A Case Study in CNC Machining

When machining any workpiece, it is critical to address fundamental parameters such as geometric dimensions, surface finish, and flatness to ensure quality. CNC Tools These attributes are not only essential for standalone components but also play a vital role in seamless assembly with other parts. Achieving a precise surface finish enhances the contact between mating surfaces, prevents gaps between butting surfaces, and avoids damage to interconnected components.

Problem Analysis

One of our clients faced challenges in manufacturing fixture components that met stringent aerospace industry tolerances. Fixtures are used to produce aerospace components with precise dimensions and high-quality finishes. Therefore, the fixtures themselves must exhibit tight tolerances and superior finishes. The base plate of the fixture, made from alloy steel with a hardness of around 450 BHN, was particularly problematic due to its manufacturing method.

The material was gas-cut (as shown in the accompanying diagram), which led to increased hardness in the raw material. The rough surface and hardened edges required careful machining to achieve the desired finish. Moreover, the plate was thin (32 mm thickness) and long (300 mm), which posed additional challenges during face milling due to the risk of bending.

Current Process Details

• Primary Operation: Face milling
• Workpiece: Fixture plate (base plate)
• Material: Gas-cut alloy steel, 32 mm thickness, 400–450 BHN hardness
• Machine: VMC BT40
• Cutter Used: D80 cutter with five insert pockets and an approach angle of 45°, using -ve inserts.

Challenges Identified

1. Axial Forces: The cutter’s 45° approach angle produced significant axial force, which led to bending in the thin and long plate during machining.
2. Surface Finish: High axial force degraded the surface quality.
3. Tool Life: High machining speed combined with low feed rate resulted in increased material hardness, negatively impacting tool life.
4. Material Toughness: The hardened surface, due to gas cutting, required a tougher grade of tooling with an optimal geometry to balance material removal and finish.

Proposed Solution

To address these challenges, the use of a cutter with a 90° approach angle was recommended. This cutter was better suited for machining thin and lightweight workpieces as it minimized axial forces and reduced the risk of bending during face milling.

Advantages of Using a 90° Approach Angle Cutter

1. Reduced Axial Force: A 90° approach angle significantly decreases axial load, making it suitable for machining thin and lightweight workpieces without deformation.
2. Improved Surface Finish: Lower axial force enhances surface quality and ensures consistent results.
3. Better Tool Life: The revised cutting geometry optimizes material removal and reduces the tool’s wear and tear, increasing its lifespan.
4. Process Stability: The workpiece remains stable during machining, resulting in precise dimensions and improved flatness.

Updated Process Details

• Operation: Two-pass machining to balance material removal and finishing.
• Cutter: A 90° approach angle cutter with medium-sharp geometry.
• Machining Parameters: Adjusted cutting speed and feed rate for better control and finish.

Outcome

The proposed solution resolved the issues faced by the client:

• The 90° cutter minimized axial forces, preventing plate bending.
• The surface finish was significantly improved, meeting the stringent aerospace industry standards.
• Tool life was extended due to optimized cutting parameters and reduced wear.
• The fixtures produced were of superior quality, ensuring perfect compatibility with the aerospace components during assembly.

This case demonstrates how analyzing machining challenges and tailoring solutions can lead to better results in CNC operations, even with complex materials and stringent requirements.