Overall Equipment Effectiveness (OEE) is a powerful tool that can be used to benchmark, identify areas for improvement, and measure progress. It combines equipment availability, performance, and quality (waste) into a single metric. See Measuring Efficiency with Overall Equipment Effectiveness for previous coverage on how OEE can be used to both measure your production efficiency, as well as use it as a tool for making equipment purchasing decision.
With a complex manufacturing process, packaging printers have a lot of opportunity to use OEE to improve their operations, from prepress through finishing and lamination. By looking at the individual components of OEE and the drivers affecting them, it is possible to identify an operation’s weaknesses, prioritize their impact, take corrective action, and track improvement. Increasing OEE leads to a more efficient, productive, and profitable operation.
It is important to recognize that the entire process is an integrated system—what happens in prepress and plate making affects the press, and the printed product affects laminating and converting. Today we’ll look at the components of OEE in the context of flexo printing.
Availability measures the proportion of time a press is actually printing. When one thinks of equipment availability and downtime, the first thing that comes to mind is maintenance, whether scheduled or unscheduled. There are, unfortunately, many other sources of downtime, most of which can be attributed to a few key areas. The most infuriating is “waiting”: waiting for work, waiting for plates, waiting for ink, waiting for material, waiting for a customer. Some of this is unavoidable, but most can be addressed through scheduling or making sure the needed plates, aniloxes, and materials are available, prepared and ready to go well before the job is scheduled to start. Addressing this can have a major impact on equipment effectiveness and is a good first place to start.
The two areas where equipment effectiveness can be improved dramatically are shortening make ready and lessening wash up and changeover time. These take on particular importance as run lengths decrease and presses become more automated. Faster make ready is key. It can be sped up by simplifying the entire process. For example, not only should the press be fingerprinted, but the aniloxes and ink should be optimized as well. Printers should run a banded roll to determine the optimal ink-carrying capacity or volume on the aniloxes to be used. Even small differences can have a major impact on density. Consistency and predictability of ink laydown and color density will limit the number of pulls and ink adjustments required.
A second area that’s ripe for improvement is the time it takes to wash up and changeover to the next job. Simplifying and standardizing processes and inks used (as much as possible) will make this faster. Time spent between jobs is non-productive.
Quality has a particular meaning in OEE; it is simply a measure of the amount of waste. Waste includes both make ready waste and production waste, either on press or in converting. If a job calls for 60,000 bags and 65,000 linear feet of substrate, and 75,000 is used, 15% of the material is waste. This waste can come from make-ready, bad printing identified on press, or unacceptable quality found in converting. Material waste is a significant cost as well as a productivity drag. OEE doesn’t address other areas of waste, such as ink savings or lamination.
Performance is the relationship between the theoretical maximum press speed and the actual speed in production (or, alternatively, the target time to produce the desired number of pieces compared with the actual time). Performance includes minor stops such as plate cleaning, web breaks, or roll changes; some of these are inevitable or uncontrollable, but others can be improved. Press fingerprinting and using the right aniloxes will provide better ink laydown, which should not only help with plate cleaning but also with color problems and other press issues. It also enables increasing press speed.
Packaging and label printers rarely run their presses at their full potential rated speed. There are a number of reasons for this, but improving production processes, ink transfer, and color consistency all enable faster production. Even a small increase in speed dramatically improves equipment effectiveness, productivity, utilization rates, and therefore profits. Increasing the speed of a label press from 150 fpm to 180 fpm represents an additional 20% capacity; going from 500 fpm to 700 fpm for a wide web press is a 40% increase. These are almost always achievable results, and an OEE analysis can point to the impact of potential improvement.
OEE can be a powerful tool to identify areas for better press utilization and effectiveness. Every part of the operation feeds into one of the key OEE categories. Faster setup improves press availability. Fingerprinting the press and using the right screening and aniloxes can improve ink transfer, enabling the press to come up to color faster and facilitates running the press faster, thus improving availability and performance and reducing waste. Using fewer spot colors will shorten wash-up and changeover time, improving availability.
OEE can be a useful tool in identifying which processes affect equipment effectiveness the most and which areas will have the greatest impact on improving operations.