In this Diwali season people have been buying new appliances. My neighbour had bought a washing machine and was throwing the foam packing. I found the foam to be of a good quality and so picked it up. However it was in a shape and size not useful for aeromodelling. So sat down to building a hot wire foam cutter. "Maidened" the cutter today.

Working video will be uploaded shortly once I get a volunteer to manage the camera.

The cutting table was built starting with a rectangular piece of 6mm plywood. The edges were strengthened by attaching strips of 18mm ply (From scrap lying with me). I made a slot for a fan regulator at one end which will serve as a temp controller for the cutting wire.

The vertical arm is a piece of 18mm ply which was screwed in the centre of one edge. The height of the vertical arm is about 12 inches.

 Took another similar piece and attached a brass terminal (taken from an old electrical swich). This would serve as the connector for the hot wire. Any simple screw would have done the job also. This piece is not rigidly mounted on the vertical arm but mounted using two aluminum brackets (cut out from an aluminum L Channel). The brackets were attached at about one third of the length of this horizontal arm.

The horizontal arm brackets were tightened on the top of the vertical arm. The two are attached so that the horizintal arm can move a bit. A spring was attached to the shorter end of this arm and the spring was attached to the vertical arm. This would keep the hot wire tight even when it expands on heating.

Drilled a hole in the cutting table just below the terminal that was attached to the horizontal arm so that the cutting wire remains vertical. Attached a piece of ply with a brass bolt to serve as the lower terminal under the hole of the cutting table. Attached a 28guage nichrome wire (available on ebay) between this terminal and the terminal mounted on the upper horizontal arm. Care was taken that after installation the nichrome wire was at 90 degrees to the cutting table surface.

Next step was to make a movable fence so that cutting straight pieces becomes easy. The fence is a L shaped aluminum channel to which two pieces of ply strips have been attached at 90 degrees. At one end a T nut was embedded in the ply strip which would help in tightening a bolt so that the fence does not move while cutting.

The electrical connections were made as per circiut diagram shown below.

Ashok everything perfect only the fan regulator at inconvenient position .... its ok if you are left handed.

The  fan regulator need not be fiddled with normally. Once set,  the power is switched on and off using the switch. But yes, position can be anywhere to suit one's convenience.

As a trial project, made a carry box for my RC Radio by cutting the foam that came with the radio to an appropriate size. The lid was attached using tape. Later I plan to make an outer box out of coro and attach a strap for carrying.

Super Cool Jig Sir  .

Mr Baijal... superb and 

regards
sujju

Spectacular, Ashok-ji! 

It's practically a fret saw!

Thanks for the appreciation Col., Sujju and Sanjayji.

Can you start a DIY series on this forum for projects related toRC/Aeromodelling?
Like your dozens of articles in Electronics For You 40 years ago?

Suggestions for initial articles:
1. Tools you have collected over the years
2. Tools/jigs you have built
3. A brief summary of your past/present models

@Iyer
Thanks for your suggestion. The current generation believes in quick solutions. It is the age of ARFs and multirotors and high end electronic stabilizers. Who has the time or interest in DIY and scratch building?

great build,

But i heard the foam cutter should be used near the windows as the fumes are extremely hazardous.

this one is being demonstrated right in the middle of the room.

Please take care

What is  the heating element ? Tungsten  ?

The fan regulator should be adjusted so that the wire is just hot enough to slice through and not burn the foam. If you increase the temp then you can smell the fumes but at the right temp, I could not smell any fumes or smoke. Even in the video you can see that there is no smoke. It is always advisable to keep the temp low for smooth cuts. But your suggestion taken. I shifted the cutter to my dining room just for the video. There was ample cross flow of fresh air into and out of the room (open doors not visible). My workshop is not wide enough for filming.

Heating element is 28 guage nichrome wire ordered on eBay.in

Heating element is Nichrome ! Got it from your description ! Awesome build and description sir !
 
If the fume is so dangerous . Usage of a fan can solve that ! A vacuum like arrangement to suck the fumes produced !

I was referring to the fan regulator on the foam cutter and not the fan in the room    ;DD  >

Huh ! I mean you can add an additional fan ( a cpu fan is enough i think ) to redirect the fume generated

The CPU fan may not work as it can extract air only from a closed space like a power supply or a computer cabinet. If fumes is a problem, the fence (the vertical aluminum guide) has to be modified so that a vacuum  cleaner can be attached to extract fumes at the cutting point. Such an arrangement is used on router tables to extract sawdust. Better to avoid excessive fumes by adjusting the cutting temp to the barest minimum as the extraction arrangement will be complex.

Just got an idea! Cover the underside of the cutting table and made a number of holes near the cutting point. Attach a vacuum cleaner to this enclosure and it will draw air and fumes from the table surface. Ensure that the vacuum cleaner air outlet throws air out of the room

Vacuum cleaner Sounds great