Springs are everywhere in daily life – in your children’s toys, in the hinges of your dishwasher, in your medical devices – even in aerospace components! Despite the wide variety of custom manufactured springs, the process of producing them is remarkably standard.
That’s not to say there’s no difference – springs in medical devices or aerospace modules often require far higher levels of precision and will need to survive extreme temperatures and long use. But while the type of metal may vary depending on the application of your custom spring or stamped metal parts, the process of their production is fairly standard.
Forming Custom Springs
The first step is the coiling process. Whether it’s an extension, compression or torsion spring, they all begin life as a piece of wire. The material of the wire and its diameter will vary depending on its end use.
Here at Arrow Manufacturing in Connecticut, we have a large range of coilers that can handle wire diameters from .003” to .112”! The wire is fed onto the appropriate machine and quickly formed.
Heat Treatment and Quenching
After a spring is formed to its custom specifications, it’s then heat treated – subjected to extreme temperature to give the metal the ‘memory’ of its new shape. Depending on the gauge the spring might actual be wound hot as well, but in either case, during or after coiling, springs are heated to temperatures as high as 1688˚F! After heating they are quickly plunged into a vat of oil that cools the springs rapidly and makes the form very strong, but brittle.
The second round of heating is more gentle, and involves more moderate temperatures and cooling processes to finish the spring. This round alleviates any stress caused by the coiling and quenching processes, and gives the spring back its flexibility.
If it’s an extension or compression spring, the ends are then typically ground flat so the spring will sit straight up. Think of a mattress – you wouldn’t want the springs to all be poking slightly different directions! It’s important for the force to be exerted straight up and down.
Some custom springs will undergo further treatments. Shot peening is a process where the spring is exposed to a storm of tiny steel balls to hammer down the exterior of the spring and close up any cracks in the material that may have occurred in the production process. Shot peening helps improve the lifetime of the product, and helps prevent any cracking in response to stress.
In the penultimate step, the spring is fully compressed or extended several times, to permanently set its form. Setting gives the spring its final length and spacing between the coils (known as the pitch).
The final step in the production process is applying a thin powder coat to the spring. It helps protect the spring from rust, but customers also sometimes request specific colors for aesthetic reasons. We custom coat or paint springs for our customers – OEM automotive components, for instance, are often requested in yellow, black or red.
Of course, although not listed here, design and quality control are two steps that are actually the most important in producing a custom-manufactured spring. A spring can be perfect technically, but if it hasn’t been designed for the right specifications it will fail quickly or cost more than necessary. Our quality checks are also extensive before we ship out any order. We have a range of optical and mechanical quality control steps to make sure any custom spring design has been produced to its exact specifications and will work as intended.