giantflier

Hi guys,

Could somebody suggest what kind of transformer better to use for cutting styrofoam? What wire? Where to get it?
I need to cut thin sheets for sandwish laminate. And by the way what foam is the best for it today?

Thank you.

PAINLESS

My Feedback: (19)

The power supply is called a Variac. Mine goes from 0 to 140 volts. I typically use about 23 volts for cutting white styrofoam.
Nichrome wire is best but hard to find, SIG use to sell it in 5 foot lengths but I haven't tried buying any in a few years. Some people use stainless steel fishing leader.
I have some .005 diameter tungsten wire I'm going to try next time I break the nichrome wire, it happens.
As far as foam, I use white 2" thick by 4'x8' purchased at Home Depot or Lowes for wings. The denser blue and pink stuff cuts well too, but needs a little higher voltage.
Don't try cutting with out a guide or pattern of some sort, it is impossible to free hand a straight line.

giantflier

Thanks!
Where can I get this Variac? At Home Depot? Is there any other device like this?

dreadnaut

My Feedback: (5)

Try www.mcmaster.com. I have also heard of guys using guitar strings. The high ''E'' strings come in varios diameters from around .009'' to .013''

This stuff is about twice the density of white foam. You will get a more rigid structure, but there is a weight penalty.

Ed Smith

I use an ordinary 10 amp. car battery charger.

Ed S

DMcQuinn

My Feedback: (13)

I got a 24 V transformer at radio shack and use a standard 110 volt "dimmer switch" on the input side of the transformer to make my heat adjustments. Works great. I have three cutting bows and I can cut all the way up to a 5 foot long cut.

giantflier

Could you please tell me more about this transformer? What is it exactly?

lrglnman

[link]http://www.radioshack.com/product/index.jsp?productId=2102703&cp=2032058.2032230.203 2277&parentPage=family[/link]
This is the one I use. I wire it up to get the full 25 volts across the nichrome wire and use a good quality dimmer switch for voltage control which controls the heat.

giantflier

That's so simple and so great! You are genius man. Thank you so much!

giantflier

Onother question

I got it all. I have transformer and dimmer. How to connect it?
Trans has two black wires on one side and two yellow and one black wire on other side.
Dimmer has four wires - black, red, yellow and red. I tryied to foloow the instruction which comes with dimmer and found that it's all Greek to me. I am not an expert in electricity to be honest.
Could you please tell me how exactly to wire these divices together to make it work?
Thank you.

Jim_Purcha

My Feedback: (8)

Check out this thread: http://www.rcuniverse.com/forum/m_49...tm.htm#4968914

giantflier

Thanks a lot! It helps.

drcrash

Check out this posting

http://www.rcgroups.com/forums/showp...8&postcount=22

from this thread over at RCG:

http://www.rcgroups.com/forums/showthread.php?t=628704

You want a 2-amp transformer or better, likely 4 or more amps. 12v is okay for a short- to medium- length bow. 24V is better. (See the above post for sources.) For long wires, you need more volts. For thicker wires, you need more amps. (And for long wires, you probably want thicker, too, or they'll break more often.)

Put it on a regular 600-watt light dimmer, or a router speed control from Harbor Freight ($25 regular price but often on sale for $10 or $15).

Use stainless wire. Stainless fishing leader wire is good and cheap. (Under $2 for a 30-foot piece, good for making several hot wires. You'll want extra because they break occasionally.) Nichrome breaks easily for hand cutting or gravity-fed cutting.

drcrash

Nichrome isn't better than stainless for hand- or gravity-fed cutting. It breaks easily. (It's good for radiant cuttting like most CNC cutting, where the wire moves at just the right speed and the foam vaporizes before the wire touches it.)

DON'T use guitar strings unless you have a very high-amp transformer or a very thin guitar string. A guitar string has about 1/5 the resistance of a stainless wire, or 1/7 the resistance of nichrome. It will draw a lot of amps if it's not extremely thin, and if it is extremely thin, it will likely break. So if you don't have a very high-amp transformer, stainless fishing leader is a better bet.

(A lot of people are under the impression that guitar strings are made of stainless steel. In general, they are not, and true stainless strings are hard to find, as well as being more expensive than fishing leader.)

Guitar strings can work if you understand the issues and have the right power supply, but by default, go with stainless.

giantflier

Thanks!

Jgear

My Feedback: (3)

Check this page out....

http://nsrca.org/technical/tip_trick...wer_supply.htm

Andrew

I use .018" stainless steel wire from [link=http://www.mcmaster.com]McMaster-Carr[/link], part no. 9495K62. $8.75 buys a 285' roll -- enough to last a long time. The cutter power supply shown on the NSRCA site will work, but the temperature control is a little course.

Flypaper 2

I use .020 piano wire and patterns made from Arborite.

giantflier

What is Arborite?

Flypaper 2

It's a composite countertop material that withstands the heat of the hot wire with no problems. It's about 1/32 in thick and very hard. I get in a scrap bin for modest cost from a local lumber business that installs kitchen counters. Can be cut with a bandsaw then filed and sanded smooth with progressively finer paper. the smoother it is the less chance of the wire catching on it and leaving a notch in the foam. Hope this helps.
Gord.

Mike Mangus

In the pursuit of trying to make something out of the junk in my shop, I came up with a radio controlled hot wire cutter.

It has a cheap 4 channel reciever, a 15 amp brushed motor speed control, and a 2 - 3 cell lipoly battery for power attached to the cutting bow. The speed control is connected to each end of the cutting wire. It normally uses around 10 - 15 amps to cut foam. I just plug in the battery, turn on the transmitter, and advance the throttle until the wire is moving smoothly through the foam.

Yeah, it's silly, but it cuts really nice and you never get a ripple in the foam from a power wire getting caught on something.