Thread: Shaping foam rubber

Hey there,

The Trimmers at my work have a $500.00 cutter for foam, I have a $30.00 electric carving Knife that does just as good a cut, for cutting sheet stock no probs, cutting recesses for roundish objects I cut 2 or 3 thin slices and sort of step the edges. I have been told that you can use a hot knife to cut recesses but you need a steady hand.

HazzaB

Originally Posted by HazzaB

...I have a $30.00 electric carving Knife that does just as good a cut..

Sounds interesting. Any details on where to get one?

I bought a $5 2nd hand electric bread knife from the Salvo's store near me. Cuts foam fine.

Suggestion:

Stack the foam around the piece, until you have a reasonably rectangular outline. Build the box around the foam.

Joe

I've cut foam rubber on the bandsaw very neatly.

To get a really close fit, coat the inside of the box with some non stick stuff, wax etc and do the same for the piece. Place piece in box, squirt in some of that gap filler foam around pice, trim to size when dry.

Thats how to do guitar cases too.

I haven't tried it but I have heard that a good way to cut shapes in foam is to squeeze it between 2 pieces of thin ply and then cut using a scroll saw.

Peter

Originally Posted by AlexS

I bought a $5 2nd hand electric bread knife from the Salvo's store near me. Cuts foam fine.

Thanks Alex, I thought we were talking about a special carving tool

Cutting is fine with the breadknife, the problem is carving out the foam to fit the contents. I'll try Joe's suggestion of stacking and shaping - sounds like the go. Thanks for all the suggestions.

Alex, had one chap that used a router on that hard white foam to make a shape for a pen, than covered it with material. Amos

I made a case for a base guitar - used foam cut out to fit the guitar and lined it with purple velvet - looked pretty swish. I used a pair of nail scissors to cut out the bits where the guitar goes - drew the shape on with a pencil, and started cutting. If you take little scallop-shaped bits you can control the shape completely - just keep trying to fit the object in as you get near to what you think is the right depth. Slow and steady.

Cheers,
Adam

I use a dremil with a sanding tube to cut out shapes like pens for pen boxes. This way you can vary the depth. Also have used an abrasive cutter to cut straight lines.

Originally Posted by Bodgy

To get a really close fit, coat the inside of the box with some non stick stuff, wax etc and do the same for the piece. Place piece in box, squirt in some of that gap filler foam around pice, trim to size when dry.

Thats how to do guitar cases too.

I finished up giving this method a go because of the complexity of the shapes (a three-branch candlestick. I turned up a pattern the shape of the base of the candlestick, cut it in half & stuck it to a base. Made up some displacers to go where the arms would sit and stuck them in position. Also made up a ply box with no top or bottom, fractionally smaller than the one the insert goes into & waxed the inside, and sat it on the base holding the patterns, held in place with clamps. Laid the lining cloth over the pattern, then put in some gap filling foam, and placed a piece of ply the same size as the inside of the box on top of the foam with stop blocks at the height I wanted the foam to rise to.

Pics tomorrow.

OK, here are some photos. Sorry they're out of order.
The box is 470 x 300 x 175, in blackwood, with tiger myrtle lid panel.

Photos 1 & 9: First, mark out the profile on two sides of a blank and and cut out the shape.
Photo 2: Turn the pattern. This is the pattern compared to the candlestick base.
Photo 3: Pattern for the candlestick base and arms on base of box.
Photo 4: Pattern in position in moulding box.
Photo 5: Foam inserted and sealed up.
Photo 6: After the foam has set.
Photo 10: Insert removed from casting box
Photo 7: Exterior of completed box
Photo 8: Interior of box showing candlestick.