1 Introduction The indexable car broach has the advantages of high processing efficiency, good processing quality, long tool life, convenient tool change and adjustment, and is currently the first choice of advanced tool for crankshaft rough machining. The car broach used in the automotive industry in China has long relied on imports. Due to the high price, the processing cost of the crankshaft has been greatly increased. In order to realize the localization of indexable broaches, many domestic companies have developed broaching products in recent years. However, due to the complex structure of the broaching tools, high technical content, difficulty in manufacturing, and processing conditions and processing Accuracy requirements are strict (need to be processed on high-precision five-axis CNC machine tools), and most of them are manually programmed by the operator, resulting in a long tool manufacturing cycle, the processing accuracy is not easy to guarantee, and the reject rate is high. Our company utilizes SUN graphics workstation and I-deas software of SDRC company in the United States, combined with Ingersoll's MAX-I type indexable tool design theory introduced from Germany, and successfully solved the indexable car broach with CAD/CAM technology. The design and manufacturing problems have better ensured the product quality and processing efficiency of home-made indexable cart broaches. 2 Car broach design The complete car broach is assembled from a plurality of fan-shaped car knife blocks on a drum. The following takes a fan-shaped pull block as an example to introduce the CAD/CAM method of the puller. For the crankshaft machining allowance is large (about 4 ~ 5mm), shaft diameter and sidewall width tolerance requirements are strict (rough processing +0.1mm, finishing + 0.04mm) and the cutting efficiency and surface roughness requirements are high, etc. The main points of structural design of the knife are as follows: Adopt the German Ingersoll MAX-I type vertical milling cutter structure. The blades of the broach puller are arranged in a tangential direction. The blade is fastened with a single screw and clamped by a cutting force. The tool structure blade is convenient and rapid in indexing, and has fewer tool accessories, which can increase the space for chipping and the number of effective cutting teeth. Compared to the plain blade structure, the stand blade structure can increase the area of ​​the blade to withstand the cutting force, that is, increase the ability of the cutting edge to withstand the cutting load, thereby enabling efficient cutting with large feed and large depth of cut. The front end of the fan knife block adopts a replaceable module structure. The blade at the front end of the broach puller has the largest cutting force and impact load, so the blade and the cutter body at this position are most susceptible to bluntness, chipping and breakage. A replaceable module structure is used at the front end of the broach to quickly replace the blade or the cutter body when it is damaged, thereby shortening the tool change cycle and effectively protecting other blades and the cutter body from large load shocks. With this structure, tool life can be extended, production cost can be saved, and good machining accuracy can be ensured. The blades are arranged in tooth increments. The blade is arranged in a tooth-lifting manner to realize the layered cutting of the crankshaft, thereby effectively reducing the cutting resistance, reducing the bending phenomenon during the machining of the crankshaft, and improving the machining quality and the cutting efficiency. The blades in the circumferential direction are arranged in unequal pitches, and a set of blades of the same size is shifted by one phase angle, so that the cutting vibration can be reduced and the cutting stability can be increased. Uses reasonable geometric angles and high dimensional accuracy requirements. 3 Car broach CAD step According to the crankshaft processing diagram provided by the user, draw a line drawing of the lamination of the broach as shown in FIG. 1 , and determine the distance between each layer (ie, the amount of tooth lift) and the diameter of each layer accordingly. Dimensions and axial width dimensions. The first five sets of inserts are used for roughing, and the larger tooth lift is used; the latter five inserts are used to ensure the accuracy of the crankshaft and the smaller tooth lift is used.
Figure 1 Lathe knife layered cutting line chart
Using a broach delaminated cutting line pattern as a reference, a linear segmentation is performed, and a cemented carbide blade arrangement lapping map is drawn (see FIG. 1). According to the lap chart of the blade, the diameter of the broach, and the size of the broach, the number of effective cutting teeth of the broach is determined, and the circumferential distribution is performed within the sector segment, and then a set of cutting teeth at the front end of the broach is changed to faster. Change the module. The amount of misalignment of each blade is calculated to form a drop value. The formula is x=0.5{Wb+C[D2/(Wb2 + C2)-1]1â„2} where: Wb—blade width C on axial section—fall angle D—the diameter of the circle where the insert is located. The diameter of each set of blades varies in size. Therefore, the dislocation values ​​of each set of cutting teeth must be individually calculated. Then each set of blades is turned to the desired position on the sector surface of the puller block, and the unequal pitch arrangement is performed. Rotate the same set of two blades of the same diameter by one phase angle. Each blade is rotated about its end face side edge, creating a side edge relief angle a. The chip space is determined based on the blade position. Due to the large number of teeth on the broach block and the relatively small chip space, the crumb space should be designed to increase the swarf space as much as possible, and to open the swarf to a smooth angle. Determine the installation structure, dimensions and dimensional accuracy of the broach. The broach structure designed according to the above CAD step is shown in FIG. 2 .
Figure 2 The design structure of the broach
Fig. 3 Flowchart of programming for indexable broach
4 Car broaching CAM step According to the determined structural scheme and design sketch, solid modeling is performed using I-deas entity software. According to the solid modeling, the three-dimensional structure shape of the processed finished broach can be visually previewed, and the dimensions, angles, and related assembly and processing interferences of the broach can be detected through the software's measurement function so as to verify in time. Modify and adjust the previous design plan and generate 2D plane design drawings. Secondary modeling, generating processing model units. Each blade and its flutes, empty knives, screws, etc., are made into a single unit. Taking into account the fact that there are enough feeds, retracting spaces, and the starting point of the feed and the up/down milling in the actual machining, the relevant surface and other reference surfaces in the independent unit are properly selected as the reference for the trajectory, boundary and direction of the tool processing. Then use the object-append command to generate individual processing model units. Enter the NC-SETUP module to generate the job file jobfile. Use the surface-set command to select and determine the machining surfaces and reference planes of the individual elements in the quadratic geometry model, and generate a GNC format job file xxx.JB. Determine the processing technology. Due to the large diameter of the broach (Ø851mm), this tool has exceeded the machining range of existing machine tools. Therefore, a non-standard tooling must be designed to clamp it on the workbench. The double-side teeth of the broaching tool must be secondary. Clipping and positioning. The unilateral machining process of the broaching tool is determined as: milling cutter → roughing insert pocket → machining flutes → semi-finishing insert pocket → machining screw center hole → drilling screw hole → tapping → fine milling insert groove. According to the process design requirements to select the processing machine, the preparation of the process specification (choose cutting tool cutting amount, machining allowance, processing route, etc.), and the selected tool and cutting amount written in the job file xxx.JB in GNC format. Prepare the processing program Sequence. Enter the GNC module and import the job file xxx.JB. Program according to the established processing route and GNC programming commands. When programming, you need to consider the factors such as the direction of cutting, reverse milling, and the forward/reverse rotation of the cutting tool. Commonly used programming commands are Partsurf/, Guv/, Multaxis/, Taxis/, Goto/ and so on. Generate the location file xxx.CL. After the Sequence machining program is completed, the entire machining process can be simulated and demonstrated. After determining the processing route, the path of the pass, the direction of the pass, and so on, use the Finish command to end the job and create a tool location file xxx.CL. Post-processing. Select the dedicated post-processing program for the machine tool to post-process the tool location file xxx.CL and generate a machining program xxx.TP that can be recognized by the machine as a G-code type. Then according to the practical experience in the numerical control processing, the processing program xxx.TP is edited and arranged again to shorten the idle travel time and distance, and adjust the speed of the knife. Trial processing. The edited machining program is input to the machine for the first trial machining to check whether the machining results meet the design requirements. If the machining error is caused by factors such as the accuracy of the machine tool in the actual machining, the positioning of the secondary fixture, and is easy to adjust, it can be adjusted directly by the operator of the CNC machine tool. Otherwise, it is necessary to return to the GNC's Sequence to make adjustments and corrections, and perform a secondary test until the machining result is correct. The programming procedure for the indexable broach is shown in Figure 3. 5 Conclusion The application of CAD/CAM technology has significantly improved the design and manufacturing precision and production efficiency of the indexable vehicle broach, shortened the tool production cycle and reduced the scrap rate. The production and application of several domestic users such as the Beijing Jeep car factory proved that our company's indexable car broach has excellent performance and can replace similar foreign products.
Engine Mountings
Engine Mountings,Engine Left Rear,Engine Mounting Front,Engine Right Rear Outrigger
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