Servomotors and indexers: They make a great couple!

Standard cam-driven mechanical indexers with motion and dwell periods on the cam are frequently driven by a servomotor instead of the usual AC or DC permanent-magnet motor. This provides many benefits:

• Synchronization of the indexer with the rest of the multiple-axis machine – not just simple speed control. The controls know exactly where ALL motion devices are, not just some of them.
• Asynchronous motion and reversing motion, often used in accumulator applications, variable speed and synchronized speed applications.
• Double-index, on demand, as required for part rejection or alternative part presentation.
• Reliable electronic braking for emergency stops and high-performance cycle-on-demand capability. The servo is a non-wearing clutch-brake, providing accurate, repeatable performance.

Servomotor-driven indexing also works well on precision link conveyor applications (with and without the indexer) and can serve effectively as an electronic jackshaft to synchronize several pick-and-place parts handlers. Contact your local IMC-Camco-Ferguson sales engineer for assistance in the effective marriage of mechanics and electronics.

Things You Should Know

Emergency Stops – Safely Stopping Your Indexer

OSHA and other regulatory agencies would like machinery to stop instantly. The real-world compromise is to stop SAFELY, in a minimum amount of time and within a minimum reasonable distance. In fact, light curtains are often distanced based on the time required for a machine operator to travel from the curtain to the moving part. 

Moving parts represent kinetic energy that must be dissipated - usually in the form of heat or electrical energy – at a controlled rate to avoid damage to the mechanical power train. The worst possible time for an emergency stop is near the mid-motion of the index, at peak velocity. A safe stop guarantees that components are not broken and that downtime, and any associated maintenance, is avoided.

Upon request, IMC engineers can evaluate and calculate the minimum stop times, travel distances and loads seen by critical components. Things to consider:

• Large enough brake to absorb energy quickly, taking into consideration the inertia of the brake and motor assembly. Remember that the brake must stop itself and the motor, in addition to the reflected indexed load.
• Rather than simply cutting power, use the AC or DC drive for a controlled stop of the motor. This will often stop the motor faster.
• Use proper sequencing. The motor should be de-energized before clutch-brake activation.
• Proper choice of peak motor speed and gear reducer ratios.
• Choice and settings of mechanical motor brakes – these are usually discreet settings controlled by springs.
• PLC and control circuit scan time.
• Safe procedures for locking out – electrically and mechanically – and resetting equipment after an emergency stop.

IMC application engineers are available to assist you when considering safe emergency stops. Contact your local IMC salesperson for further information.