Two-part silicone molds are also called male and female molds, the one with protruding parts is called male mold and the one with concave is called female mold, and the two can be combined to form a closed cavity when used. This process is suitable for the production of irregular and difficult to open models of products. The following gives you examples to share two parts of the silicone mold-making operation steps, so that you understand this process flow and attention.
Process principle: Design the parting line of the master model, put half of the master model into the clay according to the position of the parting line, then trim the clay, build a mold frame to enclose the entire model, and pour rtv-2 silicone raw material After waiting for curing, part of it is completed. The other part reverses the master model and repeats the steps just now.
Tools and materials: tin-cured silicone, rubber master model, release agent, plasticine/clay, building blocks, polyurethane casting resin, vacuum pump, electronic scale, measuring cup, stirring bar.
1. According to the size of the rubber wheel model with blocks to build a suitable mold frame, and use clay to fill the bottom flat, as shown in the following figure. Note that if platinum-cured silicone is used, sulfur-free clay should be used, otherwise it will cause the silicone to undergo a poisoning reaction and cannot be cured.
2. Put the wheel model into the clay, usually press into the clay at half the height of the model when it is placed horizontally. Here we take the designed parting line as the standard. Set positioning holes in the clay around the model. The positioning holes make it easier to close the male and female molds when they are combined. And reserve a material casting entrance at a suitable location.
3. In order to prevent the silicone and rubber models from sticking together and being difficult to separate, a mold release agent can be applied to prevent mold sticking.
4. After preparing the above steps, you can start to configure the rtv-2 liquid silicone. According to the size of the master model, use an electronic scale to weigh out an appropriate amount of part A of the rtv-2 silicone, and then add the curing agent of part B according to the proportion, and stir it evenly. Note here that if there is no stirring Uniformity will result in non-curing or incomplete curing of the silicone.
5. In order to make silicone molds without air bubbles, the mixed and stirred liquid silicone should be put into the vacuum pump for defoaming first.
6. Pour the vacuum defoamed liquid silicone material into the mold frame, generally covering the highest point of the master model by about 1~2 cm.
7. Wait for about 10 hours for the silicone to cure completely, and then the male model part of the silicone mold is finished. The curing time is related to the curing agent ratio and temperature.
8. Separate the clay from the silicone, turn the male model part upside down and start making the female model part of the silicone mold.
9. Repeat steps 4~7 to complete the silicone mold for the female model part. Here, we should pay attention to the mold of the male model part of the mold must be coated with a mold release agent before pouring silicone to avoid the problem of silicone sticking to silicone.
10. After the silicone is completely cured, the mold frame is removed, and simple trimming is performed with scissors to complete the production of the two-part silicone mold.
11. Combine the produced male model and female model silicone molds according to the location of the positioning holes, and then wrap them with tape to prevent them from being dislocated by force and the casting liquid material from penetrating out, or they can be fixed with clamps as shown in the figure.
12. Mix and stir the polyurethane resin material in a ratio of 1:1, and pour the silicone mold cavity from the reserved injection port. If the operation time of the polyurethane resin material is too short, you can put it in the freezer for a period of time before taking it out for use.
13. At present, most of the polyurethane resin materials on the market can be cured in about 10-15 minutes. After curing, the resin wheel is removed and the entire process is completed.
