A Hot Wire Cutter

G`day Folks,

I took the plunge the other day and decided to have a crack at building my own hot wire cutter. The well known brand we are familiar with, sells in Oz for an average price of $ 60.00. Replacement wire for the same product can come in around $ 8.00 for about 4 feet in length. This is not a lot of money by today`s standards, however there is a lot of info on the net on how to build these devices, so I thought it was worth a go.

My first attempt was a rather crude model, however it worked really well and that lead me to thoughts on improving the design and making a more efficient build that most of us would be capable of completing.

Here`s my first attempt......40 x 20mm timber, coat hanger wire, and an E string from an acoustic guitar.



The above device is powered from a controllable transformer as used for DC trains.

So I thought on how to improve this model and came up with a design which uses electrical conduit to create the bow that will carry the wire. The wire has also been upgraded to Nichrome wire, which is resistance wire, however the E string works just as well.



So I purchased the materials required to make at least two cutters, one long and one short, however there is enough conduit left to make six more.

Conduit

4 metre length 20mm conduit + 4 x 20mm end plugs + 4 x 20mm elbow joints + 4 x 20mm straight joiners.......came to a grand total of $ 8.40

Electrical

4 alligator clips + 4 metres of RES80 0.32mm Nichrome Wire ......came to $ 7.95.

I already have spare transformer power supplies and I`ve got enough electrical wire to tie up the Queen Mary, so no need for any further expense, as the costs are getting away from us and we`re already over $16.00.....

Below are the power supplies.

The Cyclops has one controlled 12vdc output and two uncontrolled.



Playart.....one controlled 12vdc output and one uncontrolled



And this wall plug transformer uncontrolled 12vdc @ 1000ma......actually puts out too much power. The controllable transformers are better.



The parts ...left to right....Nichrome Wire...Alligator Clips...End Plugs...Straight Joiner...Elbow Joiner



And the conduit



Now the method I am using is extremely simple. The conduit parts are such a good fit that they will stay together using friction alone. They have to be pushed together quite firmly and twisted into place, but they are quite secure once this is done. If you are concerned about this method, there is also a glue available specifically for joining conduit, so I leave that choice up to you. I prefer the ability to be able to dismantle one of these if I need to for repairs.

I want a cutter that can reach a good way into a sheet of polystyrene so the first cutter has arms that are approx. 300mm long. Two of these are required.



The connecting piece does not have to be as big so this one comes in at 100 mm



Once you have cut these pieces, make sure you clean up the ends and remove any ragged pieces with sandpaper or a knife. It`s essential to have them smooth so that they fit well into the fittings.



The wire will be fed into the conduits via a hole in one of the elbows. Drill this big enough to give some play in the wire and the wire will feed through easily.



I am using speaker wire which can be divided in two.



Feed the wire in through the hole in the elbow. Divide the wires and lay the parts out to ascertain how much wire you need for each arm. Obviously one length of wire will be shorter than the other.



Where your wires divide, tie a knot so that the wire cannot pull back through the hole in the elbow.



Now pull the knot back to the hole.



Feed the wires through the other parts and assemble them in series as you go along



Fit the straight joiners onto the ends of the arms. These are required to allow fitting the end plugs. That is their only purpose.



The end plugs will be drilled to allow fitting of small bolts to hold the Nichrome wire.





The bolts should be prepared by filing the head flat and two flat faces on the sides. Filing the head gives a good surface to solder to and the flat faces allow the head to be held securely whilst securing nuts are being tightened.



Trim the wires at the end of the arms....leave about 50mm for ease of handling.



Solder the heads of the bolts. If you find this difficult, you could add terminal clips to the ends of the wires instead and use the bolt to clamp them tight.



Solder the ends of the wires from the ends of the arms to the bolt heads.



Push the bolts into the end caps



And secure with a flat washer, spring washer and nut. Then add two flat washers, a spring washer and a nut, these will secure the wire.



Push the end caps flush into the ends of the arms. Them measure out and cut a length of Nichrome wire. Make it long enough to wrap around the bolts a couple of times.



Secure at one end first by placing the wire between the two flat washers and wrap around the bolt a couple of times and then tighten the outside nut. When adding wire to the second arm, add a slight bit of tension into the wire by bending the arm ever so slightly. The wire will cut by heat, so the tension is merely to keep the wire straight.



Solder the other ends of the wires to the alligator clips





Now it`s time for testing, however one should remember when using this tool that we a re dealing with a hot wire fed from a transformer connected to the mains. Extreme care must be exercised and the tool should be turned off and disconnected when not in use. Stay away from flammable materials and explosive gases etc. Don`t leave the tool on for extended periods as it may overheat the transformer. Allow the tool to cool down before you store it. Don`t touch the wire when the tool is on...it will burn you. When cutting foam / polystyrene, toxic fumes may be released, so work in a well ventilated area.

Hot Wire Cutter



So folks, it seems to work as it should, so I knocked up the small version as well. The small one has 100mm long arms, which should be handy for shaping and working some small areas of the polystyrene.



OK folks, I hope that has helped anyone considering making one of these. There is also a lot of information on the net and various methods on making similar models, so whatever you need to know will be out there somewhere.

I am happy to answer questions if you have any.??

http://www.clickGormo

 

Thanks guys,

Marty......no worries.....just returning the favour.....you`ve helped me out in the past......

http://www.clickGormo........PS....Bunnings only seem to have the conduit in 4 metre lengths, but as it only costs $ 2.99 for the 4 metres, it`s not worth worrying about. If you get some from Bunnings, take a small hand saw with you so that you can cut it in half to get it into your car.