Silicone is an elastic material, and dimensional results are affected by shrinkage, demolding, curing time, and measurement methods. Appropriate tolerances should be established based on functional dimensions, rather than setting all dimensions to very tight tolerances.
1. Distinguish Between Key Dimensions
Dimensions related to sealing, assembly, and button travel should be prioritized; tolerances for non-functional geometric features may be appropriately relaxed.
- Identify key features and reference points on the drawing
- Specify whether to measure the free state or the compressed state
- Avoid conflicting multiple dimensional constraints
2. Consider Shrinkage and Deformation
Shrinkage behavior varies depending on hardness, cross-section, and mold design; it should be verified using trial mold data.
- Allow for compensation in structures with significant variations in thickness
- For long parts, account for shrinkage after demolding
- After the sample has been left for the specified time, proceed with the formal measurement.
3. Define the measurement method
The pressure and positioning method of the measuring tool can significantly affect the readings on the soft rubber gauge.
- Use fixtures and probes suitable for soft rubber
- Specify the measurement locations, frequency, and environmental conditions
- For complex contours, jigs or image-based measurement can be used.
4. Mass Production Control
Dimension control must be integrated with mold maintenance and process trend management.
- First-piece inspection for critical dimensions and multi-cavity consistency
- Create Rules for Dimension Trends and Anomaly Responses
- Assessing the Ripple Effects on Other Dimensions Before Mold Modification
FAQ
1. Can silicone parts meet the same tolerance levels as metal parts?
The accuracy of critical local dimensions can be improved through design and process control, but material elasticity and mass-production stability must be taken into account.
2. What should I do if tolerances aren't specified on the drawings?
Key dimensional requirements should be specified before submitting a quote or producing a sample to avoid discrepancies in the criteria for acceptance between both parties.