Patent Application
20050247092
The use of open die forging to form and/or draw a metallic workpiece between upper and lower dies of a forging press is known, particularly with respect to forging operations of large size workpieces (e.g., for power generation machinery, crank shafts). One important aspect with respect to the quality of a forged product, is a uniform and thorough forging of the core of a workpiece in order to eliminate cavities and other inclusions in the workpiece that impair quality. To achieve a uniform consolidation of the center line, the center line being the direction in which the workpiece is moved forward and backward wherein the center of mass of the workpiece is considered the center line of a workpiece being forged. One process known as “cogging” is used to convert coarse-grained, cast ingot into fine-grained, wrought billet or in other words break down the coarse cast structure and consolidate internal defects in the work piece. In many forging shops, because of various constraints imposed by a large-scale forging operation of red-hot workpieces, forging processes are controlled by a human operator. In such processes, the operator controls center line consolidation by visual inspection to determine consolidation areas of the last forging pass, which appear as bright structures at the side of the workpiece. From experience, the operator then estimates the placement of the next cogging blows or “setup points” to improve centerline consolidation.
Operator-related variations in process control and also variations of the achieved consolidation quality can result, however, which can lead to a high rejection rate in terms of quality management and economy. Moreover, if a workpiece is not inspected for the absence of such defects until it has first been drawn or deformed, cavities and other inclusions originating in the casting process could remain after the forging process. These defects typically require additional forging and/or discarding of the workpiece that can result in the loss of work time, material, and/or energy costs.
The foregoing illustrates limitations known to exist in present forging control apparatus and methods. Thus it is apparent that it would be advantageous to provide an alternative directed to overcoming one or more of the limitations set forth above. Accordingly, an alternative forging control apparatus and methods are described including the features more fully disclosed hereinafter.
According to the present invention, a method and apparatus for optimizing the forging of a workpiece that is moved along a longitudinal axis of a forging press. The method includes detecting the relative positions of the first and second ends of the workpiece along the longitudinal axis and calculating a length of the workpiece therebetween.
The foregoing and other aspects will become apparent from the following detailed description of the invention when considered in conjunction with accompanying drawing figures.
The invention is best understood by reference to the accompanying drawings in which like reference numbers refer to like parts. It is emphasized that, according to common practice, the various dimensions of the component parts of the apparatus as shown in the drawings are not to scale and have been enlarged for clarity. Also, the directional designations “left” or “right” are not to be construed as limited to any specific orientation but, rather, are for reference purposes as they pertain to the views as shown in the drawing figures.
According to the apparatus and method of the present invention as described herein, a contactless method and apparatus are provided for controlling a forging operation using a contactless laser profile measurement. The method and apparatus are particularly useful in controlling center line consolidation of a workpiece during a cogging operation.
Briefly, the method of the present invention measures the real-time length of a workpiece between forging passes. This measurement is necessary for an accurate recording of the center line consolidation areas. This measurement is also necessary because the length can not be derived from theoretical and/or previous data base measurements due to the inhomogeneous quality of the workpiece such as chemical and physical properties. Therefore, elongation after each stroke can not be predicted. This measurement is achieved by a two-dimensional laser scanner, which measures the transverse profile of the workpiece's end when it crosses a measurement plane. The method also includes calculating the current degree of center line consolidation and the bite shift and/or setup point for a next forging pass. The position of the next forging pass is then marked in a process display along with all previous passes of the forging strokes to show the degree of center line consolidation. This is done by a computer program that displays the previous setup points along the workpiece together with the potential position of the next setup point in real time graphics. The program then either suggests to or automatically selects for a forge operator the next setup point, which takes into account all general and special boundary conditions of the forging shop.
Referring to the figures in which like reference numerals indicate like structures throughout,
The system 10 of
A laser scanning head 14, supporting equipment 15, and software for effecting the contactless measurement of a workpiece and consequential computation of its dimension and/or shape are commercially available from FERROTRON Technologies, GmbH, Industrial Measurement Technology, Moers, Germany, a division of Minerals Technologies Inc., as the LACAM (Laser Camera) imaging system, Model E113. Such contactless measuring equipment includes a Laser Line Scanner that uses two main components:
The present inventor with others have described previously in their published International Patent Application WO/01/38900A1, the disclosure of which is incorporated herein by reference, a LACAM laser profile measuring system useful in the non-contact measurement of refractory linings in metallurgical vessels. This technology is based on rapidly scanning the deflection of a pulsed laser beam on a refractory surface to be measured. To carry out the measurement, a three-dimensional grid of measurement values is recorded. The periodic deflection of the laser that is required for this purpose is accomplished in both vertical and horizontal directions by means of a mirror that rotates, respectively, around both the horizontal and vertical axes.
In the paper titled “Laser Measurements on Large Open Die Forging (LACAM-FORGE),” the disclosure of which is incorporated herein by reference, the present inventor with others have also described the use of a LACAM profile measuring system for three-dimensional measuring of the hot workpiece after the forging process and a profile of the workpiece is obtained. The data derived from these measurements are used to determine important geometrical information of the workpiece, i.e. length, width, height, flatness, etc. Additionally, described therein, measurement of a workpiece is performed using a LACAM measuring head like that described in WO/01/38900A1, except that the scanning head is mounted at a fixed position to rotate in at least one of a vertical or horizontal direction, thereby providing a line-scan as produced by the Laser Line Scanner.
The LACAM scanning head 14 shown in
By longitudinally moving the end of the workpiece perpendicular to the measurement plane, profiles are obtained and combined to provide a three-dimensional profile as shown in
As a result, the current length of workpiece 30, which is increased during each single stroke, can be measured in real time during the forging operation under production conditions. As LACAM measuring systems and their operation for contactless measurement are described in detail in WO/01/38900 A1 and “Laser Measurements on Large Open Die Forging (LACAM-FORGE),” this measurement method will be discussed below with respect to the modifications needed to effect control for center line consolidation in a forging process.
The method of the present invention also includes calculating the current degree of center line consolidation by controlling the following parameters:
Additionally, the method and apparatus of the present invention effect centerline consolidation by calculating the bite shift for the next forging stroke according to the flow diagram of the measurement software system as shown in
Upon engaging the apparatus by triggering a start button of workstation 17 (1) the right edge 39 (reference edge) of the workpiece 30 is aligned with the right edge of the lower die 34 and/or the upper die 32 and the position is recorded. The measurement (100) begins now. The system is initialized by resetting the pass number and stroke number to zero (110).
The left edge of the workpiece 30 is passed through the line scanner measurement plane to determine where the inflection point of the left edge 38 of the workpiece 30 is located (130). From these measurements the length of the workpiece is obtained.
If the current pass number is zero the pass number is incremented by one, otherwise the system waits until the workpiece is turned on a longitudinal axis by an angle of 90 degrees (140) and the pass number is incremented by one (142).
After the first pass, elongation of the workpiece is calculated by dividing the current length of the workpiece by the length of previous pass (144). The positions of previous setup points are corrected based on the determined elongation (146) of the workpiece.
The bite shift optimization routine (200) is started resulting in a proposal for the location of the next setup point which is displayed on the operator's monitor 16. The operator decides whether to accept the proposal for the location of the next setup point or to choose a different setup point. Bite optimization is calculated by searching for the best center line consolidation, which can be expressed by the following formulas:
dn=Sb−Ho/F, where if (dn<0) then dn=0 and F≧2 i)
where dn is the width of the center line consolidation area of the stroke and “n” is the stroke number, ie. 1, 2, 3 etc. and “F” is an empirical factor with a minimum value of 2. As shown in
D=combined sum of dn, ii)
where D is the combined total width of the consolidation areas along the central axis where overlapping areas are not included in the calculation (
Q=100%·D/L iii)
where, Q is the percentage quality of center line consolidation and L is the length of the workpiece. If D=L, then consolidation along the entire length of the workpiece has been accomplished (
The system waits for a signal (148) that the upper die 32 is pressing down on the workpiece 30. After detecting the signal the system checks the bite ratio (149). If the bite ratio is less than 0.5, the system waits for the next signal (148). Otherwise, the stroke number is incremented by one (150).
The position of the manipulator 35 is recorded and compared to the positions of the left edge 38 and right edge 39 of the workpiece 30 in order to determine the setup position of the current stroke (152).
The system now checks whether the whole workpiece has been forged (154). If the workpiece has not been entirely forged, a new bite shift optimization (200) is calculated resulting in a proposal for the next setup point. If the workpiece has been entirely forged in the current pass, the program waits for the left edge 38 of the workpiece 30 to cross the laser line scanner measurement plane (130) and the length of the workpiece is determined. After the last pass is forged the tracking and bite shift optimization routine is terminated (164). A report is generated showing the distribution of the setup points and quality of the center line consolidation (160).
A measurement file is stored (162) in a central processing unit 22 and the stored process data can be used for off-line visualization.
Shown in
Shown in
The method and apparatus according to the present teachings assists the operator to make decisions for the setup point positions, because real time information about the current center line consolidation is provided in which all former setup points are displayed on a computer screen. The position of the next potential setup point is displayed and the quality factor for this setup point is calculated. The method provides a proposal for the optimal setup point, which is calculated using general and customer-specific rules and boundary conditions. The current teachings include a real time visualization of the process and the possibility to store the process data for off-line visualization which can be used for further analysis, e.g., to evaluate the work of the operators and so to improve the process.
Although described above as having the capability for interactive control by a human operator, the process may also be set to be fully automated such that upon an operator giving a start signal, the software runs automatically up to a defined number of passes and a measurement report is automatically generated.
While embodiments and applications of this invention have been shown and described, it will be apparent to those skilled in the art that many more modifications are possible without departing from the inventive concepts herein described. For example, although described above with respect to use LACAM measuring apparatus, it is envisioned that the optimized forging method according to the present invention may be performed using other electro-optical methods and apparatus such as a CCD-camera with image processing; a simple light sensor in case of small workpieces having a simple cut end; and/or by using laser scanner directly onto the workpieces end in the elongation direction. It is understood, therefore, that the invention is capable of modification and therefore is not to be limited to the precise details set forth. Rather, various modifications may be made in the details within the scope and range of equivalents of the claims without departing from the metes and bounds of the invention.
