Cimatron is a set of excellent CAD/CAM software for tool and mold manufacturing. It not only provides complete modeling design, drawing, analysis and processing programming functions, but also provides an ideal solution for the entire manufacturing process of cavity molds.
Cimatron is the most widely used three-axis milling machining program for cavity mold processing, applying its original intelligent NC programming technology based on blank margin knowledge, combined with various unique features of the processing mold parts, making it the most ideal type today. One of the cavity CAM solutions. The following uses the Cimatron's application in actual machining to introduce its commonly used strategies for numerical control of cavity dies.
1 Common strategies for Cimatron cavity mold NC machining
In the three-axis CNC milling process of cavity mold parts, from the regular shape blanks to the part processing before finishing (mainly refers to polishing), the milling process can be generally divided into roughing, semi-finishing, finishing and clearing Process four types of processes.
In the roughing of blanks, although other forms of machining such as plunging may be used, contour cutting is still the most common form of actual machining. Cimatron offers POCKET, ZCU T, WCU T three processes to support this form of processing. Because the WCU T-ROU GH process has the advantages of efficient round cutting passes and intelligent feed settings, it also has a unique inter-layer processing function and is therefore the most commonly used roughing operation.
The ideal semi-finishing should be based on the calculation of the tool path based on the blank remaining after rough machining. Cimatron has a unique optimal prior optimization technique. Using the WCU T-ROU GH process and selecting the WITHSTOCK option in the machining parameters, the tool can be used. The trajectory is generated according to the residual condition of the blank after rough machining, which not only completely eliminates the empty knife phenomenon, but also the cutting load of the tool is more reasonable and the trajectory is smoother. Compared with the post-optimization technology, a more ideal semi-finishing tool path can be generated. By properly setting the inter-layer processing parameters, the residual of the blank between the two cutting layers can be removed by reprocessing along the processing surface, and can be achieved compared to the method of improving the surface processing accuracy of the part by reducing the height of the layer drop. On the premise of the same effect, the processing efficiency is greatly improved.
For part finishing, Cimatron offers a wide range of machining processes to support different finishing methods. Such as SURMILL (parameter line processing), SURCLR (limit line processing), SRFPKT (face processing), 3D STEP (three-dimensional step processing) and WCU T - FIN2ISH (contour processing), etc., in which the entire part of the surface of the SRFPKT And WCU T-FINISH is the most commonly used.
For the entire processing surface, it is always unreasonable to use a finishing process. For the flat surface whose slope is close to the horizontal plane, the SRFPKT process is better for the surface processing, and for the steep surface whose slope is close to the vertical surface, the WCU T-FINISH process is generally preferred. Therefore, firstly, the slope of the machined surface needs to be analyzed, and then the proper form of travel is the most ideal way of processing according to the different characteristics of the machined surface. Using the WCU T-FINISH process and selecting BETWEEN LAYERS : HORIZ in the process parameters, the slope of the machined surface can be analyzed automatically and different processing modes can be used for different areas based on the analysis results.
The local root removal process is also crucial to the processing of the mold. In addition to the use of REMACHINE: PENCIL based on the corner center of the model for single root removal, REMACHINE:CL EANUP can be used to perform multi-pass automatic cleaning based on the blank allowance. Root to achieve a smooth cutting tool, load the purpose of uniform. Using this procedure, the steep slope and flat areas can be processed separately using the area slope analysis algorithm, and the corresponding tool paths can be generated.
The commonly used strategies for numerical control of cavity dies are shown in Table 1.
2 Cimatron typical cavity die parts processing parameter settings
Typical cavity mold parts include cores, cavities, and electrodes required for EDM. In each process, especially in the roughing process, different processing parameters should be set according to the different characteristics of the parts in order to achieve the desired processing results. The following describes the typical parameter settings for roughing of various parts.
2. 1 cavity processing
For rough machining of general cavity parts, the WCU T-ROU GH process can be used. According to the characteristics of such parts, the following settings can be made in the processing parameter table:
(1) The tooling mode parameter is generally set to SPIRAL CU T , making the tool round around the machined surface.
(2) The type parameter of the machining model is generally set to OPENPART: NO to limit the feed to the machining range. If there is an island with a different height from the bottom of the cavity inside the part, as shown in Fig. 1, it should be set to OPEN + ISLAND to use the blank infeed or the internal pre-boring at the different cutting layers.
(3) The feed parameters generally use AU TO ENTRYPOINTS (automatic feed point). When it is required to drill the pre-hole point, it can be set as OPTIMIZED ENTRY PNT (optimized feed point), and with setting CREATE ENTRY PNT : YES to generate Less pre-holes, as shown in Figure 1.
(4) The feed angle parameter RAMP AN GL E is generally set to 5°~10° to adopt helical feed, and the cutting sequence parameter is set to INSIDE OU T to facilitate the generation of spiral. If necessary, adjust the spiral radius by resetting the MAX RAMP RADIUS parameter.
(5) For deeper cavity machining, if a tool with a machining dead zone (such as a circular knife with a carbide insert attached) is used to cut it downward, a knife rest may occur. By setting the MIN PLUN GESIZE to the tool diameter minus twice the fillet radius, it is possible to prevent cutting into the area where the machining range is too small to avoid the possible danger.
2. Processing of 2-core parts
Roughing also uses the WCU T-ROU GH process.
(1) The parameter of the cutting tool can be set as STOCK SPIRAL so that the tool can be cut around the blank to improve the cutting efficiency of the blank. Figure 2 shows the different roughing toolpaths generated for the same part after using SPIRAL CU T and STOCK SPIRAL parameters, respectively. (Mould Talent Network welcomes you, URL http://)
(2) The type parameter of the machining model is generally set to OPENPART:OU TER ONL Y. This ensures that the tool advances outside the part. The cutting sequence parameter is generally set to OU TSIDE IN and the feed angle parameter RAMP AN GL E is generally set to 90°.
(3) The feed parameter is generally set to AU TO ENTRYPOINTS. If not ideal, DE2FINE ENTRY POINTS can be selected.
2. 3 electrode processing
The roughing setup of the electrodes is basically the same as the core. The difference lies mainly in finishing.
The electrode model is generally obtained directly from the cavity model, however, there is a discharge gap between the electrode and the cavity during electrical machining. Since the electrode model may consist of many surfaces, it may be difficult to directly offset the surface of the model. In order to compensate for the discharge gap, a certain amount of overcutting of the processing surface is required.
There are many ways to achieve a certain amount of overcutting of the machined surface. For example, a smaller tool is used for calculation, and a “cheat knife method†using a larger tool is used for actual machining. However, the most common method is to set a negative value equal to the discharge gap for the SRF.OFFSET parameter in the finishing parameter table. In this method, the tool must be a ball or fillet and the radius of the fillet is greater than this value.
In addition, different faces may need to set different overshoots. This can be achieved by defining faces with different overcutting requirements as PART SURF and PART2SURF, respectively, and setting different offset values.
3 Application case
3. 1 processing of hook forging die cavity
The hook forging die is a typical HAL F die. The cavity is symmetrical up and down. The three-dimensional solid model of the die is shown in Figure 3. The blank has a border size of 240 mm × 240 mm × 60 mm and the top and bottom planes and the contours have been finished. Now we need to complete the positioning hole and the entire cavity processing in the machining center. The generated processing steps are as follows:
(1) Roughing is divided into two steps according to depth
Extraction of pocket contours using POCKET-CONTOURROU GH + FINISH with a Ø12 mm dia. flat-bottom cutter with a machining depth range of 0 to - 1.50 mm, one-off roughing of the rim with SPIRALCU T finishing
The remaining part uses WCU T-CONTOUR ROU GH. The tool is still a Ø12 mm flat-bottomed cutter with a machining depth range of 1.50 mm to minpz. The contour roughing of the cavity is performed in the form of a SPIRAL CU T. Because the flat-bottom cutter cannot be machined to the flat part of the bottom surface of the cavity, it is necessary to use a ball knife to perform secondary rough machining on the cavity.
(2) Semi-finishing
With the WCU T-CONTOUR ROU GH , the tool uses a ball end mill with a diameter of <10 mm. Processing parameters select SPI2RAL CU T, WITH STOCK, BETWEEN LAYERS :ON SRF , residual residual at the bottom of the processing cavity.
(3) Finishing
With WCU T-CONTOUR FINISH, tools with a diameter of <6 mm ball-end cutter. Processing depth range - 1. 50mm ~ minpz, processing parameters selected SPIRAL CU T, BE2TWEEN LAYERS: HORIZ. The sub-region machining based on the results of the automatic slope analysis is adopted. The steep surface is processed with the same height, and the flat surface is subjected to the finish cutting with the surface circumcision.
(4) Root processing
Use REMACHIN-CL EANUP with a ball-nose cutter with a diameter of <4 mm. The processing parameter selection PREV. TOOL = BALL6, SPL IT HORZ VERT, is mainly used for clear roots at the lug lugs and to remove residuals at other local curvature radii.
After processing through the above steps, the machining simulation results of the hook forging die are shown in Fig. 4.
3. 2 electrode processing of the key mode of the copier panel
The electrode model of the button model cavity is shown in Fig. 5. The blank's boundary dimension is 100 mm × 85 mm × 35 mm. The upper and lower planes and the surrounding contours have been finished. The processing depth range is 0 to -15 mm. Now it is necessary to complete the positioning hole and the entire cavity processing in the machining center. The generated processing steps are as follows
(1) Roughing is divided into two steps according to depth
Using the WCU T-CONTOUR ROU GH process, a flat-bottomed cutter with a Ø10 mm diameter is used. The machining depth ranges from 0 to -15mm. The blank allowance around the key cluster is removed in the form of a STOCK SPIRAL pass.
Using the WCU T-CONTOUR ROU GH process, use a flat-bottom cutter with a Ø4 mm diameter. The machining depth range is the same as above. Select WITH STOCK to remove the blank allowance between keys that was not removed in the previous process.
(2) Semi-finishing
Due to the more uniform blanks after roughing, WCU T-CONTOUR FINISH can be used for semi-finishing directly, with a ø4 mm ball-end cutter. Interlayer processing parameters selection BETWEEN LAYERS: HORIZ, PARALL EL CU T, using automatic sub-area processing, the electrode side using contour processing, the upper and lower surfaces using surface horizontal cutting for finishing. The machined surface selects all model faces, SRF OFFSET = 0, and the electrode surface cuts to the model size.
(3) Finishing
In order to supplement the discharge gap, different electrode surfaces need to be cut. With the WCU T-CONTOUR FINISH procedure, the tool is still a 4 mm diameter ball nose cutter. By setting different colors on the sides and upper surfaces of the electrodes on the model, and then using the BY CRITERIA option during the process to define the part plane, select the sides of all the electrodes as PART SRF and the upper and lower surfaces as PART 2 SRF . Then set the SRF OFFSET = - 0.15, PART2 SRF. OFST = - 0. 08, so that the electrode surface to form a different over-cut. Processing parameters selection BETWEENLAYERS: HORIZ, PARALL EL CU T. The contour finishing tool path on the side of the electrode is shown in Fig. 6, and the parallel cutting path on the top surface of the electrode is shown in Fig. 7.
After all the above steps are completed, the electrode's machining simulation results are shown in Figure 8.
In the above two cases, Cimatron basically adopted the machining strategy for cavity mold parts and achieved very good results in actual processing. At the same time, it is also not difficult to find from the above cases that only according to the characteristics of specific processing objects, appropriate adjustments are made to individual processes in the processing strategy, and appropriate parameters are set, so that processing can be both efficient and quality-guaranteed.
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