Changeover greatly affects asset reliability and its impact is often neglected when improving changeover times. Today’s changeovers in manufacturing have followed the same formula as Shingo and Toyota, and many industries have benefited with an increase in uptime and production line capacity and a reduction in finished goods inventory. Equipment manufacturers have successfully added versatility to their product lines; many machines are able to produce dozens of sizes and shapes of products for their customers’ needs. Operational-driven initiatives by Six Sigma, 5S and visual factory methodologies have refined the changeover process on the production floor to help keep conversion times to a minimum. Additionally, original equipment manufacturers (OEM) and aftermarket businesses have eliminated many of the assembly fasteners and replaced them with revolutionary clamps, slides and twist locks.
Reliability Centered Maintenance Principles Relating to Changeover
The principles of reliability centered maintenance (RCM) cannot be ignored when changing over an asset for the next product. When evaluating an organization’s changeover program, these RCM principles need to be upheld:
Preserve System Function – The function of the system does not change with changeover. For example, a tablet press must still produce tablets meeting the same criteria regardless of raw material or size.
Identify Failure Modes That Can Defeat the Function – Both parts and methods need to be evaluated for their impact on system function. Part wear and improper task execution can lead to failure.
Prioritize Function Needs – The importance of each function needs to be assessed and the interaction each has on another must be considered to assure system function is unaffected. Take, for example, a changeover from a smaller bottle size to a larger bottle size. If the stated function of speed (bottles per minute) is maintained, it is quite possible a quality function (e.g., net contents, foaming, etc.) will suffer.
Select Applicable and Effective Tasks – Any manipulation of the equipment to convert it to run the next product inserts a potential risk to functionality. Eliminating unnecessary steps also eliminates an additional risk to performance.
Figure 1: Continuous improvement
The Changeover Process
Technically and specifically, an asset’s changeover encompasses all steps necessary to run the next product, from the last product unit from the previous batch to the first production product unit for the next batch.
There are four categories of changeover steps:
- Preparatory Steps: Steps occurring prior to the completion of the batch preceding the changeover.
- Cleanup: Removal of all materials from the previous lot, as well as all cleaning and housekeeping tasks.
- Setup: The physical conversion of the machinery to run the next product.
- Start-Up: The period of time after cleanup, setup and all other changeover tasks have been performed and the line begins producing, but before it has settled down into normal operation.
The proper sequence of steps in the process also must be taken into consideration. Optimizing changeover steps may require that steps in one category precede steps from the next category. For instance, the changeover parts for a filler may need to be removed and partially disassembled before it can be cleaned. Disassembly is a setup step/task that would be performed prior to a set of cleanup steps in this case.
Preparatory Steps: Includes any staging, inspection, inventory, stocking, or planning/coordinating.
Cleanup: These steps include:
- Closeout – All paperwork for the previous batch is completed. The product is weighed and accounted for and removed from the room/production line. Any waste or scrap is also segregated, accounted for and separately removed from the area.
- Actual Physical Cleaning Steps – These include any physical cleaning, whether light surface cleaning or more detailed master cleaning.
- Washroom Steps – These are any cleaning steps that are extensive, usually away from the production line and in a specifically designated/ designed cleaning room.
- Filter Replacement – Because filters generally contain residue from the previous batch, replacing filters should be considered as part of the cleanup steps. However, in some instances, it may be more appropriate to change filters during the setup or start-up steps.
Figure 2: Sequence of changeover steps
Setup: Setup steps contain:
- Disassembly – Before proper equipment cleaning can occur, the change parts most likely will be removed from the machine, cleaned and put in their proper, predesignated place.
- Preventive/Predictive Maintenance – Any PM/PdM work orders that are due and can be performed during changeover should be planned and scheduled appropriately.
- Change Part Replacement – All changeover parts are stored appropriately on carts, hooks, or other pre-assigned locations. Next product parts, which may be the same parts as the previous batch, totally different parts, or a combination of the two, are installed on the applicable equipment.
- Wear Part Replacement – Wear strips, belts, hoses, etc., are replaced.
- Setting Start-Up Parameters – This is done on the equipment’s control panel and the spin test is performed in two phases.
- Manual Steps – They involve rotating the asset by hand looking for interference and fit-up issues. Steps done via the control panel involves slowly increasing the speed with manual speed control.
Start-Up: These are steps that affect runability or steps to ensure the machine can input raw materials and output product. Speed and quality are not factors in these sub-steps, which include:
- Pre-Production – Produced product passes all associated quality criteria, but the machine is not yet at normal operating speed.
- Production – The press is running at normal operating speed meeting all quality criteria.
Once a specific changeover has been stabilized, meaning it can be performed over time repeatedly and consistently, a SMED process can be used to optimize the changeover.
Reduce Intrusion/Trauma: Begin with the end in mind. Evaluate whether a part needs to be removed at all. If removal is necessary, consider how it can be removed and reinstalled with as little impact as possible.
Reduce Variability: Serialize all parts so they can be tracked to each asset, by product and associated to any specific setup criteria, such as tooling used in a tablet press or an embosser/coder for differently configured bottle sizes for a liquid filler, for each changeover. Look for opportunities to inject consistency into the process. If a method can be developed where a part can be only slid in one way every time, regardless of the installer or conditions, then variability and compensation for it also will be reduced.
Optimize Time of Changeover: It is important to be as efficient as possible, but if a faster speed is achievable with no injuries or associated adjustments only 10 percent to 15 percent of the time, target a speed that is achievable 80 percent to 90 percent of the time, even if the new time is longer than the original time. An effort to reduce the changeover time always should be coupled with a performance measure, such as measuring the asset’s performance in the first hour after startup. The new time should be established not as a goal to beat, but as an indication that the step was performed flawlessly.
Eliminate/Reduce Impact of the Environment: Minimize or eliminate the use of water. It is hard to manage and the equipment always requires extra effort and time to dry. Also minimize or eliminate the use of air. Air just redistributes contaminants and only marginally cleans surfaces. Consider a vacuum, where possible, as a last resort. Factor in temperature differences between the machine and the change parts, especially where tight tolerances are critical. If possible,match temperatures prior to and during installation by allowing the parts to acclimate.
Calculate Separate Run Times/MTBF/FMEA for Each Product: Establish tracking processes that enable a differentiation of performance data based on product recipe, product size and machine at a minimum. Create reports that help predict functional failures. Establish criteria that clearly identify performance trends.
Minimize/Eliminate Non-Run Related Wear: Devise installation and removal techniques that minimize contact or abrasive conditions related to the parts or the machine. Ensure all parts have a specific location, such as a change cart or shadow board, that protects all critical dimensions. Train and educate associates in proper handling methods.
Eliminate Unnecessary Steps: Wasted steps add time and complexity to an already difficult event. Challenge previous ways of completing tasks. Combine steps and devise tools, jigs, bridges, alignment marks/indicators and go/no-go gauges to eliminate rechecks and inspections.
Externalize Non-Run Required Steps: Concentrate on pre-changeover steps, moving anything possible to a time prior to the end of the current production run. Move steps that can be accomplished after the next batch is running to a time outside the changeover period. Build in non-adjustable dimension settings and install alignment pins, clamps and lips/collars that allow precise placement of parts and reduce the variety of fasteners.
Rewrite the Standard Operating Procedure (SOP): Separate the steps into the changeover categories of preparatory, cleanup, setup and start-up. Sequence the steps to provide optimal use of resources and time. Allow for continuous improvement of the SOP and any other changeover documents.
Establish a Comprehensive Training Program: Provide background information that addresses reliability fundamentals, SMED methodology and the changeover process. Ensure participants not only understand mechanical principles, but also have the aptitude to perform complex assembly and disassembly tasks. Integrate on-the-job (OJT) techniques into the training program to solidify repeatable behaviors leading to consistent outcomes.
Institute or Expand 5S : Use sort, straighten, shine, standardize and sustain (5S) methods to include changeover parts, tools and equipment
All parts, tools, supplies, documentation and support devices must have their own location when stored, cleaned, inventoried and, if applicable, quarantined. All methods, practices, movements, etc., must be sustainable.
Reliability begins with a well setup machine. Mastering changeovers requires consistent execution of all its elements and leads to better performing equipment, less scrap, higher yields, less downtime, more availability and higher capacity. Well-running equipment is reliable and leads to better planning and production scheduling, reduced inventories, just in time (JIT) material deliveries and the elimination of manufacturing-based out-of-stocks. Consistent practices lead to predictable outcomes and process reliability.
- Henry, John. Achieving Lean Changeover: Putting SMED to Work. New York: Productivity Press, 2013.
- Gulati, Ramesh. Maintenance and Reliability Best Practices, Second Edition. South Norwalk: Industrial Press, August 2012.
- Deka, Amalesh. Single Minute Exchange of Dies (SMED). January 30, 2012
- Moubray, John. Reliability-Centered Maintenance, Second Edition. South Norwalk: Industrial Press, January 1997.
- Singo, Shigeo, translated by Dillon, Andrew P. A Revolution in Manufacturing: The SMED System. New York: Productivity Press, 1985.
Dan Miller has more than 30 years experience in a wide variety of maintenance and reliability assignments, including nuclear power, food & beverage and brewing. Dan is currently working with a Pharmaceutical client as a Principal Reliability Engineer and Project Manager for ABS Group. Dan also holds certifications as a Six Sigma Black Belt, as well as in lean and project management. He has a B. S. in Human Resources and a M. S. in Management. Dan is a U.S. Navy veteran, writer, photographer, and innovator.
Reliability through Optimized Setup and Changeovers Part 1