Lap welds are recommended for thin sheets of plastic – 1/16 inch or less. The principal requirement
in making a lap weld is to be sure the faces of the sheets forming the lap are thoroughly clean before
joining them together in a lap weld. The lap of one sheet over the other should be at least 3/8 of an inch
to insure a good lap-weld bond. No welding rod is used. The overlapping areas are fused together by
using a flat tip with following pressure.
The rosette weld is a modification of the lap weld. It is used primarily for joining two layers of plastic. In
preparation for this weld, alternate holes are drilled in each sheet and the welding takes place inside
these holes. The diameter of each hole, and the spacing between holes, is at least three times the
thickness of the plastic sheet. Using welding rod whose diameter is slightly less than the thickness of the
stock, the operator makes a spiral weld that secures the bottom sheet to the one that is lapping over it;
the spiral weld is continued until the hole is filled and both sheets are joined. The procedure is repeated
for each hole.