Anyone made their own hot wire cutter before and know how to calculate how much power is needed?

Three failed attempts now using different thickness of Nichrome Wire. Thinnest I got was 32SWG (0.2743mm) off ebay and its the thinest I found.

I need it to cut foam at 60mm in length and have a 3xD power pack. Anyone know if 4xD battery will work or am I trying to achieve something that needs much more power?

So if I reduce the length of the wire, it will heat up and cut fine, but not when its 60mm in length.

Well... as I couldn't come up with a working solution, I took a friend's advice and bought a Bench Power Supply from Maplins. Set me back £35, but its got nice length crocodile clips and a variable power output. However I had to ramp it up to max 12v before the 32SWG Nichrome wire at 60cm length was hot enough to cut the foam.