Simple solution for wood-cutting application
November 2000
PLCs, DCSs & Controllers
A customer wanted to control the feed rate of lumber into a saw to maintain efficient speed without loading down the saw motor. A Red Lion motor drive controller was used to implement this function.
The saw blade runs at a maximum speed of 2200 rpm and at this speed the conveyor should feed the lumber at a rate of 3 m per minute. The MDC is used in the follower mode. The saw blade is driven by a shaft which has a 60 tooth gear; this is used as the lead input. The feedback signal will be provided by a 120 ppr encoder that uses a 300 mm circumference wheel riding directly on the conveyor that feeds the lumber. The MDC effectively monitors the saw and conveyor speed and adjusts its 0-10 V output to increase or decrease the conveyor speed accordingly. The customer also opted to use the two standard alarm outputs of the MDC. One was programmed as zero speed to inform the operator if the conveyor had stopped moving by turning on a light. The customer programmed the other alarm as a deviation alarm to warn the operators if the blade loading exceeded its limit, by turning on a buzzer. To eliminate the need for external pushbuttons, the front panel F1 and F2 keys were programmed for run and stop respectively.
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