A contractor installed a new production machine and left without testing it. The operator has contacted maintenance to say it won’t start.
You arrive and ask the operator to show you what he means. The operator’s control screen functions, so clearly there is power to the system. You ask the operator what should happen when he taps the START button onscreen.
He does that and various pilot lights come on. Then he points to one end and says, “Parts come in here, through these hoppers.” He motions along the machine, describing what each section should do. “And out this end, you get the finished piece. But as you can see, no parts are coming in, and this conveyor isn’t moving even if they did.”
You ask him if there is a simulation mode so you can isolate the problem a bit. There isn’t. How might you solve this?
First, check the drive motor for power. Perhaps the contractor left it locked out or did not connect it. There is probably an interlock that prevents parts from entering if the conveyor isn’t moving; check the control logic. Also look for an interlock that prevents the system from running unless the parts are “loaded” and available to the conveyor.
If the motor has power available to it, then perform a basic function test with the load disconnected to verify the motor will run. If it works, reconnect it.
If there is a parts availability interlock, then check the parts chutes. Do the gates operate, and are there parts on the supply side?
If the machine checks out, next turn your attention to the operator controls. Determine which input(s) and outputs should change at the PLC when the operator pushes START.
