Silicone molding, also known as vacuum casting, is a fast and economical alternative for producing small batches of injection molded parts. Usually SLA Parts are used as the prototype, the mold is made of silicone material, and polyurethane PU material is cast through the process of vacuum injection to make a composite mold.
Complex modules can strike a balance between high-quality production results, economical production methods and ideal lead times. The following are the 3 core advantages of the silicone molding process.
High degree of reduction, high product precision
The vacuum casting a parts can accurately reproduce the structure, details and texture of the original parts, and provide high-quality and high-precision injection molded parts of the automotive standard.
Free of costly steel mold
Small batch customization of injection molded parts can be completed without investing in costly and time-consuming steel molds.
Rapid product delivery
Taking JS Additive a as an example, 200 complex modules can be completed in about 7 days from design to delivery.
In addition, due to the good flexibility and elasticity of silicone molds, for parts with complex structures, fine patterns, no demoulding slopes, inverted demoulding slopes, and deep grooves, they can be taken out directly after pouring, which is a unique characteristic compared with other molds. The following is a brief description of the process of making a silicone molds.
Step 1: Make a Prototype
The quality of the silicone molds part depends on the quality of the prototype. We can spray texture or perform other processing effects on the surface of the SLA prototype a to simulate the final details of the product. The silicone mold will accurately reproduce the details and texture of the prototype, so that the surface of the silicone molds will maintain a high degree of consistency with the original.
Step 2: Make the Silicone Mold
The pouring mold is made of liquid silicone, also known as RTV mold. Silicone rubber is chemically stable, self-releasing and flexible, minimizing shrinkage and efficiently replicating part details from prototype to mold.
The production steps of the silicone mold are as follows:
§Paste tape on a flat place around the prototype for easy mold opening later, which will also be the parting surface of the final mold.
§Hanging the prototype in a box, placing glue sticks on the part to set the sprue and vent.
§Inject silicone into the box and vacuum it, then cure it in an oven at 40℃ for 8-16 hours, which depends on the volume of the mold.
After the silicone is cured, the box and the glue stick are removed, the prototype is taken out of the silicone, a cavity is formed, and the silicone mold is made.
Step 3: Vacuum casting
First put the silicone mold into the oven and preheat to 60-70℃.
§Choose a suitable release agent and use it correctly before closing the mold, which is very important to avoid sticking and surface defects.
§Prepare the polyurethane resin, preheat it to about 40°C before use, mix the two-component resin in the correct ratio, then fully stir and degas under vacuum for 50-60 seconds.
§The resin is poured into the mold in the vacuum chamber, and the mold is cured again in the oven. The average curing time is about 1 hour.
§Remove the casting from the silicone mold after curing.
§Repeat this step to get more silicone mold.
Vacuum casting a is a relatively popular rapid mold manufacturing process. Compared with other prototyping service, the processing cost is lower, the production cycle is shorter, and the degree of simulation is higher, which is suitable for small batch production. Favored by the high-tech industry, the vacuum casting can speed up the research and development progress. During the research and development period，the unnecessary waste of funds and time costs can be avoided.
Author: Eloise