A Little Manufacturing Run
Trying out Silicone Molding
Additive manufacturing, i.e. 3D printing, is getting increasingly popular and with new research everyday on methods and processes, its applications are only increasing. One thing that is not frequently discussed is how expensive 3D printing can be especially when the printer is not owned.
When I am asked on low-scale manufacturing runs (say 20–100 pieces) by someone in Nigeria, my first reply is never to use 3D printing. As the process does not scale, the print has to be done as many times as there are parts; this process is time consuming as well as expensive.
My first recommendation is Silicone Molding. Silicone is sold in two parts that after mixing in equal volumes can cure depending on the grade. The best part is that silicone performs very well both as a part (recommended if you need the part to be soft or have sealing properties) and as a mold (for a harder material like polyurethane).
However, most of the people do not end up using this method because they assume it’s much harder. I decided to do a tutorial here, as this is the hardware version of embedding code.
Requirements
Two parts of silicone
Measuring and mixing jars
Mold release spray
Gloves and a face mask
Mold
For this mold, I used silicone for the part. In the future, I will do another with silicone as the mold. In this case, I 3D printed a mold with ABS. Designing the mold can be done using the part’s design in SolidWorks (the easiest way is to build the mold as a configuration within the same file).
It is important the mold is in three parts: both cavities and a core (in green). A core is a ‘sacrificial’ part and is where the silicone is poured through.
Process
Spray the mold with mold release spray, it aids easy removal. Easy removal also depends largely on the design of the mold.
Mix the two parts of silicone. The two parts must be equal, and be careful when mixing to avoid air bubbles within the mixture.
Pour the mix into the mold, a little at a time. Time is best done with a funnel; it is advisable to allow for air bubbles to escape.
Close the mold out with the core and wait for the cure time to pass. The silicone grade I use takes only four hours, but if you go for another type for any reason this time might be longer or shorter.
Break apart the mold using a sharp edge.
Test your mold.
Below a side-by-side comparison of the same design 3D printed and silicone molded.
One obvious benefit is you can go on to make more parts using the same mold as long as you have silicone which also comes in large tubs. It is much cheaper and simple. The most important thing is getting your mold right, especially the parting line, so as to optimize the design of the part.
If you are designing a product in Nigeria and are thinking of a low-run, you should try this method especially if you are designing a wearable or a product to be used with food. It will bring the manufacturing cost down and keep IP in house; you should also ask an expert.
You are invited to the sixth meetup of Hardware Lagos on Saturday, August 19th 2017 at CapitalSquare, Ikoyi. We are discussing manufacturing.
