In the process of titanium alloy flange milling, it is necessary to overcome the problems of easy deformation of parts, high dimensional accuracy, low processing efficiency, and high cost of tool consumption. The material characteristics of the similar parts began to describe the key points of the tool selection, the design of the tool path and the parameter selection process in the process of the part, and how to improve the processing efficiency of the titanium alloy parts, reduce the deformation and reduce the possibility of out of tolerance According to the milling method, a preliminary study on the control method of cutting load during the machining process was carried out.
Keywords: titanium alloy; flange; easy to deform; processing efficiency; cutting load
1 Introduction of parts structure and processing requirements
This article discusses the flange milling process. Typical parts have a set of positioning surfaces on both sides. The front end is connected to the engine fairing and the rear end is connected to the engine fan disk. The holes and laces are used to fix and reduce weight. The following are the milling process requirements. The structure of the flange is complicated. Because most of the structures have a special role, the dimensional accuracy is high and the parts are difficult to process. Due to the large machining allowance of this type of parts, it is necessary to ensure that the deformation of the parts before and after processing is effectively controlled during the processing, and the surface quality requirements of the parts are relatively strict, so the processing process is more complicated. This makes the processing method of the part have a big difference from the traditional processing method. In addition to the stricter aperture requirements, the milling process of the part also needs to ensure effective control of the machining deformation during the removal of large margins. The angular relationship between the groups of holes in the part is complex, and the positional requirements are high. There is a strict positional relationship with lace, and special processes such as shot blasting are required after processing. The above characteristics must be internally controlled during processing to meet the impact of subsequent special processes, which brings difficulties to the processing of parts.
2 Material cutting performance and tool selection
- Introduction of material properties
This part uses DMD0777 material equivalent to domestic TC4 alloy. Compared with other metal materials, titanium alloy has the characteristics of small specific gravity, high thermal strength, good thermal stability and corrosion resistance, but at the same time titanium alloy material also has hardness or high temperature The characteristics of high hardness, high work hardening, poor thermal conductivity, high cutting temperature, easy bonding with tools, and large chemical activity make these titanium alloys a difficult machining material with poor machinability.
- Selection of cutting tools
The choice of cutting tools needs to pay attention to several main aspects:
- (1) From the perspective of tool geometry, the tool rake angle can usually be larger to reduce the friction between the flank face and the workpiece surface. The rake angle should also be selected to make the tool sharper, enhance the strength of the tool head, and reduce Small processing deformation, reduce work hardening, and improve the quality of the processed surface.
- (2) Considering the strength of the tool tip, heat dissipation capacity, wear resistance, surface quality and processing efficiency, the radius of the tool tip at the end of the milling cutter can be appropriately increased while ensuring the rigidity of the clamping and tool system, which allows In the case of surface quality, the thickness of the chip is reduced, thereby improving the feed, and the strength of the blade tip, the heat dissipation ability, and the wear resistance are strengthened.
- Selection criteria for cutting amount of titanium alloy
The amount of titanium alloy cutting is close to that of high-temperature alloys and some aerospace stainless steel materials. Both should be from the point of view of reducing cutting temperature, because controlling cutting heat is the primary means of protecting tools. When cutting titanium alloys, the surface roughness has nothing to do with the cutting linear velocity, and the influence of the cutting depth is also very small, so the feed rate can be adjusted appropriately according to the shape and size of the tool and the arc structure of the end edge when considering the processing efficiency. Through the thickness and width of the chip to control the state of force in the cutting process of the tool to achieve the purpose of processing. The cutting load should also be considered in the process of selecting the cutting amount. The primary method of reducing the cutting load is to reduce the cutting force. The brisk cutting is helpful to reduce the stress during the processing of the part and thus reduce the deformation of the part. There are several ways to reduce the cutting load. First, you can choose a small depth of cut and a large feed method. This method is more common in the cutting process using the end edge. Because this method is easy to evacuate chips, it is convenient to cool, and the tool is under load. It is lower, so it can achieve a greater material removal rate while achieving the processing goal. Secondly, you can choose a small cutting width and a large feed method. In order to reduce the load on the tool, you can also achieve the same purpose. When both methods can be applied, it is preferred to use the end edge for processing, because the force direction of the tool is more It is biased towards the axial direction of the tool and has strong rigidity. When the end edge is worn and cannot be used, milling with the side edge can effectively use various positions of the tool, which is helpful to reduce tool consumption. In the processing of this part, these two methods have been applied to achieve a balance between processing efficiency and tool cost.
3 The design and processing of the tool path for milling of this part
3.1 General principles of tool path design
The lace structure needs to be removed with a large margin, and it is difficult to process and control the process. The design of the tool path has a great influence on the processing of parts. In the milling process of this part, several problems of tool path design were overcome. First of all, in order to obtain a large material removal rate, it is necessary to have as much feed as possible during the application of the tool. During the application of large feed, the problem of changing the cutting load at the corner must be avoided. On the other hand, the cutting parameters should be adjusted at the smaller corners by cutting parameters, that is, the arc cut-in method and the corner speed-down method should be applied. The tool trajectory design process must consider each machining action in the machining process and effectively control the cutting load at all times in order to effectively exert the tool performance and at the same time help to reduce tool wear. During the milling process, the titanium alloy is always used along the milling mode, because of material performance reasons, the tool wear is large during the reverse milling, and the surface quality of the part is poor.
3.2 Main points of processing
The process of processing needs to be carried out in strict accordance with the operating regulations. In order to meet the needs of batch production of parts and the stability of quality, many aspects need to be paid attention to during the process, including:
- (1) The clamping length of the tool needs to be strictly regulated, because in the process of extremely efficient material removal, parts and tool vibration problems are often involved. Although the resonance can be avoided by adjusting the parameters, in order to pursue cost reduction, it should be Select the optimal processing conditions.
- (2) The durability of the tool needs to be tested and counted, because surface problems such as work hardening often occur during the processing of titanium alloy parts. This problem is often caused by the backlog of the tool or the chips entering the cutting area, so the blunt tool cannot be used and must be used. Clearly specify the number of parts processed by each tool.
- (3) During the finishing process, a new blade must be used and the blade is not allowed to be replaced midway during the finishing process, to avoid the unstable effect of the blade size and sharpness on the quality of the parts.
- (4) For solid carbide cutting tools, it is necessary to check whether the cutting tools are sharp before machining, and tools with severe wear are not allowed to be used.
- (5) The tool yaw must be checked during the installation of the finishing tool. When the tool yaw value exceeds 0.02, some characteristics will be out of tolerance.
Due to the reasonable and effective design of this part processing process, the stable removal process and the mastery of the operation steps, the high efficiency, high quality and low consumption of the part processing process have been achieved, and the design drawings and related documents are finally guaranteed through the development of this part Requirements, successfully completed the flange milling technology research of this model.