Titanium is a high-performance engineering material with excellent strength-to-wight ratio, fatigue strength, and corrosion resistance. The use of titanium and its alloys is widespread, such as jewelry, aircraft, power plants, medical equipment, missiles, etc. However, it is not as easy to machine as other soft materials. Several considerations are necessary for titanium CNC machining, from tooling to machining variables.
This article will discuss all aspects you need to know in the machining of titanium and alloys, including machining operations, factors to consider, advantages, applications, surface finishing options, etc.
What is Titanium?
Titanium is a lightweight, strong, durable, and highly corrosion-resistant metal. It offers superior toughness and hardness along with a low coefficient of friction and wear resistance.
The accurate machining of Titanium is quite challenging, especially when it needs to be manipulated into intrinsic shapes. Therefore, CNC machining is the ideal option for titanium manufacturing.
Titanium Alloy Grades
Two titanium alloys are popular in manufacturing processes, including the CNC machining.
- Ti-6Al-4V： It offers a high strength-to-weight ratio and is suitable for aircraft parts.
- Ti-6Al-4VEli： It offers excellent bio-compatibility properties, making it ideal for medical applications.
Titanium sheets
In the market, CNC-machinable Titanium comes a range of grades (Grades 1-10). As you go up the number, strength increases simultaneously.
| Grade | Description |
| Grade 1-4 | It is the purest form of Titanium among the grades. It is lighter than steel and offers high strength than that. |
| Grade 5 | It is compatible with high working temperatures, which makes it appropriate for chemical processing, aerospace, marine, and many more applications. |
| Grade 9 | Titanium alloy of grade 9 is famous for its high strength and weldability. It can work in high temperatures without losing its mechanical properties significantly. |
Titanium CNC Machining
Carbide cutting tools with a circular arc transition tip are used for the Titanium CNC machining. Hardness-level of Titanium requires a more brutal machining tool. These tools contain a slight front angle and a large rear angle to optimize the touching length (The machining area from the cutting tool area). A considerable touching length lowers the friction.
The round tip creates sharp corners without burnout and chipping. CNC machining of Titanium involves low machining speed and feed rate if a significant cutting depth is required.
High cutting speeds are also possible. However, keeping an eye on temperature increment in the workpiece and tool is suggested. Sometimes, the high cutting speed can cause chipping & fracture because of the reaction between chips and tool.
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CNC Milling of Titanium
Part from CNC-milling
CNC milling creates the required shape from a workpiece by removing material with the rotatory tool. It is crucial to consider various properties of Titanium and act accordingly to mill the titanium workpiece. The high strength and hardness of Titanium require tough milling tools such as those made with cement carbide & hardened steel. The immense force on the titanium workpiece can cause the overheating problem in milling tools, resulting in the formation of burrs and dimensional inconsistency.
To avoid overheating in CNC milling, the lubricant must be applied continuously. In addition, machining speed can also be reduced if that does not limit the final requirements, such as surface finish & tolerances.
Vibration is another outcome of Titanium CNC milling. The high strength causes vibration in cutting tools, which can shorten the life span. Again, cement carbide tools are the best choice for minimizing vibration.
CNC Turning of Titanium
Titanium CNC turning In CNC turning, the workpiece rotates, and the tool fed away the material to convert it into the required geometry: the high mechanical strength and toughness of Titanium demand a slower turning speed. High RPM of the workpiece can cause the formation of craters and grooves. In addition, excessive heat contributes to chip formation.
- Cutting fluid minimizes the rise in temperature, so use the appropriate coolant.
- Fine-grained carbide tools are the go-to option for CNC turning.
- It is recommended to consider 15 to 20% of blade diameter while choosing cutting depth.
CNC Drilling of Titanium
Moderate speed is suitable for titanium drilling because high speed causes vibration and overheating problems. Titanium’s high strength and hardness require carbide-tipped drill bits to create an accurate hole.
Drilling the deep hole in Titanium is challenging. Hardness can affect the straightness of the hole. If you need a deep hole, you can use a hollow-core cutting tool to create a straight-circular hole (Safian Sharif, 2012).
Variables of Titanium CNC machining
CNC Machining of Titanium has some challenges because of some mechanical properties of Titanium, such as poor thermal conductivity, mechanical strength, and hardness. There are different considerations for obtaining the best machining result.
- Excessive heat
When determining the feed rate and cutting speed, it is crucial to consider excessive heat. Titanium is not like copper or aluminum. It produces a large amount of heat, which can damage the tool and the quality of the part.
In addition, the cooling set-up should be the priority, and RPM must be adjusted when the temperature exceeds the expected range.
- Appropriate tool path
The basic principle of the tool path is that the CNC machining tool should always engage the titanium workpiece. The optimization of the tool part ensures less cycle time and quality. For instance, setting the tool path in a cyclic pattern combination can optimize groove creation.
- Holding of the workpiece
Titanium workpieces must be tightly gripped with rigid work-holding arrangements in a way that does not cause machining to stop. An improper grip (too loose or tight) can harm a workpiece and a CNC cutting tool.
- Built-up edge
Built-up edge is another issue with Titanium CNC machining. The chips can stick to the tool, so frequent removal is necessary to avoid this issue. High-pressure coolant can be applied to get rid of the chips.
Other Processing Approaches for Titanium Parts
Besides CNC machining operations, titanium can be cut and shaped using other manufacturing approaches, plasma cutting, laser cutting, waterjet cutting, etc. These techniques serve different purposes as non-shear cutting methods. Let’s discuss one by one in brief;
Titanium Plasma Cutting
Cutting titanium alloys using plasma involves a plasma torch that creates a concentrated jet of ionized gas called plasma. This plasma arc melts the material precisely and makes cuts to shape the workpiece. Meanwhile, the temperature can reach up to 30,000°C.
The electric arc is generated between an electrode (cathode) and the titanium workpiece (anode). This arc ionizes the gas (typically argon, nitrogen, or a mixture) to form the plasma beam. Subsequently, the plasma torch guides the jet through a constricted nozzle towards the titanium workpiece. The Advanced CNC plasma cutter can guide the movement with pre-loaded CNC programs.
The following table shows the key characteristics of plasma cutting titanium in brief;
| Gas Type | Argon, nitrogen, or hydrogen-argon mixtures |
| Plasma Torch | Oxy-Acet torch |
| Cutting Speed | 10-200 mm/min |
| Gas Flow rate | 0.5-1.5 m³/h (Argon), 0.3-1.0 m³/h (Nitrogen) |
Furthermore, plasma cutting applications are critical in various industries, from medical equipment to aerospace components.
- Aerospace: Airframe components, Engine parts, Landing gear, and structural elements.
- Medical: Implants (hip and knee replacements), Surgical instruments, Medical devices, and prosthetics.
- Industrial: Chemical processing equipment, heat exchangers, and pressure vessels.
- Marine: Shipbuilding components, submarine parts, offshore drilling equipment.
- Automotive: High-performance car components like exhaust systems and structural parts.
- Defense: Military vehicle parts, armor plating, protective gear.
Renewable Energy: Wind turbine components, solar panel parts, and energy storage systems.
Titanium Laser Cutting
Another titanium processing method is laser cutting, which utilizes a focused laser beam to melt and vaporize material, resulting in precise and clean cuts. However, the heat sensitivity and titanium properties can cause wrapping, contamination, and discoloration if the suitable parameters are not used.
Moreover, the precision of titanium laser cutting allows for intricate designs with tight tolerances. These benefits make it applicable to food, aerospace, medical, automotive, electronics, and other industrial components.
The table below briefly summarizes the characteristics of laser cut titanium;
| Laser Cutter type | CO2 laser |
| Speed | 50-1000 mm/min |
| Thickness | 0.5-20 mm |
| Gas Type | Nitrogen, Oxygen |
Titanium WaterJet Cutting
A high-pressure water jet mixed with abrasive cuts the titanium sheets and bars into accurate shape by eroding the material from the cutting position. The pressure of the jet can reach up to 4000 bar. Waterjet cutting addresses the possibility of thermal damage in other processing approaches like laser and plasma cutting.
The characteristics of titanium waterjet cutting are as follows;
| Suitable abrasives | Garnet, Olivine, Silicon Carbide |
| Speed | 25-100 mm/min |
| Thickness | 0.5 to 150 mm |
| Jet pressure | 1000 to 4000 bar(100 to 400 MPa) |
Surface Treatment of Titanium Parts
CNC machining of Titanium can leave tool marks and some tiny burrs on the machined surface. However, it offers an excellent as-machine surface finish ( Ra value as low as 1.20 μm (G.A. Ibrahim, 2003). Therefore, the as-machined finish of titanium parts is insufficient for critical applications like medical implants, electronics, components, aerospace parts, etc. Subsequently, surface treatment also becomes essential for aesthetic applications.
There are different surface treatment techniques for titanium parts that can achieve roughness levels as low as 0.3 μm, each with unique capabilities and advantages.
Plasma Electrolytic Oxidation
It is also known as Micro-Arc Oxidation (MAO). This process involves immersing titanium parts into an electrolyte solution and applying a high-voltage electric field. It develops a hard and wear-resistant oxide layer(hard oxide coating) on the surface of the metal. The titanium part is immersed in an electrolyte solution and subjected to a high-voltage electric field during this process. This causes micro-discharges to occur on the surface of the titanium. This finish offers corrosion resistance, wear resistance, and thermal stability.
Anodizing
Anodizing can develop a protective coating of varying thickness using the electrolysis deposition process. The thickness and properties of the oxide layer can be controlled by adjusting the anodizing parameters, such as voltage, current density, and electrolyte composition. Titanium anodizing not only improves corrosion resistance but also allows for various colors to the surface through dyeing.
Titanium Polishing
Titanium polishing involves grinding with large to small-size grits, followed by a buffing process. It removes all surface irregularities and imperfections to provide a smooth and mirror-like finish. So, polish titanium enhances the aesthetic of titanium parts and can also reduce friction and wear in specific applications.
Titanium Vs. Steel Vs. Aluminum Vs. Stainless Steel
Steel, stainless steel, and aluminum are the three main alternatives in terms of strength and lightweight. Stainless steel and steel both are the iron alloys with variations of carbon, chromium, manganese, and other alloying element. On the other hand, aluminum is a highly corrosion-resistant and lightweight material with excellent machinability and formability.
If we specifically compare titanium vs. steel, titanium is lighter, stronger, and more corrosion-resistant than steel but is more expensive. Meanwhile, steel is heavier, more cost-effective, and widely used for its versatility and strength. Similarly, steel offers a higer machinability in head-to-head comparisons with machining titanium vs steel. So, choosing tooling and machining parameters for titanium requires different specific considerations. Therefore, titanium vs aluminum, titanium vs stainless steel, and other comparisons can help to make wise decisions to optimize the machining processes.
Furthermore, the table below differentiates these manufacturing materials in various aspects;
| Criteria | Titanium | Steel | Aluminum | Stainless Steel |
| Key Properties | Lightweight, strong, corrosion-resistant | Strong, versatile, cost-effective | Lightweight, corrosion-resistant, conductive | Corrosion-resistant, strong, durable |
| Machinability | Moderate to difficult | Moderate to easy | Easy | Moderate to difficult |
| Strength-to-Weight Ratio | High | Moderate | High | Moderate |
| Machining Alloys | Ti-6Al-4V | 1020, 1045, A36 | 6061, 7075 | 304, 316 |
| Application Examples | Aerospace parts, medical implants | Construction, automotive, tools | Aircraft structures, packaging | Medical instruments, kitchenware |
Titanium CNC Machining Advantages
CNC machining of Titanium has various advantages, such as excellent dimensional accuracy, complex shapes, cost-effectiveness, quick lead time, high strength-to-weight ratio, and many more. Let’s briefly go over a few of them.
- Biocompatible
Titanium has several medical applications because of its biocompatible corrosion resistance & non-toxic nature. It can be combined with iron, aluminum, molybdenum, nickel, and other elements to make it stronger.
- Superior corrosion resistance
CNC-machined titanium is highly corrosion-resistant. So, it does not wear for a long time and withstands any level of dampness & maritime conditions.
- High strength-to-weight ratio
Titanium is a lightweight metal with a high strength-to-weight ratio., 1.3 times aluminum and 3.5 times stainless steel. This advantage makes it ideal for aerospace applications.
- Complicated shapes
CNC machining allows to manipulation of Titanium into complex shapes. Using highly rigid Carbide or diamond tools can convert any complex 3D design into reality with a high degree of dimensional accuracy.
- Cost-effective
Creating titanium parts with CNC machining is more cost-effective than conventional manufacturing approaches and cutting-edge technology like 3D printing.
- Precision
CNC machining creates accurate parts for several applications. An advanced 5-axis CNC machine can maintain tolerances as low as ±0.0005″.
Applications of CNC Machining Titanium Parts
- Aerospace
Titanium parts in an airplane
The corrosion-resistive nature and high strength make Titanium suitable for aerospace applications. Other properties such as fatigue strength, toughness, temperature resistance, and wear resistance aid in the functionality of titanium aerospace parts. CNC machining of Titanium has a significant role in the creation of Engine blades, landing gear, shafts, interior structures, compressor wheels, connecting rods, engine compartments, and many more.
- Medical
Titanium exhibits chemical inertness and biocompatible properties, which allow it to be used in medical applications. The high accuracy of medical implants & surgical equipment can be achieved by CNC machining. Some typical medical applications of Titanium include Bone growth stimulators, spinal fusion devices, bone plates, orthodontics, and fake body parts.
- Marine
CNC machining of titanium is also of significant use in the marine industry. Superior corrosion resistance and lightweight character are well suited for marine applications, such as decks, shackles, snap hooks, pressure vessels, submarine probes, and many more.
- Automotive
Various automotive parts of Titanium
Sport and luxury cars widely use titanium because of its impact resistance and durability. It is used in frames, fasteners, mufflers, exhaust Pipes, engine valves, load-bearing springs, and many more.
- Others
In addition to all these applications, titanium CNC machining is applicable in oil & gas, construction, architecture, jewelry, sports, EV, and other industries.
Final Thought
Titanium is a lightweight metal with excellent corrosion resistance, high mechanical strength, hardness, biocompatibility, and other unique mechanical & chemical properties. These properties make it suitable for automotive, aerospace, medical, construction, architecture, marine, and other industrial applications. Almost all titanium parts can be created with CNC machining for these industries.
Prolean is a dedicated Titanium CNC machining service provider. We have cutting-edge CNC precision machining technology and expert engineers, so send us your design; you are just a few steps behind in getting your parts.
FAQ’s
Why is Titanium difficult for CNC machining?
The properties of Titanium, including its hardness, low thermal conductivity, and high mechanical strength, make it challenging for accurate CNC machining. It requires consideration of various operating variables.
What are the essential considerations for the CNC machining of Titanium?
Sometimes, a minor change in operating variables can change the quality of the machined part, and you must consider different factors when designing quality titanium parts. The variable includes heat generation, formation of built-up edge, cutting speed, feed rate, and many more.
Why choose CNC machining for titanium parts?
CNC machining of Titanium provides excellent dimension accuracy and tolerances as low as ±0.0005″. In addition, it can create complex shapes, is cost-effective, and offers quick lead time.
What are the common titanium alloys for CNC machining?
Ti-6Al-4V and Ti-6Al-4VEli are the most used titanium alloys in CNC machining projects. However, there are ten different grades (grades 1 to 10) of titanium alloys with different properties.
Bibliography
- A. Ibrahim, C. C. (2003). The Effect of Dry Machining on Surface Integrity of Titanium Alloy Ti-6Al-4V ELI. ScienceAlert.
- Safian Sharif, E. A. (2016). Machinability of Titanium Alloys in Drilling. IntechOpen.
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