When titanium alloys encounter thin-walled parts, it is seemingly double the difficulty to process 2mm thin-walled materials on recognized hard-to-machine materials, but after specific analysis, there are still corresponding solutions:

PART01 thin-walled cavity analysis of titanium alloy

1.1 Part Size Analysis

The minimum rectangular contour size of the envelope cover part is 567mm × 426mm × 56.5mm. The overall appearance is a large arc surface and thin wall cavity structure. The wall thickness of the arc surface cavity is 2mm, and the thickness of the connecting shoulders at both ends is 6mm. In order to ensure the tightness of the cover plate and the box after installation, the flatness of the cover plate mounting surface is required to be 0.1 mm.

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

1.2 Analysis of processing technology

The main processing part of the cover plate part is the cavity. The difficulty is to solve the chattering problem of the cover plate part during the processing due to the thin-walled structural characteristics. The overall structure is simple. The flatness and surface quality of the cover and the mounting surface of the box have high requirements. The dimensional accuracy and surface quality of the remaining parts are not high. All the processing steps can be completed on the CNC machining center.

Here, 570mmx430mmx60mm rough sheet is selected. Titanium alloy thin-wall cavity cover parts need to be processed in three steps: ① rough milling and finishing milling of the cavity; ② rough milling of the concave cavity; ③ precision mounting surface machining.

PART02 Processing technology and tooling scheme design

2.1 Rough milling, fine milling and mounting hole machining of convex cavity

The dimensions of the cover parts are 567mm ± 0.1mm × 426m ± 0.1mm × 57mm, and the surface roughness of all machined surfaces is Ra3.2Um. Leave 0.5mm machining allowance in the thickness direction, and process 4 M16 deep 40 Threaded holes are used as fixing holes for the processing of convex cavities. The four threaded holes are based on the symmetrical center point of the large plane. "One side, two pins" positioning method, using screw clamping method to achieve positioning and clamping.

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

Secondly, the convex cavity of the cover plate part and the step surfaces on both sides are installed. The rough machining of the convex cavity and the rough finishing of the mounting step surfaces on both sides select a four-blade end mill with a high cobalt content. The parallel milling surface roughing method is shown in Figure 2. During the cutting process, high-speed tool steel tools must maintain sufficient cutting fluid to extend the tool's service life.

Then, for the convex cavity finishing, a polycrystalline cubic boron nitride ball nose milling cutter is used. The streamlined surface finishing method is shown in Figure 3, and the overall error is controlled within 0.012mm. Finally, the 16 mounting holes (all of which are threaded connection holes) on the mounting surface are processed. Directly drilling with a 0.5mm hard alloy drill bit can meet the processing requirements. After the end of this process, burrs should be removed, the sharp edges should be dull, and the surface of the convex cavity should be polished without 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 and difficult processing problems?

Finishing Simulation of Convex Cavity

2.2 Cavity rough and fine milling and milling tooling

Figure 4 shows a milling tool for rough and fine milling of a concave cavity. The concave curved surface processed by the tooling fixed on the workbench in the previous step is matched with the convex cavity of the cover plate part, and the two sides of the tooling are matched with the mounting step surfaces at both ends of the cover plate part to achieve accurate positioning. The concave surface of the tooling and the plane, where the plane intersects with the plane, should be cleared to avoid burrs or sharp edges that affect positioning accuracy. Then use 10 M10 threaded holes on both sides of the tooling to complete the clamping and fixing of the cover plate parts and the tooling.

The roughing method of the concave cavity of the cover plate is selected by the method of grooving. The tools, cutting fluid and cutting parameters are basically the same as those of the convex cavity. The four M16 clamping holes in the previous procedure are prone to vibration and damage to the tool during the milling process, which requires attention during cutting. The tool is the same as the milling parameters and the finishing of the pocket.

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

Note that during processing:

① A natural failure treatment must be arranged between the roughing and finishing of the concave part of the cover plate to completely release the internal stress generated by the cutting process and prevent machining deformation;

② During the finishing process, the mating surfaces of the cover parts and the tooling should be changed several times before and after, and the black grinding marks on all the mating surfaces in the tooling should be repeatedly repaired to ensure that there is no obvious gap between the positioned cover part and the tooling mating surface;

③Remove the cuttings at the corners and the mating surfaces of the clean tooling to avoid crushing the cover parts and affecting the surface quality; ④When tightening the screws on both sides, you should alternately rotate the screws left and right to avoid the clamping force. Deformation.

2.3 Finished mounting surface

After inspection and processing of the mounting surface, the main causes of the flatness and surface roughness are mainly caused by tool marks or processing deformation, which requires refinishing the mounting surface.

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

Both the positioning datum and the clamping and fixing surface should select the parallel mounting step surfaces on both sides of the cover part. First, select the machining method of fine milling, then select the machining method of fine grinding, finally select the machining method of grinding, and continuously check during the machining process. . In the machining process of the convex cavity, a machining allowance of less than 0.5mm is reserved to meet the accuracy requirements. Cover parts that have passed inspection after processing.

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

Titanium alloy TC4 is a difficult-to-machine material, and the cover parts belong to the structure of thin walls and cavities. The same tooling is used in the actual numerical control processing, which can be consistent with the overall process of the cover parts in the design; Clamping positioning can also cleverly overcome the 2mm thin-wall machining chatter, avoid excessive clamping force and prevent deformation and other problems. In processing practice, reasonable use of tooling can reduce costs, facilitate operation, and save time and efficiency.