You know what quality is, yet you don’t know what it is That’s self-contradictory. Some things are better than others. That is, they have more quality. But when you try to say what the quality is, there’s nothing to talk about. But if you can’t say what quality is, how do you know what it is, or how do you know that it even exists?
Since it was originally developed, Six Sigma has become an element of many Total Quality Management ( TQM ) initiatives. The process was pioneered by Bill Smith at Motorola in 1986 and was originally defined as a metric for measuring defects and improving quality, and a methodology to reduce defect levels below 3.4 Defects Per (one) Million Opportunities (DPMO). Six Sigma is a registered service mark and trademark of Motorola , Inc. Motorola has reported over US$17 billion in savings from Six Sigma as of 2006 . If I am talking to you about six sigma, what is the first thing coming to your mind? Consider the hot-selling, super-slim Razr phone. A creative, innovative design, sure. Yet &quot;Six Sigma's stamp is all over the Razr,&quot; says Michael S. Potosky, Motorola's corporate director of Six Sigma. Engineers, for instance, applied the process to the phone's antenna, helping keep it hidden while maintaining call clarity. GE first began Six Sigma in 1995, after Motorola and Allied Signal blazed the trail. In 1996, Six Sigma cost GE USD 200 million with a ROI of USD 150 million. The following year it cost them USD 400 million with returns of USD 600 million. And then in 1998 they hit the jackpot ; the programme cost USD 400 million with returns of more than USD 1 billion. GE went on to estimated benefits in the order of USD 10 billion during the first five years of '' Six Sigma ' implementation. About 35% of U.S. companies have a Six Sigma program in place, according to a January, 2006, Bain & Co. study.
Say ss is about reducing variation. Walk to the bb, and draw the normal curves. Why &quot;Sigma&quot;? The word is a statistical term that measures how far a given process deviates from perfection. The central idea behind Six Sigma is that if you can measure how many &quot;defects&quot; you have in a process, you can systematically figure out how to eliminate them and get as close to &quot;zero defects&quot; as possible. To achieve Six Sigma Quality, a process must produce no more than 2 defects per billion opportunities
6 sigma: 2 in a billion will be defective.
12 Pareto Diagram - Focuses our efforts on the problems that have the greatest potential for improvement by showing relative frequency and/or size in a descending bar graph. Based on the proven Pareto principle: 20% of the sources cause 80% of any problems.
17 Can be used to systematically track backwards to find a possible cause of a quality problem (or effect)
As process standard deviation goes up, or the mean of the process moves away from the center of the tolerance, the Process Capability sigma number goes down
Quality and Capability DSC 335 Zhibin Yang, Assistant Professor Decision Sciences
DSC 335 Roadmap Operations Strategy Process Management Process strategy/analysis Capacity analysis/planning Quality management Lean systems Supply Chain Mgmt. Supply chain dynamics Inventory management Case: Kristen’s Cookie Case: Blanchard Littlefield Game 1 Littlefield Game 2 Case: A Pain in Chain Beer game Decision Making Tools
“… If no one knows what it is, then for all practical purposes it doesn’t exist at all. But for all practical purposes it really does exist . What else are the grades based on? Why else would people pay for some things and throw others in the trash pile? Obviously some things are better than others – but what’s the ‘betterness’…?”
--- From Zen and the Art of Motorcycle Maintenance , by Robert Pirsig
Seeks to reduce variation in the processes that lead to product defects
- standard deviation of probability distribution
For normal distribution:
(Mean 3 ) contains about _____ of the data values
(Mean 6 ) contains about ______ of the data values
A sample falling out of interval is considered a _____
With 6 process, __ defects per billion products (literally zero defects)
Magnitude of Difference for Sigma Levels Sigma Spelling Time 1-Sigma 170 misspelled words per page 31.75 years per century 2-Sigma 25 misspelled words per page 0.45 years per century 3-Sigma 1.5 misspelled words per page 3.5 months per century 4-Sigma 1 misspelled word per 30 pages 2.5 days per century 5-Sigma 1 misspelled word in a set of encyclopedias 30 minutes per century 6-Sigma 1 misspelled words in a library 6 seconds per century
Six Sigma Roles in Organizational Implementation
Setting up a vision
Empowering other roles with freedom and resources
Champions (Quality Leaders, in GE)
Integrating implementation across the organization
Identify the key aspects of the current process that influence Critical To Quality (CTQs) characteristics
Collect relevant data of the current process
Measure: Run Chart – Precision Drift over Time in a Drilling Process Tracks process behavior “ Eyeball” trends 0.44 0.46 0.48 0.5 0.52 0.54 0.56 0.58 1 2 3 4 5 6 7 8 9 10 11 12 Time (Hours) Diameter of a drill process
Measure: Pareto Charts Focus on most important problems using the 80/20 rule Assy. Instruc. Frequency Design Purch. Training Others 80%
Step 3. Analyze – Diagnose Root Cause Effect Possible categories of causes Symptoms /effects Equipment Environment Materials Methods People Fishbone Diagram
A metal fabricator produces connecting rods with an outer diameter that has a 1 plus/minus 0.01 inch specification. A machine operator takes several sample measurements over time and determines the sample mean outer diameter to be 1.002 inches with a standard deviation of 0.003 inch.
Calculate the process capability index for this example
What does the index tell you about the process
This process is not capable at present due to the process mean off the center. The process center should be adjusted.