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Shorten changeovers and reap the benefits in lean manufacturing

How streamlined changeovers open opportunities for metal fabricators and manufacturers

Lean manufacturing and managing changeover

Want to streamline changeovers in your lean manufacturing journey? Scrutinize the steps, eliminate what you can, then restructure what’s left to keep jobs moving in your metal fabrication operation. Getty Images

Changeover is a fact of life in a metal fabrication job shop. You perform changeovers on the press brake, the welding operation, and even in information-based operations like quoting. Yes, changeovers happen, and making them more effective can have many positive results on an operation. Let’s explore.

Analyze Your Changeovers

The ideal is to eliminate the changeover altogether. Is it feasible? In some cases, the answer is a resounding yes. If you can make the fixture universal so that there are no adjustments, tooling changes, or fixture swapping, then your changeover time can be practically zero.

Let’s suppose this isn’t practical. What do you do? First, you need to understand the current state of your changeover process. Be sure to include multiple perspectives and input from operators, engineers, and supervisors. Analysis will likely include the following:

  • Observe the current state. Simply go see! Quietly observe the complete changeover cycle to make sure you understand what is happening.

  • Define the process and break it into internal and external elements. The changeover elements are the puzzle pieces that allow you to design the improvements. Internal elements are pieces of work you can do only while the process is stopped. For example, you cannot take the tooling out of the machine while it’s producing parts. The external elements are pieces of work that can be done while the machine is running. For example, you can gather and prepare the tooling for the next product while the machine is running.

  • Conduct a changeover time study. Define the steps in the changeover process and do a time study. One effective technique is to take a video of one or more changeovers so that you can validate what you have documented during the time study.

  • The changeover time should include the time from the completion of the last run to the start of the next run—that is, the last good part on the previous job to the first good part on the next job. Analyzing this, you’ll likely uncover different types of muda (waste). This might include traveling to the toolroom for a tool, looking for a particular wrench, getting a shop traveler or print from the office, and lots more. All such muda is fair game to be included in the time study. This can reveal your so-called “hidden factory,” those hidden pockets of muda that present real opportunities for improvement.

  • Develop a spaghetti diagram. It should illustrate the changeover person’s movements. Some movements will have a clear purpose, and some will leave you scratching your head.

  • Develop a cause-and-effect diagram. With the data and knowledge about the current state, gather the operator, engineer, and supervisor (and possibly others, depending on your organization’s structure and the particular skills you need) and begin a structured brainstorming process to build a cause-and-effect diagram. Start with the classic “man, machine, material, and methods” categories. You can use the changeover video to help you analyze particular pieces of work.

With a thorough understanding of the current state, you can begin to design the new and improved changeover process. Be creative, bold, and aggressive. But above all else, be sure the changeover process is safe.

Convert Internal to External

As stated earlier, the best solution is to eliminate changeover altogether. When that is not practical, look for ways to minimize it. How? First, identify all the wasteful elements and eliminate them. Next, wherever possible, convert internal changeover elements to external elements.

Internal elements keep you from running production. This is any changeover work, be it value-adding or non-value-adding, performed while the machine sits idle. When the operator goes off to look for a missing tool or die set, retrieve the next parts, or track down a print, he has to do it to move forward with the changeover, but it does not add value to the overall process.

In a well-designed changeover, the tooling would either be stored near the machine or would have been delivered before the previous production run finished; the next job’s parts would have been delivered into the incoming materials square at the machine; and the prints would have been delivered in the job packet or available in electronic form on a tablet or laptop.

Other hidden factory elements include a lack of clarity about the production schedule; seeking deviations to “too tight” tolerances; tweaking the parts into tolerance before being able to run consistently good parts; and an operator simply taking his or her time because no one is monitoring, measuring, or paying attention. Each has its own root causes that must be addressed. But until they are addressed, they will degrade your changeover performance and overall operating results.

Let’s say you have a modern CNC press brake with quick-changeover features. Tooling is easy to replace, backgauges set automatically, and the program even compensates for certain types of material variation. Is your changeover problem solved? Maybe not.

Even if you’re using machines with all the quick-change bells and whistles, don’t overlook the non-value-adding (NVA) elements. For instance, an operator might be able to change tools on the brake quickly, but what if it takes 20 minutes for him to gather and prepare those tools while the machine sits idle? You still need to make the “tool gathering and preparing” an external element. The same goes for material and job specifications. If he’s getting on a fork truck to move parts into the building from the yard, or if he’s confused about specifications and tolerances, then you still have muda, a hidden factory, and ineffective changeovers. Even with advanced machinery, you still have to pay attention to the basics.

Impact on the Business

As you continue your lean journey, understand that your improvement efforts should deliver results. This is true with changeover reduction. As with most lean improvements, some results will be obvious, some will be directly measurable, and some will be subtle … but all are important.

For instance, shorten your changeover and you have less downtime in your overall equipment effectiveness (OEE) calculation, which in turn positively affects your overall OEE score. That’s a measurable result.

Now consider the changeover reduction on your press brake (though it could be any other machine or process that better fits your environment). If this were a capacity-constrained operation (meaning it can’t keep up with demand), then the reduction in setup time frees additional hours to make more parts without increasing costs. Even if it were not a capacity-constrained operation, though, that freed time might allow you to take on new business to produce additional products. And those products produced in the additional hours could be very profitable, because you get the production without adding additional labor and factory overhead costs.

Look closely at all aspects of the changeover work, including the NVA content. Think about the eight wastes—defects, overproduction, waiting, transportation, excess inventory, excess motion, excess processing, and underutilized talent—and challenge and eliminate the NVA.

What’s left will then be challenged for effectiveness and efficiency. Is the flow optimized? Are you using the most effective tools? Are you using available technologies that allow for rapid clamping, universal application, and quick removal? Once you consider these items and stabilize the changeover process, you then can create standard work instructions so the process can be repeated consistently by whoever performs the work.

The whole changeover reduction effort should result in a safer place for the operator to work. Having performed 5S as part of the effort, you will have “a place for everything and everything in its place.” You will have the proper tools and lifting devices to do the job. And standard work will provide clarity and make training more efficient and effective.

Beyond the Obvious

Don’t just look at the obvious machines for changeover reduction opportunity. Consider all operations where you go from one job to another, anywhere you see the potential for disruption or loss of concentration and rhythm. This even includes administrative work, paper-based jobs, and information and transactional activities.

As always, make sure you know the current state of the changeover target operations. Gather data, analyze, and measure so you know the current state. Then get creative as you design the future state that incorporates your new changeover process. The sky is the limit!

Jeff Sipes is principal of Back2Basics LLC.

About the Author
Back2Basics  LLC

Jeff Sipes

Principal

9250 Eagle Meadow Dr.

Indianapolis, IN 46234

(317) 439-7960