Performance
The performance measurement in OEE looks at your “running to standard” by considering both idle and small stops as well as slow takt time as the key indicators for this multiplier. Taken from the German word for the baton an orchestra conductor uses to keep the time or the beat, takt time is just that—the measurable beat or pace of production.
Essentially, takt time is the manufacturing rate for a finished product to get to the customer. This can be both internal and external customers. For internal customers, it is the time it takes to finish a task to completion for the next process that physically changes the product. Transportation from one process to the next, sorting and waiting—these are not measured as takt time, but rather as a form of waste. For external customers, slow takt time results in late deliveries or long lead times.
OEE
Chart 3Instances such as web breaks, blade changes and ink adjustment all count toward idle and small stops. Items like having to run slow due to ink or substrate performance, or registration issues, would account to run standard.
Typically, run standard is measured against the machine rate of the press, rewinder, laminator, etc. If a press machine rate is 700 fpm on the nameplate, that would be the standard of your OEE metric. There are ideal run rates or theoretical run rates that can be used as the standard. However, this would be a standard that company stakeholders would have to agree on, based on a long history or established machine burden rates, especially when those burden rates are based on ROI or asset value of that equipment.
Machine rate is the metric that frustrates machine operators the most, especially in narrow web operations. The leading reason is that machine rates are based on the mechanical capability of the press while not taking into account the many different types of converting done inline, such as die cutting, de-lam/re-lam or cold/hot foil. Machine rates should not be changed to reflect downstream converting unless the downstream operation has an identified mechanical capability associated with it. Then you can take the lesser of the two. An example would be a turret rewinder with a slower speed than the press. If the operation is not used all the time, take the higher of the capabilities. By not doing so, you can introduce bad information to the dataset. Taking the higher capability number will yield a lower OEE number; however, these are your baselines. The rule of “it is what it is” applies.
With any equipment, we all understand that breakdowns, such as web breaks, wrap-ups and ink spills happen along the way. Wouldn’t it be a perfect world if we could all run at the 100 percent rated speed of the press regardless of the job? These anomalies will be identified by using the results of OEE. Equipment, strategies and processes to reduce anomalies and enhance performance could include the following: 5S, press optimization, standardization, inline color management, vision systems, auto-register and maximizing roll length to reduce roll changes.
Quality
Simply put, quality is your yield, defined as good product divided by total product ran (see Chart 2). Almost every plant I’ve been in looks at waste and/or yield as a KPI measurement. If you are tracking good product, the difference in total product ran is your waste and if you’re tracking waste, your total product ran minus your waste is your good product. Essentially, it’s what went in versus what good came out.
Monitoring your key performance indicators is an essential part of production management and continuous improvement.
Quality is a metric where the potential for “creative math” may come into play on production floors, with methods such as understating waste, shorting total product ran or claiming roll footage deviation. Utilizing OEE, you avoid any “fudging” of the numbers to improve without skewing the availability and performance elements to make the math work. Of course, you must always validate your numbers because at the end of the month during inventory, it all gets hashed out and that creative math gets caught.
With quality comes consistency and repeatability. Ways to improve quality metrics include adopting Flexographic Image Reproduction Specifications & Tolerances (FIRST), inline vision systems, auto-register systems and establishing standard operating procedures (SOPs).
When we look at our OEE numbers from a high level (as in Chart 3), we can see our three measurements of availability, performance and quality, along with our final OEE number. It’s easy to see areas that need improvement or may have shown dips that affect your OEE percentage. Often, we know what may have happened, be it bad film, ink, dirty anilox or any other combination of issues that happen in manufacturing. The idea is to understand and see those issues and make efforts to reduce those occurrences to drive the OEE trend upward.
When establishing OEE baselines, often operators, managers and business stakeholders are taken aback initially by the numbers. Especially in the flexo industry, OEE is often a low percentage and a large pill to swallow as stakeholders come to grips with the issues that have arisen. We know that if these issues are left to grow unchecked, they become the bogeys of performance improvement efforts.
Once you understand that the numbers are not a personal judgment, but rather a baseline from which to improve processes, OEE becomes a much more effective tool. It’s really understanding numbers that go into the calculations and why they are what they are.
Overall equipment effectiveness is a way to evaluate how well a manufacturing process is utilized. The three major categories of availability, measuring both planned and unplanned downtime, production measuring both idling/small stops and slow takt time, and quality measuring both production rejects and makeready/startup waste, all make up your six big losses and goal for measuring OEE. OEE gives the opportunity to address the little things that plague us daily and make the manufacturing process as productive as possible. It also allows you to prioritize improvement efforts by evaluating what is happening on the production floor, like downtime wastes, run speeds or capacity.
About the Author: Greg Horney has more than 30 years of experience in flexographic and offset printing. He has a BS in applied arts and sciences from Rochester Institute of Technology. Greg has worked from the ground up in the printing industry where his experience ranges from gopher and pressman to graphics and prepress, quality, continuous improvement/project management, print management and production management.
Greg is a Lean Six Sigma Black Belt and is also FIRST Implementation Specialist Certified. He both chaired and co-chaired sessions at FTA events, most recently chairing the “Pressroom Pressures” session at Forum 2017 and speaking on a panel at Fall Conference 2016. Greg has participated as a judge in the Excellence in Flexography Awards on three occasions and has published articles in FLEXO Magazine. Greg is now applying his years of industry experience to helping Harper Corporation of America and the Harper Graphic Solution Group’s customers as a technical service representative in the Central Plains and Southwest regions.