20457 Tg5 - Iso

Every polymer shrinks at a different rate. For example, semicrystalline plastics (like Polypropylene) shrink significantly more than amorphous plastics (like ABS). The toolmaker must scale the mold cavity larger than the desired final part to account for this shrinkage. Under ISO 20457, materials are classified into groups based on their shrinkage behavior. 2. Mold Flow Analysis

The most common tolerance groups for injection molding range from TG3 to TG9. The table below summarizes the typical applications for these groups: Iso 20457 Tg5

An automotive Tier 1 supplier switched to a "certified recycled talc-filled PP" for a non-visible bracket. The virgin material had an MFI of 12 g/10min. The recyclate arrived with an MFI of 45 g/10min (measured via standard ISO 1133). The molder assumed extreme degradation and scrapped the batch. Every polymer shrinks at a different rate

TG1 - TG3: Ultra-high precision (often reserved for specialized optical or medical components). TG4 - TG6: High precision to "Fine" engineering grades. Under ISO 20457, materials are classified into groups

: Look into the scope and objectives of the standard. This usually provides a good overview of what the standard aims to achieve.