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Engineering Plastic Quality Control: Inspection Methods & Testing Equipment
Quality control is the backbone of engineering plastic manufacturing. Without rigorous QC, material properties vary between batches, leading to part failures and production delays.
Three Levels of QC
Level 1: Incoming Raw Material
· Density verification (ASTM D792)
· Melt flow index (ASTM D1238)
· Visual inspection for contamination
· Moisture content (critical for PA66)
· Supplier CoA review
Level 2: In-Process QC
· Temperature and pressure monitoring
· Periodic dimensional checks (thickness, diameter)
· Surface inspection (blisters, contamination)
· Density of finished product
Level 3: Final Inspection
· Dimensional verification against tolerances
· Mechanical property testing (tensile, flexural, impact)
· Visual inspection per AQL sampling
· Material Test Report (MTR) and Certificate of Conformance (CoC)
Key Testing Equipment
Test | Equipment | Standard |
Tensile | Universal testing machine | ASTM D638 |
Flexural | UTM with flex fixture | ASTM D790 |
Impact | Pendulum impact tester | ASTM D256 |
Thermal (DSC) | DSC instrument | ASTM D3418 |
HDT | HDT/Vicat apparatus | ASTM D648 |
Surface resistivity | Megohmmeter + electrode | ASTM D257 |
Density | Analytical balance | ASTM D792 |
AQL Sampling
Batch Size | Sample Size | Accept/Reject |
≤ 50 | 5 | 0/1 |
51-150 | 8 | 0/1 |
151-500 | 13 | 1/2 |
501-1200 | 20 | 1/2 |
Standard AQL: 1.0 for stock shapes. Critical applications: 0.65 or 0.25.
Documentation
Material Test Report (MTR)
Material grade, batch number, test results, standards used, inspector signature.
Certificate of Conformance (CoC)
Customer name, PO number, material description, quantity, ISO 9001 reference.
How to Verify Supplier QC
1. Request MTR and CoC with every shipment
2. Ask for QC procedures documentation
3. Visit factory or arrange third-party audit
4. Request retained samples for independent testing
5. Check equipment calibration records
FAQ
Q1: What QC tests are performed?
Dimensional inspection, mechanical testing (tensile, flexural, impact), thermal testing, electrical testing, physical testing.
Q2: What is an MTR?
A document recording all test results for a specific batch — properties, standards, pass/fail criteria.
Q3: How to verify supplier QC?
Request MTR/CoC, review QC procedures, audit factory, request samples for independent testing.
Ready to source quality engineering plastics? Contact NAGOMER today for a free quote, or browse our PEEK sheets, POM rods, and ESD materials.
NAGOMER — Professional Engineering Plastics Solutions
www.nagomer.com | info@nagomer.com