The untold story of ‘Zippers’ part2
Making of the Metal Zippers:
The stringer is made by passing a wire through a rolling mill to form a Y shaped wire. This is then cut to make the tooth for the zipper. The tooth is then punched into a scoop with a die and is put in a slot on a rotating turntable. The turntable is rotated to 90 degrees and another tooth is fed into the slot. This tooth is clamped into a cloth tape. In a second method, the wire is passed through a head and pocket punch, to make scoops. A blanking punch cuts the scoops and makes the Y shape. The legs of the scoop are then clamped to a cloth tape. This method proved faster than the previous Sundbacks method. Yet another method is prevalent wherein a chain of teeth in molded and clamped around a cloth. This cloth is injected with molten zinc under pressure. The mold is cooled by the water and shapes the teeth. Residues are finally trimmed.
Making of the Plastic Zippers:
Stringers for plastic zippers are made similar to metal ones. Two methods are prevalent to make plastic zippers. In the first method, a round plastic wire is fed in between two heated screws. One screw rotates clockwise, and the other one counter-clockwise. This rotation forms loops in the wire. A head maker presses the loops into a round knob. It is then cooled. Left and right spirals are made simultaneously from two different machines, so that they match with each other. Under the second method both left and right spirals are made from the same machine. A piece of wire is looped twice between notches on a rotating forming wheel. A pusher and head maker works at the same time to form the notch and the head at a time. This process makes a zipper that is already linked together in a cloth tape. Superior quality of plastic zippers is
made by weaving them directly into the cloth like weaving.
Quality Testing:
A zipper should meet the textile quality standards. Once manufactured, the zipper is tested for its flatness by passing a gauge set at a certain height. If the gauge touches the zip many times, it means the zipper is defective. It is then tested for its straightness by laying it across a straight edge and is scrutinized for any curving. Zippers are tested with small steel balls to test coating for abrasion. They are also tested for shrinkage. Two marks are made in the tape, and they are measured before and after washing or heating, to check if there is any shrinkage in its length. Normally light weight zippers will have one to four percent shrinkage and heavy weight zippers will not have any.
Leading Global Companies:
Japan is the leading producer of zipper and manufactures 68 percent of the zippers manufactured around the world. Major zipper manufacturing countries of Southeast Asia are India, Bangladesh and China. Chinese made zippers are known for their inexpensive prices. Their zipper industry keeps growing on an average of 18 percent annually for the past five years.
Today zippers can be found everywhere; clothing, luggage, leather goods, and many other objects. They are successfully dominating the world of fasteners for more than a century. They are required and used by each and every person all around the world.
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