The value of lean manufacturing
Most duct-fabrication shops pride themselves on having a neat, clean and efficient shop.
But in many cases, it could be better, much better than they ever imagined and without major capital investments.
It can become “lean.”
The three ideas discussed within this article are:
Lean came out of manufacturing, in particular Toyota’s automobile production techniques. It has since found use in all types of manufacturing. One published report said 70 percent of all U.S. manufacturing plants have implemented some form of lean. Most duct fabricators are just starting to apply it. There are many lean tools and concepts and those most applicable to duct fabrication include the principle of “flow” and the “Five S.”
Lean seeks to add value to the product - value that customers are willing to pay for. Value is the opposite of waste, and lean makes war on waste. One key concept of lean is to make value flow.
The customer does not pay for a sheet or coil of metal. Many customers could purchase the sheet metal for as much or even less than duct shops can. But customers aren’t in the fabrication business; they pay for fabricated duct installed to serve their needs.
Sheet metal is only of value when it is fabricated, installed and working. Value is added when the metal is being cut, welded, clamped, beaded and bent. When the physical nature of metal is changed, value is added. When nothing is happening to the metal, such as when it is waiting to be put on the plasma table, or to run through the transverse duct flange machine, it is waste. Waiting is waste. Time is money. You want to keep the metal flowing through the shop and delivered to the installers.
Many times, when contractors study their shop flow they discover that the sheet metal pieces are spending more time “lying in wait” than being fabricated. In one company studied, only about 10 percent of the steps involved in fabrication were value added. There is much waste to attack.
The way to improve flow is not to work harder or faster, but to redesign how the process works. Quit doing work in batches where all the pieces are moved through the shop in groups. Instead, move one piece at a time through the shop until completed. When work is done in batches, most of the pieces are left waiting. It may seem efficient to batch work, but it actually isn’t.
One contractor recently shared this story:
I was in my office about an hour ago and John comes bounding in with this look of ‘wow’ on his face. I ask him what was up and he said come out to the shop - lean is happening and I can see it. What he meant was he could finally see all his work really happening, all the pieces were working. The field guys had ordered the metal and before noon he had already put out seven orders for different jobs. He said the flow was perfect: a job got burned, came off the table, moved from one station to the next, and never stopped for seven different orders. I went out to the shop to observe and the best part of what I saw was John’s enthusiasm for the process. It was way cool.
Reducing batch size really works.
When considering shop layout, keep these key ideas in mind:
- Organize the processes by product, not function. Try to locate equipment in the flow of fabrication for the types of duct you do. Do not locate all the brake machines in one area, but where they are needed in the workflow.
- Put machines close to each other that follow in the work process. The cutters need racks to feed them, the beader to follow the main cutter, etc.
- Design the layout for product flow, not for storage tables or finished duct.
- Design for the majority of the products you produce, not the exception or special cases.
- Look for bottlenecks. One shop found a bottleneck in insulation due to cramped space. They rearranged the process to better accommodate the work.
Another tool for making a shop Lean is Five S. This tool was explained in a previous article (see “Getting in shape,” April 2009 Snips). Five S is a way to organize the shop’s tools, material and equipment so workers have what they need, when and where they need it. This eliminates many “treasure hunts” that happen all day in the shops. Locating the tools used in each machine right next to it or even on it, is a great way to reduce searching time that equates to duct waiting, aka waste.
Organizing the shop is really the second “S,” which stands for simplify. The first “S” should be done first for a good reason. It is “sort” and means to sort out all that is necessary for fabrication from that which is not. Most shops have materials and tools lying around that clutter the work area and are not needed. If you haven’t used it in the last year and don’t have a specific use upcoming, get rid of it or at least move it out of the main shop work area.
One shop had duct stacked on one side that was from a job completed eight years ago. They had kept it just in case they might have a use for it. They had even moved to a new shop during those eight years and had moved it, too. Clutter is waste; get it out of the way. Once one has sorted out the good from the waste, simplifying is much easier to do.
Finally, go watch the work. In lean language this is called going to “gemba,” a Japanese phrase that means “where value is added” and watch how the work flows or doesn’t.
A simple tool is a “spaghetti chart” (see “Back to school,” May 2009 Snips for an explanation of terms). Get a layout map of the shop floor and follow the duct fabrication flow as it actually happens - not what you think is happening. Draw lines on the map showing where the workers actually walk as they do their work. Use a different-colored line for the actual flow of material.
It is called a spaghetti chart because after mapping the fabrication flow through the shop, it usually looks like spaghetti was tossed on to the map with lines going everywhere. Once the map is done, start asking why the workers have to walk around. It is usually because they need a tool or part that is located away from the work area. Apply Five S to eliminate the problem.
Duct shops can improve the speed of how work is fabricated without sacrificing quality. There are many lean tools to apply. Try these for a start.