Making a Mold

For today’s lab we were making a foam mold to form a composite from Canvas and Epoxy. The mold was designed in Fusion 360 and you can download the stl file here.

fusionSketch

This was uploaded onto the software for the shopbot CNC milling machine and 3 tool paths were made: one roughing (make the general shape of the object first), then two smoothing (90 degrees from eachother to make the shape more accurate).

toolpath

The foam block we were planning to shape was placed in the CNC mill and its corners were hot glued to a throw away surface thet was attached to the machine.

The next step was setting the origin, the shopbot is a 3 axis machine (x,y,z). We set the origin in the bottom left corner of the foam block. Once the cut finished it looked like this:

finishedCut

Layering

canvas layers

Layers:

  1. Release (Vacuum Bag)
  2. Breather (Sheeted Stuffing)
  3. Bleeder (Seran Wrap)
  4. Fiber(Canvas) + Epoxy
  5. Release (seran Wrap)
  6. Foam Mold

Now it was time to layer our composite material. We cut rounded sheets of canvas with darts in it to fit over out heart shape. To mix our eopxy we use two parts A (ONE Epoxy) and one part B (ONS Hardener). The first layer over the mold was seran wrap. Then we spread the epoxy on the layers of canvas we cut and put them over the first seran wrap layer. We added another layer of seran wrap over all of this that war perforated using a spiked roller. Then a layer of cotton was put over all of this.

pokeThing stuffing

Once all the layers were on it was time to vaccum seal it using a food preserver.

sealMachine vaccSealed

After 24 hours the mold was ready to be removed from the bag.

removedMold

The seran wrap was peeled off as best as possible. The canvas hadn’t lined up with the mold quite right so it came out looking like this :

seranMold backSeranWrap

Then the excess canvas was cut off using shears for this final result:

cleanedMold

More information about composite molds here