Silicone is a versatile material used in a wide range of products, from medical devices to consumer goods. One of the most common manufacturing methods for silicone parts is injection molding. But can silicone actually be injection molded? As a plastic injection molding manufacturer, I will help you find it out!
Can Silicone Be Injection Molded?
Yes, silicone can absolutely be injection molded. In fact, injection molding is one of the most popular processing methods for silicone parts and products.
The type of silicone typically used for injection molding is liquid silicone rubber (LSR). LSR has an ideal viscosity that allows it to be injected into molds under high pressure.
Here’s a quick overview of how silicone injection molding works:
- Liquid silicone rubber (LSR) is loaded into the barrel of an injection molding machine.
- The LSR is heated until it reaches a molten state.
- The liquid silicone is injected under high pressure into a steel mold.
- It quickly cools and cures into the shape of the mold cavity.
- The molded silicone part is then ejected from the mold.
This enables intricate silicone parts to be mass produced efficiently and precisely.
Benefits of Silicone Injection Molding
There are several major benefits that make silicone injection molding popular for manufacturing:
Quick Cure Times
The platinum-catalyzed cure system used for LSR results in very fast cure times. Parts can be demolded in less than a minute, allowing for high-volume production.
Precision Molding
The high pressures used allow silicone to be injected into tiny cavities, holes, and channels. This permits complex and detailed part geometries.
Flexible Materials
Silicone injection molding can produce durable components in a shore hardness range from 5A to 80A. This includes super soft and flexible silicones.
Temperature Resistance
Molded silicone rubber maintains its properties at very high and very low temperatures, typically from -100 to 300°C.
These and other advantages make silicone an ideal material for injection molding applications across many industries.
What Products Use Silicone Injection Molding?
Silicone injection molding is used to produce components and products in a diverse range of markets, including:
- Medical: Pump diaphragms, seals, valves, stoppers, connectors, masks, tubing
- Automotive: Gaskets, seals, valves, mats, masks, tubes, connectors
- Electronics: Keyboards, connectors, insulators, grommets, seals
- Appliances: Gaskets, mats, tubing, seals, handles, cases
- Consumer goods: Kitchenware, baby products, wearables, masks, handles
Virtually any application that calls for flexible, heat-resistant molded rubber parts can benefit from silicone injection molding technology.
Silicone Molding Process Explained
While the fundamentals are straightforward, successfully injection molding silicone parts requires attention to detail.
Here is a more in-depth look at the complete silicone injection molding process:
1. Design the Part and Tooling
As with any injection molded component, the manufacturing process starts with CAD software to design the silicone part and corresponding mold tooling. Things like draft angles, tolerance requirements, material injection points, and ejector pin locations require consideration.
The injection molding tool must withstand pressures exceeding 15,000 psi and temperatures above 350°F needed to mold silicone.
2. Choose a Silicone Material
LSR is supplied by companies like Dow Corning in two liquid component formats that must be precisely mixed before injection. The choice of material grade will determine properties like hardness, elongation, tear strength, and heat resistance. Electrical, medical, pharmaceutical, food, and fuel grade options are all available.
3. Prepare the Injection Machine
Special two-component injection molding machines are used that can handle aggressive silicone mixing. The precise 1:1 mixing of the two material components is critical to achieve consistent material properties and avoid cosmetic issues with the final molded parts.
4. Heat the Tooling
The mold must be heated to a temperature high enough to vulcanize the liquid silicone rubber material and produce completed silicone parts. This is typically between 280-400°F depending on durometer, filler content, and other variables. Insufficient heat will lead to incompletely cured parts.
5. Inject the Silicone
Once the mold is up to temperature, the mixed and dosed LSR is injected into the tooling at high pressure, anywhere from 2,000-15,000 PSI depending on part size and geometry. The liquid silicone quickly fills the entirety of the mold cavity.
6. Cure the Molded Parts
As heat transfers from the mold walls to the liquid silicone, it rapidly cures into solid rubber that adopts the precise shape of the tooling. The standard cure time is usually between 30 to 120 seconds. Additional post-cure time is sometimes required for low-durometer silicones.
7. Eject and Finish Parts
Once cured, the silicone parts are ejected from the mold by the ejector pins. Secondary processes like deflashing to remove excess silicone flash may be required before the component is complete. The finished parts can then be packaged and shipped to customers.
While the basic process is straightforward, factors like fill rate, injection pressure, tool heating, and cycle optimization must be dialed in to produce perfect silicone parts consistently with maximum efficiency.
Is Silicone Injection Molding Right For My Product?
Silicone injection molding offers an efficient, precision production method capable of molding intricate and detailed silicone rubber components. It provides robust solutions for products across medical, consumer, industrial, and electronics markets.
However, the specialized equipment required does necessitate high initial overhead costs. Silicone injection molding is best suited for high-volume production scenarios to maximize ROI on tooling expenses.
For lower volume applications, silicone compression molding can provide a more practical solution, albeit with longer cycle times. The cost per part crossover point between the two methods can help determine which is the better option.
OEMs interested in leveraging silicone molding would benefit from an expert manufacturing partner to help launch production. A full-service provider experienced with silicone can guide decisions around tooling, processing, secondary steps, and other critical considerations that impact cost and lead times.
In Summary
Yes, silicone absolutely can be injection molded thanks to innovative technologies like LSR. When combined with the proper planning and process execution, silicone injection molding offers exceptional efficiency, quality, and design freedom. The unique properties of silicone rubber make it an ideal candidate for this versatile high-volume manufacturing technique.
