Coiling of Springs

a technological operation in which a wire or strip is bent into a helical, conical, flat, or contoured spring. A distinction is made between cold coiling (from wire of 0.1–16.0 mm in diameter) and hot coiling (from wire 12–75 mm in diameter).

Springs are coiled by a number of methods. Helical springs are coiled on a rotating mandrel (cold and hot coiling), by means of feed rollers and a fulcrum pin that bends the wire around a fixed mandrel (cold coiling), and by means of feed rollers and two fulcrum pins (cold coiling). The latter method is the most common; it is used on spring-coiling machines. Contoured springs are coiled on special mandrels and attachments, usually on semiautomatic machines. Figure 1 shows an arrangement for coiling helical springs with a uniform pitch, which is set by a wedge that acts on the stock at a certain moment or by a pitch lug that is fed along the axis of the spring. When the feed stops, the finished product is cut off by inner and outer knives. For coiling springs from large-diameter wire (more than 50 mm), very strong fulcrum rollers with grooves are used in place of pins on automatic machines. Conical and contoured springs are produced by means of a lever system that moves the pins toward the point of origin during the coiling process. By displacing the outer pin (or roller) forward, perpendicular to the coiling plane, springs with an interturn pressure (stock for extension springs) may be produced. Hot coiling is done on a mandrel on semiautomatic machines.

Figure 1. Arrangement for coiling helical springs on an automatic spring-coiling machine using feed rollers and two fulcrum pins: (1) rollers for feeding wire, (2) pitch lug, (3) outer knife, (4) inner knife, (5) outer pin, (6) inner pin, (7) pitch wedge