Titanium milling has always been a challenging process, and it must be done exactly right because this is the choice metal for a lot of high-end products in the aerospace, medical, and other industries that require precise, reliable results. The characteristics of titanium make it ideal for many situations, but those same traits can cause a lot of wear and stress on the machining tools.
In order to deal with these unique challenges, machinists need more than just the right tools. It’s important to use the right techniques to extend the life of the tools and produce the quality products that those industries expect.
Milling titanium is a very time-consuming process. In fact, most of the costs of titanium products are related to the difficulty and the time spent machining it, rather than the rarity of the metal. And since cutting speed is directly affected by the arc of engagement of the cutter, the larger the engagement, the longer it takes to cut. This simply can’t be avoided right now because if the speed is pushed too hard, the tools could be damaged. While new methods are being researched and tested, a lot of it will always come back to using the right tools for the right job.
Understanding the Challenges
With 40% to 50% of the costs of titanium parts directly related to machining, companies are constantly looking for new ways to increase speed and reduce prices. However, this has to be done with extreme amounts of care in order to keep the quality high and the tools in good shape.
One of the biggest differences in titanium, compared to other metals, is the way it builds up heat. Since this metal is so heat-resistant, the high temperatures that are generated from the cutting process isn’t dissipated in the chip, as it would be in steel or aluminum. Instead, the heat is absorbed by the cutting tool. In fact, because the thermal conductivity is so low, overly aggressive milling could even lead to combustion. On top of that, titanium may not be as hard as other metals, but it is quite abrasive, which can cause further damage to the tools.
Using the Right Tools
Any type of metal machining will lead to wear and tear on the tools, but when titanium is under the knife, so to speak, extra precautions are necessary to help extend tool life while maintaining a sustainable and profitable cutting speed.
Milling titanium requires a positive geometry combined with quality edge preparation to protect the tool while making efficient cuts. This can start by determining the materials used in the cutting tools. Many machinists prefer carbide because it has a wear resistance that allows it to be used at higher speeds. However, it is more brittle than high speed steel, so there are some instances where it might not be ideal.
Keeping it Cool
In order to offset the amount of heat generated by the milling process, coolant must be used to dissipate the heat and protect the edge of the tool. Some tools employ a through-spindle coolant to deliver the liquid directly to the cutting edge. Others, depending on the depth of the cut, will need a high-pressure coolant pump to stop chips from welding to the cutting edge.
Potential for New Methods
There has been a lot of discussion about thermally assisted machining as an alternative. Basically, this technique involves using a laser to heat and soften the metal before the tool reaches it. It has been used on extremely strong metals and has shown promise. However, while most reports have shown that machinability is improved through this method (i.e. the cutting forces are clearly reduced), there has not been a lot of evidence to support whether or not this significantly extends the tool life.
A Careful Process
Even a small increase in the milling speed on titanium can lead to much larger wear on the tools. Finding that balance of speed and proper tool care can be difficult, but it is necessary to continue producing quality products at sustainable speeds and affordable costs.
For more information on Titanium Processing Center visit: www.titaniumprocessingcenter.com.
Titanium Processing Center (Corporate)
51513 Industrial Road
New Baltimore, Michigan 48047
Toll-free: 888.771.9449 | Phone: 586.716.7555 | Fax: 586.716.8430
Titanium Processing Center Texas Group
8601 Fawn Trail Bldg. #2
Conroe, Texas 77385
Phone: 936-271-7773 | Fax: 936-271-7783