can i use a emergency light battery for hot wire cutter?
specs.
6v 4.0h
suncapak batt.
pls.

Noooooooooooooooooooooooooooo
4 amp will be very high................ and 6 volt will be very less to heat the wire...

Sandeep

i have the thinnest guitar string for the cutter which is note E maybe

A 4 Ah battery does not mean it will provide 4Amps, It can discharge in almost 10~20 seconds in short circuit condition and destroy the battery. It depends on the resistance of the wire.

Nah.. emergency light battery will not be enough i think.. but then if u already have it, why not give it a shot? might work for a small string.. and i tested the e / no.1 string (thinnest).. and it was about 0.5 ohm per inch..

so for a 30inch string.. 15ohms.. V=IR therefore I=V/R or 6/15 in your case i.e. 0.4 Amps.. I don't think 0.4A will be sufficient to cut.. My string was 0.5 ohm per inch.. yours might be different..

I am uploading some pages from RCSD Nov 2008 Magazine for all who are interested in foam core cutting.
" http://www.mediafire.com/?ji9a9h1b945r888 "

Surprised that Rao Garu has not added to this thread. He is a past master at the art of foam cutting and hot wire bows. Rao Garu, please help............

With 6V you can heat  max 60 to 70cm of nichrome wire to desired temp to cut foam. if the nichrome wire is longer it will not heat up to desired temp to make a sustained cut. Voltage is directly proportional to the length of the nichrome wire which can be used. 

Dear VC,

I am unable to attach the Foam Cutter setup to PM.So I am posting it here.

Rao

Rao Garu, thanks a lot. This is exactly what I wanted.

Sir,
Could you please explain, why do we need Fan Regulator?
Regards,
Dileep

To adjust the current and hence the heat..

A variable adapter can also be used for this purpose, thats what I had been using, and it serves many purposes too...a handy little electronic box.

Guys pls post some pics of ur hot wire cutter..

I just tested my cutter.. The way the wire cuts through the thermocol is awesome!  I used a 12v 5A transformer and a old regulator that my electrician gave me for free.. Tried the thinnest (1 or e) and second thinnest (2 or B) guitar strings.. Although it cut through the thermocol, it was too slow for my satisfaction even though the regulator was turned all the way up.. So then we tried with a shorter segment of the 2nd wire.. It cut quite fast, so we realised that the strings have too much resistance and so we'll have to use thicker strings for a longer cutting bow.. Cant use thicker guitar strings as they have a coiled wire covering them.. Will try with thicker violin strings day after tomorrow.. Will be posting pics and vids later tonight.. 

Sorry I couldn't post pics and vids as promised in the last post as I've lost my data cable.. Anyway, I managed to find a thicker single strand guitar string (No.3) and it still has too much resistance.. Can anybody tell me where I can buy some nichrome wire?

Something like the following with 1 Ohm/foot would be perfect for my application.. If I don't find it in India I'll have to resort to ordering it from ebay USA..
http://cgi.ebay.com/Resistance-heating-wire-Nichrome-22-awg-20ft-/170484606532?pt=LH_DefaultDomain_0

Just look in the topic "EPP SHEETS IN INDIA",they r selling nicrome wire..

I have sent a PM to them.. Lets see if they have a wire which I can use? Does anybody know any other source of nichrome wire similar to the one in the eBay link above? It would be really nice if someone could send me some.. Otherwise I'll have to purchase it from eBay USA which I don't want to as I'm thoroughly sick of waiting for stuff to arrive from far away places

I get my nichrome wire from our school physics lab
its also better than the one avaiable on ebay
has Diameter od 0.32mm
Specific resistance- 1.019 ohm/meter
 its the best wire i have come accross for foam cutters

Akky.. Any idea where I can buy that type of wire?

No idea medicineman ....i paid Rs 180 for the whole Role of wire
around 50 meters
i gave the money to our physics lab incharge

Medicineman!
why dont you try Furtado's?
you can get guitar strings there OR you can peel up a copper wire, which mas a approx. dia. of around <0.5 which should also work, I remember making a wire cutter like this during christmas for cutting thermocol!

Hi Dorwin, I've already tried the 1st 3 guitar strings but they don't heat up enough.. The other guitar strings are only available in the coiled form.. Violin strings are also coiled. Now will try some other musical instrument or copper wire..



Akky, could you buy some for me and ship it?

but how will you pay for it ,,,i dont have any bank account

No bank account?? Ok, just ask any of your friends/relatives with accounts.. Will transfer to them n then they can give you cash..

This is the nichron wire which i use

Just found this interesting site:

http://www.harikesh.com/FoamWing.htm

I had read that site long back and also sent PM to harikeshpk but no response..


Akky, pls buy me a roll of it too.. I'm desperate! I'll send you the money somehow.. Ask your friends if any of them have a account..

ok medicine man will try buy presently i am having my exams which will continue till 28...after that only i cant try..please bear with me...

No problem! I just finished my exams so I understand your pain.. Till then I'll try some other strings..

and please note the specific resistance of this wire is 3.84 ohm/meter.....the first value was wrong,
in comparison with guitar string which has more than 18 ohm/meter(approx)

Even I thought it was too low.. then I thought u might have typed meter instead of foot.. so i guess this one and the eBay one I posted are approximately the same value then.. Guitar strings have too much resistance for big cutting bows, they are fine for small one I guess.. But then they might work on a higher voltage supply.. Mine is just 12v

i use around 18 volts 2 amps...but with a regulator....but i dont preffer this hot wire cutter...anymore...

I have made my my hot wire cutter from Soldering Iron Coil.
Just bought an 35 watt soldering watt coil from your electrical shop. (I have purchased for Rs.6/- only)
Just unwind from the mica sheet. Please note that, dont use used coil as they become stiffer and the bending mark cannot be made straight.
Now some calculation :
As the coil is used with one diode in series,
Rated Current = Watt x 2 /V
and comes to about 300 mA.
Therefore, it is recomended to drive at 2/3 rd current i. e. 200mA.
Now make your Bow or tension making arrangement.
Fix the wire. Measure resistance of the desired wire.
Calculate required voltage for heating (IxR).
I found for my 14" Bow wire, 12 volt is sufficient.
As the current is low, you can use a 12-0-12 Volt 1/3 Amp with voltage doubler or tripler with 3300uF Capacotor & 1N4007 Diode as required for your cutter.
========================================================
Roughly the thumb rule is that use the multiple of 12 Volt per feet.
========================================================
The advantage for this cutter is that, as the heat per inch is very less, cutting are very accurate. Simultaniously, you can hold the wire during cutting and feel nothing but small heat (If ur sensation is very good). The disadvantage is that you can not cut very first.
========================================================
The Cuttings are be very nice and accurate.
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
Similarly you can use 250 Watt Heater Coil (Sometime you may not find.) The calculation will be similar but value would be different and you need 1Amp Supply.

Thanks

Could you please post your doubler or tripler circuit? Also post the pictures too

Regards,
Dileep

Akky,

Can you buy for me also.

i will send somebody to you he will collect and give you the money.

will try do so but only after my exams r over means next month

Here is the Voltage Doubler Circuit.

or rearranging,

 and a voltage tripler circuit is here.


Similarly you can add more stage and get higher voltage.
Please use the voltage rating of each Capacitor well below operating peak voltage (Use 25 Volt ).

DIY Foam cutter link:

http://epp540.com/index.php?option=com_content&task=view&id=89&Itemid=43

And here is my Bow Cutter.


runs with 12 volt. PS capable to deliver 5A but use only 200mA.
Thanks

Here is my cutter.. 12v 5A transformer.. Ceiling fan regulator.. Activa/dio side stand spring for tension & guitar string tightening mechanism to adjust tension..

Medicineman, your setup is quite the same as mine. Only difference is that in your case the bow moves and the foam is stationary and in my case it is the other way around as I  plan to slice 25mm blocks into 5 mm sheets to start with. I like the guitar wire tightening mechanism, but what is the problem if we don't use a dimmer / regulator and connect the transformer directly to the mains?

If later you decide to use say a wire with lower resistance, or a short segment of wire, then the wire overheats and breaks. With the regulator I can adjust the heat to the desired level..

Hi Guys,
 a simple Question.
  Can I use a variable power supply for a hot wire foam cutter ? 

come on Guys.

check this out
not mine though

http://www.submarineboat.com/hot_wire_cutter.htm

this one is way better
http://www.horrorseek.com/home/halloween/wolfstone/HalloweenTech/fotmak_MakingFoamTools.html

Dear guys

       Hotwire cutters:

     Use of Variac in the primary of a transformer is normally suitable. But I think use of Eelectronic Voltage Regulators (LM 317T) will be more economic ans very safe in handling electricity.  The mentioned IC is capable of handling1.2V to 37VDC at 5Amps.  You can vary the voltage to control the current flowing through the HOTWIRE,(ie. Temperature of the wire),for any SWG of Nichrome/Piano wire.

J A Vincent/Trichy

Thanks

Hey , Can i use Pc's UPS battery(12v) and electric guitar no 1.(thinnest) string for Hotwire thermocol cutter?

Hello All,
although enough info is present n this thread but still want to share my share of info....

Hand held bow cutter may do some jobs but real work can be done only by a plate form cutter.
See the snap....with this not only the precision cutting is possible but you can give aerofoil shape to wings, make thin sheets out of thick sheets.... that too with amazing precision....

the snaps are self explanatory it all depends what cut you want adjust the wire & regulator.
 I have cut sheets upto 1mm thickness ( no jokes).

things are pretty much same as required for Bow cutter you need a platform and an iron L shape.

Nichrome wire is the best and use a SPRING to have tension on the wire. the wire tends to elongate when hot so spring keeps the wire straight for accurate cut.

Use fan regulator on full for cutting thick sheets and reduce as you reduce the thickness.

Tip -  always test on scrap thermacol  before you actually cut the real part to understand what speed you will cut and at which fan speed you get best results.
It can cut Coro sheet also...!!!

Have a look on this thread of what i could do with such a wire cutter.... @ #32
http://www.rcindia.org/electric-planes/scratch-building-a-look-alike-of-axn-floater-or-fms-800-or-easystar/msg106180/#msg106180

> choose high density thermacol for crafting, fevicol is the best adhesive i know to stick thermacol & PLY.
> A coating of 50:50 ratio ( water & Fevicol) with tissue paper on thermacol surface gives extra strength.