Wire cutting is a key process in the manufacture of rack tools. All the tooth parameters of the rack tool—the pitch, the tooth thickness, the full tooth height, the helix angle, the back angle, and the tooth angle—are all formed by this process. Due to the stroke limitation of the CHARMILLES 290 wire-cutting machine, only the rack tool with a length of ≤350mm can be processed, and the maximum length of the rack tool ordered by the user is up to 480mm. In order to use the existing equipment to process the over-travel large-length rack tool, It can only be processed by the knife attachment method.
Machining is a process in which a rack tool is divided into two sections. The upper and lower nozzles of the wire cutting machine are moved according to the programmed machining path, and there is a large space around the nozzle. Therefore, one end of the rack tool can be fixed in the machining stroke according to the machining direction of the program, and the other end is placed beside the nozzle. At the gap, after the L1 section of the tool is finished, loosen the clamp and move the workpiece diagonally in the X-axis direction in the fixture positioning surface, so that the L2 section of the tool completely enters the machinable range and is clamped and tightened. Measuring the machined datum surface to find the cutting point of the second section of the machining program, the wire cutting process of the entire rack tool can be completed by executing the second section of the machining program.
To achieve the above processing principles in actual machining, the following problems must be solved:
The determination of the position of the L1 segment. In order to determine the safe position of the L1 segment, a simulation run must be performed on the on-line cutting machine. Under the premise that the nozzle does not collide with the workpiece, the height of the upper nozzle should be reduced as much as possible; in addition, the interruption point of the two-stage machining program should be located at the midpoint of the tooth root (as shown in Figure 2) to avoid Leave a knife mark on the critical dimension surface. There should be a partial overlap (~0.3mm) between the two sections to avoid the formation of the joint.
The measurement of the datum. In theory, by accurately measuring the machined reference planes A and B, the cutting point of the second section of the machining program in the X and Y directions can be obtained. However, in the actual machining, since the X and Y axes are simultaneously moved when machining both sides of the toothed surface, and only the Y axis is moved when the A surface is machined, it is difficult to ensure the processing quality of the A surface; and the distance between the upper and lower nozzles is large. The tension of the electrode cutting wire is not easy to meet the requirements during finishing, which may cause the A-face processing size to be unstable, which leads to a large reference surface measurement error, which affects the determination of the cutting point of the second-stage machining program. In addition, when the oversized workpiece is reworked, since the A surface has been cut off after the second machining program is executed, it can no longer be used as the reference surface. In the processing practice, it is found that the front tooth side processed by the first step program is better as a measurement reference. Since the surface is also a design reference surface, if it is used as a measurement reference surface, the reference coincidence can be ensured.
Since the second-stage machining program is based on the machining surface of the first-stage machining program, even if there is a machining error, the consistency of the error direction can be maintained, and the influence of the machining error can be reduced. However, when calculating the moving distance, the measurement error caused by the non-perpendicular contact between the electrode cutting wire and the reference surface should be considered. The distance should be converted to the X-axis direction and then moved to the cutting point. By changing the reference plane, the measurement accuracy and machining accuracy can be further improved, and the reworked workpiece can be further processed. By measuring the pitch and the tooth thickness value and converting according to the measured value, it can be judged whether the rack tool is qualified during the machining process. If problems are found, the machining position and machining dimensions can be adjusted at any time (if the tool is removed and tested, it is difficult to ensure the machining accuracy after the tool is re-clamped).
The clamping of the workpiece. Since the length of the processed rack tool is large and the part is clamped during processing, the clamping direction varies with the helix angle and is not perpendicular to the horizontal plane, so the rigidity of the clamp is high; meanwhile, when the workpiece moves Keeping the direction unchanged, the requirements for fixture positioning accuracy are also high. In the actual machining, after the workpiece is moved, the position change of the tooth top and the vertical plane of the adjacent three teeth is detected by the dial indicator, and the position of the workpiece is adjusted to meet the installation accuracy requirement, and then the electrode cutting wire is used for measurement to determine Cut position. The method of connecting the knife can reduce the processing difficulty of the large-sized rack tool and expand the effective processing range of the wire cutting machine. In addition, since it is possible to determine the processing qualification of the workpiece other than the circular curve on the machine, it is not necessary to remove the workpiece for inspection, and it is difficult to completely reset the re-clamping position on the machine tool when the error repair processing is required.
Machining is a process in which a rack tool is divided into two sections. The upper and lower nozzles of the wire cutting machine are moved according to the programmed machining path, and there is a large space around the nozzle. Therefore, one end of the rack tool can be fixed in the machining stroke according to the machining direction of the program, and the other end is placed beside the nozzle. At the gap, after the L1 section of the tool is finished, loosen the clamp and move the workpiece diagonally in the X-axis direction in the fixture positioning surface, so that the L2 section of the tool completely enters the machinable range and is clamped and tightened. Measuring the machined datum surface to find the cutting point of the second section of the machining program, the wire cutting process of the entire rack tool can be completed by executing the second section of the machining program.
To achieve the above processing principles in actual machining, the following problems must be solved:
The determination of the position of the L1 segment. In order to determine the safe position of the L1 segment, a simulation run must be performed on the on-line cutting machine. Under the premise that the nozzle does not collide with the workpiece, the height of the upper nozzle should be reduced as much as possible; in addition, the interruption point of the two-stage machining program should be located at the midpoint of the tooth root (as shown in Figure 2) to avoid Leave a knife mark on the critical dimension surface. There should be a partial overlap (~0.3mm) between the two sections to avoid the formation of the joint.
The measurement of the datum. In theory, by accurately measuring the machined reference planes A and B, the cutting point of the second section of the machining program in the X and Y directions can be obtained. However, in the actual machining, since the X and Y axes are simultaneously moved when machining both sides of the toothed surface, and only the Y axis is moved when the A surface is machined, it is difficult to ensure the processing quality of the A surface; and the distance between the upper and lower nozzles is large. The tension of the electrode cutting wire is not easy to meet the requirements during finishing, which may cause the A-face processing size to be unstable, which leads to a large reference surface measurement error, which affects the determination of the cutting point of the second-stage machining program. In addition, when the oversized workpiece is reworked, since the A surface has been cut off after the second machining program is executed, it can no longer be used as the reference surface. In the processing practice, it is found that the front tooth side processed by the first step program is better as a measurement reference. Since the surface is also a design reference surface, if it is used as a measurement reference surface, the reference coincidence can be ensured.
Since the second-stage machining program is based on the machining surface of the first-stage machining program, even if there is a machining error, the consistency of the error direction can be maintained, and the influence of the machining error can be reduced. However, when calculating the moving distance, the measurement error caused by the non-perpendicular contact between the electrode cutting wire and the reference surface should be considered. The distance should be converted to the X-axis direction and then moved to the cutting point. By changing the reference plane, the measurement accuracy and machining accuracy can be further improved, and the reworked workpiece can be further processed. By measuring the pitch and the tooth thickness value and converting according to the measured value, it can be judged whether the rack tool is qualified during the machining process. If problems are found, the machining position and machining dimensions can be adjusted at any time (if the tool is removed and tested, it is difficult to ensure the machining accuracy after the tool is re-clamped).
The clamping of the workpiece. Since the length of the processed rack tool is large and the part is clamped during processing, the clamping direction varies with the helix angle and is not perpendicular to the horizontal plane, so the rigidity of the clamp is high; meanwhile, when the workpiece moves Keeping the direction unchanged, the requirements for fixture positioning accuracy are also high. In the actual machining, after the workpiece is moved, the position change of the tooth top and the vertical plane of the adjacent three teeth is detected by the dial indicator, and the position of the workpiece is adjusted to meet the installation accuracy requirement, and then the electrode cutting wire is used for measurement to determine Cut position. The method of connecting the knife can reduce the processing difficulty of the large-sized rack tool and expand the effective processing range of the wire cutting machine. In addition, since it is possible to determine the processing qualification of the workpiece other than the circular curve on the machine, it is not necessary to remove the workpiece for inspection, and it is difficult to completely reset the re-clamping position on the machine tool when the error repair processing is required.
Needle Bearing,Flat Needle Roller Bearing,Needle Roller Bearings,Sealed Needle Roller Bearing
Shanghai Yi Kai Cheng bearing Co., LTD , https://www.ykcbearing.com