Patent Application
20250187131
The present invention relates to a method for grinding of a workpiece with a grinding tool, wherein an axis of rotation of the grinding tool is oriented perpendicular to a feed plane of the grinding tool, wherein the workpiece is formed in particular by a temporary workpiece comprising a multiplicity of bandsaw blades that are parallel to one another.
Workpieces such as bandsaw blades are of great economic importance in a variety of machining methods, and are used extensively, particularly in the skilled trades, for the cutting, severing or dismantling of building elements, as well as in fire brigade rescue operations. Band saw blades are also used in industry, especially in cutting of metals, plastics or wood, as well as in the food industry, particularly for frozen fish or meat products. Accordingly, high demands are placed on the precision of the tooth geometries. In general, high-quality demands are placed on workpieces produced using grinding methods.
Band saw blades as possible workpieces generally exhibit great variability in terms of their tooth width and geometry. They are usually manufactured from a blank by unwinding a metal strip from a coil and, if necessary, turning and straightening it. The said metal strip is then ground to produce the teeth. It is also common to arrange a plurality of metal strips next to each other for simultaneous grinding so as to produce the teeth. If necessary, the bandsaw blades are then cut to the desired length, or the finished bandsaw blade is turned and wound up once again to form a bandsaw blade coil. The unwinding of the blank from the coil, together with the other subsequent work steps, are usually synchronised, at least to the extent of the work steps with which a bandsaw blade that is to be produced is continuously machined. Buffer sections between the individual machining stations may have to be planned in, if the cycle time is not constant throughout the entire production line.
From the prior art, there are methods of known art for the grinding of workpieces that machine the workpiece in a deep grinding method, a creep feed grinding method, or a plunge grinding method. In the course of a deep grinding or a creep feed grinding method, the grinding tool is brought on one occasion to the total vertical engagement setting external to the workpiece, and this is removed from the workpiece in a single horizontal feed cycle. In the plunge grinding method, the grinding tool is moved vertically into the workpiece to a final dimension that defines the total vertical engagement setting and is then lifted vertically out of the machined workpiece.
A disadvantage of the said prior art is the very slow feed rate in the course of the deep grinding method or creep feed grinding method. This is due to the very high grinding tool engagement in the workpiece, which leads to a very high heat input and, in extreme cases, to structural changes in the workpiece, and thus a potential deterioration in the material quality. Increased cycle times are therefore required. In the plunge grinding method, the width of the workpiece at right-angles to the feed direction is limited, by virtue of the fixed diameter of the grinding tool. The workpieces produced using the grinding method also have different dimensions as a result of the cross-sectional shape of the grinding tool.
The present invention is therefore based on the object of specifying an efficient and cost-effective method for grinding of a workpiece with the shortest possible cycle times.
This object is achieved by a method for grinding of a workpiece with a grinding tool, wherein an axis of rotation of the grinding tool is oriented perpendicular to a feed plane of the grinding tool, comprising the following steps:
The grinding tool is advantageously rotationally symmetrical and is designed such that it can be used for profile grinding or generating grinding. The first and second entry regions, as well as the first and second exit regions, are preferably defined as those regions in which the grinding tool and the workpiece, initially or finally respectively, are in contact with each other, before or after the two are moved apart from each other. Advantageously, both the grinding tool and the workpiece are mounted within a grinding machine such that they can move. The movement, contact, and traversing of the grinding tool takes place along at least two linear axes of the grinding machine, whereby the grinding tool is moved by interpolation along these linear axes.
With the inventive method for the grinding of the workpiece, the removal volume is divided into two steps of the method by a division of the grinding process, whereby a high traverse velocity and thus short cycle times and an efficient workpiece output from the grinding machine are achieved. In addition, the first to third velocities in accordance with the invention are adjusted to the respective engagement between the grinding tool and the workpiece, such that the load on these components is as uniform as possible and any damage, in particular that caused by load peaks, is therefore advantageously avoided.
The contour is advantageously selected such that there is a uniform material removal rate over the entire grinding cycle in accordance with the steps b) to g). Between the steps d) and e), the feed rate of the grinding tool is decelerated from the second velocity to 0 and is then accelerated to the third velocity before the grinding tool establishes contact with the workpiece for a second time. The horizontal directional components of the second velocity and third velocity are opposed to each other. In particular, the grinding tool rotates continuously at a constant peripheral velocity.
The machining region extends along an outer form of the workpiece, and advantageously extends the latter in all directions of propagation by a maximum of 25 mm, preferably by a maximum of 20 mm, particularly preferably by a maximum of 15 mm. The movement of the grinding tool into the machining region is achieved as soon as at least one part of the grinding tool lies within the machining region.
In an advantageous form of embodiment of the invention, the grinding tool moves at the third velocity in a total vertical engagement setting. The total vertical engagement setting is preferably 1 mm to 10 mm. Accordingly, the workpiece is machined to the final dimension by the movement of the grinding tool at the third velocity. A further machining step on the new surface created by the grinding tool at the third velocity is advantageously omitted, which further reduces the cycle time.
In an advantageous configuration of the invention, provision is made for the first entry region to be oriented such that it is vertically offset relative to the first exit region in the feed plane, whereby the first entry region and the first exit region are vertically offset relative to one another by less than or equal to the total vertical engagement setting. The first entry region and the first exit region are advantageously offset vertically relative to one another, such that the first entry region is positioned closer to the grinding tool than the first exit region. In a particularly advantageous form of embodiment, the grinding tool achieves the total vertical engagement setting in the course of the first extraction from the workpiece, so that the grinding tool undergoes a horizontal change of direction immediately after the extraction, and establishes contact with the second entry region in the total vertical engagement setting along the horizontal direction of traverse, traverses through the workpiece, and is extracted from the second exit region.
Furthermore, in an advantageous development of the invention, the first entry region extends over an essentially first vertical outer surface of the workpiece and an essentially horizontal outer surface of the workpiece adjacent to the first vertical outer surface, whereby the first exit region extends over an essentially second vertical outer surface of the workpiece, whereby the second vertical outer surface is opposed to the first vertical outer surface. Advantageously, the first entry region in the feed plane thus has an L-shaped cross-section by virtue of the vertical and horizontal sections, whereas the first exit region in particular has an I-shaped cross-section, since exit takes place on the vertical surface located opposite to the vertical entry surface. The first entry region advantageously extends from a corner point formed by the first vertical outer surface and the horizontal outer surface along the first vertical outer surface and the horizontal outer surface, by a maximum of 6 mm in each case, preferably by a maximum of 4 mm in each case, particularly preferably by a maximum of 2 mm in each case. The horizontal outer surface is defined as the surface closest to the grinding tool. The first vertical and second outer surfaces are in each case oriented parallel to the axis of rotation and at right-angles to the horizontal direction of traverse, and are advantageously connected indirectly by the horizontal outer surface. The horizontal outer surface is advantageously oriented parallel to the horizontal direction of traverse.
A maximum first traverse is formed, in which the first entry region is positioned vertically at the height of the horizontal outer surface, and the first exit region is positioned vertically at the height of the total vertical engagement setting. Any intermediate vertical positioning of the first entry region and the first exit region is also possible, as long as the first entry region is positioned closer to the horizontal outer surface than the first exit region. Such preferential positioning of the first entry region allows the machining region to be significantly reduced, and the grinding tool can thus be moved close to the workpiece without inadvertently establishing contact with it.
In a further configuration of the invention, provision is made for the first exit region to extend over the essentially second vertical outer surface, and for the second exit region to extend over the essentially first vertical outer surface, whereby a greater vertical offset is formed between the first entry region and the second exit region than between the first exit region and the second entry region. Accordingly, the first traverse of the grinding tool has a horizontal directional component that is opposed to the second traverse of the grinding tool. Since, in accordance with the invention, the second traverse takes place along the horizontal direction of traverse, the second entry region and the second exit region are advantageously designed to be congruent, and are arranged to be offset parallel to one another along the horizontal direction of traverse.
In a development of the invention, provision is made for the predefined contour to have an essentially linear, parabolic, logarithmic, exponential, or wave-like shape, or a superposition of at least two of the aforementioned shapes. Advantageously, the predefined contour is selected such that the material removal rate of the workpiece is as uniform as possible, and thus the loads on the grinding tool and workpiece are also as uniform as possible.
In an advantageous development of the invention, the predefined contour and the horizontal direction of traverse subtend an angle φ of 1° to 45°, preferably of 15° to 30°, particularly preferably of 20° to 25°. If the predefined contour does not have a linear shape, a linear average of the predefined contour is used to define the angle φ. Another possibility for the definition of the angle φ is the generation of a straight line through the point of contact and the point of extraction between the grinding tool and the workpiece. The angle φ depends on, amongst other items, a workpiece width defined at right-angles to the axis of rotation, which in particular is between 10 mm and 60 mm in size.
In an advantageous form of embodiment of the invention, the first entry region ends vertically above the first exit region, so that the grinding tool always experiences a vertical directional component in the course of a first traverse, whereby an angle φ between the horizontal direction of traverse and the contour is always greater than 0.
In an advantageous configuration of the invention, provision is made for the axis of rotation to lie behind or within the first entry region in the feed plane in the course of the contact of the first entry region with the grinding tool along the horizontal direction of traverse.
Furthermore, in an advantageous development of the invention, in the course of the first extraction, and/or the contact of the second entry region along the horizontal direction of traverse, the axis of rotation lies in front of, or within, the second entry region in the feed plane. Depending on the type and the requirements of the workpiece, the direction of rotation of the grinding tool about the axis of rotation is defined so as, in particular, to achieve the flattest possible surfaces, or the shortest possible machining time. The direction of rotation of the grinding tool is preferably defined as in the opposite direction to the third velocity.
In an advantageous configuration of the invention, provision is made for the first velocity to be higher than the second and third velocities respectively, whereby the second and third velocity differ from each other, whereby the second and third velocities in each case are constant in the course of an engagement of the grinding tool with the workpiece. While the grinding tool is moved at the first velocity, it is not in contact with the workpiece, as a result of which there is no risk of damage to the workpiece and/or the grinding tool. The second and third velocity are preferably selected such that the shortest possible cycle time is generated, but such that there is no alteration in the structure of a metallic workpiece in particular, and no damage to the workpiece and/or the grinding tool. In a particularly advantageous manner, the second and third velocities are furthermore selected such that the rate of material removal from the workpiece is as uniform as possible.
Furthermore, in an advantageous form of embodiment, the workpiece is formed by a temporary workpiece comprising a plurality of bandsaw blades that are parallel to one another, whereby a plurality of teeth of the temporary workpiece are ground simultaneously by the grinding tool. In an advantageous manner, a plurality of individual workpieces, namely the individual bandsaw blades, are thus combined so as to form a temporary workpiece and are machined simultaneously. The greater the number of bandsaw blades forming a temporary workpiece, the more the cycle time for a single bandsaw blade is reduced, which significantly increases the output of the grinding machine and thus greatly increases the cost efficiency. In their longitudinal alignment the bandsaw blades forming the temporary workpiece are arranged parallel to the axis of rotation of the grinding tool.
In a development of the invention, provision is made for the workpiece to be held down and clamped before and/or during the movement of the grinding tool. Parallelisation of these operations further reduces the cycle time for the machining of the workpiece. Since the workpiece and the grinding tool do not engage with each other in the course of any of these operations, they can be carried out independently of each other, provided that the build space of a grinding machine permits this.
In a preferred form of embodiment of the invention, provision is made for the workpiece to be displaced parallel to the axis of rotation after the second extraction, and at least the steps b) to f) are repeated. A development of the machining process of the workpiece advantageously begins with the pressing down and clamping of the workpiece. This is followed by steps a) to f) in accordance with the invention, after which the workpiece is ground, whereby when grinding bandsaw blades of identical build, which are forming a temporary workpiece, either tooth backs and/or tooth faces are generated by steps a) to f). The workpiece is then displaced parallel to the axis of rotation and at least steps b) to f) are repeated, wherein when grinding bandsaw blades of identical construction forming the temporary workpiece, either tooth backs and/or tooth faces are generated by repeating at least steps b) to f), depending on which were not generated in the course of the first grinding operation, The aforementioned steps of grinding and shifting can preferably be repeated at least once more before the workpiece is released from its clamped state, which further shortens the cycle times.
In a preferred development of the method, the workpiece, after the second extraction, is released from its clamped state, is displaced and clamped once again, and at least steps b) to f) are repeated. Here too, the workpiece is displaced parallel to the axis of rotation of the grinding tool, whereby a machining cycle is generated within the method. The steps of releasing, displacing, and clamping are particularly necessary for workpieces that are machined a number of times at different positions using the inventive method. The clamping and releasing are advantageously performed by at least one clamping unit arranged on the grinding machine. The displacement is either also carried out by the clamping units, whereby the clamping units are guided parallel to the axis of rotation by way of a linear guide on the grinding machine, or the workpiece is displaced parallel to the axis of rotation by a further offset unit, and is then re-clamped by means of the clamping units so as to engage the grinding tool in the workpiece.
The invention is described by way of example in a plurality of preferred forms of embodiment with reference to illustrations, whereby further advantageous details are shown in the figures in the illustrations.
Here functionally identical parts are labelled with the same reference symbols.
The figures in the illustrations show in detail:
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2023 134 183.9 | Dec 2023 | DE | national |
