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« on: June 05, 2012, 01:24:55 PM »
robotics.pavanthegala
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Hi all needed help and.the materials needed to construction of hot wire foam cutter

Pavan Theegala
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« Reply #1 on: June 05, 2012, 01:47:54 PM »
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Pavan,

You PM'ed me on the same subject and I replied:

"First thing first you need to get yourself a step down that will convert 240V AC to 12 V DC output. The current rating of the output of at least 500mA to 1000mA.

Do a thorough search on the forum, you will find a lot of designs and inputs on hot wire cutters.

All the best!"


Have you done all that? Have you tried typing "Hot wire" or "hot wire foam cutter" in the search box located at the top right hand corner of this page and pressed the 'Search' button next to it?
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« Reply #2 on: June 05, 2012, 01:54:19 PM »
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I am about to build a hot wirefoam cutter. I have all the parts ready to go. Depending on which type you want will dictate what you need. Do you wish to build a bench/table type cutter or a hand held cutter. The hand held cutter is cheaper but not as versatile as a bench type. The hand held type requires a very steady hand but the bench type can be extremely accurate and gives a far more superior cut. Rather than go into details on both methods could you tell me which type you prefer please.

Remember, you can add a hand held cutter to the bench type very easily to give you both types.

Kind regards  Stuart
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« Reply #3 on: June 05, 2012, 02:06:36 PM »
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Hi Pavan, I made foam cutter recently, let me share the details with you.

1. Get heater coil from any electrical shop, it will be 15 or 20kw (I am confused about this unit). It will in a shape of coiled wire. Take a piece of this spring like and straighten it by stretching it over a wooden surface. Get it completely straighten.

2. Take a wood stick which can bend little bit like wooden beats used in plywood furniture. Make a bow kind of structure by tying both ends of stick with heater wire and stretch it so it will in a bow shape.

3. You need 12V DC 5AMPS power supply to connect to both ends of bow. If you have laptop, take 2 thin wires and insert into your laptops power adapter pin and secure them with some tape so they dose not come out. Connect both ends of wire to two your bow. You can use old computer SMPS also.

You will feel the wire heating up within 2-3 seconds and then it will be ready to use. It will cost you 20 bucks for heater coil, thats all it will take to make a hotwire foam cutter.

As VC Sir suggested there are at least 20 threads/posts here is Forum about making Hotwire Foam Cutter. Do search them you will get your answers.
 
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« Reply #4 on: June 05, 2012, 02:26:47 PM »
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Hi Pavan,

If you can wait I can take a lot of photographs of an excellent home made foam cutter on Sunday next. I will also get photographs of the planes we are building with this foam cutter. So far we have built 6 of the aircraft which are built to carry a large amount of video equipment. In fact we fitted a domestic hand held video camera to one and it carried it with ease. It is a slow flyer and in a steady wind of 5 miles per hour it will hover stationary for 5 minutes if need be.

It is a perfect beginners plane and the complete body was cut from ordinary cheap insulation type foam. The plans for the plane are available on the Internet but the foam cutter is one of a kind and will cut a 6 inch slab of foam into perfect sheets of any thickness you require. It can be adjusted to cut at any angle in a 170 degree arc. The build is so simple 3 of us are building copies of it. It can't be too hard to build as I will be building mine in bed, as I am disabled.

Kind regards Stuart
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« Reply #5 on: June 05, 2012, 02:39:22 PM »
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@ VC I am aware of how to setup the hot-wire cutter I am seeking about the type of to be used. Even the guage I was able to cut the foam, but in just 2 to 3 cuts the string broke Sad


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Regards,
Pavan Theegala,
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« Reply #6 on: June 05, 2012, 03:04:46 PM »
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One option that has worked well for me is the heater coil . You can get a replacement heater ( hot plate heater ) and straighten it out to the length you want and cut and keep the balance for a later date.
We regularly cut HD foam and have no problems with it.
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« Reply #7 on: June 05, 2012, 04:02:46 PM »
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By far the best wire is fishing tracer wire from any fishing store, the next is Nichrome. Followed by guitar string. Heater coil is rather thick, requirers higher current and tends to break easily. Maybe we tried the wrong wire but we are all using fishing trace wire and none of us have yet have one break even though we use extreme pressure to keep the wire dead straight. It needs to be so tight it sounds like a guitar string when plucked.

Regards  Stuart
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« Reply #8 on: June 05, 2012, 04:15:54 PM »
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Yep the Guitar wire is also good
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« Reply #9 on: June 05, 2012, 04:29:19 PM »
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Hi Stuart,
can you please post the plans of your hot wire cutter, specially the power supply segment. Am building a hot wire cutter myself and am stuck with the power supply......ritenow computer SMPS seems the only option possible....so I'd be glad to see your design.

Regards
Bilal
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« Reply #10 on: June 05, 2012, 04:48:44 PM »
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Bilal boss I would rather suggest not to use the computer SMPS if you plan on using SMPS again on the computer. As the load might short components in the SMPS.
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« Reply #11 on: June 05, 2012, 05:17:15 PM »
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Punty,
bang on mate, thats exactly what am worried for, though am using a 460W SMPS rated at 16amps on the 12V rail........so what to do, any suggestions?
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« Reply #12 on: June 05, 2012, 05:22:57 PM »
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Bilal mate if you check VC sir's post above.. He is suggesting to use a power down transformer, If you have access to some electronic store, you can easily get an adapter with 12V DC and good AMP. But the choice of power supply will also depend on the type of wire you use as the cutter wire and the length of the wire.
Basically we need to heat the wire to the extent so that it can cut the foam. These days there are adapters which have variable voltage and amps, offcourse within pre specified range. Hope this helps Smiley
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« Reply #13 on: June 05, 2012, 05:32:22 PM »
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Toshiba Laptop Power Adapter is what I used and it works great.
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« Reply #14 on: June 06, 2012, 07:28:34 AM »
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Hi Guys,

I'm afraid you would find my power supply rather expensive. It is 0 to 30 volts and 0 to 10 amps continuously variable. Retail price around $300.00

I built one for a friend which involved a cheap 240 volt AC to 12 volts AC  anything between 12 and 24 volts ac and 5 to 10 amps is OK. I then used an old light dimmer I had lying around but they can be purchased very cheaply at an electrical store. I wired the transformer to the dimmer and then to a light bulb We were using 12 voltsd so we bought a truck bulb and mount. With the bulb in line it was a simple matter to run the two cables to alligator clips which connected to either end of the cutting wire. Using the light dimmer allowed the AC to be adjusted so the foam wasn't burnt or not cut correctly due to low power leaving the wire too cold. Remeber to use a good wire throughout the system, if the wire is too thin it will begin to heat up as well but if it is too thick it becomes hard to handle.

Another system to use is the old computer power supply. The AT type All you need to do is cut all the wires from the big solder beds and leave nothing but an Earth (black wire) and a yellow ( 12 volts DC) wire plus the two wires running to the fan. The main switch could be part of the case which makes life easy or perhaps the main switch is attached to an insulated wire. Sometimes the attached switch can be uninsulated if this is the case then I suggest mounting it in the power supply case or simply leaving it switched on then wrap it it insulation tape and tuck it out of the way and use the wall switch to power up.

The more modern supplies become a little trickier and you need to short two wires out to activate the supply (usually the orange and grey wires) but this can differ in other units. Somebody with a multimeter will pinpoint which wires are used. Then some supplies require a small load be added to the supply to keep it operating. Again a friend with a multimeter and a some experience with power supplies can be of help.

I certainly don't encourage you to poke wires into laptop power supplies and taping them up especially if you have the matching laptop. If you can afford $49.00 Hobbyking sell an excellent power supply with dual outputs of 12 volts DC at 30 amps but you would need to add a DC variable control.

I've heard of car battery chargers being used, basically anything with a secondary voltage of 12 to 30 volts and a current of around 5 amps in more than enough. A word of warning, please don't be tempted to use a car battery or a lipo battery. These are extremely dangerous and car batteries can give off explosive gases and if a lipo is depleted below 3 volts it could burst into flames or just wreck the battery. If a friend says he has used a bad system for years and had no problems he is a very lucky person but shouldn't be copied.

By the way The best possible item to use to power a foam cutter is known as a Variac or Auto Transformer. The bigger the better. You can dial up virtually any voltage you wish and cut anthing from the smallest piece of foam to a piece 8 foot by 6 foot. Just turn the knob on top and away you go. The only thing to watch is to not wind it too high or your wire will burn or become a shock hazard. If I didn't own a variable power supply I would use my variac like a shot. Ask a local electrician he might have one collecting dust. They aren't used much these days.

As promised I will take photos of a home made system on the weekend. I would do it now but being disabled I need assistance to get around. My friends pick me up on Sunday.
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« Reply #15 on: December 20, 2012, 01:21:40 PM »
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Hi,
I want to ask one simple question:
Q: If we directly connect the nicrome wire b/w the two pole of dc circuit, isn't it is a type of short circuit.

Note:- I've few months ago tried to put the copper wire b/w the 24-0-24 Volts 2amps transformer. And transformer caught fire. i've connected the wire b/w 24-24 pole of the transformer.

help me as need serious help. i'm afraid is that hot wire really works
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« Reply #16 on: December 20, 2012, 01:35:55 PM »
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Hello AASTO,

read this.
http://www.rcindia.org/tools-materials-and-building-techniques/hot-wire-foam-cutter/msg106341/#msg106341

Also use a 6 volt 1 AMP  transformer for this use along with a fan regulator in primary coil of Transformer.
Yes, its a short circuit but nichrome is a high resistance wire which is why it generates heat.

If you use a 6V 1 amp transformer  with  a fan regulator u can control the temp of a 1-2 ft long wire. you would need a regulator in order to increase or decrease temp depending on the craft you are cutting.

any issue just use the above thread to post query.


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« Reply #17 on: December 20, 2012, 09:32:04 PM »
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Hi,
I want to ask one simple question:
Q: If we directly connect the nicrome wire b/w the two pole of dc circuit, isn't it is a type of short circuit.

Note:- I've few months ago tried to put the copper wire b/w the 24-0-24 Volts 2amps transformer. And transformer caught fire. i've connected the wire b/w 24-24 pole of the transformer.

help me as need serious help. i'm afraid is that hot wire really works
ofcourse u are in a way short circuiting, but the fact lies in that where the energy from potential drop goes.
basically the thing u have to be careful about is that u have to add sufficient RESISTANCE across the wire so that ur u heat ur wire instad of blowing ur battery/ transformer.

steps to avoid blow up.....(increase resistance)

1 Take care diameter of wire is sufficiently LESS (finest string of guitar sitar wire)
2 longer wire the better ..... u can easily titre temp as in :

reply 4

http://www.rcindia.org/tools-materials-and-building-techniques/hot-wire-foam-cutter-build-help/msg119652/#msg119652
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« Reply #18 on: December 21, 2012, 09:08:23 AM »
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Hey,
guiter or siter wire may cut while hot and cannot take so much tensile streng during hot condition like nichrome wire for this. You can slowly open up any 10 watt - 40 watt soldering wire and can use. Or can purchase 36/40 SWG Nicrome wire. I have some of them. If anyone interested, I can send this.
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« Reply #19 on: December 21, 2012, 10:27:06 AM »
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what should be value of resistance, and Is it okay to use laptop power adaptor as power source? is it safe? tell me for how much time we have to keep the hot wire foam cutter device on? if any one have safety schematic circuit diagram for to make the hot wire foam cutter then please post the diagram. Can we use diode to protect the backflow of current in the circuit.

Note:- I've already blown-up one transformer a moth ago for trying to make hot wire foam cutter. so i want a hot wire foam cutting technique to be safe and give me realistic data. don't say you can add resistance. tell me the value and how it should be added. I've joined forum to change the way people use to post information. I've joined and posted the problem so their answer should be clean enough that can be used by any other guy in similar situation.
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« Reply #20 on: December 21, 2012, 10:35:49 AM »
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think you have not gone through this....

http://www.rcindia.org/tools-materials-and-building-techniques/hot-wire-foam-cutter/msg106341/#msg106341

for cutting properly...
1. try on scrap piece
2. on hot wire use the fan regulator to see the optimum temp to cut
3. once satisfied switch off
4. Start working on actual craft switch on and off immediately.... since there is no time required to heat the wire.
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