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Oct 15, 2018, 12:50 PM
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Polystyrene Foam Cutter


I have improved my polystyrene foam cutter. The cost to build was about $10. Using household tools, a drill, soldering iron and glue gun it was complete in a couple of hours. The size accommodates polystyrene foam up to 1" thick. It is portable, powered by 2 alkaline D cell batteries. 3 inches of very thin steel wire is heated by resistance to just beyond the temperature polystyrene transitions. Polystyrene is safely cut in a ventilated area. The heat is minimized to avoid unhealthy fumes. As a result, cutting speed is more or less 9 inches per minute depending on the size and density of the PS. The cut is barely larger than the diameter of the resistance wire so detailed and accurately sized pieces and voids can be achieved. It also cuts thin molded PS (recycling symbol 6). The platform lifts off to change the batteries or resistance wire.
Resembling a pizza box, a 12" square frame made of 1.5" x .5" poplar with a .25" paper board top and bottom. The lumber was cut with a small hand saw. The top board is left unattached and small blocks are glued to the underside which keeps the top in position on the frame.
A light steel rod is bent at a right angle. One end of the rod is fitted into a hole in the frame and held with a set screw. The point of the screw tip is ground off. The arm is parallel to the surface at 2" above. The negative battery wire (22 AWG) is inconspicuously soldered to the rod using a heavy soldering iron. The resistance wire is very thin steel utility wire cleaned with emery paper. It is wrapped around a notch at the far end of the rod. Also, the wire is quickly detached and threaded through a hole made in the polystyrene for an inside cut.
A third of the 3" hot wire extends down through the hole in the platform. A small block of wood supports a screw which transitions from the steel hot wire to the positive lead wire connector inside the box. An on/off switch is wired between the screw and the battery positive. The switch is mounted though a hole in the back. The battery connector/holder is made of unpainted steel cut from a coffee can bottom.
The cutter is tested as 4.5W and an alkaline D cell is rated at 8 watt hours. In other words, the cell voltage will drop from 1.56V to 1.46V in about 15 minutes. Below 1.46V, the wire won't reach the desired temperature range. For reasons not explained here, more capacity is needed. A second D cell is connected in parallel. Connecting D cells in parallel was a common practice a long time ago.
The cutter had been used for 10 minutes at a time over a few days for a total of 2 hours. The batteries were down from 1.56V to 1.46V (resting). They are far from exhausted and could be used in another device. An alternative is to substitute the alkaline batteries with the constant output from a power supply.
Last edited by blitzen; Oct 22, 2018 at 12:37 PM.
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Oct 15, 2018, 02:16 PM
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Thank you for taking the time to post this!

Chris.
Oct 16, 2018, 08:56 PM
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Originally Posted by iluvtoflyrc
Thank you for taking the time to post this!

Chris.
Thank you for the comment.
Oct 17, 2018, 10:30 PM
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Nasa Delta Wing Glider


Here is a plan to start with. https://www.nasa.gov/pdf/205703main_...ing_Glider.pdf
I printed the template at 75% so it would fit on two smaller food trays. The patterns were cut with scissors and taped to the foam


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