1 INTRODUCTION While designing and manufacturing complex cutters such as sprocket hobs by conventional methods, the hob's normal tooth shape is known, but due to the lack of a straightforward method for accurately solving the hob axial tooth profile, the hob is used for machining. Tools such as lathe tool and shovel cutter are complex in design, cumbersome in calculation, error-prone, large in machining allowance and unevenly distributed. The tooth profile accuracy of machined hobs is not easy to meet the design requirements. The trial cut method is required to perform the hob tooth profile. Corrected. Although at present China has developed some complex tool CAD/CAM systems. However, there are not many real applications in production practice. According to the current state of technology of domestic enterprises, it is fully possible to use the existing computer three-dimensional modeling technology and wire cutting processing technology to achieve the design and manufacture of hob machining tools. In this paper, a new tool design and manufacturing method is proposed. It uses a modern 3D solid modeling technology to design a three-dimensional solid model of the tool. The hob's normal tooth profile is directly converted into an axial tooth profile on the model. The principle of machining is to determine the cutting line of the tool line on the model, and then the tool blade profile is directly machined. 2 Hob normal tooth form and tool processing The sprocket hob is used as an example. The normal tooth profile of the hob (see Fig. 1) should be the same as that of the rack tooth common to the sprocket. Theoretically, when the pitch and roller diameter of the sprocket are the same and the number of teeth is different, the tooth profile of the sprocket is different, that is, the tooth profile of the rack co-twisted with the sprocket is also different, so different hobs are required. Processing, which will greatly increase the specifications of the sprocket hob, also brings inconvenience to the manufacture and management of the sprocket hob. Therefore, in China, the method of using a fixed sprocket reference rack tooth profile in actual production is to specify a sprocket tooth profile with a certain pitch and a certain roller diameter as a sprocket reference rack tooth profile. When a sprocket with the same pitch and diameter of the roller and different number of teeth is machined with a hob having such a reference tooth profile, although a certain error will occur, the amount of error is not large, and when the accuracy of the sprocket is not high enough, The method has a certain feasibility.
Figure 1. 38.10 x 22.23 sprocket hob normal tooth profile The sprocket reference rack tooth profile reflected on the sprocket hob is the normal tooth profile of the hob. Checking the design manual shows that according to the pitch t and the outer diameter d of the roller, the sprocket hob has 10 specifications. Corresponding to this, the normal tooth profile of the sprocket hob is only 10 kinds, each hob The specific dimensions of the normal tooth profile have also been determined. Fig. 2 is a schematic diagram of wire cutting processing of a tool for machining a sprocket hob. Fig. 2a shows the use of sine gauge fixtures to clamp the tool body at a certain front and rear angle. The tool wire cutting trajectory is the projection of the hob axial tooth profile on the vertical surface of the tool flank (the horizontal surface in the drawing); Fig. 2b shows The flank face of the tool is processed by the key wire inclination method, and the hob axial tooth profile can be directly used as the wire cutting machining track.
3 tool three-dimensional modeling and line cutting process trajectory determination
(a)
(b) Figure 2 Cutting line diagram of the tool line In the past, we mainly used AutoCAD and other software to carry out three-dimensional design of the product. Now we can use modern three-dimensional modeling and processing software (such as Solid Edge, Solid Works, UG, Pro/E, etc.) Product modeling operation. Taking Solid Edge software as an example, the three-dimensional solid modeling of the sprocket reel hob blade (applicable to the processing method in Fig. 2a) is performed. As a new generation of 3D CAD software, Solid Edge has powerful 3D design capabilities, including building surfaces, related part families (rotation, scanning, lofting, spirals, etc.), cutouts, fillers, hole features, shells, fillets, and arrays Wait. Using Solid Edge's parameter- and feature-based design techniques, an entity can be created by drawing the contour of a workpiece, and then a three-dimensional entity can be formed by projecting, scanning, staking out, and rotating the entity. The principle of modeling design first establishes a basic body of a tool model. The basic body should contain the axial plane of the tool, the flank, and the plane perpendicular to the flank that can reflect the wire cutting trajectory, and place it at the bottom of the model. For an auxiliary surface, the angle between it and the axial plane is equal to the helix angle on the hob dividing circle, this auxiliary surface is the normal plane of the hob (see Figure 3); on the hob normal plane According to the hob method, sketch the specific structure dimensions of the tooth profile, and then cut the tooth profile of the rack on the basic body of the tool model perpendicular to the sketch plane. The intersection line of this rack tooth profile with the axial plane is the hob axis. To the tooth shape; The axial tooth profile is projected to the bottom of the basic body of the tool model to obtain the tool line cutting process trajectory. By this projection as a sketch, the basic body of the tool model is cut, and the final three-dimensional shape of the tool can be obtained. Specific steps Open Solid Edge, create a new part file, click on the “stretch” feature icon and select the reference plane 2 in the drawing window. Determine the shape, size, and pull direction of the tool extension profile according to the design principle shown in Figure 3. After stretching height, click "Finish" to create a basic tool shape.
Fig. 3 Three-dimensional design framework of a car blade for machining sprocket cutters
Fig. 4 Conversion of normal tooth profile and axial tooth profile
Figure 5 three-dimensional modeling tool
Make an auxiliary reference plane 4 with an angle of lf from the upper axial plane of the basic body of the tool modeling. Click the “Sketch” icon to make a hob normal tooth profile sketch 1 on the plane 4, and determine the hob normal direction on the sketch 1. The center position of the teeth and the positioning reference. And mark the size of each part; click the “Sketch” icon again to make the hob normal tooth sketch 2 on the plane 4, draw the hob normal tooth profile on the sketch 2 and mark the dimensions (the dimensions of the sketches are The “Intricate Tool Design Manual (Volume 2)” published by the Machinery Industry Bureau of Sichuan Province (published by Machinery Industry Press, 1979) is clearly regulated on page 779). Click the "Division" icon, select the sketch of the normal tooth profile 2 by selecting the outline from the sketch, and then select the "All through" method and the through direction, and click "Finish" to form the basic body of the original tool. Cut out the sprocket reference rack (see Fig. 4). The axial profile of the tool body is the axial tooth profile of the tool. Click on the "Sketch" icon to make a sketch on the axial plane. 3 When you enter the outline state of the sketch, click on the "Include" icon to copy the axial tooth profile of the tool onto the axial plane; then click on the "Feature Pathfinder". "Suppression" of the reference rack tooth removal operation in step c. Draw sketch 4 with the bottom plane of the tool as the drawing plane. After entering the contour state of the sketch, copy the axial tooth profile of the tool to the drawing plane by “Include”; then click the “Division” icon to sketch 4 To outline the sketch, determine the direction of material removal, and use the “full penetration” removal method to remove the material, a three-dimensional model of the blade of a machine tool chain sprocket reel can be finally completed (see Figure 5); the finished model can be saved. Use Solid Edge's drawing module to create a new drawing (.dft file), and transfer the three-dimensional modeling of the finished tool from the file; when selecting the direction of the part's main view, only the cutting line of the tool line can be expressed. Without the other isometric view of the part, after confirming the view scale, the view conversion of the part can be completed automatically in the figure, and the wire cutting path of the tool can be drawn. The drawing is saved in a format acceptable to the wire cutting system and input to the wire cutting system. Before the wire cutting of the cutting edge of the cutting tool, the dimensions of other parts of the cutting tool should be pre-machined. The cutting tool should be heat-treated according to the design requirements and the surface on the cutting tool should be ground, and then the cutting body should be clamped. After selecting the machine tool to process the origin and picking up the wire cutting trajectory, the tool edge shape can be wire-cut, and the tool front corner can be cut after the machining is completed. When the specification of the processed sprocket hob changes, only the corresponding dimensions of the three-dimensional modeling of the tool can be modified according to the specific structure size of the tool, and the design technology based on parameters and characteristics can make Solid Edge accurately and conveniently. Redesigned the three-dimensional shape of the tool. 4 Conclusion Using the above Solid Edge 3D modeling design method, we have designed a 3D modeling model of multiple sprocket hob machining tools, and successfully processed a sprocket hob machining tool based on the obtained tool line cutting trajectory. Good practical application effect. Using Solid Edge 3D solid modeling technology to accurately solve the sprocket hob processing tool profile and tool line cutting process trajectory in the design, manufacture of other complex tools also has important reference value. With the continuous development of three-dimensional parametric design technology and CAD/CAM integration technology, the design and manufacture of complex tools will become faster and easier, and the production efficiency will continue to increase.
