Research on NC Machining Process Based on IPW
Utilize UG software CAM module to compile the processing procedure, put forward the best numerical control processing craft based on IPW, improve the efficiency of the mould and touch block processing.
introduction
Mold processing is an important part of mold manufacturing. It not only determines the surface quality and accuracy of the mold but also affects the manufacturing cycle of the mold. Choosing a reasonable processing technology is the basis for solving these problems. Due to the small batch nature of the single-piece processing of the mold, a reasonable processing process cannot be explored by the processing process. Therefore, optimization of the manufacturing process using CAM software is the current trend of mold processing. . Currently there are many CAM software on the market, mainly Unigraphics (abbreviated as UG), Powenvill, MasterCAM, Cimatron and so on. Because the operation is simple and convenient, MasterCAM and Cimamon and other software have a large share in the domestic market, but their CAD functions are very weak, and complex designs need to be completed with other CAD software. Relatively speaking, UG and Powermill belong to better CAM software, especially the CAD/CAM function of the former is very powerful and has greater development prospects. Based on UG's CAM module, this paper discusses the best NC machining process based on the W cast iron module of a coated sand mold for the actual production process.
Figure 1 shows a brake caliper coated sand mold module using UG design
1 IPW-based CNC machining process
The processing of a part includes many steps. In the traditional NC machining programming, it is not clear which material has not been machined after each step of the machining process, and when programming the roughing, semi-finishing, finishing or tool changing processes, all are programmed. It starts from the part blank, which results in the semi-finishing, finishing, or tool change machining. The CNC machine must finish the surface of many blanks that have been machined according to the speed of the work (we call it empty cutting). A lot of hours.
In the actual processing, after each machining process is completed, there is an intermediate process of blanks called IPW (In Process Work-piece). During programming, the IPW generated after the previous process can be used as the blank for the subsequent processing, thereby reducing the number of blanks and improving the processing efficiency. This is the IPW-based NC machining process that we are discussing today, and it is also a unique function provided by the UG/CAM module.
The quality and efficiency of the modular NC machining basically determine the quality and delivery time of the mould. Therefore, it is necessary to discuss the best numerical control processing technology to improve the quality of molds and timely delivery. The caliper body coated sand stacking die casting mold module is shown in FIG. 1 . The blank is obtained by the casting method, and then processed to obtain the mold module. As can be seen from Figure 1, the module requires full root removal (no fillets) on the parting surface, and the remaining minimum fillet is R3~5mm. In addition, in order to reduce costs, the parting surface will be cleared by hand to remove the roots by hand. Therefore, it is initially determined that the minimum tool diameter for finishing is 8mm. According to the characteristics of the cast iron module, the alloy insert tool was initially selected for roughing and semi-finishing, and the solid carbide tool was used for finishing.
The processing is completed by three processes of roughing, semi-finishing and finishing. The IPW-based NC machining process is discussed below.
2 IPW-based CNC machining applications
2.1 Roughing process
The minimum tool diameter for roughing is determined to be 16 mm, the allowance for machining is 0.6 mm, and the bottom is 0.2 mm. For rough machining of mold modules, cavity milling is generally used. Since the cavity milling is layered in the depth direction, no matter how fine the layers are, there will always be steps. Therefore, after the cavity milling, you must perform contour milling. Contour milling is a profiling process along the cross-sectional profile of the part. The cutting conditions are relatively uniform, the cutting is smooth, and the surface roughness of the workpiece is also relatively good. Here we mainly compare the traditional cavity roughing and IPW-based cavity roughing process.
Although the shape and shape of the mold module is a rectangular parallelepiped, it already has a cavity inside, as shown in Fig. 1. However, the traditional cavity milling process uses a rectangular parallelepiped as the machining blank for numerical control programming, and the same processing as the mold module cavity is performed. After a certain cavity with a certain machining allowance, the remaining steps are then high-milled with a flat cutter. The processing technology effects and parameters are shown in Figure 2, and the total processing time is 372.3 minutes.
Figure 2 Traditional roughing process parameters and effects
It can be seen that since the blanks that we have fabricated have only a uniform 6mm allowance, which is different from the depth of the inner cavity, and the shape of the inner cavity has been the same as the inner cavity of the cavity milling shown in FIG. In the traditional cavity milling process, the first 16mm flat-blade cavity milling process inevitably has a lot of empty knives, which not only adds a processing process, but also increases a lot of man-hours.
IPW-based cavity milling processing parameters and the effect shown in Figure 3. The total processing time is 122.4min. It is the use of the mold design process to produce the mold module diagram (Figure 1) as a traditional cavity after the middle of the milling process, and then on its basis for high-altitude milling milling cutter CNC machining programming, although the surface of the rough programming increased NC programming time and positioning auxiliary time, but due to the elimination of the first more frequent blanking process in the traditional cavity milling, can shorten the CNC machining man-hours more than 50%, greatly improving the efficiency of roughing.
2.2 Semi-finishing process
Since the diameter of the finishing tool is 8 mm, the minimum tool diameter for semi-finishing is determined as 10 mm or 8 mm, and the machining allowance is 0.1 mm. Here we also compare the traditional semi-finishing process and semi-finishing process based on IPW.
Figure 3 Roughing process parameters and renderings based on IPW
The traditional semi-finishing process is mainly to gradually reduce the diameter of the tool so as to gradually reduce the machining allowance. When the NC machining program is programmed, the contour after roughing is used as the basis for programming and positioning of the tool. The programming process takes a long time. At the same time, the diameter of the roughing tool is taken into consideration as 16 mm. Generally, the diameter is 12 mm. CNC machining process, the specific parameters: the side of the processing allowance 0.45 mm, the bottom of the processing allowance 0.15 mm, each layer depth of cut 0.4mm; processing time: 224.2min. Then use 10mm ball knives and other high milling CNC machining process for the second processing, the specific parameters: the side of the processing allowance 0.1mm, the bottom of the processing allowance 0.1mm, each layer depth of cut 0.3mm; processing time: 284.1min. The total processing time is 508.3 min. The semi-finishing based on IPW is similar to the roughing process based on IPW, that is, an IPW is generated using a 16-mm flat-cutter roughing program, and then based on this IPW, the 8-mm flat cutter is used for cavity milling directly. Processing. The side machining allowance and the bottom machining allowance are both 0.1 mm, the depth of cut for each layer is 0.25 mm, and the total processing time is 391.2 min.
For two processes, as shown in Table 1, it can be seen that the IPW-based semi-finishing can shorten the number of CNC machining man-hours, and that the corners of the IPW process have reached R4mm, leaving smaller fillets for subsequent finishing. Machining allowance.
Table 1 Comparison of NC Machining Process and Working Hours for Cast Iron Mold Modules
2.3 Finishing process
UG3.0 has made major improvements to contour milling and finishing, combining the two steep machining procedures required by UG 2.0, such as high steep slope processing and contour gentle slope processing, to reduce the number of processing operations error. Finishing process is relatively simple, we mainly use the following processing technology: 8mm ball knives and other high milling +8mm flat knife surface milling. This phase does not need to be based on IPW.
To sum up, the best numerical control processing technology for coated sand mold-stacked cast iron mold modules is shown in Table 2. The process has the advantages of saving man-hours, good surface quality and simple process.
Table 2 The best numerical control process of cast iron mold module
3 Conclusion
Utilize UG software CAM module to compile the processing program, and take full advantage of UG software's unique IPW-based processing function, aiming at the characteristics of the mold module's small post-cast machining allowance, and proposes the IPW-based mold module NC machining technology and tradition. Compared with the numerical control processing technology of the mold module, this process has the advantages of saving processes, saving tools, and saving man-hours, and improves the efficiency of mold module processing in ensuring the accuracy and surface quality of the mold. Moreover, the integration of mold design and manufacturing is realized, and at the same time, the mold can be programmed at the same time as the corresponding NC machining programming at the manufacturing stage. This is in contrast to the traditional NC program preparation and processing after the part blank comes out of the manufacturing stage. In fact, the production cycle of the mold is shortened.
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