Moulding and Casting your own parts

[roymattblack]

This thread is based on my moulding and casting of parts for my large scale model cars but could be used by anyone, for making any parts for modelling.

You will need a few simple things first:

1: Moulding Silicone.

2: Casting Resin.

3: Plastic mixing cups - large spray can lids are ideal.

4: Lolly sticks and cocktail sticks.

5: Plastic boxes/tubs etc to use as a mould box.

6: Plasticine.

Right.

Let's get to it....

First, have your master you want to duplicate - I'm suggesting you make your OWN masters.

Ideally, parts that have one flat side that will be able to lay flat in your moulding box.

Use a box just a BIT bigger than your original. A big box uses a large amount of moulding silicone.

Complex '3d' shapes with hollows and cut-outs are best avoided. This is a BASIC guide after all !

Stick the part with D/S tape or plasticine to the bottom of your moulding box.

If you don't, they might 'float' in your silicone mix.

Mix your Silicone and catalyst in a plastic cup or spray can lid so when you've finished and the rubber has set, the surplus can just be peeled out of your cup so you can use the cup again.
Follow the mixing instructions.

The mix should end up a nice light blue - NOT swirly or streaky...

This is the silicone mix I use. The tub and catalyst shown is 1kg and costs about £12 with delivery.
Find it easily on Ebay. Make sure you get the one shown...

This is NOT how your mix should look.......

Work fairly quickly as the silicon has a useful mix life of about 5-10 mins depending on temperature.

When the mix is an even colour, pour it over your master slowly, making sure it gets into all the nooks and crannies.

Use a cocktail stick to delve into your mould, poking in all the little places where there could be trapped air.

A good bit of poking here pays big dividends.

As air bubbles rise to the surface, you can pop them.

When the mould has set - about 30 mins or so, you can tell by poking it with your finger.

The silicone will feel like fairly hard rubber.

Peel the mould out of your box and turn it over.

The picture shows two differential halves I copied, still in the mould.

Pop your originals out of the mould.

They will come out easily and cleanly.

Looking at your mould, you should find no odd hollows caused by air bubbles.

Poking with the cocktail stick paid off.

If you are only going to make one or two duplicates, you can use your new mould straight away.

If you plan to keep the mould and use it a lot, let the mould 'settle' for 2-3 days before casting with it.

This is the resin and catalyst.

I've used several types and this one is by far the best and easiest to use.

Make sure you buy the FAST CAST - ORIGINAL FILLED - WITH NO ADDITIVES/COLOUR ETC.....

The two bottles above are just over £20 delivered, but you get a lot! The bottles are about half a pint each.

Mix the liquids about 50-50.

That's what I do and it works great.

Mixing the liquids together fully is CRITICAL.

If you don't, the resin will go 'sugary', sticky, and be a pain to clean out of your mould.

Again, pour the mix slowly into your mould, a small layer at a time, poking each layer with a cocktail stick in all the little hollows.

When your mould is full, leave it to harden.

Again, about 30 minutes.

Make sure you mix enough resin to fill your mould properly.

If you find you haven't mixed enough, DON'T mix more and pour it in.

Your mix will not be identical to the first layer, and the 'join' will be sugary and sticky - useless.

Let your first layer of resin harden and THEN top up the mould with more resin.

'You can't see the join' - as someone famously used to say.

Hopefully, all the above makes sense and is useful to some of you.

Of course, you should scratch make your masters - actual copying of kit parts would be frowned upon. it's not that daunting if you need several copies (as I did with my Dunlop wheels) as you only make one, and then copy it.....

Have fun.

Any other questions, just PM me.

Roy.

Edited March 26, 2015 by roymattblack

[DaveCromie]

Roy

thanks for such a concise description of the process you use, this might just tip me over the edge into trying casting!

Mods

Any chance this can be stickied please?

DC

[Fazer]

great tutorial Roy,

It's a slippery slope to do your own castings as I started to cast my own parts the same way & then got so interested that I went on to make my own vac chamber & pressure pot... :doh: :blink2:

Mark D

[vinnie the panda]

Well that's got me fired up to give casting a go, I've wanted to do some wheels for ages now. Excellent tutorial thanks

[toms111s]

Great post Roy, I want to make some copies of wheels for an aircraft and was curious about how to go about it. Thanks for taking the time to explain how you do it.

[BritJet]

Hope you don't mind me adding a couple of things to your excellent tutorial based on many years of resin kit production.

1. After mixing the rubber use an old/cheap paintbrush and coat your masters as this helps to stop any stray bubbles attaching themselves to the masters. Work the rubber into any cavities etc. using the cocktail stick as well.

2. Pour the rubber slowly into a corner of the mould as fewer bubbles will be trapped especially near the masters.

The rubber will produce better moulds if you can de-gas it in a vacuum chamber, but for one-off/low volume work this isn't necessary.

Steve

[Rickpadwick1801]

Hi Roy,

Can I ask how you create your masters ?

Is this the kind of technique which could be used to create my own resin models based on my own designs ?

Cheers,

Rick

Edited April 17, 2015 by Rickpadwick1801