ISO 20457:2018 is the primary international standard for determining manufacturing tolerances and acceptance conditions for plastic molded parts. It replaces the older

and provides a structured approach to tolerancing based on material properties and manufacturing complexity. Super-Ingenuity Core Tolerance Framework The standard uses Tolerance Grades (TG)

and precision classes to define allowable deviations. A critical requirement is that a callout must include the grade and environmental conditioning (e.g., ISO 20457–TG6 + 23°C/50%RH ) to be enforceable. Super-Ingenuity Tolerance Categories (Materials)

: Materials are categorized (typically Categories 1–4) based on their shrinkage properties. Precision Classes Class A (High Precision)

: Reserved for specialized applications like medical devices or optical components requiring extreme accuracy. Class B (Medium Precision)

: The industry standard for most technical plastic parts with moderate fit requirements. Class C (Low Precision)

: Used for non-critical, general-purpose applications where loose tolerances are acceptable. How to Use the Tolerance Tables

To find a specific tolerance value, users follow a multi-step process often detailed in reference PDFs: Identify Material : Determine the specific plastic being molded. Determine Category : Look up the material in a provided table to find its Tolerance Category based on shrinkage. Select Tolerance Grade

: Cross-reference the category with the nominal dimension of the part to find the specific deviation (in mm). Implementation and Resources Official Standard : Detailed specifications are available directly from the ISO 20457:2018 Publication Page Working Templates : For practical engineering use, Super-Ingenuity

offers downloadable 2D tolerance note blocks and Excel-based quality report templates. Quick Reference PDFs : Manufacturers like OKW Enclosures provide summarized PDF guides that illustrate how is applied to common thermoplastics. Comparison : While ISO 20457 is for molding, standard

is typically applied if those molded parts are subsequently machined. OKW Gehäusesysteme specific materials

like ABS or Polypropylene are categorized under this standard?

ISO 20457 is the current international standard for determining manufacturing tolerances of plastic molded parts. It replaces older standards like ISO 8062 and is closely aligned with the German DIN 16742. This standard is vital for designers and manufacturers to agree on achievable precision without driving up costs through unnecessary accuracy requirements. Key Tolerance Groups (TG)

Unlike metal parts, plastics have high shrinkage and warpage, requiring specific "Tolerance Groups" (TG) based on material properties and manufacturing effort.

TG4 (Fine): Used for high-precision components like internal gears or small medical parts. TG5 (Medium): Typical for functional housing parts.

TG6 (Coarse): Standard for non-critical consumer products or packaging. ISO 20457 Tolerance Table Overview

The following table provides general capability ranges based on the part's nominal dimensions (size) and the selected tolerance grade: Nominal Dimension (mm) TG4 (Fine) TG5 (Medium) TG6 (Coarse) Up to 1 mm 1 to 3 mm 3 to 6 mm 6 to 10 mm 10 to 18 mm 18 to 30 mm 30 to 50 mm 50 to 80 mm 80 to 120 mm 120 to 180 mm 180 to 250 mm Critical Requirements for ISO 20457 Callouts

Simply stating "ISO 20457" on a drawing is insufficient. For a tolerance to be enforceable, the design documentation must include:

Tolerance Grade (TGx): Specifying the exact group (e.g., TG6).

Conditioning: Standard measurement temperature (usually 23°C) and humidity (50% RH).

Measurement Method: Specifying tools like a CMM (Coordinate Measuring Machine) or Optical Measurement Systems.

Datum System: Clear reference points to ensure repeatable results. Why ISO 20457 vs. ISO 2768?

The ISO 20457:2018 standard, which replaced DIN 16742, defines the tolerances and acceptance conditions for plastic molded parts. It uses Tolerance Groups (TG) to classify accuracy based on material properties and manufacturing processes. Key Tolerance Group: TG6

TG6 is a common baseline for thermoplastic injection molding. Below is a summary of the general tolerances for this group: Nominal Range (mm) Tool-Specific (W) (± mm) Non-Tool-Specific (NW) (± mm) 1 to 3 3 to 6 6 to 10 10 to 18 18 to 30 30 to 50 50 to 80 80 to 120 Source: Derived from OKW-Tolerances-en (PDF). Tolerance Determination Process

Interpreting the Tolerance Table: A Practical Example

Let us extract a typical row from the ISO 20457 tolerance table (PT2 – fine grade for a dimension not affected by parting lines).

Nominal size range: 100 mm to 200 mm PT2 tolerance: ±0.30 mm

Compare this to ISO 286 for metal (IT7 grade for 100–200 mm: about ±0.035 mm). The plastic tolerance is nearly 10x wider. This illustrates the core lesson of ISO 20457: Do not over-specify plastics.

The full table includes separate columns for:

• Dimensions unaffected by tool construction (e.g., wall thickness between two fixed cores)
• Dimensions across a parting line (half the tolerance on each side, with additional allowance for mismatch)
• Dimensions involving moving cores (slide-action features)

Unlocking Precision: The Ultimate Guide to the ISO 20457 Tolerance Table PDF

In the world of manufacturing and mechanical engineering, precision is not just a goal—it is a language. When two parts from different suppliers in different countries must fit together perfectly, engineers rely on a standardized vocabulary of tolerances. One of the most critical, yet often overlooked, documents in this domain is ISO 20457.

If you have been searching for the "ISO 20457 tolerance table PDF," you are likely looking for a clear, actionable reference for geometrical product specification (GPS) and verification. This article serves as your complete resource. We will explain what ISO 20457 is, why the tolerance table matters, how to interpret it, and where to find legitimate PDF versions.

6. How to Read the PDF Tables

If you are looking at an ISO 20457 PDF, you will see columns labeled:

1. Nominal Dimension ($d_n$ or $e_n$): The named size (e.g., 110mm).
2. Average OD ($d_em$): The measured mean diameter.
3. Min/Max OD: The allowable limits.
4. Out-of-roundness (OoR): The maximum ovality allowed.

Limitations and Practical Advice

While the ISO 20457 tolerance table is a powerful tool, it is not a universal solution. The PDF document makes clear that general tolerances are default values. They apply only when no individual tolerance is specified. For features that require a precise fit (e.g., a bearing housing or a gear shaft center distance), the designer must still assign explicit, tighter tolerances. Furthermore, the standard does not cover every geometric characteristic—profile tolerances (for curved surfaces) are notably absent, as are tolerances for free-form surfaces.

For practical use, one should obtain the official ISO 20457:2018 document from an authorized standards provider (e.g., ISO, ANSI, or national bodies like BSI or DIN). Many educational summaries and “cheat sheets” exist online, but only the official PDF contains the complete, legally authoritative tables. The tables in the standard are the final reference for any quality control dispute.

Step 1 – Identify the Feature Category

Your drawing must classify each dimension using ISO 20457’s three categories:

• Category A: Both sides of the dimension are in the same mould half (fixed or moving). Easiest to hold.
• Category B: Dimension crosses the parting line. Tolerance must be wider due to mould locking and ejector plate variations.
• Category C: Involves a side-action core (cam, lifter, unscrewing device). Widest tolerance because of moving mechanical elements.

A. Material Groups

The tolerances vary depending on the material, as different plastics shrink and mold differently. The standard generally divides materials into groups:

• Group 1: Materials with low shrinkage (e.g., PVC-U, PVC-C).
• Group 2: Materials with higher shrinkage (e.g., PE, PP, PVDF).
• Group 3: Specific materials requiring special consideration (e.g., PE-X).

Finding the Document

It is important to note that ISO standards are proprietary documents. While you may find snippets or summaries online, obtaining the official, complete ISO 20457 tolerance table PDF generally requires purchasing the standard from:

• The ISO Webstore (iso.org).
• Authorized resellers such as Techstreet or IHS Markit.
• National standardization bodies.

Using the official document ensures that the data you are using is up-to-date, as standards are periodically reviewed and updated to reflect new technologies and industry practices.