Silicone mold injection molding is an advanced manufacturing technology that uses liquid silicone rubber (LSR) comme matière première, l'injecter dans des moules de haute précision sous température et pression contrôlées pour produire des produits en silicone de haute qualité. Contrairement à la fabrication manuelle traditionnelle de moules, il excelle dans la production de masse, haute précision dimensionnelle, and stable product performance—making it a core process in medical, électronique, et l'industrie automobile. But what are its core principles? How to control key processes? And how to address its unique challenges? This article answers these questions in detail.
1. Core Principles & Material Characteristics
To understand silicone mold injection molding, we first break down its working mechanism and the properties of its key raw material—liquid silicone.
UN. Core Working Principle
The process follows a simple but precise 因果链 (cause-and-effect chain):
- Raw Material Melting: Liquid silicone (two-component: main agent + curing agent) is fed into the injection machine’s barrel, where it is heated to a flowable state (no melting—silicone is thermoset, so this step softens it for injection).
- High-Pressure Injection: The injection machine pushes the softened silicone into a high-precision mold cavity (tolerance ±0.01mm) at a controlled speed (5–20mm/s) et la pression (10–50MPa).
- Guérison & Vulcanization: Le moule est chauffé (120–180°C) to trigger a chemical reaction in the silicone, turning it from liquid to elastic solid. Curing time depends on product thickness—e.g., 1mm-thick parts take 10–15 seconds; 10mm-thick parts take 60–90 seconds.
- Démoulage & Finition: Une fois guéri, le moule s'ouvre, and the product is ejected. Post-traitement (ébavurage, garniture) removes excess material, resulting in a finished part.
B. Matériel clé: Liquid Silicone Rubber (LSR)
LSR’s unique properties determine the process’s advantages. The table below highlights its critical characteristics:
| Material Characteristic | Specific Performance | Role in Injection Molding |
| Fluidity | Faible viscosité (5,000–20,000 cP) | Flows into micro-details of the mold (par ex., 0.1mm-thick sealing lips) |
| Résistance à la chaleur | Withstands -60°C to +250°C (short-term +300°C) | Suitable for high-temperature applications (par ex., automotive engine gaskets) |
| Chemical Stability | Résiste aux acides, alcalis, huiles, et solvants | Idéal pour les dispositifs médicaux (sterilized with alcohol) and electronic parts (resists coolants) |
| Élasticité | Elongation at break >500%; Shore hardness 20–80A | Ensures products (par ex., phone buttons, Joints toriques) maintain flexibility after repeated use |
| Biocompatibilité | Medical-grade LSR meets FDA 21 CFR §177.2600 | Safe for skin-contact products (par ex., baby pacifiers, medical catheters) |
2. Step-by-Step Production Process
Silicone mold injection molding follows a standardized, linear workflow—each step requires strict parameter control to avoid defects.
Étape 1: Raw Material Preparation & Essai
- Component Mixing: Blend LSR main agent and curing agent in a precise ratio (common 1:1 ou 10:1) using an automated mixer. For colored products, add 1–3% non-toxic pigments to the mixture.
- Contrôle qualité: Conduct 3 key tests:
- Viscosity Test: Ensure viscosity is 5,000–15,000 cP (too high = poor flow; too low = leakage).
- Curing Test: Cure a small sample at 160°C for 30 seconds—check for full solidification (no sticky surface).
- Impurity Check: Filter the mixture through a 5μm sieve to remove particles (prevents mold clogging).
Étape 2: Conception de moules & Fabrication
Molds are the “heart” of the process—their precision directly impacts product quality.
- Design Considerations:
- Gate Location: Place gates (injection inlets) at thick sections to avoid air traps. Pour les petites pièces (par ex., connecteurs électroniques), use pinpoint gates (0.5–1mm diameter).
- Circuit de refroidissement: Add water channels around the cavity to control mold temperature (±2°C tolerance)—prevents uneven curing.
- Traitement de surface: Apply chrome plating (5–10μm thickness) or nitriding to the mold surface. This improves wear resistance (extends mold life to 100,000+ cycles) and release performance (reduces sticking).
- Manufacturing Equipment: Use CNC machining centers (accuracy ±0.005mm) to mill the mold cavity. For complex shapes (par ex., composants de dispositifs médicaux), add EDM (Usinage par électroérosion) for micro-details.
Étape 3: Injection Molding Parameter Setup
Key parameters must be optimized—incorrect settings cause defects like bubbles or shrinkage. The table below lists critical parameters and their ideal ranges:
| Paramètre | Ideal Range | Impact of Incorrect Settings |
| Température du baril | 40–60°C (zone 1: 40°C; zone 2: 50°C; zone 3: 60°C) | Too high (>70°C) = premature curing (blocks the barrel); trop bas (<30°C) = poor flow |
| Pression d'injection | 15–30MPa | Too high (>40MPa) = mold deformation; trop bas (<10MPa) = incomplete cavity filling |
| Vitesse d'injection | 8–15mm/s (staged: slow start → fast middle → slow end) | Too fast (>20mm/s) = air trapping (bulles); trop lent (<5mm/s) = cold slugs (uneven texture) |
| Température du moule | 140–160°C | Too high (>180°C) = over-curing (brittle parts); trop bas (<120°C) = under-curing (sticky surface) |
| Temps de durcissement | 10–120 secondes (1 second per mm of thickness) | Too short = under-curing; too long = reduced production efficiency |
Étape 4: Guérison, Démoulage & Post-traitement
- Guérison: The mold remains closed for the set time—use a mold temperature controller to maintain stable heat.
- Démoulage: Use robotic ejectors (pour la production de masse) ou outils manuels (pour les petits lots) to remove parts. Apply a thin layer of silicone release agent if sticking occurs (avoid excess—causes surface defects).
- Post-traitement:
- Ébavurage: Trim gate residues with a laser cutter (for precision parts) or sharp scissors (pour les pièces non critiques).
- Cleaning: Wash parts with deionized water to remove release agent residue.
- Secondary Vulcanization (Facultatif): For high-temperature parts (par ex., joints automobiles), bake at 200°C for 2–4 hours to improve heat resistance.
3. Avantages & Défis: A Comparative Analysis
Silicone mold injection molding has clear strengths compared to traditional manufacturing methods (par ex., moulage par compression, manual casting). It also faces unique challenges—understanding both helps users decide if it’s the right process.
UN. Advantages Over Traditional Methods
| Avantage | Silicone Mold Injection Molding | Moulage par compression | Manual Casting |
| Production Efficiency | Haut (30–60 parts per minute for small components) | Moyen (5–10 parts per minute) | Faible (1–2 parts per hour) |
| Précision dimensionnelle | ±0,01mm (ideal for precision parts) | ±0,1mm (limited by mold pressure) | ±0,5 mm (human error) |
| Product Consistency | 99.5% uniformity (processus automatisé) | 90% uniformity (dépend de la compétence de l'opérateur) | 70% uniformity (high variability) |
| Gestion de la complexité | Excellent (can produce parts with undercuts, micro-trous) | Pauvre (requires split molds for complexity) | Very poor (limited to simple shapes) |
| Déchets de matériaux | Faible (<5% scrap—excess can be recycled) | Moyen (10–15% scrap) | Haut (20–30% scrap) |
B. Key Challenges & Mitigation Strategies
| Défi | Root Cause | Mitigation Strategy |
| High Initial Investment | Mold manufacturing (Usinage CNC + traitement de surface) frais \(10,000–)100,000; injection machines cost \(50,000–)200,000 | – Pour les petits lots: Use shared molds (reduces cost by 50%).- For long-term projects: Choose high-wear-resistant mold materials (par ex., Acier H13) to extend life (100,000+ cycles) |
| Mold Clogging | Impurities in LSR or low fluidity | – Filter LSR through 5μm sieves before injection.- Preheat LSR to 50°C (improves fluidity) |
| Bubble Formation | Air trapped during injection or incomplete venting | – Add vent grooves (0.01–0.02mm depth) to the mold.- Use vacuum-assisted injection (removes air from the cavity) |
| Shrinkage Defects | Uneven cooling or over-curing | – Optimize mold cooling channels (ensure uniform temperature).- Add 1–2% shrinkage allowance to the mold design |
4. Application Fields: Where It Shines
Silicone mold injection molding is widely used in industries that demand precision, durabilité, et biocompatibilité. The table below highlights key applications with specific examples:
| Industrie | Typical Products | LSR Grade | Key Process Requirements |
| Dispositifs médicaux | Conseils sur les cathéters, surgical instrument gaskets, baby pacifiers | Qualité médicale (FDA 21 CFR §177.2600) | – Cleanroom production (Classe 100,000).- No release agent (avoids contamination).- Biocompatibility testing post-production |
| Électronique | Phone buttons, LED lamp seals, sensor O-rings | Qualité industrielle (high insulation) | – Haute précision (±0.005mm for button travel).- Low volatility (no VOCs to damage electronics) |
| Automobile | Engine gaskets, fuel system seals, composants du tableau de bord | High-temperature grade (resists 250°C) | – Résistance chimique (aux huiles, coolants).- Vibration resistance (élongation >500%) |
| Biens de consommation | Silicone kitchen utensils (spatulas), waterproof watch bands | Food-grade (Approuvé par la FDA) | – Non-toxic pigments.- Surface lisse (Râ <0.8µm) pour un nettoyage facile |
5. Yigu Technology’s Perspective on Silicone Mold Injection Molding
Chez Yigu Technologie, we see silicone mold injection molding as a cornerstone of high-precision manufacturing—especially for industries like medical and automotive. Pour les clients médicaux, our custom injection molds (tolérance ±0,008 mm) and medical-grade LSR have enabled the production of 100,000+ catheter tips with 0% biocompatibility failures. For automotive partners, our high-temperature LSR (resists 280°C) and optimized cooling systems reduce engine gasket shrinkage to <0.5%, improving product lifespan by 30%.
We’re addressing key challenges by: 1) Developing low-cost mold materials (par ex., coated aluminum) that cut mold costs by 40% tout en maintenant 50,000+ cycles; 2) Integrating AI into parameter control (automatically adjusts temperature/pressure to reduce defects by 25%). Our goal is to make this technology accessible to mid-sized businesses—balancing precision with affordability.
FAQ
- Quelle est la quantité minimum de commande (MOQ) for silicone mold injection molding?
MOQ depends on mold cost: Pour les pièces standards (par ex., Joints toriques), MOQ is 10,000–50,000 units (to offset mold costs). Pour les pièces personnalisées, we offer shared molds with MOQ as low as 1,000 unités (ideal for small-batch testing).
- Can silicone mold injection molding produce transparent silicone products?
Yes—use high-purity LSR (impurity content <0.1%) and polished molds (Râ <0.02µm). We’ve produced transparent medical connectors with 90% transmission de la lumière, meeting optical requirements for device visualization.
- How long does it take to develop a custom silicone mold and start production?
Mold development takes 4–6 weeks (Usinage CNC + essai). After mold approval, production can start within 1 semaine. Pour les projets urgents (par ex., medical device emergencies), we offer expedited mold development (2–3 semaines) with priority production.