Optimized Clamping Solutions for Batch Production: No Custom Fixture and Recyclable

Choosing the right process and fixture is key to ensuring product quality and production efficiency. This article is about a case study of CNC machining fixtures for a small, complex structural part, sharing how efficiency issues in machining and clamping were effectively resolved. It also offers a comprehensive analysis of the advantages, disadvantages, and applicability of various machining routes.

Product Background

The product is a drone component in the agriculture and forestry industry. The material used is AL7075 aerospace-grade aluminum, which offers higher hardness and strength than regular aluminum alloys. The surface treatment is sandblasting and anodizing. The production batch for this order is 2,000 pieces, which presents higher demands for the stability and efficiency of CNC machining.

Analysis of Product Structure

The product dimensions are 32×29×4.6mm, making it a small part with the following characteristics:

• Dimensional Tolerances: The most strict tolerance is ±0.05mm, with a parallelism requirement of 0.05mm.
• Threading Requirements: Three M2 thread gauges can function correctly, allowing passage when appropriate and stopping when necessary.
• Structural Features: The product has a semi-open structure with a thinnest area of only 2.84mm. If deformation occurs, it may exceed the parallelism tolerance requirements.
• Processing Requirements: For the batch of 2,000 pieces, a stable, efficient, and easy-to-operate processing route and fixture must be developed.

Different Process Route Comparison

In this section, we analyze three processing routes and compare their pros and cons.

General Process Route 1

The single workpiece is clamped on both its front and reverse sides separately and is processed in two operations.

Advantages

Simple process and easy to operate.

Disadvantages

• Material Waste: The product’s thickness is 4.6mm, with an additional 2 mm clamping thickness. Taking into account the available thickness specifications of the raw material, the nearest suitable thickness is selected. The final blank material thickness is 8 mm, leading to a large amount of waste material.
• High Labor Cost: Due to the small size of the product, the machine time per machining is short (first clamping estimated at 4.5 minutes, second clamping estimated at 0.6 minutes), requiring frequent part changes by the operator, resulting in high labor intensity and low machine utilization.
• Deformation Risk: The second clamping operation involves removing the connecting material sections, machined edge, and chamfering the hole. Typically, the conventional jaw-type fixture exerts a relatively high clamping force, which can cause deformation in the product. Additionally, the bottom surface of the product and the mating surface of the fixture may lift due to the clamping force, resulting in instability in parallelism and thickness dimensions.

General Process Route 2

Use the vacuum suction process and employ the same processing step as Route 1 for both the front and back sides, but adopt a multi-product parallel layout to produce.

Advantages

No issues with the first clamping operation, machining efficiency is improved, and waste material is reduced.

Disadvantages

When using vacuum suction in the second clamping process, due to the small size of the products, air leakage can occur when milling completely through the products. To prevent air leakage, a film can be applied to the bottom surface.

However, after putting the products on the plate, the hollowed-out gaps created by milling are too large, causing the film to wrinkle, which affects the flatness of the parts. Additionally, during removing the connecting material of the parts, displacement may occur, making the vacuum suction process unsuitable.

Optimized Process Route 3: Adopted in This Case

• Blank Size: 200×200×25mm
• First Clamping: Uses a saw blade to layer and cut the material. With one clamping, 27 layers (totaling 135 pieces) can be processed. Five pieces are processed side by side. The main structure on the front side could be machined in this step.
• Second Clamping: Utilizing a multi-position self-centering elastic fixture with contour-reversed positioning for finish machining on the reverse side, including planing and chamfering of the products.

Highlights of First Clamping

• Eliminating the need for fixture design and manufacturing, accelerating the project schedule.
• Using a saw blade to cut layers and separate materials allows for multi-piece processing with one clamping, significantly reducing part change frequently and enhancing production efficiency.
• Side-by-side processing shortens the single-layer processing time of the machine, improving machine utilization.

Highlights of Second Clamping

• Moderate Clamping Force: The self-centering contour-reversed locking device applies moderate clamping force, much less than that of traditional jaws. It can prevent clamping injuries or deformation of the product.
• Stability Verified: Measured and verified by WayKen’s engineering team, the parallelism of the product is between 0.02-0.03mm, and the thickness variation is less than 0.03mm, meeting the stability requirements for batch production.
• Continuous Processing: For high-volume machining, the fixture can be upgraded to an A/B interchangeable fixture system, allowing the A fixture to be processed in the machine while the B fixture is being loaded/unloaded outside, enabling continuous processing.
• Reusable Fixture: The second clamp fixture can be reused for similar products by simply replacing the self-centering components.

Conclusion

After several discussions, theoretical analysis, and pros/cons evaluations of various process routes at WayKen, this effective solution was ultimately chosen. A total of 2,000 pieces were processed with one machine running. This clamping process solution has provided a valuable reference for future similar products and accumulated valuable experience. We also hope that our experience can provide you with useful insights. If you have any questions or needs regarding machining, please do not hesitate to contact us.