Just curious to know, lately we have been on a mould building marathon and we started looking for other materials to use on creating the flanges. Usually, we build the flange out of foam or left over core materials and apply a body-coat to it, wet sand smooth and then paint the plug with EZ sanding duratech primer.
Long process sometimes, we just finished a mould for a 7 foot dash for a low volume luxury SUV proto-type. That took nearly 27 man hours to build the flanges on the plug.
I like laying up 6"- 10" wide strips of fiberglass mat on glass. Amount of layers depends on flexability requirements. But usually 1 or 2 layers of 1 1/2 oz. mat.
Normaly flanges out of mdf then cover in 2 inch High temperature flash breaker/composite tape which works a treat as does PET Adhesive backed vinyl sheet and Mylar self adhesive plastic film on mdf for larger parts with not to much shape. Only draw back is when you pull the part off it often lifts the film as well but thats not a worry if its for mould construction or one off part.
I am currently pondering the best way to flange up a spiraling decreasing circle (think a large ammonite about 1.5 m dia) massive amount of time to do very fiddly flanges as gaps reduce and contored surface. Have been thinking along the lines of building a dam around the plug on the table then pouring in casting resin or plaster of Paris (which might be very cost effective)in to fill up upto the midway parting line to create the initial flange. I would be interested to hear if if anyone has tried such a method.
I used MDF everywhere, usually with only wax as a release, sometimes some resin or paint, depending on the plug.
But since I work at a car factory, with loads of sheet aluminium laying around, I use that. Both are ok.
I hear that, I ask because on smaller parts I have done just that, provided there are no undercuts I just glue the part (original) piece I need to make the mould from not flanged and use model clay to close any gaps. I box it and pour replicast on it, pull it from the table, pop the part out and I have a plug with flanges all smooth to make my mould from.
We have this part now in which is roughly 3 feet long, 4 feet high with a depth of 3.5 feet. The idea of flanging it makes me feel tired All that sanding…
The mylar does help, we have done the bondo route and just squeegie it under the mylar to get it smooth and get the air out but it still needs sanding at the seams, especially when there is drafts, bevels and radius’ to contend with.
True, but we build moulds for various companies besides our own use, like the surface of the mould for the part, if the flange looks off a little they def mention it, so we have to treat the flange as equally as important as the rest of the mould.
super late post but id also like to add aluminum flashing works great. I use the 6" stuff from home depot and then i use a break to bend the edge 90* for added rigidity. Worked well for me. You have to be easy on the pressure for the first layer of FG but ones the first layer is cured its plenty sturdy
I use MDF most of the time. I saturate it with epoxy resin so it soaks in. I brush the surface with resin and heat it gently with a heat gun. I keep on adding resin until it won’t soak in anymore. Then I polish it with a random orbit sander. I use the Frekote FMS sealer and 770-nc release on it.
In general I try to put the part on a flat sheet, then fill out the eventual gaps with modelling clay. Sometimes you need to make the flange curved somewhat, to conform to the shape of the part.
Especially with RTM Light you want the flange to be relatively straight, smooth and without sudden changes in direction.
Recently completed some plugs with Durester cg I sprayed four coats on to my mdf flanges for my plug I then sanded back with 320 buffed and waxed and it worked well. In fact I was not expecting it to release so well as it was quiet thin in places after sanding back. For the plugs the Durester worked well I applied it on top of a regular 2k highbuild.
All that sanding…