Abstract: starting from the actual production situation, this paper aims to solve the problems of processing titanium alloy small-diameter precision castings on the five coordinates of the new equipment, ensure the deformation control of high-precision gearbox parts, improve the first pass rate of technical conditions of processed parts, improve processing efficiency and reduce production cycle, bearing seat, front bearing gearbox The front section of the inner ring of the rear cover / rear cover assembly belongs to this type of gearbox parts. According to the structural characteristics and technical requirements of each part, the analysis and experimental research are mainly carried out from the aspects of process route, machining method, NC program and cutting parameters, and a reasonable process route is formulated. The problems encountered in processing and the measures taken are described in detail.

　　Keywords: process integration; Five coordinates

　　1. Introduction

　　With the continuous improvement of Aeroengine Design performance, the design accuracy of the gearbox is getting higher and higher, and the design structure of the gearbox is becoming more and more complex. In addition, the use of difficult machining materials has brought great difficulties to how to control the deformation of the gearbox in machining, how to ensure the machining accuracy and shorten the manufacturing cycle, especially the machining of the gearbox with more complex profile, The control of its deformation is the key to the improvement of gearbox manufacturing technology. From the current production and processing of gearbox parts, it is difficult to control the deformation of high-precision gearbox parts in processing. The deformation during machining and after test run and flight test will affect the quality of gearbox and the requirements of assembly interchangeability. It is urgent to solve the deformation of high-precision gearbox parts and improve the first pass rate of machining

　　2. Project overview

　　2.1 task source

　　Branch level research

　　2.2 technical indicators

　　1. Process on the five coordinates of the new equipment and cooperate with the five coordinates machining center to complete the NC process;

　　2. Combine processing procedures to improve production efficiency;

　　3. Improve the quality of parts

　　2.3 research content

　　2.3.1 bearing pedestal:

　　1. Explore and verify the process and program suitable for five coordinate NC machining equipment.

　　2. ? Check the new process route of bearing pedestal parts and control the qualified rate of technical conditions of parts to 100%

　　2.3.2 rear cover:

　　1. Complete the process and program preparation and verification suitable for five coordinate NC machining equipment, and study the machining technology of titanium alloy small-diameter precision castings.

　　2. Concentrate the milling height to the five coordinate machining center to improve the machining efficiency of parts.

　　3. Implementation of tackling key problems

　　3.1 bearing pedestal

　　The bearing seat is the main component, which is made of titanium alloy, casting and maximum diameter Φ 600, total height 180.5mm, wall thickness 4.5mm. Bolt holes, threaded holes and pin holes are distributed on the front and rear end faces of the parts; Mounting seats and pin holes are distributed radially.

　　3.1.1 use five coordinate NC machining equipment to combine milling processes.

　　By adjusting the process route of parts, the contents that can be processed in the same placement position can be combined for processing. In total, 1.5h alignment time, 3 alignment times and 4 parts turnover are saved, and the average processing cycle is 16 days.

　　3.1.2 adjust the process route to control the qualified rate of technical conditions of parts at 100%.

　　Finish turning in the original process specification Φ The final technical conditions are ensured by the runout of each surface during the alignment of the 200 inner hole. The alignment state of the actual parts can not meet the drawing requirements, and the technical conditions are seriously out of tolerance after processing.

　　3.1.3 cause analysis of out of tolerance

　　The mounting edge of the part is a cantilever beam structure. After the finishing machining process, there are still many drilling and milling processes. The end face and stop of the part are stressed and deformed, and they will be finished in the final finishing machining process Φ The datum planes related to technical conditions such as a, B and L are deformed during 200 inner hole, resulting in the out of tolerance of technical conditions in free state after machining

　　3.1.4 improvement measures

　　Assign drilling fixture with auxiliary support to reduce the stress and deformation of installation edge during drilling.

　　Adjust the processing content of the process: leave 0.1-0.2mm allowance on one side of the relevant dimensions of each technical condition before finishing Φ 200 inner hole process is clamped and processed at one time to ensure that all technical conditions are qualified.

　　3.1.5 improvement effect: the four technical conditions of the improved parts are 100% qualified.

　　3.2 rear cover

　　Precision castings made of titanium alloy, maximum diameter Φ 500, minimum diameter Φ 45, overall height 150mm. The casting structure of parts is complex, and the difference between large and small ends is large; There are two vent pipes and one oil pipe. The big end is provided with threaded holes and lace, the small end is provided with threads, and the inner hole is coated.

　　3.2.1 use five coordinate NC machining equipment to combine milling processes

　　By adjusting the process route of parts, the milling contents of parts are highly concentrated and merged into five coordinate NC machining equipment

　　3.2.2 optimize the milling scheme, improve the surface quality of l-groove and meet the drawing requirements.

　　3.2.3 improvement measures

　　The new equipment of five coordinate machining center is used, and the five axis linkage milling mode is adopted Φ 20r3 alloy milling cutter does not need to use tool extension rod, and the milling cutter has high strength.

　　4. Work summary

　　The work has achieved benefits. Through this breakthrough, a lot of waiting time for equipment turnover has been saved, the alignment time has been reduced by 4.5H, and the labor intensity of workers has been reduced.

　　5. Experience and problems

　　5.1 experience

　　1. The test of titanium alloy small-diameter parts in five coordinate machining center is successful, which can realize the combination of multiple processes, and plays a guiding role in the preparation of the process route of subsequent new family parts

　　5.2 main problems

　　1. Referring to the design concept of accompanying fixture, please make the general base and positioning fixture of quick change tooling for small-diameter parts. The quick change turntable has not been manufactured back and cannot be processed for verification.

　　2. At present, there is only one five coordinate machining center. If all small-diameter parts are milled by this machine tool, the equipment capacity will be insufficient to meet the production demand.

　　6. Conclusion

　　In this breakthrough, the parts have completed the process verification suitable for the five coordinate machining center. Although there are some deficiencies in the process, we have seen benefits from the aspects of part quality, processing efficiency, cycle, section scheduling, labor intensity and so on. The overall evaluation is that the breakthrough is successful. At the same time, it also points out the direction for the preparation of the process route of subsequent family parts, A new way has been opened up for the allocation of tooling for small diameter parts.