Archive for Training

Applying Taguchi to Load Development

Posted in Manufacturing Improvement with tags , , , , , , , on August 4, 2013 by manufacturingtraining

This blog entry describes the application of the Taguchi design of experiments technique to .45 ACP load development in a Smith and Wesson Model 25 revolver.

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Taguchi testing is an ANOVA-based approach that allows evaluating the impact of several variables simultaneously while minimizing sample size.  This is a powerful technique because it allows identifying which factors are statistically significant and which are not.   We are interested in both from the perspective of their influence on an output parameter of concern.

Both categories of factors are good things to know.  If we know which factors are significant, we can control them to achieve a desired output.   If we know which factors are not significant, it means they require less control (thereby offering cost reduction opportunities).

The output parameter of concern in this experiment is accuracy.   When performing a Taguchi test, the output parameter must be quantifiable, and this experiment provides this by measuring group size.   The input factors under evaluation include propellant type, propellant charge, primer type, bullet weight, brass type, bullet seating depth, and bullet crimp.  These factors were arranged in a standard Taguchi L8 orthogonal array as shown below (along with the results):

Taguchi-1

As the above table shows, three sets of data were collected.  We tested each load configuration three times (Groups A, B, and C) and we measured the group size for each 3-shot group.

After accomplishing the above, we prepared the standard Taguchi ANOVA evaluation to assess which of the above input factors most influenced accuracy:

Taguchi-2

The above results suggest that crimp (or lack thereof) has the greatest effect on accuracy.   The results indicate that rounds with no crimp are more accurate than rounds with the bullet crimped.

We can’t simply stop here, though.  We have to assess if the results are statistically significant.   Doing so requires performing an ANOVA on the crimp versus no crimp results.  Using Excel’s data analysis feature (the f-test for two samples) on the crimp-vs-no-crimp results shows the following:

Taguchi-3

Since the calculated f-ratio (3.817) does not exceed the critical f-ratio (5.391), we cannot conclude that the findings are statistically significant at the 90% confidence level.  If we allow a lower confidence level (80%), the results are statistically significant, but we usually would like at least a 90% confidence level for such conclusions.

So what does all the above mean?   Here are our conclusions from this experiment:

  • This particular revolver shoots any of the loads tested extremely well.  Many of the groups (all fired at a range of 50 feet) were well under an inch.
  • Shooter error (i.e., inaccuracies resulting from the shooter’s unsteadiness) overpowers any of the factors evaluated in this experiment.

Although the test shows that the results are not statistically significant, this is good information to know.  What it means is that any of the test loads can be used with good accuracy (as stated above, this revolver is accurate with any of the loads tested).  It suggests (but does not confirm to a 90% confidence level) that absence of a bullet crimp will result in greater accuracy.

QMCoverThe parallels to design and process challenges are obvious.   We can use the Taguchi technique to identify which factors are critical so that we can control them to achieve desired product or process performance requirements.   As significantly, Taguchi testing also shows which factors are not critical.  Knowing this offers cost reduction opportunities because we can relax tolerances, controls, and other considerations in these areas without influencing product or process performance.

If you’d like to learn more about Taguchi testing and how it can be applied to your products or processes, please consider purchasing Quality Management for the Technology Sector, a book that includes a detailed discussion of this fascinating technology.

And if you’d like a more in depth exposure to these technologies, please contact us for a workshop tailored to your needs.

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Unleashing Engineering Creativity

Posted in Creativity with tags , , , on January 12, 2013 by manufacturingtraining

That’s the title of our newest book (available here from Amazon.com).  We also offer focused creativity training available exclusively through www.Eogogics.com/create.

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In this latest book we explore the best techniques for stimulating creative thinking, creating new products, improving existing products, and solving design challenges.  Surprisingly, even those of us who are paid to be creative often need help.  Most of us lose much of our natural creativity by the time we finish high school, but we can regain it through the techniques included in Unleashing Engineering Creativity.  This is exciting and fun material, and Unleashing Engineering Creativity presents it in an interesting and engaging manner.

Many organizations and engineers rely on brainstorming as their primary creative and inventive tool, but this simplistic approach often fails to stimulate creativity in a meaningful way.  Unleashing Engineering Creativity goes far beyond brainstorming.  This book explores powerful new creativity stimulation approaches and provides recommendations for overcoming self-imposed obstacles.   The title says it all.  If you want to unleash your engineering creativity, this book will help you and your organization attain significant creativity improvements.

Manufacturing Delivery Performance Improvement

Posted in Manufacturing Improvement with tags , , , on July 5, 2012 by manufacturingtraining

Our newest book, Manufacturing Delivery Performance Improvement, is now available from Amazon.com!

If your company has ever struggled with shipping products on schedule, this book cuts through all the theory and software mysticism the MRP and ERP companies push…it’s what you need to know if you want to eliminate your delinquencies and stay on schedule.  It’s also the book we’ll be using in the University of Kansas online Manufacturing Performance course series, and you can learn more about the KU program right here.

Leaving money on the table…

Posted in Manufacturing Improvement with tags , , , on April 10, 2012 by manufacturingtraining

On the subject of drawing tolerances, many organizations leave a lot of money on the table.   This is an important area from both cost reduction and quality perspectives.  Here’s a question for  you:  How does your organization assign tolerances?

Common approaches for tolerance selection include the following:

  • In some organizations, tolerances are based on the nominal dimension.  Dimensions up to 1 inch might get a tolerance of ± 0.001 inch, dimensions up to 5 inches might get a tolerance of ± 0.01 inch, and everything above 5 inches might get a tolerance of ± 0.05 inch.  This makes the designer’s work easy, but it is a poor practice.
  • In some organizations, tolerances are based on decimal places.  If the designer specifies a nominal dimension of, say, 1.000 inch (3 decimal places), the tolerance for might be ± .001 inch (all 3-decimal-place dimensions are assigned a ± .001 inch tolerance).  If the designer specifies a nominal dimension of 1.00 inch (2 decimal places), the tolerance is ± .01 inch.  The tolerances are restricted to fixed steps, and it’s not likely the steps correspond to fit, function, or process capabilities.
  • In some cases, designers assign tight tolerances to parts in an effort to improve quality.  This practice is misguided and builds unnecessary cost into the product.
  • In some cases, the designers assess how the parts fit together, what the parts have to do, and how the parts will be manufactured, and base the tolerances on these factors.

That last approach is the best approach.  Based on our observations of many organizations, though, it’s not what usually happens.

Cost Reduction Opportunities

The best point for reducing cost is during the design process.   A good approach is to include the manufacturing folks in the design process, assess the production approach as designs emerge, and identify processes and process capabilities for each part.  It’s the engineering organization’s responsibility to select dimensions and assign tolerances that will assure fit and function; it’s the manufacturing organization’s responsibility to raise a red flag where tight tolerances mandate expensive processes or a high likelihood of nonconformances.

If you didn’t do the above during the design process any you have tightly-toleranced parts in production, you can still reduce cost by targeting unnecessarily-tight tolerances.  Here’s a recommended approach:

  • Talk to your QA and manufacturing people.   They’ll be able to identify parts and dimensions that cause frequent rejections.   Where this situation exists, evaluate relaxing the tolerances.
  • Look for “use as is” dispositions on nonconforming parts (trust me on this…your manufacturing people will know where this is occurring).  If a “use as is” disposition is the acceptable, it’s likely the tolerance on the nonconforming dimension can be relaxed.
  • Talk to your purchasing folks.   They can reach out to the supplier community and ask the same kinds of questions.   This is a particularly important area to explore, because in most manufacturing organizations approximately 70% of the cost of goods sold flows through the purchasing organization.  You may not know without asking how many parts your suppliers are rejecting; all you’ll see are the costs buried in what you have to pay for the parts.   The best way to ask the question is the most direct:   What are we doing that’s driving your costs?  The suppliers know, and they’re usually eager to answer the question.

All of the above is associated with cost reduction, but that’s not the only place where inappropriately-toleranced parts create problems.  In many cases, dimensioning and tolerancing practices can induce system-level failures.    That’s another fascinating area, and we’ll address it in a future blog entry.

Would you like to know more about cost reduction opportunities you act on right now?  Consider our cost reduction training programs, or take a look at our most recent book, Cost Reduction and Optimization for Manufacturing and Industrial Companies!

KU Online Courses Scheduled for 2012-2013

Posted in Manufacturing Improvement with tags , , , , , on March 21, 2012 by manufacturingtraining

ManufacturingTraining and the University of Kansas have finalized the course schedule for our next series of six online Manufacturing Optimization courses:

  • Delivery Performance Improvement:  21 August 2012
  • Cost Estimation:  16 October 2012
  • Industrial Statistics:  8 January 2013
  • Quality Management:  5 March 2013
  • Root Cause Failure Analysis:  30 April 2013
  • Cost Reduction and Optimization:  25 June 2013

Each course is 3 weeks long and the University of Kansas will grant Continuing Education credit.  We’ll meet for online lectures twice each week, with interactive assignments and discussion board activities following the lectures.  We’ll be posting more information here and on the ManufacturingTraining.com website in the near future, so stay tuned for more information on this exciting new professional education opportunity!  In the meantime, if you want advance information on pre-enrolling, you can do by shooting an email to info@ManufacturingTraining.com.

State of the Art?

Posted in Manufacturing Improvement with tags , , , , on March 14, 2012 by manufacturingtraining

Back to the photo I showed a week or so ago…

An Apache Rotor Blade Bond Joint

The photo above shows a bonded section of an AH-64A Apache helicopter main rotor blade in the area where you see the blue Dykem. It’s where the blade manufacturer and the Army experienced numerous disbonds, and it’s the problem the blade manufacturer had to solve.

An AH-64A Apache at Fort Knox, Kentucky

Before delving into the failure analysis, let’s consider the Apache rotor blade’s design and its history. The Apache helicopter has what are arguably the most advanced rotor blades in the world. They can take a direct hit from a 23mm ZSU-23/4 high explosive warhead and remain intact. During the Vietnam war, a single rifle bullet striking a Huey blade would take out the helicopter and everyone on board. When the Army wrote the specifications for the Apache, they wanted a much more survivable and much less vulnerable blade.

Vietnam-Era Huey Helicopters 

The Apache helicopter prime contractor designed a composite blade with four redundant load paths running the entire rotor blade length. The blade’s advanced design uses titanium, special stainless steels, and honeycomb, but those four redundant load paths were the key to its survivability. If one section of the blade took a hit with a 23mm warhead detonation, the three remaining load paths held the blade together. That actually happened once during the first Persian Gulf war, and the Apache helicopter made it back to its base. It’s an awesome design, but it had a production weakness.

Apache Rotor Blade Sectional View Showing Four Spars 

Let’s also consider the nature of the Apache production approach. Three entities are important here: The US Army (the Apache customer), the prime contractor (who designed the helicopter and its blade), and the blade manufacturer. The blade manufacturer was a built-to-print manufacturing organization. They built the blade in accordance with the helicopter prime contractor’s technical data package.

The manufacturing process consisted of laying up the blade in a cleanroom environment using special fixturing, bagging the blade components in a sealed environment, pulling a vacuum on the bag, transporting the blade to an autoclave, and then autoclave curing.  The autoclave cure was rigidly controlled in accordance with the prime contractor’s specification.

During production startup, many of the blades had a high rejection rate after the autoclave cure. The bond joint (where the stainless steel longitudinal spars overlapped, as shown in our photo above) frequently disbonded.  Eager to get the blade into production, the blade manufacturer, the prime contractor, and the Army pushed ahead.  They believed that due to the “state of the art” nature of the Apache blade’s design, a less-than-100% yield was inherent to the process.  The disbond failures continued into production.  To cut to the chase, the blade manufacturer continued producing the blade for the next decade with an approximate 50% rejection rate.  To make matters worse, blades in service on Apache helicopters only had about an 800-hour service life (the specification called for a 2,000-hour service life).

By any measure, this was not a good situation.  The blade manufacturer had attempted to find the disbond root cause off and on for about 10 years, with essentially no success. While not happy, the Army continued to buy replacement blades, and they continued to send blades back to the prime contractor from the field for depot repairs.  The prime contractor sent the blades back to the blade manufacturer.  In retrospect, neither the prime contractor nor the blade manufacturer were financially motivated to fix the disbond problem.

After a change in ownership, the blade manufacturer realized the in-house blade disbond rework costs were significant. The new management was serious about finding and correcting the blade disbonds. Using fault-tree-analysis-based root cause analysis techniques, the company identified literally hundreds of potential failure causes. The failure analysis team found and corrected many problems in the production process, but none had induced the blade disbonds.  The failures continued. Surprisingly (or perhaps not surprisingly, considering the lively spares and repair business), the helicopter prime contractor did not seem particularly interested in correcting the problem.

After ruling out hundreds of hypothesized failure causes, one of the remaining suspect causes was the bondline width where the longitudinal spars were bonded together. That’s the distance marked on the macro photo with scribe marks on the blue Dykem (the photo I showed you earlier, and the one at the top of this blog entry).  During a meeting with the helicopter prime contractor, the blade manufacturer asked if the bondline width was critical. The prime contractor, evasive at first, finally admitted that this distance was indeed critical. The prime contractor further admitted that if the distance was allowed to go below 0.440 inch, a disbond was likely.

Armed with this information, the blade manufacturer immediately analyzed the prime contractor’s build-to-print rotor blade drawings.  To their surprise, tolerance analysis showed the blade’s design allowed the bondline width to go as low as 0.330 inch. The blade manufacturer inspected all failed blades in house, and found that every one of the failed blades was, in fact, below 0.330 inch.  It was an amazing discovery.

The blade manufacturer immediately asked the prime contractor to change the drawings such that the bondline width would never go below 0.440 inch. The prime contractor refused, most likely fearing a massive claim from the blade manufacturer for a technical data package deficiency spanning several years.  The prime contractor instead accused the blade manufacturer of a quality lapse, stating that this was what allowed the bondline width to go below the 0.440 inch dimension.

The blade manufacturer explained the results of their tolerance analysis again, and once again pointed out that the blade design permitted the disbond-inducing condition. When the prime contractor refused to concede the point (and again accused the blade manufacturer of a quality lapse), the blade manufacturer took a different tack.  As repair facility, the blade manufacturer had blades in house for depot repairs from various points during the Apache program’s life (including the 12th ever blade built, which went back to the first year of production). All of these earlier failed blades had the same problem: They conformed to the technical data package, but their bondline width was below 0.440 inch.

The blade manufacturer, faced with an ongoing 50% rejection rate, decided to hold the blade’s components to much tighter tolerances than required by the prime contractor’s technical data package. By doing so, the blade manufacturer produced conforming blades with bondline widths above 0.440 inch. After implementing this change, the blade disbond rejection rate essentially went to zero.

So what’s the message here?  There are several:

  1. Don’t accept that you have to live with yields less than 100%. You can focus on finding and fixing a failure’s root cause if you are armed with the right tools. Don’t accept the “state of the art” argument as a reason for living with ongoing yield issues.
  2. Don’t think that simply because the product meets the design (i.e., there are no nonconformances) that everything is good. In many cases, the cause of a recurring failure is design related. Finding and addressing these deficiencies is often a key systems failure analysis outcome.
  3. If you are a build-to-print contractor, be wary.  The design agency may not always be completely open to revealing design deficiencies.
  4. It’s easy to become complacent and accept a less-than-100% yield as a necessary fact of life. In some cases, the yield is not just a little below 100%; it’s dramatically less than 100% (as occurred on the Apache rotor blade production program for many years).
  5. There are significant savings associated with finding and fixing recurring nonconformances. You can do it if you want to, and if you have the right tools.

You know, the wild thing about this failure and the Mast Mounted Sight failure mentioned a week or so ago is that the two companies making these different products were literally across the street from each other.  The Mast Mounted Sight was a true show stopper…it stopped production and it probably delayed the start of Operation Desert Storm.  The Apache blade didn’t stop production…it was just a nagging, long-term, expensive rework driver for the Army and the blade manufacturer.  Which one was more expensive?  Beats me, but if I had to guess, I’d guess that the ongoing (but non-show-stopping) nature of the Apache rotor blade failures carried a heftier price tag.

Do you have recurring inprocess failures that you’d like to kill?  Give us a call at 909 204 9984…we can help you equip your people with the tools you need to address these cost and quality drivers!

A Four-Step Problem Solving Approach

Posted in Manufacturing Improvement with tags , , , , on March 8, 2012 by manufacturingtraining

In August 1990 the United States starting sending military forces to the Persian Gulf with the intent of expelling Saddam Hussein’s forces from Kuwait.  We called the buildup Desert Shield, and when we actually went to war on 16 January 1991, the name transitioned to Desert Storm.  When Desert Storm finally started, the engagement was decisive.  In short order, Kuwait was free of Iraqi forces.  It was the beginning of the end for Saddam Hussein.

Desert Shield (the buildup) lasted a good 6 months. The question in those days was:  Why the delay?  We had our forces and those of allied nations in place relatively quickly. Why did 6 months elapse before we crossed the border into Kuwait to expel Saddam?

The true reasons for the lengthy delay may never be known, but I can tell you that a key component of our smart munitions delivery capability was not ready in August 1990. You all remember the dramatic videos…munitions being dropped directly down chimneys, one-drop hits, etc.  All that was made possible through laser-guided munitions (along with the bravery and skill of our fighting forces).

One of the key laser targeting devices was the Mast Mounted Sight, shown in the photo above.  It’s the thing that looks like a big basketball on top of the helicopter.

The Mast Mounted Sight contained a laser target designator, an infrared sensor, and a television sensor.  All were slaved to the pilot’s helmet.  Wherever the pilot looked, that’s where all three beams were supposed to point.  The Mast Mounted Sight had been in production and deployed on helicopters for years.  Everyone thought everything was fine.

But it wasn’t.

When the Desert Shield buildup started, the Army tested its Mast Mounted Sight systems a bit more rigorously, and it discovered what it and the manufacturer thought was an alignment error in the laser, IR, and television lines of sight.  This could have been disastrous.  It meant that the pilot might launch a missile based on the television or the IR sensor being on target, but the laser beam would guide the munition to the wrong spot.  If a miss occurred, it would alert the bad guys, and they could return fire against the helicopter.  Mind you, this system had been in production and deployed in the field for years.

The manufacturer went into high gear to find and fix the failure cause. The Mast Mounted Sight contains an internal alignment mechanism, which is supposed to align all three instruments (the laser, IR sensor, and the TV sensor).  The manufacturer spent the next 6 months looking for a problem in the MMS alignment subassembly.  They didn’t find anything.

Hold that thought.

Ever hear the joke about the drunk looking for his car keys at night under a street light?

It goes like this: I offered to help the drunk find his keys, and after we both searched for an hour, we came up empty-handed.

“Gee,” I said, “are you sure you dropped them here?”

“Oh, no,” responded the drunk. “I lost them over there, by those bushes in the dark…”

“Then why are you looking here under the street light?” I asked incredulously.

“Because I can see here,” he answered.

Many times when we have a production shutdown, or even a low-level recurring failure, finding the root cause is elusive. Production shutdowns get a lot of attention.  Recurring nonconformances frequently do not, but they can just as expensive (sometimes more so) than a line-stopping failure.

So how do we go about finding the root cause of a failure?

Many years ago, the smartest man I ever knew once shared a simple four-step problem solving process with me.  It goes like this:

  • Define the problem
  • Define the causes
  • Define the solutions
  • Select the best solution

Where we usually go south when analyzing failures is with that first step: Defining the problem. Frequently, we start jumping to conclusions about potential causes without taking the time to fully understand the problem. The results are predictable: We spend lots of time chasing our tails, and the problem continues.

Need proof?  Try this exercise:  Tell your staff that you walked into a room, flipped the light switch, and the light did not illuminate.   Then ask them what the problem is.  In most cases, folks will immediately start listing potential failure causes: A broken filament, breaks in the wiring, a defective switch, failure to flip the switch properly, etc.  But those are all incorrect answers.

The question should be:  What is the problem?  That should be our first step.  In this case, the problem is that the light bulb does not illuminate.  All of the other suggestions listed above involved jumping to conclusions about potential causes.

Let’s turn back to the Mast Mounted Sight.  After several months of trying to find a failure cause in the MMS alignment mechanism, the failure analysis team finally decided to take a step back. They reviewed the test data again, and to their amazement, they found that the TV and the laser were aligned.  Only the IR sensor was out of alignment.  The failure analysis team had been solving the wrong problem.  Once the problem came into focus, the team looked outside the alignment mechanism, and they found an IR window heater anomaly.  The fix was a simple software patch.  It was implemented on 15 January 1991, and US troops rolled across the Kuwait border on 16 January 1991.

Would you like to know more about our fault-tree-based Root Cause Failure Analysis training program, or perhaps our book on Systems Failure Analysis?   Check out our Root Cause Failure Analysis page, and give us a call at 909 204 9984 if you would like to know more!