The best changeover is no changeover
Achieving effective changeovers should start with eliminating those that are unnecessary.
In a perfect manufacturing world, one would be able to dedicate production assets to one product, run that product continuously, and never, ever be forced to change to another product. If one could do so, this mode of operation would yield true world-class performance. Think of it—no constant struggle to reduce the losses that invariably occur as part of the changeover process.
Unfortunately, for most of us a perfect world doesn’t exist. Our markets are highly volatile, demand fluctuates, and inventory cost is too high to support dedicated production assets. Instead, we must be flexible and capable of running multiple products on one or more assets. We must do changeovers, but that does not mean that we must sustain unnecessary downtime and capacity losses.
While some changeovers are necessary, most plants make far too many. In a typical plant, it is not unusual to see production assets average two or more changeovers a day, often switching between fewer than three products. Just last week, I observed one asset change from one product to another, back to the first product, and then back to the second in a 24-hour period.
Achieving effective changeovers should start with eliminating those that are unnecessary. In a typical plant, at least half of the changeovers could be eliminated by adhering to standard products and effective production planning. When one evaluates the forcing functions that drive changeovers, two are dominant. The first is the number of orders received for nonstandard products or delivery schedules.
Too often the sales group commits the plant to orders that force production to react—often without standard procedures for producing the nonstandard product.
The second dominant forcing function is deficiencies in the production planning process. In too many instances, production planning—really scheduling—is little better than a clerical function. Little, if any, effort is placed on effective asset utilization, conversion cost, or the level of effort required to changeover. Instead, the activity is limited to plugging each order into the first apparent hole in the schedule without regard to impact on performance.
Effective production planning and scheduling are essential to sustainable best-in-class performance and the best means of eliminating the negative impact of changeovers. Always remember that the best changeover is no changeover at all, and that can only be achieved through effective planning.
Once all unnecessary changeovers have been eliminated, we must also improve how required changeovers are performed. There are seven steps that are integral to effective changeovers:
- Separate internal from external setup operations. External operations can be done without stopping the asset or production line or interfering with normal production. These tasks can be completed before shutting down for the changeover.
- Convert internal to external setup. Every effort should be made to convert as much of the changeover process as possible to external tasks. Every task that can be performed before shutdown extends the production and its resultant capacity.
- Create standard work, not generic functions or tasks. Standard work is the keystone of best-in-class performance—including changeovers. Leave nothing to chance. Implement step-by-step task descriptions, roles, and responsibilities that clearly define the changeover process. Train all involved and then enforce absolute adherence; compliance cannot be optional.
- Use functional clamps or eliminate fasteners altogether. Traditional fasteners are inefficient, require too much time to loosen and tighten, and introduce a significant risk of mistakes that too often result in difficult, prolonged start-ups. Every effort should be made to replace traditional fasteners with quick-lock clamps or fasteners. Effective use of functional clamps will reduce changeover time as well as eliminate mistakes.
- Use intermediate jigs and fixtures. The use of jigs and fixtures to assure consistent, repeatable setups is essential. A jig and fixture set should be created for each product type that will be produced and permanently located adjacent to the appropriate asset.
- Adopt parallel operations. To the extent possible, eliminate all serial operations or tasks. Safety cannot be compromised, but many shutdown, changeover, and start-up tasks can be performed simultaneously, thereby eliminating lost time as well as wasted motion.
- Eliminate adjustments. The extended need to make adjustments, especially during the start-up process, is perhaps the greatest source of scrap and lost production in the entire changeover process. Much of this need can be eliminated by standard work, jigs, fixtures, and mistake-proofing the changeover process.
The losses associated with changeovers range from 5% to 25% of total available production hours, and many can be eliminated. Elimination is not easy; it requires discipline and a coordinated, combined effort that includes sales, production planning, logistics, and all other functional groups. It’s not easy, but it can be done—if you are willing to do it.