Epoxy Laminating Systems

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.

Building an Epoxy Laminate Tool

Now that we understand some of the basics of laminating, we will use those techniques to construct a mold or “tool” that may be reused to create multiple finished parts. Unlike making the actual finished part, where precision and the overall weight and appearance are critical, with a tool, the primary goal is to achieve an excellent surface finish, good dimensional accuracy, and overall strength and durability to support the number of parts required.

First, we applied and sanded several coats of Sandable Grey Primer until we achieved the desired surface finish. We also constructed a support frame made of pine. This frame gives us a ending point for our tool, unlike an actual part where we would want to extend the laminate beyond the desired dimensions and then trim it later. The frame is as large as possible in order to maximize the flange, or flat part, around the model, which will be useful later when forming the part.

We drew a line around the inside of the frame, to provide an ending point for our resins. We don’t want the laminate to protrude above the support frame as this would require unnecessary trimming to create a flat back surface.

Now it is time to cut and fit our pieces of fiberglass. To make the laminating process proceed quickly, we want to pre-fit all of the pieces of our fiberglass before mixing the resin.

First, we connected the mold frame temporarily.

We are going to use a combination of 6 inch, 4 inch, 3 inch, and 2 inch fiberglass tape. All of these tapes are a 10 ounce fiberglass with a plain weave.

Fiberglass tapes are excellent for smaller jobs because they reduce the amount of cutting required, and have bound edges to prevent the fabric from unraveling. For larger molds, obviously, the large rolls of cloth are ideal.

We begin to fit each strip of fiberglass in our mold and mark where we want to cut it. Then, using a straight edge and a utility knife, we cut each piece as shown. Scissors also work well for cutting fiberglass. It is a matter of personal preference.

Note that we are fitting our layers of fiberglass prior to applying our release agents. This is done to prevent us from disturbing our carefully applied release agents, and thus requiring possible re-application.

Our goal, especially for the first layer, is uniform coverage with no overlapping joints. Although a tool doesn’t need to be as precise as a final part, the more carefully we fit our fiberglass, the easier it will be to build the mold.

For our ends= of our model, we use paper to trace the outline of the desired shape. Then we cut the shape with scissors, retrace and cut this shape to create a cardboard template. This template can now be used to guide our utility knife when cutting the fiberglass tape.

Next we arrange some strips around the perimeter of our model in order to secure our tool to the mold frame.

We use partial cuts in the fiberglass pieces it order to fit them around corners and other difficult contours.

Finally, we cut small pieces to apply around the corners of the model to reinforce those areas.

Now we’re ready for cutting the second layer, which we build up at a 90 degree angle from our first layer. Orientation of the cloth isn’t as important for a mold as it is for a part, but it is usually good practice to at least alternate the direction of the fiberglass with each layer.

We’re also using wider tape at the perimeter to overlap the underlying layers.

It is not required to have the first layer underneath in order to fit the second layer, but we’re doing it this way in order to help you better visualize the construction of this tool.

We’ll cut the pieces for our third and fourth layers identically to our first and second. Then, we’ll remove all of the fiberglass and clean off the mold.

Now we’re ready to apply our mold release.

We applied two coats of Freeman Wax Release, buffing the wax after each coat. Next we pour our PVA mold release into a small cup and apply two coats of PVA mold release over our model, allowing sufficient time for each coat to dry completely.

Fifteen minutes later, with our mold releases completely dry and our mold frame reattached, we’re ready to apply our Freeman 705 epoxy surface coat with a cut brush. We start with tool face first, and then cover the rest of the model. We’re also applying the surface coat to the mold frame, up to about the line we had drawn earlier. Here is what the first application of the surface coat looks like when it is finished.

Now we wait for the material to reach the almost-tack-free state, before applying the second coat. For more information on identifying the almost-tack-free state, please see our other video on epoxy laminating basics.

With our second coat reaching the almost tack-free state, we’re now ready to build our laminates.

Before we begin applying our fiberglass tape, we want to add a putty-like mix around the corners of our mold frame. We do this by mixing our Mia 66 Milled Glass Fiber into our Freeman 605 laminating resin, and then applying this thickened mixture to the corners as shown. This creates a fillet in the corner and establishes a smoother contour for our fiberglass tape and prevent air voids between our laminate and surface coat.

Now we’re ready for the first layer of laminating resin, which we apply over the two layers of surface coat with a normal brush.

Then we lay down the first layer of the fiberglass tape that we had pre-fitted earlier. Using a cut brush, we work the resin up through the fiberglass until it is completely wetted out with the resin.

We have to be careful not to be too aggressive with our brush because the surface coat layers underneath are not completely cured, and therefore can still be disturbed if too much force is applied.

Even though we mix smaller batches of laminating resin to extend the working time as much as we can, now is when we really appreciate the careful planning and cutting of all of the fiberglass earlier.

Once the first layer is complete, we immediately begin laying our second layer. And then our third layer.

For this mold, we stopped the laminating process at three layers to show an easy technique to bond subsequent layers of fiberglass over a cured epoxy laminate.

Here we are sprinkling our Mia 66 Milled Glass Fiber over our laminating resin, which is still wet, making sure to completely cover our entire tool. This process covers our mold with thousands of pieces of very fine fiberglass filaments that will create a mechanical bond to the next layer of laminate. Without this mechanical bond, the probability of a de-lamination between subsequent layers is very high.

The next day, after the first three layers of laminate have completely solidified, we brush out the excess milled glass fiber. Then we apply another layer of laminating resin and then fiberglass tape. Because the underlying layers are hard, we don’t have to worry about disturbing the integrity of the layers underneath.

The next day, our fourth and final layer of fiberglass and resin has cured. Now it is time to install the support bar. We do this because of the large expanse length-wise where the tool is only connected to the mold frame on the perimeter. By adding support bars across our frame, we add significant strength, rigidity and stability to the tool without adding much weight or cost.

Since we want the backside of our mold to remain flat, we want to install the support bars just below the surface. Also we want to make sure that the support bars are not touching the laminates to prevent possible “print thru” of these over time.

To bond the support bars, we could use a filler material such as Tuf-Fil, but since the gaps are narrow, we’ve chosen to use Freeman Wood Glue.

Notice how we have cut notches on the ends of our support bars to accommodate the fiberglass on the mold frame. After allowing the glue to cure for about 15 minutes, we apply small wire brads to further strengthen the bond.

Next, we secure the support bars to our mold frame and our mold with more fiberglass tape and laminating resin. We apply short pieces on the ends, and longer strips along the length of the support bars to attach to the underside of the mold.

We are also taking this opportunity to show an alternative method for wetting out our fiberglass tape. We lay out our strip over a plastic-covered surface. Then, using the cut brush, we wet-out the fiberglass, flip it over and then apply it to our tool. Although not ideal for the first layer, since you need sufficient resin underneath to be drawn up through the fiberglass, this process does speed up the application of additional layers, as we’re doing here for our second and third layer of fiberglass.

Here is our completed mold, with the bracing completed.

The next day, we remove the mold frame, and then use our wedges to slowly remove the mold from our model. Because of the careful application of mold releases, demolding is not difficult.

Here we can clearly see the green color of the PVA mold release, which we remove with several damp cloths and then allow to dry.

The mold is now ready for use in creating fiberglass parts, Kevlar parts, or carbon fiber parts, as we will demonstrate in the next video.

Vacuum Bagging a Composite Part

One of the most common methods of constructing a finished composite part is vacuum-bagging. We will demonstrate this process by forming a carbon fiber part against this epoxy laminate tool that we created in our earlier video. Although we’ve chosen to use the carbon fiber because of its superior strength to weight ratio, this same method is also compatible with fiberglass.

We begin by applying our Mia PS tape around the perimeter of our mold in order to cover the gap between the mold and the frame. This pressure-sensitive tape will ensure an airtight seal during the vacuum bagging process. Next we apply our release agents. For this mold, we’ve chosen a semi-permanent release. For more details on this procedure, please watch our video on Sealing & Releasing Models and Molds

Next we apply our Mia Sealant tape. We start applying the tape in the middle of one of the sides, rather than a corner. This way, it will be easier to seal the two ends of the tape together when we are finished. Here is a close-up of how we are rounding the corners. Rather than overlapping tape at the corner, which could create a potential vacuum leak problem, we tear just the tape at the corner and carefully create a nice, round corner with no cuts or overlapping tape. This method exposes a small bit of the adhesive at the corners, which we cover with small strips of the tape’s non-stick backing.

Now we’re ready to cut our materials. [graphic]

First is the carbon fiber. Although there are many types of carbon fiber, we have chosen a twill weave, which provides an impressive looking appearance to the finished part. Since each strand has a smooth, slippery surface, carbon fiber will move and shift during cutting, making it more difficult to handle than fiberglass cloth. We measure the desired dimensions of our carbon, and then pull out one strand, leaving a line for our scissors to follow when cutting. This technique will work when cutting both the length and width.

Next we roll out and cut our Mia peel-ply. This layer, although not necessary, is very useful when desiring either a satin finish for the finished part, or if we plan to do secondary bonding. The nylon will create a rough and very active surface on our part.

The next layer is our perforated film, which regulates the flow of excess resin from the part into our bleeder material. The small perforations enable excess resin to be drawn from the reinforcement evenly throughout the part, rather than allowing it to pool in specific areas. This helps us to achieve the ideal ratio of resin to reinforcement throughout the part.

Next we cut our bleeder material. This material absorbs and retains the excess resin that is drawn from the part and through the perforated layer. We selected at least two layers to ensure it captures all of the excess resin without completely saturating the material.

Now we cut our release film, which prevents resin from crossing into the breather material.

Next we cut our breather layers which is the same material as our bleeder. This layer enables the vacuum to uniformly pass through this fabric and exert consistent and even pressure over the entire laminate.

Our final layer is the bagging material, which we cut oversized to allow this material to be sucked down into the cavity created by the contour of our mold.

When using the vacuum bagging technique, it is always advised to insert a resin trap between the vacuum pump and the tool. This trap protects the pump by preventing excess resin not captured by the bleeder material from flowing through the vacuum line and into the pump itself. This resin trap can be in the form of a beaver tail, which we’ll show at the end of this video, or a vacuum chamber, as we’ll show here.

First, we test the integrity of the chamber and its connections to ensure maximum vacuum pressure is reaching our tool. We do this by plugging the end of our hose and then turning on the vacuum pump and watching for loss of pressure.

Here we are testing our vacuum reservoir by plugging the end of the hose and then turning on the vacuum pump.

To improve the integrity of the connection and prevent even the slightest leak, we apply some of our sealant tape around the connection. Our vacuum reservoir easily reaches negative 25 inches of mercury, which is sufficient vacuum pressure for our part.

For our base resin, we’re going to use Miapoxy 100 with our Mia 95 hardener. The Mia pumps dispense the correct ratio of materials without having to measure. We chose the slower hardener because it provides us with the working time we need to complete our vacuum bag before it begins to cure.

Next we measure our Miapoxy 100 epoxy resin and our Mia 95 hardener using the Mia pumps to provide the correct ratio of materials.

We don’t want to dispense any more material than we’ll need at any one time because mixing larger quantities of resin and hardener results in loss of working time. For more information on measuring and mixing, please see our other video on this topic.

After applying an initial coat of resin to our mold, we proceed to wet-out our carbon fiber. We do so by pouring our resin over plastic, then brushing it out, and then laying out our first layer of carbon fiber over the resin. Then we use our brush to apply additional resin over the fabric, thus completely wetting out the carbon fiber.

We are careful not to apply too much resin to the edges of our carbon. To prevent the unraveling of the fabric, it is best to wet the edges in the tool cavity.

Here we are applying the carbon fiber to the part. Notice that the fabric is larger than desired, so we trim the material on the mold itself, making sure it does not extend too far onto the flange area.

Although we are using vacuum pressure to draw the part down to the mold, we still want to be careful to lay down our fiber evenly over the contour to prevent wrinkles and warping of the part during the vacuum process.

Notice when the fiber is impregnated with resin, it becomes almost airtight over the mold, and therefore can create bubbles or air pockets that need to be eliminated before moving on to the next layer.

Here we are applying the second layer of carbon.

Next we apply our final layer of laminating resin directly over our second layer, and then apply the last layer of carbon fiber dry. Then we use our brush to bring the resin through and apply additional resin only where necessary.

With the carbon fiber and resin application completed, we’re now ready for the vacuum bagging process. First, we apply our peel ply directly onto the top layer of carbon fiber. Notice how the peel ply seems to almost disappear as it comes into contact with the resin.

The peel ply should be treated like a layer of cloth, meaning that we don’t want any air entrapment between this layer and the laminate. Any white areas show where air entrapment has occurred. We use our brush to carefully eliminate these areas.

Next we apply the perforated layer laying it out it as flat as possible. Although this material will stretch a little under the vacuum pressure, it is best to minimize the stress. Since both our peel ply and perforated layers are slightly over-sized, we use scissors to remove the excess. It is better to initially cut these layers over-sized and then trim them, rather than cut them too small.

Next is our two layers of bleeder material. This provides us enough material to absorb nearly all of the excess resin which will be drawn from the part through the peel ply and perforated materials.

Using our Mia PS tape, we secure the bleeder to one edge. And we fold over the other edge while we lay down our Mia release film. If necessary, we can cut notches in the release film to ensure a good fit.

Now we are cutting off the extra bleeder material and then taping the other side of the bleeder and then the release film.

We then apply the breather material. This material is identical to the bleeder used before and is isolated from the resin by the release film. The vacuum pressure will be dispersed evenly over the entire part because the resin is not able to permeate into this layer.

Unlike earlier layers, it does not have to be secured in place.

Next, we apply a small piece of breather to the end of our hose and secure it with tape. This regulates the flow of the vacuum and prevents the bag from blocking the vacuum hose.

Now we’re ready to apply the bagging material. The following technique is essential to make sure the bagging material is able to contact all the surfaces of the laminate as uniformly as possible. Otherwise, the part may contain air voids, resin rich areas, or possibly delaminate.

First, we connect the corners of the bag to the corners of the sealant tape.

Next, we begin to make a series of “pleats” in our bag. These pleats permit the bag to fit tightly into all corners of the laminate.

We need to create a pleat on every corner and one for every inside radius. Therefore, for the longer sides, we only need one pleat in the middle, where on the shorter sides, we need three pleats.

We measure the height of each pleat and tear off a piece of sealant tape for each one.

To attach the tape to the pleats, we fold one end over, bond it to the sealant tape on the surface, then attach it to the interior of one side of the pleat. Then we peel off the backing, pull the pleat to one side, and carefully attach the sealant tape to the other side.

Here we’ll show the process one more time. These are sometimes called rabbit ears because of the shape of the finished pleat. The goal is a completely sealed pleat that gives the bag extra material to touch all areas of the laminate without “bridging” or creating voids between the bag and the part.

Finally, we attach the vacuum hose to our tool using the same technique. Again, we’re careful to completely seal the opening to ensure vacuum integrity.

Now we turn the vacuum pump on for just a few seconds and let the bag work its way toward our tool, but not all of the way. Then we arrange the bag to make sure the pleats are properly placed to ensure thateven pressure will be applied to the part.

Then we turn the vacuum pump back on and check for any leaks. This vacuum will remain on until the resin has cured.

Notice the dots of resin in the bleeder layer, having come through the tiny holes in the perforated layer below it.

As the vacuum is applied, we can easily see that we have achieved uniform compaction of the part, resin is flowing through the peel ply, through the perforated release film, and is being absorbed by our two layers of bleeder fabric. We now maintain vacuum pressure overnight until the resin has solidified.

The next day, we cut our vacuum hose, then begin peeling off the sealant tape, revealing our breather layer.

Then we peel off the other layers, to reveal our part.

Because of the careful application of our semi-permanent sealer and release, our part demolds very easily.

Next, we remove the peel ply, which has adhered itself to the part. We are careful of the edges of the part, which are very sharp. Again, since we used the peel ply, that side of our part has a matte finish and is ready for secondary bonding.

If we desired a part with a shiny and smooth back surface, we would have eliminated the use of the peel ply layer and we would have started with the perforated release film.

The first finished part is always the most difficult to create. After the first one, you can make adjustment, such as how much resin to use and how many layers of bleeder material is necessary.

After trimming our demolded part and sanding the edges of the carbon fiber, we now seal the edges with Freeman 505 5-minute epoxy. The epoxy is mixed and then applied with a gloved finger-tip as shown. This simple application protects the edges and prevents possible splintering or moisture contamination. Our part is now finished and ready for service.

Now, as an alternative, we going to show a method that replaces the vacuum reservoir as a “resin trap” with long strip of breather material, known as a beaver tail. Instead of the resin flowing into the reservoir, it would flow into the beaver tail, preventing it from reaching the pump.

To create this, we take long pieces of breather material, fold them together, and place them in bagging material, as shown. We also insert the base plate of our vac valve and place it at the end of the beaver tail. The other end is attached to one side of our tool with sealant tape.

Note how we attach the breather from the beaver tail to the breather material on the tool itself to ensure vacuum passes from the beaver tail to the breather layer. Next. we cut a small hole in the bag and then attach the top of the vacuum valve.

As before, we start the vacuum pump, stop it in order to arrange the bag to make sure the pleats allow for even distribution of pressure. Then we restart the vacuum pump.

We have now achieved the function of the resin trap, without a vacuum chamber.

Paste Laminating Systems

Paste Laminating is a tooling process designed to lessen the considerable time it takes to lay up medium-sized tool without sacrificing strength or stability.

Those who have followed the epoxy laminating system to lay up a dozen or more layers of fiberglass cloth have experienced the biggest drawback of that system, which is time. In this process, you apply a 1/2 inch thick layer of paste laminate material, such as our Freeman 1020, between layers of fiberglass cloth, creating a very strong, yet lightweight tool in much less time.

This project is going to be a three-part mold with curved parting lines. To form the parting lines, we’re using Freeman’s 3/8 inch high temperature sheet wax. We’ve chosen the 266 series high temperature wax instead of our 165 series lower temperature wax because it is much easier to bend and flex by hand. We are adhering the wax strips with Plast-Econ modeling clay.

After sealing the sheet wax with Freeman Wood & Plaster Sealer, we are applying PVA and wax release to the entire part. For proper sealing and releasing procedures, please see our other video on this topic.

The first step of the paste laminating system involves applying two layers of surface coat such as our Freeman 705, with a cut brush. As always, we wait for the material to reach the almost tack-free state before applying additional layers.

The next step is applying three layers of laminating resin and fiberglass cloth, much as you would in a typical epoxy layup. Since we devote an entire video to epoxy laminating systems, we won’t repeat those instructions here.

After three layers, you are now ready for the paste laminate material. We are opening our packages of Freeman 1020 on a plastic covered table. Since each gallon kit will cover about 420 square inches, we know this project will require more than one gallon kit. So we begin by mixing the entire bags together without having to weigh the material. When we require less than one full kit of material, we will weigh the material using 100 parts resin to 33 parts hardener.

This material is easy to mix by hand. The goal is to mix until the material until it reaches a uniform color.

If you mix the paste laminate material too much, it will become very sticky, which will make it more difficult to apply.

Next, using a rolling pin, we roll our material on a plastic-covered piece of wood, which has been specifically built with a half inch clearance in the middle.

With our material now rolled out to a uniform 1/2 inch patty, we cut the material into strips for easier handling and apply the paste to the back of our tool.

Since most projects aren’t exactly rectangular, you may have to cut the material into smaller pieces to fit into small corners and gaps.

Here is our finished application of the paste laminate. We are now ready for our final three layers of fiberglass cloth, beginning with our laminating resin. You do not have to wait until the paste laminate hardens before applying the final layers of fiberglass cloth.

Notice how we are starting at one end of the part and working our way to the other end. This not only allows us to keep track of where we’ve applied our material, but it also helps us recognize which side should reach the almost tack-free state first.

Our first part is now complete and ready to cure overnight. If we had been following the epoxy laminating system, we would still be laying up our maximum of 12 layers of fiberglass cloth per day and then have to finish up the part tomorrow to add the additional layers required to build a strong tool.

Day Two: After 16 to 18 hours, we are ready to create the second part of our mold.

We begin by removing the sheet wax that formed our parting line. Then, using a razor knife, we clean up the edges of our fiberglass layup.

To clean up the clay that was used to attach the sheet wax, we use a fillet shaper tool to scrape the clay and a rag wipe off the remainder.

Next, we attach new pieces of sheet wax to complete the second parting line. Again, we’re using Plast-Econ modeling clay to adhere the wax and our fillet shaper tool to clean off the excess.

After applying the Wood and Plaster Sealer to the sheet wax, we cover the ends of the first part of our mold with masking tape. This is done to prevent the any of the new material from accidentally seeping into the edges of the first part and therefore locking the two parts together.

Finally, we apply our two coats of Wax Release, two coats of PVA and our last layer of wax release. Our wax release will also dissolve some of the excess clay that we hadn’t removed earlier.

The remainder of our paste laminating is exactly as we did the day before, applying two layers of surface coat, three layers of Fiberglass cloth, our 1/2” thick layer of paste laminate, and finally our last three layers of fiberglass cloth.

On the third day, we created our third part just as we did parts one and two and here on the fourth day, our tool is complete and we’re ready to demold. Notice the makeshift stands that we’ve attached to the outside using our Tuf-Fil. This is so we can later turn the tool upside down.

Before we demold, we are drilling holes through the lips of our mold to ensure perfect alignment of our three parts later. We are inserting brass dowels into the holes.

Here we are placing wedges at the parting lines and tapping them with a hammer. Because we followed the proper sealing and releasing procedures, we are able to demold each part cleanly.

Notice the green PVA mold release on our tool, which can be easily peeled off and washed off with a damp rag.

Since we drilled the alignment pins before demolding, we are ensured perfect alighment when reassembling our tool.

Here you see a sideview of the paste laminate. Again, had we created this tool using the epoxy laminating system, it would have taken many more hours, plus an extra three days to create a mold this rigid and strong.

For even less working time, you may forgo the fiberglass layup steps, especially for smaller or less demanding projects. Freeman also offers Freeman 1030, a new lightweight urethane paste material that can be applied with a paddle rather than being rolled out.

The Repro Laminating System

Repro Surface Coat and Laminating Resins are a popular choice among our customers who are making a medium-sized tool and don’t need the strength of an epoxy.

To demonstrate working with a Repro surface coat and laminating resin system, we will create a tool based on this part. The frame is made of pine wood and the entire part has been treated with one coat of Freeman Wax Release and one coat of PVA mold release. For proper application procedure, please refer to our other video on this subject.

Our Repro Surface Coat and Laminating Resin system has several advantage over using an epoxy, such as the easy 1 to 1 mix ratio, the lower cost, and the shorter gel times allow an entire tool to be created in 75 minutes, as opposed to overnight. Also, by using fiberglass strand instead of cloth, it is easier to fit the tool around intricate parts.

Applying Repro Surface Coat

The Repro Surface Coat starts out thinner than an epoxy, so we want to start out by covering the areas of our part with the highest detail and the corners.

If the viscosity was too thin, such as for applying material on vertical walls, we would wait a bit and it will thicken up.

We will be applying two layers of surface coat, so we’re not as worried about getting everything the first time around.

We’re not worried about excessive build-up (as in epoxy) because Repro doesn’t produce a lot of heat.

After three minutes, notice how the liquid is already thickening up, making it easier to apply to vertical surfaces.

The gel time is determined by what point the material is so thick that it will no longer self-level.

The almost tack-free state will occur in about 15-20 minutes, and then we are ready for the second coat.

Again, we started on the areas requiring the highest detail. We can also apply this layer more liberally.

Apply Laminating Resin and Fiberglass Strand

With our surface coat again at an almost tack-free state, we’re mixing up a small amount of our laminating resin. Then we apply one coat directly on top of the surface coat to act as an adhesion layer.

Next, we’re ready to mix the laminating resin with the fiberglass strand. First, we mix the two sides of the laminating resin like any other 1:1 ratio liquid tooling material. Then we pour the mixture into a larger cup and begin adding the chopped fiber.

We can make this as wet or dry as we like. The drier you make it, the lower the resin content, which will lessen both the heat and the shrinkage. However, we’ll want make sure these enough resin so it is still sticky.

Here we have our finished “dough-like” material. The top of our tool is still wet from our adhesion layer as we begin to apply it everywhere. We work it into the smaller areas with a paint paddle.

There will be more material used here than with an epoxy layup, so we can expect a little more shrink, but it is will more controllable and uses a lot less material than a mass cast – which is why mass cast parts are usually used only for smaller parts.

As we progress, it may be difficult to see exactly how thick our tool is. We want 1/4 to 3/16 of an inch. Notice how much easier it is to apply this thick of material than it is if we were using numerous layers of fiberglass cloth – this is one of the primary advantages of Repro Surface Coat and Laminating Resin.

As our mixture starts to dry, it is even easier to work with. We can even form it with our hand.

Demolding

Here we are unscrewing the backside of our mold. Then, after turning the mold back over, we gently tap four wedges to begin separating our tool. It is important to lift the tool evenly. If you lift from an angle, we may create a negative draft, which we don’t want.

Once the tool is removed, we have to remove the PVA mold release by dampening a cloth and wiping off the entire surface of our tool.

Glove Molding Systems

Glove molding is a process where we form a thin layer of flexible material over our model, and then back it up with a stronger, rigid material. The flexible layer enables easy demolding of cast parts while the rigid material increases the mold’s strength, durability, and accuracy. This process uses less material than mass casting resulting in a lighter mold, and can be applied to vertical surfaces.

In this video, we’re going to demonstrate the classic application of the process, and then demonstrate an alternative process for highly detailed parts.

With our model attached to the mold board, we begin by applying our Freeman wax release, and then applying our PVA mold release. Please refer to our separate video on proper model preparation procedures.

Next we screw the wooden frame onto our mold board.

Once everything is in place, it is time to mix our Freeman 1035T urethane rubber material. This material has a 1 to 1 mix ratio by volume, and 80 to 100 mix ratio by weight, so we are scooping 200 grams of part B, zeroing out the scale, and then pouring 160 grams of part A on top of the part B. To avoid an unnecessary mess, we usually recommend adding the thicker material first, which in this case is part B, and then adding the thinner material on top.

Here you see us mixing the two parts together. For proper preparation of liquid tooling materials, please see our other video on this topic.

We begin applying the 1035T onto our part with a small brush that has been cut to create a pointed end. We are making this layer as thin as possible to minimize air entrapment.

One of the advantages of using this material is that it can be applied on a vertical wall. Notice how the material doesn’t move at all.

Here’s what the completed first application looks like.

After 45 minutes, we test the material to determine if it has reached the almost tack-free stage. For more information on the almost tack-free stage, please see our video on the epoxy laminating system.

We are now ready to apply our second coat. This layer will not be as thin as the first, but we aren’t yet concerned with building up thickness. While our detail is mostly established, we are still careful not to entrap air.

Here you see the application of third layer. Now, with each successive layer, we are applying the material thicker because the surface of our tool is gradually evening out, allowing us to be less concerned with air entrapment and more focused on speed and material thickness.

Finally, our fourth and final coat is applied. This last layer is our thickest, yet it is the easiest and quickest to apply.

Here is our completed application of our glove layer using Freeman 1035T.

Day Two

The following day, we are using our Freeman fillet shaper tool to separate the glove layer from the frame. Next, we remove the screws on the bottom of the mold board and then remove the frame so we can easily cut the edges of the glove layer with a knife.

This step is really useful because it prevents our next layer of rigid material from pinching the glove layer between it and the mold frame.

Next, we scrape and then lightly sand the mold frame to remove any excess material.

Then we apply a layer of wax release to the glove layer. Here, no buffing is required because we aren’t as concerned with what the surface of the backup layer looks like. We are just concerned with getting 100% coverage of wax to allow for easy release between the glove layer and the backup layer.

As we reassemble the mold frame, notice the tight fit, demonstrating the low shrinkage of this material.

For our backing material, we’ve chosen Freeman 1030, a lightweight urethane paste material that has a 1 to 3 mix ratio by volume, and 41 to 100 mix ratio by weight. When we open the B side, we notice a little separation has occurred, so we lightly stir it until it reaches a uniform consistency and then measure 300 grams.

After shaking the A side a little, we add 123 grams and mix the two parts together. Again, we added the b side first because it is thicker.

We are now ready to apply our backing material. Freeman 1030 has a consistency a lot like peanut butter making it very easy to apply. Since it has only 9 minutes of working time, it is recommended that you mix smaller cups of material and apply them one at a time as shown in this demonstration.

Notice the color change as the material begins to cure. The thicker areas will set up quicker than the thinner areas.

Here we are applying our second cup of material on top of the first. This new material will bond with the material from the first cup without sacrificing strength.

The corners and the vertical walls are the most difficult areas on which to apply to get a nice thick layer of material.

Here is what the finished application of our backup layer looks like.

Day Three

The following day, we are removing the screws from the mold board, and then placing wedges between the mold board and the mold frame.

Notice how the backing layer is still attached to the frame while our glove layer remains over our model.

It is a good idea to mark one side of the glove mold and the matching side of the frame. This allows for quick and easy alignment of the two pieces later.

Next we peel the glove layer off of our model.

This also illustrates why we don’t need any additional registration to properly align the two pieces. The irregularity of our parting line will provide a natural locking mechanism.

Finally, we wash off the PVA with water or a damp rag and the mold is now ready for pouring plaster or urethane to create many accurate, easily demoldable parts.

Alternative

Following the exact steps of the glove molding process will work for many medium-sized projects. Here is an example of a glove mold using Rhodia’s VRM-65, a brushable silicone rubber, and Repro Laminaing Resin mixed with fiberglass strand as the backup material. Silicone, while being more expensive, is often preferred by those who require a very easy part release because silicone doesn’t require any release agents.

However, the typical glove molding process might not work as well for very intricately detailed models, such as our previous model, which demonstrates the shortcomings of this process. Since a thick material is being applied to such an irregular surface, air entrapment is almost unavoidable, resulting in minor defects as shown here.

To demonstrate a solution to this problem, we’ve gone back and added an additional step, one that is only necessary for highly detailed models.

Before applying our thixotropic layer, this time we will add two thin layers of our regular Freeman 1035, a much thinner material primarily used for mass casting flexible parts and molds.

This material mixes at a one to one ratio by weight or volume. For this example, we’re mixing 75 grams of each side into a cup, and then applying a thin coat to our model.

Notice how the material puddles just a little bit in the deeper areas, which is usually where the air entrapment occurs. Using an airhose to push air over a layer may also help prevent bubbles from forming underneath.

The material will thicken gradually over the gel time. After about 20 minutes is the ideal time to apply the urethane to noncritical areas and vertical walls

Here is what the completed first application of Freeman 1035 looks like.

Once the almost tack-free state is reached, the second layer proceeds exactly like the first.

We now have a very thin layer of material over our model, creating a smoother working surface and lessening the possibility of air entrapment as we proceed to the Freeman 1035T to complete the glove layer.

From this point, everything proceeds exactly as in our earlier demonstration, with several layers of Freeman 1035T to complete the glove layer, an overnight cure, and then the application of Freeman 1030 to produce our backing layer.

On the third day, we are ready to view the results of our extra effort.

Again, we mark the tool and frame, and then we reveal our tool.

You can see the differences in color between the 1035 and 1035T. Notice how the 1035 is predominant in the areas where air entrapment occurred in our earlier mold. Our new mold virtually defect free, making the added working time worthwhile.