Ensure Safety Using Mechanical Devices

Problem

In order to meet ANSI B 11.1 and OSHA Federal Register Sub-Part 0,1910.217 safety standards, a customer should either have a dual microprocessor based press control system or a mechanical cam limit switch on the press.

Solution

The 1980 Cam Limit Switches provide control reliability. The 1980 Series provides a comparatively stable mechanical design with N.O. and N.C. contacts which can be verified for proper operation each time the press strokes. Compared to these mechanical devices, solid-state devices provide better longevity and versatility; however, they cannot provide the fail-safe ability without a huge cost.

A clutch/brake combination unit connected to the crank controls a mechanical press. This assembly is an air over mechanical device in majority of the cases. When no air is applied, the brake is activated by the springs in the assembly. The applied air overrides the springs and energizes the clutch.

The 1980 Cam Limit Switch creates the contact closures depending on the position of crank (ram) to trigger the brake in the appropriate position of the stroke to halt the ram on top. The cam limit switch is also widely used for the top-stop monitor circuit and the anti-repeat circuit. The anti-repeat circuit makes sure that the user cannot tie down the two-hand control buttons to keep the press cycling. If the last stroke stops the press beyond 5–7 degrees over top, the top-stop monitor circuit will restrict the press from cycling again.

Benefits

  • Largest collection of standard and custom products. With more than 1,000,000 possible combinations in its standard units alone, Ametek is certain to have a cam box for customers’ specific applications.
  • Exclusive three-year warranty on cam boxes. Applies to whole unit.

Conclusion

Rotating cam limit switches have been the core of mechanical press control circuitry for more than five decades for one reason, that is, the control reliability. If this part of the press control fails, a dangerous runaway condition could happen.

This information has been sourced, reviewed and adapted from materials provided by Ametek Factory Automation.

For more information on this source, please visit Ametek Factory Automation.

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