When titanium alloy meets thin-wall parts, it seems to be twice as difficult to process 2mm thin-wall from the recognized difficult material. However, after specific analysis, there can be corresponding solutions:

Analysis of thin wall Cavity parts of PART01 titanium alloy

1.1 Part size analysis

The minimum rectangular contour size of the envelope cover plate parts is 567mmx426mmx56.5mm. The overall appearance is a large circular arc surface thin-wall cavity structure, the wall thickness of the arc surface cavity is 2mm, and the thickness of the connecting shoulder at both ends is 6mm. In order to ensure the sealing between the cover plate and the box after installation, the flatness of the installation surface of the cover plate parts is required to be 0.1mm.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

1.2 Processing technology analysis

The key processing part of cover plate parts is the cavity, the difficulty is to solve the flutter problem of cover plate parts due to the structure characteristics of thin wall in the process of processing. The overall structure is simple, the cover plate and the box installation surface has higher flatness and surface quality requirements, the rest of the size accuracy and surface quality requirements are not high, all processing procedures can be selected in the CNC machining center to complete.

Here we choose 570mmx430mmx60mm blank plate, titanium alloy thin-wall cavity cover plate parts processing need to carry out three processing steps: (1) convex cavity coarse milling, fine milling, namely mounting hole processing; ② Concave cavity rough finishing milling; (3) Finishing of installation surface.

PART02 Processing technology and tooling design

2.1 Convex cavity rough milling, fine milling and mounting hole processing

The outer dimension of the processing cover plate parts is 567mm±0.1mmx426m±0.1mmx57mm, to ensure that the surface roughness of all the processing surfaces is RA3.2um, and the processing allowance of 0.5mm is left in the thickness direction, and four THREADED holes of M16 deep 40 are processed on the large plane as the fixed hole of the convex cavity processing process. The four threaded holes are based on the symmetrical center point of the large plane, and the positioning size is corresponding to the fixed hole of the aluminum-magnesium alloy 6061 tooling fixed on the workbench, so that the cover plate parts adopt the positioning mode of "one side and two pins", and the positioning and clamping method is realized by screw clamping.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

Secondly, the convex cavity of the cover plate parts and the mounting step surface on both sides are processed. Four-edge end milling cutter with high cobalt content was selected for rough machining of convex cavity and coarse and finishing machining of step surface mounted on both sides. Roughing method of parallel milling surface was selected as shown in FIG. 2. In the cutting process, the high speed tool steel tool must keep sufficient cutting fluid to prolong the service life of the tool.

Then, polycrystalline cubic boron nitrite ball milling cutter was selected for convex cavity finishing. The streamline surface finishing method was selected as shown in Figure 3, and the overall error was controlled within 0.012mm. Finally, the 16 mounting holes on the mounting surface (all belong to threaded connection holes) can be directly drilled with a 0.5mm carbide drill to meet the processing requirements. After the end of this process, burrs should be removed, sharp edges blunt, convex cavity surface polishing treatment, no obvious knife marks, so as not to affect the positioning and clamping of the next process.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

Parts convex cavity finishing simulation

2.2 Cavity rough and fine milling and milling tooling

Figure 4 shows the milling tool for coarse and fine milling of concave cavity. The fixture fixed on the workbench in the previous process is processed into a concave surface and the convex cavity of the cover plate parts, and the two sides of the fixture and the mounting step surface of the cover plate parts at both ends are matched to achieve accurate positioning. The concave surface and plane, plane and plane intersection place for root cleaning, avoid burr or sharp edge affect the positioning accuracy. Then 10 M10 threaded holes on both sides of the tooling are used to complete the clamping and fixing of cover plate parts and tooling.

The cutting tool, cutting fluid and cutting parameters of the concave cavity of the cover plate are basically the same as those of the convex cavity. The 4 M16 clamping holes in the previous procedure are easy to cause vibration and damage to the tool during milling, so attention should be paid in cutting. Cutter and milling parameters and convex cavity finish the same.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

In processing, attention should be paid to:

(1) A natural failure treatment must be arranged in the middle of rough machining and finishing machining of the concave cavity of the cover plate parts, to completely release the internal stress generated by cutting and prevent machining deformation;

(2) When finishing clamping, the matching surface of cover plate parts and tooling should be replaced repeatedly, and the black grinding marks on all the matching surface of tooling should be repaired repeatedly, so as to ensure that there can be no obvious gap between the cover plate parts and the matching surface of tooling after positioning;

(3) Clean the chip in the cleaning root and corner and on the mating surface to avoid crushing the cover plate parts and affecting the surface quality; (4) When locking the screws on both sides, it should be alternately twisted symmetrically to avoid deformation caused by clamping force.

2.3 Finishing mounting surface

After detection and processing of the installation surface, the main reason for the out-of-tolerance of flatness and surface roughness is knife marks or processing deformation and other factors, which requires re-finishing the installation surface.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

The parallel installation step surface on both sides of cover plate parts should be selected for positioning datum and clamping fixed surface. First, the processing method of fine milling should be selected, then the processing method of fine grinding should be selected, and finally the processing method of grinding should be selected, and constantly detected in the processing process. The machining allowance of 0.5mm is reserved in the convex cavity processing procedure to achieve the accuracy requirements. Cover plate parts that have been inspected after processing.

Titanium alloy + thin-walled workpiece, how to solve the difficult processing problem?

Titanium alloy TC4 belongs to the difficult to process material, cover plate parts belong to the structure of thin wall and cavity, the actual NC machining using the same tooling, in the design can be consistent with the overall process of cover plate parts; Technically, it not only solves the clamping location, but also skillfully overcomes the vibration and chatter of 2mm thin-wall machining, and avoids the problems of excessive clamping force and deformation. In machining practice, reasonable use of tooling can reduce cost, convenient operation, time-saving and high efficiency.