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Registered Member #49
Joined: Thu Feb 09 2006, 04:05AM
Location: Bigass Pile of Penguins
Posts: 362
A long time ago (10 years) I recall having a flyback with the oooooold 2x 2N3055 driver and using it to cut fine lines into paper...
... but that was a long time ago and my memory sucks.
I now have need to make a paper cutting device and I wonder if burning through the paper with an arc might be easier to set up than buying a laser.
Does anyone here have a flyback + driver and could give it a try? Just take a standard piece of printer paper and see if you can cut it with the arc... I'd be interested to know how thick/wide the cut is, how fast you're able to move the paper, and how likely the paper is to catch fire. All for any given power level.
With my only current flyback + driver (Royer ZVS @ 12V) it instantly catches the paper on fire, no matter how fast I move the paper through the arc. This arc is quite hot though so that is to be expected.
You'd almost certainly need a very low current arc to just cut paper.
Registered Member #2099
Joined: Wed Apr 29 2009, 12:22AM
Location: Los Altos, California
Posts: 1716
AndrewM wrote ... A long time ago (10 years) I recall having a flyback with the oooooold 2x 2N3055 driver and using it to cut fine lines into paper... ... but that was a long time ago and my memory sucks.
Same here, only we're talking 30 or 40 years. I remember making a bunch of tiny holes in the paper, which would be visible if backlighted.
I think what matters is not the average arc current. It's getting a series of discrete sparks, at rep rate measured in ones or tens per second. That depends on having some (appropriate) small capacitance in the circuit, fed by a relatively weak source. It makes a relaxation oscillator.
Perhaps the parameters to compare notes about are gap length and energy per spark. Warning: putting an analog or digital milliammeter in series with the circuit just described is likely to damage the instrument.
Registered Member #72
Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659
Try putting a few megohms in series with the spark gap, though it will need to be a fairly watty resistor if it's used continuously, and it will need to be high voltage. A series string may be good here. This tends to reduce the arc down to a very thin streak.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
klugesmith wrote ...
Same here, only we're talking 30 or 40 years. I remember making a bunch of tiny holes in the paper, which would be visible if backlighted.
BINGO! yep back in the long, long ago, (1997, when i was in high school) we made a device (without teacher oversight of course) that poked tiny holes in standard paper. it was the oil-can type iggie driven with a 2n3055 and 555, and it punched nice neat holes without burning the paper, i think it drew 12v and 5 amps and was about 20-30 % efficient (so, 15 watts at the spark) and at 2 to 5 kHz it would put a train of holes in paper.
Every flyback (DC or AC old) ive ever used, light paper up and burn it to the ground.
i wonder if instead of round needles, you put thin rectangular electrodes, if you could make perferations, like a roll of paper towels!
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
well can you use a stepper motor to draw the electrode across the sheet?
AndrewM wrote ...
Yes flybacks these days seem like a far different animal that what I had. I was only able to make 1/2" arcs, tops, and they were hair-thin.
Can you turn the voltage down, maybe?
i think changing voltage and current may not be useful, i think you may need a 3 khz square wave, 10% hi, 90% low.... that kind of hv will scorch without burning, but you would need to adjust the freq and PRF for each new material.
Registered Member #2463
Joined: Wed Nov 11 2009, 03:49AM
Location:
Posts: 1546
I have an old Naval Pelorus recorder that uses a selsyn to move a very sharp needle over a moving paper strip chart.
The spark source is a model-T ignition coil. The key to not burning the paper is it moves over a smooth metal surface, which is the other electrode, and the buzz spark can never heat the paper beyond the tiny burn hole because of the metal plate heat sink.
Registered Member #2431
Joined: Tue Oct 13 2009, 09:47PM
Location: Chico, CA. USA
Posts: 5639
radiotech wrote ...
I have an old Naval Pelorus recorder that uses a selsyn to move a very sharp needle over a moving paper strip chart.
The spark source is a model-T ignition coil. The key to not burning the paper is it moves over a smooth metal surface, which is the other electrode, and the buzz spark can never heat the paper beyond the tiny burn hole because of the metal plate heat sink.
this idea of a flat sheet or round roller, might be the key.
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Experiment request: burning paper w/ flyback
