Five steps of mastering lean manufacturing
Getting in Shape
So-called “lean” tools came out of manufacturing. The best-known example is probably Toyota’s automobile production techniques.
At first glance that may seem not very applicable to the many sheet metal shops that perform custom work. But Toyota Motor Corp. started its lean journey in the 1950s when it had only one manufacturing plant to make several different types of cars. This forced it to focus on quick-changeover techniques and better ways to run machines.
People who work in sheet metal fabrication shops can learn much from Toyota and others who have applied lean techniques. Here are some examples.
Apply the “Five Ss.” If you are not doing these five things, you are not really doing lean manufacturing and missing valuable improvement opportunities.
The Five Ss are actually “S words” in Japanese. When these words were brought to America, they were given English names. Depending on whom you talk to, the words may differ slightly. Here are the words used by Boeing Co.:
Sorting means to go through a designated work area to sort out the necessary from the unnecessary.
Necessary is defined by frequency of use. If you don’t use an item at least annually, it’s probably not necessary. Items that are necessary are kept and all the rest are disposed of, recycled or returned. Sorting is fun; it feels great to get rid of stuff.
Simplifying means to put everything, determined as necessary during sorting, in a designated place and mark it.
This is the critical step in eliminating waste that happens when employees in the shop are on “treasure hunts.” Not only is a place established for every necessary item but also its actual location is based on how often it is used. The items used most are located closest to where they are used. Those used less often are farther away.
Sweeping means to physically clean up the work area and to deliberately pick up all parts and material that are out of place and return each to its assigned place as defined in simplifying.
Standardizing means creating standard ways to keep the work areas organized, clean and orderly and to document agreements made while implementing the Five Ss. It means to standardize the tools, color codes, shadow boards, etc. used in the shop.
Self-discipline means following through with the Five S agreements. If we don’t maintain the changes made, you will not “maintain the gain.”
The Five Ss help you better operate machinery. Everyone wants to have all tools, gauges and parts used for each piece of equipment in a designated spot to avoid having to search for them. Less time searching means more time producing.
Time is lost when you have to change the equipment to run a new piece. Lean offers a very useful approach to reduce change over time. It’s known as quick changeover. It is similar to how pit stop crews quickly handle racecars when they are in the bay for refueling or a tire change.
Here are some other basic steps used to reduce setup times:
1. Separate work done while the machine is not running from work that can be done while the machine is in operation. Work that must be done with the equipment stopped is called internal setup work and tasks that can be done while the equipment is operating are called external setup work. Handle the two types of work differently.
- Reduce external setup work by applying the Five Ss. Make sure everything needed is in designated places and located based on frequency of use. Have every tool and material ready so that when the machine stops, everything is ready to go with the next piece.
For example, one shop built a small cart with fixtures to hold the dies for changing the size on a hydraulic air brake. This reduced the need for manhandling the dies into place.
- Reduce internal shop setup work by marking adjustments so new pieces can easily be found; by building fixtures or molds to set in place for the various sizes of fittings; by using base plates where various sizes are accommodated; and by using standard parts.
- Make sure shop workers know their assigned responsibility once the machine is stopped.
- Do parallel operations where possible.
3. Look at large blocks of setup time and use employees to brainstorm ideas to shorten them.
Think of a pit crew waiting for a racecar. The crew has the tires in place ready to replace used ones. The fuel nozzle is in the right spot to reach the tank. Each crewmember has an assigned task to do. When the car comes in, everything is close by so no time is used searching for it. Each crewmember has assigned tasks and does them in minimum time. Pit crews take pride in taking the least amount of time needed to turn the car around and get it back out on the track. They are also always seeking faster ways to do the tasks.
You can apply the same ideas to a tool change in the sheet metal shop to reduce wasted time.
One company analyzed how it operated its burn table. It was already running two shifts and was not keeping up with the workload demands. Officials found ways to do a quick setup for each job, allowing them to run more of them. Actions they took:
- The burn table operator was able to use an apprentice to clear off the table while he was encoding the next job.
- The apprentice also helped stage all material so it would be ready to be put on the table once it was ready for the next job.
- They would have nozzles ready to change for the upcoming job. They cleared off all unneeded scrap material near the table, giving more walk space. They moved some racks of specialty metal closer to the use area. They put tools needed at the table in an easy place to reach and the location was marked for each tool.
The last - but maybe the most important - tip is for the shop to best serve the install crews even if it means some inefficiency in the shop.
An example of the wrong type of thinking was a sheet metal shop that fabricated the duct for 32 air-handling units being installed on a plant roof. The shop thought it most efficient to fabricate and ship each duct piece for all units before changing the machineries to fabricate the next piece. This was good for the shop, but caused much wasted time for the crews who had to keep going back to each unit to install the next piece.
Taken as a whole, the install process was inefficient and cost more crew time than it saved in the shop. Fabricating all the pieces needed for each air handler would have been more productive for the crew, and would have saved money on the whole job.
Toyota does not call its efforts “lean” or “lean manufacturing.” Efficiency experts Jim Womack and Daniel Jones coined that term as they described Toyota’s unique way of doing and improving work. For many years, Toyota did not call its continuous improvement efforts any thing. It has now become known as the “Toyota production system.”
For more ideas on how to improve shop productivity, see “Look out below” in the June 2008 Snips.