The helical flexure - a designer’s flexible friend

01 April 2009

A cellophane packaging machine manufacturer had experienced problems with a plastics die cutter, which was becoming prematurely blunt on high-volume runs. The die cutter was originally attached to a solid shaft holder, which had to be constantly adjusted to keep the cutting edge perpendicular to the roller. The machine was operating 24 hours a day, at the rate of 180 packages per minute, and the best life expectancy obtained from the die cutter was about a month before it had to be replaced. The solution to the problem was found in Abssac’s helical flexure technology.

The performance of a helical flexure is determined by six characteristics: its outside diameter, inside diameter, coil thickness, material of construction, the number of coils, and number of starts. By altering these characteristics, torque capacity, angular and parallel misalignment capabilities, and the torsional and lateral bending rates of flexured u-joints can be modified to suit the application requirements.

Following a short design exercise, Abssac suggested using a shaft manufactured from heat-treated stainless steel and a flexure design specification that ensured correct loading and cutting-edge perpendicularity. The end result was, in affect, a shock-absorbing, yet load bearing assembly that extended the die cutter life from one month to 10-12 months.