Moulding the Voight-Kampff machine - help needed!

[Birdie]

I will soon be molding my Voight-Kamph machine build, and I could really use some advice.

The plan is to make a one-piece RTV mould, with the intention of using it to make hollow fibre-glass shells.

I have never made a mold this large before. To the experts, what sort of shore hardness RTV should I use? Advised wall thicknesses? After molding, do I need to build a clay mould-case to support the mold when glassing?

When I was using THstudios VK mould, he had used very soft and quite thin rubber, with a hard clay case, but I still had problems with warping, since the rubber didn't key into the case too well.

Any advice would be appreciated. The master is approx 13"x9"x5"

This isn't quite the completed piece, but gives a good idea of what we're looking at:

 

[swgeek]

I would go with a 30A or 40A rubber with about a 1/2 " thickness. I would recomend screwing the VK to a board, covering it with plastic wrap and then lay on a layer of 1/2" clay. Once you have the clay even and smooth(ish) put on some clay keys ( although you may not need to with the complex shape of the VK). Then spray some clear spray paint on to seal the clay. Next I would spray some release on the clay and lay down the fiberglass. When the fiberglass has set up drill a series of holes along the edge/flange through the FG and the board. Pull the fiberglass off, take all the clay off and put it in a bucket (you can use it latter to estimate how much silicone you will need). Next I'd drill some vent holes in the fiberglass shell and drill a pour hole in the highest spot on the mold jacket. Bolt the Fiberglass jacket back to the board, seal the edge where the FG meets the board just to be sure, pour the silicone let it cure and you have your mold. That's how i would do it anyway. Good luck.
Jonathan

 

[swgeek]

Oh, one thing I forgot to mention, when you do the clay layer, lay down a strip of clay 3/4" to an 1" thick and about 1 1/2" wide all along the base of the VK. Also if you put a raised edge on the clay flange , like a step up, it will key into the FG when it's silicone. If that makes sense.

 

[Birdie]

Sounds like a plan :thumbsup

I need to get this right first time (can't afford a second), and I really appreciate the assist

 

[swgeek]

I changed which side to drill above (I started thinking). If you drill the fiberglass jacket side and pour from there you will get a better mold, especially if you can't degass your silicone.

 

[Propsjonnyb]

Hi Birdie ,
am very interested in a working VK machine myself , have been persuing the elusive machine now for almost 20 years - so any details?? are you going to offer a kit or full build up? you said you bought Tylers original molds any chance of a pull set ?? I had to ask !! I have a VAC former available, but it will only handle sheetsize 24'' x 11'' max PM me with any information

regards,

Propsjonnyb

 

[28injection]

Does it come with the wheely bin? Sorry :lol

The shape looks accurate.

Good luck with this.

 

[Birdie]

After letting this one simmer for the best part of a year, this is gonna be my next project to try and get finished, now that the weather is looking up

I will probably be using Tyler's moulds for the arm/eyepiece, everything else is pretty much going to be scratch-built.

Right now I intend to go the vac-forming route with the shell, and see how I get on.

As to whether there will be a kit - I hope so. Sorry not to be more specific, right now i need to put some time into playing around with my vac-former, which has been sitting around for nearly six months since I bought it, without me touching it. :rolleyes

Hope to be able to update soon.

Edit: that wheelie bin actually got stolen since that picture was taken. You'll bee pleased to know the model wasn't still sitting on it. Wheelie bin forming technology would be great for this project.

 

[robsam]

Well You are doing a great job. As SWGeek Suggested, you can go with his idea. Screwing the VK to a board & covering it with plastic wrap will give you positive results. Spraying will give you a smart move.

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Plastic Injection Molding