Today’s CNC machining industry is extremely demanding, with titanium and its various alloys commonly used to create strong parts for aerospace, automotive, firearm, and medical applications. We’re talking about one of the most popular machining metals on the market here. But while titanium may be ideal for a wide variety of projects, it’s not the best material for everything. Here’s what you should know.
What are the benefits of using titanium for CNC machining?
CNC machinists sometimes prefer to work with titanium and titanium alloys because of the rust-resistant properties thereof. Furthermore, this metal family is generally recyclable which means it’s perfect for clients concerned with eco-friendly manufacturing. Plus, titanium offers the best tensile strength for multiple techniques while remaining lightweight enough to meet certain industry requirements with precision.
DID YOU KNOW: The manufacturing world used 1.16 metric tons of titanium in 2019 alone.
What are the most common titanium grades and alloys?
There are multiple alloys and grades of titanium that frequently get used by high-performance CNC machine shops. In fact, this is one of the most available resources on the market, with nearly 40 different ASTM varieties to choose from. Meanwhile, there are five (5) distinct grades to classify this metal’s chemistry. And since metal grade can affect its machinability, it’s crucial to know and understand the different properties of each.
In general, the first four titanium grades are defined as commercially pure but have varying levels of tensile strength. As for grade five titanium, which is sometimes called Ti6Al4V or Ti 6-4, it’s usually an alloy made up of at least 6% aluminum and about 4% vanadium (hence the name). But while all-titanium grades are usually grouped, there are a few important distinctions to be made before machining.
The 3 most important factors of titanium machining
Any experienced CNC machinist or manufacturing engineer will tell you the same thing: titanium can be extremely difficult to work with. Although it’s one of the most durable materials known to humankind, it’s surprisingly malleable and not quite as rigid as some other metals. That’s why these three factors are always considered:
Due to the flexible physical properties of titanium, machinists must establish a secure grip on the workpiece using a robust machine. This helps experts avoid cut interruptions by keeping the tool moving at all times. It also decreases the wear and tears on crucial tooling equipment.
#2. Galling and BUE
Galling and BUE (build-up edge) are both major disruptors to a precision CNC machining project. Unfortunately, titanium is notorious for both. Generally, machinists pump tons of high-pressure coolant onto the cutting surface to prevent it. But that doesn’t work for every application.
Too much heat can become a formidable foe in titanium manufacturing. Commercially pure grades are soft and gummy, but alloy elements are used to increase the material’s hardness. That, in turn, can change the temperature and affect tool dexterity even during routine machining processes.
Basically, the primary factor during titanium and alloy machining is that the metal may shift slightly while being processed. However, the techniques used to limit those shifts remain constant. Typically, machinists try to prevent galling and BUE at all costs. They also monitor heat generation closely and use coolants as much as they can. Still, there are some other key considerations that all legit machinists must make when they’re building with titanium.
How to machine titanium correctly
Contrary to popular belief, machining titanium doesn’t have to be difficult. For expert machine shops like Pioneer Cuts, working with strong and/or lightweight materials is par for the course. Most of the time, experts start by selecting the proper tool coating to prevent excessive galling and chipping. Either way, establishing stability is as essential as reading the project’s blueprints accurately.
So, use the following tips, tricks, and techniques to turn raw titanium into a workable component without all the fuss:
#1. Lower the Radial Engagement
Always try to maintain a low radial engagement because titanium presents several challenges in terms of heat dissipation. Compared to machining other metals, more heat goes into the tool rather than the material itself. So, the radial engagement typically dictates your project’s possible speeds and feed times.
#2. Raise the Flute Quantity
Most end mills feature between four and six flutes, but this material may demand a few more. Well-equipped CNC machine shops tend to use at least 10 flutes for titanium machining. That’s because increased flute quantity can compensate for a low feed-in many applications involving this alloy.
#3. Try Climb Milling
Climb milling consists of creating a thick-to-thin chip formation. It’s useful because thick chips are better on entry and thin chips are better on exit. This technique helps to prevent chip adhesion while allowing machinists to perform contour surface milling without sacrificing quality, consistency, or accuracy.
#4. Change the Axial Depth
Titanium machining commonly involves surface oxidation and other chemical reactions. Then, if a tool is repeatedly used in that sensitive spot, it could cause premature damage to the material. Successive axial cuts may ultimately create lines that the aerospace industry will reject. Change the AD with each new pass.
#5. Use Smaller Tools
Sometimes, the best way to machine titanium is to choose tools that are smaller than the pocket. Remember, there’s a lot of heat to express here, so some clearance is always helpful. Small pocket milling usually requires a tool diameter that’s no more than 70% of the pocket’s diameter. Then, the tool can be offset by about 10% to help with climb milling.
While there are several different grades of titanium and countless uses for it, machining this metal may not be easy for every CNC machine shop. And although the techniques used to manufacture parts with it are straightforward, very few facilities can handle complex processes without disregarding industry regulations. So, it’s important to work with a company that not only understands how the process works but can provide timely services at an affordable price.
For more information on any of these titanium tooling tactics, consult a CNC machining expert at Pioneer Cuts. Don’t forget to submit your information to get a quick 6-hour quote while you’re there.