PT Intan Sejati is a company engaged in printing services. The production process at PT. Intan Sejati uses 96 machines. The maintenance activities carried out by the company are corrective maintenance. Engine damage in the period (January-December) in 2018 shows that there are 636 engine failures that require part replacement with 44% of damage occurring in the printing machine, which means the machine's printing process is a critical machine. This study was conducted to classify the criterion index part of the machine using the Reliability Centered Spares method, sorting out critical parts repairable and non repairable, determining the needs of critical parts using the Poisson Process method, determining the minimum and maximum stock quantities, determining the size of orders for economic parts using the Economic Order Quantity. The results of the RCS worksheet show that there are 3 high critical classification parts, 52 medium critical classification parts, 33 low critical classification parts and 48 not critical classification parts. The calculation of part requirements is carried out on 14 part units which are included in the high category and critical medium and have a frequency of damage ≥3 times. 14 units of parts are included in the category of non repairable parts. The biggest critical part needs are on the XL 105 engine with 61 units and the smallest need is on the SM 52 A engine with 21 units. The largest maximum and minimum amount of inventory is on the CD 102 machine with a supply range of 9-26 units and the smallest inventory is on the XL 105 engine with a supply range of 2-3 units. The largest economical ordering size is on the SM 102 B engine with 11 units and the smallest on the XL 105 engine with 2 units.