The customer is currently using a standard duty Coiled Spring Pin for use as a hinge pin in a circular saw blade guard application. An engineering review was generated to review this application because the customer complained of excessively high insertion forces.
The customer had two different assembly lines that were used to install the Coiled Spring Pin. All of the insertion problems were experienced on the fully automated line that had less than half of the insertion force of the semi-automated line. Based on empirically derived insertion data for the Coiled Spring Pin, the automated line had a cylinder that was undersized for this application.
The customer did not provide any shear strength requirements for the Coiled Spring Pin in this application. A simple option for the customer, which would require no changes to the automation equipment or the hole sizes in the components, would be to change to a light duty pin. The insertion force for the same Coiled Spring Pin in light duty is approximately half that of the standard duty pin in the same application.
There were several other observations and recommendations by Engineering. The customer was using a tapered disappearing pin to align the holes. The disappearing pin diameter measured from .211 to .250. This means that there was a tendency for the top holes to be misaligned due to the severe taper. The diameter of this alignment pin should be .252 for its’ entire length.
The insertion quill also had slightly rounded edges. The quill was smaller than the diameter of the Coiled Spring Pin; therefore, the quill was pressing on the inner coils, which increased the insertion force.
SPIROL stressed that it is important that the assembly be supported/clamped to limit the cantilever lifting action during insertion.
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