H&R stocks spring wire from 0.3 to 32mm, in 0.25mm-diameter steps, giving its engineers great design freedom.
H&R stocks spring wire from 0.3 to 32mm, in 0.25mm-diameter steps, giving its engineers gr
Manufacturing in Germany is very expensive. To remain competitive, H&R must have the best quality and good service: A premium product justifies its price. Though its product range is diverse, H&R's main factory is for the most part a spring factory. TRAK+ wheel spacers are made elsewhere, and most of the damper work done in Lennestadt is development and low-volume production.
Spring manufacturing starts with wire storage; H&R stocks spring wire from 0.3- to 32mm, in 0.25mm-diameter steps. Rolls of wire are mounted on a Wafios CNC machine, which straightens the wire before feeding it through a series of rollers and shoes that wind it into a spring. The finished spring is cut off with a scissors-like die, perhaps the loudest operation in the plant. The Wafios machine operator can't simply put the wire in the machine, push a button, and come back to a basket of springs in an hour. The shoes and rollers wear, and calibration can vary between machines. Each time a new spring batch is begun, the output must be checked and measured dimensionally, perhaps requiring adjustments to the machine's program. Once production begins, springs are checked for length as they come off the machine.
H&R's Wafios CNC machines straighten the wire before feeding it through a series of rollers and shoes that wind it into a spring.
H&R's Wafios CNC machines straighten the wire before feeding it through a series of roller
Annealing is a critical step that must be done within two hours of winding the spring. It allows the cold-work stresses that were put into the metal to relax, restoring its elasticity and strength. If it is not done in time, the stresses will become permanent and the spring will not function as designed. In special cases, additional heat-treating processes may be required.
If the design calls for it, the spring's ends are ground flat before shot peening, which consists of blasting the springs with 0.9mm steel shot at high speed as they are turned over in a tumbler. The result is that the surface of the spring is permanently compressed, increasing strength and fatigue resistance. A shot-peening cabinet's internal components last about six months, and a rebuild, in which most of the internal parts are replaced, costs roughly 50,000 Euros.
Between annealing and shot peening, many spring designs require the ends to be ground flat at a precise length.
Between annealing and shot peening, many spring designs require the ends to be ground flat
Block setting is the final forming process. To ensure that all the deformation that will occur does so at the factory, the springs are wound slightly longer than their final length. The spring is repeatedly compressed to coil bind, the point where it becomes a solid block of metal and can deform no further. Once this process is complete, sagging is impossible. Afterward, each spring is again checked dimensionally both free and under load.
Springs are stored in an oil bath between block setting and powdercoating to prevent even microscopic surface corrosion from forming, which would create a pit that could be the beginning of a crack.