Now more than ever, your sheet metal shop operations need to be lean in order for you to get the most out of your socially distanced workforce. But when it comes to lean, how do you separate fact from fallacy? Here are a few tried and true pointers published by SNIPS from Dennis Sowards, an industry consultant and author of the research book “Thinking Lean - Tools for Decreasing Costs and Increasing Profits.”
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, simplifying, sweeping, standardizing and self-discipline
Some of these words can broadly apply to all factory operations, while others take on new meaning in a sheet metal shop.
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.
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, and do parallel operations where possible.
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 anything. It has now become known as the “Toyota production system.”
Sheet Metal Shop Efficiency v. Productivity
There are many myths about how sheet metal shops can improve. Many of these are built on the faulty assumption that contractors want shop efficiency. Most don’t. They want shop productivity, which is not the same as shop efficiency. It is more than just definition differences; it is about understanding the basic differences of how to run operations.
This article discusses ideas and topics including:
Efficiency is the rate of using resources. Productivity is the rate of producing something (output) compared with the resources consumed. It could be defined as effectiveness divided by efficiency.
You always need to look at the productivity of the whole shop and field workers, not just a single operation. If one operation is more efficient at the expense of others, the total is usually less productive.
“Lean thinking” looks to reduce waste out of processes such as duct fabrication. Being efficient in part of the fabrication process can lead to additional waste elsewhere. But there are the things to keep in mind and the things to eliminate when it comes to sheet metal shop efficiency.
Here are six myths debunked and discussed.
Is Faster Always Better In A Sheet Metal Shop?
Equipment sales staff and some fabrication experts push the idea that if you buy a newer and faster machine you will make more money. For example, one person suggested that replacing a 300-inch-per-minute plasma cutter with a 3,000-inch-per-minute laser cutting machine would create a huge increase in metal-cutting efficiency.
The statement is absolutely true, but shop productivity is not just about metal-cutting efficiency. It is about getting duct through the entire process. A machine may cut faster, but if all it does is pile up metal waiting for the next tool, it will not increase productivity. You may be better off using the slower - and already paid for - machine. Faster is not necessarily better.
‘Pay’ For Your Most Expensive Machine
One shop would run its plasma cutter to near 100 percent capacity to justify its expensive tool. High utilization seemed to be the most efficient operating mode. The reality was that the high use caused jobs to pile up on all the available tables while waiting to move to the next operation.
This would max out the available tables and no work would move until the jobs were processed. This shop found out that using the plasma cutter at a lower rate to match the ability of the rest of the shop was actually more productive.
More space is better
Shop workers often feel they lack space and need a bigger facility. While more space may give the appearance of more productivity, it usually works in reverse. No value is added to the metal when being transported to another station. This is waste and when the distance increases between machines, the waste also increases.
In some of the most efficient shops, working areas are tight. They meet all safety requirements for working space, but little more. This actually caused them to have minimum travel time and distance between machines and made them more productive.
Tightly Stack Duct to Reduce Trips to the Field
Many contractors want to save fuel and travel time to jobsites, so the workers loading the duct cram as much as possible into the trailers or delivery trucks. However, stacking the duct too tight often results in damaged materials. This must either be returned for repair or causes the installation crews to fix it in the field. Either way, such work is waste and costly.
One contractor developed a set of bands to hold the duct in place so it would not knock into other pieces. Sometimes this loading approach resulted in more trips to deliver the product, but less rework easily paid for it. Shops know how much work is returned to them, but few contractors know the amount of work done in the field due to damaged product. Pack it right, not tight.
Run jobs in batches
The conventional way of fabricating duct is to do every job as a batch, causing lots of duct to wait at each process step. For example, one shop fabricating spiral duct fittings produced a set of fittings through each step as a batch. While the worker was using the machine on one fitting, the rest sat waiting on the floor. Waiting is waste. There was much wasted energy picking up and setting down each fitting at each machine. A better method is to flow each piece or fitting through the shop and not in batches.
Keep the shop working
Shop fabrication is never constant. There are always peaks and valleys. Typically what happens during a low time is that shop supervision will start fabrication jobs that have need dates well over a week away. While this may keep the workers in the shop, it has many negative effects.
Change orders may cause the completed duct to be wrong, resulting in wasted material and labor. Even if the customer ends up paying for the change, it is still wasted effort. Once a job is fabricated, the shop never has room to store it, so often the duct is sent to the jobsite early. This disrupts the field crew’s current work and requires double handling of material - more waste.
Shop supervisors think they’re doing the company a favor by fabricating work early and keeping their hands productive, when they’re really adding more waste to the operations. The myth is that the field work serves the shops’ needs, when in fact the shop should only fabricate as needed in the field.
Some of these myths have been used for many years and are passed on from supervisor to supervisor. It takes a better understanding of operations to see that what may appear to be good for the shop is really not good for it or the company. Faster is not better; high utilization in isolation is not more productive. More space is not the answer, less trips to the field may not save time and fabricating too early is not a good idea.
Avoid the myths and be smart - and productive.