18. A firm wants to finalize one of the two machines for a particular job. The machines are of similar
types but vary in terms of capacity. The units per hour produced by two machines during test run are
given below. The machine will be selected based on performance and consistency. Advice the firm
about which machine they should purchase?
1
1
1
1
6
1
7.
1
5
1
2
1
7
6
4.
7.
Machine
A
Machine
B
2
0
3
7
1
6
3
6.
3
3
2
4
3.
8
3
0
3
9
3
3
5
4
8
0
Answers
Answer:
Focusing on the OEE score – not the underlying losses
OEE (Overall Equipment Effectiveness) measures how close you are to perfect production (manufacturing only good parts, as fast as possible, with no stop time). Monitoring your OEE score on its own is not all that helpful to improving production. The true value of OEE comes from understanding the underlying losses: Availability Loss, Performance Loss, and Quality Loss. By focusing on these losses, and more importantly, by taking action to reduce these losses, your OEE score will naturally improve.
Using ‘budget’ or ‘standard’ speeds for Ideal Cycle Time
If you want OEE to fully drive productivity improvement, make sure to use the “true” Ideal Cycle Time, which is the maximum theoretical speed of your process. Many companies have ‘budget’ or ‘standard’ speeds that are slower than this maximum. These numbers are useful for production planning, but if used in the OEE calculation they will hide the true capacity of your process. This will artificially raise your OEE score, while hiding loss and slowing improvement.
Excluding changeovers
Changeovers are an essential part of the production process for most manufacturers. Changeover time is lost production time – time that could be spent manufacturing parts. While excluding changeovers from your OEE calculation will increase Availability (and OEE), it will also hide the opportunity to increase output by reducing changeover time. To learn more about reducing changeover time read up on SMED (Single-Minute Exchange of Dies).
Collecting too much data
Keep your OEE data collection as simple as possible. Many managers ask operators to select from a bewildering array of downtime reason codes. Other managers set downtime thresholds so low that operators spend as much time collecting data as running machines. The operator’s job is to run the machine. Asking them to collect large amounts of excessively detailed data will result in poor data or poor productivity. Collect less; do it well.
Using OEE to compare dissimilar processes
Many companies compare OEE scores across divisions, sites, assets, or products. The temptation to do so is overwhelming. Here is the problem. Such comparisons are only truly meaningful when comparing the same equipment running the same product under the same conditions. Let’s consider a few real-world