(e.g., PP, PE, PA66) have high, directional shrinkage.
The PDF of this standard, particularly its essential tolerance tables, is more than just a document—it is a quality assurance tool that:
The standard uses a to define tolerance grades:
| Nominal size (mm) | PT3 (Fine) | PT5 (Medium) | PT7 (Coarse) | |------------------|------------|--------------|---------------| | up to 10 | ±0.10 | ±0.25 | ±0.50 | | 10 – 25 | ±0.15 | ±0.35 | ±0.70 | | 25 – 63 | ±0.20 | ±0.45 | ±0.90 | | 63 – 100 | ±0.30 | ±0.60 | ±1.20 | | 100 – 160 | ±0.40 | ±0.80 | ±1.60 | iso 20457 tolerance table pdf
Injection pressure, melt temperature, hold time, and cooling channel layouts alter the rate at which the polymer chains pack and solidify inside the tool cavity. Best Practices for Using ISO 20457 in Design
Years later, Ana stood at the same bench where she'd first opened the old PDF. The shop had grown into a small factory with apprentices, CAD stations, and a quiet floor where machines hummed in coordinated rhythm. On the wall, framed under glass, was a clean reproduction of the tolerance table—this time accompanied by handwritten notes: material pairings, preferred surface finishes, and a list of clients who depended on that sheet for their lifetimes of service.
If you are currently setting up a production run, I can help you determine exactly which tolerance group fits your specific material and design constraints. The shop had grown into a small factory
is the international standard for manufacturing tolerances of molded plastic parts . It replaces the older DIN 16742 standard and provides a system to determine achievable tolerances based on the material properties and production process. ISO 20457 Tolerance Table (TG6 Example)
On a spring morning, as apprentices filed in and sunlight slanted through new windows, Ana handed a young machinist a fresh printout. "Learn this," she said. "But don't worship it. Use it to talk to people, to fix things, to make promises you can keep." The apprentice smiled and traced a column, feeling the same hush Ana had felt years before. Outside, delivery trucks rolled in and out. Inside, each tiny part they made slid into place within those invisible allowances, and the world—complicated, imprecise, human—ran a little smoother because someone had read the numbers and decided to make them mean something.
These tolerances apply to dimensions that are influenced by factors outside of the mold cavity itself. and the world—complicated
: The definitive source to purchase and download the official ISO 20457:2018 PDF for full compliance.
For flatness, ISO 20457 provides standard tolerances based on overall part dimensions: