Abssac has produced a tiny titanium machined spring, complete with end
connections, for a special medical application. Its physical size (just a
few millimetres in diameter), repeatable precision spring rate and
one-piece integrity cannot be realised using conventional wire-wound
springs, claims the company. With the machined spring, perpendicularity,
parallelism, lateral bending, axial and torsional rates can all be
guaranteed. It can provide very precise linear deflection rates because
virtually all residual stresses are eliminated. As a result, there are no
internal stresses to overcome before deflection occurs, which is often
the case with a wire-wound spring.
In addition, multiple start spring coil configurations can be
manufactured, the most common being the single start spring, which
comprises a single continuous coil element. A double start spring has two
intertwined continuous coil elements - effectively placing two
independent helixes in the same cylindrical plane.
Multiple start flexures (ie greater that two) are similar extensions of
this concept. Multiple start springs provide redundant elastic elements
in the event of a failure. Moreover, the failed element will be trapped
by those that remain intact, so the spring can continue in operation,
albeit with reduced function.