Monday, November 7, 2011

Large Scale Cutting

Hello everyone,

Just another question on cutting foam..! I've gotten this one a few times before, not necessarily for surf boards, but just larger hand held projects. The questions are in blue, take a look!

I am a surfboard builder and am interested in cutting blanks out of EPS foam -I know nothing about electrical systems but would like to build my own cutting tool- 
what do you recomend for this type  of project?

I'd certainly recommend a large scale hand held cutter

the bow needs to be aproximately 32" inches wide. 

You should easily be able to make this cutter at any length you desire. 

You could even use 3/4" PVC rather than 1/2". The 3/4" will be a bit heavier, but will be more rigid and strong for larger cuts. 

If you want me to make you the electrical end caps, just let me know and I can send them to you. But I will be uploading some new videos tonight, so you may be able to follow along in those and make them yourself. 

what should I use as my power source? ( I have been looking at variacs on ebay)

The variac series are nice. They are an AC power supply rather than the typical DC power, which works well at a wide range of voltages and amperes. has the greatest selection of variacs available online, and they are very reasonably priced. Check out what they have for AC transformers, and you can always get model numbers to see what you can find online.

Be VERY VERY careful when using AC transformers. Typically any voltage above 45 volts can penetrate human skin and cause electrocution. While you'll probably need less than 20 volts, ever, this wont be a problem. But just be careful!

Here are two power supplies I'd choose for your project

The first one SHOULD be enough power for you. It says it can only put out 3.3 amps at 150 volts, but its rated as a 500VA (or watt) transformer. So at lower voltages you should be able to safely obtain a higher amperage.  I'd guess the first one will be more than enough for your project, but the second one will DEFINATELY work!

I  can build the cutting bow but dont know what gauge on nichrome wire to use or if it would be best to use stainless steel.

I would recommend NiChrome, only because it is most reliable and there are known electrical values. (Meaning, we know how much amperes/voltage it requires to heat up.)

I'd recommend either 24 gauge or 22 gauge wire. 20-22 gauge are pretty stiff, so might not be ideal. I've personally used 26 gauge at lengths under two feet, but you should probably use 24 gauge.

the good news is, Nichrome is CHEAP. so you can always buy 24 and 22 and see which you like better.

On the other hand, with the variac transformer you will be able to test out 22 gauge, 24 gauge nichrome, as well as stainless steel if you wanted. The power supplies are hearty enough that they will heat up a lot of different wires. 

Check out this fishing line retailer, they have stainless steel fishing line, that I had a customer use for making RC plane wings. He said he liked it better than nichrome at longer lengths and is pretty cheap too.

here is the link to their stainless steel leader wire page

I don't remember the recommend lb test wire, but I THINK it was between 30-60lb test stainless steel wire that worked the best. But at a few dollars per pack, it's still pretty cheap to buy a variety of wires, and see what you like!


That's it guys! I hope it was some what informative. And remember, all those links are already on the website!