Silicone compression molding factory

In this video Dangerous Prototypes and Pax Instruments visit a silicone molding factory in Shenzhen, China:

We recently visited a silicone compression molding factory with our friends at Dangerous Prototypes. This is the same technology used for making our silicone keypads for the T400 temperature datalogger.
I put together a short video showing the overall process. The process begins by mixing a base material with colorant using a roller machine similar to a pasta maker. Then chunks of the material are placed in a mold, which then enters a press. The silicone is compressed and takes the shape of the mold. The mold is then heated and the material cures in a few minutes.

More details at Pax Instruments site.

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  1. Awesome! Great vid. I think materials is just as interesting as electronics. So many modern materials to learn about… Wouldn’t it be great if your local maker shoppe has a bucket of uncured silicone rubber just ready to turn all your rubbery ideas into fruitation? :-P

  2. That was a super fun trip. It was great learning a bit more about this technology, so I can better use it in the future. it actually turns out compression molding is suitable for more than just dildos and keypads. I may use this technology to produce the T400 enclosures in a material with the same hardness as ABS. This may save thousands of dollars if I don’t have to do injection molding. Thanks, guys! :-)

      1. But it would be interesting to see if there are DIY attempts on this anywhere in the world… I would be very interested in news of such endeavours.
        Human ingenuity can sometimes be pretty remarkable, so I would not totally discount the possibility.
        So-so DIY quality obviously would not be suitable for toys *ahem* such as those above, but might be good enough for button panels, or skin for your Terminator robot arm.

      2. A compression mold is significantly cheaper than an injection mold. A factor of 5 or 6. Compression molds can be made for ~$1200, while an injection mold starts ~$4000.

        At this factory the boss showed us prototype molds he said cost 200RMB (~$33). I tried for weeks to get him to explain the limitations for using that, but he never made it clear. I suspect he may have exaggerated a bit.

        However, we also saw some very ridged plastic looking stuff he said was compression molded as well. Later this week or next week we’ll go check out that factory.

        Makers, Hackers, Startups, etc all want the injection molding tooling stamp on their passports, but if compression molding can give a workable widget for tons less I think it is worth researching more.

      3. For very short runs, you can get away with a simple aluminium mold. The cost is vastly reduced since the main cost of building a mold is time, not materials, and you can work with aluminium a lot faster than with hardened steel. But durability and surface finish are greatly reduced. Any decent 3axis CNC mill, and a decent drill press to dril the heating circuit and you are almost done. The construction of a prototipe is posible for some hackerspaces. Of course, forget complexity.

        Then you need to find somebody to press the parts for you. Again, the main cost will be time. They will bill you a fixed fee for asembling and disasembly the mold in the press, and all the preparations necesary for your run. The actual run time and materials will be lesser of the costs.

        So, if you want a 100 parts run, with a part price of maybe 30$ part, it’s doable.

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