Changeover greatly affects the reliability of the asset 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, as well as 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 manufacturer (OEM) designers and aftermarket businesses have eliminated many of the assembly fasteners, replacing them with revolutionary clamps, slides and twist locks.
However, efforts to reduce changeover times can conflict with setup consistency and repeatability. Achieving a goal of two hours for a filler changeover, for instance, may be cause for celebration, but if the accomplishment is infrequent or, worse yet, based on unique shortcuts, the increase in variability can lead to hours of line adjustments and associated reduced line speeds and throughput.
The focus of this article is on the effects of setup and changeovers on asset reliability. From the impact of flexible OEM designs on endurance to the details of properly written setup and changeover standard operating procedures (SOPs), the “trauma” of changing over a perfectly running production line to produce the next stock keeping unit (SKU) on the production schedule can lead to premature failures, increased quality defects, exposure to safety risks and even operator fatigue. No organization seeking to have a world-class enterprise asset management (EAM) program can succeed without fully understanding and refining their setup and changeover process.
Reliability: The probability that an item will perform its intended function for a specific interval, under stated conditions. – MIL-STD-721C
Failure Mode and Effects Analysis (FMEA): A technique used to examine an asset, process, or design in order to determine potential ways it can fail and the potential effects of that failure, and subsequently identify appropriate mitigation tasks for the highest priority risks.
Changeover: The total process of converting a machine, line, or process from running one product to running another.
Achieving Changeover Sustainability
Equipment reliability during each production run begins with a consistently executable and sustainable changeover method. Since reliability is so dependent on highly successful changeovers, the reliability team needs to drive the proper development of each step, the step sequence, equipment modifications, support systems, comprehensive training and the deployment of associated world-class best practices.
Changeover is a reliability function directly affecting overall equipment effectiveness (OEE):
Availability – Improved changeover techniques (e.g., single-minute exchange of die (SMED) approach) will reduce actual changeover times and increase the time equipment is available.
Performance – When changeovers are sustainably consistent, higher throughput is attainable.
Quality – Properly executed changeovers reduce/eliminate initial start-up “running” adjustments and lead to less scrap and outof- spec quality issues.
Changeover Effects on Reliability
There are six elements that influence how well or how poorly a changeover program will succeed. They are: degree of intrusion; environmental impact; transformational impact; equipment design; SOP or written procedure content; and training.
Degree of Intrusion
Changeovers are intrusive and traumatic to any piece of equipment being converted from running one product to running the next product on the production schedule. Well performing equipment is suddenly shut down, cleaned, stripped down, cleaned again, new changeover parts installed or parts reinstalled and the equipment is then started up. Hopefully, there are few running adjustments. Most of the time, however, numerous adjustments are made until the system regains its normal operating throughput.
Environmental factors, such as temperature (e.g., cooldowns), moisture (e.g., cleaning with water and chemicals) and air speed (e.g., drying with plant air), change how the equipment behaves. In the changeover transition, these factors need to be accounted for and compensation for their effects needs to be an integral part of the changeover process.
When a product’s specific changeover parts are exchanged with parts specific to the previous product, a transformation of the equipment occurs. The new setup can give the asset a different personality. In a normal maintenance event (e.g.,corrective or preventive maintenance) where old, worn and broken parts (e.g., wear strips, bearings, etc.) are replaced with new parts, the asset is restored to like new status. The asset regains its intended performance characteristics, which are maintained until the next scheduled maintenance.
But change parts are not usually new parts; they are most likely used parts that are swapped out over and over again. A changeover requires the meticulous removal of the previous change parts, to be used again the next time the product is run, and installation of previously used parts to run the new product. Three factors affect transformational impact: mean time between failure, dimensional diminishment and availability components.
Figure 1: P-F Curve
Mean Time Between Failures (MTBF):
MTBF is normally calculated based on total run time of the equipment. Seldom, if ever, are separate MTBF calculations performed based on which product is being run. Because of the variability in change parts’ construction and design, each set (designed for a specific product) will behave and fail differently. Therefore, any key performance indicator (KPI) tied to a given asset should be tracked by product run on the asset. Product subcategories are then averaged to reflect the total MTBF for that asset. In most industries, the production/manufacturing departments already track and evaluate each product’s throughput for performance and budgeting improvements. It only makes sense, then, for the reliability team to track MTBF by product to help identify changeover improvement opportunities.
Dimensional Diminishment or tolerance degradation:
Unlike a new part replacement where a dimensional reset on the equipment (like new) occurs, change parts are removed and installed numerous times over their life. There are three types of wear affecting dimensions and performance on a changed part: Normal Running Wear, which is predictable and based on run time of the equipment with applicable change parts installed; Replacement Wear, which is nearly unpredictable and based on the frictional factors of sliding a part into and out of place, bore wear for alignment pins, thread wear for bolts and fasteners, and widening of slots over time; and Handling Wear, which is unpredictable and preventable wear and damage due to transport, storage and cleaning of change parts.
Availability is defined as the probability that an asset is capable of performing its intended function satisfactorily when needed and in a stated environment. Availability is affected by the ability to precisely replicate the performance-related conditions achieved during the last run of the product now to be run. The factors include dimensional adjustments, parameter setup and warm-up/ break-in time.
Equipment design must factor in the flexibility of the equipment to run a wide variety of products. Size, raw materials and ingredients, process and cure times, scrap factors and post-process requirements (e.g., embossing, coding, etc.) are all taken into account. To construct production equipment meeting multi-product applications, the OEM must optimize all the dimensions and build change parts that fit within those dimensions. The end result, even under perfect conditions, is a machine that runs a lot of different products, but sacrifices throughput and possibly yield when compared to a one size, one product version of the equipment.
Changeover consistency needs to be maintained through guidance found in well-written SOPs. The changeover SOP not only needs to be detailed enough for the newest member of the changeover team, but also relevant enough to the most seasoned participant. Steps are written to the level of detail necessary for first-time readers, but simultaneously crafted to allow effective perusing when familiarity is attained. Consistent SOP execution leads to sustainable and repeatable outcomes.
The biggest influence to consistent changeovers is the training program. Training establishes the basis by which participants align their perspectives to accomplish the task at hand. Proper indoctrination for new members allows them to contribute to the team without an interruption in momentum. Once aligned, all participants achieve sustainability in changeover execution.
Figure 2: Continuous improvement
Failure Mode and Effects Analysis and Its Application in Changeover
In addition to the normal component failure analysis, such as drive motor failure, coupling degradation, gear wear, backlash, etc., the equipment also needs to be evaluated. This entails each product’s setup and its impact on non-changing components; the probability of failure for each change part and the impact of any positional factors (e.g., installed backwards or upside down, clamping force variance, loose parts, etc.) affecting them; the probability of failure based on fastening mechanisms (e.g., bolts, clamps, alignment pins, etc.); and the probability of failure due to non-extracted setup tools, alignment jigs, bridges, go/no-go gauges, etc.
Each task/step in the changeover process needs to be evaluated to determine its risk factors relating to functional failure or its potential impact on product quality or throughput. For example, if the adjustment of the discharge rail is too high for the next product, the discharge transfer/ conveyor can be damaged or easily cause a jam.
A potential solution may be to add a flexible or self-adjusting rail that would then eliminate an adjustment step. Where critical parameters are identified or the failure risk is higher than acceptable, inspection techniques and fail-safes must be included in the process.
In the next issue of Uptime magazine, this topic continues with a more detailed look at:
• How reliability centered maintenance (RCM) principles relate to changeover activities.
• The changeover process and steps and sequence factors.
• Applying SMED concepts to continuously improve changeovers.
1. Singo, Shigeo, translated by Dillon, Andrew P. A Revolution in Manufacturing: The SMED System. New York: Productivity Press, 1985.
2. Henry, John. Achieving Lean Changeover: Putting SMED to Work. New York: Productivity Press, 2013.
3. Deka, Amalesh. Single Minute Exchange of Dies (SMED). January 30, 2012
4. Gulati, Ramesh. Maintenance and Reliability Best Practices, Second Edition. South Norwalk: Industrial Press, August 2012.
5. Moubray, John. Reliability-Centered Maintenance, Second Edition. South Norwalk: Industrial Press, January 1997.
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.