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Stainless Steel Cutting Wire - 2/2/2004 5:00:46 AM   
Sendhendrix


 

Posts: 9
Joined: 1/20/2004
From: Lavista, NE, USA
Status: offline 		Hey folks I have a question about using fishing leader wire for foam cutting...if any of you has an ohmmeter could you please tell me how much resistance per foot this stuff is? Please also include the size of the wire.

My problem is I made a power supply out of a bell transformer and a dimmer switch. This gives me 24V output. However, it's only rated at around 20 watts, which means I need to keep my amperage around 1!! Obviously I can crank the voltage down with the dimmer but... anyway I could go on and on (my hair is on end and I have wild eyes) but could somebody please tell me what the resistance per foot is of their leader wire in the various popular cutting sizes...(.020? .030?)

Thanks.
       Post #: 1

RE: Stainless Steel Cutting Wire - 2/2/2004 5:09:51 AM   
michpittsman


 

Posts: 598
From: Muskegon, MI, USA
Status: offline 		I tried a dimmer switch years ago and promptly blew it out. Why not use the nichrome wire that Sig sells? That is what it's for. Also, most of your fishing leader wire is nylon coated. I would check it before trying it. I think the DuBro pull-pull wire is uncoated, and may be usable. Good luck...JIM

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RE: Stainless Steel Cutting Wire - 2/2/2004 6:51:51 PM   
gronker


 

Posts: 9
Joined: 1/8/2003
From: ca
Status: offline 		Cabelas 0.024 SS leader - actual dia. is 0.022" Resistance 0.9 ohms/yard. I run 4 to 5 amps in a 42" bow at 5V on a 12V (100W) halogen light transformer. That's 20 - 25 W so the doorbell transformer is barely enough. and probably not rated for continuous output at 20W.

< Message edited by gronker -- 2/2/2004 2:01:43 PM >

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       Post #: 3

RE: Stainless Steel Cutting Wire - 2/11/2004 3:07:51 PM   
nouser


 

Posts: 22
Joined: 2/10/2004
From: no town, SC, USA
Status: offline 		if your wired right almost anything works at any length wire. as for wire i use 3 kinds with excellent succes. 1st pic over all others is .016 carbon steel music wire, 2nd is 304 stainless .016, and 3rd is a lower carbon steel same size. the ultra high carbon spring steel wire is best, no stretch, and it practically refuses to kink,bend or twist. you can get any wire in the world from McMaster-Carr, who gets theirs from Malin co. ni-chrome is out, it's weak, hard to get, and costs more. for the price of a few feet of ni-chrome, you can buy about a 1/8 mile of SS or carbon steel (in 1lb. spools).

i saw one webpage where the kid was using steel guitar string from his own guitar (the E string). he gets his wire from his local music shop at 3 dollars a piece.

(another webpage) another savy teen bought a lionel trane transformer on e-bay for $7and uses that. to be honest i wish i thought of that before i built mine.

i've made every silly combination work, the only trick to hot wire bows is keeping down the voltage. i still have the original 5amp fuse in the control box i made, hasn't blown yet. i also put a volt meter on my bow before using it. 7.8 volts is my magic number from the transformer. the only wire i ever broke is the one impact tested with pliers while it was on and hot. think tension and strength of wire, adjustable voltage does the rest. good luck.

(in reply to gronker)
       Post #: 4

RE: Stainless Steel Cutting Wire - 2/13/2004 2:58:57 AM   
marvintm



Posts: 77
Joined: 9/3/2003
From: Cleveland, OH,
Status: offline 		The 24v x 20w transformer may not work on a wide cut. You may get it hot, but it takes even more power during cutting as it looses heat to the foam. Play with it.

The stainless leader wire is available in greater lengths than guitar string if your doing big wings. You can find it in the more serious tackle stores or saltwater bait shops, usually not at in-land Wal-marts.

Get a "variac". They run around $80-90 on e bay for a 10 amp enclosed benchtop model in good shape.

I have 5 nice ones I've been meaning to sell. Just a bear to ship at 10 lbs each. Pics available if anyone interested. marvintm@adelphia.net

< Message edited by marvintm -- 2/14/2004 1:48:20 PM >

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RE: Stainless Steel Cutting Wire - 2/13/2004 10:27:51 AM   
arx_n_sparx


 

Posts: 45
Joined: 2/9/2004
From: Burlington, ON,
Status: offline 		Oh man, where to start......

First of all, here in Canada a doorbell transformer is the only type of transformer that doesn't need a fuse. This is because the current is self limiting - NOT a good thing if you want to hot wire with it. You need some amperage behind it to get the heat, not just voltage. I'd recommend a transformer that will give you 4 amps (you'll probably only need 2A, but why overtax it?) - at 12V, get a 50VA (watts) Tx - at 24V, get a 100 VA.

For heat control, a dimmer will be fine on the primary side of the transformer IF you use a dimmer made for an inductive load (i.e. ceiling fan speed control).

As far as the wire goes, I use .018" SIG control line wire - works well on my 4 1/2' bow. I also made a "scroll saw" type cutter where the wire is vertical for cutting out parts like bulkheads, etc.

Hmmm....just thinking here. If you go to the local computer repair shop, ask if they would give you an old dead power supply or 3 (they usually toss them out). You should be able to scrounge a working transformer out of one of them. The dimmer will set you back some - I'd guesstimate ~$10 or so.

Once you get it all up and working, it's a real pleasure!

Regards,

Brad

(in reply to marvintm)
       Post #: 6

RE: Stainless Steel Cutting Wire - 2/13/2004 12:48:34 PM   
nouser


 

Posts: 22
Joined: 2/10/2004
From: no town, SC, USA
Status: offline 		OK maybe I should have mentioned I use a 50va transformer from an air-conditioner with a standard $10 light dimmer. Read the VA rating on a transformer, anything less than 40-50 volt amps will be smoked in short order. Doorbell transformers are for doorbells, if you want a transformer that can take endless abuse for years, use something with a high va. Put your fuse between the trans and your dimmer on the hot wire (black). If you go to Radio Shack for this stuff just throw your money in trash and stay home, at least you will save gas. Buy your gear at an ac/r supply house, or a hardware store. Keep it simple, don't add a bunch of crap to it (lights meters etc..), you only raise your amperage causing endless problems.

With that combination ANY strong wire will work.

(in reply to arx_n_sparx)
       Post #: 7

RE: Stainless Steel Cutting Wire - 2/13/2004 2:14:29 PM   
arx_n_sparx


 

Posts: 45
Joined: 2/9/2004
From: Burlington, ON,
Status: offline 		Fuse should be between the hot incoming wire and the switch. It'll work as binkdaddy has said, but it's not good electrical practise....

(in reply to nouser)
       Post #: 8

RE: Stainless Steel Cutting Wire - 2/17/2004 12:50:48 PM   
nouser


 

Posts: 22
Joined: 2/10/2004
From: no town, SC, USA
Status: offline 		OK I'll split a hair with ya...hehhe. I was following the system wiring at work I service for protecting the more costly components in electric motor starters and compressors. My goal to save my transformer and bow, forget the $10 switch. If the fuse blew, the switch would be unloaded and saved anyway. Either way works. But yeah, any decent electrical engineer would say fuse first on everything.

(in reply to arx_n_sparx)
       Post #: 9

RE: Stainless Steel Cutting Wire - 2/20/2004 2:53:58 AM   
averen



Posts: 105
Joined: 8/31/2003
From: Austin, TX,
Status: offline 		Here's the setup I use for my CNC cutter...works rather well.

1 - 24V Transformer from Radio Shack (2 Amp rating with a center tap of 12V)
1 - 6A rectifier (CNC Cutter requires DC)
1 - 10mF 75V Filter Capacitor.

Transformer plugs directly into the wall, rectifier goes on the outputs with the capacitor running in parallel to smooth out the voltage.

Works awesome! When I'm cutting fast thewire moves at 4mm/second and I use 44% power to the bow which is 5' long.

If you don't need DC voltage you can get rid of the rectifier and the capacitor and get a lamp dimmer from home depot or where ever and plug the transformer into that...honestly I think I get more power going with DC. To give you an idea I just added the capacitor today. I had to turn down the temp on a 1.5mm/s cut (used to be 50%) down to 24%!!! That's pretty impressive...means the bow is getting twice as hot while leaving everything the same except for the Capacitor!

Anyways, just my $2.20 (adjusted for inflation)
Averen

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RE: Stainless Steel Cutting Wire - 2/20/2004 3:56:50 AM   
arx_n_sparx


 

Posts: 45
Joined: 2/9/2004
From: Burlington, ON,
Status: offline 		WHOA!!!! Back that train up!!!!

There are NO advantages to using DC over AC. The bridge rectifier does rob a wee bit of power (0.7 volts to overcome the depletion zone of the diodes), but the capacitor that "smooths" out the wave form is robbing from Peter to pay Paul. I don't know why BinkDaddy is getting more power, unless he's using a 10uF capacitor (microfarads), and it's (the capacitor) helping to drive the output. Maybe I should say "overdriving". Bink - I hope you have a whole bunch of ventilation holes to disperse the heat generated inside of your power supply......Adding the rectifier and cap is just adding stuff you don't need, unless you don't have the power in the first place. If you DO have the neccessary power, I would NOT add the bridge/cap, as it's unneccessary.

Brad

(in reply to averen)
       Post #: 11

RE: Stainless Steel Cutting Wire - 2/20/2004 4:21:54 AM   
averen



Posts: 105
Joined: 8/31/2003
From: Austin, TX,
Status: offline 		arx_n_sparx - I think your reply was directed towards me

Like I said I'm using DC because I have to for my CNC cutter (if I use AC the PC won't control the wire temp)...there probably aren't any advantages to it...

The 10mF (millifarad or 10,000 microfarad) capacitor is in place to provide a smooth DC input for the CNC controller for the bow power.

As far as the "advantages" I'm just going off of what I've experienced. I haven't noticed any advantages or disadvantages from 24VAC to 24VDC. Although with the capacitor in place I have noticed a MAJOR difference between the the 24VDC before and after the Capacitor...the 24VDC after the cap is probably comparable to the 24VAC.

Ventilation holes? Nope...the setup doesn't get hot at all...the rectifier gets a little warm...but nothing to be concerned about. The ballast resistors for my CNC motors get MUCH hotter than any one part of the bow system...but that's what they're designed to do...dissipate power

Binkdaddy - I'm interested in this carbon steel that you're using. How does it compare to nichrome? What kind of tensile strength is it? What about the kerf?

Averen

< Message edited by averen -- 2/20/2004 4:22:12 AM >

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RE: Stainless Steel Cutting Wire - 2/20/2004 4:29:00 AM   
arx_n_sparx


 

Posts: 45
Joined: 2/9/2004
From: Burlington, ON,
Status: offline 		A note on power used:

I have my PS set at just under 1/2 power (about 11:30 on the dial ) using this http://www.nsrca.org/technical/tip_tricks/foam_cutter/foam_cutting_power_supply.htm My cuts are NOT fast - typically about 5 inches per minute. Slow cuts are nicer cuts, and my kerf (the width of the cut) is small. I have a 4 1/2 foot bow, so we are not talking a wee one. I haven't tried a smaller bow yet, but I know less power will be needed. I haven't measured the resistance (ohms) of the wire, because it's a bogus number while cold - as soon as you put some current on it, the resistance will change (higher). I haven't measured the current either, as it won't be an RMS value, and I don't think my DVM can figure out "true current". I do know the voltage drop reads 14V across the bow, but again, it's not a true sine wave, so that number is subjective.

So, to put it into laymans terms: Try it on some scrap foam, and find out what works for you! (hey, you thought I'd be able to give precise #'s? Think again!) It really is a bit of an art, and it's up to you to find just works best for YOUR rig. I had a problem at the start where the wire would literally oscillate up and down (I could see the wire twisting and untwisting as well) creating ripples in the cut. This meant (and I had to ask other people in that *other* forum) that I was cutting too fast/using too much feed speed.

Just try your rig, and if you have problems, try posting in foamies "Help, my foam cutter is doing XXXXX! - How do I solve this?" I know i had to take as much friction out of the cutter I use as I could (My cutter just makes my own fan fold in whatever thickness I want, I don't cut "foils" with it). I had my probs at first, and the guys quickly jumped in to solve it for me.

I guess I'm humble enough to ask advice when I need it. You've asked your question, so obviously you are humble enough too. You might get lucky and not need to ask again, but it's very reassuring to know that if you have a roblem, the folks here are quite willing to pitch in and help you solve it. I know I'm very grateful to TONS of people, and the only way I can "share the joy" is to put back as much into these forums as I take out - if not more.

I love the net.......

Brad

(in reply to arx_n_sparx)
       Post #: 13

RE: Stainless Steel Cutting Wire - 2/20/2004 4:33:55 AM