Application of the hottest MasterCAM in injection

2022-08-17
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An example of the application of MasterCAM in the processing of injection mold

the following introduces the processing process of the injection mold of the back shell of the regulated power supply on the computer processing center, which is the main processing method of the injection mold at present. The mold was processed with Fujitsu mcv-560 computer processing center during the author's work in the mold CNC processing center of Fenggang Yili Electronics Group Co., Ltd. in Dongguan, Guangdong Province. The most popular PC machining center software MasterCAM8.0 system is adopted at present. Practice has proved that the processed mold fully meets the design requirements and ensures the product quality. This mature CNC mold processing method has high reference value

1. Structural characteristics and technical requirements of the rear shell of regulated power supply Figure 1 is the schematic diagram of the rear shell of regulated power supply of a company. It is required to produce 200000 plastic parts without mold repair. The plastic part is made of mixed engineering plastics of black polystyrene PS and polycarbonate PC, with natural transition on the surface and no flow marks, silver wires and other defects. The inner surface of the plastic part is smooth, the roughness is Ra0.32, and the outer surface is corroded. In addition, the wall thickness of plastic parts is =2.5mm, the upper structure is a convex cuboid (its edges and fillets R1.0), and all edges and fillets of the lower structure are R8.0

2. Mold structure design mold core processing technology analysis through the analysis of product structure and technical requirements, combined with the specific situation of our mold CNC processing center, the following arrangements are made: (1) material selection, using Sweden 718 mirror mold steel as the core material of the front and rear mold, which is a reliable guarantee for the production of 200000 plastic parts without mold repair. However, its hardness is above hrc39, so it is difficult to process. (2) The die adopts the overall structure, and the Wenxing die core material is hidden into the mold embryo. The front and rear dies are processed with the overall structure, which is roughened by the computer CNC machining center, and then processed to the size by the EDM machine tool. According to the schematic diagram of plastic parts, the actual parting surface of the mold combined with the development of the industrial park should be set at the mating surface of the rear shell (that is, the bottom plane of the rear shell). Refer to the following front and rear mold processing process (Fig. 2, FIG. 5). (3) According to the cutting requirements of cutting tools, white steel knives are more suitable for rough machining and semi precision machining. For hard materials, it is better to adopt the bottom-up machining method instead of the horizontal cutting method. Forward milling can improve the cutting conditions and feed tool wear. The alloy tool is suitable for transverse feed, with small cutting concentration and high cutting speed. The disadvantage is that it is difficult to cut down, and there is no big difference between forward and backward milling. Therefore, when arranging the machining process, the tool path should be reasonably selected. During rough machining (rough opening), the cutting feed should be carried out outside the machined part. It is absolutely not allowed to directly cut vertically on the machined workpiece, which will lead to knife sticking and knife breaking accidents. When the rough workpiece (mold core) is rough machined in the way of pocket or contour, the oblique straight cutting or spiral cutting can be used to gradually deepen the cutting concentration in place, which can improve the cutting performance and processing quality. 3. In the CNC machining process of the front mold, because the maximum geometric dimension of the rear shell of the regulated power supply is about 1209060 (length, width and height), the existing flat bottom ball cutter with a diameter of =30 alloy (cutter radius r5.0) can be used for rough machining to improve the cutting efficiency. In processing, we adopt the following processing technology: (1) rough: processing with a flat bottom ball cutter with a diameter of 30mm. Adopt the slotting method (Pocket), feed diagonally (inclination angle =5), gradually increase the cutting depth to the specified value for cutting, the cutting amount of each layer is h=2.5mm, and the tool speed is n=2500r/min. The final allowance =0.5mm is used as the cutting amount of semi finishing and finishing. See Figure 2 for rough machining tool path

(2) semi finishing and finishing: select an alloy ball head cutter with a diameter of 12mm, and carry out horizontal feed machining by parallel milling. The tool path is zigzig Zig back and forth in the direction of 225 with the ox axis of the machining center. Semi finishing allowance =0.15mm is reserved for finishing cutting, and all r8.0mm fillets on plastic parts can be directly processed by cutters. However, the rounded corner of the square groove R1.0 sunk by the front die cannot be processed to the size, and only the tool radius of r6.0 can be obtained. The finishing tool path and finished products are shown in Figure 3

4. CNC machining process of front mold R1.0 corner clearing copper electrode (copper male). Through the above machining process, most of the mold surfaces have been machined in place, and only the rounded corners of the sunk square groove R1.0 cannot be machined to size. We can deal with it by electro etching. By using the pulse discharge between the electrode (copper male) of the EDM machine tool and the processed mold, the excess metal is etched to meet the requirements of surface quality and design size. With the help of auxiliary fixtures, such as translation head, rotating head, etc., the electrode can expand and modify the cavity to meet the requirements of different workpieces. Copper electrode (copper male) is generally divided into coarse and fine. The material is generally processed with red copper, and Gu is called coarse male and fine male. For special composite workers, the difference is huge enough. Thin plastic parts, such as watches, pagers, mobile phones, mobile communication devices and so on, usually have a middle electrode (Zhonggong). The discharge gap of copper is generally related to the size of the workpiece. Generally, the unilateral discharge gap of coarse male is 0.8mm, that of medium male is 0.5mm, and that of fine male is 0.2mm The front mold processing of the back shell of the stabilized voltage power supply described in this paper can meet the size requirements with only one fine male because the amount of metal that does not reach the design size is very small The processing process of copper is as follows: blanking rough machining shape (contour), rough machining large surface, finish machining large surface, finish machining shape, and finally machining the table scoring benchmark (EDM benchmark, i.e. the boss at the bottom of the copper meter), rough machining shape (contour), finish machining large surface cutter path and finished products are shown in Figure 4

5. The CNC machining process of the rear mold requires 200000 plastic parts to be produced without mold repair. We selected Sweden 718 mirror mold steel as the mold material, which has high hardness and is difficult to cut. There are generally two methods to take the glue position (particle thickness): (1) tool correction method: if you need to take the glue position of 2.0mm, you can use the r14mm ball cutter to write the CNC program and use the r16mm ball cutter to process. However, you must pay attention to that after the tool is set, the workpiece should be processed by lowering the parting surface by 2.0mm (this point can be guaranteed by the CNC machining center console, or by translating 2.0mm in the CNC program). (2) Allowance method: processing allowance of -2.0mm is adopted. In this paper, we adopt the latter method for processing, and the processing technology is as follows: (1) roughening (I): processing with 2D shape (contour), cutting with arc tangent of 30 alloy flat bottom ball cutter (the gap between global production capacity and consumption of alloy cutter radius may reach 22.5 million tons r5.0mm), and the cutting depth of each cutter is 2.5mm; A column with a contour of -2.3mm is processed to facilitate subsequent processing. (3) Roughening (II): also use 30mm alloy flat bottom ball cutter to roughen the program in the form of contour, and arc into the tool from the outside of the rear mold for equal height cutting, with allowance = -2.3mm and tool speed n=3500r/min. See Figure 5 for rough machining tool path

(4) finish machining (I): use 12mm and 5.0mm alloy ball head cutters respectively, and take the machining allowance of -2.4mm and -2.5mm for machining. The tool path adopts the equal tool path, and enter the tool at the 225 angle with the ox axis of the machining center. The tool speed is n=3500r/min. In the CNC programming process of finishing tool path, Qing paid special attention to whether the tool will cross the cutting surface. This phenomenon occurs in this example. The over cutting tool path should be dealt with in time, otherwise the consequences can't be set in 2019! See Fig. 6 for the processed finishing tool path

(5) finish machining (II): finish machining the 2D shape of the rear mold contour at the -2.5mm margin. Use the 2D shape method, select 12mm flat base alloy cutter for machining, and the cutting speed of the cutter is n=1500r/min. In addition, because the processing of some parts caused by the previous finishing knife passing through the cutting surface cannot be processed, it is also necessary to write a local light knife program on the side of the rear die to finish the processing of the rear die

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