1. Analysis of processing difficulties
There are a batch of production tasks from an optical machine. This task is a new challenge in terms of processing materials and processing accuracy. Among them, the processing of the convex lens rotation axis has the following problems:
- The rotating shaft of the convex lens is made of titanium alloy. Due to its high strength and high hardness, it is easy to produce a surface hardened layer during processing, and the material has a small thermal conductivity and a small elastic modulus, and the springback of the processed surface during cutting is large , Causing violent friction, adhesion and bond wear on the flank of the tool.
- While ensuring the shape processing accuracy, the coaxiality of the two ends of the part is required to be 0.006mm, which is almost difficult for the existing machine tools to achieve. Since the existing machine tool starts, its own spindle jump is> 0.01mm, and it is difficult to complete the processing tasks on such a machine tool.
- The requirements for the shape of the parts and the dimensional accuracy of the holes are very high, respectively 0.005mm and 0.01mm, and the surface roughness value Ra = 0.8μm is required. Under normal circumstances, to achieve this pattern requires processing on the grinding machine to complete. Because there is no grinding machine equipment for precision processing in the branch, this task must be completed by a lathe.
Before processing, the pattern was carefully studied, various processing schemes were analyzed, and finally the following method was decided to process.
Second, the choice of process parameters
According to the characteristics of titanium alloy materials, the tool materials with high strength performance, good wear resistance and YW series brand are preferred for processing.
- Tool parameters: select a positive and negative external eccentric cutter and a lateral groove turning tool with a main declination angle of 90 °. While ensuring the cutting strength of the tool, in order to reduce the cutting resistance and prevent the material from overheating and deforming during the cutting process, the larger rake angle of the tool is selected to be 20-25 °. In order to avoid sharp friction and adhesion of the tool flank with the surface of the part during the cutting process, the tool back angle is selected to be 5-8 °.
- Cutting parameters: Due to the low thermal conductivity and small elastic modulus of titanium alloy materials, bonding is easy to occur during processing, so the cutting parameter value is not easy to set too large during processing, and the spindle speed is selected from 350 to 500r / min high. Choose a larger amount of back-feeding knife and feed volume for rough turning, and a smaller one for finishing turning.
2. Processing technology
- Rough turning: First use a horizontal groove turning tool to rough turn the two ends of the part, leaving a margin of 0.5mm on one side. Due to the small resistance and easy chip breaking during the cutting process of the transverse groove turning tool, the use of the transverse groove cutter has a good effect on the rough turning of both ends. However, because the titanium alloy material is easily deformed by heat during processing, the cutting fluid must be used for sufficient cooling during the cutting process.
- Semi-precision turning: After the part is completely cooled, use a 90 ° external eccentric knife to pull out the reference outer circle of the part, clamp the shape of the part through the soft claw, and correct the shape of the part using the micrometer lever meter to make the circle run out to 0.005 Within one millimeter, the parts are processed at one end, and cannot be processed in place at one time, leaving a margin of 0.1 to 0.2 mm on one side.
3. Fine car:
- After the shape of the part is cut off, drill and boring to ensure the size and accuracy requirements. Correct the shape of the parts again to ensure that the dimensional accuracy is within 0.005mm, and the precision car shape has a margin of 0.05mm. Because the double top is based on the internal holes at both ends as the positioning reference, and the shape margin of the part before the final finishing is small (0.05mm), drilling and boring and the finishing shape are completed in the middle of one clamping and the hole is made. Chamfer to prepare for the next double top process.
- Put a center point on the machine tool, pass the parts through the double top method, use the positive and negative deflectors to finish the shape of the two ends, polish the shape of the parts, and reach the requirement of surface roughness value Ra = 0.8μm.