1.What is silicone rubber?
Silicone rubber is an elastomer made from silicone – itself a polymer – which contains silicon as well as oxygen, hydrogen and carbon. Silicone rubber is successfully used in many industries due to its good chemical and physical properties. Silicone rubber is typically stable, non-reactive and can withstand extreme conditions and temperatures. It can withstand temperatures that would melt most plastics (+250°C) and maintains its flexibility at temperatures down to -70°C. Silicone rubber is also low-toxic and odorless.
Due to its excellent properties, silicone rubber offers the following advantages:
- Good electrical insulation
- Excellent sealing ability
- A very good service life
- Cheap and fast production
- Can be molded into different shapes
2.Why a silicone rubber mold?
Silicone can be stabilized in liquid form in any environment and the mold maintains its shape even under high loads and high temperatures. Silicone rubber also does not shrink after molding because no extracts or leaches come out of the silicone rubber after molding. It is also widely used in mold making due to its fine detail reproduction, physical strength, versatility, ease of use, and availability. Silicone rubber also allows for a variety of colors and hardnesses, making it the material of choice for an increasing number of molding applications.
3.How is silicone rubber molding made?
The molding of silicone rubber occurs through a series of steps explained below:
3.1 Creating the master pattern
CNC rapid prototyping is performed to produce the master sample
3.2 Form design
3.2.1 The structure
Before the mold is made, the sprue and ventilation must be considered. Ventilation openings and inlet holes allow casting material to flow into the rubber and silicone mold. The position and size of the gate openings are determined by the shape and volume of the master model. As a general rule: the larger the volume of the master model, the larger the sprue area.
3.2.2 Selection of silicone rubber
There are two types of silicone rubber used in the molding process today. 1) Condensation hardening (tin based) 2) Addition hardening (platinum based). Both types of silicone have slightly different characteristics and properties. When selecting the right silicone rubber for your mold, one of the most important considerations is the silicone rubber's resistance to inhibition. Inhibition is the result of any impurity present in the master being formed. Before the molding process, a patch test must be performed to detect or remove any existing contaminants.
3.3 Making the silicone rubber mold
After the master pattern has been created, a silicone rubber mold can be made. One of the most important properties of silicone rubber is the precision of its reproduction. Silicone rubber is widely known for its extreme attention to detail. Below are two main types of setup that can be used to create silicone rubber molds.
3.3.1 Book form/single-level form
Book mold or single stage mold is one of the most commonly used silicone rubber molding techniques. With this type of molding, the master part is hung in a molding box. Then liquid silicone rubber is placed in the box until it is full. Once the silicone hardens, the mold is cut in half. This is one of the most economical and economical ways to make a silicone mold.
3.3.2 Two-part tool/multi-stage tool
This method is a little more labor intensive, but allows better control over the mold parting line and allows the formation of larger parts due to better dimensional stability. The two-part shape is achieved by creating a dividing line with modeling clay. The silicone is then placed in a mold box until it is halfway formed. Once the first half of the casting is complete, the mold is inverted and the parting line compound is removed along with the silicone. Then the frame is replaced and the second half of the mold is cast and cured.
3.3.3 Mixing and ventilation
After selecting the type of mold and silicone rubber, it is necessary to ensure that the two components (catalyst and silicone base) are accurately weighed to achieve design accuracy. The mixture must also be made in a plastic container at least three to four times larger than the volume of the material. This allows air bubbles to escape freely during the ventilation process. Any bubbles in the silicone rubber can compromise the integrity of the final product.
4.Applications of silicone rubber
Due to its excellent physical and chemical properties, silicone rubber is a material of choice for various industries and applications. That includes
aerospace industry
Construction and renovation
Defense industry
Medical industry
Plug
Stamps
silicone rings
Coating of wires and cables
