Range of dimensional tolerances

ISO 3302-1 defines the tolerance classes and their values for molded, extruded, and calendared rubber products. The document also specifies the appropriate testing procedures and methods necessary to determine compliance with this standard. The tolerances outlined in ISO 3302-1 primarily apply to vulcanized (cured) rubber as well as products made from thermoplastic rubber. It should be noted that this international standard does not apply to, among other things, toroidal sealing rings or calendared composite products (e.g., rubber-coated fabrics).

Extruded Products
Rubber swells and shrinks during the vulcanization (curing) process, leading to deformation. For these reasons, extruded rubber products require wider production tolerances than molded parts. During molding, elastomers shrink to varying degrees depending on factors such as material used, molding method, and product geometry. Final dimensions are also influenced by the processing method, temperature during processing, and moisture content. Using supports during the curing process can help reduce deformation of rubber parts during extrusion.

Below are three tolerance classes for nominal dimensions of the cross-sections of extruded parts without support:

Class E1 – High Quality
Class E2 – Good Quality
Class E3 – Acceptable Quality

The tolerance class depends on the application in a given use. Class E1 and E2 require more production effort and finishing. For some synthetic rubbers, there is no E1 tolerance class.

Class E1
Class E1: Accuracy level – Good. Requires profiles meeting the Class E1 tolerance.

• High-precision spray nozzles

• Precisely coordinated and repeatable extrusion speeds

• Very rapid curing after the rubber compound exits the spray nozzle

• Large quantities and close coordination of tolerances between the client and the supplier are required

Class E2
Class E2: Accuracy level – Medium. Requires profiles meeting the Class E2 tolerance.

• Precise spray nozzles

• Medium extrusion speeds

• Fast vulcanization process after the rubber compound exits the spray nozzle

• Medium to large quantities required

Class E3
Class E3: Accuracy level – Rough/Approximate. This class is now almost unused and serves mainly as a basis for profiles.

• Small production quantities and large wall thicknesses

Dimensional tolerances according to ISO 3302-1

  In the appendix, a table showing the relevant tolerance ranges  

  Tolerances are used for individual rubber products:

• rubber o-rings that you can buy here:/en/rubber-o-rings
• Rubber cords which you can buy here:/en/rubber-cord-adhesive
• rubber seals, the production of which is dedicated here: /en/contact