When it comes to manufacturing durable, flexible, and heat-resistant parts, silicone is often the material of choice. Its versatility makes it ideal for a range of industries, from automotive and medical devices to consumer electronics and kitchenware. But how exactly do you transform raw silicone into precisely shaped, functional products?
What is Silicone Molding?
Silicone molding is a manufacturing process where liquid silicone rubber (LSR) is shaped into various forms. The most common methods include compression molding, transfer molding, and injection molding. Among these, injection molding is the most popular for producing high-quality, intricate parts in large quantities.
Please watch the following YouTube video to learn how silicon molding parts are removed from a high-temperature molding machine.
Why Choose Silicone?
Before diving into the process, it’s worth understanding why silicone is such a popular material. Silicone rubber stands out for its flexibility, durability, and resistance to extreme temperatures, chemicals, and UV light. It’s non-toxic and hypoallergenic, making it suitable for medical applications. Plus, silicone can be easily colored or made transparent, offering a range of design possibilities.
Types of Silicone Molding
The two main types of moldable silicone raw materials are High Consistency Rubber (HCR) and Liquid Silicone Rubber (LSR).
High Consistency Rubber (HCR)
High Consistency Rubber (HCR) is a thick silicone material used in compression and transfer molding. Compression molding involves placing HCR between heated plates, ideal for low-volume production. Transfer molding transfers HCR through a system into the mold, suited for parts needing specific properties or mid-range volumes.
Liquid Silicone Rubber (LSR)
Liquid Silicone Rubber (LSR) is a fluid silicone used in Liquid Injection Molding (LIM). It supports several technologies: Overmolding, which covers a substrate with silicone; Two-shot molding, combining thermoplastic and silicone simultaneously; and Micromolding, producing very small parts for advanced medical devices.
Here’s a look at the different types of silicone rubber and their specific uses.
| Type of Silicone | Description | Properties | Applications |
|---|---|---|---|
| Transparent Silicone Rubber | Clear silicone with Shore hardness of A 10 to A 70. | Used as an invisible gasket, does not interfere with aesthetics. | Airflow diaphragms, cosmetic products |
| Fluorosilicone Rubber | Contains fluorine in its polymer chain, combining properties of silicones and fluorocarbons. | Resistant to fuels, oils, solvents, and extreme temperatures. | Aerospace, automotive applications |
| Low Hardness Silicone Rubber | Softest silicone with a Shore hardness between A 5 and A 20. | Stretchy, can be pulled and reformed multiple times without tearing. | Baby bottle nipples, food storage film, anti-slip mats |
| Flame Retardant Silicone Rubber | Silicone with high thermal conductivity and heat resistance. | Self-extinguishing, enhanced flame resistance through special additives. | Fire or heat contact applications |
| High Strength Silicone Rubber | Designed for extreme elongation, tearing, and high resistance to abrasion and fatigue. | Tear strength of 29 to 49 kN/m. | Molding, extrusion, calendaring |
| Electrically Conductive Silicone Rubber | Silicone rubber compounded with carbon and other conductive materials. | Reduces electromagnetic and radio frequency interference. | Electronics, EMI/RFI shielding |
| Heat Resistant Silicone Rubber | Maintains stability and properties even at high temperatures (up to 150°C/302°F). | Excellent thermal stability, resistant to high temperatures. | High-temperature applications |
| General Purpose Silicone Rubber | Common silicone rubber with a Shore hardness of A 30 to A 70. | Versatile, used for compression molding and extrusion. | Kitchen utensils, tubing, vehicle parts |
| Thermal Conductive Silicone Rubber | Moves heat away from sensitive areas, ideal for electronics. | Effective in dissipating heat, used with CPUs and electronic enclosures. | Electronic devices, heat dissipation |
| High Hardness Silicone Rubber | Silicone with a Shore hardness up to A 90. | High elongation, tear strength, abrasion, and fatigue resistance. | Molding, extrusion, calendaring |
| Oil Resistant Silicone Rubber | Resistant to oils without affecting its structure. | Maintains properties after exposure to oils. | Oil-related applications |
| Methyl Group | Dimethyl silicone elastomer, the first developed silicone elastomer. | General-purpose elastomer. | Various general applications |
| Methyl and Phenyl Groups | Methyl-phenyl silicone elastomers, developed for low temperature applications. | Better performance at low temperatures. | Low-temperature applications |
| Methyl and Vinyl Groups | Methyl-vinyl silicone elastomers, helps in the vulcanization process. | Enhanced vulcanization properties. | Various applications requiring enhanced vulcanization |
| Methyl, Phenyl, and Vinyl Groups | Silicone elastomers with methyl, phenyl, and vinyl groups, suitable for low temperatures. | Good performance in low-temperature applications. | Low-temperature applications |
| Fluorine, Vinyl, and Methyl Groups | Fluorosilicone rubber known for its resistance to oil, fuels, and solvents. | Exceptional resistance to chemicals and extreme temperatures. | Aerospace, automotive, chemical industries |
How Are Silicone Rubber Parts Made?
Silicone rubber parts are produced through several methods, each suited to different needs.
| Method | Description | Advantages |
|---|---|---|
| Injection Molding | Heated silicone is injected into a die under pressure, filling the cavity to form complex shapes. | Suitable for complex designs and high volume. |
| Liquid Injection Molding | Liquid silicone is mixed and injected into a mold cavity using two plungers, with additives and catalysts. | Shorter curing times, precise designs. |
| Extrusion | Raw silicone is heated and compressed through a die to form shapes like tubing and seals. | Low cost, high volume production. |
| Compression Molding | Silicone is placed into heated molds and compressed to form the part. | Cost-effective for low volumes. |
| Transfer Molding | Silicone is placed in a pot and forced into a mold cavity under high pressure through a sprue. | Precise parts with minimal waste. |
| Calendaring | Silicone is fed between rollers to produce thin sheets. | Produces thin, even sheets. |
How is Silicone Rubber Made?
Silicone rubber, a polymer known for its flexibility and heat resistance, is created by isolating silicon from silica. This is done by heating quartz sand to 1800°C (3272°F) and reacting the resulting pure silicon with methyl chloride to form dimethyldichlorosilane (DMDCS).
DMDCS is then hydrolyzed to produce polydimethylsiloxane (PDMS) chains, which are cross-linked to form a three-dimensional network. Additives such as fillers, pigments, and stabilizers are mixed in to enhance properties like tear resistance and color. The final product is shaped and cured through vulcanization, either at high temperatures for strength or at room temperature for softness.
How Are Silicone Molds Made?
Silicone molds are created by either a one-part or two-part process. In a one-part mold, a master part is made, coated with release agent, and then covered with mixed silicone rubber. After curing, the master is removed, and the mold is ready for use. For a two-part mold, the master is embedded in clay, and silicone is poured over it to form one half of the mold. After curing, the mold is separated and a second silicone layer is added to complete the mold. This process results in durable molds suitable for producing high-quality parts.
Advantages of Silicone Molding
Silicone molding offers a range of benefits that make it a preferred choice for many applications.
- Captures intricate details accurately.
- Long-lasting and can be used multiple times.
- Withstands high temperatures without deforming.
- Resistant to many chemicals and solvents.
- Quick setting speeds up production.
- Requires minimal upkeep compared to other molds.
- Suitable for a wide range of applications and products.
- Ideal for complex and detailed designs.
- Parts come out of the mold without damage.
- Economical for both small and high volume production runs.
- Maintains shape and size over time.
- Minimal size changes during curing.
- Non-stick surface ensures easy part removal.
- Can create both simple and intricate shapes.
- Efficient use of materials with minimal excess.
Why is Silicone a Great Molding Material?
Silicone is a top choice for molding because it’s versatile, precise, and durable. It handles extreme temperatures and chemicals, cures quickly, and requires minimal maintenance. Silicone molds are easy to release, have low shrinkage, and are cost-effective for various designs.
How To Clean Silicone Air Fired Molds?
To clean silicone air-fired molds, start by allowing them to cool completely. Gently scrape off any residue with a soft, non-abrasive tool. Wash the mold with warm, soapy water using a soft brush or cloth, avoiding harsh chemicals or abrasive cleaners. Rinse thoroughly with clean water and dry completely with a lint-free cloth or let it air dry.
How to Paint Silicone Molds?
Clean the mold and apply a silicone-compatible primer. Use silicone or acrylic paint, applying thin, even coats. Let each coat dry before adding more, and finish with a clear silicone sealer for durability.
How To Color Silicone Molds?
To color silicone molds, you can mix silicone pigments directly into the silicone before it cures. Simply add a few drops of pigment to the uncured silicone and mix thoroughly until the color is evenly distributed. This allows the color to bond with the silicone, resulting in a vibrant and permanent hue.
How To Make Molds At Home Without Silicone?
You can make molds at home without silicone by using materials like gelatin, cornstarch, or plaster. Gelatin molds are made by dissolving gelatin in hot water and pouring it over your object, then letting it set. Cornstarch and glue can be mixed to form a moldable dough that hardens as it dries. Plaster of Paris is another alternative; simply mix it with water and pour it over the object you want to mold, allowing it to harden.
How To Remove Jello From Silicone Mold?
First, ensure the Jello is fully set by chilling it in the refrigerator. Once ready, gently pull the edges of the silicone mold away from the Jello to loosen it. You can also dip the bottom of the mold briefly in warm water to help release the Jello. Finally, place a plate over the mold, flip it upside down, and gently tap or squeeze the mold to release the Jello onto the plate.
Where To Buy Silicone Molds?
You can buy silicone molds from a variety of online retailers, specialty kitchen stores, and craft shops. For customized or specialized silicone molds, consider BOYI, which offers high-quality silicone mold manufacturing services tailored to your specific needs.
Get Started with BOYI’s Silicone Molding Services
BOYI provides silicone molding services, specializing in creating high-quality, precise silicone parts for a range of applications. Whether you need intricate designs or durable molds, BOYI expertise ensures excellent results tailored to your requirements.
Ready to bring your project to life with top-quality silicone molds? Contact BOYI today to discuss your silicone molding needs and discover how our expert team can provide precise, durable, and cost-effective solutions. Don’t wait—reach out now to get started on creating the perfect parts for your applications!
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FAQ
If you need high precision, flexibility, and durability, silicone molds are often the better choice. For high-volume production with a focus on cost efficiency, plastic molds might be more suitable.
Silicone molding can be relatively expensive compared to other molding processes, particularly for high-volume production. The costs associated with silicone molding include the price of the silicone material, the complexity of the mold design, and the setup for the molding process.
Silicone molds are flexible and versatile but can be expensive, less durable for high-volume use, and sensitive to extreme temperatures and chemicals. They may also have longer curing times and less detail compared to metal molds.
To seal a silicone mold, clean the mold, apply a mold release agent, fit the parts together, and seal the edges with silicone sealant or tape. Apply even pressure and let the silicone cure as instructed.
A silicone mold can last anywhere from several months to several years, depending on factors like usage frequency, proper maintenance, and the type of silicone used.
Two-part silicone is more expensive due to its complex formulation and curing process. It requires precise mixing of base and catalyst, which involves higher-quality materials and careful handling.
Yes, it’s generally a good idea to spray silicone molds with a mold release agent before use. This helps ensure that the cast material releases easily from the mold and extends the life of the silicone mold by reducing wear and tear.
Yes, silicone molds are safe for baking. They can withstand high temperatures, typically up to 450°F (232°C), making them ideal for use in ovens.
Catalog: Injection Molding Guide
This article was written by engineers from the BOYI team. Fuquan Chen is a professional engineer and technical expert with 20 years of experience in rapid prototyping, mold manufacturing, and plastic injection molding.
