Deep hole drilling and boring of titanium alloy

Titanium alloy pipe Tc6, pipe diameter Φ40, length 575, this deep hole drilling technique, the first deep hole drilling technique of titanium alloy material, we are in contact. The deep hole resembles a typical long axis type part, especially the hollow structure of the deep hole, the partial opening size of which is Φ40. It does not match the company’s deep hole drilling equipment (T2120 deep hole drilling and boring machine). Since the outer diameter of the support handle of the original machine tool is Φ38, the total length of the part being machined must be 750-1500 mm. Under existing conditions, it is not possible to meet the deep drilling requirements for pipe diameters. Deep hole drilling technology made of titanium alloy has become an important technology to be solved in the development of parts.
As shown in Figure 1.
Titanium deep hole processing

Part structure in Figure 1
1. Analysis of difficulty of processing technology
The technical difficulty is deep hole drilling for thin-walled parts. And difficult to handle titanium alloy material: TC6 has an aspect ratio to meet the equipment requirements to the deep hole length specified in 1170mm (2 part length) processed in this process. Is 1170: 38, surface roughness Ra0.5. The structural design of the shank of a special deep hole drilling machine is very difficult to select and manufacture, resulting in very difficult machined parts. At the same time, existing equipment must meet the conformance requirements of the newly designed shank. To this end, we have undertaken special work related to deep hole drilling for thin-walled titanium alloy shaft parts.
T2120 deep hole drill
2. Formulate specific measures
2.1 Determine the processing plan
We will take up the deep machining of titanium alloys as a research theme, develop new dies, design sealing structures, reconstruct deep hole drilling equipment and other technical challenges. It was decided to use the company’s existing deep hole equipment to improve this processing solution, and the T2120 deep hole drilling machine developed deep hole drilling and titanium alloy tubing.
Specific improvement measures are as follows.
Reconfigure the positioning system structure of the machine handle.
Design and component matching positioning sealing structure;
Deep hole drilling, tool material research
The size of the tool structure has been developed to meet the design requirements of the tool handle. At the same time, basic research is needed when designing the mandrel, such as the tip removal function of the inner hole of the mandrel.
To this end, we design and manufacture nine types of special deep hole cutters, boring heads, shanks and other equipment accessories.
Numerous machining tests have been carried out to ensure the smooth development of deep hole drilling and machining of titanium alloy tubing. After testing, it will meet your production and development needs and solve the important problems of deep hole drilling technology for titanium alloy pipes.
First, we combined the deep hole structure of the titanium alloy pipe with the existing equipment to develop a specific process route and formulate the process specifications.
The processing route for titanium alloy pipes is as follows.
Roughing Criteria –Deep Hole Drilling –Extension Holes –Reaming –Finishing Cylinder Test.

Deep hole drill

2.2 Special touring design
2.2.1 Special deep hole tool design.
Due to the determination of the deep hole drilling equipment (deep hole drilling and boring machine T2120), the design of the mandrel must be consistent with the machine cutting and sealing system.
Since the inner diameter of the deep hole of the titanium alloy tube is φ40, there is a limit to the design structure of the inner and outer diameters of the mandrel. On the one hand, the outer diameter of the shank must not be too large, reducing the inflow of high pressure oil during deep hole drilling. The resulting pressure is inadequate and affects the insert removal function of deep hole drilling. Arbors tend to get clogged with chips. On the other hand, when designing a mandrel, the maximum inner diameter of the mandrel must also be considered. The inner and outer diameters of the shank must match to ensure the robustness and reliability of the rectangular threads at the joints of the shank, and the shank has sufficient rigidity. At the same time, it fulfills the chip removal function of the deep hole processing device (T2120 deep hole drilling machine) to ensure that the chips are smoothly discharged into the waste box along the inner hole of the arbor under the action of high pressure oil. There is a need.

2.2.2 Tool design.
Specially designed special deep hole drilling, deep hole reamer, adapter, deep hole reamer, matching reamer seat.
2.3 Design of positioning sealing structure connected to machine tool and parts, i.e. selected design Sealing transition adapter sleeve structure provides sealing function of the contact surface between parts and machine tools for smooth joint transition Resolve and form a closed space for parts and tools. In deep hole drilling, a closed high pressure circulation system is formed that prevents high pressure oil leakage and realizes cooling, chip discharge, and lubrication during deep hole drilling.

3. Example of processing technology for deep holes in titanium tubes
In deep hole drilling of titanium alloy tubes, conventional deep hole drilling methods are still used during machining. Our production base is changed by the use of equipment, special deep hole arbor and matching tools, deep hole drilling, specific processing steps are divided into three steps: Lehman-Reaming, processing test,
As shown in Figure 2
Deep hole drilling, reaming, deep hole Lehmang
Figure 2 Deep hole drilling, reaming, deep hole Lehmang
After the processing test, on the deep hole surface of the first titanium alloy tube, the diameter of the inner hole was locally poor, the surface roughness was poor, and groove marks were generated on the surface of the inner hole.
As a result of the analysis, it was found that the size of the transition joint of the floating reamer is the upper limit and the cutting force at the tip of the reamer is not uniform. Then, the production of floating blades moves, and the diameter of the inner hole exceeds the requirement of the drawing. Further, the groove mark is present in the inner hole because the wall is thin, the hole is deep, and a vibrating knife or a pressure blade is likely to be generated during drilling.
In addition, reamers can cause the above problems after wear.

Gradually improve the structure of the tool and develop improvement methods in response to the causes of these problems. To ensure reamer reamanging after self-centering, the actual size of the reamer and the centering effect of the floating reamer tip are increased before machining. Check tool wear and replace with new tools in a timely manner. This ensures deep hole drilling dimensions for subsequent machining. Completed the first deep hole drilling and development of titanium alloy tubing. In the subsequent processing, deep hole drilling of the titanium alloy pipe was completed 48 times. To meet the company’s development and production needs, it solves the key to deep hole drilling technology for titanium alloy pipes.

4, processing summary
By verifying the test results, it has been proved that it is possible to develop such a deep hole processing scheme. Deep hole drilling methods and machining techniques for titanium alloys have been incorporated into the relevant technical documentation and applied to dedicated production lines.

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