Selecting Titanium Alloys and Grades

Titanium is available in different grades, including commercially pure titanium (>99% Ti) (Grades 1 to 4) and titanium alloys (Grades 5 and higher). In the table below, you’ll find a description of these grades, their properties, and applications. This information can help you choose the right material for your titanium part design.

Table 1: Common Titanium Grades Used for CNC Machining

CNC machining supports design complexity, but titanium poses special challenges.

Tips for CNC Machining Titanium 

Titanium can be machined with CNC milling, turning and lathing, drilling and boring, utilizing a multi-axis precision machine. Each process involves different operations and has benefits and challenges.

• Milling uses rotating tools to shape parts and requires managing speeds and coolant levels to prevent tool wear. 

• Turning and lathing rotate the titanium workpiece while a stationary tool shapes it. It’s ideal for cylindrical parts but requires careful handling to avoid excessive vibrations and ensure a smooth finish. 

• Drilling and boring are two similar processes. Drilling creates precise holes using sharp bits. Boring enlarges these holes and is used to meet tight tolerances. 

• 5-axis machining is the most advanced process, allowing the titanium workpiece to move along five different axes. Because it can create intricate parts with fewer setups, it’s particularly useful in aerospace and medical applications.

Looking ahead, emerging technologies such as AI-driven toolpath optimization and smart machining systems are expected to revolutionize CNC machining. Additionally, the use of hybrid manufacturing—combining additive and subtractive methods—is expected to provide greater design flexibility.

Fictiv uses high-precision CNC machining equipment to produce parts at amazing speeds.

Setting CNC Machining Parameters

Regardless of the CNC machining equipment you use, it’s important to fine-tune your machining parameters to achieve high-quality results. Cutting speeds and feed rates, machining tolerances, and coolant are important considerations.

Cutting Speeds and Feed Rates

Careful control of cutting speeds and feed rates help prevent workpiece overheating and tool wear. Lower cutting speeds paired with higher feed rates reduce heat buildup and maintain the integrity of the tool and the workpiece. If higher speeds are required, cutting tools coated with titanium aluminum nitride (TiAlN) or titanium carbo-nitride (TiCN) are recommended.

When CNC milling titanium, the ideal cutting speed varies depending on the specific type and grade of titanium, as well as the tooling and coolant used. A general guideline is a surface speed of approximately 60-100 feet per minute (FPM) or 18-30 meters per minute (MPM). It’s crucial to also consider other factors such as feed rate, depth of cut, and the machine’s power and rigidity. 

Machining Tolerances

It’s difficult to achieve tight tolerances with titanium because of the metal’s sensitivity to heat and tendency to cause tool deflection. However, you can prevent excessive deflection by ensuring that parts are well-supported and secured. Shorter cutting tools also reduce deflection, while a well-stabilized setup minimizes vibrations that affect machining accuracy. 

Coolant Use

Temperature control is critical when machining titanium. Directing a steady, high-pressure stream of coolant at the cut region cools both the workpiece and the cutting tool. A high-pressure coolant stream also removes chips that would otherwise stick to the tool. Adjust the volume and concentration of coolant to optimize usage and avoid waste.

To mitigate heat build-up, use a coolant with excellent lubricity and cooling properties. Coolants specifically designed for machining difficult materials, such as emulsion-based coolants with high lubricity, are recommended.

Additional Machining Considerations 

Preventing overheating involves more than just coolants. Along with adjusting feed rates and spindle speeds, consider cutting strategies to improve efficiency and reduce heat. For example, increasing the axial depth of the cut while reducing radial engagement helps with thermal management.

CNC-machined parts like this may require several surface finishing methods. 

Following Safety Precautions and Best Practices

Safety is important in titanium CNC machining to reduce the risk of injuries to workers and damage to equipment. Machine crashes, electrical hazards, health hazards, and flying debris are all risk factors. Use the bulleted list below as a checklist for safety precautions and best practices. 

• Understand the importance of safety in CNC titanium machining

• Wear recommended personal protective equipment (PPE)

• Follow safe handling and storage procedures for titanium materials

• Perform machine setup and regular maintenance checks

• Adhere to proper cutting tool selection, handling, and storage practices

• Handle and dispose of coolants and lubricants properly

• Implement fire prevention measures and response plans

• Safely remove and dispose of titanium chips and debris

• Use ergonomic workstation setups to reduce operator fatigue

• Implement training programs for operators on safe practices

• Develop emergency procedures and first aid measures

Surface Finishing CNC-Machined Titanium Parts

Titanium CNC machining supports the use of various surface finishing treatments for functional and aesthetic purposes. Often, finishing is used to reduce surface roughness and improve the appearance, durability, and performance of machined parts. 

The surface finishing processes used with titanium include:

• Polishing 

• Bead blasting

• Anodizing

• Chroming

• Brushing

• Painting

• PVD coating

• Powder coating

• Electrophoresis 

Industry Standards and Certifications

There are several standards and certifications that apply to CNC machining titanium.They help ensure the quality and reliability of titanium parts produced through CNC machining, especially in critical applications like aerospace and medical devices.

Industry Standards

ASTM International, the International Standards Organization (ISO), and SAE international have published industry standards that apply to titanium CNC machining. 

ASTM Standards

• ASTM B265: Standard Specification for Titanium and Titanium Alloy Strip, Sheet, and Plate.

• ASTM F136: Standard Specification for Wrought Titanium-6Aluminum-4Vanadium ELI (Extra Low Interstitial) Alloy for Surgical Implant Applications.

• ASTM F1472: Standard Specification for Wrought Titanium-6Aluminum-4Vanadium Alloy for Surgical Implant Applications.

ISO Standards

• ISO 5832-2: Implants for surgery – Metallic materials – Part 2: Unalloyed titanium.

• ISO 5832-3: Implants for surgery – Metallic materials – Part 3: Wrought titanium 6-aluminum 4-vanadium alloy.

SAE Standards

• SAE AMS 4911: Titanium Alloy Sheet, Strip, and Plate, 6Al – 4V Annealed.