SMED is an abbreviation of Single Minute Exchange of Dies. It is a method to reduce set up time. This method was developed by Shigeo Shingo in Japan and was applied first in the automotive industry. At one time set up times became a big problem at the manufacturing of pressed car parts like doors, bootcovers and so on. This meant a machine stop of about 24 hours when a press needed to be set up for the production of another part. By applying the SMED method the set up times were reduced to a few minutes. Nowadays the SMED method to reduce set up time is widely spread across the World and applied with success in different kinds of industry.
2 The goal
In the current market situation a company needs to respond quickly to customer demands to be able to compete with other manufacturers. Customers ask more and more for small lots. This means that the manufacturer needs to produce small series to satisfy this demand. This implies that more often the need exists to change set up of equipment, unfortunately with the production loss accompanied with it.
As stated in the introduction, the SMED method is a method to reduce set up time. By reducing the set up time the productivity of the equipment increases. This simply because of the shorter period the equipment is not producing products. This increased productivity can partially be used to change set up more frequently.
3 Definition of set up time
To avoid confusion about the meaning of set up time, the following definition is used:
Set up time = the time passed between the completion of the last product of the old series and the completion of the first good product of the new series.
During the set up actions are made in relation to:
- the change of tools,
- the adjusting of machine parts,
- the adjusting of machine- or process parameters,
The production loss during the start of the production is also part of the set up time. Except for the fact that the SMED method reduces the time losses, it also tries to search for an optimal set up of the machine and a way to avoid start up losses.
4 Who shortens the set up times with SMED?
In the center of the SMED method are the people that deal directly with the machine the method is used upon. Primarily the knowledge the operators have obtained in time is used. Other departments that deal indirectly with the machine concerned assist these people, for example the Technical and the Engineering department. They assist the SMED-team if changes to parts of the machine need to be made or designed.
Figure 2: The three steps of the SMED method
5 SMED, an overview
Figure 2 gives an overview of the SMED method in short. The method distinguishes three steps to reduce set up time.
5.1 The initial situation
In the worst case the initial situation is being characterised by unclear information at the working area, no standardisation of settings or work methods, unprepared activities and no order around the machine as a result of which the necessary parts, tools or measurement equipment get lost easily.
5.2 Step 1
The preparations of the SMED route are important. All set up actions are recorded accurately with the aid of a video camera. All the actions from the operators during the set up are described accurately and the time taken for each action is measured.
Furthermore, in step 1 all these actions are being looked at critically if these actions are to be done during the production stop (on line), or if they can be prepared during production (off line). During this it is also determined if the action is actually necessary or if it can be avoided. While making the preparations think of putting ready the tools and exchanged parts. In this step a complete overview of all the tools that are used during the set up is also made.
5.3 Step 2
The next step in the SMED route beholds the search for ways to make off line actions from on line actions. It is possible that making small changes to the equipment or working method can make some actions obsolete.
5.4 Step 3
In the third and final step the on line actions that seemingly are unavoidable are being looked at closely. During this solutions, often very creative, are looked for to shorten the time elapsed during these actions. In step three focus is mainly being paid to:
|Try to replace as many bolted connections by quicker alternatives. Bolted connections are mostly over dimensioned. There are cheap alternatives like snapfasteners with which the set up time can be reduced dramatically|
|2. Positioning aids: fixed positioners
|Often aids can be used to simplify actions. Think for example of fixed positioners to simplify the positioning of parts. Fixed positioners prevent endless adjusting|
|3. Standardisation of tools||Simplicity first. That is why the use of different tools needs to be limited as much as possible. This lowers the risk of loss of tools and eases the operations. An example is the replacement of different types of bolts with a single type as a result of which only one spanner is needed|
|4. Working methods||Looking critically at the working methods can often save a lot of time. The starting-point is: First Time Right. This means that an action does not need to be repeated or corrected any more. Also, performing the actions parallel with more than one operator can save a lot of time. This may demand for a little organization, but the time saved determines if the necessary organization is worth the trouble|
According to mr. Shigeo Shingo it is possible to reduce ANY setup time with 90% (!). And now the hammer… If you achieved this target, his law still applies….