| CPC B41J 2/04513 (2013.01) [B41J 2/04581 (2013.01); B41J 29/20 (2013.01); B41J 2/165 (2013.01); B41J 2/16579 (2013.01)] | 18 Claims |

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1. A control unit for performing maintenance of an inkjet head unit for discharging a substrate treatment liquid onto a substrate comprising:
a count module for counting the number of discharges for each nozzle of the inkjet head unit;
a comparison module for comparing the number of discharges with a reference value to determine whether the number of discharges is equal to or greater than the reference value; and
an evaluation module for evaluating whether a life of the inkjet head unit has reached a usable life based on whether the number of discharges of each nozzle is equal to or greater than the reference value,
wherein the count module counts the number of discharges based on whether a voltage is applied to a piezoelectric element involved in operation of a nozzle.
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