This determines the flexing properties of perforation-resistant inserts (midsoles) used in safety footwear.
The SATRA STM 441 is a six station machine with two banks of three stations on either side of the central body of the machine. The inserts, usually of steel, are located in the machine clamps, together with the correct interlayers (supplied) and free end resting against the flexing bar. The angle of flex can be adjusted to meet the appropriate standard.
A timer is provided to stop the bar once the required number of flexes has been reached so that the inserts being tested can be inspected. The machine is designed to operate at 16 cycles/second.