Business Intelligence: OEE

The increasing pressure on sales margins is forcing managers of print shops to look for tools to monitor production equipment performance via KPI’s (Key Performance Indicators). One of the frequently used indicators in other production industries, is OEE (Overall Equipment Effectiveness). This indicator is slowly finding its place in the print industry as well.

The OEE indicator shows how much of the maximum production capacity is reached over a selected period of time. It is expressed as a %, where 100 % is the theoretical maximum.

In the picture below, the HP PrintOS offers an OEE score of a HP WS6800 press over the last 2 weeks : 36 %.

The OEE tool shows how much time out of the planned production time was productive and how much time is spent on activities considered as productivity loss. With the OEE metric customers can constantly focus on their main operational opportunities. OEE is just a metric that will show you whether the improvement decisions that you are implementing to perform better, are indeed effective. You can still be a bad performer, but you can measure improvement.

Let’s first continue on some examples where OEE can help you before explaining how you can calculate an OEE for your machines in more detail. 

Suppose you have decided that you will standardize paper widths, as is often done on digital presses. The expectation is that you will have less stand-still to change rolls on your press. In measuring your OEE for these presses before and after this decision was put in place, you should see an OEE increase.

Or you could compare the OEE of a conventional press before and after installing an automatic unwinder. You expect to reduce the time changing rolls, so your OEE will have increased when comparing before or after the install of the unwinder.

Or you could compare your machine’s OEE with your colleague-printer that has an identical machine producing an identical product portfolio in a similar average run-quantity range.

That’s why the Heidelberg Performance Benchmarking program shows the OEE value of your press within your peers (identical presses), taking the average print run length into consideration. In the picture below, you can clearly see that OEE goes up when average print run length increases. This is logic, since longer print runs require less stand-stills.

So comparing OEE’s amongst printers is dangerous, since the conditions can be completely different. Still the OEE indicator remains very interesting.

Of course, the number of roll changes per day would be an as good metric to check whether standardizing paper widths is effective. And timing the average production speed (including roll changes) over a longer period of time would also answer the question whether an unwinder was a good investment or not. But in changing many parameters in a press production, the OEE can give you an overall improvement indication. So, changing to standard paper widths, reducing the unique number of papers used, adding an unwinder and adding a rewinder and a waste removal system should all contribute to an increase in the 1 OEE metric. That’s why it is such an interesting and simple measure to use.

A monthly report on OEE can turn out to be useful to monitor the performance of your machines in a more permanent way as it is possible that production parameters change without you being aware. If these changes have a negative effect on the total good production output, you will see this in a decreasing OEE value. This can be your trigger to start looking for the root cause, by drilling down to compare detailed data like average run length, average number of colours, number of inline finishing stations used, change of operator, change in quality procedures, …

Let’s now jump to the mathematics. OEE is a % of how many ‘good’ products a machine produced compared to what it could have produced in the allocated time. In the below graph, the OEE of a machine is 13 % in January and it is fluctuating between 20% (max) and 6% (min) in the year.

This means that this machine could theoretically produce 87% more good products in January.

January’s 13% OEE is a multiplication of 3 individual percentages, as you can see in the 3 combined graphs for the same machine below: 63 % (quality) * 51 % (performance) * 41 % (availability) = 13 % OEE.

Notice that although the quality and the performance are rather stable, it is the availability that is causing the variance between 5 and 20 %.

Availability is a time factor: the percentage of time a press is available to print (or printing) compared to the total planned production time of this press. Availability can be improved by reducing setup time or downtimes so that you have more time to really print. Setup time for example can be reduced by scheduling jobs in a more efficient sequence or by reducing the number of paper widths used or by adding an unwinder to change rolls.

Discussion item can be the total available time of a machine. In most cases you take the total of all shifts scheduled minus the breaks. When comparing with others, it is important to inquire about their definition of availability since it is obvious that a 24/7 is unreachable.

Performance is a speed factor: the average [KA1] speed of the printing machine during production versus the theoretical maximum speed of the machine. Reasons for running jobs at a slower average speed could be their technical difficulty.

Quality is a good/bad factor: the total amount of good meters/sheets compared to the total amount of meters/sheets consumed. A way to improve quality is reducing produced waste. This can be accomplished, for example, by introducing gang printing to reduce the amount of plate changes and their waste meters/sheets.  

So if you want to install an OEE evaluation on your machines, you need to have the 6 following values measured on a day by day basis and stored per machine over a long period of time : the total available time, the total time ‘printing’, the total meters/sheets consumed and the total good meters/sheets produced, the average speed while running and the maximum possible speed.

The CERM MIS software is storing these data for you and offers you a standard OEE indicator per machine in its Smart BI software.

01/07/2019