Silicone molding is a manufacturing process that transforms liquid or semi-solid silicone raw materials into elastomeric products with specific shapes and properties. It serves as the backbone of producing everything from daily necessities (e.g., kitchen utensils) to high-precision industrial parts (e.g., seals). But with multiple molding techniques available, how do you choose the right one for your project, and what key factors ensure success?
1. A Comparison of 6 Core Silicone Molding Methods
Different silicone molding techniques are designed for specific scenarios—from mass production to small-batch customization. The table below breaks down their core features, applications, and key controls:
| Molding Method | Key Features | Typical Applications | Critical Control Parameters |
| Compression Molding | High precision; suitable for complex structures; mass production | High-precision seals, automotive gaskets | Mold temperature (160–200°C), pressure (5–50MPa), vulcanization time |
| Injection Molding | High efficiency; low scrap rate; automated | Miniaturized parts (e.g., electronic buttons, conductive connectors) | Injection speed (staged control), mold vacuum exhaust, plasticization temperature |
| Extrusion Molding | Continuous production; equal-section profiles | Pipes, sealing strips, rubber hoses | Die design, barrel segmented heating, laser diameter monitoring |
| Gate Molding | Flexible; low-cost for small batches | Transparent crafts, mold prototypes, custom jewelry | Vacuum defoaming, layered infusion (for thick parts) |
| Coating & Impregnation | Thin, uniform coverage; adheres to substrates | Fabric coating, PCB waterproof films, biomedical coatings | Coating thickness, adhesion (grid test), centrifugation speed (for impregnation) |
| Special Molding | Innovative; solves complex needs | Cold runner: zero-waste parts; 3D printing-assisted: complex textures; Co-molding: silicone + metal/plastic inserts | Insulation (cold runner), resin type (3D printing), insert positioning (co-molding) |
2. Step-by-Step Guide to 3 Common Molding Processes
For beginners or those selecting a method, here’s a linear breakdown of three widely used workflows:
A. Compression Molding (Ideal for High-Precision Seals)
- Material Preparation: Weigh raw rubber, fillers, and vulcanizing agents per formula; mix evenly via a refiner.
- Plasticization: Reduce compound Mooney viscosity using the thin-pass method to improve plasticity.
- Preforming: Cut the compound into blanks that match the rough shape of the final product.
- Mold Vulcanization: Place blanks into the mold; heat and press in a flat vulcanizing machine (160–200°C, 5–50MPa).
- Post-Treatment: Trim excess material; conduct secondary vulcanization to remove volatiles and boost stability.
B. Injection Molding (Best for Miniaturized, Mass-Produced Parts)
- Feeding: Automatically feed granular or strip compound into the machine’s barrel.
- Plasticization: Heat the barrel to soften the compound (temperature varies by silicone type).
- Injection: Use high pressure to inject the softened compound into the closed mold cavity.
- Packing & Cooling: Maintain pressure until the compound is initially cured; cool slightly to set shape.
- Demolding: A manipulator automatically removes the finished product—no manual trimming needed for most designs.
C. Extrusion Molding (Great for Continuous Profiles)
- Die Design: Customize the die opening to match the product’s cross-section (e.g., round for pipes, rectangular for strips).
- Heating & Extrusion: Heat the barrel in segments (front: plasticization; middle: constant temperature; rear: forming); push compound through the die.
- Monitoring: Use a laser diameter gauge to real-time check product dimensions and adjust extrusion speed if needed.
- Traction & Cutting: Pull the extruded profile via a track system; cut it to the set length automatically.
3. Troubleshooting: Common Defects & Solutions
Even with proper process design, defects can occur. Below is a cause-and-effect guide to fix the most frequent issues:
| Defect Phenomenon | Root Cause | Practical Solution |
| Bubble Holes | Air trapped during mixing; gas released during vulcanization | Use vacuum defoaming before molding; adopt gradient heating for vulcanization (avoids sudden gas expansion) |
| Glue Shortage (Incomplete Filling) | Low silicone fluidity; insufficient glue injection volume | Increase injection pressure (for injection molding); optimize gate position to improve flow; preheat silicone slightly |
| Sticky Surface | Incomplete vulcanization; mold surface contamination | Extend vulcanization time or raise temperature; clean the mold with a solvent (e.g., isopropyl alcohol) before use |
| Dimensional Deviation | Uneven curing shrinkage; inconsistent mold temperature | Reserve a 1.5%–3% shrinkage allowance in mold design; ensure uniform mold heating (use temperature sensors) |
4. Material & Equipment Selection Guide
Choosing the right materials and equipment directly impacts product quality. Use this table to match your needs:
| Demand Scenario | Recommended Silicone Type | Supporting Equipment |
| Food-Grade Products (e.g., silicone spatulas) | FDA-certified liquid silicone | Vacuum casting equipment (avoids contamination) |
| High-Precision Seals (e.g., automotive oil seals) | Silicone with vapor-phase silica filler (boosts hardness) | Precision compression molding machine |
| Conductive Parts (e.g., electronic buttons) | Precipitation-method conductive silicone rubber | Vertical injection machine + static elimination device |
| High-Temperature-Resistant Parts (e.g., industrial pipes) | Phenyl silicone rubber (resists up to 300°C) | Extruder + laser diameter gauge |
5. Yigu Technology’s Perspective on Silicone Molding
At Yigu Technology, we see silicone molding as a driver of product innovation—not just a manufacturing step. For clients in healthcare, we’ve optimized coating molding to create biocompatible silicone films for medical devices, ensuring 99.8% adhesion and meeting global safety standards. For automotive clients, our compression molding process reduces seal defect rates to below 0.5% by refining temperature control and using high-purity fillers.
Looking forward, we’ll focus on two priorities: 1) Developing eco-friendly silicone materials that cut waste by 30% and 2) Integrating AI into injection molding to real-time adjust parameters, boosting efficiency by 20%. We aim to make silicone molding more sustainable, precise, and accessible for all industries.
FAQ
- Which silicone molding method is best for small-batch custom products (e.g., 50–100 units)?
Gate molding is ideal—it’s low-cost, flexible, and doesn’t require expensive molds. Use additive liquid silicone for high transparency (e.g., custom crafts) and vacuum defoaming to ensure quality.
- How to ensure food-grade safety in silicone molding for kitchenware?
First, select FDA-certified liquid silicone (no toxic additives). Second, use dedicated equipment (avoid cross-contamination with industrial-grade silicone). Third, conduct post-production tests (e.g., leachate testing) to meet food safety standards.
- What’s the main difference between compression molding and injection molding for silicone parts?
Compression molding is better for complex, high-precision parts (e.g., seals) but has longer cycle times. Injection molding is faster (ideal for mass production of mini parts like buttons) and has lower scrap rates, but requires higher initial mold investment.