Alternative mold making materials

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#1

I have been experiencing a few problems with a couple of my molds. No matter which type of release agent I use I keep damaging my molds in certain areas, this damage is never on the flat part of my mold but is on protrusions or on sharp radii areas. One mold has been remade about 6 times and the same problems occur. I have used the following release agents :

Meguiars M-08 Mirror Glaze
Meguiars M-08 Mirror Glaze + PVA
Easylease Semi Perm
Easylease Semi Perm + Meguiars + PVA
Easylease Semi Perm + PVA

Now I’m sure it’s not my mold making process that is at fault here because I have many molds that release perfectly with no damage at all. BTW I’m using Epoxy and glass for my molds.

I have been exploring if there are any other materials that I could use to make these molds, ideally I would like to use aluminium but the cost of having these made for me is too much. So I have been thinking about other plastics, namely ABS or Polyurethane. I have read that it is easy enough to make a liquid ABS by dissolving ABS shavings in acetone. I have also found a liquid Polyurethane resin. Do you think any of these two materials would be any good for making molds? Would they be tougher than epoxy? Or is there any other materials I could use?

#2

Polyurethane: forget it.
ABS: never seen it used, probably because it is not chemically resistant.

What is wrong with your moulds? These are epoxy and glass, but what epoxy, and what glass. How is your mold making procedure?

#3

I was afraid ABS would not be any good because of it’s poor chemical resistance. Are there any other thermoplastics that could be used? How about polypropylene? good chemical resistance and a relatively low melting temp so not too difficult to mold?

The problem I am experiencing is the gelcoat sticking to the new part. Like I said this is not a widespread occurrence, just in a few places namely place where the mould has raised areas or corners of radii. My mold making procedure is as follows:

  1. Prepare plug with Maguiars 8 wax, sometimes I also use PVA.

  2. Apply epoxy gelcoat as per manufacturers instructions, which entails applying 2 coats, waiting for the 1st coat to gel to a tack free state. I also degas the gelcoat.

I use this product http://www.ecfibreglasssupplies.co.uk/p-2166-clear-epoxy-gelcoat.aspx and here is the data sheet http://www.ecfibreglasssupplies.co.uk/images/PDFs/clear_epoxy_gelcoat.pdf

  1. Apply 1 layer of surface tissue (http://www.ecfibreglasssupplies.co.uk/p-664-surface-tissue.aspx) The epoxy laminating resin I use is this product http://www.ecfibreglasssupplies.co.uk/p-2168-general-purpose-epoxy-laminating-resin.aspx and here is the datasheet http://www.ecfibreglasssupplies.co.uk/images/PDFs/epoxy_laminating_resin.pdf

  2. I then apply one layer of 200gm plain weave E glass cloth (http://www.ecfibreglasssupplies.co.uk/p-330-glassfibre-cloth-200g-sq-mtr-1mtr-wide.aspx)

  3. I then apply 5 layers of 290gm plain weave E glass cloth (http://www.easycomposites.co.uk/products/woven-glass-fabric/290g-woven-roving-glass-fabric.aspx) and finish off with another layer of 200gm plain weave E glass cloth.

#4

Hi
What do you think think about this mold making material. Its doesnt shrink can be heated to 120º and is very cheap?
Its some Acryl based based material.

http://www.denacoimports.com/

#5

I know this material very, very, very, very well. (cannot say more at the moment, you do the guesswork or PM me).

A very nice system, but do stick to the instructions to make it work, please.

#6

Marc,

These materials seem OK to me. Chipping might occur due to too large thickness of gelcoat (especially difficult in inner corners). Postcuring does help somewhat in that respect. Hope this helps.

#7

The gelcoat datasheet states a maximum thickness of 2.5mm should be applied, is a thinner gelcoat preferable to a thicker one? what do you feel would be an optimal thickness?

I have sent you a PM regarding the polydur.

Thanks for your help.

#8

Keep the gelcoat thin. As it is epoxy based, it does not need thickness to cure properly. (polyester does).

Try keeping close to the 0,5mm, and apply 2 layers. Will save some money as well. Also, with 2,5mm, the gelcoat is quite thick compared to your mould, which is quite thin. This might cause some of the cracking.