Din 16742 - Tg5 Today

It replaced the older standard. While DIN 16901 was designed heavily around thermoplastics and specific shrinkage behaviors, DIN 16742 encompasses a broader range of plastic materials, including thermoplastic elastomers and thermosets, acknowledging that plastics possess different shrinkage and stiffness characteristics than metals. Key Aspects of DIN 16742:

The standard differentiates between two types of dimensions:

falls in the middle of the standard spectrum, situated between the highly precise lower groups (TG1–TG3) and the looser, general-purpose higher groups (TG6–TG7).

When designing plastic injection-molded parts, achieving perfect dimensional accuracy is impossible due to inherent material shrinkage and process variables. To bridge the gap between design intent and manufacturing reality, engineers rely on standardized tolerance systems.

The seamless fit of a smartphone chassis, internal camera lens holders, and laptop hinge mechanisms frequently leverage TG5 tolerances to achieve a premium tactile feel and environmental sealing. 6. Challenges and Best Practices for Implementation din 16742 - tg5

For verification, a clear measuring concept must be defined, which is particularly important for dimensionally unstable parts. Aspects to consider include functional orientation, reference system, gravitational influence, and pre-tensioning.

The primary technical feature of TG5 is that it does not use a single percentage for all dimensions. Instead, it splits tolerances into and Non-Functional Dimensions (N) :

Plastic parts undergo significant physical transformation during manufacturing. As molten polymer cools within a mold, it experiences thermal contraction, crystallization, and volumetric change known as .

| Nominal Size Range (mm) | Limit Deviation (± mm) | | :--- | :--- | | 1 - 3 | 0.12 | | >3 - 6 | 0.18 | | >6 - 10 | 0.22 | | >10 - 18 | 0.26 | | >18 - 30 | 0.31 | | >30 - 50 | 0.37 | | >50 - 80 | 0.57 | | >80 - 120 | 0.80 | | >120 - 250 | 1.05 | It replaced the older standard

DIN 16742 is a German standard (adopted internationally as ISO 20457) that defines general tolerances for plastic molded parts. Unlike metal parts, which can be specified using standardized fit systems, plastic parts require a unique system due to material behavior like shrinkage, warpage, and moisture absorption.

DIN 16742 classifies tolerances into nine distinct groups, labeled .

For technical guidance on applying this standard, designers often use tools like the PolTolerances Software

If you need the official DIN 16742 document, purchase it from (Germany) or your national standards body. For most practical engineering work, the above TG5 values are sufficient for drawing notes and supplier communication. the tolerance group system

Or, to combine:

Unlike metal machining tolerances (which are largely linear), plastic cooling involves volumetric shrinkage, anisotropic orientation, and thermal contractions. DIN 16742 accounts for these complexities by categorizing production factors into ranging from TG1 to TG9. Deconstructing the TG5 Classification

2. Non-Tool-Fixed Dimensions (Nicht werkzeuggebundene Maße)

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