Foam cutting with your charger

Concept

This is a quick tip. I've read many tutorials on the web about how to create power supplies for foam cutting. Using ATX power supplies or building your own with heat control from basic electronic parts.

Most of us already have a charger. The Turnigy accucel-6 chargers (and many other programmable chargers) don't have a program for foam cutting like the icharger products but they can do the same. 

The power supply connection

First get the correct wire that will melt foam. What you need is nichrome wire, the finer the better (as long as it holds up). You can use other types of wire but they won't work as good as nichrome wire.

The easiest way to get your charger leads on that wire is to use crocodile type connectors. In fact the accucel 6 charger comes with 2 sets. 1 for input (keep those for charging from battery terminals) and 1 for output. That one I've never used so far. I just replaced the yellow connector with two plugs I bought at the LHS. 

I used some 14 awg wire from hobbyking in between (it's cheap an very flexible). You'll need to have at least 1m each to work on a 1m50 wing span. You need some extra to be able to work with the wires freely.

The construction

It's important to have enough tension on the wire. Otherwise your cut won't be straight. The 2 most common systems for foam cutting are the bow and the fixed point table setup. 

For a bow you need 3 pieces of wood and 2 pivoting points configured as a H. On top goes a spring or rubber forcing the 2 sides together. Below goes the nichrome wire for cutting. 

An alternative is the fixed point table setup. For this you need to have a fixed point on a table where the cutting wire is connected on. On the other side you can put a handle to keep tension on the wire yourself. You can touch all the wire except for the part that is between the connectors.

Start melting some foam

Connect this up with your charger and select the NiCd CHARGE program. You can select the current before you press start. How much current you need depends on the length of your wire. 2A is a good point to start with. The wire should be glowing just a little bit. Don't have it glowing up hot red or it will burn too fast through the foam. Try it out on some leftovers. Remember to always keep tension on the wire while cutting so that it goes straight.

For some reason my charger dropped from 10V to 0V 2 times when I started and only then gives 10V continuously. Not sure if this is related to my setup or this can be programmed or not. Let me know if someone has a solution for this. If the wire gets disconnected you'll get a connection error on the charger. 

For the profile you can use a guide on one side. I tried with balsa today but it's better to have harder wood or metal or plastic that doesn't melt too fast. The balsa was burning if I got stuck. Also make sure it's smooth so you don't get blocked by the template. It should all be done in one smooth movement.

Good luck with the cutting!