Optimizing CNC Machining: Process & Fixture Design for Thin-Walled Components

The design of processes and fixtures for machining thin-walled components in CNC operations requires careful planning to prevent deformation, maintain precision, and ensure efficiency. These components are widely used in aerospace, automotive, and electronics industries. However, their low rigidity and thin walls make them prone to deformation, surface chipping, and vibration marks.

If the process or fixture design is inadequate, continuous and stable batch production cannot be achieved, even if cutting loads are reduced and machining time is extended. This article shares process and fixture solutions for a real thin-walled machining case study, providing practical insights.

Challenges in Machining Thin-Walled Parts

Thin-walled assemblies, such as drone casings and electronic enclosures, usually have wall thicknesses below 2 mm. They reduce weight and improve thermal management in finished products. However, their lack of structural rigidity during CNC machining often results in instability in assembly dimensions, poor surface finish, and local or overall deformation.

Deformation After Machining

Thin-walled parts are likely to bend under tool pressure or clamping force. Even small cutting forces can deform unsupported areas, causing wall bending and tool deflection during machining. The risk is especially high when processing features near thin edges or hollow cavities.

Surface Chatter Marks

Because of their low mass and rigidity, thin-walled components vibrate easily during high-speed machining. This can lead to chatter marks on the surface, accelerated tool wear, and poor dimensional accuracy.

Practical Case: E-cigarette Aluminium Alloy Housing

Here, we look at machining an aluminium alloy e-cigarette housing, sharing how thin walls and tight tolerances affect production.

Product Specifications

• Material: AL6063-T6
• Dimensions: 92.8 × 40.8 × 22.8 mm
• Wall Thickness: 0.9–1.5 mm
• Production Volumes: 1000 pcs

Machining Requirement

• Assembly clearance is ≤0.1 mm between the front/rear deep blue surfaces and other components.
• T-shaped snap-fit grooves on the inner walls must pass a 3-metre drop test without detachment after assembly.
• The surface requires 200-grit sandblasting followed by anodizing, with no tool marks or vibration patterns allowed on visible areas.

Processing Challenges

• The 0.9–1.2 mm wall section is the assembly area with other structural components. So under deformation, it is difficult to maintain the required 0.1 mm assembly clearance.
• The peripheral area is a Grade A visible surface that must be free of defects, but the overall hollow structure lacks rigidity, especially in the central section, where cutting tool deflection and vibration issues are highly likely to occur.
• The weak wall rigidity also affects the dimensional consistency of the snap-fit, which can compromise drop test performance.

Issues with the Conventional Machining Solution

The blank uses profile material, with equal machining allowance added to the wall surfaces that need to be processed. A 3+2 axis rotary table is first used to machine the front and surrounding structures. After the part is cut off, a 3-axis CNC is used to process the reverse structure.

The advantage of this solution is its “short” process, as it only requires two steps. However, its disadvantages and limitations are also clear:

Limitations of the Approach

• Although the 3+2 five-axis rotary table provides multi-surface machining capability, it can only machine one product at a time.
• In most machining workshops, the number of 5-axis machines is much smaller than that of 3-axis machines. Therefore, the limited availability of 5-axis machines for batch operations makes it difficult to increase production capacity.
• In addition, all the machining challenges of thin-walled parts, mentioned earlier, still occur in this approach. Without quality, delivery capability cannot be guaranteed.

Optimized Machining Solution

1. Optimized Machining Sequence

The machining sequence is adjusted to:

• CNC1 (3-axis for front structure)
• CNC2 (4-axis for side structure)
• CNC3 (3-axis for reverse structure)

2. Reinforcing the Blank

Three reinforcing ribs are added inside the hollow cavity of the blank, forming a bridge-type connection structure to provide strong support during external machining.

3. Pre-Drilled Fixture Hole

To provide a tie-rod tensioning position for the cylinder fixture, a gourd-shaped hole is pre-drilled at the centre of the blank, which also improves the automation level of fixture lifting operations.

4. Secure Part Separation

After CNC3 completes the reverse-side machining, the fixture’s red-marked surface provides positioning and inward support points distributed around the circumference.

When the workpiece needs to be separated from the blank, two cylinders operate: one holds the scrap area while the other supports the finished part. This ensures the finished part does not move and the tool is not damaged by the scrap during separation.

5. Improve Production Efficiency

The machining operations originally performed on the 3+2 five-axis machine are now divided between CNC1 (three-axis) and CNC2 (four-axis). This significantly improves small-batch delivery capacity, with daily output reaching 300% of the previous level.

Thin-walled structural components are challenging to process due to their low rigidity and sensitivity to vibration. With diverse geometries, each part often requires a custom approach.

By integrating profile optimization, process planning, and fixture design, this article shares a practical solution that ensures both machining quality and reliable small-batch delivery.

WayKen offers CNC machining services for metal and plastic components, including thin-walled structures. Through advanced equipment, optimized processes, and strict quality control, our team ensures accuracy and consistency, helping customers move smoothly from prototyping to small-batch production with dependable results.