Titanium and its alloys are increasingly seeing widespread use in aerospace and biomedical applications that take advantage of its unique properties. However, machining titanium also presents unique challenges that precision engineers accustomed to machining other metals will find difficult. Here we look at why machining titanium is so difficult and different techniques you can use to get the best results when machining titanium.
WHY TITANIUM IS SO POPULAR
While aluminum and aluminum alloys were previously the preferred materials of the aerospace industry, newer aircraft designs are increasingly making use of titanium and titanium alloys. These materials are also used in the biomedical industry. The reasons for their popularity include light weight, high strength, excellent fatigue performance and high resistance to aggressive environments, remaining free of rust and degeneration. Titanium parts last longer and provide better performance and results than other metals and materials.
WHY TITANIUM IS SO DIFFICULT TO MACHINE
The very properties that make titanium such a beneficial and high-performance metal are also the properties that can make it difficult to machine. Just as when using aluminum and aluminum alloys, up to 90% of the material may need to be milled and turned away to produce the final part.
Titanium alloys have a low Young’s modulus, which causes spring back and chatter during machining. This can create poor surface quality in the finished product.
Because of titanium’s high work hardening tendency and the stickiness of the alloy, long continuous chips are formed during turning and drilling, which can entangle the tool and impede function. This almost eliminates the possibility of automating titanium machining.
Despite these setbacks, there are techniques that make machining titanium easier.
HOW TO MACHINE TITANIUM
Machining titanium requires coated carbide tools that will resist the stickiness of the alloy and break up the long chips. The tool coating also helps to manage the heat produced with machining.
Keeping radial engagement low is important to counteract the effects of heat generation and work hardening tendency. Increasing the number of flutes in the end mills can help to counteract the lower feed per tooth to increase productivity.
Application of high pressure coolant helps to reduce heat and damage to the tool. Currently, ultrasonic assisted machining is in R&D. The goal is to reduce the contact time of the tool, and prolong tool life.
The technique used when machining titanium can also help to improve results. By using ‘climb milling’, arcing in, ending on a 45-degree chamfer, using a secondary relief tool design, altering the axial depth, and using a tool at least 70% smaller than the tool pocket, you can reduce tool damage and get better results when machining titanium.
By carefully examining the unique properties of titanium and adjusting machining appropriately, you can get the best results for your tool and your finished piece. For more assistance in machining titanium, talk to the experienced engineers at Inverse Solutions for a custom titanium solution for you.