Epoxy Laminating Systems

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Since mass casting methods are only practical for smaller tools, because of factors such as weight, cost, and shrink, epoxy fiberglass layups are much more common to construct larger tools and molds.

We’re going to demonstrate a very basic layup, using our Freeman 705 epoxy surface coat and Freeman 605 laminating resin to construct a simple, rectangular layup on a flat board. The basic principles shown here will apply to nearly all epoxy fiberglass layups, regardless of their size and complexity.

Our board has already been treated with Freeman Wax Release and PVA Mold Release. For proper application procedure, please refer to our other video on this subject.


Applying The Surface Coat layer

We begin with our application of the surface coat directly on our part. We are applying this with a white bristle throwaway brush whose bristles have been cut in half in order to create a stiffer brush. Notice we aren’t applying this like paint, but rather we are flowing it on, creating a layer of material between 1/32 and 1/16 of an inch thick.

These materials do get hot when they cure, so we are careful to avoid large puddles of material.

Normally, you’ll want to apply two surface coat layers to make sure your part is covered with at least 1/16 of an inch of material. This is especially important when you are working on vertical surfaces. Plus, you will want the surface coat layer thick enough in case you need to perform any touch up work later. If a layer of surface coat is too thin this may expose the fiberglass cloth underneath if any repair work needs to be complete on the tool face.

The almost tack-free state

Before applying each additional layer of surface coat, our goal is to reach an almost tack-free state. This is the point where no material comes off on our glove, yet our finger does leave an indentation in the material itself…as shown here.

The reason for this is we’re setting up for the next layer of material. You want the first layer to be hard enough that the second surface coat does not push thru the initial layer, but is not fully cured so good adhesion is obtained between the two layers.

Earlier, we had tested the material and found the epoxy to still be too tacky – notice the material coming off the part and onto the glove.



Applying The First Layer of Fiberglass Cloth and Laminating Resin

Before applying the laminating resin, we cut our fiberglass cloth to the correct width and length using standard scissors.

Of course, we also need to mix our laminating resin. Since this is an uneven ratio material, we followed that procedure. For more information, please refer to our other videos on weighing and mixing materials.

With our surface coat having again reached the almost tack-free state, we are ready to apply the layers of fiberglass cloth and laminating resin.

We are using two brushes. The cut brush will be used to apply the cloth.

And here you see the long brush being used to apply the liquid material. This material is a little thinner than the surface coat and again, we are flowing this on to obtain a uniform wetting of the tool surface.

Finally, we set the first layer of fiberglass cloth over the resin and we use the cut brush to bring the resin through the cloth. We are applying just enough pressure to get it through, but not too much to disturb the surface cost underneath.


Applying Additional layers of Fiberglass Cloth and Laminating Resin

We can apply additional layers of cloth and resin as quickly as we can, noting the gel time of the resin. When we brush out each layer, we are careful not to stretch out the cloth, which could warp our tool.

We can apply up to 12 layers or about 1/4 inch of material onto our part in one session. After 12 layers, we must allow the heat to dissipate before applying another session of up to 12 layers. Otherwise, the excessive heat from the laminating resin may warp our tool.

For additional sessions, we would need to prepare the surface for the first laminating adhesion layer. One way is to wash off the tool as it will feel a little greasy and then sand it a little. Another way is to take cotton flock and sprinkle it over the last layer before we go, then the next morning we would blow off the excess and then start applying the resin.


Demolding

To demold our tool, we are simply wedging a putty knife under the tool and gently lift. Notice the PVA film that we had applied to the board before the surface cost. Most of this film can be peeled off with your fingers and since the PVA is water soluable, you can wash off the rest to finish your tool.