Rolling Stones & Root Causes

Mick Jagger of the Rolling Stones famously sang:

You can’t always get what you want

But if you try sometimes,

You just might find

You get what you need

While I doubt Mr. Jagger had anything remotely near assembly automation in mind when he wrote those lyrics, they apply surprisingly well. In my 22+ years of designing and building custom automation, I have found that manufacturers often focus on solving the problem at hand, rather than looking at the root cause of the issue. It is human nature to want to solve what appears to be the immediate issue. However, it makes little sense to frantically mop up a flooded house while the faucet remains wide open. In the end, it’s a losing and costly proposition.

A good example of this type of thinking is to draw arbitrary lines between the various stages of a manufacturing process. By focusing on individual processes, engineers lose control of the orientation of a part from one stage to the next.

Be Sure to Look Upstream

I recall a manufacturer who called us in to help automate several steps in its process. The manufacturing engineer showed me an assembly operation where the operator picked a complex-shaped part out of a box. The operator then spent several seconds flipping the part over in her hands to determine the correct orientation before placing it into an assembly fixture.

When I inquired why it took so long, the engineer explained that the part was “almost, but not quite symmetrical,” and it was difficult to determine the proper orientation. The engineer had even investigated orientating the part by vibratory feeder bowl, but found that it was expensive and not 100 percent reliable. The engineer wanted a vision system that would tell the operator if the part was oriented correctly. This was imaginative and technically possible. But, it was what the engineer wanted. It wasn’t necessarily what he needed.

I asked to see the process just prior to the assembly operation. The engineer protested, stating that was not the issue. I persisted and eventually was led to an injection molding machine where the parts were being made and then ejected randomly into a bucket. This was the root cause. The molding machine obviously controls the orientation of the parts. Once we have control of orientation, we never want to let it go. In the end, we proposed to pull the parts out of the molding machine with a robot and place them into trays, so the orientation was controlled and repeatable. This eliminated the need for operators to orient the parts and reduced a 15-second cycle time on the downstream operation to less than 6 seconds, almost tripling their throughput and freeing up 2 operators for other tasks.

Maybe It's Your Product That Needs to Change

For another project we were involved in the assembly of a plastic valve. The parts of the valve were mainly cylindrical yet needed to be radially oriented. Again a feeder bowl could not orient them as the defining feature was inside the diameter. Again our only recourse was to use vision and an additional rotation station to align the part. This added cost and cycle time. We worked with the design team and suggested they add a small feature to the outside of the part. This did not affect the functional operation of the part and in fact gave them a place to add a laser marked serial number. The team had taken into account design for manufacturability (DFM) but not design for assembly (DFA). This simple change saved them tends of thousands of dollars on the assembly machine.

What We Need vs What We Want

Despite the popularity of Six Sigma, Kaizen events and lean manufacturing, I still see a distinct lack of root-cause analysis and design for assembly being performed in manufacturing. The fast-paced, demanding schedule of product development and deployment often blinds us to the real source of problems in our assembly plants. However, taking a step back to determine “what we need” rather than “what we want” can make a big difference in producing an efficient, economical and satisfactory automation solution.

Do you agree? Have you ever been blind to the root cause of a manufacturing problem? Did you ever get what you needed rather than what you wanted? Or vice versa? How would you have solved the customer’s problem? Share your thoughts!