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Thermally molded elastomers are dependent on the following factors:
- ✓ Compound variation
- ✓ Mold tolerance
- ✓ Shrinkage
- ✓ Mold registration
- ✓ Temperature
- ✓ Cure time
Shrinkage could arise on elastomers depending on the following factors:
- ✓ Tool design
- ✓ Shape
- ✓ Material
- ✓ Molding
To account for the variables that are included in the manufacturing process, it is vital to define tolerances. This can help achieve the required level of precision and quality.
ISO 3302-1
1) ISO 3302-1 states the various classes of tolerances and their values for molded, extruded, and solid rubber products. The applicable test methods required for complying with ISO 3302-1 are also defined.
2) Note that the tolerances are mainly intended for vulcanized rubbers. However, they may be suitable for thermoplastic rubbers as well.
Measurement
3) Four tolerance classes ranging from M1 to M4 are defined. Based on the press direction of the mold, differences are calculated between the mold dimensions and the two-component adhesion system measurements of the mold closure.
Tolerance Classes
1) M1 (Precision Moldings) – Requires precision molds, close mix controls, and fewer cavities per mold. Measuring devices such as optical comparators may be needed to reduce distortion of the compound.
2) M2 (High-Quality Moldings) – Involves most of the close control needed for M1 class.
3) M3 (Good-Quality Moldings)
4) M4 (Non-Critical Dimensional Control Moldings)
Dimensional Tolerances
The dimensional tolerances defined in ISO 3302 could be wider than the ones used in certain engineering practices. Listed below are the following considerations:
1) When rubbers are cooled after molding, they will show some shrinkage. The amount of shrinkage depends on the mix used and elastomer type. However, it can vary from batch to batch.
2) Non-rubber fragments that are bonded to elastomers could affect the practicable tolerances and shrinkage.
3) Molds can be manufactured in different ways depending on the accuracy demanded and the product type. Also, if the degree of accuracy is greater, the molds and their maintenance will be more expensive.
4) Products that have a wide sectional variation will require more care in applying the standard tolerances.
5) During mold removal, if the rubber products are distorted, the dimensions may be affected, and a special allowance may be required.
Geometrical Tolerances
ISO 3302 defines geometrical tolerances for molded and extruded elastomer products, including the ones with metal inserts:
- ✓ Parallelism Tolerance
- ✓ Positional Tolerance
- ✓ Coaxial Tolerance
- ✓ Flatness Tolerance
- ✓ Perpendicularity Tolerance
Thermally molded elastomers are dependent on the following factors:
- ✓ Compound variation
- ✓ Mold tolerance
- ✓ Shrinkage
- ✓ Mold registration
- ✓ Temperature
- ✓ Cure time
Shrinkage could arise on elastomers depending on the following factors:
- ✓ Tool design
- ✓ Shape
- ✓ Material
- ✓ Molding
To account for the variables that are included in the manufacturing process, it is vital to define tolerances. This can help achieve the required level of precision and quality.
ISO 3302-1
1) ISO 3302-1 states the various classes of tolerances and their values for molded, extruded, and solid rubber products. The applicable test methods required for complying with ISO 3302-1 are also defined.
2) Note that the tolerances are mainly intended for vulcanized rubbers. However, they may be suitable for thermoplastic rubbers as well.
Measurement
3) Four tolerance classes ranging from M1 to M4 are defined. Based on the press direction of the mold, differences are calculated between the mold dimensions and the two-component adhesion system measurements of the mold closure.
Tolerance Classes
1) M1 (Precision Moldings) – Requires precision molds, close mix controls, and fewer cavities per mold. Measuring devices such as optical comparators may be needed to reduce distortion of the compound.
2) M2 (High-Quality Moldings) – Involves most of the close control needed for M1 class.
3) M3 (Good-Quality Moldings)
4) M4 (Non-Critical Dimensional Control Moldings)
Dimensional Tolerances
The dimensional tolerances defined in ISO 3302 could be wider than the ones used in certain engineering practices. Listed below are the following considerations:
1) When rubbers are cooled after molding, they will show some shrinkage. The amount of shrinkage depends on the mix used and elastomer type. However, it can vary from batch to batch.
2) Non-rubber fragments that are bonded to elastomers could affect the practicable tolerances and shrinkage.
3) Molds can be manufactured in different ways depending on the accuracy demanded and the product type. Also, if the degree of accuracy is greater, the molds and their maintenance will be more expensive.
4) Products that have a wide sectional variation will require more care in applying the standard tolerances.
5) During mold removal, if the rubber products are distorted, the dimensions may be affected, and a special allowance may be required.
Geometrical Tolerances
ISO 3302 defines geometrical tolerances for molded and extruded elastomer products, including the ones with metal inserts:
- ✓ Parallelism Tolerance
- ✓ Positional Tolerance
- ✓ Coaxial Tolerance
- ✓ Flatness Tolerance
- ✓ Perpendicularity Tolerance
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Speak with a human to filling out a form? call corporate office and we will connect you with a team member who can help.
