Zippers are composed of two “stringers”, which in turn consist each of the tape and teeth assembly that makes up one side of a zipper; the “slider”, which connects and disconnects teeth of both stringers and with that closes and opens the zipper; a “tab”, which moves the slider; and “stops” that prevent the slider from falling off the zipper.
Teeth, slider, tab and stops of a metal zipper are usually made of stainless steel, aluminum, brass, zinc, or a nickel-silver alloy while plastic zippers have teeth made from polyester or nylon and slider and pull tab from steel or zinc.
One stringer with metal teeth (one side of the zipper) is made when a round wire is sent through a rolling mill which shapes a wire into a Y-shape. Wire is then cut to form a tooth with width that needed for the type of zipper that is made. Finished tooth is then put into a slot on a rotating turntable that has a die which punched a tooth into the shape of a scoop. Same part of the machine claps a tooth onto the cloth tape. Second method also uses metal wire but this time flattened one which is treated with a heading punch and a pocket punch that make scoops which are cut with a blanking punch that makes Y-shapes. Y -shapes are used to clamp wire around the cloth tape. Third method for making metal zippers uses mold in the shape of the negative teeth that is clamped around the cloth and filled with molten zinc under pressure. When the zinc colds it is shaped like teeth.
Types of teeth of plastic zippers are much diverse compared to the metal ones. There are spiral, toothed, ladder, or woven plastic zippers. Spiral plastic zippers can be made in two ways. With first, round plastic wire is notched before feeding it between two heated screws. Loops are made by those same screws and then those loops are heated with head maker to form heads. Left spiral and right spiral of the stringers are made simultaneously on two machines so they would mach and could close. Second method makes both spirals at the same time at the same machine. Machine has a rotating forming wheel with notches that makes both loops on one notch. Heads of teeth are formed when pusher and head maker simultaneously press the plastic wires into the notches. Those spirals are already locked together and closed and are just sewn onto two cloth tapes. Stringers for toothed plastic zipper are made with molds and molten plastic just like for metal zipper. Machine for making ladder plastic zippers has a rotating forming wheel from which protrude alternating spools onto which a plastic wire is wound. Loops are made with strippers on each side and shaped into U-shape by heading and notching wheel that also forms heads on the teeth. Teeth are then sewn onto the cloth tape to make stringers. Woven zippers are made by weaving the plastic wire directly into the cloth which makes zippers of high quality.
Stringers are then connected temporarily until slider and tab, which are connected separately, are connected to them.