OpenSpecEngineering

Finds the overall equipment effectiveness (OEE) of a machine or line over one run, such as a shift: the share of the planned time that made good parts at full speed. It also splits the loss into its three parts, so you can see whether stops, slow running or scrap costs the most. Plant, maintenance and continuous-improvement engineers use it to track equipment and to rank TPM projects [1], [2].

Equations

OEE = A × P × Q

A = (t_p − t_d) / t_p     P = (c_i · N) / (t_p − t_d)     Q = G / N

t_p is the planned production time and t_d the unplanned downtime within it, so t_p − t_d is the run time. c_i is the ideal cycle time: the fastest the machine can make one unit. N is the total units made and G the good units, those made right the first time with no rework or scrap. Availability A is the stop loss, performance P the speed loss and quality Q the defect loss [1]. The fully productive time, OEE × t_p, equals G × c_i: the time the good units would have taken at the ideal rate.

Limits and common mistakes

• Planned production time leaves out planned breaks, meals and time with no orders. Changeovers and breakdowns count as downtime.
• Use the machine’s nameplate or design cycle time, not a past average. A slow “ideal” hides the speed loss. If the page reports performance above 100 %, the ideal cycle time or the counts are wrong.
• Count reworked units as bad. They took machine time but weren’t good the first time.
• Times are in minutes and must all be in the same unit. Compare OEE only between runs measured the same way. The SEMI E10 and E79 terms [3] differ in detail from the TPM ones used here.

Worked example

A packaging line runs a 450-minute shift after breaks. It stopped for 38 minutes, its rated speed is 80 cartons an hour (0.75 minutes each), and it made 520 cartons, of which 506 were good. What is its OEE?

1. Enter Planned Production Time (min) 450 and Unplanned Downtime / Stops (min) 38.
2. Enter Ideal Cycle Time (min per unit) 0.75.
3. Enter Total Units Produced 520 and Good Units (no rework/scrap) 506.
4. Press Solve. The Solution shows: Run time: 412 min
   Availability: 91.5556 %
   Performance: 94.6602 %
   Quality: 97.3077 %
   OEE: 84.3333 %
   Fully productive time: 379.5 min

Check: 506 good cartons at 0.75 minutes each is 379.5 minutes, and 379.5 / 450 = 84.33 %. Availability is the largest loss here, so the stops are the place to start.