Starting from the actual production situation, this article is intended to solve the processing of titanium alloy small-diameter precision castings on the five coordinates of the new equipment, to ensure the high-precision deformation control of the box parts, to improve the qualification rate of the technical conditions of the processed parts, to improve the processing efficiency, and to reduce the production cycle. Problems, bearing housings, front bearing casings, and the front section of the inner ring of the rear cover / rear assembly belong to this type of casing parts. According to the structural characteristics and technical requirements of each part, it mainly analyzes and experimentally studies the process route, processing method, numerical control program, cutting parameters, etc., and formulates a reasonable process route. It also elaborated on the problems encountered in the processing and the measures taken.
With the continuous improvement of aeroengine design performance, the design accuracy of the casing is getting higher and higher, the design structure of the casing is becoming more complicated, and the use of difficult-to-machine materials, which gives the casing how to control deformation during processing and how to ensure Machining precision and shortening the manufacturing cycle have brought great difficulty. Especially for the processing of more complicated type casings, the control of the amount of deformation is the key to the improvement of casing manufacturing technology. Judging from the current production and processing of casing parts, it is difficult to control the amount of deformation during machining of high-precision casing parts. The deformation during processing, as well as the deformation after the test run and flight test, will affect the quality and assembly interchangeability requirements of the casing, and solve the deformation of high-precision casing parts and improve the qualification rate of the processing is an urgent problem.
2. Project Overview
- Task source
- Technical index
1. Machining on the five-coordinates of the new equipment, cooperate with the five-coordinates machining center to complete the CNC process;
2. Combine processing procedures to improve production efficiency;
3. Improve parts quality
2.3 Research content
- Bearing seat:
1. Explore the technology and procedures suitable for the five-axis CNC machining equipment, and verify.
2. Test the new process route of the bearing seat parts, and control the qualified rate of the technical conditions of the parts to 100%
- Back cover:
1. Completing the process and program compilation and verification of five-axis numerical control processing equipment, and studying the processing technology of titanium alloy small-diameter precision castings.
2. The milling process is highly concentrated in the five-axis machining center to improve the efficiency of parts processing.
3 Research and implementation
3.1 Bearing seat
Bearing seat is the main component, the material is titanium alloy, casting, the maximum diameter is Φ600, the total height is 180.5mm, and the wall thickness is 4.5mm. Bolt holes, threaded holes and pin holes are distributed on the front and rear surfaces of the parts; mounting seats and pin holes are distributed on the radial direction.
- Five-axis numerical control processing equipment is used to merge milling processes.
By adjusting the process route of the parts, the contents that can be processed in the same placement position are merged and processed together. A total of 1.5h of correction time is saved, 3 correction times are saved, 4 parts turnover is saved, and the average processing cycle is 16 days.
- Adjust the process route to control the pass rate of the technical conditions of the parts to 100%.
In the original process specification, when the inner hole of the finish car Φ200 was adjusted, the correcting of all sides was guaranteed to ensure the final technical conditions. The actual part alignment state could not meet the requirements of the drawings, and the technical conditions after processing were out of tolerance.
- Reason Analysis of Out-of-tolerance
The mounting edge of the part is a cantilever beam structure. After the finishing process, there are still many drilling and milling processes. The end face and the stop of the part are deformed by force. In the final finishing Φ200 inner hole, the technical conditions such as A, B, and L are related. Deformation of the reference surface, resulting in out-of-size technical conditions in the free state after machining
- Improvement measures
Supplied with auxiliary support drilling fixture to reduce the force deformation of the mounting edge when drilling.
Adjusting the processing content of the process: leave the relevant dimensions of each technical condition with a margin of 0.1-0.2mm on one side, and clamp the processing at one time in the Φ200 inner hole process of the precision car to ensure that each technical condition is qualified.
- Improvement effect: The four technical conditions of the improved parts are 100% qualified.
3.2 Rear cover
The material is a precision casting of titanium alloy, with a maximum diameter of Φ500, a minimum diameter of Φ45, and a total height of 150mm. The casting structure of the parts is complex, and the difference between the large and small ends is large; there are two vent pipes and one oil pipe, the big end has threaded holes and laces, the small end has threads, and the inner hole is coated.
- Using five-coordinate CNC machining equipment, combined milling process
Through the adjustment of the part process route, the content of part milling is highly concentrated and merged into the five-coordinate CNC processing equipment.
- Optimize the milling plan, improve the surface quality of the L-shaped groove, and meet the requirements of the drawings.
- Improvement measures
Using the new equipment of the five-axis machining center, using the five-axis linkage milling method, using the Φ20R3 alloy milling cutter, without the use of tool extension rods, the milling cutter has high strength.
4. Work summary
The work has achieved benefits. Through this research, a large amount of equipment turnaround time has been saved, the time for correcting the work has been reduced by 4.5 hours, and the labor intensity of the workers has been reduced.
5. Experience, problems
- The titanium alloy small-diameter parts have been successfully tested in the five-axis machining center, which can realize the multi-process combination and completion, and have a guiding role in the preparation of the process route of the new types of family parts.
5.2 Main problems
- 1. With reference to the design concept of the accompanying fixture, please make a small-diameter part quick-change tooling universal base and positioning fixture. The quick-change flip plate is not manufactured and cannot be processed for verification.
- 2. At present, there is only one five-coordinate machining center. If all the small-diameter parts are milled and processed by this machine tool, the equipment capacity will be insufficient to meet the production needs.
In this research, the parts have completed the process verification of the five-coordinate machining center. Although there are some deficiencies in the process, the benefits have been seen from the aspects of part quality, processing efficiency, cycle, production schedule of the section, and labor intensity of workers. The evaluation of the key problem was successful. At the same time, it also pointed out the direction of the process route compilation of the subsequent family parts, and opened up a new path for the tooling system of small-diameter parts.