Silicon casting parts

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thenoizeguy

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I thought I should share my casting process which I am currently busy with.

It all started when I purchased a SANSUI SE 7 Eq from Vleisman a few weeks ago. It had one missing slider knob.
As it had 19 good ones, I thought it would be easy to copy one, and searched the net for different types of casting or moulding.

Going back a bit in my story now, this EQ is part of my AU7 collection which I have slowly built up as I find matching components. The first Item I bought was the SC3330 cassette deck, then the TU217 tuner, AU417 amp and now the SE7 EQ. Luckily, the SC3330 came with the Sansui rack handles, so I had a template to make make copies of these for the amp and EQ. The tuner is smaller, but was also supplied with the handles, so if I find the matching AX7 mixer, or one of the smaller amps, I can make copies of those handles as well.

After watching a lot of YouTube vids, I headed to Herbert Evans to see if they had the bits I needed. They did, but at a price to make your eyes water. The company that makes this stuff is AMT, but if you want small hobby quantities, then you have to pay the price. So after a half hour lecture from the lady there, I walked out armed with a 2 part silicone mix, and 2 part resin mix. Just over 1K !.
Due to the nature of a handle having a closed section, I would have to do a split cast.
So after a lot of thinking, I thought the best way would be to split the cast on its side as in the pics, and do an accurate first pour, making sure the handle was perfectly level.
Dowels were suspended from the top, so that the second pour could lock into the one under it when it was set.

The first pour used up ALL of the silicone mix, so it was back to Herbert Evans for another R680 !

You need a release agent to coat the cured bottom half, to stop the top pour from sticking to it. A bit of researched mentioned that Vaseline does the job perfectly, and it did.

I did a few test samples of the sliders first, to see how the resin sets. You literally have less than a minute after mixing and stirring, to do your pour. This stuff goes from extremely runny, to rock hard in about 2 minutes.
Lots of disposable cups and containers needed here !

Here's a few pics of the process.


 
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