[3Dsigns]

This is the cutter I built. It can handle two 3x4x10 blocks at once, has 4 axis capability and a 5th axis turntable. But I was using a DC power supply to heat the 84" Nichrome wire and for some reason the PS died when I was almost done with the first job. Any ideas? Someone has told me that I should be using a "Variac" but, being A/C, that sounds dangerous. What do you think? Thanks
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https://www.youtube.com/watch?v=PDEE6vXHaTg

[109jb]

I made a non-CNC foam wire-cutter using a small transformer and a standard light dimmer switch. I can't remember the specs of the transformer, but I think it was just a doorbell type transformer. It worked well, but was only used with a 60" stainless steel cutting wire. The dimmer switch controlled the input to the transformer and allowed adjusting the temperature of the wire. Since the output of the transformer can't exceed the transformer rated output, which is considered "low voltage" it is pretty safe.

[underthetire]

Last foam cutter I built for those 4th grade mission projects, glad kids are older now, I used my bench power supply I got on eBay for ~60.00. infinity adjustable that way.

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[3Dsigns]

Last foam cutter I built for those 4th grade mission projects, glad kids are older now, I used my bench power supply I got on eBay for ~60.00. infinity adjustable that way.

Sent from my A3-A20FHD using Tapatalk

Thanks, that is basically what I had before it died. Dr Meter HY3005F 3 Variable Triple Output Linear DC Regulated Power Supply 30V5A | eBay
except mine was an "Arksen" probably made at the same Chinese factory.

[john-100]

what voltage and current setting did you have for the hot wire cutter ??

if you had it set to 6V at 5A the linear regulator could be dissipating 150W as heat
while the power supply should normally cope with this, mounting it in an enclosure
could over heat it enough to open a thermal fuse embeded in the transformer

if nothing works - no display on the meters check all the fuses you could be lucky

John

[3Dsigns]

what voltage and current setting did you have for the hot wire cutter ??

if you had it set to 6V at 5A the linear regulator could be dissipating 150W as heat
while the power supply should normally cope with this, mounting it in an enclosure
could over heat it enough to open a thermal fuse embeded in the transformer

if nothing works - no display on the meters check all the fuses you could be lucky

John

The PS has 2- 30Vchannels and I was running them both in series at about 26V each, so I suppose it was 52V. The current was set on max (5A) but the meters were reading 4.6A

[john-100]

I would of thought 2x 26V at 4.6A the power supply should of been OK unless there is some thing in the small print
not to run it continuously at maximum current

with the power supply current limit at 5A, the inrush current into the cold wire is limited to 5A untill the wire heats up
to dissipate 239W the wires resistance when hot must be just over 11 ohm

John

[3Dsigns]

So that's good? I wonder why the power supply died?

[handlewanker]

Hi....if the transformer duty cycle is low you won't get much run time........don't ask me how I found that out with a 240 volt to 110 volt 2,000 watt transformer on an electric oven cooking my supper.

I've got a couple of computer power supples and the 12 volt 50 amp output on one looks promising for a foam cutter I want to have a go at.........the power supplies are switch mode and don't use a transformer to drop the mains voltage to 12 volts.........controlling that might be a problem.

A dimmer switch wired in to a transformer primary will control the secondary output, so the resistance factor of the wire is not necessary.....it's whatever amperage it takes to make the wire hot enough, provided the trannie has enough amperage.....it should always be rated for use at half it's capacity for continuous run time.

As the cutting wire is the load resistance, just adding a wire wound resistance in series should make the transformer run at a lower loading......I think.......but the duty cycle will mean any loading will cause it to get warmer as the time goes by.
Ian.

[3Dsigns]

I took one of the capacitors by a motor repair shop because my meter wouldn't read high enough for 4700uf. They said it was bad. So I ordered another capacitor but in the meantime ordered another DC power supply. Gwinstek SPS 606 60V 6A DC Power Supply | eBay This one sells new for over $400 more than I paid for it on Ebay. Maybe it's a good one. According to this handy online calculator, I only need 5.19A @60v to power my wire. NichromeCalc

[handlewanker]

Hi.....you don't need DC or any electronic circuit to just heat a piece of wire.....this is the same as a soldering iron in reality.

An AC transformer with a simple $5 EBAY PWM controller to vary the amps is all you need......it works the same as a dimmer switch dimming a light bulb which is just a resistor/thin wire running in a vacuum.
Ian.

[3Dsigns]

OK, thanks!

[Kenniffs]

I use an icharger 106b. It has a foam cutting setting that gives me a constant current source regardless of my wire length. My wire is only 1Mt across, you might need a 206b to drive your longer wire.
I was lucky, I already had the icharger for charging my lipo batteries.

[junkdog]

we use ac variac as power supply to cut 4'x4'x10'
blocks all day long for foam for skateparks and landscaping backfill
nichome wire between to wooden handles connected to the power supply
as redneck as you can get
but we cut semi truckloads of the stuff

i like your rig would have been easier for some complex shapes