Many customers are doing silicone products for the first time. When they receive the drawings, they think they are reasonable. But when they start the prototyping, problems arise: incorrect dimensions, deformation, tearing, and inability to fit.
It's not that the customers' designs are bad; it's because silicone materials are different from plastics and metals. Using the design approach for plastics for silicone can sometimes lead to omissions in certain areas.
Today, we have compiled the 5 most important points to pay attention to in silicone product design. If you are preparing to develop silicone products, it is recommended to read this before sending the drawings.
1. Uniform wall thickness
Common situation: Some parts of the product are thick while others are thin, with a significant difference in thickness.
Why it needs attention: Silicone will shrink during the molding process, and the shrinkage rate is related to the wall thickness. The thicker areas shrink more, while the thinner areas shrink less. If the wall thickness difference is too large, the product will deform, warp, and have unstable dimensions. In severe cases, there may even be shrinkage depressions in the thick areas.
Suggestion: Try to keep the wall thickness uniform. The wall thickness of conventional silicone products is usually between 1-3mm. If structural changes are necessary, make gradual transitions instead of suddenly thickening or thinning. The ratio of thickness should be controlled within 2:1 at most.
2. Avoid right angles and sharp corners
Common situation: The edges of the product are all right angles, or there are very sharp corners.
Why it needs attention: Silicone is prone to stress concentration at sharp corners. When subjected to force, the sharp corner area will tear first. The processing of sharp corners in the mold is troublesome, and the electrode wear is fast. The sharp corners are prone to wear, and the mold life is short.
Suggestion: Try to use R-shaped transitions for all corners. The R-shaped angle should be at least 0.5mm, preferably 1mm or more. If it is a stressed area, the R-shaped angle should be even larger. The round corner not only makes the product more durable but also makes the mold easier to process.
3. Consider demolding in advance for inverted designs
Common situation: There is an inverted design on the product, but no consideration was given to how to remove it from the mold.
Why it needs attention: Silicone is a soft material. Small inverted designs can be easily removed by force. But if the inverted design is too large or deep, forcibly removing it will cause the product to tear. If a sliding block structure is used, the mold cost will increase significantly, and the production cycle will also be longer.
Suggestion: Before designing the inverted design, communicate with the factory. Have the engineer evaluate: Can this inverted design be forcibly removed? Will forcibly removing it tear the product? If it must be a sliding block, how much will the cost increase? Communicating in advance is much more convenient than making changes after the mold is made.
4. Reasonable tolerance requirements
Common situation: There are many ±0.05mm tolerances marked on the drawings, thinking that the more precise, the better.
Why it needs attention: Silicone has a shrinkage rate, usually between 1%-3%. Affected by temperature, pressure, and formula, the shrinkage of each batch will fluctuate. Marking ±0.05mm means the mold needs to be extremely precise, and production must strictly control every variable. The yield rate is low, the cost is high, and the delivery period is unstable.
Suggestion: Distinguish between critical dimensions and non-critical dimensions. For dimensions that affect assembly, the tolerance can be set more strictly, such as ±0.1-0.2mm. For dimensions that do not affect, relax it to ±0.3-0.5mm or even wider. If unsure, inform the factory engineer of the product's usage to have them help you set reasonable tolerances.
5. Clear surface treatment requirements
Common situation: Just say "smooth" or "good-looking", without specifying the surface effect.
Why it needs attention: There are many surface effects for silicone: smooth, matte, frosted, hand-sprayed oil, screen printing, laser engraving. Different effects require different mold surface treatments and post-processing procedures. Without clarification, the product may not be what you want. One rework attempt will waste time and cost.
Suggestion: Try to provide physical samples or reference pictures. If it's not available at the moment, clearly describe the effect you desire: is it a glossy finish or a matte finish? Does it feel smooth or rough to the touch? Do you want to apply a hand lotion? Do you want to have the text printed or engraved? Make these details clear so that the factory can get it right.