AAOM Handbook

The charts progressively look more ‘acceptable’. In the monthly chart there are a few low periods where obvious reasons, or excuses, may be proposed for the low output, but otherwise the results appear to be reasonably steady, and you may even hope that the performance has improved – even though the reality is very different. These filtered charts hide the fact that the large swings in the daily output produce lots of waste: • Pushing hard to try to catch up for the low days results in additional labour and energy use, and additional stress to, and failure of, equipment. • The surging and stalling of throughput results in the same type of delays and losses that occur when traffic gets into a stop/start pattern rather than remaining free flowing. • Labour and energy are wasted when equipment fails or the process stalls. Producing with an output variation swing of ±100%, rather than ±10%, can result in waste of between 30% and 50% of the labour, equipment, and energy used in the process. What is also hidden in the averaged data charts is just how much potential capacity there is within the process. While the average output on all charts is equal, no points on the averaged monthly output chart are above 120% of the average, few points on the averaged seven day output are above 125% of the average. However, the chart of daily output rates indicates that there are a lot of days when output was above 180% of the average, with one as high as 200%. For this process sustained output rates that are double the historic average may not be possible, but rates that are significantly higher probably are.

A common consequence of reducing the variation in the output of a Process is that the average output increases. Following is a chart for the same Process as the charts