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Should You Trust the PLC?

GTI Predictive Technology on a recent service call investigated a problem with a dual disc centerless grinder. This one year old grinder had been performing poorly, causing downtime and poor parts quality. Using GTI’s VibePro iPad vibration tools, our service technician discovered that both spindles in the machine were running much faster than rated for the machine; and faster than the speed displayed in the PLC. Both spindles were found to have quite a bit of imbalance.

To fix the imbalance problem the spindles first needed to be running at the appropriate running speed. Our technicians did a quick fix for spindle speed by compensating on the PLC, lowering the displayed speed to have actual speed match specs. Using special weights designed for these spindles GTI Predictive technicians fixed the imbalance problem.

Reprogramming the PLC is still required for a true long term solution. Spindle running speeds should always match the displayed running speed. GTI’s temporary fix involved slowing down the displayed number to match the required running speeds to match grinding specs. Running the PLC in this state for a prolonged period of time could cause other issues such as damaging the rotor or stator.

This example demonstrates how important it is to verify the information displayed by the PLC when diagnosing problems. The accuracy of running speeds and other parameters from the PLC can be critical to finding a solution to the problem. 

Are you sure that your machines are operating where you think they are? GTI Predictive Technology service specialists can help diagnose and solve your machine problems.