Initial Planning - Flat Panel Foamie

[GPW]

Free Foam , That’s Great !!!

[depatty]

Just ordered the wire to use for cutting the foam. Ordered 5 feet of 20 gauge Nichrome 60 Wire and 10 feet of 27 gauge René 41 Wire from http://jacobs-online.biz/index.htm. He offers free shipping in US on wire orders!

Planning on building a cutting table along the lines of the one at https://www.flitetest.com/articles/hot-wire-foam-sheet-cutting to cut the 4x8 sheets into ~2" to 3" thick sheets.

The 20 gauge will be used for making shaped cutting tips to cut slots for hard points and to round edges.

Now just waiting for the USPS to get it to me.

[depatty]

Nichrome wire came in yesterday! Super fast shipping from Washington state to Alabama!

Now to clear out an area to build a cutting table. Working the next few days so will be the weekend before I get anymore done on it.

Took apart a small APC UPS and got the transformer out of it which is a 120 to 15 volt unit, so should work just fine with the heaver wire that I got to cut channels and round the edges with. Will need to dig up a higher voltage transformer to use with the table as it needs to be ~28 volts to heat the 50 inches of wire to 600 degrees.

Got to thinking about it and remembered I had yet another dead APC UPS in the junk pile so tore it down and got the transformer out of it. Turned out to be a higher wattage unit but voltage is the same. Connected the primaries in parallel and the secondaries in series and got 30 volts out at 120 in.
Only need 1.6 amps at 28 volts so should work just fine.

And some pix of the temporary setup to check output voltage.



The transformers wired to the variac.



Variac voltage setting.



And output voltage from the transformers.

Will do a bit neater job of wiring it all up when I get ready to use it.

Unless you know what you are doing, Please DON'T attempt to do this. The voltage/amperage involved can be deadly if proper safety precautions aren't taken.

[GPW]

DP, Yes , please be careful , we’ve been “tickled’ a couple times by accidentally touching a part of the wire we shouldn't…. Now we insulate EVERYTHING up to the cutting wire itself ...

[depatty]

DP, Yes , please be careful , we’ve been “tickled’ a couple times by accidentally touching a part of the wire we shouldn't…. Now we insulate EVERYTHING up to the cutting wire itself ...

Thanks for the additional warning Glen!

Yep "SAFETY" is the word of the day when working with electricity! I worked as an electronics tech and electrician for over 40 years and can't count the times I have been "tickled", "bit", and had the "sh*t shocked" out of me! None of them are any fun.

I thought about just going with the Variac, as this one will handle up to 10 amps, but it's a direct connection to the AC line, which is just asking for trouble. The 15 volt transformers I'm using give line isolation (no direct connection from the secondary (15 volt side) back to the AC line) so there is "less" chance of electrocution if you happen to touch something and are also grounded. And i WILL have everything insulated and in an enclosure when actually using it! as soon as I get there.

[GPW]

We've dabbled in electronics for many years now and also have been bit a few times ( No fun !!) Now we’re overly safety conscious … dry floors , with rubber floor mats , rubber shoes , and thick rubber gloves if possible … For Electronics we always apply the “left hand in the pocket “ principle , but two handed hot wiring means you have to be extra careful , and of course an isolation transformer is a great idea … We’ve experimented with several gravity powered cutting methods , one involving weights and pulleys , the other just placing the wire on top of the foam , turn it on , catch the bow on the other side … The more we try these hands off methods , the less we might get shocked ….

Wonder if a GFI would help ? or even work ….

[depatty]

Wonder if a GFI would help ? or even work ….

With an isolation transformer in the path I don't think it would trigger as they are designed to trip when there is a current flow from line to ground. Will look and see if I have one kicking around and if so will give it a try.