Quality Through Innovation

Inventory stocks create (unnecessary) high costs. Aggravating this situation is the increasing market demand for more customised products, fuelled by reducing life-cycles and never-ending innovations. An order not fulfilled immediately is frequently lost to a faster responding competitor. Stocked goods become obsolete very quickly. All of these, in addition to inventory cost, make stocks expensive. To obtain a competitive advantage, customer requests must be satisfied quickly. These requests are increasingly for customised products. Lot-size reduction and the need for flexibility requires that manufacturers master quick changeovers.

Often, changeover is carried out when the final part from a production batch is processed. The equiment is stopped and changeover operations are carried out. The machine commences production again only after the completion of trial runs. Usually no standard method is defined, procedures and checklists do not exist, and there is no teamwork, which means that several operators share these operations. In many companies, large changeover times cause productivity losses. Increasing the lot size is a tempting solution to changing-over less often and thereby minimise global loss. This has led to the adoption of the so-called economic ordering process.

SMED is a method for systematically achieving set-up time reduction to a quantified target. Single Minute Exchange of Dies means that dies are exchanged in less than 10 minutes. The phrase 'Single Minute' is because the set-up time is of the order of a single digit.

SMED involves four steps. Initially the operations that must be done while machine is stopped (called internal set-up (IS)), must be discriminated from those that could possibly be done while the machine is running (called external set-up (ES)), and from useless operations.

To realise SMED, firstly, the involvement of everyone concerned must be obtained. Operators have crucial knowledge of processes, machines, and their jobs. They are more likely to know the weak spots, and can point them out. In the future these operators will be required to comply with new rules, and they would accept rules more easily if they have helped in creating those rules.

Analysis of data will probably reveal the need for 5-S action, in order to make tools and equipment handy, or a new workshop layout to avoid or minimise useless motions.

If changeover is not standardised through formal documents, the creation of a procedures or operations manual will help avoid mistakes and the need for controls and post-operation rectifications.

In this step, it is important to distinguish what must be done while the machine is stopped (internal set-up), from what can be done while the machine is running, before the changeover occurs (external set-up). The questions to be answered are: Can what is actually done when the machine is stopped, be done in advance ? Is it really possible to convert internal set-ups into external?

Some external operations are actually performed like internal ones because of old habits or simply because of ignorance of this principle. These are to be converted immediately. Activities that can be completed prior to stopping the machine are generally the preparations for a set-up; such as tools, parts, material, pre-assemblies, presets, preheating, preparation of working instructions, etc.

An attempt should be made to suppress these either partially or even totally. Turning movements should be minimised as they involve several grasp-release motions. All assembly operations should be 'fit-at-once', single-motion operations. Blocks, jigs, and templates should be used. Tools, screws, nuts, etc. should be standardised.

For every screw, regardless of its length, it is always the last turn that tightens and the first that releases. This means that a tightening with a single turn is as efficient as screwing 10 turns, but much faster! This is also true for nuts. There are fastening solutions without screws and bolts, because even if screwing turns are reduced, they tend to create some confusion because of the different sizes involved. Also nuts and bolts have the habit of falling into the worst possible places ! Other examples of simplifications are U-shaped washers, quarter-turn screws, U- shaped grooves, magnets, plugs, and cam and lever tights.

Standard values should be fixed. An attempt must be made to find adjustment-less methods through physical means, like stoppers and blocks. If necessary custom-made tools can be designed. The aim is to minimise the contesting need for tools as far as possible.

The best example for this is a racing pit. In an SMED action for an electronic automatic insertion machine, one operator sets up everything in front of the machine, while another feeds components at the rear. They do not disturb each other, and safety devices prevent the machine from starting as long as the operation is not complete and the covers are not back in place.

Increasing workshop staff is not recommended as long as a trained 'relief' person is available, who can help during changeovers.

The set-up must provide for minimising the requirement of trials and controls. The more formal and systematic the job, the less drifts there are to check. Such a set-up will prevent omissions and mistakes. Using fool-proofing devices like Poka-Yoké, or even automation, enables set-ups to be done in a standard way each time. The use of checklists and involving operators in the design of operations is a good way to generate respect for procedures and a kind of discipline.

Gains through SMED are often tremendous. Getting more usable time on a machine or process not only improves yield, but also helps in postponing or even cancelling needs for capacity investments.