AUTOMATIC HOT-WIRE FOAM CUTTING MACHINE

Gene Sandburg

The Auto-Foam Cutter is shown in the schematic drawing above. It shows a tapered wing section about to be cut. The advantage of this device is. that the resulting section has an extremely smooth finish requiring very little sanding and filling. This saves many hours of work, dollars and pounds off the finished aircraft.

The foam cutter works like this; the templates are fastened to the ends of the foam block. They are made with ramps (extensions) ahead and behind the required contour. These are for the wire to rest on and be guided to the start of the cut and the support the wire after the cut. The templates work best if they are made of metal and insulated from the foam by a space. The foam is weighted down during the cutting to hold it flat and in place.

The wire is pulled through the foam by means of weighed lever arm (see the above diagram). A wire hook is attached to the hot wire outboard and just adjacent to each of the two templates. Dacron fishing line is tied to the hooks, threaded around the pulleys and attached to their appropriate templates on the lever arm. The distance the line is pulled during the inscribed arch of the lever arm, at the line attachment point, must equal the length of the template.

Dacron fishing line is used to minimise the line stretch to insure an even cut. To obtain the best cut use the minimum allowable heat on the wire. and the minimum allowable weight on the lever arm. This provides a slow smooth cut.