From two-slice toasters to Boeing jets, tools and dies are omnipresent staples of manufacturing. And where there are tools and dies, there are idle employees and lost production.
Three decades ago, Dr. Shigeo Shingo largely solved this problem with the introduction of single-minute exchange of dies (SMED), a lean manufacturing technique that was designed to reduce the amount of time tooling and die changes require. Single minute means a time period less than 10 minutes – a single digit time. Dr. Shingo's innovations continue to influence the automotive and other industries.
"SMED is about an attitude of continuous improvement and never becoming complacent with the status quo," said Bob McClintic, aka Dr. Die Cast.
Tools, dies and molds are fundamental to manufacturing. Tools are used to cut and form metal and other materials. Dies are metal forms used to shape metal in stamping and forging operations. Molds, which are also of metal, are used to shape plastics, ceramics and composite materials. Both low-pressure casting and high-pressure die casting use steel molds called "dies" to produce products from automotive transmission cases to aluminum wheels.
In manufacturing, tooling and die changes take a considerable amount of time. While tooling or die changes are being made, production lines are shut down. This lost time and associated costs must be covered. In addition, the downtime for changing tooling or dies impacts other production decisions. The more time it takes, the longer the production cycle. Operations personnel increase lot sizes and run longer in order to reduce the impact of setup costs.
There are advantages to having the tool or die out of the machine that may not be apparent at first glance. Molding, stamping, tooling and cutting are processes that all produce soils that can affect the performance of the process to make quality parts.
According to Mike Bangasser of Best Technology Inc., the best time to clean the die or mold is as it comes out of the machine – not when it's time to try and re-install it in the machine.
"Cutting fluids, slag and other particulates will accumulate on the surface of a mold or die during normal usage," Bangasser said. "Especially in precision applications, it's critical to clean the working surfaces to ensure correct tolerances are maintained. Letting soiled tooling sit on the shelf is like letting your dinner dishes, pots and pans sit on the counter overnight before trying to wash them."
Tool and die companies, which are typically small businesses staffed by skilled craft workers, make it possible for their customers to manufacture innovative products, from auto parts to household appliances to fighter planes. High-volume tool and die shops have incorporated "quick change" fixtures to reduce setup time and increase accuracy between machining processes. However, when tool and die changes take too long, complications arise including higher manufacturing costs, lower quality levels, excessive test runs and pulling people off task to find tools.
By contrast, employees at Honda's plant in Anna, Ohio, are superstars when it comes to die changes, completing changes on 3,500-ton die-casting machines in 15 to 20 minutes. Others may take up to four hours to perform similar operations.
With SMED, increased production is achieved without purchasing new equipment or hiring additional employees. In addition, because SMED reduces the number of items that must be produced in a production run, the production line becomes available to produce other products.
Because SMED reduces changeover time, it becomes economically possible to have smaller production runs. This provides a number of advantages:
- Less capital is tied up in inventory and less warehouse space is needed.
- Less work in progress, reducing costs further.
- The ability to quickly respond to market changes.
- Improved quality and less waste. Defects can be identified and the problem corrected without large quantities of defective product being carried in inventory.
- Product innovations, which provide a competitive advantage, can be brought to the market sooner because inventories of the older product are smaller and will be sold off quicker.
Using SMED to reduce changeover times provides a number of benefits that go right to the bottom line, including improved productivity and greater equipment utilization, but don't expect instant results.
"These kinds of transformations take planning," said Steve Udvardy, director of research, education and technology for the North American Die Casting Association. "Management is often so busy putting out fires with concerns about detracting from what we're doing today to think about how these kinds of shifts will make things better in the long run. Upper management has to set the tone, take the time and discipline to help foster a culture of change and understand that there will be hurdles to overcome."
Not Just Tools and Dies
Being in tune with SMED is like being the producer of a Broadway show. As everyone knows, the show must go on – even if you have to rehearse a few times with all the necessary players and tools in place.
"The No. 1 way that SMED changes human behavior is making one more conscious of waste," said Udvardy. "If you can reduce eight turns of a wrench to one-quarter turn of a wrench to tighten a clamp, then that's progress."
SMED Tools and Visual Communications
Clear communication is vital throughout this process. Checklists should be provided to ensure everything is ready before the shutdown begins. Procedures should be readily available. Safety warnings and information must be prominent, including labeling tooling as "ready to set" or "not ready, work order incomplete."
Utilize your smartphone's video camera to record details of all team and changeover activities. Capture activities from both the operator and helper sides of the machine. Record elapsed time. Install a sign that reads, "Cameras are recording work for learning purposes."
Use stop watches to record incremental changeover activities with timelines. This information can be helpful to measure time data in the changeover process with people, machines and equipment.
Create and post charts and graphs for recording data. Correlate activities on the Y axis and incremental time/elapsed time on the X axis. Capture data from team members and record and share with your teams. Break activities into specific actions/activities such as "move die to machine, align die with keyways, clamp die, connect hydraulics and/or electrical switches." This will allow you to identify areas where more practice is needed or simpler methods can be developed.
Like all changes, achieving proficiency in SMED is not an overnight exercise. Instead, expect a few bumps in the road. Training, review and reassurance will be necessary. Help your team by communicating key SMED messages with signs and labels that can be easily updated and relocated.