Most of us have gotten used to buying different plastic molds. However, this can be quite expensive, especially if you want to buy different molds for different shapes. It is likely to be more to your benefit to learn how to make plastic molds at home. Here are steps you can follow:
Choose the material for the plastic mold that you want to make. You can choose from among the following:
Urethane RTV rubber – a material used for making rubber molds, stamp pads, and concrete form liners. It also makes good plastic molds since it exhibits resistance to tearing, abrasion, and stretching. Aside from that, its low viscosity makes it easy to mold and process.
Silicone RTV rubber – The finished molds are tear-resistant and flexible. Moreover, they can make fine details stand out, and can also withstand high temperatures.
Polyurethane casting resin – This is safer than polyester and is also fast curing, taking only about 5 to 10 minutes to make a durable finish. This is best for casting highly detailed molds and shapes, as well as small-scale replicas.
Resin filler powder – This serves as a thickening agent and improves the liquid resin viscosity before casting. It helps make your plastic molds stronger, smoother, and less prone to plastic shrinkage.
Mold release – It helps release mold rubbers and enhances the efficiency of casting. Moreover, it lengthens the lifespan of your finished product.
Sulpho-plastics – These are best for light casting and plastic mold making as they provide strength and malleability. Aside from plastic molds, sulpho-plastics are best used for manufacturing novelty items and ornaments.
Let’s take sulpho-plastics as an example: Mix the sulpho-plastic completely until it is smooth.
Heat and melt the mixture using a bowl. Do not use direct heat or open flames on it, as sulpho-plastics are highly flammable.
If the mixture has completely melted, it should be water-like in consistency. Remove the mixture from the heat and make sure that its temperature does not exceed 235 degrees. Otherwise, it will become rubbery in texture.
During this state, you can start to mold it to fit your chosen pattern.
If you want to explore other methods of plastic molding, you can choose from the following techniques, depending on the type of plastic material that you want to use. However, note that not all of these methods can be followed at home:
Injection molding – This is one of the most popular methods of plastic molding. In this technique, plastic is fed through a screw, heated and melted, then injected into a cool mold. After allowing the plastic to cool and solidify, the halves of the mold are opened and the product is removed. Injection molding works well for making complex plastic items.
Compression and transfer molding – In compression molding, the mold is filled with plastic or plastic powder then heated. The halves are pressed together so as to mold the plastic into the target shape. The same process is used for transfer molding, except that the plastic is partially heated before it is molded.
Extrusion – This makes use of liquid plastic, which is forced through a die to make simple shapes. Then the formed plastic is transported on a conveyor belt to cool it, and it is cut into smaller pieces. This plastic molding process is suitable for pipes and fibers, not for highly detailed shapes.
Knowing how to make plastic molds can help you save a lot of money. Moreover, you can create a mold to fit the shape that you desire to create.