Monday, August 17, 2009

How to Make Model Car Kits and Figures

It's nice that Hobby Link Japan recently put up a video section in their site and started posting videos relevant to the modelling culture. Just recently they went on a tour of Model Factory Hiro in Japan that makes model car kits out of resin, metal and rubber.

How to Make Model Car Kits and Figures

To make a model they first make a master. If the master is of simple design with only minimum detail, it is hand made with scratch building materials (styrene sheets and tubes I am assuming). For more complex designs with intricate detailing, they make the design in CAD then print it out afterwards in a 3D printer.

A 3D printer is probably the scratch builders ultimate dream tool because you only have to create your design in a computer then it will print out the final 3d object in plastic via extrusion process (usually HDPE plastic in coil form is used as a raw material). Thanks to the RepRap Project, which created an open source 3d printer design, it made cheap 3d printers available to the desktop hobbyist.

Of course they don't sell them commercially since they focus on improving the reprap components. They leave it up to 3rd party developers like Makerbot to profit off of their work. Model Factory Hiro's 3D printer seems to be of commercial quality, meaning probably frikking expensive.

After a master is made they cast it in resin using silicon rubber molds. Their resin casting process wasn't shown but based on the equipment seen at the show it looks to me like they use vacuum and pressure chambers to cast their models. Vacuum and pressure chambers are quite nifty for producing quality resin casts because they get rid of the air bubbles in resin and ensures that the resin fills all the spaces of the mold. The problem with a Silicon Rubber mold is that they are expensive and wear out easily after only 20 uses since the resin attacks the mold. They are easy to use and make however.

How to Make Model Car Kits and Figures: Vacuum Chamber

For thin parts like wings and suspension they use white metal for their casted material. They first make a metal master using silicon rubber then use it to make a rubber mold that goes through the vulcanization process. In vulcanization, heat and pressure are applied to rubber so that it becomes strong and stiff. That is also the reason why a metal master is needed, so that it can withstand that heat and pressure.

Once the rubber mold is made it is placed in a spinning machine when casting, this is so that the poured white metal, via centrifugal action, will spread evenly inside the mold.

For even thinner parts, photo etching is used. Those aren't made in Model Factory Hiro, but rather outsourced to another company. But what was shown was that they use CAD to create design then submit it to the factory, who will use the design to make the final product by etching the design into a thin sheet of metal using acid.

That's one thing I really like about HLJ compared to the other online stores in Japan, that they focus not only on toys, but also on the model kit building hobby. I've been trying to search for stores which carry model making materials, tools and scratch building materials, only HLJ was the one I found that carried all of that. Which is good because you can save on cost of shipping.

Aside from this video from HLJ there is the PLAMO Tsukuro (Building Plastic Models) series in Japan that focuses on the model kit building hobby. They usually feature professional modellers building a kit that they gave them. From there you can see the techniques used by the professionals. The bad thing though is that it is in Japanese. I only know a smattering of Japanese so I can only understand partly what they're trying to say, but I still find it full of good information on the modelling hobby.

My favorite episode of theirs was when they visited one of the figurine building companies and they showed how a custom figurine was built from the ground up, from design, to casting and to painting. Check out the video below updated in youtube.

Basically after a design is selected they choose from a bank of pre-existing silicon rubber molds of figurines and cast the figurine in poly putty. The modeller will then work on this poly putty model using other putties and scratch building materials. I guess they didn't want to show their trade secret, which was how to make a model from the ground up.

Based from the video from HLJ and my experience, I could only deduce that they could be using either CAD to make the model then printing it out on a 3d printer, or sculpting it manually or with a desktop CNC milling machine using modelling boards, or sculpting it with modelling clay then baking it to harden.