This article introduces the structural characteristics and CNC machining ideas of complex parts through the case of complex parts produced by our company, as well as the CAXA/CAM processing method adopted in the machining center of the case. The complex part features, processes, and other aspects are described and carried out.
The processing of the real object is used to verify its accuracy and reliability. We will describe the features and technology of the complex parts, and perform physical processing to verify their accuracy and reliability.
As shown in Figure 1, it is a relatively complex part machined by our company in mold processing.
The blank size is 158mm long, 128mm wide, and 35mm high. The material is 45 steel, which has comprehensive processing elements such as internal contour, curved convex and concave platform, complex curve surface, curve groove, thread, inner hole, and gear.
Its CAXA manufacturing engineering processing method has certain representatives. The software has high programming accuracy and is easy to master. It can generate G codes for CNC systems commonly used in the world, has a wealth of roughing and finishing commands, and also has communication functions.
Figure 1 Three-dimensional diagram of parts
1. Complex Parts Structural Characteristics
As shown in Figure 2, the upper end of the front complex part has a curved surface composed of R50mm and 2 R4mm, and the boundary of the surface has a circular chamfering of R5mm, the center complex part has a curved surface composed of R20mm and 4 R5mm, and the complex part has 4 R3mm chamfering. These structural elements make the modeling and processing difficult to some extent.
Figure 2 CNC Machined Complex Parts Diagram
The gear parameters for the front center are: Modulus/m=4, Number of teeth/ z=9, Addendum coefficient/ha=1，Gear tip clearance/C=0.25, Addendum modification coefficient/X=0.4, Spanned tooth count/K=2， Common normal/Wn=19.5+0.2 +0.1 (mm).
CAXA does not provide professional gear modeling commands, which can be modeled by function curves, but this method is more complicated to shape with displacement coefficient.
The size of the curved groove at the lower end of the front surface of the complex part is not easy to guarantee. The two 90° gaps are not closed, and the auxiliary line is closed to be programmed and processed.
There are two ellipses in different directions on the inner contour edge of the back, inner and outer hexagonal petals composed of arcs in the center, and two arc-curved islands on the top and bottom. These elements are rounded in processing, so it is more convenient to choose a reasonable shape.
2. Complex Parts CNC Machining Process Analysis
Using CAXA manufacturing engineering to process complex parts, there is no need to draw complete parts for reprocessing, the first such downtime is long, a waste of processing time; Second, in the selection of local processing, there will be interference between the elements of the complex parts, but it is not convenient to program track.
When machining plane contour elements, the software can only draw contour lines of complex parts for rough and finished machining. Surface machining can be programmed by solid or surface machining. Surface must be used in local processing, and some finishing commands can only be selected by surface machining.
The roughing command can not only realize roughing but also be used as a finishing command.
The finishing command can use the trajectory translation to form multiple levels, and the connected trajectory becomes a whole roughing command; Roughing command can turn a layer of machining track into a finishing command by setting the layer height.
“CAXA manufacturing Engineer” plane contour elements, can use plane area roughing and contour finishing to complete the rough finishing parts, and can also use contour finishing to do rough processing. Surface roughing can be done by contour roughing or by two finishing commands: parametric line finishing and 3d offset surface.
Due to the high dimensional accuracy in the figure, it was decided to use rough machining, semi-finishing, and finishing to achieve dimensional accuracy.
Semi-finishing machining and finishing machining using the same tool and cutting parameters, which can correct all kinds of geometric errors and parts of the elastic deformation. It is easy to ensure the size, the important undersurface also needs to finish machining.
The complex parts are processed by the FANUC NC machining center. All tool tracks are generated in FANUC post-format. The transmission is carried out using CAXA’s communication function and transmitted according to FANUC Settings; The subsequent machining programming ends without the tool path.
3. Complex Parts CNC Machining Process
①Machining the outer contour of the front: Clamp the two sides of 150mm with a machine vise, expose 30mm of the vise surface, shim the bottom surface, mill the top surface with a face milling cutter, and process the surroundings with an end mill.
As shown in Figure 3, black is the blank wireframe, blue is the contour curve of the complex part, brown is the tool track, pink is the tool feed track, and red is the tool retreat track.
Figure 1 shows that the shape is a plane contour graph, according to the complex parts clamping position draw parts contour line, using φ 18mm machine clamping end milling cutter, because the tool diameter exceeds the complex parts unilateral margin, so in the X-Y plane without layered processing.
Figure 3 Machining outer contour track
Using the contour finishing command, set the depth machining range of -28 ~ 0mm in the layer high, and screw feeding between layers to keep the machining smooth. Force cutting outside the blank, leave 1mm for finishing allowance, rotate speed 2 000r/min, cut 1.5mm vertically, feed speed 600mm/min, and generate trajectory as shown in Figure 3.
Semi-finishing machining, complex parts finishing machining using the same command and tool, semi-finishing machining in the margin of the parameters set as 0.5mm, speed 2 400r/min, knife depth is Z 5mm, feed speed 300mm/min. For finishing, adjust the margin parameters according to the actual size of the inspection, and use the same cutting parameters for processing forming.
②Machining the gap on both sides of the front: Open the CAXA interface and draw a notch graphic according to the part clamping. Because the rough machining command of the plane area is used, there must be a closed contour line. To not leave any residual material at the three right-angle sides, the two right-angle sides must be translated out of one. A closed contour can be formed after the tool radius to generate a tool path.
Roughing parameter setting, using φ 18mm machine clamp end milling cutter, from the outside to the inside ring cutting processing. The height is set to the depth machining range of -15 ~ 0mm, and the cutting parameters are the same as above. The tool tracks of another notch are generated by mirroring, and the two tracks are connected to realize one machining, as shown in Figure 4.
Figure 4 Process the contour track of the notch on both sides
Semi-finishing and finishing use contour finishing commands, same as above.
③Machining 30 ° bevel and R50mm surface: Solid modeling is used in the processing, and then the solid surface is converted to a curved surface for processing through the solid surface command, or it can be directly made into a curved surface for complex parts processing. Use two processes roughing and finishing.
The 30° inclined plane is roughed and finished by using the parameter line command. The parameter line is the finishing command and cannot be processed by layers. So with the curved side milling method, in the Z-direction cutting amount can reach 1 ~ 1.5 times the tool diameter, in the X-Y direction that the row distance cutting amount of 0.1 ~ 0.5mm, without layering can be rough processing.
In rough machining, a speed of 2 000r/min, feed speed of 1 000mm/min, row spacing of 0.3mm, and margin of 0.5mm are set to complete rough machining. Use the same command and parameter settings for finishing. The tool is an R5mm ball-end milling cutter, with a speed of 3 600r/min, a feed speed of 1500 mm/min, a line spacing of 0.3 mm, and a margin of 0 mm. The inclined surface finishing of the complex part is completed. The tool path is shown in figure 5.
R50mm curved surface uses three-dimensional offset surface finishing commands for roughing and finishing. After roughing, the non-layered tool path can be translated up to five layers, and a complete path is formed through the path connection, but there are more empty tools.
Therefore, by increasing the feed speed in the cutting parameters, adjusting the feed rate switch of the machine tool to quickly go through the empty tool, and adjusting the normal speed when cutting.
Set the parameters of 3d offset surface processing command in rough machining, φ 18mm machine clamp end milling cutter, rotational speed 2 000r/min, feed speed 4 000mm/min, row spacing 1.5mm, layer 1.5mm, leave margin 0.5mm, complete rough machining.
Finishing uses the same command and parameter Settings. Due to the restriction of R3mm inner arc in the parts, the tool selected R2mm ball milling cutter, rotation speed 4 500r/min, feed speed 2 000mm/min, row spacing 0.3mm, margin 0mm, finish R50mm, tool path as shown in Figure 5.
Figure 5 Machining R50mm curved surface and 30° inclined plane trajectory diagram
④Machining a recessed table with a width of 94mm on the front side: Using wireframe modeling, the gear is first milled into a φ 47mm circle, and the narrowest complex part of the recess is 13mm, plus allowances on both sides, only φ10mm tools can be used for complex parts machining. Rough machining uses plane area command, ring cutting is from inside to outside, machining height is -15～0mm, layer height is 0.5mm, row spacing is 5mm, the cutting method selects spiral radius 2mm, pitch 0.5mm, cutting parameter is 3 000r /min, the feed rate is 2 000mm/min, and the tool path is shown in Figure 6.
Figure 6 roughing track
Semi-finishing and finishing use contour finishing commands. Because the bottom surface of the concave table has a low dimensional accuracy, no bottom finishing is performed. The processing parameters are processing height -15～0mm, layer height 2mm, vertical cutting mode selection, rotation speed 4 000r/min, and feed speed 450mm/min. The dimensional tolerance guarantee method is the same as above, and the trajectory is shown in Figure 7.
Figure 7 Finishing track
⑤Gear machining: Draw the graph with the gear command in CAXA electronic chart, be sure to decompose and save it in its format, and start the same version of “Manufacturing Engineer”.
Select the file to be merged into the file. Rough machining using contour finishing command, processing parameters set due to the restriction of tooth shape, the tool using carbide φ 4mm end milling cutter, processing height of -10 ~ 0mm, the height of 0.1mm, row spacing 2mm, deviation mode is left, layer between the knife spiral, the number of cuts is 2, remaining margin 0.8mm, under the knife spiral, The cutting parameters are rotational speed of 5 000r/min and feed speed of 2 000mm/min. The resulting tool trajectory is shown in Figure 8.
Figure 8 Gear roughing trajectory diagram
Semi-finishing, finishing also adopts contour finishing command, cutting tool φ 4mm carbide end milling cutter, the parameter setting is processing height -10 ~ 0mm, layer 1.5mm, cutter times is 1, under the cutting mode choose vertical, cutting parameters for speed 5 000r/min, feed speed 500mm/min, dimension tolerance guarantee method is the same as above, the trajectory is shown in Figure 9.
Figure 9 gear finishing trajectory diagram
⑥Center surface processing: Use local modeling to stretch a cylinder to create a curved surface, which is convenient for local selection processing. For roughing, select the equal height roughing command, use φ 6mm cemented carbide end mill, set the parameters of layer height 1mm, line spacing 1mm, and select the inner side of the machining boundary. In addition to approach and return, all connection parameters can be directly connected.
Cutting parameters can refer to the previous settings. The trajectory is shown in Figure 10. Complex machined parts finish machining using 3d offset surface command, the use of R2mm ball milling cutter, parameter setting line spacing 0.3mm, select and machining boundary coincidence, cutting parameters can refer to the previous Settings. The trajectory is shown in Figure 11.
Figure 10 Center curved surface roughing trajectory
Figure 11 Center curved surface finishing trajectory
⑦Front curve groove machining: In CAXA, the curve groove is drawn according to the graphic position. To make the tool cut outside the complex part entity and leave no residual material when the tool is processed, the 5.5mm straight line is extended by a tool radius. The groove processing uses a shaped keyway milling cutter to ensure accuracy.
Rough machining using contour finishing command, using φ 8mm carbide milling cutter, residual 1mm, using a small tool 0.3mm processing, and the parameter settings as above. Complex machined parts finish machining also uses the contour finishing command. For parameter setting, refer to the above. Use φ 10mm carbide keyway milling cutter with the same slot width to process and form, as shown in Figure 12.
Figure 12 Curved groove machining trajectory
⑧Back concave processing: Using wireframe modeling, the rounded corners on both sides of the hexagonal petals are modeled with curved surfaces, and only one curved shape is created by the two long waist-shaped bosses.
During roughing and finishing, since the depth of the inner hole in this complex part is 15mm and the depth of the large concave table is 5mm, the regional roughing and contour finishing commands are used separately, and then a complete roughing and finishing tool path is formed through the path connection.
Due to the restriction of the inner arc, the φ12mm carbide end mill is used as the roughing and finishing tool, and the parameter setting is the same as above. Due to the 5mm concave table depth dimension accuracy being high, it is necessary to finish machining the bottom surface, using the area roughing command to process only one layer of tool track bottom surface. Concave contour roughing and finishing show are shown in Figure 9, the gear finishing trajectory is shown in Figure 13 and Figure 14, respectively, and the bottom surface finishing is shown in Figure 15.
Figure 13 Concave contour roughing track
Figure 14 concave contour finishing track
Figure 15 Concave contour roughing track
The curved surface in the recessed table is a circular arc chamfer, with a small machining allowance. Using parameter line finishing as roughing, finishing command, roughing using φ 8mm alloy end milling cutter, step set to 1mm, finishing using R2mm alloy ball milling cutter, step set to 0.3mm, to reduce the finishing allowance. Because finishing tools are limited by complex parts, only smaller diameter tools can be used, the rest of the parameters refer to the previous. Roughing and finishing of chamfering surface are shown in Figure 16 and Figure 17.
Figure 16 Roughing track of the chamfering surface
Figure 17 Finishing track of the chamfering surface
⑨The thread in the complex part can be processed by the hole processing commanded by the automatic programming command or the fixed cycle processing to realize the automatic tapping of the bottom hole. The inner hole of φ 6mm can be reamed by the automatic programming drill, and the inner hole of the larger diameter φ 16mm can be drilled, milling, and bored to complete the processing, it will not be described here.
Through the above methods, the CNC machined parts completely meet the accuracy requirements. In the processing to the flexible use of CAXA manufacturing engineers in a variety of modeling and processing functions, you can use the curve without entity, surface, and entity preference modeling conveniently. To reasonably select machining commands, the simpler the trajectory is, the better.
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