EPS Hotwire Setup Pix

General Discussion
1

ok, here it goes. Attached are photos of my very crude hotwire setup.

xSection - I bought a 12’ x 2’ x 30" block of EDRO EPS from an Insulfoam distributor for $150. The block yielded 5 blanks and the last two feet in all but one board was wasted. Next time I’ll get a 10’er and an 8’er.

Hotwire - Made with a scrap piece of ply, an old extension cord, a small spring, eyehooks, and some old light fixtures. All this stuff I had laying around my house.

Resistance - I have a total of 350 watts in this setup but it is easy to add or subtract.

I guess I am limited to three photos so I’ll reply to my own post with the rest.

Cheers,

Gary

2

Spring - If the 30 gauge NiCr wire gets hot the spring catches the slack.

Slicing – Steady now.

Mirror – A piece of mirror duct taped to the ply. Now my wife does not have to help.

5

My text did not go through on the last ones:

Top slice - cool photo after slicing the top foam

I’m Free - Slicing like a hot knife through butta.

Two blanks - both done in a total of 20 minutes

Band Saw - This is a bit overkill but really easy. Another method would be to hand saw and hit with a planer. Greg cranks up his regulator and slices with a long piece of NiCr.

Pieces - The stringer possibilities are endless

Warped - Usually the pieces are a little off flush so I use this handy little jig to true up the blank.

This reply:

Fixed Warp - all better now.

Clamp - I either use Elmers or yellow wood glue.

That’s it.

Gary

6

Nice! I liked the mirror, will add on my setup.

regards,

Håvard

7

I have never set up my own blanks like you are doing. I always just buy clark blanks and if I need a special stringer setup I just have them construct it. It seems that doing it like you are doing is an art in itself. I was wondering, besides being able to make any stringer set up that you want, what is the advantage of gluing up your own blanks? Is the cost cheaper? Even when you factor in the time spent doing it?

8

Gary -

I’m completely blown away! Thanks very much for posting the photos and explanations. The two blanks on edge show what looks to be a fantastic profile. I like the high tech resistance device also… how did you determine the correct bulb wattage? I seem to remember a formula based on wire length and diameter but can’t find it via search.

Check your e-mail.

John

9

That’s pretty neat. I’ve always been interested in seeing how that all worked. Thanks for the pics.

10

TSaunders,

The foam runs about $20 for the foam for a 10 Foot long board and, since I have the bandsaw and resawing capabilities, a 1/4" basswood stringer runs about $5. The flexibility in design is great because I can play with curves in Adobe Illustrator and come up with any plan shape or rocker profile I want. Also, there is no such thing as going too deep into the foam because the EPS is the same density throughout.

John,

Trial and error. I trialed with a single 200 watt bulb and decided to add another 100 along with the dimmer switch. It also depends upon your NiCr gauge, extension cord thickness and length.

Cheers,

Gary

11

After mcuh searching for NiCr wire, I gave up and tried guitar string, after wasting about four of these I gave up and that, went to the tackle shop and found what I needed!

This stuff is super strong and can handle up to 24v at 5 amp, but realistic? You only go about 16v for foam… Cuts through gluelayers (White elmers type) too!!

Bow is 9mm ply so it’s quite stiff, got a door coil to pick up heat-slack (it sings as it heats up!!), an on/off switch and…

…a switching power supply, but hey, these are available in most electronics shops (radio shack type shops and some computer spare parts shops)

…got about 12 ft of heavy duty wire (230v rated) with crock clamps to hook it up, it doesn’t get warm during operation, this is a problem with thinner wires, the last one actually smoked!! (loudspeaker wire is NOT DONE!!)

Oh, and notice on the picture that the feed doesn’t actually connect at the switch to the hotwire but there is a piece of 230 rated wire going down the bow to the hook, this is to avoid over-heating on the non-cutting portion of the hotwire, trust me, learned the hard way…

for those of you in NiCr poor areas, this setup works like a charm and slices and dices through EPS200 (30kg/m2 density) foam like soft cheese…

P.S. always be carefull with hotwire setups, be aware that you are “abusing” equipment for purposes which they were not intended, your mileage may vary and it’s all at your own risk!! I am assuming all readers of this site are adults and take their responsability for their actions, I share this info for the informed anyone else had better not try this at home!! I got my fair share of shocks and burns and even a blown fuse!! This is not a toy and requires a responsible attitude to do properly, you’ve been warned…

12

Tell me more about this door coil!

I recently got sick of the slow cut on the battery charger and got a nice variable speed transformer of eBay. Less than AU$20 delivery inclusive.

Cuts great for a short time then overheats and cuts out. So I think I need something like the door coil.

Anyone else have any suggestions?

13

Surfer_dave wrote:

……got about 12 ft of heavy duty wire (230v rated) with crock clamps to

hook it up, it doesn’t get warm during operation, this is a problem with thinner

wires, the last one actually smoked!! (loudspeaker wire is NOT DONE!!)

Oh, and notice on the picture that the feed doesn’t actually connect at the switch

to the hotwire but there is a piece of 230 rated wire going down the bow to the

hook, this is to avoid over-heating on the non-cutting portion of the hotwire, trust

me, learned the hard way……

Please note that it is the wire guage, not the voltage rating that determines how much current the wire can carry without getting hot. The 230V rating simply means that the insulation on the wire will not break down and arc to the other wire or to ground for voltages up to 230V.

Also it is important to remember that the SMALLER the guage of the wire, the GREATER the cross-sectional area of the conductor and the MORE CURRENT it can carry without getting hot. Examples (as best I remember) in order of high current capacity to low current carrying capacity:

00 guage (e.g. car battery cable) →

4 guage (typ arc welding leads) →

12 guage (heavy duty extension cord) →

16 guage (light duty extension cord) - >

18 guage (speaker cables?) →

20 guage (heavy duty hot wire) →

28 guage (light duty hot wire) →

32 guage (wire-wrap wire?)

If you know how many amps are flowing at your desired hot wire temperature, you can often find out what guage wire you need by checking the packaging on extension cords (which usually list the wire guage and sometimes also the max amperes it is rated for) in a hardware store. Then look for the wire guage that gives you your desired amperage (or more–i.e. a smaller wire guage) in whatever type of wire you want.

14

Has anyone here tried the “dimmer switch plus 25v 2amp transformer” type hotwire power sources of the kind listed on the Hot wire foam cutter and Foam Cutter web pages?

If so, what did you think of the thing?

Regards,

15
Quote:

Tell me more about this door coil!

I recently got sick of the slow cut on the battery charger and got a nice variable speed transformer of eBay. Less than AU$20 delivery inclusive.

Cuts great for a short time then overheats and cuts out. So I think I need something like the door coil.

Anyone else have any suggestions?

The door coil is just a big spring that keeps the cutting wire taught, necessary when you shove some volts down the wire it stretches quite a bit so you need to keep it tight or it will wobble and get generally messed up in your foam.

I think the stretch may be more with the steel wire I use than some of the more exotic wires but that’s just my guess.

my 2cts, your powersupply is under powered and is overheating and thermally cutting off, you need to get a beefier one… the one I pictured cuts out when I max it at say 24v@5 amp!! heck it turns steel 20 guage wire into a light bulb at that but then livin’ on the edge is part of the fun!(see warning on my previous post!!) seriously though, at 16v@5 or 6 amp, you can cut EPS like cheese and the pictured power supply doesn’t moan about it…

16

Cool, thanks for that. Luckily the wife needs a new train transformer anyway :smiley:

Did you look at those other links I posted just above?

Oh, and what is this?

Thanks for sharing your thoughts and ideas!

17
Quote:

Cool, thanks for that. Luckily the wife needs a new train transformer anyway :smiley:

Dunno bout a train transformer, they usually cut out when shorted like this to protect the toys when they derail… also, I think Amperage may be on the low end…

Quote:

Did you look at those other links I posted just above?

yep… nearly killed myself with a dimmer… but that may be my karma…

Quote:

Oh, and what is this?

Holy smokes batman! He’s discovered the doomsday device!!

actually it’s an on/off switch, it’s nice to have nearby when something goes wrong and the powersupply is on the OTHER end of your longboard blank…

Quote:

Thanks for sharing your thoughts and ideas!

my pleasure, thats nice about swaylocks, two guys can show up each with their own idea, after a while they go away with two ideas each!

PS I hate spackle too… microspheres that’s my trip…

18

Hi Dave!

Dunno bout a train transformer, they usually cut out when shorted like this to protect the toys when they derail… also, I think Amperage may be on the low end…

I think you are preaching to the choir :wink:

yep… nearly killed myself with a dimmer… but that may be my karma…

More info?! I have already started building one of those suckers. Did you have it fused and running 25v 2amp AC? What happened?

Holy smokes batman! He’s discovered the doomsday device!!

hehe!

actually it’s an on/off switch, it’s nice to have nearby when something goes wrong and the powersupply is on the OTHER end of your longboard blank…

Yeah, good idea. Might do that myself. What kind did you use, out of interest?

my pleasure, thats nice about swaylocks, two guys can show up each with their own idea, after a while they go away with two ideas each!

Can I get an “Ahmen”?! :stuck_out_tongue_winking_eye:

PS I hate spackle too… microspheres that’s my trip…

Good man! Much better solution. Lighter and gives you a chemical bond :smiley:

19
Quote:

Hi Dave!

Yo Doug!

Quote:

yep… nearly killed myself with a dimmer… but that may be my karma…

More info?! I have already started building one of those suckers. Did you have it fused and running 25v 2amp AC? What happened?

was one of those Ikea 24v slider-dimmer setups, hooked it to the hotwire and switched it on and got sparky with it… I dunno, maybe it was just a bum dimmer, maybe it was my karma…

Quote:

actually it’s an on/off switch, it’s nice to have nearby when something goes wrong and the powersupply is on the OTHER end of your longboard blank…

Yeah, good idea. Might do that myself. What kind did you use, out of interest?

uhm… the on/off kind, you know, wall switch for lightbulb?

Quote:

my pleasure, thats nice about swaylocks, two guys can show up each with their own idea, after a while they go away with two ideas each!

Can I get an “Ahmen”?! :stuck_out_tongue_winking_eye:

Ahmen?

20

Hi, already thinking ahead to my next “project” I’ll have some spare epoxy so want to give the home glue up thing a try.

Thinking hot wire, I’ve got a dimmer switch, guitar string, croc clips, wire, springs eyelets ect and all knocking around in one of my “may come in useful one day” piles, and plenty of wood off cuts.

I had a look in the electrical shop for a transformer, most only go up to 12V, but 2 caught my eye,

One rated at 15v, max 4.5Vamp and the other 25v max 9.5Vamp, will these be any good. do I need light bulbs for risistance ???

Cheers.