Machining small precision parts of titanium alloy is indeed a challenge.The reason why it is difficult is mainly because of the material properties of titanium alloy: it is both "sticky“ and ”hard", its thermal conductivity is poor, the tool is easy to wear during processing, and the parts are easy to deform.
However, the modern manufacturing industry has developed a mature set of coping strategies.The main processing of such parts are：
Physical cutting: The mainstream micro-milling process is suitable for manufacturing complex three-dimensional structures.
Special processing: including electrolytic processing, laser processing, etc., used to deal with scenes that are difficult to reach with high-precision or traditional tools.
Let's take an in-depth look at how these two methods are done.
Mainstream method: micro-milling-like “cutting” with a micro-engraving knife
This is currently a commonly used method for manufacturing small precision titanium alloy parts, which can be understood as the miniaturization of traditional CNC milling.But the core problem it has to overcome is: how to “tame” the hard and sticky titanium alloy.
In order to solve this problem, engineers started from three key links：
Clever ”cutting" strategy: For thin-walled parts, conventional “dynamic milling” can easily cause deformation of parts due to uneven force.The engineers found that the use of “layered milling”, that is, the method of “shallow cutting depth and fast feed”, can effectively disperse the cutting stress, so that parts as thin as eggshells (0.5mm) can also be formed stably.
The “counter-intuitive” design of the tool: when machining conventional materials, the larger the spiral angle of the tool, the more conducive it is to cutting.However, when processing the thin wall of titanium alloy, the spiral angle will produce a reciprocating force up and down, but it is easy to cut through the parts.Therefore, a straight-edge milling cutter with a spiral angle of 0° will be used, and the cutting force generated by it will always press down on the workpiece. With the vacuum suction cup, over-cutting and deformation can be greatly avoided.
”Customized" blanks for titanium alloys: The traditional view is that forged or rolled titanium alloys are better processed.However, the study found that the titanium alloy directly formed by selective laser melting (SLM) 3D printing technology has a fine needle-like grain structure inside, which is more suitable for micro-milling than traditional thick isometric grains, which can significantly reduce burrs, improve tool life and surface finish.
Advanced method: Special processing-forming by "corrosion” or "dissolution”
For some areas where traditional tools are difficult to process, such as micropores, complex cavities, or parts that have high requirements for stress-free surface, special processing techniques are required.
Ultrasonic assisted electrolysis processing: This is a “soft knife” technology.It uses the principle of electrochemistry to “dissolve” the workpiece (anode) like metal corrosion, while the processing tool (cathode) itself does not come into contact with the workpiece, so there is no cutting force and no tool wear.In order to solve the problem that the dense passivation film on the surface of the titanium alloy will hinder the electrolysis reaction, the researchers introduced high-intensity focused ultrasound to accurately “bombard” the processing area with sonic energy to make the electrolysis reaction proceed smoothly, so as to achieve high-precision material removal.
In general, processing small precision parts of titanium alloy is a systematic project.It is not simply choosing a kind of equipment, but needs to comprehensively use special tool design, optimized tool path, innovative clamping methods, and even combined with 3D printing on the basis of understanding the characteristics of titanium alloy. This “love and hate” material can be shaped into high-precision parts.
