DIN 16742 Tolerance Grades

Material Categorization

Groups of resins are assigned to specific tolerance classes based on their stiffness and their tendency to shrink. Amorphous materials like polycarbonate often achieve tighter tolerances than semi-crystalline materials like polypropylene because they have more predictable shrinkage patterns. The standard provides tables that correlate the part size with the expected deviation, ensuring that expectations are grounded in the physical reality of the material.

Moulding Precision

Production variables such as tool temperature and injection pressure directly influence whether a part meets the specified grade. A molder must maintain a stable process window to ensure that every shot stays within the narrow limits of a high-precision grade. Frequent monitoring and calibration of the equipment are required to prevent the dimensions from drifting as the tool heats up over time.

Tolerance Boundary

Requirements that exceed the tightest grades in the standard often lead to higher scrap rates and tooling costs. While a designer might desire extreme precision, the standard shows where the cost of achieving it becomes prohibitive for mass production. Most commercial projects settle on a medium grade that balances functional requirements with manufacturing efficiency.