Lean manufacturing techniques are being applied successfully throughout the construction industry and are especially useful in the shop. To improve your ductwork fabrication methods, consider these five suggestions.

1. Increase flow. To improve your shop’s performance, you want to increase throughput without adding more resources. The customer, your field crews or an external customer wants fabricated duct to install. The faster you can move sheet metal products through the shop and out the door, the more you will improve performance. Look for bottlenecks, what causes material to wait and not be fabricated.

Once you have spotted a bottleneck, here are some ways to address it.

  • Change capacity for that step or piece of equipment. In one shop, the transverse duct flange machine was the major bottleneck, but it may not require buying a larger or newer, faster machine. Instead, stagger when operators take breaks, so the machine is always running. Throughput improved.
  • Balance product flow from one machine/fabrication station to the next, so work in progress doesn’t build. When you have material stacked between stations, workers waste time sorting and moving the pieces around.
  • Reduce the time operators spend searching for tools and information and the time used to set up to fabricate. (See tip No. 4.)
  • The last option is to add equipment. This is the most costly alternative. Consider using older machines to offload easier fabrication work.

2. Set rules of release. Do not release jobs for fabrication until it is close to the need date. Fabricating early may result in having to stop the job in progress for rush orders. Even if the job is all fabricated at the same time, doing it too early requires it to be stored either at the shop or job site. The duct may be moved several times around the yard before being installed. This is waste and can result in damaged or missing duct.

Do not start ductwork fabrication when some of the material needed for fabrication is not available. Doing otherwise can cause you to shelve a partially fabricated job while waiting for special ordered parts. Time will be wasted waiting and then restarting the job. Partially completed work in inventory is waste. 


3. Reduce batch size. While coil lines control the parts being fabricated, you still do not want to fabricate large orders in one run. Making all the duct at one time when it will be installed over several weeks builds inventory usually at the job site and, as already discussed, is waste. Do smaller batches, such as a week’s worth of work or even less.

For the plasma cutters, operators try to optimize the metal cuts to save material. Coming off the cutting table, workers usually stack several pieces of unassembled duct together. This results in frequent sorting for downstream fabrication. Run your plasma cutter to get the most cuts on a sheet of metal to reduce scrap and then sort the metal cut pieces by each piece of duct. Move each set of duct through the next steps separate from the other sets. Do not batch the work by fabrication type.

Do not burn more jobs than the rest of your shop can process each day. Seek to maximize throughput through the entire shop, not just the plasma cutter.

4. Organize the shop to reduce “treasure hunts.” Workers in most shops spend much of their time searching for tools, parts and information. Use the “Five Ss” — sorting, simplifying, sweeping, standardizing and self-discipline — to get rid of clutter and unneeded stashes. Then identify where every tool and part should be located. Mark each location, so everyone can see where each tool goes and when it is not there. Put more frequently used tools closer to the point of use. Apply ergonomic principles to make it easier and safer to get and return tools. This is called simplifying.

A quick way to see if your organized shop is working is to use the 30-second test. Watch the shop workers as they fabricate. When they go for a tool or part, can they do it in 30 seconds or less? If more time is used, analyze the situation to find ways to reduce search time. (See “Five steps of mastering lean manufacturing,” April 2009 Snips).


Organizing the shop is important to improving throughput. Be careful to not get so caught up in sorting, color coding and organizing that you lose sight that the intent is to keep duct moving through the shop. 

5. Follow the “Five Rs”: right piece, right quantity, right time, right quality, right method. Many delays in keeping duct moving through the shop can be traced to a missing “R.”

To be effective in the shop, you need to measure throughput and on-time delivery — not measure tons fabricated per hour or per day. Learn from failures to meet deadlines and prevent bottlenecks in flow. Always seek to improve. Be different than your competition.

Dennis Sowards is an industry consultant and guest writer for SNIPS. His company is Quality Support Services Inc. and can be reached at dennis@YourQSS.com or (480) 835-6048.

For reprints of this article, contact Jill DeVries at (248) 244-1726 or email devriesj@bnpmedia.com