Economical CNC lathe machining special-shaped spiral groove thread

May 29, 2022

The physical map shown in Figure 1 is an outsourced product processed by a factory in the internship teaching of our hospital. The name is the conveying screw shaft, which is a component of the material transported on a machine. The material is cast aluminum alloy. As a whole, it is a taper thread, and it is a left-handed thread, and the shape of the spiral groove is relatively complicated. The length of the spiral portion is 550 mm, the rigidity during processing is poor, and the amount of the snack knife is required to be low. The spiral groove structure is composed of three arcs. It is composed of a straight line segment and belongs to the special-shaped thread type, which cannot be processed on ordinary machine tools. Moreover, there is no thread machining code that can be directly quoted on the CNC lathe, so the difficulty lies in the programming of the program and the selection of the tool.

Processing program analysis

The programming idea of CNC machining lies in the accurate description of the contour of the part. Therefore, the focus of this thread programming is how to accurately describe the shape of the spiral groove. Because there is no thread machining code that can be directly quoted, the G32 code is used for macro programming. (The R4mm arc is used as an example) to machine the part. as shown in picture 2.

It can be seen from Fig. 2 that the coordinates of the points on the R4mm arc are changed. How do you calculate them? Suppose we give the starting point A of a thread, then we can get the coordinate B of the center of R4mm (which can be considered as fixed). By analogy, the center coordinates C and D of R5mm and R25mm can be obtained. The drawing calculates the starting angle corresponding to R4mm, and uses the circle equation to calculate the coordinates of any point on the arc. For example, A point #3=COS[#1] *4 (#1 start angle, #3 represents X value), convert the circular coordinate system into the workpiece coordinate system. For example #3=COS[#1] *8+94.688 (diameter at the center of R4mm); A point Z value #2=SIN[#1]*4, after conversion #2=SIN[#1] *4-593.575 (R4mm center coordinates in the Z direction). The above is the coordinate calculation of the R4mm arc at the starting point, and then the corresponding end point coordinates are calculated, and the start point and the end point are connected by the G32 command. Then complete the R4mm macro programming, the program is as follows:

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For more information, please download the attachment or view Metalworking (Cold Processing), Issue 23, 2013:

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