Precision male screw shaft layering experiment

By adopting the above shaft lamination processing method and cutting the left and right processing blades respectively, the left and right threaded surfaces are formed. We designed two different finish turning technology schemes according to the process design method and conducted a comparative experiment of large pitch male thread finish cutting. Preparation of test piece for large pitch screw finishing experiment, the material of the test piece is 35Cr Mo quenching and tempering. The structure is right-handed trapezoidal male screw, number of heads 1, thread length 160 mm, large diameter 120 mm, diameter 104 mm, median diameter 112 mm, pitch 16 [mm], half of teeth The angle is 15 ° and the width of the thread groove is 6.33 mm.

Two tools have been designed, polished and turned to turn the left and right threaded surfaces of a 16 mm pitch trapezoidal male thread.

The utility model uses a replaceable cutter head spring type cutter, which is made of high-speed steel (W18Cr4V) and can be attached to and disassembled into the cutter body.

The part where the two tools are involved in cutting consists of the upper edge and the left and right cutting edges.

• Pre: Base surface,
• Pse0: Cutting surface of the main cutting edge,
• Pse1: Cut surface of left cutting edge,
• Pse2: Cutting surface of right cutting edge,
• W0: Length of upper cutting edge,
• θ: The angle between the left and right cutting edges,
• λs: Blade tilt angle,
• γ00: The most advanced rake angle.
• γ01: rake angle of left cutting edge, γ02: rake angle of right cutting edge,
• α00: The back angle of the upper cutting edge.
• α01: Left corner of the cutting edge,
• α02: Back angle of the right cutting edge,
• εr1: Cutting edge angle of the left cutting edge,
• εr1: is the right cutting edge angle.

When using the above two tools on a CA6140 lathe, the rotation speed n is 10 r / min, which matches the cutting depth of the tool with the depth of the thread groove of the workpiece. The screw test piece is machined by rotating the tool left and right and cutting the cutting edge layer by layer along one side of the shaft. Until the error of the machined surface roughness and screw diameter of the left and right threads is controlled below the specified machining quality index.

Thread axial laminated cutting test result

In the above experiment, the pitch error data curves of the left and right thread surfaces of the thread are obtained, as shown in Figure 4.

The fluctuation range of the pitch error on the left surface is -0.019 to 0.019 mm. The fluctuation range of the pitch error on the right side is -0.017 to 0.019 mm. The pitch error of the left edge cutting is larger than the pitch error of the right edge cutting, and the right side is denser than the left side. Above all, the surface pitch error on the right side is better than the surface on the left side, both ranging from -0.02 to 0.02 mm.

Meet the processing requirements.

The pitch error range for the left curved surface is -0.009 9 to 0.01 mm. For right curved surfaces, the pitch error range is -0.01 to 0.01 mm. The pitch error of the left edge cutting is larger than the pitch error of the right edge cutting, and the left side is denser than the right side. Among them, the surface pitch error on the right side is better than that on the left side, both ranging from -0.02 to 0.02 mm, which meets the processing requirements. To quantitatively analyze the strengths and weaknesses of the left and right machining accuracy of the two solutions, the size order is 10-4 mm. To quantitatively analyze the accuracy on both sides of the screw, the size order is 10-4 mm.

Results of correlation analysis of pitch error of left and right thread planes:

Solution 1: The pitch error between the left and right threaded surfaces of the threaded test piece is 0.8632. Solution 2: Test thread surface for pitch error of left and right threads related to a degree of 0.6217. Therefore, it can be seen that the thread surface distribution consistency of the second scheme is superior to that of the first scheme. Figure 6 shows the machined surface topography of the left and right thread surfaces of the experimentally obtained thread.

Roughness parameter curves are processed and analyzed to quantitatively analyze the strengths and weaknesses of the left and right roughness parameters across the thread. The results are shown in Table 5.

Table 5 Roughness Ra parameter value analysis

As can be seen from Table 5, the fluctuation range, average value, and standard deviation of the three roughness index values ​​of the large pitch male screw of the second method are relatively small.

This indicates that the large pitch male thread of the second scheme has a small thread surface roughness value, a relatively uniform distribution along the entire thread surface, and good consistency. From the comparison of the two process schemes above, we can see that the processing count of the second scheme is much higher than that of the first scheme, but the processing effect is superior to that of scheme 1. Therefore, it can be explained that the cutting efficiency of the design goal is inconsistent with other goals. To ensure that other goals meet your requirements, simply specify reasonable design parameters. When other objectives meet the technical requirements and reach the highest value, select with reasonable cutting efficiency in mind

From the above analysis, it can be seen that the topography of the machined surface of a workpiece with the same large pitch of male threads varies greatly depending on the process design variables due to the difference in design variables. This difference can result in deviations in movement and force transmission. Under different process design conditions, the quality of machined surfaces is quite different, and the consistency and distribution characteristics of threaded surfaces are very different. Therefore, controlling process design variables and optimizing the process scheme suitable for large-pitch thread cutting are essential for high-precision, high-quality large-pitch threading.

Conclusion

• (1) Research on the contact relationship of large-pitch male threading machines and the parameters of the cutting layer by axial stratification. Eighteen parameters were determined as process design variables, such as the geometric angle of the tool, cutting parameters, and the number of cuts on the left and right blades. The results of the main process design variable analysis show that the front and rear cutting edges are designed to have a front angle of 0 °. Due to the effect of the right helix angle, the left edge is cut at the positive front angle, the right edge is cut at the negative front angle, and the thread angle has the opposite effect on the working dorsal horn of the left and right cutting edges. .. The left and right cutting edges use the same process design variables to cut large pitch male threads, and the process of forming the left and right thread surfaces is clearly different.
• (2) Due to the cutting efficiency and the consistency of the surface of the left and right threaded surfaces, a design method for an axially laminated cutting process with large pitch male threads has been proposed. This method adjusts the back angle of the left and right blades of the tool, the number of times the left and right thread surfaces are machined, and the permissible value for one cutting. The processing quality of threads is effectively improved under the condition of ensuring efficiency.
• (3) Two different cutting process schemes were designed and proposed according to the design method. To determine the final process design, we conducted a comparative experiment of axial delamination cutting precision machining of large pitch male threads. In this scheme, the left edge was rotated 16 times and the right edge was rotated 10 times. The front angle of the tool is 0 °, the rear angle of the left blade is 8 ° 52′, and the rear angle of the right blade is 5 ° 58′. Experimental results show that the design method can significantly improve the pitch error, surface roughness, and corresponding large pitch screw distribution. To meet the machining requirements for high pitch threads, this method can be used in the design of axially laminated large pitch thread finishes.