Cutting expanded polystyrene

Don't know the details that youwant, but be very careful with the toxic fumes that are given off.

I guess you just want to eg split the blocks in two, to within a mm or so? If so, a hot wire cutter is good.

First, you need a method of tensioning the wire when it gets hot and sags - a spring is good.

Also, some method of mounting the wire, perhaps vertically, so that you have a fence to move the blocks along, as in the fence in a tablesaw or the like.

For the wire, people use lots of things. The pros sometimes use inconel or nichrome, but stainless is generally okay. 7-strand fishing leader is more flexible, but solid wire will do fine.

For the power supply, well you need around 15 to 50 watts per meter of hot wire. You don't want to get it so hot that it produces fumes, or gets red hot.

Exact voltages and currents depend on the wire used. If you have some wire I can calculate these for you if you let me know the wire diameter and material, and the length.

For starters, think 12V and 2 amps, but this will depend on the wire!

Otherwise, you can probably find a calculator out there somewhere on the wild wild web.

-- Peter Fairbrother

Many thanks, just what I was after finding out, as oppossed to the health and safety warning/advice I didnt want ( Yet another sign of ageing, we KNOW various stuff should/shouldnt be used, gives fumes etc, and get fed up being told all about H&S by a group of dipsticks who dont know anything about the real "World" )

I was thinking of using some sort of fuse wire, the stuff that came on the cardboard dispensers, for emergency repair when the house fuse blew. (please dont anyone tell me you need a newer type of fuseboard, I have one ) I was thinking a length of say 6" of 5amp would be a starting point. Bob

If you want a few feet of Inconel suitable for making the device you need the let me know, you can have it for a donation of your choice to Remap

Thank you. I'll sort a donation in the morning, must get VAT sorted tonight or in trouble. Bob

Try Googling hot wire cutting model aircraft wing cores. It's a pretty normal technique.

Richard

Thanks. I just remembered, I have a low voltage power supply somewhere, recall its

12-24v. Might even have some sort of variable output dial on it. Maybe I should add this to the "you know when your getting old" thread !!!! Bob

A very sharp, thin bladed knife will work, such as an old carbon steel carving knife, carefully sharpended.

BugBear

Foam cutter

Should do ok. I used to use a CB radio power supply - straight off the secondary of the transformer. I bought my hot wire from the local model shop who sold them for cutting foam wing cores.

15 minutes work and some timber batten & two screws is all it will take you to make a hot wire cutter. I made a simple wooden H frame from 2"x1" about 3 foot wide, strung the wire across one end of the H and put a string loop across the other, just put a scrap of timber through the string and twisted it up to tension the wire. Cut many a core on that jig though it would tend to get hotter in the middle than at the ends.