Casting A Mould

[wavodavo]

Hi

I have a model part that I would like to make a mould for to produce a few others. What's the best and easiest way of doing this? I have read other threads and can't decide which epoxy resin to use and mould material but plasticine sounds good for this.

Cheers

Dave

[Alex Gordon]

G'day wavodavo.I seem to remember reading in SAM Guidelines many moons ago that Play Doh is the stuff to use,not too hard and easy to remove.Can't recall the make of resin used though.

[wavodavo]

Thanks Alex for the info, I'll try playdoh first.

[Happy Martian]

You could use Oyamaru as the moulding compund. It's a one part polymer that when heated in boiling water allows you to impress an item into it. When the Oyamaru cools, it keeps the shape of the part you need. When you've got enough parts made up in your resin of choice, putting the Oyamaru back in hot water to make it soft and reuseable.

http://www.artclayshop.co.uk/product_details_183.htm

[Alex Gordon]

G'day Happy Martian,this stuff sounds like it could be worth a try. If warmed gently could it be used for repeat work without damaging the mould?

[Happy Martian]

When the Oyumaru cools, it becomes solid, like a silicon mould, so you can make as many parts as you need. There is no need to reheat the stuff unless you want to make new moulds. One thing I forgot to mention is that when the Oyumaru is solid, you can push a second heated piece onto it to create a two part mould without needing any release compound.

Just found this PDF document which may help PDF

[Alex Gordon]

Hmmm. Got me thinking. Thanks Friend,will be having a play with this when I can source some.

[bootneck]

I purchased some Oyumaru and I have already been able to mould a few small items.

A mould can be produced in less than 15 minutes and is cool enough to start pouring resin into within a couple of hours (even less on cold days).

My working scale is generally 1/144 and I have been able to cast doors and side windows for my helicopters. This means that I can now model them with doors open and then detail the interiors.

The same principle works for the side windows as I can now cast them in clear resin and place them in the 'slid back' location, again exposing the cockpit area.

I've added a couple of images below. The new door is positioned temporarily with double-sided tape to allow me to identify where to trim etc.

I'm just off to order some more of this stuff, Thanks Happy Martian

Mike

(Bootneck)

Oyumaru shaped with door impression and example of resin door waiting clean up and painting

resin door positioned for fit

[Happy Martian]

Glad I could help, Mike. It certainly seems to be a useful addition to the toolbox. And speaking to a guy in the US, he reports no effect on the Oyamaru from the reaction heat of two part polyurethane resin. So this is certainly a quick alternative to RTV Silicone.

The door appears to be extremely thin. Is it a single piece mould or are you using 2 piece moulds to force the thickness of the resin ?

Andy

Edited February 24, 2010 by Happy Martian

[bootneck]

Hi Andy,

the mould is just a one-piece item, as it looks in the photo, and I just pressed the original into it; like you would do with plastacene.

The mould, once you press it to the master, easily shapes to whatever form provided.

As to the thickness, or thin-ness in this case, I just painted a layer of resin into the depression as the required size is so thin.

I have added another image below which shows how thin the door is (stood upright) and also my next mould which shows the side windows, for a Wessex HU.5 helicopter, plus some nose cones.

These cones are for me to convert some Revell F-4E/J Phantoms to F-4J's or F-4K's for my flight deck project.

Mike

Oyumaru mould for helo cockpit side windows plus Seaking doors.

[SPerx]

There is a good outfit called TOMPS who sell RTV rubber in various formulations and 2-part casting resin packs. You can order on-line; do not need to buy idustrial quantities; they deliver quickly; and you can phone up and get advice. Oh, and I don't work for them.

http://www.tomps.com/shop/index.php

[Happy Martian]

I agree, SPerx. I can recommend Tomps for their customer service as I order resin and silicone rubber from their eBay store on an almost quarterly basis. But for the majority of modellers, who wouldn't use 2 litres of RTV in its lifetime, Oyamaru does seem to be a simple entry into mould making and flexible enough to be re-useable to create new moulds where RTV moulds are not. Plus, for one offs or test shots, it's a perfect option.

[Vaughan]

Hey Guys

This is such a brilliant site. I am looking to do some moulding and casting of my own - just simple stuff.

Read this article and its everything I need (for the moment at least)

Thanks for the discussion and clear advice

Regards

Vaughan

[ScainaR620]

Hi Andy,

the mould is just a one-piece item, as it looks in the photo, and I just pressed the original into it; like you would do with plastacene.

The mould, once you press it to the master, easily shapes to whatever form provided.

As to the thickness, or thin-ness in this case, I just painted a layer of resin into the depression as the required size is so thin.

I have added another image below which shows how thin the door is (stood upright) and also my next mould which shows the side windows, for a Wessex HU.5 helicopter, plus some nose cones.

These cones are for me to convert some Revell F-4E/J Phantoms to F-4J's or F-4K's for my flight deck project.

Mike

Oyumaru mould for helo cockpit side windows plus Seaking doors.

Hello Mike

May i ask what resin you are using as and trying to get the right one for casting plastic parts for my plastic model kit Axles i need for my Scania R620 so that i can make it into a 6x4

Many thanks

Nick

[Happy Martian]

Nick, you'll find most folks use a 1:1 ratio polyurethane resin. And for your purposes, I'd probably recommend this as the most resilient. As Sperx mentioned above, Tomps is a very good company to buy from. But they're not alone. There's Sylmasta, Alumite and a host more.

Do you have any ideas what moulding compound you're going to use ?

Andy

[emlra]

Impressed (not intended as a pun!) just ordered some.

Do you need to use a release agent, if so is there a cheap recommendation for small scale usage?

Rex

[ScainaR620]

Nick, you'll find most folks use a 1:1 ratio polyurethane resin. And for your purposes, I'd probably recommend this as the most resilient. As Sperx mentioned above, Tomps is a very good company to buy from. But they're not alone. There's Sylmasta, Alumite and a host more.

Do you have any ideas what moulding compound you're going to use ?

thanks is there a name to this polyurethane resin please ?

Yes going to use Oyumaru Moulding Compound as me mould as reading on this page how good it is and like the idea of heating it up to reuse

Edited January 11, 2011 by ScainaR620

[Happy Martian]

Rex,

If you're using Oyamaru, no release agent seems to be needed. I've used the same mould 7 times and have had no degradation issues. Should you feel you do need some, household vaseline should be adequate as long as its not applied too thickly.

Nick,

No specific trade name. Here's a link to the Tomps stuff http://www.tomps.com/shop/polyurethane-fas...bvrg3dvhupbm0p1

Andy

[Karl]

I've successfully used plasticine in the past for creating a mould for small parts.

I moulded a replacement instrument panel for my Dynavector Javelin (the IP had gone missing from my kit) using the 2nd kit I had in the stash for the pattern:

Turned out ok I think, though the picture isn't too good.

PS:

I did end end up with a replacement IP from Taro at Dynavector though, not because my mould wasn't good, but I'd already sent him an email asking for a replacement if he still had any spares

Karl

Edited January 12, 2011 by Karl

[periklis_sale]

what resin do you recomend to use and where to get it from?

i am planning to get some Oyumaru Moulding Compound but i am confused about what resin to use?

Oyumaru Moulding Compound is it only good for small flat-ish items? If you wanted to mould a figure's head is it good?

[Happy Martian]

Karl, I agree. Plastiscene, Blu Tack and even artists clay can be used. But unless you are very careful removing the part, the mould could be damaged. With Oyamaru, that worry is removed as the polymer becomes hard after cooling so is more resistant to removal damage.

Periklis, I'd suggest you look at local suppliers as my preferred resin (two part polyurethane resin) is classed as hazardous so would fail to meet many courier companies' policies. Alternatively, try epoxy resin. It should be more readily available and would suffice for smaller parts. If you're looking at heads, Oyamaru should work like any other two part mould. Personally though, for easy of creating the mould and depending on the size of the head, I'd move up to RTV Silicone.

Andy.

[Karl]

Andy is correct - you do need to be quite careful how you remove your pattern from the mould if you use something like plasticine; in some ways it is a limiting factor as to how deep you can cast your parts.

As for a resin, again nice and simple with stuff that I had to hand: 'David's Isopon Resin' and hardener, as used in car body repair with fibreglass. It's relatively cheap and readily available. Just a little gloopy/thick when mixed, you just need to make sure that you pour it slowly in to the mould and try and agitate any air bubbles to the surface.

Karl

[ScainaR620]

So where do you guys do your casting then, do you have a special place to do it as i notice you need to be room temp for the resin to set right

Also do it smell the house out of flumes if you do it indoors

many thanks

[ScainaR620]

Glad I could help, Mike. It certainly seems to be a useful addition to the toolbox. And speaking to a guy in the US, he reports no effect on the Oyamaru from the reaction heat of two part polyurethane resin. So this is certainly a quick alternative to RTV Silicone.

The door appears to be extremely thin. Is it a single piece mould or are you using 2 piece moulds to force the thickness of the resin ?

Andy

So Andy are you saying that this Oyumaru is not attected by the reation of the two part polyurethane resin heating not not effecting then mould

[Happy Martian]

Scaina, I'd probably say that it depends on the thickness of the mould. A thinner mould wall may absorb more heat and allow it to deform but I've used a one-part mould with 1:1 polyurethane resin for multiple parts with no apparent degradation of mould details, even with the exothermic reaction. I've had the same success with a couple of two part moulds as well. I probably would also recommend washing the Oyamaru with soapy luke warm (not HOT) water to clean the mould between uses and it should last for a good number of pieces.

I made this very-quick How-To on a site I co-run and shows the two part moulds I made and the resin parts that were produced. The thickness of the hood and front bumper mould was about 7 mm and there was no deformation. Be warned the parts are rough as it was done for speed but gives you an idea.

I haven't got to the point where the Oyamaru begins to degrade through overuse and hope I don't have to. As I've said before, from all I've read, this shouldn't be thought of as a complete replacement to Silicone Rubber, which has a longer mould life expectancy. But for one-offs or for short run pieces, it's a great little addition.