Silicone molds is a block of rubber with an internal empty cavity. In most cases, a liquid casting material can be poured or forced into the container and then hardened, making a solid object in the shape of the mold cavity. Usually there are one-piece silicone molds and two-piece silicone molds. One-piece silicone molds are used for creating items with flat bottom surfaces and positively angled geometry without undercuts: soap molds, candle molds, and chocolate molds, for example. Two-part silicone molds are commonly used for more complex geometry like mechanical parts, statues, and sculptures.
Production principle
The silicone rubber mold process is a soft tooling by indirect mold manufacturing method. The process requires a physical 3D Printed part, called the "master." The master part is a 3D Printed part made in high-resolution SLA Resin, and is perfectly smooth so as to allow for a high-quality mold and smooth cast parts.
To produce your silicone mold, we will first 3D Print your master part in SLA Resin, and then create a silicone mold from that part.
Silicone Mold Making Materials
Most silicone molds are made of a raw material called RTV silicone (for room temperature vulcan ization), while some are made of called HTV silicone rubber (for high temperature vulcanization). There are many, many types and formulations of RTV silicone rubber mold material, but for craft and hobby uses they are available in two general forms, a liquid silicone (tin-cured and platinum-cured silicone) and a solid silicone (silicone putty).
Casting Material
Creating parts from a silicone mold is commonly called Vacuum Casting, RTV Molding or RTV Casting. The material poured into the silicone mold -- the material in which your copied parts are made -- is called casting material. Popular casting materials that work with silicone molds are urethane resin plastic, epoxy resin, plaster, polyurethane foam, wax, soap, and concrete.
Type of Silicone Molds
Single-part Silicone Molds
If your part is widest at its base and has positively angled geometry without undercuts, then a dump mold is your best option for casting out copies in standard casting materials: resin, wax, soap, concrete, plaster, foam, etc.
Multi-cavity Tray Molds
A tray mold is a dump mold with multiple identical cavities. Tray molds allow you to cast out copies more quickly and efficiently, compared to single-cavity dump molds.
Two-part Silicone Molds
Figurines, statues, prototypes and end-use parts with complex geometry can be produced using a 2-part silicone block mold.
Advantages of silicone molds
Flexibility: silicone rubber is a very versatile, easy-to-use material, you can easily create custom designs using silicone molding. Silicone not only acts as a natural release agent, but is itself extremely flexible. so you can use them repeatedly without fear of breakage. The cured resin can be removed from a silicone mold very easily.
Reproduce the Details: Silicone molds replicate without the loss of the intricacies of the original, as silicone rubbers will capture the minutest of detail, even down to the fingerprints.
Durability: Silicone rubber molds have a fairly long library life. You can continue to use the same mold or molds for reproductions again and again, which often offsets the higher cost of silicone rubber.
Stability: Silicone molds can be used in hot or cold temperatures (-50℃ to 250℃) without degrading or warping, making them suitable for applications like cooking.
With the good flexibility and elasticity, silicone rubber mold is able to make parts with complex structure, fine pattern, no mold draft angle, even a negative angle and deep grooves.
How to make
Silicone putty
Silicone putty material comes in two parts, each part about the thickness of standard putty. To use, cut equal parts of Part A and Part B and then combine them, mixing them in your palm. Each part is a different color so once the colors are fully blended without any marbling the silicone has been properly combined. Simply place the thick putty around the original piece. It's set in five minutes. It is thick thst enough when cured, it usually does not need a mother mold or a mold box, another benefit of silicone putty.
RTV-2 liquid silicone rubber
Step 1: Prototype placement
After cleaning and simple processing of the prototype, place it on the plate and fix it, make the mold frame and fix the mold frame it, make the distance between the prototype and the mold frame even, and brush some demolding reagent on the inner surface of the mold frame plate.
Step 2: Stick a Clay and Pouring gypsum backing
stick clay or plasticine on the prototype surface, and then pour the prepared plaster slurry into the mold frame. After the plaster slurry solidifies, remove the clay or plasticine layer, and clean the clay or plasticine adhered to the prototype to avoid affecting the surface quality of the mold.
Step 3: Pouring liquid silicone
The volume of silicone rubber to be prepared can be calculated with the volume of the removed clay layer and a certain loss. After full mixed, evacuate the bubble in the silicone rubber mixture in the vacuum extractor. Then pour the silicone rubber .
Step 4: Curing
Solidify the cast silicone rubber mold at room temperature or by heating. After the silicone rubber does not stick to the hand, remove the prototype and continue to solidify the silicone rubber at room temperature or by heating.
Step 5: Repair new mold
After the prototype is removed, if some small defects are found in the mold, it can be repaired with newly prepared silicone rubber and solidify.
Silicone Mold Hardness
Silicone molds are soft or hard. The Shore hardness usually ranges from 0 to 60, but no matter how soft or hard it is, it has elasticity. These are specified in Shore, whereby a low value stands for high elasticity and a high value for low elasticity:
- 0-15 Shore A: Very soft, but slightly weaker in tear strength.
- 20-40 Shore A: denotes a medium elasticity. The extensive flexibility of this material is complemented by a relatively good dimensional stability.
- 40-60 Shore A: denotes a high hardness silicone. It is more resistant to stress, but is also quite brittle.
Which degree of hardness is best for you depends on your project and is also to some extent a matter of trial and error. The softer the material, the easier it is to release the workpiece from the silicone mold. However, due to the high elasticity and low brittleness the mold is very unstable. The opposite is the case with a solid mold: workpieces are not so easy to release and you have to be careful that the brittle silicone does not break. However, casting molds with a high Shore value are of course easier to handle because they are less mobile and do not deform as easily.
Applications for Silicone Molds
In casting, baking, and other activities requiring a mold, silicone molds are always preferred. This stems from the basic fact that these molds are very easy to use. Silicone molds have many different purposes. Some of the most common ones include household applications, kids’ toys, baking or cooking tools, candle molds, and medical uses. Here are a few examples of industries and applications that make silicone molds to produce their products:
Prototyping & Inventing
High-accuracy & high-performance mold making and casting materials for the ultimate in accuracy everytime. Therefore, silicone mold is great alternative in the stage of prototype to achieve rapid, accurate and low-cost sample acquisition.
Jewelry Designing
Jewelers use custom silicone molds to duplicate hand-carved or 3D printed patterns in wax, allowing them to phase out the time-consuming labor of creating wax-carved patterns for each new piece, but still continue to cast from wax. This offers a major leap in serial production, making it possible for investment casting to work at scale. Because silicone molds capture a fine level of detail, jewelers can produce pieces with ornate details and intricate geometries.
Consumer Goods
Creators use silicone molds to make many custom crafts such as soaps and candles. Even manufacturers of school supplies often use silicone molds to form items such as chalk and erasers.
Food Related
Make your own custom or personalized chocolate molds, or even make molds for fondant or cakes. Since silicone can handle heat up to 250° degrees Celsius, molds can be used in cooking, too. Small baked goods such as muffins and cupcakes rise nicely in silicone molds.
DIY Projects
Art lovers often use silicone molding to craft unique creations. You can use silicone molds to form or replicate everything from bath bombs to dog treats—the possibilities are nearly endless. A fun silicone molding project for kids is to create a lifecast of their hand. Just make sure you choose a skin-safe silicone.
Safety & Cleaning
Silicone molds are environmentally friendly and safe. It is non-toxic and therefore comparatively gentle on the environment. This is one of the reasons why silicone is often used to make things like bakeware or pacifiers for small children. However, not all liquid silicone rubber molding is suitable for use with food. If you’re making molds that you plan on using for food (like chocolate molds or even ice trays) you’ll want to choose food grade silicone rubber (platinum-cured silicone rubber). Because this silicone is approved by the FDA.
To wash the silicone molds it is recommended not to use strong detergents, sparkling aids and deodorants for dishwashers. In case of washing with rinse aid, it may occur the appearance of a white coating on the surface of the mould and in the subsequent baking foods could present a flavor alteration. However, the performance and safety of the mould are not compromised. To eliminate this problem we recommend boiling the product in water for a few minutes.
