Fabrication of Silicone Molds

What are Silicone Molds?

Silicone rubber, used throughout industries and homes, is a part of our daily life. It is a stretchy material that is used to make muffin pans, pot holders, food molds, medical devices, jewelry components, and much more. Silicone molds are made from RTV (Room Temperature Vulcanizing) silicone by a combination of parts that results in a chemical reaction, causing the rubber to vulcanize into a non-stick, stretchy, and durable material. Silicone rubber is of many types to be made into different molds for different purposes.

Use EDM machines for precise molding

Properties of Silicone Molds

  • Silicone molds are heat resistant and can be used at 302 °F (150 °C) degrees without any change in performance.
  • They are also cold-resistant and can retain elasticity even at -76 °F (-60 °C) to -94 °F (-70 °C).
  •  Silicone rubber is flammable, but if a flame retardant is added, it becomes flame retardant and self-extinguishing.
  • Silicone rubber is highly resistant to any electric discharge and remains stable even at high temperatures and frequencies.
  • Other unique properties include being hydrophobic and having the ability to easily release materials from its surface.

Fabrication of Silicone Molds

There are many different fabrication methods for silicone molds, and choosing the right one is very important. Some of these methods are as follows:

➢  Extrusion of Raw Material-

  • Extrusion is done by creating uncured raw material with the help of dye to form a uniform cross-sectional shaped product.
  • The raw material is passed through the extruder, which uses screws for temperature fluctuation and rotation.
  • After shaping the product into the required shape, it is washed and cooled by air or water and then cut into the final product.
  • The extrusion process is low-cost, takes less time, and produces a bulk of products.
  • It is difficult to maintain tolerance criteria, and per-part price varies due to the complexity of the dye.
  • It is best for the production of gaskets, tubing, and seals.
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➢  Injection Molding –

  • It is the most common, robust, and complex process because the products vary in size and application.
  • Material is injected into mold halves with a plunger.
  • This method is best because it has great output production, can be automated, and has short molding cycles.
  • Many types of materials can be used at the same time, and no trimming of product is needed.
  • Trapped air bubbles, flash, and sinks are problems that can be solved by venting.
  • It is best for thin-walled products; therefore, it is used to make small parts and automobile body panels.
Liquid Silicone Molding

➢  Liquid Injection Molding

  • Liquid injection molding creates products in cavities, and the liquid material is injected into these cavities.
  • In this process, raw materials are mixed mechanically. After the product is hardened, it is ejected from the mold cavity.
  • It is a high-pressure process, has a shorter cure time, and is used to make intricate designs with great precision.
  • This method is used to mass-produce products, with thermal imaging technology employed to identify any errors.
  • It is best to make gaskets, o-rings, keypads and electronic contacts.
Liquid Silicone Adding

➢  Compression Molding –

  • Preform rubber is placed into heated cavities to create molds.
  • The raw material can be in the form of pre-measured pellets, granules, or powder.
  • The cavities are closed by heated plungers and put under pressure of 15,000psi to 20,000psi.
  • It is an economical method that has a low-to-medium production rate.
  • The cavities should be cleaned properly to avoid any contamination.
  • Seals, o-rings, gaskets, automotive parts, and cushioning pads are products made from this process.
One-shot Molding

➢  Product Calendering –

  • It is a speedy, continuous sheeting process that uses a number of rollers to press the semi-liquid material into a hard sheet.
  • The products are then coated onto fabrics.
  • It is essential to set an optimum temperature for rollers to avoid overheating and sticking.
  • Creeping of the product is also a concern in calendering.
  • It is used to make dye sheet cuts and thin sheets of material.

➢  Transfer Molding –

  • A plunger puts the material in the heated cavity, and then it is cooled down to take the shape of the mold.
  • The waste created by compression of the mold is then manually trimmed,  followed by cryogenic processes, tumbling, or precision grinding.
  • It has a shorter production cycle and a tighter dimensional tolerance.
  • This process is used to make smaller, more complex, and more detailed parts.

Silicon molds are created to make thousands of things that we use in our daily life, from toys, gifts, candles, and more. Wetop makes silicone kitchen appliances, electronics accessories, and baby products that can also be customized according to your requirements. Do check us out today!

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