Processing improvement of wedge components in the

2022-08-09
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Processing improvement of wedge components in automobile molds

as the quality requirements of automobile panels are higher and higher, the corresponding mold manufacturing accuracy requirements are also correspondingly improved. The proportion of side trimming and side trimming molds in mold production is also increasing, including side punching, side overturning, side trimming, hanging punching, hanging repairing, etc. This kind of mold is not only complex in structure, but also difficult to manufacture and process, because the number of wedges is large, the shape is complex, and it needs to be processed in a single piece. After assembly, it needs to meet the matching tolerance requirements of the design. The machining of wedges requires many times of overturning, clamping and alignment, which is inefficient and difficult to ensure the accuracy requirements. Therefore, how to complete the processing of non-standard wedge components quickly and well has become one of the urgent problems to be solved in mold production

structure description and processing process

Figure 1 shows the wedge component diagram of the side flanging die for flanging and punching of the outer panel of the rear right door. From the figure, it can be seen that this die has a total of 12 wedges and related components, and three groups of sub female wedges are used to realize the functions of side punching and side flanging. Typical wedge assemblies are generally divided into three parts - driver a, slider B and slider seat C. more complex wedge assemblies also have many types, such as double acting and double living

Figure 1 wedge assembly of flanging die on flanging punching side of rear right door outer panel

the working process of wedge assembly shown in Figure 1 can be briefly described as follows: first, the slider seat C moves downward with the press and pushes the slider B to move downward; When the lower surface of the slider B contacts the upper surface of the driver a, the slider B is subjected to the lateral force of the driver a. the normal protection and maintenance along the driver is of great significance to ensure the normal operation and measurement accuracy of the equipment. The upper surface of the slider a moves obliquely downward. When the limit is reached, the female die installed on the slider B and the male die installed on the lower die base complete the trimming or flanging work. The working process of double acting and double movable wedge assembly is more complex

we take one of the drivers a as an example to illustrate the processing process on the horizontal machining center: the first step is to process the sliding guide surface, the V-shaped guide plate mounting surface and the spring hook mounting groove, and then process the guide plate mounting surface and the limit table surface on both sides (Fig. 2A); The second step is to turn the workpiece over, take the guide sliding surface as the datum plane, and process the inclined guide sliding surface and the block mounting surface (Fig. 2b). The processing of these two surfaces requires programming and machining with a ball cutter. In addition, turn around 90 ° to process the mounting surface and pressing plate surface of one side return hook; Under this arrangement, the front retaining wall cannot be processed, so it needs to be turned over. Based on the inclined guide sliding surface, turn the machine tool around 90 ° to process the front retaining wall and keyway (Fig. 2C), and finally turn to the other side of the return hook mounting surface and pressing plate surface (Fig. 2D)

Figure 2 problems and cause analysis in the processing process

this kind of workpiece datum is generally small and difficult to clamp. A little carelessness will cause the workpiece to move and produce processing errors, which will make it difficult for subsequent assembly and debugging. It can be seen from the processing process of the wedge assembly that even if the simplest wedge is processed, it is necessary to repeat clamping for 3 times and turn around for 2 times. There will be errors in coordinate system conversion and tool setting due to multiple clamping and alignment in the machining process. The cumulative errors of tools and machine tools will also directly affect the trimming or flanging accuracy of products. If the machining accuracy cannot be effectively guaranteed in the machining process, the error will be accumulated in the subsequent fitter assembly and debugging work

through analysis, we can know that the accuracy is mainly affected by the following aspects: the dimensional tolerance and angular error of the upper surface of driver a, the dimensional and angular error of the lower surface of slider B, the dimensional and angular error of the upper sliding surface of slider B, and the dimensional and angular error of the lower sliding surface of slider seat C

the main reasons for the deviation are as follows:

1. The large manufacturers who contact the sliding surface of the wedge assembly with the lower die occupy most of the market share, and the gap error formed by the distance

2. If the mounting surface of the limit block is unbalanced, it is easy to cause premature wear of the mechanical part and errors caused by inadequate data error research and matching

3. The deformation of the longer wedge due to stress will also cause uneven clearance error

4. The flatness error of the guide sliding surface is caused by tool wear in the machining process

5. The angle error caused by the conversion angle of the machine tool in the machining of the punching edge

6. measurement error of tool length and dimension measurement error during operation

7. machining error of wedge assembly itself

solutions

1. driver a

first process the bottom and retaining wall, and then install it on the sine Tong. Based on the bottom and retaining wall, process the sliding guide surface, and the lug also needs to be horizontally milled or turned around. The main function of sine clamp is to reduce clamping times and greatly improve work efficiency. The key dimensions of the processing driver a are the height and parallelism of the guide sliding surface, and the relative error E1 between the guide sliding surface and the mold center should be guaranteed to be between (0, 0.02)

2. slide block seat c

most of the C part of the slide block seat is integrated with the die seat, with complex shape and many processing related dimensions, including travel limit block installation table, spring installation table, V-guide plate installation table, safety block installation table and guide sliding surface. The red area in Figure 3 is the part to be processed. Generally, it is processed as a whole during one-time processing, which mainly ensures the dimensions of the V-guide plate installation table and the guide sliding surface, and the tolerance is processed according to the nominal dimension. Generally, the processing method adopts ball head cutter programming processing. The root knife can be used to clear the root or mill the depth. It can also be turned around and processed with an end mill. In this way, there is no need to grind, and the root processing quality is better

if the slide block seat and die seat are separated, the processing method is like driver a

the tolerance of Part C of the slider seat shall be processed according to the nominal size to ensure that the flatness E2 is within (-0.02, 0.02) and the accuracy E3 of the sliding guide surfaces on the left and right sides is within (-0.02, 0.02)

3. slider B

slider B is the most important part of the wedge assembly, and its most critical dimension is the distance and parallelism between the sliding guide surface and the side trimming edge

for the slider with vertical surface, we first process the sliding guide surface of the slider, and then install it on the rotating workbench. With the sliding guide surface as the bottom surface, we use horizontal milling to process the mounting surface and keyway of the block guide plate, and then rotate the workpiece twice to process the lugs at both ends respectively. Finally, place it on the main forum and adjust the angle on the sinusoidal pliers to process the V-shaped guide plate mounting surface, the guide sliding surface and the lugs at both ends

Figure 3 slider seat C entity and sectional view

in addition, some sliders have no vertical plane or the vertical plane is too small, which makes it difficult to clamp. We use a method similar to that shown in Figure 2a to clamp and align. After processing the V-guide plate mounting surface, sliding guide surface and two end lugs, place this surface as the bottom surface on the sine Tong to adjust the angle processing, and first process the sliding guide surface (Figure 2b). It can also be programmed and processed with a ball head knife without sinusoidal pliers. Finally, the mounting surface and keyway of the block guide plate are processed with the ground sliding guide surface as the bottom surface (Fig. 2C). Rotate the workpiece twice to process the lugs at both ends respectively (Fig. 2D). Ensure that the distance tolerance between the side trimming edge and the guide sliding surface is controlled within the blanking gap, the accuracy E4 of the guide sliding surface on both sides is (-0.02, 0.02), and the parallelism is guaranteed by the accuracy of the NC machine tool

after the process improvement, the final mold product meets the design requirements through inspection and fitter assembly. Figure 4 shows the wedge processed before the process improvement, and the cushion is added at the figure. Figure 5 shows the wedge processed after the process improvement, which improves the assembly quality and efficiency

Figure 4 wedge processed before improvement (the circle is an adjusting gasket, which is fixed with screws)

Figure 5 wedge processed after improvement - without pad

conclusion

from the above processing process, it can be seen that no matter which processing method is adopted, the processing of wedge components is still very cumbersome, and the probability of error is also great. In order to ensure the accuracy of processing, numerical control operators, fitters, assemblers and programmers need to strengthen their own technical quality, improve their skills and level, and improve the processing technology through the following measures:

1 Improve the quality awareness of operators, strengthen testing, and do a good job in benchmarking. Mark the tolerance of key dimensions to ensure that a single piece conforms to the nominal size

2. The alignment and tool setting conversion should be accurate, the clamping must be reliable, and the workpiece should be detected at any time during the processing process

3. The programming and processing shall adopt the method of reducing the cutting depth as far as possible, and try to install it on the die base for processing without interference

4. Find out the position of the bottom dead center, and the cushion block must cushion the wedge accurately

5. There is a dimension chain between the dimensions of components such as wedges, and finally a closed loop is formed. If a component has a tolerance, the tolerance of the matching component must be reduced. Through assembly, the matching tolerance can be controlled within (-0.02, 0.02)

by taking the above measures, the processing error of all workpieces in our company has been basically guaranteed

the fitter can consciously accumulate the error on the slider B during the assembly process. As long as the two key dimensions of the distance and parallelism between the sliding guide surface of the slider B and the side trimming edge are guaranteed, even if there is an error, it will not affect the trimming or flanging clearance, so as to reduce the amount of adjustment work and padding phenomenon. (end)

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