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Author Topic: silicon moulds for small scale items  (Read 5619 times)

boatmadman

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silicon moulds for small scale items
« on: November 05, 2009, 12:32:37 PM »

I will need to make some moulds to cast some small clear resin parts for my current build.

Trouble is, where do I start? What do I use? How do I do it?

Help please

Thanks

Ian
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Seaspray

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Re: silicon moulds for small scale items
« Reply #1 on: November 05, 2009, 12:57:02 PM »

I too would appreciate this information as some parts on a model just don't look right in wood. Etching is beyond me.

A hand made casting is called for especially if there is many parts.

Seaspray
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Bradley

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Re: silicon moulds for small scale items
« Reply #2 on: November 05, 2009, 02:05:45 PM »

Hi Guys,
Have a look at this website - you may find that they cater for your requirements.   :-))
Derek.    :police:
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Bradley

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Re: silicon moulds for small scale items
« Reply #3 on: November 05, 2009, 02:06:47 PM »

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Subculture

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Re: silicon moulds for small scale items
« Reply #4 on: November 05, 2009, 02:43:47 PM »

If it's just some very small parts, you can use normal silicone caulking. A tube can be had for a pound at poundland. Just coat your object with some vaseline, and squirt it over. Once cured, create a simple hardback to support the silicone rubber using some plaster, polyfiller or polyester filler.

andygh

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Re: silicon moulds for small scale items
« Reply #5 on: November 05, 2009, 03:11:58 PM »

Have a look here

http://www.tomps.com/shop/pages.php?cID=5&pID=5

I've used this

http://www.tomps.com/shop/-c-1_7_5.html?osCsid=smhqk0u8qid23aptnjpmp02977

and this

http://www.tomps.com/shop/polyurethane-fast-cast-resin-p-129.html

Best advice I can give? Don't stir in too much air and pour slowly. It's very easy to do so long as you have an accurate set of kitchen scales to measure your mixture. I used vasseline painted on (very thinly) with a brush as a release agent
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andrewh

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Re: silicon moulds for small scale items
« Reply #6 on: November 05, 2009, 05:35:33 PM »

Hi, I was also going to suggest Tiranti for information

I tried this a few weeks ago - was delighted by the simplicity and process.  My saga of discovery - warts and all - is at
  http://www.modelboatmayhem.co.uk/forum/index.php?action=post;topic=20609.0;num_replies=5

Swift summary - I used a 2-part silicone rubber (frankly I used what I had - which was most sub-optimal as it was almost a paste)
I tried both  epoxy and polyester resin - and preferred the results from polyester - filled with microbaloons0

andrew
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Bradley

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Re: silicon moulds for small scale items
« Reply #7 on: November 05, 2009, 05:44:24 PM »

Andrew,
I think that you have got the wrong link shown in your entry for this item - when I clicked on it it just opened the same item  {:-{.
Hope you can understand what I mean  {:-{.
Derek.    :police:
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Guy Bagley

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Re: silicon moulds for small scale items
« Reply #8 on: November 05, 2009, 05:54:15 PM »

use tomps, they are excellent  !!!

( tomps- tony MCguire plaster supplies ) - they have their own website plus they list on ebay too
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Umi_Ryuzuki

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Re: silicon moulds for small scale items
« Reply #9 on: November 05, 2009, 05:58:51 PM »

The really good pictorials were "disappeared".
I salvaged and somewhat simplified the explanations here...

http://www.queensown.org/photo-gallery/?g2_itemId=2224

And Here A two sided mold.

http://www.queensown.org/photo-gallery/?g2_itemId=2223

.

A slightly different two sided mold.

http://www.queensown.org/photo-gallery/?g2_itemId=2267


I pour polyurethane plastics. It is far less brittle than Polyesters.
For the clear casts, I let the silicone molds cure for a week before use.
Otherwise the clear polyurethanes tend to remain sticky..

Several people I know use "LEGOS" to build up their mold boxes for two sided molds.
The LEGOS allow the plasticene clay to be built up and worked, and then pulled out
 of the mold easily. They also make the mold box is rebuildable and reusable.

Avoid any sulfer in your clays.
The sulfer can inhibit the curing of mold material and leave you a gooey mess.
Also, use a good scale to measure portions "by weight".
This also prevents a a bad mix and a gooey mess.
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boatmadman

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Re: silicon moulds for small scale items
« Reply #10 on: November 05, 2009, 06:15:41 PM »

Thanks fella's, and honorary fella - Umi - great help as always  :-))

Ian
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Vintage

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Re: silicon moulds for small scale items
« Reply #11 on: November 05, 2009, 06:21:28 PM »

As has been said Tiranti probably have a good selection of silicone rubbers, another good supplier is Jacobson Chemicals (link below) who have an in depth knowledge of casting & are extremely helpful although I'm not sure if they have a minimum order.

http://www.jacobsonchemicals.co.uk/

Just to add to what has already been said -

Use a polyurethane "fast cast" resin for casting - the de-mould time is extremely quick & the results will be far better than using Polyester resin.

When pouring your Silicone, to form the mould, avoid pouring directly over the subject but pour from one corner of the mould box & allow the rubber to flow over the item - this way you're far less likely to have problems with air bubbles. Remember that air will get trapped under any undercuts so avoid this by tilting the mould as you pour, if that makes sense...

It'll help, assuming you don't have access to a vacuum chamber, if after pouring the silicone you put the mould box onto something that'll vibrate slightly such as a scroll saw bed - this will encourage any air bubbles to rise to the surface before the rubber cures.

Hope this helps

Mark.
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andygh

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Re: silicon moulds for small scale items
« Reply #12 on: November 05, 2009, 07:21:59 PM »

Quote
if after pouring the silicone you put the mould box onto something that'll vibrate slightly such as a scroll saw bed - this will encourage any air bubbles to rise to the surface before the rubber cures.

I've never found this to be a problem when using Tomps silicone

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Nordsee

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Re: silicon moulds for small scale items
« Reply #13 on: April 26, 2010, 11:49:04 AM »

If it's just some very small parts, you can use normal silicone caulking. A tube can be had for a pound at poundland. Just coat your object with some vaseline, and squirt it over. Once cured, create a simple hardback to support the silicone rubber using some plaster, polyfiller or polyester filler.
To make the mould box, use Lego. Make a suitable size box allowing about 1 cm outside all around  the part.Smear inside of Lego with release agent, Talcum Powder or Vaseline. Put a layer of Silicone in, place the part onthis base and fill. Tap the sides of the box to remove air bubbles, or coat the part with silicone first. Leave until cured, then break the Lego away just leaving the mould.If you have lots to make, then use this Master to make 3 or 4 and make another larger mould so you can produce more in one pour.You can then sell them to your Club Mates at an exorbitant Price!!
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malcolmfrary

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Re: silicon moulds for small scale items
« Reply #14 on: April 27, 2010, 10:35:16 AM »

One of my club members needed a lot of repeat items for his Duke of York - he got his moulding bits and pieces from his local Hobbycrafts.  http://www.hobbycraft.co.uk/Home.aspx
If they are all laid out the same, up the stairs, first aisle on the right.
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davidm1945

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Re: silicon moulds for small scale items
« Reply #15 on: April 27, 2010, 06:37:04 PM »

Just a thought - how do you stand re copyright with this? Obviously it's not a problem if you have made the original part yourself but I should think that there are some retailers on the forum that would not be happy if you started copying their products.

      "Yes Guv, I know that I only bought 1 mushroom vent from you and there are 12 on my model, but......!"

Dave.
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Subculture

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Re: silicon moulds for small scale items
« Reply #16 on: April 28, 2010, 10:55:25 AM »

I think that boils down to scruples. It would be very hard for anyone to prove you had knocked off their work, but it is polite to ask permission before you go and copy. Some are okay with this, as long as you don't sell them on for profit, or undercut them. Others won't like it.

Guy Bagley

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Re: silicon moulds for small scale items
« Reply #17 on: April 28, 2010, 11:35:43 AM »

as far as i am aware so long as you dont sell items then there is no copyright issue, if you own the part ( the master as it were ) that you are moulding and you are not selling on replicas there is no issue as these are only for personal use..

 the issue only arises when you are retailing the item or passing their item off as your own....- i know as i have had people copy my goods  and sell them as their own !
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