ISO 20457 Tolerance Group 5 (TG5) is the industry-standard "baseline" precision level for plastic molded parts. It is typically used for general-purpose applications like housing parts and standard technical components where extreme precision is not required, but functionality must remain reliable. Key Characteristics of TG5
Baseline Precision: TG5 represents standard manufacturing accuracy for injection molding, sitting between high-precision groups (TG1–TG4) and coarse/loose groups (TG6–TG9).
Application Focus: Ideally suited for housing parts, enclosures, and general technical moldings.
Production Difficulty: Often classified under "Series 1" (Standard Production) or slightly tighter, meaning it can typically be achieved using standard injection molding processes without excessive specialized measures. How TG5 Fits into ISO 20457
ISO 20457:2018 (which replaced standards like DIN 16742) categorizes tolerances into nine groups (TGs) based on the required precision: Tolerance Group Description Typical Use Case TG1 - TG3 Extreme Precision Critical medical or optical components TG4 High Precision Gears, precision wheels, or high-speed impellers TG5 Baseline Precision Consumer electronics housings, standard covers TG6 Packaging, bottle caps, or simple pen barrels TG7 - TG9 Very Coarse High-shrinkage parts or rotational molding (e.g., TG9) Practical Considerations for Using TG5
Material Impact: Achieving TG5 is easier with low-shrinkage materials like ABS. For high-shrinkage materials like Polypropylene, reaching TG5 might require more precise process control.
Tooling Costs: Since TG5 is the baseline, it usually offers a good balance between part performance and manufacturing cost. Tighter groups like TG4 often incur a "significant surcharge" due to increased quality assurance and tooling precision.
Measurement Context: Tolerances in ISO 20457 are often defined as symmetrical limit dimensions (e.g., ±0.1 mm) rather than a total tolerance band.
Parting Lines: Be aware that dimensions crossing the tool's parting line (NW - Not tool-dependent) typically have wider tolerances than those contained within a single mold half (W - Tool-dependent).
ISO 20457 Tg5 refers to a specific "Tolerance Group" (TG) within the international standard for plastic molded parts. Specifically, TG5 is the baseline standard precision grade used for general-purpose industrial applications, such as housing parts and enclosures. What is ISO 20457?
ISO 20457, which replaced older standards like DIN 16901 and DIN 16742, defines the geometrical and dimensional tolerances for plastic molded parts. Unlike metal machining, plastic molding must account for unique variables such as material shrinkage, thermal expansion, and moisture absorption. Understanding the TG5 Classification
The standard categorizes production accuracy into nine Tolerance Groups (TG1 to TG9):
TG1 – TG3: Extreme precision (expensive and difficult to maintain). TG4: High precision (e.g., gears or precision wheels).
TG5: Standard Baseline Precision. This is the "default" for technical parts where fit and function are important but not microscopic.
TG6 – TG9: Coarse to very coarse (e.g., packaging or parts with high, unpredictable shrinkage). Key Components of an ISO 20457 Callout
Specifying "ISO 20457 Tg5" on a drawing is not enough to be legally enforceable. According to technical guides, a complete specification must include: Tolerance Group: e.g., TG5.
Conditioning: The environmental state (typically 23°C and 50% relative humidity) at which the part must be measured. Datum Scheme: The reference points used for measurement.
Inspection Method: Whether using a CMM (Coordinate Measuring Machine) or a manual fixture. Why Choose TG5? Iso 20457 Tg5
Using TG5 balances cost and quality. Tighter groups (TG1–TG4) significantly increase tooling costs and scrap rates because they require narrower process windows. TG5 provides sufficient accuracy for: Consumer electronics housings. Automotive interior trim. Medical device enclosures. Summary Table: ISO 20457 Tolerance Hierarchy Accuracy Level Typical Application Extreme Precision Optical components, micro-fluidics High Precision Gears, functional mechanical parts TG5 Standard Precision Industrial housings, technical components Packaging, disposable goods
For more detailed engineering data, you can view the official abstract on the ISO website or check the DIN ISO 20457 comprehensive guide.
The tolerance grade within the ISO 20457:2018 standard is a medium-to-tight precision classification used primarily for housing parts and functional components in plastic injection molding.
ISO 20457 is the modern international successor to the older DIN 16901 standard. It defines nine tolerance grades (TG1 to TG9), where is the tightest (highest precision) and is the loosest. Boyan Manufacturing Solutions Application of TG5
TG5 is often the "sweet spot" for technical plastic parts that require a reliable fit without the extreme costs of ultra-high precision molding. Common Use Cases
: Electronic enclosures, automotive interior trim, and structural housings. Comparison : Coarser; typically used for packaging.
: Finer; used for precision mechanical parts like small gears or wheels. Key Features of ISO 20457
Unlike older standards, ISO 20457 accounts for the physical reality that plastic parts accumulate more error as dimensions increase from a datum point. Boyan Manufacturing Solutions Tolerance Series : Tolerances are divided into two main categories: W (Tool-specific) : Dimensions formed by the same part of the mold. NW (Non-tool-specific)
: Dimensions affected by moving mold parts (like parting lines or sliders). Distance Dependent cap D sub p
(distance from a feature to the datum) to calculate position and profile tolerances, ensuring the values align with real shrinkage and warpage behavior. Acceptance Conditions (ABF)
: This standard includes specific rules in Chapter 8 for inspecting parts and handling deviations, which helps resolve disputes between manufacturers and customers. Boyan Manufacturing Solutions Factors Influencing TG5 Success Achieving TG5 consistently depends on several variables: Material Selection
: Low-shrinkage materials (like filled resins) make it easier to hit TG5 than high-shrinkage materials like Polypropylene. Part Geometry
: Features like long thin walls or large flat surfaces increase warpage, making TG5 harder to maintain. Mold Design
: Proper cooling and uniform wall thickness are essential for dimensional stability. Boyan Manufacturing Solutions
For specific numerical values for your part's dimensions, you can reference the full standard available through the or technical distributors like against the older classes to see how your legacy designs might transition? Go to product viewer dialog for this item.
International Organization for Standardization ISO 20457 2018 First Edition Plastics Moulded Parts
The parent standard, ISO 20457, outlines general principles for the recovery of plastic waste, including source separation, collection, sorting, and various recycling technologies (mechanical, chemical, and organic recovery). While comprehensive in scope, the standard inherently operates at a macro level. It advises what should be done but leaves significant ambiguity regarding how to verify the quality of sorted waste or ensure that a recycled pellet from one facility is functionally equivalent to that from another. ISO 20457 Tolerance Group 5 (TG5) is the
This is where TG5 enters the framework. Dedicated to Traceability and Quality Management of Recycled Plastics, TG5 addresses the weakest link in current recycling systems: information asymmetry. Recyclers often receive unknown, contaminated feedstocks, while converters reject recycled materials due to batch-to-batch variability. TG5’s work closes this gap by developing harmonized protocols for:
ISO 20457 TG5 is not a glamorous part of the plastics standardisation universe, but it is arguably the most commercially significant. It takes the messy, heterogeneous reality of plastic waste and imposes a structured quality language that markets, engineers, and regulators can trust. By focusing on measurable parameters—MFI, contaminants, odour, mechanical retention, and colour—TG5 transforms recycled plastics from a waste product into an engineered feedstock.
Yet, TG5 cannot work in isolation. Its voluntary nature, static grading model, and exclusion of food safety mean it is a necessary but not sufficient condition for a circular plastics economy. For TG5 to reach its full potential, it must be embedded in mandatory procurement policies, linked to digital traceability, and complemented by end-of-waste regulations. Ultimately, ISO 20457 TG5 exemplifies a profound truth: sustainability is not just about good intentions; it is about good specifications. Without the quiet rigour of TG5, the dream of a circular plastic economy remains a technical fiction. With it, recyclers, brands, and policymakers finally have a shared map to navigate from waste to worth.
References (Illustrative):
ISO 20457:2018 (which replaced DIN 16742) defines Tolerance Grades (TG)
specifically for plastic molded parts to account for the unique behavior of polymers compared to metals. Super-Ingenuity ISO 20457 TG5 Overview
classification represents a specific level of precision. In the ISO 20457 system, tolerance grades typically range from TG1 (most precise) TG9 (least precise) Super-Ingenuity Precision Level : TG5 is generally considered a high-precision grade
for industrial injection molding. It is often applied to functional parts where fit is critical but extreme "toolroom" precision (like TG1 or TG2) is not required. Key Requirements
: To enforce a TG5 callout, the technical drawing must include: Acceptance Temperature : Standard is typically 23°C. Measurement Humidity : Often 50% relative humidity. Datum System
: A defined inspection method (e.g., CMM or fixture) is necessary for repeatability. Super-Ingenuity Why TG5 Matters Cost vs. Accuracy
: Selecting TG5 implies a commitment to higher manufacturing costs compared to standard grades like TG6 or TG7. Tighter tolerances require more expensive tooling, tighter process controls, and more frequent quality assurance checks. Material Influence
: Not all materials can achieve TG5. Highly crystalline plastics with high shrinkage (like POM or PA) are harder to hold to TG5 than amorphous plastics (like PC or ABS). Manufacturing Method
: The standard covers various processes, including injection molding, compression molding, and rotational molding, though achieving TG5 is most common in precision injection molding. www.makrolar.eu Usage Tips Avoid Over-Specifying
: Only apply TG5 to dimensions critical for function. Using it as a "general tolerance" for non-critical features can unnecessarily inflate production costs. Verification : Check the ISO 20457:2018 Official Standard
for the exact numerical limits of TG5 based on your part's nominal dimensions. www.makrolar.eu Do you need the specific numerical tolerances
for a certain dimension under TG5, or are you comparing it to another grade?
ISO 20457 is the primary international standard for determining manufacturing tolerances and acceptance conditions for plastic moulded parts. Within this standard, Tolerance Group 5 (TG5) serves as the baseline for standard precision applications. Overview of ISO 20457–TG5 The Mandate of ISO 20457 and the Necessity
This grade is designed for parts where general dimensional accuracy is required without reaching the extreme costs of high-precision manufacturing.
Standard Precision Baseline: TG5 is considered the standard for most functional injection-moulded parts. While higher grades (TG1–TG4) are for extreme or high precision, TG5 balances manufacturability with cost-effectiveness.
Material Suitability: It is most consistently achieved using amorphous resins (e.g., ABS, PC), which have low and predictable shrinkage (0.4–0.7%). Semi-crystalline materials like Nylon (PA66) may require more careful process control to stay within TG5 limits.
Replacement of Older Standards: ISO 20457:2018 officially replaced older German standards like DIN 16742 and DIN 16901. Key Technical Requirements
To properly review or implement a TG5 callout, specific environmental and measurement conditions must be met to ensure valid results:
Conditioning Period: Parts must not be measured immediately after production. They require a stabilization period of 16 to 72 hours (typically 24–48 hours) at standard room temperature.
Standard Atmosphere: Measurement must occur in a climate-controlled environment of 23°C (±2K) and 50% (±10%) relative humidity.
Tool-Bound vs. Non-Tool-Bound: Tolerances vary based on whether a dimension is formed within a single tool part (W) or by the interaction of multiple tool parts (NW), with the latter typically allowing for larger variations. Comparative Ranking of Tolerance Groups Application Type Precision Level TG1 – TG3 Extreme precision Critical components (e.g., medical, aerospace) TG4 High-precision Critical-to-quality (CTQ) features like snap-fits TG5 Baseline Precision Standard functional applications TG6 Coarse precision Non-critical housings or loose-fit parts TG7 – TG9 Very coarse Highly unpredictable shrinkage materials Practical Review Tips
When reviewing a design specifying TG5, ensure the following callout is present on the technical drawing to avoid disputes:
"General tolerances per ISO 20457–TG5; Acceptance only after 24–48h conditioning at 23°C / 50% RH."
Are you looking to verify if a specific dimension on your part meets the TG5 standard based on its nominal size? TOLERANCES
Specifically, TG5 is responsible for Architecture and Terminology. This group lays the foundational framework that allows different intelligent transport systems (traffic lights, cars, navigation software, infrastructure) to "speak the same language" and operate cohesively.
Here is a comprehensive guide to understanding ISO 20457 TG5, its scope, and its importance.
The standard requires specific notation of whether the notch was cut "with skin" or "into core." Recycled parts have surface degradation; TG5 insists on reporting the "skin-core" morphology to avoid false positive impact results.
TG5’s primary output is a quality grading matrix that aligns recyclate properties with specific end-use applications. The key parameters defined by TG5 include:
Technical Group 5 (TG5) is a working group within the ISO/TC 204 committee. Its primary mandate is to maintain and develop standards related to the Reference Architecture and Terminology for Intelligent Transport Systems (ITS).
While "ISO 20457" is often cited as the umbrella for the group's work, the output of this group consists of several critical ISO standards (most notably the ISO 14817 series and ISO 14813 series). TG5 is essentially the "city planner" of the ITS world—they design the blueprints before the systems are built.