The Elsmar Cove Forum - Blogs

Gage Resolution Required for SPC!

bobdoering — Thu, 12 Nov 2009 14:51:37 GMT

When considering the concept of what gage resolution is appropriate for SPC, we can benchmark some of the work from the automotive industry found in AIAG MSA (Measurement System Analysis)
3rd edition. It refers to the "10:1 rule of thumb" on page 43-44. They state that it can be considered a starting point, but that it "does not include any other element of the measurement system's variability." ndc (number of distinct categories) uses the gage study to generate statistically significant "buckets" or true gage resolution versus the indicated gage resolution or "readability" or "discrimination" (number of graduations, digits, etc. on the gage).

On page 45, they claim that the ndc should be greater than 5. And that may be true for general measurement. But it is woefully inadequate for SPC!

The most key statement is "If the measurement system lacks discrimination (sensitivity or effective resolution), it may not be an appropriate system to identify the process variation or quantify individual part characteristic values. All parts in the same category will have the same value for a measured characteristic."

On page 45 through 46, they indicate the need for good resolution in order to have SPC be effective. They claim, again, 5 categories is sufficient for SPC, which, again, is woefully inadequate. You should have 5 categories on either side of the mean - if you are using X-bar-R charts or similar - to have enough resolution to utilize Western Electric rules (or similar). In fact, on page 46 they indicate "adequate resolution would be for the apparent resolution to be one tenth of the total process six sigma standard deviation." For SPC, I prefer the following:

ndc (for SPC) = ((UCL-LCL)*1.41)/(GRR) >10

This calculation assures 10 statistically significant categories within the control limits.

Open Space meetings -- another great tool for collaboration

Panchobook — Sun, 01 Nov 2009 20:07:52 GMT

Have you ever been to a conference and came back thinking that your best interactions were at the coffee breaks and meals where you met surprisingly interesting folks at random?

Industry or interest group symposia typically involve sessions on subjects chosen by the organizers and delivered by knowledgeable presenters to a passive audience. The audience may have 5 to 15 minutes to lob questions at the end, and, of course, also has a chance to mingle informally at coffee breaks and at the conference meals.

But there are studies that say that individuals that bridge two disjointed social groups have access to more knowledge, methods, ideas (See, for example, Strategic Network Formation with Structural Holes), and can apply the knowledge of one group to solve problems in another; there is value in having a bridging role. Perhaps what is happening at these coffee brakes is that you are meeting bridging folks, or you, yourself are becoming a bridge -- and not even knowing it.

If informal meets are so valuable, why not observe them, optimize them for value and then make more of them? It seems someone has indeed done just this, and they called it "Open Space".

At WikiSym last week, I had the opportunity to see and participate for my first time in one such "Open Space" meeting/session.

When the session's organizers called it to order, it was simply to explain how it works, all of which took about 15 minutes. Our session was organized by Ward Cunningham (yep, inventor of wikis), and Rut Jesus. They explained the process: Participants organize "sessions" on their own interests. To do this, after the explanation, we took some sharpies and stickies, wrote our session title on the sticky and then stuck the note on a calendar wall. Other folks then write their initials on those notes they like to express their interest in the session. Rut noted that, like in a real Open Space, many creatures thrive in these meets. The bumblebee works furiously on a interesting subject, and acquires concentrated goods to make honey back home. The butterfly just flies carefree back and forth between groups cross-pollinating.

And though the intro was amusing, the best was to come. Initial skepticism vanished soon after the sessions started. Folks gathered in small circles of chairs and discussed interesting subjects, such as graphical wikis and structured information in wikis (many on subjects that probably had too few participants to warrant a full blown sym session anyway). The mini-sessions were intense, with hands-on demos and discussions not possible in a formal setting. Yep, many structural holes were bridged -- met some amazing folks that I'd needed a several dozen coffee breaks to run into.

Only regret not having started a session on using wikis for management systems, but I will next time around. Also, this format is great for engineering, quality or company meetups, so will propose it when I next attend one of those (or post to their respective forii) and thereby bridge some ol'holes. In any case, possibly the best learning I came away with from WikiSym was being exposed to Open Space.

-- Pancho

Inaccuracies in the Inconvenient Truth - TAT for TIT

Dr. L. Ramakrishnan — Sat, 17 Oct 2009 05:02:12 GMT

I just came across this information on the inacccuracies in the acclaimed documentary "The Inconvenient Truth" (TIT) by Al Gore. No doubt, Al Gore raised mass awareness on Climate Change issues through this documentary. Al Gore deserves our admiration for the strong commitment he has for this common cause. No doubt, Climate Change is a Global issue.

A British Judge hearing a case on the documentary came out with the following eleven inaccuracies:

1.The Inconvenient Truth (TIT) claimed that melting snows on Mount Kilimanjaro was due to global warming. British Government's expert conceded that this is not correct.

2.TIT suggested that evidence from ice cores proved that rising CO2 caused temperature increases over 650,000 years. The Court found that over that period the rises in CO2 lagged behind the temperature rises by 800-2000 years.

3. TIT used emotive images of Hurricane Katrina and suggested that Katrina had been caused by global warming.The Government's expert had to accept that it was "not possible" to attribute one-off events to global warming.

4.TIT showed the drying up of Lake Chad and claimed that this was caused by global warming. The Government's expert had to accept that this was not the case.

5.TIT claimed that a study showed that polar bears had drowned due to disappearing arctic ice. It turned out that four polar bears drowned and this was because of a particularly violent storm.

6.TIT threatened that global warming could stop the Gulf Stream throwing Europe into an ice age: this is a scientific impossibility.

7. TIT blamed global warming for species losses including coral reef bleaching. The British Government could not find any evidence to support this claim.

8.TIT suggested that the Greenland ice covering could melt causing sea levels to rise dangerously. The evidence is that Greenland will not melt for millennia.

9.TIT suggested that the Antarctic ice covering was melting, the evidence was that it is in fact increasing.

10.TIT suggested that sea levels could rise by 7m causing the displacement of millions of people. In fact the evidence is that sea levels are expected to rise by about 40cm over the next hundred years and that there is no such threat of massive migration.

11. TIT claimed that rising sea levels had caused the evacuation of certain Pacific islands to New Zealand. The British Government is unable to substantiate this and the Court observed that this appears to be a false claim.

Indeed there are a few more inaccuracies in the film, like the one on Mumbai rains....rains and clogging of drainage in Mumbai are not new.

Does this diminish the stature of Al Gore ? In my opinion, a big NO. All poets have the freedom to use "exaggeration" to bring home their points. I think Al Gore has the poetic freedom to exaggerate !!!!

Congratulations Dr. Ramakrishnan

Dr. L. Ramakrishnan — Sat, 10 Oct 2009 10:57:49 GMT

All budding and serious scientists believe that their work is of Nobel Prize quality. Now Dr. C.V. Ramakrishnan got the Nobel prize in Chemistry with two others, his dreams would have come true. Congratulations Dr. Ramakrishnan for this honour!!

I wish I had worked like you as a scientist towards this coveted goal.....but for me that was only a dream..being a mediocre scientist (of course, with a Gold Medal for the best Ph.D. thesis from the Indian Institute of Science, Bangalore, India) I would not have even taken the first step towards such a coveted prize. Anyway, I moved away from Pure Science .....a long ago.

I am proud that I share your name (first name) at least....we of course share the country of birth, state and the mother tongue (Tamil) etc. Incidentally two other Nobel prize winners of Indian origin in Sciences (apart from Hargobind Khorana), Sir C.V. Raman and Prof. S. Chandrasekhar, are from Tamil Nadu in India. We are proud of all of you.

Let this trend continue !!!!

Congratulations once again.

Congratulations to Barrack Obama too....for his Nobel Peace Prize.

Congratulations to all the other Nobel Prize winners...about whom I will have to learn more in the days to come :)

The real point of the Central Limit Theorem?

bobdoering — Wed, 23 Sep 2009 12:41:42 GMT

We have pretty much given up on the using the central limit theorem to "prove" why SPC works, so, what does it really "prove"? One thought is that the larger the sample, the more the average masks the true distribution. This "sampling error" becomes more and more like the normal distribution. So, you could conclude that sampling error - like measurement error, e.g. - tends to be a normal distribution.

Cool, huh?

Intro to MSA of Continuous Data � Part 8: Comparison of Two Gages

Miner — Sat, 19 Sep 2009 23:38:13 GMT

This is the eighth in a series of articles about MSA. The focus of this article will be on assessing the measurement reproducibility between two measurement systems that must measure the same characteristic.

Does the following scenario seem familiar? An operator performs an online test on a product. The test shows a failure to meet specifications. This is an expensive product, so the line supervisor takes the part to an online tester located on an adjacent line and retests it. This time it passes. The supervisor instructs the operator to go ahead and use the part. Both of them lose confidence in the first measurement device. But which one provided the correct result?

There are several approaches that may be used to assess the reproducibility of two measurement devices.

One approach that is commonly used when the measurement devices are fully automated is to perform a standard R&R study and replacing the Operators with the Measurement Devices. Reproducibility is now tester to tester reproducibility. The operator*part interaction becomes the tester*part interaction. While this approach does quantify the reproducibility of the two devices, it has the drawback of providing little additional information if a significant difference between the two is noted. It is also limited to fully automated gages. You do have the option of adding gage as a third factor (Parts, Operators, Gages) and analyzing the resulting designed experiment using Analysis of Variance (ANOVA).

A second approach is known as the Iso-plot. This is a very simple graphical approach. An x-y plot is constructed with equal scales, and a 45� line is drawn through the origin. Parts are selected throughout the expected measurement range. Each part is measured using both gages. Each part is then plotted on the graph using the value measured by one gage on the x-axis and the value measured by the other gage on the y-axis. Ideally, the coordinates of all parts will lie on the 45� line. If the points fall consistently above or below the line, one gage is biased in respect to the other. The Iso-plot provides an excellent visual assessment of the reproducibility of the two gages, but does not provide quantifiable results. A linear regression analysis of the data used to create the Iso-plot will provide quantifiable results. Ideally, the regression constant should equal zero and the slope should equal one. The regression output will provide the relationship between the two gages as well as confidence and prediction limits.

A third approach is the Bland Altman plot. Parts are selected throughout the expected measurement range. Each part is measured using both gages. Calculate the differences between the gages (Gage1 � Gage2), the mean of each pair of measurements and the mean of the differences. Plot the differences on an x-y plot with the differences on the y-axis and the mean of the paired measurements on the x-axis. Draw a horizontal line for the mean of the differences. Draw two more horizontal lines at + / - 1.96 standard deviations of the differences. Approximately 95% of the differences should fall within the limits. The mean line indicates the bias between the two gages. A trend indicates that the bias changes with the size (a linearity difference between the gages). An increase (or decrease) in the width of the pattern with size indicates that the variation of at least one of the gages is dependent on size. If the variation within the limits is of no practical importance, the two gages may be used interchangeably.

Do not overlook the differences between gages when evaluating your measurement systems. Your operators will be quick to discover gages that inconsistently accept and reject product between the gages. They will then lose confidence in them and the test itself.

Return to India

Howard Atkins — Tue, 15 Sep 2009 16:28:04 GMT

I have just returned from an ISO/TS 16949 audit in India.
This is not the first time I have been to India and as a vegetarian it is probably the best place for me to visit as I know that there is no problem with food. Usually my hosts are very surprised to find me a vegetarian and are pleased and curious as to my vegetarianism.:cool:
As some one who grew up in England, India food is very well known and can be regarded as part of the English Cuisine; so many English were in India during the Raj that they brought their love for the food back with them.
A familiar scene in English TV programs are the drunken roll out from the pub accompanied by the "lets go for a curry" and the following discussions with the waiter on a "Red Hot Vindaloo" :agree1:
To connect this to my current home see England Fans sing Vindaloo in Tel Aviv:bonk:

I had an opportunity to have some tourist time and went to Agra to the Taj_Mahal and Agra_Fort. I will post some pictures in the photo albums.

When one says to people that you are going to India one tends to get the normal ignorant comments and I explain that I have seen good factories in India and terrible plants in Detroit and the country does not determine the facts.

I have the same issues in Israel where there are excuses given all the time for the look of the plant or the depth of analysis. They claim that they cannot waste time on data collection but are prepared to rework and reject.

As one CEO said to me "if they could see $ being scrapped then they would think again"
In Israel there are plants that are spotless and others that claim that their technology prevents good housekeeping but do not see the paper cups, cigarette butts and other rubbish on the floor.

I returned to Israel and went to a plant that I had been before the trip; they asked me about the trip with a tone of contempt. I told them that it was better that I did not tell them. In this Israeli plant I would not let a rat eat from the floor, if I could get to the floor through the lakes on the floor around the machines:nope: but in the factory in India I would eat from the floor.
This company working in the rubber industry was clean the previous visit but now had improved vastly. It had cleaned all areas and had introduced a form of voluntary service whereby the top management weekly shows its solidarity by themselves spending 30 minutes cleaning machinery.
The plant in Israel cannot enforce the law about smoking despite complaints by workers, the plant in India, despite the fact that the MD smokes has no smoking inside the fence.
The audit went very well. They have a very active and effective Continuous Improvement program which includes also worker motivation actions such as visits by production workers to customers to see how their products are received.:applause::applause:
I know that this is one example from India and Israel and I know that plants in the opposite direction can be found in both countries but the explanation is as we learned in Quality 101.

It all depends on the Top Management:magic:

Remember
You have one chance to make a first impression

Writing I made days after 9/11

Tom W — Fri, 11 Sep 2009 17:47:38 GMT

I wrote this a couple days after 9/11. It might not make sense but it was a spur of the moment kind of thing. It's not poetry or even flow well in spots.

It is written as If we (USA) are speaking to you (those that did this and their stereo-type). I was trying to make sense of it all without just spouting off about killing all that opposed us and our way of life.

The mood shifts in the writing from anger to comapsion to confusion. If you don't understand it I apologize, but if you want to ask questions about it feel free. Please do not take offense to it either as it was emotionally driven on the feelings at the time.

Its called...

AT LEAST....

What the hell just happened?
This feeling is so strong,
As I sit here watching them fall,
I know something is very wrong,

The scenes unbearable,
The anger builds,
Someone�s got to pay,
Someone else has to fall,

Who do we blame?
Couldn�t have been us,
Pointing our fingers and saying,
It had to be you, you or you,

All those people,
All that life,
Taken at once,
Taken by flight,

At least it wasn�t me,
At least it wasn�t you,
At least it wasn�t more,
At least it was only four,

Together we cry,
Together we stand,
Together we are,
Hand in hand,

So here we go,
Here we go again,
Halfway around the world,
To let freedom ring,

Freedom is coming,
Coming for you,
Justice will be served,
Served on you, you or you,

We send in our sons,
We send in our daughters,
We send them after you,
What will you do?

You will send your sons,
You will send your daughters,
You will send them after us,
What will we do?

Many have died,
Many more will,
This fight is hard,
Hard as hell,

The anger subsides,
The anger fades,
We now ask why,
With our hands to the sky,

Bombs fall down,
Smashing your dreams,
You now ask why,
With your hands to the sky,

What did we do?
What was so wrong?
Why are you here?
Singing this freedom song,

Standing up for what you believe,
That is all we do,
We are like you,
We want that too,

Revenge is always bad,
So they say,
Dig two graves,
One for them and one for you,

Send in the Army,
Send in the Marines,
Send in the Air Force,
Send them all in,

Send them to fight,
Send them to win,
Give them your support,
Pray for their lives,

We all pay a price,
But how big is yours?
What are we doing?
Other than spewing words,

Marines are dying,
Soldiers too,
What have you done?
What are you willing to do?

History is made,
Time rolls on,
Those that have perished,
Their memory soon gone,

At least it wasn�t me,
At least it wasn�t you,
At least it wasn�t more,
At least it was only four,

What can be done?
What can we do?
Remembering the anger,
Looking at you,

We are in it to win,
We are in it for long,
We will fight on and on,
As you sing your song,

God is great,
God is glory,
We feel that way too,
But we won�t stop you,

We won�t stop you,
From praising your God,
We want you to know,
No one is wrong,

We stand for freedom,
You stand for fear,
We are correct,
And you are�?

Statistical process control for precision machining - Sample Data

bobdoering — Wed, 09 Sep 2009 16:07:15 GMT

Some folks were looking for some sample data of a precision machining process in control. Attached is such data, from an actual CNC turning of a forged blank. Feel free to contact me with any questions!

Attached Thumbnails

Dvorak keyboard - one cure for RSI and bad typing habits

Panchobook — Sun, 06 Sep 2009 23:23:44 GMT

A few years ago I was developing a bad case of pain in my wrists from a lifetime habit of typing with a terrible hand position. I switched to the Dvorak keyboard. Clicking on an old bookmark brought this experience back to me today, and I thought I'd share it here.

The pic shows the Dvorak keyboard layout. It was designed in 1936 as a "more efficient" alternative to Qwerty. By bundling vowels under the left fingers, it promotes alternation between the hands, and purportedly allows faster typing. It never did catch on extensively, perhaps because its advantages were never enough to overcome the inertia and network effects of Qwerty.

But for the last 25 years, with PCs, it is easy to map any keyboard layout to a standard keyboard. All OSs nowadays allow simple software switching of keyboard layouts.

In mid-2002, my wrists were hurting every evening after spending the day on the computer. I didn't exactly hunt-and-peck, but had to look at the keys, and my typing speed was sometimes frustratingly slow (i.e., when text-chatting). Some blog gushed about Dvorak and I decided to give it a try. During a long weekend (possibly Labor day weekend) I did these lessons twice.

The first week back at work was a bit difficult, but within a month my typing speed was better than it had ever been with Qwerty. Wrist pain's gone since then. Thanks Dvorak.

Picture of the week

Claes Gefvenberg — Thu, 03 Sep 2009 16:00:21 GMT

Another shot from the veteran car & aeroplane day in Eskilstuna: A Porche Spyder replica.

Model speeches of lead auditors in Opening Meeting and Closing Meetings

brahmaiah — Sat, 29 Aug 2009 06:15:43 GMT

Dear friends,
Please post the best Opening and closing speeches of a lead auditor you have heard or given during a certification audit.
It will of special interest to know how a lead auditor gives a closing meeting speech when he is not recommending an organization for the intended certification.
I wish to use your replies with due credits in my training sessions.
Thanks in advance,
V.J.Brahmaiah

Picture of the week

Claes Gefvenberg — Thu, 27 Aug 2009 21:31:48 GMT

We just had the yearly veteran car & Aircraft day at the local airfield, and of course I gave the camera a workout...

Back to Process Mapping

Dvora — Tue, 25 Aug 2009 12:52:04 GMT

What fun! After a 10 month hiatus I've finally found a contract job doing process mapping for a large company. With over 4000 employees, they have NO processes documented officially for handling HR-employee issues such as FMLA, WC, etc.

It's a daunting task, but I'm looking forward to getting into some serious stuff and learning new things.

And if anyone wants to discuss, I have a question:

To me process mapping seems simple. Observe the process, ask questions, and write it out step-by-step, then ask why for all the steps to see where you can improve. Then compare to other processes that are being considered as a possible replacement.

Have I missed something there?

Hallelujah! Back to work!

Thoughts about Propaganda - Mayberry circa 1960 vs. 2009

Marc — Mon, 24 Aug 2009 00:56:00 GMT

Thoughts about Propaganda - Mayberry circa 1960 vs. 2009

Here is a cartoon from 1948. Make Mine Freedom.

For some thoughts on this film and propaganda in general, and as a source of thousands of free videos, you might like the Internet Archive page for this film. It has some of the history about this specific film and a number of comments.

Your comments here in this blog are invited and welcomed!