Bespoke spring solves motor bearing pre-load problem
A conventional die-stamped wavy washer, used to pre-load a standard 608
bearing on an 8mm motor shaft appeared to be the source of increased
noise and excessive wear, when TFC was called in by the motor
manufacturer to help solve the problem. The cause turned out to be
limited available working height for the spring, which varied between 2.2
and 1.42mm after tolerances had been taken into account. The die-stamped
spring wasn't able to provide a controlled spring rate over these maximum
and minimum conditions.
TFC suggested using a Smalley crest-to-crest Spirawave spring, which is
able to develop similar forces to conventional round wire or helical
springs, while occupying a third or less space. The company produced a
bespoke four-turn spring from narrow section 17-7 precipitation hardened
stainless steel flat wire in a design that was sure to supply the spring
rate needed for the application.
Spirawave springs are drawn from a continuous coil of single-filament,
pre-tempered wire, so there are no tooling costs associated with their
manufacture - clearly a bonus for the motor manufacturer, who was able to
take advantage of reduced lead times and much lower costs.