Machine Side View

After using many other foam core cutting machines including the string and pulley type used on the Feather Cut machine, I decided to build a machine that uses a positive linkage system to rotate the bow as it cuts thru the foam. This linkage system eliminates the flimsily strings and pulleys used on many other machines.

When cutting tapered wing cores it is very important that the hot cutting wire enter the foam blank parallel to the trailing edge of the foam and exit the foam parallel to the leading edge. For this to happen, the bow that supports the hot cutting wire must rotate as it travels thru the foam.

 This machine uses a 4-bar linkage system to rotate the bow as the hot cutting wire cuts thru the foam. When the two long links are parallel the bow moves in a straight line. This setup would be used for wings that have parallel leading and trailing edges - no taper.

When the long links are not parallel, the bow will rotate in an arc. To adjust the amount the bow rotates loosen the two thumbscrews and slide the fitting along the angle support (see the the upper left picture). To adjust the starting angle of the bow, loosen the two thumbscrews on top of the fitting and rotate the bow until it is lined up with the edge of the foam. 

Templates are used to support the hot cutting wire as it travels thru the foam. The wire follows the template to cut the exact airfoil shape. One set for the root and one set for the tip. The foam core is cut in two passes. First, the templates that define the lower airfoil shape are pinned to the ends of the foam and power supply is turned on. The machine cuts the lower airfoil surface. The lower templates are removed and the upper templates are pinned in place using the same holes. The machine then cuts the upper surface. The entire cutting process takes less than 30 seconds.