In high-precision manufacturing fields such as automobile chassis processing and stainless steel sheet metal processing, the quality of each product directly affects the safety and service life of terminal equipment. As a purchaser, how to control quality risks in the entire production process of sheet metal parts? This article provides a practical guide for purchasers from the disassembly of the quality inspection process to the actual pitfall avoidance strategy.

The whole process of quality inspection of sheet metal parts: “Five lines of defense” from raw materials to finished products

The quality inspection of sheet metal parts is not only “looking at the appearance” at the finished product stage, but must run through the entire production process. Taking Zhu Xi sheet metal bending processing company Christian Machinery as an example, the complete quality inspection process is usually divided into the following five stages:

1. Raw material inspection

Material quality is the basis of sheet metal processing. For stainless steel sheet metal processing, key inspections are required:

• Material authenticity: Use a spectrometer to verify whether the stainless steel grade (such as 304, 316) meets the requirements;
• Surface defects: Check whether the sheet has scratches, rust spots or oxide layers;
• Thickness tolerance: Use a micrometer to measure the thickness of the sheet, and the deviation must be controlled within ±0.05 mm.

2. Process monitoring

In key processes such as sheet metal stamping and sheet metal riveting, process parameters need to be monitored in real time:

• Pressure of stamping die: Regularly check die dimensions to avoid hole displacement due to wear;
• Riveting force control: Ensure that the strength of riveted points meets the standard through pressure sensors (such as automobile chassis parts need to withstand a tensile force of, ≥500 N);
• Laser welding penetration detection: Use an industrial endoscope to check whether the weld is uniform and free of bubbles.

3. Sampling inspection of semifinished product dimensions

For complex structural parts such as sheet metal chassis processing, key dimensions need to be sampled after bending and welding:

• Three-dimensional scanning comparison: Compare 3D data of semifinished products with design drawings, and parts with tolerances exceeding ±0.2 mm need to be reworked;
• Assembly pre-test: Simulate finished product assembly to verify hole matching and gap uniformity.

4. Surface treatment acceptance

Surface processes such as spraying and electroplating directly affect the product life and appearance:

• Salt spray test: Stainless steel sheet metal parts must pass a 48-hour neutral salt spray test, and no red rust is qualified;
• Coating adhesion: Use a hundred-grid knife to scratch the coating, and the shedding area is ≤5% to meet the standard.

5. Final inspection and packaging protection

Full-item inspection is required at the finished product stage, and the packaging method is standardized:

• Functional test: For example, the grounding resistance of the chassis parts must be ≤0.1 Ω;
• Shockproof packaging: Use EPE foam or customized blister trays to avoid transportation bumps.

Four core strategies for procurement risk avoidance

Strategy 1: Establish a “quality agreement” in advance

During the contract signing stage, clarify the quality inspection standards and responsibilities:

• Quantitative acceptance indicators: For example, the burr height of sheet metal stamping parts is ≤0.1 mm, and the bending angle tolerance is ±1°;
• Agreed terms for handling unqualified products: including rework costs and compensation plans for batch problems.

Strategy 2: Make good use of third-party testing tools

For purchasers who lack professional testing capabilities, third-party tools can be used:

• Portable hardness tester: quickly test the surface hardness of stainless steel sheet metal parts (HV ≥ 200);
• Industrial microscope: observe whether the microstructure of the sheet metal riveting point is dense and crack-free;
• Cooperating third-party laboratories: entrust professional testing such as X-ray flaw detection and metallographic analysis.

Strategy 3: Lock in high-quality supplier resources

Choosing experienced sheet metal processing service providers can greatly reduce quality risks. Taking Chuntian Machinery as an example, its three major advantages accumulated over 20 years of processing experience:

• Process database: pre-compensation technology for bending rebound coefficients of different materials (such as aluminum alloys and galvanized steel sheets);
• Flexible production line: supports small batch and multi-variety orders to avoid shrinking quality inspection processes due to rush work;
• Full process traceability: traceability from raw material batches to processing equipment parameters, which is convenient for quality problem analysis.

Strategy 4: Implement the “segmented acceptance” mechanism

Split large orders into multiple production batches:

• First piece acceptance: Full inspection of the first batch of 20 pieces to verify process stability;
• Process sampling: Randomly select 5% of samples from each batch to re-test key dimensions;
• Final piece sealing: Keep the last piece as the quality inspection benchmark for subsequent orders.

The quality risk control of sheet metal parts is essentially the technical consensus and collaboration between the purchaser and the supplier. By standardizing the quality inspection process, making good use of testing tools, and choosing service providers with technical accumulation such as Chuntian Machinery, the purchaser can not only avoid risks, but also promote the overall quality upgrade of the supply chain. In the increasingly competitive manufacturing industry, only by changing quality control from “passive inspection” to “active prevention” can we achieve real cost reduction and efficiency improvement.