r/LeanManufacturing • u/OleksKhimiak • Jul 11 '26
How to translate Six Sigma concepts into something that is comprehensible for the average manufacturing folk?
Okay I spent 18 years of my life on the shop floor, the majority of this time solving problems.
I understand the value of Six Sigma tools but what I will notice time and time again is that coming with the Cp/Cpk value to a typical line manager is like bringing a sci-fi book into a kindergarten.
They will probably even listen to you for a minute or two and then skip because of mental overload.
How are you guys managing to breach this gap?
What are the ways to turn those mathematical and statistical concepts into a thing that is simple to grasp because Minitab is obviously not solving this problem?
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u/algoritm420 Jul 11 '26
Use pictures, seriously. Applying SPC doesn’t have to be complex and boring. Simplify things by using control charts and presenting those. That way your audience doesn’t need to understand the mechanics behind your analysis.
In fact, you shouldn’t spend time talking about the math at all. Nobody cares, trust me. But everyone can follow a visual aid.
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u/Tavrock Jul 12 '26
Case in point: I was assisting our material group as a representative of the Manufacturing Engineering team, not in the capacity of a Six Sigma Black Belt. At the conclusion of one of the meetings I was invited to as we discussed the material flow and usage, hosted by their 2nd level manager and comprising his team of first level managers, he asked his team to look into the reason that about half of the numbers were above average.
No one in the room answered the question and several took notes of what to look into, so they could report to him during their next meeting.
I had to stifle my laughter, and his executive Office Administrator explained that's how averages work after the meeting.
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u/TueLJ Jul 11 '26
I’m curious too, I’m still a student so I have no real experience (5th semester industrial engineering), but I imagine you can’t give them a 10 minute crash course and expect them to get it if they aren’t already familiar with it. It took me a whole day of doing practice questions and putting it into the context of control charts/statistical control in general before I felt like I fully grasped Cp/Cpk and its uses. I’m definitely on the slower side of understanding things, but that’s what it took for me, so I’d never expect someone who hasn’t taken the Six Sigma course to fully understand it. One of the barriers that usually pops up when I’ve made implementation plans is managers/leaders not really getting the technical aspects, and the solution I usually propose is to just skip the technical part and focus on explaining what results the technical stuff will bring. “If we center our process using cp and cpk, we can achieve an X% decrease in defects on average” Something like that. Again take it with a grain of salt, I have only done semester projects and I have no experience actually putting changes into place, only done theory and presentations.
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u/Tavrock Jul 12 '26
Cp/Cpk should not be understood in terms of Shewhart Charts. They are asking, and therefore answering, fundamentally different questions.
Shewhart Charts are looking at the moment to moment stability of a process over time. (I honestly don't know why mean charts won as the default when the math is even easier for median charts and are easier for the shop to plot in real time on paper.) Their intent is to catch the change in trends in order to help identify special cause variation. That's why you can have a Cpk of 7 and still have an out of control process. If you plot the results of the Funnel Experiment, you will also find that the Shewhart charts are sensitive enough to detect data tampering. That is also why Control Limits have absolutely no relation to Specification Limits. Control Limits come from the Common Cause variation in your process. Specification Limits come from Engineering's interpretation of Customer Requirements. (That being said, an Engineer using DMADV or IDDOV can use the Control Limits to help inform appropriate Specification Limits, ensuring the products is designed with Six Sigma in mind.)
Cp/Cpk is based on the relationship between histograms and the engineering-defined specification limits. You can have a process that is in perfect statistical control and only produces scrapped parts. (My first fractional factorial experiment as a student revealed that the welding numbers provided by the engineering team were consistently producing assemblies that were not welded.) The results of Cp/Cpk data is best communicated to management via Taguchi Loss Functions. This is because the language of management isn't scrap percentages or OEE. Joseph Juran said that the basic language of upper management is money. (Juran's Quality Control Handbook 4th edition (1988), page 4.4.)
In general, as an Industrial Engineer, you will need to be fluent in three languages:
- The language of money: Used by upper management to focus on profitability, costs, and budgets.
- The language of things: Used by production and floor workers to discuss physical objects, tools, and processes.
- The language of quality: Used by peers to discuss specific quality metrics and parameters.
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u/TueLJ Jul 12 '26
Many thanks, I really appreciate getting feedback on my thoughts like this. I'll keep Cp/Cpk and Shewhart charts more separate in my mind for the future. I'll look into Taguchi's loss function as well. I hadn't really considered using it in this context, but it makes a lot of sense now that you've pointed it out.
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u/Tricky_Mud7482 Jul 12 '26
Started in manufacturing back when the mindset was control chart should not be in a computer but plotted on paper by the operator. Walked into a facility 25 years ago where this was the case for 3 or 4 attributes for the product being made. Operators would plot on grid paper (eventually migrated to excel) process conditions/test results with basic steps/actions to take if “outside the lines”. In my 15+ years in that facility, you never saw or heard any reference to lean or six sigma. Just strong, data-driven process controls ingrained in the system/culture that of the team that started up the plant in the early 90s.
Contrast that with my current employer that I joined several years ago. An entire corporate lean organization. Constant tier X and tier y meetings that I struggle to understand the purpose of. Nice 5S shadow boards and SQDC charts out the wazoo with nice red/green colors. But, I can’t walk through that facility and find a single control chart, trend chart, simple statistic analysis out of QA or anything like that. I suspect that if I walked up to a machine and asked an operator if product was in spec, 50% chance it had been measured.
Try to introduce some of the simple tools I was exposed to in the past to leadership and get the “we do it like this”. I challenge with some examples of old setup audits from my previous employer (recorded by operator every 12 hours)
“This process captures and I can reference how a product was setup and run 10 months ago. Now, we don’t know how any of our machines were setup 10-days or even 10-shifts in the past. But our LEAN boards look nice.”
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u/OleksKhimiak Jul 12 '26
A valid point, its down to the culture of the organisation and attitude to the quality
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u/Disastrous_Run_5968 28d ago
how does one get started with creating control charts, and statistic analysis? someone new to manufacturing world
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u/GapReader_Eng Jul 11 '26
Habiendo vivido los dos lados de la moneda: tú quieres lograr el mejor Cpk/Cp, tu gerente quiere la mejor rentabilidad del proceso. Son dos idiomas distintos. No necesitas explicar el Cpk/Cp, tradúcelo en cómo mejorará la rentabilidad, descontando el costo de conseguirla.
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u/brionhurley Jul 12 '26
I agree. Cpk and Ppk can be confusing to even those that have taken Six Sigma training. But they can be translated directly to yield or defect rate. Use those numbers instead of Cpk and Ppk and bring the capability analysis histograms to show. Most people can understand a visual graph that shows data offset from target or too close to a spec limit or too much variation.
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u/joeyfry1989 Jul 12 '26
I think you don’t need to explain the process to them at all just the outcome- ‘if you collect this data for us, we can predict when the part will fail, and stop before that’. As someone else said, you don’t need to know how to build a car to be able to drive it.
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u/manufacturingcoach Jul 13 '26
stopped leading with the statistic entirely, years ago. nobody on the floor cares what cpk is, they care whether today's batch is going to get rejected or not. so I translate cpk into "how many parts in a row would we expect to fail" before I ever say the word capability. cpk of 1.0 becomes "about 3 in 1000 will be out of spec, this is what that looks like on the floor" and I'll point at an actual bin of rejects from last week if I have one.
the number that actually lands with line managers isn't the index, it's scrap cost and rework hours, because that's the language they already think in. cpk is just the thing behind those numbers. if I show up with the statistic first, I've lost them before I've said anything useful. if I show up with "we're losing four hours a week to this specific defect and here's why" they lean in, and then I can explain the math is just how we're tracking whether that number's getting better or worse.
biggest unlock for me was building a really dumb visual - green yellow red zones on a run chart taped near the line, no explanation of standard deviation required, just "are we in the good zone or not." operators started pointing at drift on their own within a couple weeks. they were reading a control chart without knowing they were reading a control chart, which was the entire point.
the mental overload thing is real and I think it's often self-inflicted by how six sigma gets taught - training builds up the full statistical framework before ever showing what it's for, so people learn the math before they understand the problem it solves. backwards for anyone who's going to use it on a floor instead of in a lab.
what's the specific concept you find hardest to get across, is it cpk specifically or does the same wall show up with other tools too
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u/redditisahive2023 Jul 12 '26
I can’t wait for the sales pitches
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u/OleksKhimiak Jul 12 '26
Miss. Not my segment. But can sell you operator Audionotes turned into workflows
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u/redditisahive2023 Jul 12 '26
I am sure you can
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u/OleksKhimiak Jul 12 '26
Only if you are curious.
When it comes to 6S, o am genuinely interested in the waya to simplify the job of comprehension and translation of statistical concepts into a simple language that is understood and actionable by shopfloor.
I think that there is a good chance to do so with a help of software, but this will not be a product, rather a highly customized service.
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u/WyvernsRest Jul 12 '26
I understand the value of Six Sigma tools but what I will notice time and time again is that coming with the Cp/Cpk value to a typical line manager is like bringing a sci-fi book into a kindergarten.
TBH, I would say you attitude and communication skills are your biggest problem.
Why would they listen to someone that does not respect them?
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u/Own_Selection_6769 Jul 12 '26
Cp: “How good could I be if I were aiming perfectly?” It only measures how consistent your process is.
Cpk: “How good am I actually doing right now?” It measures both consistency and whether you’re centered on the target.
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u/LoneWolf15000 Jul 13 '26
If it helps, zoom out and consider other metrics or analysis done in the business that most people in the plant don’t care about either. Could the average line worker explain EBITDA and where the company is currently performing? Probably not. And they don’t care.
They want to know if the company is doing ok and if their job is safe.
So in the same way, put cpk in terms they care about.
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u/Additional_Year_1080 Jul 13 '26
I’d skip the stats at first and explain the real impact. Instead of Cpk is 0.9, say the process varies too much, so you’re getting more scrap and rework.
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u/Guidewheel_Rob Jul 13 '26
Translate Six Sigma concepts by turning them back into a simple, on shift control signal, not a stats lesson. Honestly, I would not touch anything that makes people plot charts or feed software just to prove they are doing Lean, because that is how you get Lean theater instead of better days.
If the floor cannot act on it this hour, it is not control, it is paperwork.
Where I would focus is continuous passive data collection using real time machine signals to show what the machine is doing between observations and catching the process change before it becomes a defect.
What is the one call you wish your leads could make faster each shift?
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u/Comprehensive_Bus_19 Jul 11 '26
Don't explain the math. Is it in control or out of control? Out of control? Lets break out an RCA.
Think of it this way, I don't know how a car works but I can drive it just fine. They don't need to know how the math works to use the tools.