Modern puzzles are mostly made of cardboard, which makes them cheaper and easier to make. The pattern of a jigsaw puzzle is a whole piece of fine art printed on the surface of cardboard before cutting. The content of the picture can be enlarged photography, painting, or other kinds of flat art. The mapped cardboard will be sent to a special stamping machine, which is equipped with a steel cutting tool set in a predetermined pattern. After being pressed by the machine, the cardboard will be cut into pieces by the cutting tool set. The process is similar to that of a graphic cookie, except that the jigsaw presses have a much higher impact. For a typical 1,000-piece jigsaw puzzle, for example, up to 700 tons of pressure are required to be generated during the operation of the machine tool in order for the tool bank on the die to fully cut through the cardboard. The die (printing plate) of the jigsaw puzzle is usually made of plywood and other plates. The mold maker first marks or burns grooves on the template according to the pattern of jigsaw pieces, and then inserts the one by one into the grooves to assemble the tool set. The tool set is also covered with a layer of elastic material, usually foam rubber, which is used to cardboard pieces out of the holes in the tool set after printing.
Pieces of jigsaw
There are various ways of cutting the joints of jigsaw pieces. Mainstream puzzles use a piece-edge style called fully interlocking. "Comprehensive interlocking" means that several adjacent pieces are connected together. If one of them is moved horizontally, all the connected pieces will slide in the same direction, and will not be discrete. Sometimes the pieces fit together so tightly that the whole piece can be picked up without unravelling.
A close look at the joints of the jigsaw puzzle
The interlocking of pieces is usually achieved by the convex and concave edges of the pieces, which is similar to the "mortise and tenon joint" in furniture making. The main body of the piece is A rectangle with the same size and form, assuming that the two pieces tightly connected to the left and right are respectively A and B. If there is A convex A extending to the right on the right edge of the piece A, then the left edge of the piece B must have a sag B in the shape of A, and in order to make A and B mutually locked, it is also required that the end of the convex A is wider than the end connected to the edge of the piece. This kind of bulge, which is wide at the front and narrow at the back, is called a dovetail in traditional woodworking. We may also call the bumps and depressions of the jigsaw pieces "mortise" and "hole". However, if the dovetail with the tip is done on the cardboard, it is easy to layer and damage the pieces, so the tenon and the hole in the jigsaw are mostly round.
In some puzzles (probably the most common type), all the pieces are of the same shape. Each piece has an axisymetrical two-tenon (p) and two-tenon (P) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) -tenon (p) etc. In this way, bits and pieces are always crisscrossed. Some pieces of the jigsaw puzzle have different mortise and tenon structures, but usually the main body of the pieces are quadrilateral, with a tenon or hole on each side of the four.