The Pareto principle at work

September 12, 2006
By: Jim Berge

You may not have heard of Vilfredo Pareto, but you likely have heard of the 80/20 rule attributed to him. In this article, robotic welding expert Jim Berge discusses how the rule, which he believes to be more accurate as 90/10, applies to implementing robotic welding and automation successfully and achieving maximum efficiency.

The Pareto principle, named for Italian economist Vilfredo Pareto, may be better known as the 80/20 rule. Pareto observed that in most activities, a small fraction (20 percent) of the total activity accounts for a large fraction (80 percent) of the results. I have come to learn that Pareto's law applies to just about every aspect of life you can imagine. Based on personal experience, I also have discovered that 90/10 probably is more accurate than 80/20.

Why am I talking about such things in an article about robotics? Because I believe that the 90/10 rule also applies to manufacturing and automation. Let me know if you agree with the following assumptions (and please give me a little leeway here regarding the exact percentages):

  • 10% of the work force are good leaders; 90% are followers.
  • 90% of job knowledge comes from on-the-job experience and 10% from book learning. (Apologies to all you degreed engineers out there ... remember, I'm one too.)
  • 10% of your part numbers make up 90% of your product volume.
  • 90% of your costs from poor quality come from 10% of the causes.
  • 10% of your vendors are a pain in the neck, while 90% basically satisfy your needs.
  • You don't like 10% of the menu items at the deli where you and your co-workers eat lunch.

You get the point. I believe we can learn valuable lessons by applying the 90/10 rule to the challenges we face in automated welding and manufacturing.


I once worked for a large manufacturing company that planned to install many expensive robotic welding cells and needed to train programmers and operators to run them. The company was not familiar with robotic automation, so I advised them to create a new job classification called "robot technician" and to give those technicians responsibility and authority over the robotic equipment.

When management wanted me to suggest who among their chosen candidates should become robot technicians, I advised them to be patient—during the upcoming training, the cream would float to the top.

I honestly can say that everyone who took part in the training became good at operating robots, but two of the trainees (out of about 15 people) really grabbed the ball and ran with it. They became the robot technicians, and over the next few years, I saw them become robotic welding experts. (To save you math fans from digging for your calculators, 13.3 percent of the trainees became robot technicians.)

The lesson? A motivational writer once wrote that all the advice we hear about working on our weaknesses is hogwash. He said work on your strengths and develop your God-given gifts, and find others to help you with your weak areas. Ten percent of your work force will have the strengths and thought patterns that will help them excel as robot technicians and in other positions of authority. Identify these individuals and invest heavily in them, so that they won't want to leave and will want to learn even more.


Ninety percent of the companies I deal with either need to improve their part quality or change or improve their upstream or downstream processes before installing robots. Requiring improvements is not a bad thing and does not necessarily indicate poor quality or poor business practices. The need for highly accurate and repeatable parts simply is not as great when parts are welded together manually. Manufacturers can get by with inconsistent weld joints if the weld is located in an area that does not affect final part quality.

It can be difficult to convince some companies that they need to improve part quality before automating. Some learn the hard way after the first robot has been installed. In fact, this lesson was the reason the robotic industry experienced a backlash after the first machines were embraced enthusiastically in the U.S.

Many companies were sold the bill of goods that robots were the solution to all production and quality problems, but they soon learned that there's more to eliminating these problems than simply introducing a robot. Only 10 percent of parts actually were consistent enough to weld with automation, while 90 percent had to have further quality controls built in, even if the measures were as simple as cleaning or shotblasting parts before welding. It is no coincidence that the rise of industrial robots in the late '70s and early '80s was parallel to the increase in statistical process control and similar quality control programs.

The moral of the story: Focus first on the 10 percent of poor-quality parts that result in the highest costs to the company and fix the problems that contribute to the poor quality. By doing so, you will be making a huge stride forward in quality and cost reduction, particularly if this 10 percent represents your highest-volume parts. After you make all possible quality improvements, then you can install robotics and get the biggest bang for the buck.

Part Volume and Throughput

For years robot manufacturers have been trying to make robotic welding more practical for small-batch production, and they have largely succeeded. Small lot sizes can be easily accommodated with innovations like flexible fixturing, more powerful software, and sensor technologies to identify parts automatically. But there still is no substitute for sheer numbers to justify robots. That's why the automotive industry, which produces high part volumes with little change, is by far the largest user of industrial robots.

Most likely, 10 percent of your part numbers comprise 90 percent of your factory throughput, so it makes sense to focus on these parts. The typical large-volume manufacturer should start by installing robots to weld the highest-volume parts. This allows the manufacturer to get through the robot learning curve with a simpler, high-volume workcell. The lessons learned in this process (and there will be many) then will enable the manufacturer to devise more complex and flexible robot cells to handle the smaller volumes. These small-batch cells will not have the dramatic payback that the simple, higher-volume cell has, but they will be excellent investments that will quickly pay for themselves.

When choosing your highest-volume parts, remember that they do not have to be identical. One way to identify a large volume of parts is by grouping parts with similar designs into families and using flexible fixtures with very short changeover times. Rather than identifying the part number that represents 90 percent of your production volume, you are identifying families of part numbers.

The Robot Learning Curve

I have found that the typical company achieves a robotic welding cell efficiency level of 80 percent to 90 percent with little difficulty. Many companies stop trying to improve efficiency after achieving the 90 percent level of throughput, productivity, or quality. They may believe that this 90 percent is the maximum that can be achieved with robotics. The good news is that even at 90 percent efficiency, these companies probably are far outperforming their previous manual welding operation, and automation has been a good investment.

That last 10 percent efficiency can be costly to achieve, but it may make the difference between a really great investment and just a new technology that impresses customers. I want to encourage all robot users to strive for that last 10 percent of productivity or quality, because that 10 percent will keep you competitive and strong in our ever-more-global manufacturing world. Given the slim margins some manufacturers live with, it could mean the difference between being profitable and losing money.

The last 10 percent can express itself in a number of ways depending on your circumstances and your original reasons for buying robotic automation. Besides improving quality, you also may make that part more efficiently; reduce scrap rates, rework costs, field retrofits or warranty work; and possibly attain higher throughput. You might even win some new contracts.

Go ahead. Put a robot into production and achieve 90 percent efficiency through your learning curve. But be aware that once you have reached the point of feeling satisfied with your new robot installation, there may be an extra 10 percent lurking that can tip the quality or profitability scales in your favor. Remember Vilfredo Pareto. Find someone who can help you unlock that last door to productivity and quality.

Practicing the Principle

As I go about my daily activities, I constantly ask myself questions about how the Pareto principle applies. I advise you to do the same. While you're walking through your plant, ask yourself:

  • Which 10% of my work force could become robot champions?
  • Where does 90% of my quality problems originate?
  • Which 10% of my products should I focus on to make the biggest changes in the shortest amount of time? (If you haven't yet, please read The Goalby Eli Goldratt.)
  • Do I have an additional 10% of potential locked up in my existing robotic welding installations?

If you would like to share some of your 90/10 manufacturing experiences, I would love to hear them.

Jim Berge

Jim Berge

Contributing Writer
Berge Robotics
Sherveport, LA
Phone: 970-222-1753

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