CNC turning titanium parts offers numerous advantages, but careful consideration of several factors is crucial for successful machining. Here's a breakdown of the key points you mentioned and additional details to consider:

1. Choosing the Right Cutting Tool

l Material: Standard high-speed steel (HSS) tools used for softer metals are not suitable for titanium. Instead, opt for carbide cutting tools. These offer superior wear resistance and can handle the higher cutting forces required for titanium.

l Coating: As you mentioned, coatings like Titanium Aluminum Nitride (TiAIN) are highly recommended. This coating reduces friction and galling between the tool and the titanium workpiece, leading to extended tool life and improved surface finish. Other coatings like Chromium Nitride (CrN) can also be considered depending on the specific application.

l Geometry: The geometry of the cutting tool, including the rake angle and flute design, significantly impacts chip formation and heat generation. Selecting the appropriate geometry for the specific titanium alloy and machining operation is crucial. For instance, a higher rake angle can help reduce cutting forces and heat generation.

2. Cutting Parameters

l Cutting Speed (rpm): This refers to the rotational speed of the cutting tool. Titanium machining typically requires lower cutting speeds compared to softer metals to minimize heat generation and tool wear.

l Feed Rate (mm/rev): This is the rate at which the cutting tool moves along the workpiece. A slower feed rate is generally used for titanium to reduce chip load on the tool and improve surface finish.

l Depth of Cut (mm): This refers to the thickness of material removed with each pass of the cutting tool. Taking shallower cuts helps distribute the cutting forces and heat generation, minimizing tool wear and improving surface quality.

3. Coolant Strategy

l Coolant Type: A high-pressure coolant system with a coolant specifically formulated for titanium machining is essential. These coolants contain lubricants and anti-foaming agents to reduce friction, cool the workpiece and cutting tool, and effectively carry away chips.

l Coolant Application: The coolant should be directed at the cutting zone where the tool meets the workpiece. Flood cooling, where the entire cutting area is submerged in coolant, is often preferred for titanium machining.

4. Workholding

l Workholding Fixtures: Securely fixturing the titanium workpiece in a CNC machine is critical for maintaining accuracy and avoiding vibrations during machining. Custom-designed fixtures that clamp the workpiece rigidly are often necessary.

l Workpiece Surface Preparation: Ensuring a clean and smooth surface on the titanium workpiece before machining can improve chip formation and reduce cutting forces on the tool.

By carefully considering these important factors and employing the appropriate techniques,  you can achieve successful and efficient CNC turning of titanium parts.