HK100 hot knife cutter is a great product that cuts foam very fast. Very easy to use and maneuver. I used it on 1inch styrofoam and this cut through it like butter. Just use it in a well ventilated area because not sure how good the fumes from melted styrofoam can be for your health
Tip for consumers: Different hot knife with different specifications of the blade. There are two types of voltage for hot knives, choose according to the voltage standard of your country