I have seen advertisements for machined springs and wondered what types of equipment would use a spring cut from one piece of metal. I discovered machined springs have capabilities that can outshine those of helically-wound wire springs, but at higher cost. Forming a wire spring takes only a few moments, but machining a spring from a block of metal requires many operations with expensive production machinery.
Unlike wire springs that require “flattening” at each end, a machined spring can provide a solid annular surface at each end, and machining can include a fastening structure such as a threaded shaft or hole. In addition, the machining process provides for greater dimensional precision–generally 1% compared to about 10% for a wire spring. (see Ref.)
By machining an integral attachment such as a flange, a pin, or a clamp, you can reduce assembly time and save money by not having to stock extra hardware.
Photo courtesy of Helical Products Co., www.heli-cal.com.
Machining also provides an additional benefit: The spring manufacturer can create multiple “starts” in the material so you can have several helical spring members around the axis. Wire springs cannot usually reproduce that type of structure.
You’ll find, though, that machined springs have limits imposed by size and materials, and they might need more length than a wire spring to provide the same elasticity. But if you use springs in a product, machined springs deserve a look. –Jon Titus
Ref: Boehm, Gary L., “Wire Springs or Machines Springs,” Design World: http://www.designworldonline.com/articles/527/262/Wire-Springs-Or-Machined-Springs-.aspx.