A brand owner wants r-PET for direct food contact. TG5’s highest grade (Premium) still does not guarantee food safety because migration testing is outside scope. The brand must layer TG5 with EFSA positive list requirements. Here, TG5 is necessary but insufficient.
To fully appreciate the role of Tg5, it is helpful to see how it sits within the broader tolerance hierarchy.
Elara’s blood went cold. “Which test?”
: The physical constraints of the mold (e.g., whether a dimension is formed by a single mold half or across a moving slide) significantly impact the achievable tolerance. Application and Measurement Standards To ensure a part meets the TG5 requirements, mandates specific inspection conditions: Conditioning : Measurements must be taken after 24–48 hours of conditioning in a climate-controlled room ( RH) to ensure the plastic has stabilized. Geometric Dimensioning & Tolerancing (GD&T) Iso 20457 Tg5
: Features like long thin walls or large flat surfaces increase warpage, making TG5 harder to maintain. Mold Design
The standard categorizes production accuracy into nine Tolerance Groups (TG1 to TG9):
ISO 20457 simplifies this by establishing a series of tolerance groups, ranging from NW (non-functional dimensions) to various TG (Tolerance Group) levels. These levels define the allowable dimensional variations based on the material characteristics and the production process. What is Tolerance Group 5 (Tg5)? A brand owner wants r-PET for direct food contact
Understanding where TG5 sits relative to other groups helps engineers avoid over-specifying tolerances, which increases production costs unnecessarily. Feature / Metric TG3 (Commercial) TG5 (Precision) TG7 (Ultra-Precision) Consumer goods, toys, housings Automotive sensors, medical gears Aerospace instrumentation, fiber optics Cost Profile Moderate Increase ( Exponential Increase ( Tooling Wear Impact Metrology Required Standard calipers / Micrometers CMM (Coordinate Measuring Machine) Optical / Vision measuring systems Design and Manufacturing Best Practices for TG5
Within the TG1 to TG9 spectrum, Tg5 occupies a central and highly valuable position. It represents a pragmatic "general purpose" tolerance, offering a balanced solution suitable for a wide range of standard applications where the extreme precision of finer grades (like TG4) is not required.
The standard divides manufacturing capabilities into nine distinct Tolerance Groups, labeled TG1 through TG9: Industrial and coarse tolerances. Here, TG5 is necessary but insufficient
Achieving TG5 requires total control over three main pillars of production:
Three years later, the first FAA-certified 3D-printed fuel nozzle flew on a Boeing 787 using TG5’s dynamic margin.
represents a specific accuracy class used to define allowable dimensional deviations based on the material properties and manufacturing process. Understanding ISO 20457 TG5 ISO 20457 (which succeeded
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