Just a minute

Single minute exchange of dies (SMED) is a technique to speed changeovers and cut lost time on machine set-ups to nine minutes or less - single minutes. Depending on the sector, this may be referred to as die changeover, tool change, clean-down time or any number of other variants - but every one of these represents lost production time. Chris Russell is an enthusiastic supporter of SMED. He is operations manager at Baxi Heating UK in Bamber Bridge, Preston. The 60,000m2 site employs 300 and it incorporates sheet metal manufacturing, a paint plant, aluminium and cast iron foundries and casting machining. Customers are all downstream final assembly operations or spares businesses within Baxi. Russell reports that SMED was introduced as part of a wider programme, which the business undertook with the help of a firm called Total Flow. "We have a large variety of products and wanted shorter lead times, and as a business we realised we needed to look at set-ups," he says. Batch sizes have moved from around 2,000 components to 250 or less. "Changeovers had to be a mile from where they were previously," states Russell. Single minute achieved The improvement programme included the traditional methodology: shopfloor operators were involved, videos of changeovers were made and workshops were held. "It was a classic process," says Russell, "but we took 60% of the time out without spending any money." And, after small investments in tooling and fixtures, Baxi hit the jackpot - "single minute was achieved". Russell explains: "We appointed a champion in each area. The vast majority of the work has been done in the automated and manual press shops." Baxi started the project 18 months ago and its first workshops worked well. Having identified the flow streams in the plant and conducted the workshops, the business could start to see the true benefits. "We have a 'measures dashboard' and every measure is going in the right direction." It's not all been plain sailing though and Russell warns against making assumptions. "In some areas, we were looking for the best case scenario and we made assumptions that a person would be available to help with the changeover." That wasn't always the case he admits: "We had to re-visit availability." The impact on the shopfloor at Baxi has been immense. Operators and setters can see the time allocated for changeover and now understand the implications of not achieving it. They understand about delivery and the knock-on effect downstream. Russell says this has given them far greater ownership. Should SMED be implemented at every changeover point? Dr Ted Hutchin thinks not. Hutchin works for I&J Munn, a firm that promotes the application of the Theory of Constraints (TOC). He explains: "We have been a Theory of Constraints consulting practice for many years. Before that, I worked on business improvement, bringing Japanese tools to UK manufacturers." Hutchin has strong views on SMED: "Doing it everywhere is a waste of money," he says. The thinking here is classic TOC: that is, working on the constraint is the benefit. The key is knowing what the constraint is, and using SMED on that particular piece of plant or process. Hutchin's experience echoes the results at Baxi: "Typically, we find a 60% reduction just by identifying the external and internal parts of the set-up, and doing the external first." Most people know this, he says, but they don't do it, although he believes it is "critical". Instead, firms try to concentrate on 'designing out' the set-ups, but this cannot happen in every case, so SMED is important. "It's the process of changeovers that's is really important," advises Hutchin. Mark Colvin runs Leanpal, a lean consultancy; he thinks that the term 'SMED' is often the first hurdle to its adoption. "SMED is perceived by many people to be jargon and potentially puts people off using the technique because they think it is only relevant to die changeovers." Colvin recommends using 'changeover reduction' as a phrase: it has more relevance for many industry sectors. He also agrees with Hutchin about the importance of the process: "It is by improving the organisation of the people doing the changeovers that companies get the biggest benefit - and it requires very little investment." Colvin has worked to apply SMED on a capacity constraint in a double-digit growth company, where "the time saving translated directly into increased sales and therefore profitability". Elsewhere, through better organisation, another business cut changeover times by 30%. Good results from seemingly simple, practical steps are common, he says. "What stops people is the mistaken belief that the bigger opportunity will come from the application of technical jigs and fixtures to speed up the physical changeover. Thinking this will take engineering time, money and redesign often acts as a barrier to starting the process." What tends to be the catalyst to prompt a business to look at its set-ups? Chris Ellins is managing director of Total Flow, the consultancy that worked with Baxi's Preston site. Ellins has spent much of his career focused on improvement, including time at the Kaizen Institute. He says a more general view is needed of the business, before jumping into SMED: "A business needs to understand its value proposition at the point of sale... all SMED does is increase responsiveness." If a customer wants something next day, but your business can only deliver in three weeks, for example, Ellins says businesses often just protect themselves by stocking more inventory. Actually, what they must really do is to work back upstream. "You need a better batch performance and better capability on set-ups. Then, you can understand in component terms how much inventory you want to bear." "Where life gets really interesting," he adds, "is when the internal/external process is deployed all the way through the process, for example to the back office." Part of lean In the drive to adopt lean, have manufacturers squeezed all the possible benefit from SMED? Leanpal's Colvin says: "Unless the lean manufacturing programme uses proper measures to identify the losses and wastes in the business and prioritise those accordingly, there is a risk that certain tools and techniques will be used just for the sake of it, or perhaps because the lean implementation people are experts only in those tools and techniques. A proper analysis of losses and wastes is required." This is normally achieved by value stream mapping (VSM). "If the VSM shows the machine is a constraint, and the measures (OEE) on that machine show excessive changeovers are affecting available capacity, then this will drive changeover time reduction activities." Colvin agrees with Hutchin that there is no point applying SMED to machines and equipment if the constraints lie elsewhere in the value stream. This is precisely what happened at SAS International's site in Bridgend, Wales. Paul Smith is engineering manager for the site, which manufactures ceiling systems and architectural metalwork. It's a growing business that employs 120 people. As the business moves from project to project, the bottleneck also moves, and the business has to reinstall what Smith calls its "set-up regime". One process is punching holes in steel coil, using tools with sometimes over 2,000 punches (shown left and on p18). "In punching, we have a set-up regime: as the bottleneck moves, the focus moves to the next bottleneck." The original set-up reduction programme was implemented five years ago. "All the operators and all the teams attended workshops. We educated the people on the shopfloor," says Smith. This brings a real sense of ownership, though he admits that this has drifted from time to time. "We've had to reinstall the procedures and methodology to keep it in focus." New software will help to identify bottlenecks and the company has used MAS Wales to help with its tooling set-ups. A final example proves the case for SMED. Mike Gibson, a project manager with MAS Wales, was recently involved with a successful SMED project that reduced changeover times in a 24x7 PET bottle plant "from 12 hours to around five and a half, with two further hours possible". The site in question is Amcore PET Packaging and it makes nine million 'preforms' a day from blow- and injection-moulding machines. The business had already embraced 5S and OEE, but market pressures revealed changeover times were a problem. "The key question was how quick could it be done? A MAS Wales practitioner went in and ran a two-day workshop to explain the principles behind the technique of SMED," says Gibson. The set-ups were observed and the SMED programme had dramatic results - cutting changeover times by 54%. This has delivered savings of £60,000 so far. So far, so good.