The design of this foam cutter requires the use of an AC power transformer with a separate 120 VAC primary and a 24 VAC secondary winding in order to eliminate a potential shock hazard from the aluminum supports.
All measurements are approximate and non critical.
1.) The center support of the foam cutter is made from a scrap piece of 3in x 28in x 1in length of poplar wood.
2.) The side supports are made from a 18in x 1in x 0.125in length of aluminum angle.
3.) The rope used to tension the nichrome wire is a 60in length of nylon clothes line. A wood chopstick is used to apply tension to the cord. Note: The tension cord must be made of non-conductive material.
4.) The cutting wire is made from a 28in length of 27 awg nichrome wire.
5.) The black and white wire connections from the aluminum supports to the terminal block can be 16 or 14 awg TFFN stranded wire.
6.) Miscellaneous components include 16 awg #6 or #8 ring terminals, a two position terminal block, two small S hooks and some #6 and #8 machine screws and nuts.
7.) Power cable between transformer and foam cutter can be either separate 14 awg wires or a 14 awg two or three conductor cable.
8.) Power supply components consist of a 24 VAC transformer (Stancor P-8618) rated at 4 amps and a 0-130 VAC Variac transformer rated at 5A.
Note: Since most Variacs are NOT line isolated, a separate 24 VAC transformer is required to power the foam cutter.
The aluminum support bars are spaced a nominal 24in apart and are attached to the poplar board with #8 machine screws.
Note: The aluminum bars also serve as electrical conductors to the nichrome wire.
The nichrome wire is looped several times through a nickel plated ring terminal and tightly crimped to the wire and attached to the aluminum bar with #6 machine screws and nuts.
Each aluminum bar is connected to the terminal block with a 16 awg wire using a 16 awg ring or spade terminal on each end.
The connection between the 24 VAC transformer and foam cutter is made with a length of 14 awg three conductor SJOOW power cable.
Finally, I added a two inch section of aluminum channel to the poplar wood support to allow me to clamp the foam cutter to my table saw in order to make long straight cuts using the table saw fence.
Using the table saw fence I have been able to cut strips of two inch styrofoam one tenth of an inch thick (0.1in).
Foam Cutter Voltage and Current Measurements
|VARIAC OUTPUT||XFRMR OUTPUT||WIRE CURRENT|
|36 VAC||7 VAC||1.0 A|
|54 VAC||11 VAC||1.5 A|
|73 VAC||15 VAC||2.0 A|
|90 VAC||18 VAC||2.5 A|
|108 VAC||22 VAC||3.0 A|