Dimensional tolerances depend on the (mm) of the feature. Below is a simplified table for TG5 (based on DIN 16742, general tolerances for non-critical dimensions):
[ Molten Polymer ] ──> [ High Pressure Injection ] ──> [ Volumetric Shrinkage & Cooling ] ──> [ Ejected Part ]
Plastics shrink as they cool. Amorphous polymers (like Polycarbonate or ABS) exhibit low, isotropic (uniform) shrinkage. They are ideal for TG5. Semi-crystalline polymers (like Polypropylene or Polyamide) exhibit high, anisotropic (non-uniform) shrinkage. They make achieving TG5 much harder unless reinforced with glass fibers. Tooling Quality and Construction
It strikes a realistic balance between strict functional design requirements and affordable manufacturing costs. din 16742 - tg5
Or, to combine:
| Nominal dimension (mm) | Tolerance ± (mm) | |------------------------|------------------| | 0 – 3 | ±0.08 | | 3 – 6 | ±0.12 | | 6 – 10 | ±0.15 | | 10 – 18 | ±0.20 | | 18 – 30 | ±0.25 | | 30 – 50 | ±0.30 | | 50 – 80 | ±0.40 | | 80 – 120 | ±0.50 | | 120 – 180 | ±0.65 | | 180 – 250 | ±0.80 | | 250 – 315 | ±1.00 | | 315 – 400 | ±1.20 |
DIN 16742 defines nine tolerance groups numbered from to TG9 (loosest) . Each TG corresponds to a specific basic tolerance grade (IT grade) according to DIN EN ISO 286-1, the international standard for limits and fits. Dimensional tolerances depend on the (mm) of the feature
Many molders hesitate to guarantee TG5 for three reasons:
: It is often specified for "hard" plastic components or multi-component parts where a more accurate fit is needed (e.g., snap-fits or bearing housings). Cost vs. Accuracy
Even for very small dimensions, a tolerance smaller than ±0.1 mm is generally not economically feasible for most injection moulding processes. They are ideal for TG5
Tolerances are highly constrained, often within
, which is the variation inherent to the finished molded part rather than the mold tool itself. Pekago Covering Technology Best Practices for Specifying DIN 16742 Indicate the Standard Clearly
Key characteristics include: