Foil arc-cutter
Marko, Thu May 18 2006, 09:54PMI think I just found another fun use for that mechabnic pencils.
I simply hooked one with metal head to small 18V DC supply (rectified and filtered small 20VA transformer).
Positive clip was connected to piece of aluminium foil.
I used as thin as possible cape (0,3mm). It showed to be thinner = better.
Graphite vaporises alluminium at contact in very small spot.
Using a ruler it can cut perfect lines with much more speed and accuracy than scissors or scalpel (scalpel also tears the foil every 3 cm).
It may spare a lot of time doing big lifters.
Only problem was That I would need to use piece of ceramic or glass for a ruler.
Due to spot-heating plastic one sticks to the foil edge (poorly, but still does) andI needed to tear it apart every time.
xcept that lines can be drawn almost ideally, in unlimited length and with speed you can draw with a normal pencil.
When graphite rod burns up I just use pencil's reloading system (actually it is used slower than in normal writing on paper)
Basic idea was actually to make something that could cut PCB copper to repairbadly-etched boards.
Copper seems much thicker and harder to blow apart than foil.
I tried to use a huge carbon rod and specialtechnic pencil but I just melted it, and left some black spots on the copper.
Here is some mess I wrote on the foil, and closeup.
Clip is hooked to metal head, if I wanted something more real I could maybe put a wire inside the pen.
Re: Foil arc-cutter
Reaching, Thu May 18 2006, 09:59PM
hehe, thats interesting stuff, great idea
Reaching, Thu May 18 2006, 09:59PM
hehe, thats interesting stuff, great idea
Re: Foil arc-cutter
Maz, Thu May 18 2006, 10:00PM
wow thats qualiy stuff you got there!
i would have never guessed. i only managed to use pencil lead as a resistor...
Maz, Thu May 18 2006, 10:00PM
wow thats qualiy stuff you got there!
i would have never guessed. i only managed to use pencil lead as a resistor...
Re: Foil arc-cutter
Marko, Thu May 18 2006, 11:08PM
Small movie of cutting, note how fast it is.
Looks like some star-trek plamsa scalpel... (if there were no that aligator clip :P )
Marko, Thu May 18 2006, 11:08PM
Small movie of cutting, note how fast it is.
Looks like some star-trek plamsa scalpel... (if there were no that aligator clip :P )
Re: Foil arc-cutter
Michael W., Thu May 18 2006, 11:10PM
Its actually pretty cool, until you touch the graphite to the foil too long, and it glows like a filiment and the explodes....
Michael W., Thu May 18 2006, 11:10PM
Its actually pretty cool, until you touch the graphite to the foil too long, and it glows like a filiment and the explodes....
Re: Foil arc-cutter
Marko, Thu May 18 2006, 11:15PM
This can't happen.
Only when I used huge 1,5 mm carbon rod it would 'weld' to the foil in short periods and heat up too much.
0,3mm can no way do this, it just 'eats' aluminium no matter how is it positioned or how fast it's moving.
Graphite is used mainly because it doesn't stick.
Only sometimes I don't leave enough graphite out and foil shorts to metal part of pencil, blowing a little bigger hole.
Marko, Thu May 18 2006, 11:15PM
This can't happen.
Only when I used huge 1,5 mm carbon rod it would 'weld' to the foil in short periods and heat up too much.
0,3mm can no way do this, it just 'eats' aluminium no matter how is it positioned or how fast it's moving.
Graphite is used mainly because it doesn't stick.
Only sometimes I don't leave enough graphite out and foil shorts to metal part of pencil, blowing a little bigger hole.
Re: Foil arc-cutter
Michael W., Thu May 18 2006, 11:45PM
well yes it can happen, i tried it with thin pencil lead and the lead glowed bright red and exploded....
Michael W., Thu May 18 2006, 11:45PM
well yes it can happen, i tried it with thin pencil lead and the lead glowed bright red and exploded....
Re: Foil arc-cutter
Alex, Fri May 19 2006, 12:21AM
Neat.
I wouldn't expect it to work well as a PCB etching tool, because there would be carbonized copper remains in the cut paths. Maybe it could be wire brushed or chemically cleaned reliably, I'm not sure. Even if it could, it might not be very good for making intricate boards, but it'd at least be handy for lashing up a quick prototype.
Alex, Fri May 19 2006, 12:21AM
Neat.
I wouldn't expect it to work well as a PCB etching tool, because there would be carbonized copper remains in the cut paths. Maybe it could be wire brushed or chemically cleaned reliably, I'm not sure. Even if it could, it might not be very good for making intricate boards, but it'd at least be handy for lashing up a quick prototype.
Re: Foil arc-cutter
Bjørn, Fri May 19 2006, 01:45AM
Pencil lead can explode violently enough to cause damage to skin and eyes when heated. Heat it slowly, never cool it in a liquid and keep it away from your eyes.
Bjørn, Fri May 19 2006, 01:45AM
Pencil lead can explode violently enough to cause damage to skin and eyes when heated. Heat it slowly, never cool it in a liquid and keep it away from your eyes.
Re: Foil arc-cutter
..., Fri May 19 2006, 05:21AM
Great idea!
I have been known to cut out Al foil by just dragging the alligator clip across it, but that gets messy and I can't use much current... I never though to use a pencil lead
I can vouch for the exploding thing... They will heat up to a certain point, the suddenly go bang shooting little carbon projectiles everywhere. I suppose if it is inside the pencil all should be fine though...
As to pcb etching... I wouldn't really recommend using this. There is the problem of the carbon left behind, but also you can only make thin lines, not obliterate a nice gap between traces to prevent solder bridges forming... I would recommend a dremel tool for that... I hear the cutoff wheel work well for strait lines and those little SiC masonry bits for the detail work...
But both of these can be surpassed by the sharpie/enchant if you know what you are doing...
..., Fri May 19 2006, 05:21AM
Great idea!
I have been known to cut out Al foil by just dragging the alligator clip across it, but that gets messy and I can't use much current... I never though to use a pencil lead
I can vouch for the exploding thing... They will heat up to a certain point, the suddenly go bang shooting little carbon projectiles everywhere. I suppose if it is inside the pencil all should be fine though...
As to pcb etching... I wouldn't really recommend using this. There is the problem of the carbon left behind, but also you can only make thin lines, not obliterate a nice gap between traces to prevent solder bridges forming... I would recommend a dremel tool for that... I hear the cutoff wheel work well for strait lines and those little SiC masonry bits for the detail work...
But both of these can be surpassed by the sharpie/enchant if you know what you are doing...
Re: Foil arc-cutter
Marko, Fri May 19 2006, 06:11AM
Not inside the pencil, I tried it.
When etching foil spark is on microscopic level and can interestingly never generate enough heat to do it.
After tons of etching temp of pencil tip increases by just few degrees.
If I touch something too thick to etch (aligaor clip) then it does glow, and very brightly but it doesn't explode. I guess it's because if it's too short.
Only problem is that then I melt sensitive parts of pencil in very short time.
Touching to foil 'too long' does nothing, just etches anywhere you drag it.
Cutting is based on constant 'bad contact' between electrode and foil because foil constantly melts in it's way.
If you use few cm of lead and hook it directly to power supply it is normal for it to overheat and blow up.
If it is thicker there is even more risk of explosion and sharpnels are much bigger and dangerous.
Marko, Fri May 19 2006, 06:11AM
well yes it can happen, i tried it with thin pencil lead and the lead glowed bright red and exploded....
Not inside the pencil, I tried it.
When etching foil spark is on microscopic level and can interestingly never generate enough heat to do it.
After tons of etching temp of pencil tip increases by just few degrees.
If I touch something too thick to etch (aligaor clip) then it does glow, and very brightly but it doesn't explode. I guess it's because if it's too short.
Only problem is that then I melt sensitive parts of pencil in very short time.
Touching to foil 'too long' does nothing, just etches anywhere you drag it.
Cutting is based on constant 'bad contact' between electrode and foil because foil constantly melts in it's way.
If you use few cm of lead and hook it directly to power supply it is normal for it to overheat and blow up.
If it is thicker there is even more risk of explosion and sharpnels are much bigger and dangerous.
Re: Foil arc-cutter
Electroholic, Fri May 19 2006, 09:57AM
I was using 0.5 lead in my foam cutter,
it worked perfectly, but when i crank current up,
the middle part of it glow white hot.
It oxidized itself, and got two "extremely" sharp carbon needle.
so I guess only thick lead, like >1mm, would explode.
Electroholic, Fri May 19 2006, 09:57AM
I was using 0.5 lead in my foam cutter,
it worked perfectly, but when i crank current up,
the middle part of it glow white hot.
It oxidized itself, and got two "extremely" sharp carbon needle.
so I guess only thick lead, like >1mm, would explode.
Re: Foil arc-cutter
Marko, Fri May 19 2006, 10:45AM
Good guess.
When I tried something similar with a 1,5mm carbon rod it used to explode violently, especially if I leave too much of it free.
I had to take cover when doing this.
To reduce heating electrical contact must be as close top the tip of lead, because of high ohmic resistance of graphite.
Also one important thing is to use negative pole of power supply on the electrode, I didn't belive it's important untill I tried.
With positive pole on the pen it sticks to foil and creates some garbled, wide cut.
Marko, Fri May 19 2006, 10:45AM
guess only thick lead, like >1mm, would explode.
Good guess.
When I tried something similar with a 1,5mm carbon rod it used to explode violently, especially if I leave too much of it free.
I had to take cover when doing this.
To reduce heating electrical contact must be as close top the tip of lead, because of high ohmic resistance of graphite.
Also one important thing is to use negative pole of power supply on the electrode, I didn't belive it's important untill I tried.
With positive pole on the pen it sticks to foil and creates some garbled, wide cut.
Re: Foil arc-cutter
Psyko, Fri May 19 2006, 08:03PM
I just tried it with a 0,7 mm pencil. Incredibly powerfull. Nicest find man
But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
I have tried to melt some solder wire with the pencil and the system could nearly solder. Nearly .
Psyko, Fri May 19 2006, 08:03PM
I just tried it with a 0,7 mm pencil. Incredibly powerfull. Nicest find man
But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
I have tried to melt some solder wire with the pencil and the system could nearly solder. Nearly .
Re: Foil arc-cutter
Coyote Wilde, Fri May 19 2006, 11:14PM
Coyote Wilde, Fri May 19 2006, 11:14PM
Psyko wrote ...
But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
Because the carbon is burning; steel doesn't react nearly as much in air.But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
Re: Foil arc-cutter
Marko, Fri May 19 2006, 11:34PM
Nope, It's not burning at all in foil-cutting operation.Carbon lead gets just warm a bit.
It can cut for very long getting just a bit wasted.
It does the job well because graphite doesn't tend to weld to metals like a sell tip would do.
This makes 'everlasting point of bad contact' anywhere it goes, and the spark occuring at the spot blasts the alluminium into vapour.
I also tried it for solder wire and it works, but I don't know for the boards.
I suppose that 'soldering' ability is just from ohmic heating of the carbon rod (graphite has a quite high ohmic resistance) and transferring it to solder, as it's too massive to get vapourised like alluminium foil.
You can distinguish these two events by occuring temperature andwasting of carbon lead.
If it's just filamenting it will be burned in series of small explosions and get consumed pretty fast.
Marko, Fri May 19 2006, 11:34PM
Nope, It's not burning at all in foil-cutting operation.Carbon lead gets just warm a bit.
It can cut for very long getting just a bit wasted.
It does the job well because graphite doesn't tend to weld to metals like a sell tip would do.
This makes 'everlasting point of bad contact' anywhere it goes, and the spark occuring at the spot blasts the alluminium into vapour.
I also tried it for solder wire and it works, but I don't know for the boards.
I suppose that 'soldering' ability is just from ohmic heating of the carbon rod (graphite has a quite high ohmic resistance) and transferring it to solder, as it's too massive to get vapourised like alluminium foil.
You can distinguish these two events by occuring temperature andwasting of carbon lead.
If it's just filamenting it will be burned in series of small explosions and get consumed pretty fast.
Re: Foil arc-cutter
ragnar, Sat May 20 2006, 01:06AM
Much like a lightbulb, the current running through your carbon/graphite electrode is also self-limiting as the graphite heats up. This reduces sputtering and welding. Similarly you can vary the current by using a longer length of graphite between your supply and target.
ragnar, Sat May 20 2006, 01:06AM
Much like a lightbulb, the current running through your carbon/graphite electrode is also self-limiting as the graphite heats up. This reduces sputtering and welding. Similarly you can vary the current by using a longer length of graphite between your supply and target.
Re: Foil arc-cutter
Marko, Sat May 20 2006, 10:03AM
Current drawn in the cutting is much lower than short-circuit current possible.
Length of graphite interestingly makes no difference at all, as the spark limits the current (It draws something like small 'bangs' from the filter cap but overall current is quite low).
Your self-limiting effect probably occurs only on microscopic scale on point of contact and this prevents welding.
'Electron wind' from the electrode also seems to help blowing the vapour away.
Marko, Sat May 20 2006, 10:03AM
Much like a lightbulb, the current running through your carbon/graphite electrode is also self-limiting as the graphite heats up. This reduces sputtering and welding. Similarly you can vary the current by using a longer length of graphite between your supply and target.
Current drawn in the cutting is much lower than short-circuit current possible.
Length of graphite interestingly makes no difference at all, as the spark limits the current (It draws something like small 'bangs' from the filter cap but overall current is quite low).
Your self-limiting effect probably occurs only on microscopic scale on point of contact and this prevents welding.
'Electron wind' from the electrode also seems to help blowing the vapour away.
Re: Foil arc-cutter
cbfull, Sat May 20 2006, 06:07PM
I love all of the creative ideas on this board! This method of cutting foil sounds like killing a fly with a bazooka. I use a cutting mat and a wheel blade/straight edge when I need to cut a straight line in a hurry. I'm not sure how it could get any faster.
On the other hand, pencil lead is much cheaper than those round blades. I'm waiting to see how long it takes for aluminum to dull a steel blade.
cbfull, Sat May 20 2006, 06:07PM
I love all of the creative ideas on this board! This method of cutting foil sounds like killing a fly with a bazooka. I use a cutting mat and a wheel blade/straight edge when I need to cut a straight line in a hurry. I'm not sure how it could get any faster.
On the other hand, pencil lead is much cheaper than those round blades. I'm waiting to see how long it takes for aluminum to dull a steel blade.
Re: Foil arc-cutter
Marko, Sat May 20 2006, 06:35PM
It was actually intended to etch and repair PCB's, but it didn't work there too well.
And how about writing letters, circles and very small shapes with a blade (I just needed two small circles to cover small sphere, I just drew them around solder wire roll...).
Pizza blade is also good idea but I have only a wavy one
Marko, Sat May 20 2006, 06:35PM
cbfull wrote ...
I love all of the creative ideas on this board! This method of cutting foil sounds like killing a fly with a bazooka. I use a cutting mat and a wheel blade/straight edge when I need to cut a straight line in a hurry. I'm not sure how it could get any faster.
On the other hand, pencil lead is much cheaper than those round blades. I'm waiting to see how long it takes for aluminum to dull a steel blade.
I love all of the creative ideas on this board! This method of cutting foil sounds like killing a fly with a bazooka. I use a cutting mat and a wheel blade/straight edge when I need to cut a straight line in a hurry. I'm not sure how it could get any faster.
On the other hand, pencil lead is much cheaper than those round blades. I'm waiting to see how long it takes for aluminum to dull a steel blade.
It was actually intended to etch and repair PCB's, but it didn't work there too well.
And how about writing letters, circles and very small shapes with a blade (I just needed two small circles to cover small sphere, I just drew them around solder wire roll...).
Pizza blade is also good idea but I have only a wavy one
Re: Foil arc-cutter
Electroholic, Sat May 20 2006, 06:57PM
and dont' forget graphite's non stick property!
Electroholic, Sat May 20 2006, 06:57PM
Coyote Wilde wrote ...
Psyko wrote ...
But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
Because the carbon is burning; steel doesn't react nearly as much in air. But why is carbon so powerfull, compared with metal ( I tried with steel ) ?
and dont' forget graphite's non stick property!
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