Southern California Section of the Society of Plastics Engineers
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This is the first part on a two part series. This article will cover the benefits of SMED and
the key principle. The next article will cover step by step implementation of SMED.
Lean Manufacturing is a production philosophy that emphasizes the elimination of waste: Wasted motion, scrap, wasted idle time, wasted labor, etc. There are many tools and techniques that are used to achieve a “lean state.” One of these is SMED – Single Minute Exchange Die. The idea behind SMED is to reduce the set up time/changeover time or said more completely the amount of time that it takes to turn around a piece of equipment from the production of one product to the production of another product. By streamlining this process, waste is eliminated and machine utilization increases.
How powerful is this? One of my students as part of a school project worked with a blow molder specifically to reduce changeover from 18 to 6 hours, then end result was down to 3 hrs. At 20 bottles a second X 15 hrs time saved X 3600 seconds/hour =1.08 million bottles increased production per setup. Benefits: Increased production AND less
warehousing (specifically the space for 1.08 million bottles!).
The benefits of streamlining the changeover for a different product are many and depending on the company the benefits chosen will vary. Some examples:
1. Reduction in the time from end of one product to beginning of next product. This increases the machine
utilization time. For instance, if a setup cycle can be reduced from 3 hrs to 30 minutes, that makes the machine
available for 2.5 more hours of production which can result in either more sales, or reduce the need to purchase
2. Reduction in direct set up labor. By eliminating unnecessary tasks it will take less time for the setup
technician to get the equipment and tooling ready. This provides a direct reduction in manpower. Have you ever
seen people looking for the right length hose or jerry rigging a different length hose while the machine is idle?
3. Reduction in skill level for the changeover. Often when placing tooling it is necessary to perform precision
adjustments. However, many of these adjustments can be replaced or speeded up by having a standard setup.
For instance, when injection tools are replaced on the platens, prespecified stops can be placed permanently
to lean the tool against them. Different sized tooling? Set the stops to the largest tool to be run, and then use
spacing blocks to locate smaller tools. On the screw and barrel side of things, the equivalent is done with a set up
sheet (or program). No need to dial in the process from scratch or memory each time.
4. Improved shop organization. In order to achieve faster change over times it can pay to dedicate set
up tooling for a specific tool. The advantage is a faster and easier setup, however the obvious disadvantage is
increased cost in tooling inventory. This may make sense for a job that gets changed frequently (weekly) but
clearly not for a job that is run once a year. For this other job a well organized supplies room will be more than
adequate. However, a list of all necessary items (tools, couplings, hoses, etc.) and a tray to collect all necessary
items prior to changeover is needed.
5. Faster turnaround times and improved customer responsiveness. That is, it is not necessary to wait for long
runs of jobs to finish, it is possible to economically make smaller batches.
6. Lower in process and finished goods inventory
These are just some of the benefits that can be achieved with SMED implementation, but there are others.
While there are many benefits, there are also costs to the implementation of SMED. They go from very low to a
significant expense. It is necessary to analyze each situation and determine whether the required investment
for improvement is warranted. For instance, the first step of SMED consists on observing and analyzing the
changeover process. If in this process it is found that there is a significant amount of wasted time such as that
required to look for couplings, hoses, etc. a quick inexpensive improvement could simply be organizing all of these
supplies. A second inexpensive step would be to separate the ‘internal’ (on-line) and ‘external’ (off-line) functions
of the changeover. For instance, actually removing a mold from an injection press requires production to stop,
this would be an internal task. Gathering tools and supplies for the changeover can be done while production
is running, this would be an external task. Simply organizing changeovers in this manner will save valuable
time. This separation between internal and external tasks is the main element of SMED. Other more extensive
changes can be performed, such a getting a dedicated crane for each machine, but in most cases this would be
unnecessarily expensive an unwarranted. In all cases an analysis of costs vs. benefits needs to be performed.
In the next article, an example of how a changeover can be improved by using SMED techniques will be presented.
Any questions or comments please contact me at email@example.com.
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