Quality is an energy-saving issue

Not only is quality an energy-saving issue, but energy-saving is a quality issue.

By David Manning-Ohren, Condition Monitoring Manager, ERIKS

Achieving optimum product quality is obviously high on the list of any manufacturer, for all kinds of reasons – many of them fairly obvious and most of them related to cost. However, there is a quality-related cost which is relevant and important to reduce, but which is often overlooked: the cost of wasted energy as a result of poor quality production. So not only is quality an energy-saving issue, but energy-saving is a quality issue.

Poor quality production which makes it out of the factory means dissatisfied customers. But even poor quality production which is spotted before it gets that far means wasted time and raw materials. Take that to its logical conclusion and ultimately it means wasted energy too: at every stage from the production process which didn’t produce anything saleable, to the energy cost of recycling the sub-standard finished product for reuse of the raw materials. (In the case of, for example, an aluminium casting, that cost is enormous.)

At its simplest, if you are making something twice instead of once, it is a clear waste of energy which, if quality is satisfactory, need never happen. Improving quality may seem essentially an internal issue. However, closer analysis will show that in fact the inextricable integration of a production process means that consideration of a machine, its components and its controls can help to achieve improved quality just as much as more obvious approaches.

ERIKS, for example, is highly experienced in conducting air leak surveys. By identifying the location of an air leak and correcting it, you ensure the right pressure is available in pneumatic systems, which then means the right force is being applied, which in turn leads to the right quality of finish for the final article.

1. Determine the equipment’s overall availability rate, by dividing the operating time by the planned production time. For example, if the equipment operates for 400 minutes but the planned production time is 500 minutes, the availability rate is 400/500, or 80%.

2. Determine the equipment’s overall performance rate, by dividing the ideal cycle time by the actual cycle time. Cycle time is the amount of time it takes to produce one piece. So, if the ideal cycle time is 100 pieces per minute and actual cycle time is 75 pieces per minute, the performance rate is 75/100, or 75%. (To determine the actual cycle time, divide the number of pieces produced by the amount of time taken to produce them.)

3. Determine the equipment’s overall quality rate by dividing the number of good pieces produced by the total number produced. For example, if the equipment produced 400 pieces but 20 were defective, that would mean only 380 good pieces. So dividing 380 by 400 results in an equipment quality rate of 95%.

4. Multiply availability rate x performance rate x quality rate. The product of the three numbers is the Overall Equipment Effectiveness, or OEE. Using the example above: 0.8 (step 1 result) x 0.75 (step 2 result) = 0.6. Multiply this by 0.95 (step 3 result) = 0.57 or 57% which is the OEE.