Thursday, 30 January 2014

DIY - Handheld Hotwire Cutter

I thought I would share my experiences sourcing parts for the new Handheld Hotwire Cutter I have just completed.  Previously I used wire from a TV coil hooked up to various car battery chargers that had a factory set current output.  These worked occasionally but you never had much control of the wire temperature. 

Hotwire Foam Cutter
After scouring the pages of ebay I came across a neat little hot wire power supply from Australia. There were 2 options for maximum wire length(when used with the recommended nichrome wire) of 1m and 1.5m and the unit ended up costing around $100.  I went for the 1m version as I will only be cutting the short side of full EPS blocks and I didn't want wires burning out when cutting thinner material.

Hotwire Power Supply
The unit weighs next to nothing and is quite compact so I mounted it to the hotwire bow for ease of adjustment. You can get optional wire with the banana connectors on request.

Hotwire Termination
Mounting of the wire is achieved by looping it around a bolt in between 2 washers, a wingnut is then tightened to clamp the wire between the washers.  The end of the wire hangs out for easy connection to the power supply.

Hotwire Bow Spring Tensioner
The wire lengthens when heated so one end of the bow pivots on a socket head cap screw.  An old trampoline spring maintains the required spring tension.  Folded 50x3 aluminium flat bar is folded to form the opposite fixed connection as well as the hinge seen above.  Scraps of 45x35(?) pine were used for the arms but these might be upgraded to CF roll wrap tube when I have more time.

Freshly cut EPS without sanding...
This is the first board(HD Creeper 48) cut with the hotwire and the above foam is straight off the wire with no sanding whatsoever.

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