Flow regulating control with multi-start threads and spline forms
Our customer asked us to manufacture the right tooling to produce two off components to a series of tight tolerances and requirements
We were asked to produce components used to control fluid flow that will always orientate in the same position and give rapid movement in or out with minimum rotation. The strict tolerances governing the fit of the parts had to be adhered to throughout in order to ensure the 'tactile' feel to the user was always as good as it could be.
Our answer to this was to manufacture tooling that could produce two off components to the technical tight tolerances required - ensuring the requirements could be met. The first tool was designed to produce the drive component with an internal multi-start, left hand thread. To ensure the stop start would always be engaged in the correct position, one thread was deliberately omitted. That was the six start thread which allowed for rapid forward and back transition of the mating part with minimum rotational turn of the component.
The second tool was designed to have an external multi-start thread with one thread omitted. This, when mated with the first component, gave the 'dead on' alignment and allowed for quick transition.
To overcome the undercut issue that was caused by forming a multi-start external thread in plastic, we removed the area of undercut created at the split line by coring it out. The flow was then controlled with a profiled varying set of splines made up of more than 20 inserts with different spline profiles machined in to them.
Many of the mould tools we run in our moulding machines have complex cores which operate in a plane 90 degrees to the tool opening plane.