction. Thereby data may be available for positioning in the three-dimensional space.
In a structurally particularly advantageous embodiment, the reference pattern block has the form of a fourth of an element combined from at least two truncated square pyramids fitted on top of each other, the top of a lower positioned truncated square pyramid matches the base of a higher positioned truncated square pyramid, and said element has been parted along its centreline and through the symmetry lines of adjacent lateral surfaces of the truncated square pyramids in order to form said fourth.
In an embodiment, all faces of the reference pattern block intended to contact sand mould parts are formed with a draft angle in relation to the longitudinal direction of the moulding chamber. Thereby, the accuracy of the detected parameters may be improved, as all faces of the reference pattern may be better released from the reference pattern block and therefore the flat surfaces of the reference pattern may be formed more accurately in the sand mould part.
In an embodiment, a computer system is adapted to receive a number of distance measurements from the non-contact distance measuring device during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device, the computer system is adapted to perform curve fitting on the basis of said received distance measurements and thereby estimate the respective positions of a number of straight lines in a coordinate system, each straight line representing a respective one of the at least two flat surfaces of the reference pattern seen in cross-section, and wherein the computer system is adapted to calculate the position or positions of one or more intersection points between such straight lines. Thereby, the position or positions of one or more intersection points between such straight lines may be automatically determined. The position of such intersection points may be automatically compared to the ideal or theoretic position of the intersection points.
In an embodiment, the computer system is adapted to perform curve fitting and thereby estimate the respective positions of the number of straight lines based additionally on measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, the respective positions of the number of straight lines may be estimated by curve fitting even if the speed of advancement in the conveying direction of the compacted sand mould parts is not constant.
In an embodiment, a position sensor is adapted to perform the measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device, and wherein the position sensor has the form of an absolute, non-contact position sensor working according to the magnetostrictive principle.
In a structurally particularly advantageous embodiment, a set including a number of non-contact distance measuring devices is mounted on a measuring boom at least partially surrounding the path of travel of the compacted sand mould parts, and the set includes at least a non-contact distance measuring device arranged to measure a distance in a first direction and a non-contact distance measuring device arranged to measure a distance in a second direction being different from the first direction.
In an embodiment, a conveyor is adapted to advance the compacted sand mould parts along the path of travel in order to achieve relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, said relative displacement necessary for the measurement of a distance by means of the non-contact distance measuring device may be achieved by means of a conveyor, which may anyway be necessary for transporting the compacted sand mould parts along the path of travel. Thereby, a separate device for displacing the non-contact distance measuring device may be avoided.
In an embodiment, the non-contact distance measuring device is arranged displaceably in order to achieve relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, said relative displacement necessary for the measurement of a distance by means of the non-contact distance measuring device may be achieved even if the compacted sand mould parts stand still and are not conveyed. Additionally, in the case of a sand moulding machine working according to the match plate technique, two sand mould parts may be positioned on top of each other to form a complete sand mould on a conveyor, and the non-contact distance measuring device may be displaced in the vertical direction in order to achieve said relative displacement. In this case, said relative displacement is in a direction, which is not a conveying direction of the sand mould parts.
In an embodiment, each of the chamber end walls is provided with a pattern plate having a pattern adapted to form a pattern in a sand mould part, and a conveyor is adapted to advance a number of compacted sand mould parts in aligned and mutually abutting configuration along a path of travel in a conveying direction corresponding to the longitudinal direction of the moulding chamber. Thereby, the sand moulding machine may work according to the vertical sand flaskless moulding technique such as the DISAMATIC (Registered Trademark).
In an embodiment, the non-contact distance measuring device is arranged stationarily, a position sensor is adapted to perform the measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device in the form of the position in the conveying direction of the compacted sand mould parts, and the position sensor is coupled to a so-called Automatic Mould Conveyor (AMC), a so-called Precision Mould Conveyor (PMC) or a so-called Synchronized Belt Conveyor (SBC).
In an embodiment, a set of non-contact distance measuring devices is arranged along the path of travel of the compacted sand mould parts, the set includes two non-contact distance measuring devices arranged to measure a distance in an at least substantially vertical direction and a distance in an at least substantially horizontal direction, respectively, to a reference pattern in an upper left corner of a sand mould part, two non-contact distance measuring devices arranged to measure a distance in an at least substantially vertical direction and a distance in an at least substantially horizontal direction, respectively, to a reference pattern in an upper right corner of a sand mould part, one non-contact distance measuring device arranged to measure a distance in an at least substantially horizontal direction to a reference pattern at or above a lower left corner of a sand mould part, and one non-contact distance measuring device arranged to measure a distance in an at least substantially horizontal direction to a reference pattern at or above a lower right corner of a sand mould part. Thereby, vertical, lateral and rotational mutual misalignment and the width of a possible gap between adjacent mould sections may be detected very accurately. Furthermore, among other parameters, the width of a possible gap between adjacent mould sections, mould expansion and mould dimensions may be detected by this arrangement. Nevertheless, by this arrangement a complicated arrangement of non-contact distance measuring devices beneath the path of travel of the compacted sand mould parts may be avoided.
In an embodiment, a further non-contact distance measuring device is arranged to measure a distance obliquely in an upward or downward direction to the reference pattern at or above a lower left corner of a sand mould part, and a further non-contact distance measuring device is arranged to measure a distance obliquely in an upward or downward direction to the reference pattern at or above a lower right corner of a sand mould part. Thereby, vertical, lateral and rotational mutual misalignment and the width of a possible gap between adjacent mould sections may be detected even more accurately. Nevertheless, also by this arrangement a complicated arrangement of non-contact distance measuring devices beneath the path of travel of the compacted sand mould parts may be avoided, because said further non-contact distance measuring devices may in oblique direction so to say see flat faces of the reference pattern facing in downwards or upwards direction.
In an embodiment, two moulding chambers are separated by means of a match plate, the sand moulding machine is adapted to simultaneously compress two sand mould parts in the respective two moulding chambers and subsequently remove the match plate and position said two sand mould parts on top of each other to form a complete sand mould, and the non-contact distance measuring device is arranged to measure the varying distance to the reference patterns of said two sand mould parts positioned on top of each other.
In an embodiment, the sand moulding machine is adapted to position said two sand mould parts on top of each other and subsequently press the upper one of said two sand mould parts out from its respective moulding chamber, and the non-contact distance measuring device is arranged to measure the varying distance to the reference patterns of said two sand mould parts subsequently to pressing the upper one of said two sand mould parts out from its respective moulding chamber, but before placing said two sand mould parts on a conveying surface of a conveyor. Thereby, the movement performed by the sand moulding machine of said two sand mould parts may be utilized for achieving the required relative displacement in a displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, a separate device for displacing the non-contact distance measuring device may be avoided.
In an embodiment, the sand moulding machine includes a frame positioning device for positioning a holding frame around said two sand mould parts positioned on top of each other and positioned on a conveying surface of a conveyor, and the non-contact distance measuring device is arranged to measure the varying distance to the reference patterns of said two sand mould parts at a position along the path of travel of the compacted sand mould parts before and/or after the frame positioning device. It may be of interest detecting whether the action of positioning a holding frame around said two sand mould parts positioned on top of each other may displace the sand mould parts mutually.
In an embodiment, the sand moulding machine includes a frame positioning device for positioning a holding frame around said two sand mould parts positioned on top of each other and positioned on a conveying surface of a conveyor, the non-contact distance measuring device is arranged to measure the varying distance to the reference patterns of said two sand mould parts at a position along the path of travel of the compacted sand mould parts at or after the frame positioning device, and the holding frame has an opening through which the non-contact distance measuring device is adapted to measure the varying distance to the reference patterns of said two sand mould parts. Thereby, it may be possible to perform distance measurement during or after positioning the holding frame around said two sand mould parts. If the distance measurement is performed during said positioning the holding frame, the non-contact distance measuring device may even be mounted on and displaced by the frame positioning device.
The present invention further relates to a foundry production line including a sand moulding machine as described above, wherein a melt pouring device is adapted for automatic positioning along the path of travel in the conveying direction, and wherein a computer system is adapted to control the position of the melt pouring device on the basis of calculated positions of at least two intersection points between straight lines associated with a number of sand mould parts positioned between the sand moulding machine and the melt pouring device. Thereby, the melt-pouring device may be accurately positioned in relation to the pouring opening in a sand mould formed by two adjacent sand mould parts, even if the individual dimensions of the sand mould parts positioned between the sand moulding machine and the melt-pouring device vary throughout the process.
In an embodiment, a set including a number of non-contact distance measuring devices is arranged adjacent the path of travel of the compacted sand mould parts just after the sand moulding machine. Thereby, mutual misalignment of adjacent mould sections and other parameters as mentioned above resulting from the sand moulding process may be detected.
In an embodiment, a set including a number of non-contact distance measuring devices is arranged adjacent the path of travel of the compacted sand mould parts just before a melt pouring device. Thereby, mutual misalignment of adjacent mould sections and other parameters as mentioned above resulting from the sand moulding process and resulting from the conveying process may be detected. By comparing parameters detected by a set of non-contact distance measuring devices arranged just after the sand moulding machine with parameters detected by a set of non-contact distance measuring devices arranged just before a melt-pouring device, the parameters related to the conveying process may be detected.
In an embodiment, a set including a number of non-contact distance measuring devices is arranged adjacent the path of travel of the compacted sand mould parts just after a melt pouring device. Thereby, mutual misalignment of adjacent mould sections and other parameters as mentioned above resulting from the sand moulding process, the conveying process and the melt pouring process may be detected. By comparing parameters detected by a set of non-contact distance measuring devices arranged just after a melt pouring device with parameters detected by a set of non-contact distance measuring devices arranged just after the sand moulding machine and with parameters detected by a set of non-contact distance measuring devices arranged just before the melt pouring device, the parameters related to the melt pouring process may be detected.
In an embodiment, a computer system is adapted to control a melt pouring device to stop the pouring of melt on the basis of calculated positions of at least two intersection points between straight lines, and wherein said at least two intersection points are associated with two respective sand mould parts positioned in mutually abutting configuration. Thereby, it may be avoided that faulty castings are produced for instance as a result of mismatch between sand mould parts.
The present invention further relates to a method of producing sand mould parts, whereby a moulding chamber during a filling operation is filled with sand, and whereby the sand is subsequently compacted, the moulding chamber being formed by a chamber top wall, a chamber bottom wall, two opposed chamber side walls and two opposed chamber end walls, whereby the moulding chamber is filled with sand through at least one sand filling opening provided in a chamber wall, whereby a mould or mould part is provided with a pattern by means of at least one of the chamber end walls being provided with a pattern plate having a pattern, and whereby sand is compacted inside the moulding chamber by displacing at least one of the chamber end walls in a longitudinal direction of the moulding chamber, whereby a reference pattern is formed in an external face of a sand mould part by means of at least one reference pattern block associated with and positioned in fixed relationship to at least one of the pattern plates, and whereby a position of a pattern face of the reference patterns of the sand mould parts is detected by means of a non-contact detection system arranged adjacent a path of travel of the compacted sand mould parts.
The method is characterised by that the at least one reference pattern block forms a corresponding reference pattern including a pattern face having a tangent varying in a longitudinal direction of the sand mould part corresponding to the longitudinal direction of the moulding chamber, by that the non-contact detection system detects the position of a number of different points distributed over the pattern face of the reference pattern in the longitudinal direction of the sand mould part, and by that the tangent in the longitudinal direction of the sand mould part is different between at least two of said points.
Thereby, the above described features may be obtained.
In an embodiment, the at least one reference pattern block forms a corresponding reference pattern including a pattern face having a tangent varying in a height direction of the sand mould part corresponding to a height direction of the moulding chamber, the non-contact detection system detects the position of a number of different points distributed over the pattern face of the reference pattern in the height direction of the sand mould parts, and by that the tangent in the height direction of the sand mould parts is different between at least two of said points. Thereby, the above described features may be obtained.
In an embodiment, the at least one reference pattern block forms a reference pattern including a first pattern face part having a first pattern tangent at a first position in the longitudinal direction of the sand mould part and a second pattern face part having a second pattern tangent at a second position in the longitudinal direction of the sand mould part, the second pattern tangent is different from the first pattern tangent, and the non-contact detection system detects the position of a number of different points distributed at least substantially evenly over both the first and the second pattern face part of the reference pattern in the longitudinal direction of the sand mould part. Thereby, the above described features may be obtained.
In an embodiment, the at least one reference pattern block forms a reference pattern including a third pattern face part having a third pattern tangent at a third position in a height direction of the sand mould part corresponding to a height direction of the moulding chamber and a fourth pattern face part having a fourth pattern tangent at a fourth position in the height direction of the sand mould part, whereby the fourth pattern tangent is different from the third pattern tangent, and whereby the non-contact detection system detects the position of a number of different points distributed at least substantially evenly over both the third and the fourth pattern face part of the reference pattern in the height direction of the sand mould part. Thereby, the above described features may be obtained.
In an embodiment, the at least one reference pattern block includes a spherically symmetric face. Thereby, the above described features may be obtained.
In an embodiment, the at least one reference pattern block forms a reference pattern including at least two flat surfaces following one after the other in the longitudinal direction of the moulding chamber, and whereby each flat surface is arranged at an oblique angle to another one of the flat surfaces. Thereby, the above described features may be obtained.
In an embodiment, each of said at least two flat faces forms an oblique angle with the longitudinal direction of the moulding chamber. Thereby, the above described features may be obtained.
In an embodiment, the oblique angle between two flat faces measured externally of the reference pattern block is in the range from 95 to 175 degrees or in the range from 185 to 265 degrees, preferably in the range from 115 to 155 degrees or in the range from 205 to 245 degrees, and most preferred in the range from 125 to 145 degrees or in the range from 215 to 235 degrees. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes at least one electro-optical sensor unit. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes at least two electro-optical sensor units, and whereby each electro-optical sensor unit detects the position of a number of points located on a pattern face of a respective reference pattern on a compacted sand mould parts. Thereby, the above described features may be obtained.
In an embodiment, the electro-optical sensor units are maintained in mutually fixed positions, preferably by means of a boom or frame. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes at least one digital camera. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes at least one 3D scanner. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes a laser-based illumination system which forms an elongated light beam forming an illuminated line on the pattern face of the reference pattern. Thereby, the above described features may be obtained.
In an embodiment, the laser-based illumination system forms the elongated light beam by means of a prism. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes a laser-based illumination system which sweeps a light beam along a line on the pattern face of the reference pattern. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes a first laser-based illumination system which forms a first elongated light beam forming a first illuminated line on the pattern face of the reference pattern, whereby the non-contact detection system includes a second laser-based illumination system which forms a second elongated light beam forming a second illuminated line on the pattern face of the reference pattern, said first and second lines extending in the longitudinal direction of the sand mould part, and whereby the second elongated light beam forms an angle of preferably 90 degrees with the first elongated light beam. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes a non-contact distance measuring device. Thereby, the above described features may be obtained.
In an embodiment, the non-contact detection system includes a non-contact distance measuring device in the form of a laser-based distance sensor. Thereby, the above described features may be obtained.
In an embodiment, the non-contact distance measuring device rotates and thereby performs distance measurements to a number of points distributed along a line on the pattern face of the reference pattern when the sand mould part is arranged stationarily. Thereby, the above described features may be obtained.
In an embodiment, a computer system receives the detected positions of a number of points located on a pattern face of the reference pattern of the sand mould part, whereby the computer system performs curve fitting on the basis of said received detected positions and thereby estimates the respective position of a curve in a coordinate system, the curve representing the pattern face of the reference pattern seen in cross-section, and whereby the computer system calculates the position or positions of one or more reference points related to the curve. Thereby, the above described features may be obtained.
In an embodiment, the non-contact distance measuring device measures a varying distance to the reference patterns of the sand mould parts during a relative displacement in a displacement direction between the compacted sand mould parts and the non-contact distance measuring device, and whereby said displacement direction corresponds to the longitudinal direction of the sand mould part. Thereby, the above described features may be obtained.
In an embodiment, the non-contact distance measuring device is measuring a distance in a direction at right angles to the displacement direction. Thereby, the above described features may be obtained.
In an embodiment, at least one of the reference pattern blocks forms a reference pattern in a corner of a sand mould part, whereby said reference pattern includes a first set of at least two flat surfaces following one after the other in the longitudinal direction of the moulding chamber and being arranged at right angles to the chamber top wall, each flat surface of the first set is arranged at an oblique angle to another one of the flat surfaces of the first set, whereby said reference pattern includes a second set of at least two flat surfaces following one after the other in the longitudinal direction of the moulding chamber and being arranged at right angles to the chamber side walls, each flat surface of the second set is arranged at an oblique angle to another one of the flat surfaces of the second set, whereby a first non-contact distance measuring device measures the varying distance to the reference pattern as a result of the at least two flat surfaces of the first set passing relatively the non-contact distance measuring device in succession during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device, and whereby a second non-contact distance measuring device measures the varying distance to the reference pattern as a result of the at least two flat surfaces of the second set passing relatively the non-contact distance measuring device in succession during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device Thereby, the above described features may be obtained.
In an embodiment, the first non-contact distance measuring device is measuring a distance in a first measuring direction, and whereby the second non-contact distance measuring device is measuring a distance in a second measuring direction being different from the first measuring direction. Thereby, the above described features may be obtained.
In an embodiment, the reference pattern block has the form of a fourth of an element combined from at least two truncated square pyramids fitted on top of each other, the top of a lower positioned truncated square pyramid matches the base of a higher positioned truncated square pyramid, and said element has been parted along its centreline and through the symmetry lines of adjacent lateral surfaces of the truncated square pyramids in order to form said fourth. Thereby, the above described features may be obtained.
In an embodiment, all faces of the reference pattern block contacting sand mould parts are formed with a draft angle in relation to the longitudinal direction of the moulding chamber direction. Thereby, the above described features may be obtained.
In an embodiment, a computer system receives a number of distance measurements from the non-contact distance measuring device during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device, whereby the computer system performs curve fitting on the basis of said received distance measurements and thereby estimates the respective positions of a number of straight lines in a coordinate system, each straight line representing a respective one of the at least two flat surfaces of the reference pattern seen in cross-section, and whereby the computer system calculates the position or positions of one or more intersection points between such straight lines. Thereby, the above described features may be obtained.
In an embodiment, the relative position between the compacted sand mould parts and the non-contact distance measuring device is measured during the relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device, and whereby the computer system performs curve fitting and thereby estimates the respective positions of the number of straight lines based additionally on said measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device. Thereby, the above described features may be obtained.
In an embodiment, a position sensor performs the measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device, and the position sensor has the form of an absolute, non-contact position sensor working according to the magnetostrictive principle. Thereby, the above described features may be obtained.
In an embodiment, a set including a number of non-contact distance measuring devices is mounted on a measuring boom at least partially surrounding the path of travel of the compacted sand mould parts, and wherein the set includes at least a non-contact distance measuring device measuring a distance in a first direction and a non-contact distance measuring device measuring a distance in a second direction being different from the first direction. Thereby, the above described features may be obtained.
In an embodiment, a conveyor advances the compacted sand mould parts along the path of travel in order to achieve relative displacement in the displacement direction between the compacted sand mould parts and a non-contact distance measuring device. Thereby, the above described features may be obtained.
In an embodiment, a non-contact distance measuring device is displaced along the path of travel in order to achieve relative displacement in the displacement direction between the compacted sand mould parts and the non-contact distance measuring device. Thereby, the above described features may be obtained.
In an embodiment, each of the chamber end walls is provided with a pattern plate having a pattern adapted to form a pattern in a sand mould part, and wherein a conveyor advances a number of compacted sand mould parts in aligned and mutually abutting configuration along the path of travel in a conveying direction corresponding to the longitudinal direction of the moulding chamber. Thereby, the above described features may be obtained.
In an embodiment, a non-contact distance measuring device is arranged stationarily, a position sensor performs the measurements of the relative position between the compacted sand mould parts and the non-contact distance measuring device in the form of the position in the conveying direction of the compacted sand mould parts, and the position sensor is coupled to a so-called Automatic Mould Conveyor (AMC), a so-called Precision Mould Conveyor (PMC) or a so-called Synchronized Belt Conveyor (SBC). Thereby, the above described features may be obtained.
In an embodiment, a set of non-contact distance measuring devices is arranged along the path of travel of the compacted sand mould parts, whereby the set includes two non-contact distance measuring devices measuring a distance in an at least substantially vertical direction and a distance in an at least substantially horizontal direction, respectively, to a reference pattern in an upper left corner of a sand mould part, two non-contact distance measuring devices measuring a distance in an at least substantially vertical direction and a distance in an at least substantially horizontal direction, respectively, to a reference pattern in an upper right corner of a sand mould part one non-contact distance measuring device measuring a distance in an at least substantially horizontal direction to a reference pattern at or above a lower left corner of a sand mould part, and one non-contact distance measuring device measuring a distance in an at least substantially horizontal direction to a reference pattern at or above a lower right corner of a sand mould part. Thereby, the above described features may be obtained.
In an embodiment, a further non-contact distance measuring device measures a distance in an upward direction to the reference pattern at or above a lower left corner of a sand mould part, and a further non-contact distance measuring device measures a distance in an upward direction to the reference pattern at or above a lower right corner of a sand mould part. Thereby, the above described features may be obtained.
In an embodiment, two moulding chambers separated by means of a match plate during the filling operation are filled with sand, the sand moulding machine simultaneously compresses two sand mould parts in the respective two moulding chambers and subsequently removes the match plate and positions said two sand mould parts on top of each other thereby forming a complete sand mould, and the non-contact distance measuring device measures the varying distance to the reference patterns of said two sand mould parts positioned on top of each other. Thereby, the above described features may be obtained.
In an embodiment, the sand moulding machine performs the following steps in succession:
Thereby, the above described features may be obtained.
In an embodiment, the sand moulding machine by means of a frame positioning device positions a holding frame around said two sand mould parts positioned on top of each other on a conveying surface of a conveyor, and whereby the non-contact distance measuring device measures the varying distance to the reference patterns of said two sand mould parts at a position along the path of travel of the compacted sand mould parts before and/or after positioning of the holding frame around said two sand mould parts. Thereby, the above described features may be obtained.
In an embodiment, the sand moulding machine by means of a frame positioning device positions a holding frame around said two sand mould parts positioned on top of each other on a conveying surface of a conveyor, whereby the non-contact distance measuring device measures the varying distance to the reference patterns of said two sand mould parts at a position along the path of travel of the compacted sand mould parts during or after positioning of the holding frame around said two sand mould parts, and whereby the non-contact distance measuring device measures the varying distance to said reference patterns through an opening formed in the holding frame. Thereby, the above described features may be obtained.
In an embodiment, a melt pouring device is automatically positioned along the path of travel in the conveying direction, and the computer system controls the position of the melt pouring device on the basis of a calculated position or positions of at least one reference point related to a curve associated with a sand mould part positioned between the sand moulding machine and the melt pouring device. Thereby, the above described features may be obtained.
In an embodiment, a set including a number of non-contact distance measuring devices is arranged adjacent the path of travel of the compacted sand mould parts at one or more of the following positions: just after the sand moulding machine, just before a melt pouring device and just after a melt pouring device. Thereby, the above described features may be obtained.
In an embodiment, whereby a computer system calculates positions of at least two reference points related to a curve, whereby said at least two reference points are associated with two respective sand mould parts positioned in mutually abutting configuration, and whereby the computer system controls a melt pouring device to stop the pouring of melt on the basis of calculated positions. Thereby, the above described features may be obtained.
The invention will now be explained in more detail below by means of examples of embodiments with reference to the very schematic drawing, in which
In the embodiment illustrated, the first chamber end wall 7 illustrated to the right in
The sand filling opening 9 of the moulding chamber 3 communicates with a sand feed system 18 including a sand container 19 also illustrated in
In the embodiment of the present invention illustrated in
In the embodiment illustrated in
Non-contact distance measuring devices are preferred as high accuracy may not be obtained with mechanical measuring probes due to the strength properties of the compressed mould.
It should be noted that in
In accordance with the embodiment illustrated in
The corner reference pattern block 24 used to form the corner reference pattern 28 is illustrated in
Furthermore, on each pattern plate 10, 11, two side reference pattern blocks 26, 27 are arranged to form corresponding side reference patterns 30, 31 at or above the lower corners of the sand mould part 2 as illustrated in
For all embodiments of the reference pattern blocks 24, 25, 26, 27 according to the invention, it should be considered that although it has been illustrated that the three flat faces L, M, N are directly connected to each other, adjacent flat faces L, M, N may alternatively be connected for instance by a rounding or another flat face.
In accordance with the embodiment illustrated in
Furthermore, the laser-based distance sensor L5 is arranged to measure the varying distance in horizontal direction to the side reference patterns 30, 31 formed in the right side of the string of compacted sand mould parts 2, seen in the conveying direction D of the compacted sand mould parts 2, as a result of the three flat surfaces l, m, n passing the measuring position 40. The laser-based distance sensor L6 is arranged to measure the varying distance in horizontal direction to the side reference patterns 30, 31 formed in the left side of the string of compacted sand mould parts 2, seen in the conveying direction D of the compacted sand mould parts 2, as a result of the three flat surfaces l, m, n passing the measuring position 40.
Although in the illustrated embodiment, the upper reference pattern blocks 24, 25 have been described as corner reference pattern blocks 24, 25 as the one illustrated in
Suitable non-contact distance measuring devices are available from the company SICK AG, Germany, in the form of short range distance sensors utilizing laser technology. Other suitable non-contact distance measuring devices based on other measuring technologies may also be employed according to the invention.
It is preferred that each of the three flat surfaces l, m, n of the reference patterns 28, 29, 30, 31 forms an oblique angle with the conveying direction. Thereby, the accuracy of the detected parameters may be improved, as the flat surfaces of the reference pattern may be better released from the reference pattern block and may therefore be formed more accurately in the sand mould part. In addition, the reference pattern block may be less worn during use which may also mean better accuracy in the long run. Furthermore, when using a laser-based distance sensor to measure the varying distance to the reference patterns, the distance measurements may be more precise, when the distance is gradually increasing or gradually decreasing as opposed to being constant. Although the applicant does not want to be bound by the following explanations, it is believed that the reason may have to do with the fact that the laser beam has a certain diameter, such as approximately 1 millimetre, and that the surface of the reference pattern has a certain grainy structure formed by sand grains. Furthermore, it may have to do with internal tolerances of the laser-based distance sensor.
It may be preferred that all faces of the reference pattern blocks intended to contact sand mould parts 2 are formed with a draft angle in relation to the longitudinal direction of the moulding chamber 3 in order to better release the reference pattern blocks from the sand mould parts 2.
In an embodiment, the oblique angle between two flat surfaces measured externally of the sand mould part is in the range from 95 to 175 degrees or in the range from 185 to 265 degrees, preferably in the range from 115 to 155 degrees or in the range from 205 to 245 degrees, and most preferred in the range from 125 to 145 degrees or in the range from 215 to 235 degrees. Thereby, according to experiments, the accuracy of the detected parameters may be even further improved. In the embodiment illustrated in
It is preferred that the non-contact distance measuring devices 39 are arranged to measure a distance in a direction at right angles to the conveying direction D. For instance, the laser-based distance sensor L1 could be arranged to measure a distance in horizontal direction, but at an oblique angle to the conveying direction D, and the measured distance could, for instance in a computer programme, be projected onto a direction at right angles to the conveying direction D. However, this would complicate the calculations in order to detect for instance misalignment of sand mould parts.
Likewise, it is preferred that the non-contact distance measuring devices 39 are arranged to measure a distance in an at least substantially horizontal direction or a distance in an at least substantially vertical direction. It is most practical to calculate and represent distances in a coordinate system having axes corresponding to the faces 32, 34, 35 of the sand mould parts 2 arranged on the conveyor 16. Although distances measured in other directions may be projected onto such axes, this may complicate calculations.
As illustrated in
Comparing the corner reference pattern block 24 illustrated in
It may be preferred to position the side faces 53 of the corner reference pattern blocks 24, 25 at a small distance, for instance 1/10 or ½ millimetre, from the adjacent chamber top wall 4 and the adjacent chamber side walls 6, respectively, in order to minimize wear. Likewise, it may be preferred to position the side faces 52 of the side reference pattern blocks 26, 27 at a small distance, for instance 1/10 or ½ millimetre, from the adjacent chamber side walls 6 in order to minimize wear. As seen in
According to the present invention, the computer system 23 illustrated in
Although in the illustrated embodiments, each reference pattern block 24, 25, 26, 27 includes at least one set of three flat faces (L, M, N) following one after the other in the conveying direction D, it should be understood that a set of two flat faces (may be enough, for instance if only sand mould misalignment should be detected. The determination of one intersection point A for each one of two abutting sand mould parts will be sufficient. On the other hand, if for instance a measure for local compaction of the sand mould part 2 should be determined, at least one set of three flat faces (L, M, N) following one after the other in the conveying direction D is necessary. This will be understood more clearly by the explanation further below.
Having performed the curve fitting operations and calculations necessary to estimate or position the straight lines in the coordinate system, the computer system 23 has calculated the correct position of the intersection point A1 between the straight lines representing the flat surfaces l1, m1, m1 and the correct position of the intersection point B1 between the straight lines representing the flat surfaces m1, n1 in the coordinate system illustrated in
Provided that the sand mould part 2 passes the measuring position 40 with a constant velocity, the straight lines representing the flat surfaces may be correctly positioned in a coordinate system by the computer system by adapting the slopes of the straight lines to the known slopes of the corresponding flat surfaces of the reference pattern. Theoretically, the slopes of the corresponding flat surfaces of the reference pattern correspond to the slopes of the corresponding faces of reference pattern block. However, by using this procedure, inaccuracies may occur; for instance the velocity of the sand mould parts 2 may vary slightly, although assumed constant. On the other hand, it may often be preferred that the sand mould parts 2 do not pass the measuring position 40 with a constant velocity. On the contrary, the sand mould parts 2 may for instance accelerate as they are expelled from the moulding chamber 3.
Therefore, it is preferred that the computer system 23 is adapted to, by means of curve fitting, estimate the respective positions of the straight lines based additionally on measurements of the position in the conveying direction D of the compacted sand mould parts 2 during the advancement in the conveying direction of the compacted sand mould parts 2. Thereby, a number of points may be plotted in a coordinate system based on pairs of corresponding measured position in the conveying direction D and measured distance to a reference pattern. By curve fitting, a straight line may be estimated on the basis of these points.
The measurements of the position in the conveying direction D of the compacted sand mould parts 2 may be performed by means of a position sensor 55 coupled to the conveyor 16. The conveyor 16 may have the form of a so-called Automatic Mould Conveyor (AMC) which conveys the compacted sand mould parts 2 by means of pneumatically operated longitudinally extending gripping elements 54 (also called thrust bars) arranged on either side of the string of the aligned and mutually abutting compacted sand mould parts 2 as illustrated in
The position sensor 55 may preferably be an absolute, non-contact position sensor working according to the magnetostrictive principle. Suitable position sensors of this type are marketed by the company MTS (registered trademark) under the trade name Temposonics (registered trademark). Other suitable position sensors may also be employed according to the invention. As illustrated in
In
Alternatively, the position sensor 55 may be a laser-based distance sensor measuring the distance to an external end face 35 of the lastly expelled sand mould part 2.
When the correct positions of the respective intersection points A, B for the different reference patterns 28, 29, 30, 31 have been determined by the computer system 23, a number of important variables may be calculated on the basis thereof. For instance, by comparing the respective positions along the y axis as indicated in
Furthermore, by calculating the distance along the x axis as indicated in
Furthermore, by calculating the distance along the x axis as indicated in
In the embodiment illustrated in
However, as inaccuracies in the sand mould part alignment as well as in other parameters may also result from the casting process itself, that is during the melt pouring process, it may furthermore be advantageous arranging the boom 41 or an additional boom 41 after or just after, and possibly relatively near or next to, the melt pouring device 22. Thereby, said inaccuracies may be taken into consideration immediately. Although melt may have been poured into a mould cavity, the detection of a faulty casting at this stage may be advantageous in that the method of producing sand mould parts may be corrected immediately, for instance by adjusting the pattern plates 10, 11. Furthermore, a faulty casting may in this way be identified and be separated out at an earlier stage before it would otherwise be mixed up with acceptable castings, which would lead to larger effort needed for locating the faulty casting.
Naturally, it may furthermore be advantageous arranging the boom 41 or an additional boom 41 just after, and possibly relatively near or next to, the sand moulding machine 1 in order to be able to take inaccuracies into consideration as early as possible.
In any way, it may be very advantageous to accurately detect any inaccuracies at or before the melt pouring device 22. If such inaccuracies are not detected according to the invention, these may not be detected before the castings have cooled down and are removed from the sand moulds. As there may be a string of for instance 300 or more sand moulds located downstream, that is after, the melt pouring device 22, it could take a long time before any inaccuracies would be detected by inspection of the cooled down castings at the end of such string. Therefore, in that case, more than 300 castings would have to be scrapped if there were only one casting in each mould. Often patterns for sand moulds with several casting cavities are used; meaning for instance a pattern with four cavities would result in 1200 defective castings having to be scrapped.
In an embodiment, the foundry production line 21 illustrated in
It should be mentioned that although in the above, it has been mentioned that the foundry production line 21 illustrated in
As illustrated in
As explained above, in the embodiment illustrated in
In an embodiment, the sand moulding machine 75 includes a not shown frame positioning device for positioning a not shown holding frame, a so called jacket, around said two sand mould parts 76, 77 positioned on top of each other on a conveying surface of the conveyor 74. The positioning of said holding frame around said two sand mould parts 76, 77 is well-known to the person skilled in the art and is done in order to maintain the two sand mould parts 76, 77 in correct mutual position during casting. The measuring boom 80 with the non-contact distance measuring devices 39 is arranged to measure the varying distance to the reference patterns 81 of said two sand mould parts 76, 77 at a position along the path of travel 17 of the compacted sand mould parts 76, 77 before and/or after the frame positioning device. It may be of interest detecting whether the action of positioning a holding frame around said two sand mould parts positioned on top of each other may displace the sand mould parts mutually. In a slightly alternative embodiment, the holding frame has an opening through which the non-contact distance measuring device 39 is adapted to measure the varying distance to the reference patterns 81 of said two sand mould parts 76, 77. Thereby, it may be possible to perform distance measurement during or after positioning the holding frame around said two sand mould parts. If the distance measurement is performed during said positioning of the holding frame, the non-contact distance measuring device may even be mounted on and displaced by the frame positioning device.
Although in the illustrated embodiments, the non-contact distance measuring devices 39 are arranged on a measuring boom 41, 80, the arrangement of the non-contact distance measuring devices 39 may be in any suitable way, for instance each non-contact distance measuring device 39 may be arranged on a separate holding pole.
In an embodiment, a computer system 23 is adapted to control a melt pouring device 22 to stop the pouring of melt on the basis of calculated positions of at least two intersection points A, B between straight lines, and wherein said at least two intersection points A, B are associated with two respective sand mould parts 2, 76, 77 positioned in mutually abutting configuration. Thereby, it may be avoided that faulty castings are produced for instance as a result of mismatch between sand mould parts.
The position of such reference points may be compared to the ideal or theoretic position of the reference points. Thereby, mutual misalignment of adjacent sand mould parts may be detected very accurately. Furthermore, among other parameters, the width of a possible gap between adjacent sand mould parts, mould expansion and mould dimensions may be detected by this arrangement. It may thereby be assessed whether the actual situation is acceptable or not. The ideal or theoretic position of the reference points may depend on the parameter that is to be assessed and may be determined by calculations based on theory or empirically. For instance, if the parameter to be assessed is mutual misalignment of adjacent sand mould parts, and the known curve corresponding to the pattern face is a circle, then the theoretic and ideal position of the reference point, the centre of the circle, of either sand mould part is the same position in a coordinate system, i.e. the centres of the two circles coincide.
As in the embodiment illustrated in
Although in the embodiment illustrated in
In the embodiment illustrated in
Furthermore, in the embodiment illustrated in
Furthermore, in the embodiment illustrated in
In the embodiment illustrated in
Furthermore, in the embodiment illustrated in
Furthermore, in the embodiment illustrated in
Preferably, in the respective embodiments illustrated in
Preferably, in the respective embodiments illustrated in
It should be noted that according to the present invention, a non-contact detection system 39 is any system that is able to detect the position of a number of different points distributed over the pattern face of the reference pattern without direct mechanical contact between the non-contact detection system and the pattern face. A non-contact detection system could for instance be a 3D scanner.
According to the present invention, the non-contact detection system 39 may include an electro-optical sensor unit, such as for instance a digital camera. Information delivered by electro-optical sensors are essentially of two types: either images or radiation levels (flux). Furthermore, the non-contact detection system 39 may include video, laser, radar, ultrasonic or infrared camera or the like.
A 3D scanner is an imaging device that collects distance point measurements from a real-world object and translates them into a virtual 3D object. Many different technologies can be used to build 3D-scanning devices; each technology comes with its own limitations, advantages and costs. Optical 3D scanners use photographic, stereoscopic cameras, lasers or structured or modulated light. Optical scanning often requires many angles or sweeps. Laser-based methods use a low-power, eye-safe pulsing laser working in conjunction with a camera. The laser illuminates a target, and associated software calculates the time it takes for the laser to reflect back from the target to yield a 3D image of the scanned item. Non-laser light-based scanners use either light that is structured into a pattern or a constantly modulated light and then record the formation the scanned object makes.
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/IB2015/054235 | 6/4/2015 | WO | 00 |
