six sigma and beyond - real-life six sigma - ejemplos desarrollos sixsigma

8/7/2019 Six Sigma and Beyond - Real-Life Six Sigma - Ejemplos desarrollos SixSigma

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Six Sigma and BeyondThomas Pyzdek

Real-Life Six Sigma

These synopses of actual Six Sigma projects provide usefulexamples.

For many people, it's easier to learn by reviewing examples than byreading generalized descriptions. So in this column, we'll look at several

quick overviews of Six Sigma projects to provide you with an idea of whatSix Sigma deployment looks like at the project level. Of course, these

synopses skip over significant factors, such as the leadership and

infrastructure necessary to make the projects succeed. It's not that thesefactors are unimportant; to the contrary, they're critical. For additional

information on the critical success factors, you may wish to review my

earlier columns atwww.pyzdek.com/pdf.htmand www.qualitydigest.com,

or in my bookThe Six Sigma Handbook(McGraw-Hill, 2001).

Accounts receivableThe Six Sigma team was tasked with improvingthe accounts receivable department's collection process. The project

sponsor was the CFO, and the top-level dashboard item that generated the

project was improved cash flow. The team decided to use the average ageof uncollected accounts on the last business day of the month as their

metric. Using X-bar charts because the histogram showed a very non-normal pattern, the team determined that the process was in statisticalcontrol with a mean of 57 days. They made a flowchart of the as-is AR

collection process and used it to guide an observational study.

The team noted and corrected several discrepancies, and several

obviously stupid things were changed. For example, a team member frombilling asked why the term "Net 30 Days" was used. An experiment was

conducted where the term was changed to "Due on Receipt" for a random

sample of invoices. The results showed that the average time to collect for

the experimental group was 45 days, vs. 57 for the control group. The

difference was highly significant, both financially and statistically.

Next, the team contacted randomly chosen customers who had paid late

and asked why they had been late. Fully 70 percent of the reasons for latepayment were factors under the company's control (e.g., invoice errors or

the bill being sent to wrong address). The team constructed a Pareto

diagram and set about correcting the biggest problem areas. Within six

months, the average age of uncollected invoices dropped to 37 days. The
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resulting savings were substantial.

Printed wiring board componentsThe Six Sigma team received itsproject from the material review board. The MRB identified the project as

a significant and chronic contributor to the problem of failures at finalproduct test. The assembly was a complicated piece of hardware and finaltest failures caused shipping delays, resulting in penalties and loss of

customer goodwill. The team's project focused in the PWB assembly area.

There were three major subprojects: errors at manual insertion, errors at

automated insertion, and errors at semi-automated insertion. A fewexamples of the issues addressed include kitting errors, the layout of the

manual insertion workstation, the positioning of axial lead parts on the

automatic insertion machine's parts tape, and the speed at which semi-automated insertion was performed. Problems were prioritized and

addressed, leading to dramatic reduction of test failures.

Cycle timeThe team was chartered by a program manager to help thecompany introduce new programs more quickly. The company would

often introduce a new design into manufacturing only to find that itcouldn't be produced, which resulted in quality and schedule problems.

The team's projectone of severalinvolved establishing the capabilityof complex numerically controlled machining equipment. This was

important because the company manufactured a tremendous variety ofcomplex parts in very low volume. Standard SPC was difficult because

production runs were both short in duration and small in quantity. The Six

Sigma team wanted to develop the ability to determine in advance if a

particular engineering design could be produced at all and, if so, whichCNC machine should produce it. To solve their problem team members

designed a special test part that put each CNC machine through a complete

series of tasks. The parts were then inspected and the results used todetermine machine capability for each type of machine movement (e.g.,

drilling small holes, milling a surface or machining a groove). This data

was used to evaluate proposed engineering designs for manufacturability,for make-by decisions and to select CNC machines to produce specific

parts.

Injection molded partsThe Six Sigma team was chartered to evaluate

a problem with field failures of molded plastic parts. Members began byreplicating the problem with production parts. The problems were resolvedwithin a few weeks when the team identified a new process as the cause of

the core problem. The process mixed two different plastic components at

the injection-molding machine, as opposed to the single hopper and pre-

mixed material of the previous process. If not properly mixed, the carbonblack component would stratify and the product would fracture at the


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stratification when exposed to low temperatures.

Wire bondThe Six Sigma team received its project from a seniorexecutive who had received direct communication from an important

customer who was upset about wire-bond failures of a particular criticalpart (a thick-film hybrid microcircuit.) The project had two major areas offocus: the wire bonding process and the testing process. Problems

addressed included the metallurgy of the gold wire; the preparation and

set-up of the process; the dressing of the tip on the machine tool; pressure,

time and other settings; the hook used to pull the wire; the angle of thepull; the rate at which force was applied.

Purchase order processA Six Sigma team was chartered tostreamline the process of obtaining a purchase order. The process took six

weeks, creating delays and customer dissatisfaction. The Six Sigma team

created a process map and used historical data to show the time taken byeach step. By hand-carrying 10 PO requests through the process, the team

was able to determine that, more than 99 percent of the time, a PO request

spent in the system was nonvalue-added timemostly waiting time. Theteam subdivided the project according to the type of PO being requested.Members were able to eliminate PO requests completely for a common

type of PO and dramatically reduce processing time for the others.

Etched circuit boardsThe Six Sigma team was directed by a seniorexecutive to solve the problem of photoresist breakdown. This problem

occurred at the very end of a long sequence of process steps, which

produce a bare printed wiring board. The problem was sporadic, and whenit occurred, it resulted in delays throughout the production process. This

wreaked havoc with schedules and resulted in extensive overtime work,

shipping delays, penalties and angry customers. Through data mining, theteam was able to focus the project on work which took place in the

"yellow room," where the photoresist was applied. The project eventually

focused on the settings of the lamination and the expose processes. Theroot causes of the problems were identified, and the problem was

completely eliminated.

About the author

Thomas Pyzdek is a consultant in Six Sigma. He has written more than 50books, software and training products, includingThe Six Sigma

Handbook (McGraw-Hill). Learn more about Six Sigma at

www.pyzdek.com. E-mail Pyzdek atTom Pyzdek.
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The team constructed a Pareto diagram and set about correcting the biggest problem

areas.

final test failures caused shipping delays, resulting in penalties and loss of customer

goodwill.

errors at manual insertion, errors at automated insertion, and errors at semi-automated

insertion

the layout of the manual insertion workstation, the positioning of axial lead parts on the

automatic insertion machine's parts tape, and the speed at which semi-automated insertion

was performed.

The Six Sigma team created a process map and used historical data to show the time

taken by each step

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