AQL 2.5 chart

AQL 2.5 chart

Lot size samples accept Reject
2 to 8 2 0 1
9 to 15 3 0 1
16 to 25 5 0 1
26 to 50 8 0 1
51 to 90 13 1 2
91 to 150 20 1 2
151 to 280 32 2 3
281 to 500 50 3 4
501 to 1200 80 5 6
1201 to 3200 125 7 8
3201 to 10000 200 10 11
10001 to 35000 315 14 15
35001 to 150000 500 21 22
150001 to 500000800 21 22
Above 500000 1250 21 22


Abbreviation for AQL is Acceptable Quality Limit.

Definition for AQL as per MIL – STD – 105E

When a continuous series of lots is considered, the AQL is the quality level which, for the purposes of sampling inspection, is the limit of a satisfactory process average.

What is MIL – STD – 105E

It is a Military standard for sampling procedures and tables for inspection by attributes used by Department of Defense, Washington, DC 20301, United States of America.




Abbreviation for AQL is Acceptable Quality Limit.

Definition for AQL as per MIL – STD – 105E

When a continuous series of lots is considered, the AQL is the quality level which, for the purposes of sampling inspection, is the limit of a satisfactory process average.

What is MIL – STD – 105E

It is a Military standard for sampling procedures and tables for inspection by attributes used by Department of Defense, Washington, DC 20301, United States of America.

SiX sigma

Definition Of Six Sigma, Lean Six Sigma Concepts

What Is Six Sigma?

Six Sigma stands for Six Standard Deviations (Sigma is the Greek letter used to represent standard deviation in statistics) from mean. Six Sigma methodology provides the techniques and tools to improve the capability and reduce the defects in any process.

It was started in Motorola, in its manufacturing division, where millions of parts are made using the same process repeatedly. Eventually Six Sigma evolved and applied to other non manufacturing processes. Today you can apply Six Sigma to many fields such as Services, Medical and Insurance Procedures, Call Centers.

DMAIC

Six Sigma methodology improves any existing business process by constantly reviewing and re-tuning the process. To achieve this, Six Sigma uses a methodology known as DMAIC (Define opportunities, Measure performance, Analyze opportunity, Improve performance, Control performance).

DFSS or DMADV

Six Sigma methodology can also be used to create a brand new business process from ground up using DFSS (Design For Six Sigma) principles. Six Sigma Strives for perfection. It allows for only 3.4 defects per million opportunities for each product or service transaction. Six Sigma relies heavily on statistical techniques to reduce defects and measure quality.

Six Sigma experts (Green Belts and Black Belts) evaluate a business process and determine ways to improve upon the existing process. Six Sigma experts can also design a brand new business process using DFSS (Design For Six Sigma) principles. Typically its easier to define a new process with DFSS principles than refining an existing process to reduce the defects.

Six Sigma incorporates the basic principles and techniques used in Business, Statistics, and Engineering. These three form the core elements of Six Sigma. Six Sigma improves the process performance, decreases variation and maintains consistent quality of the process output. This leads to defect reduction and improvement in profits, product quality and customer satisfaction.

Six Sigma methodology is also used in many Business Process Management initiatives these days. These Business Process Management initiatives are not necessarily related to manufacturing. Many of the BPM's that use Six Sigma in today's world include call centers, customer support, supply chain management and project management.

Lean Six Sigma

Some Six Sigma practitioners have In recent years combined Six Sigma ideas with lean manufacturing to invent new a methodology. This new methodology is called Lean Six Sigma.

HISTORY OF SIX SIGMA

The roots of Six Sigma as a measurement standard can be traced back to Carl Frederick Gauss (1777-1855) who introduced the concept of the normal curve. Six Sigma as a measurement standard in product variation can be traced back to the 1920's when Walter Shewhart showed that three sigma from the mean is the point where a process requires correction. Many measurement standards (Cpk, Zero Defects, etc.) later came on the scene but credit for coining the term "Six Sigma" goes to a Motorola engineer named Bill Smith. (Incidentally, "Six Sigma" is a federally registered trademark of Motorola).

In the early and mid-1980s with Chairman Bob Galvin at the helm, Motorola engineers decided that the traditional quality levels -- measuring defects in thousands of opportunities -- didn't provide enough granularity. Instead, they wanted to measure the defects per million opportunities. Motorola developed this new standard and created the methodology and needed cultural change associated with it. Six Sigma helped Motorola realize powerful bottom-line results in their organization - in fact, they documented more than $16 Billion in savings as a result of our Six Sigma efforts.

Since then, hundreds of companies around the world have adopted Six Sigma as a way of doing business. This is a direct result of many of America's leaders openly praising the benefits of Six Sigma. Leaders such as Larry Bossidy of Allied Signal (now Honeywell), and Jack Welch of General Electric Company. Rumor has it that Larry and Jack were playing golf one day and Jack bet Larry that he could implement Six Sigma faster and with greater results at GE than Larry did at Allied Signal. The results speak for themselves.

Six Sigma has evolved over time. It's more than just a quality system like TQM or ISO. It's a way of doing business. As Geoff Tennant describes in his book Six Sigma: SPC and TQM in Manufacturing and Services: "Six Sigma is many things, and it would perhaps be easier to list all the things that Six Sigma quality is not. Six Sigma can be seen as: a vision; a philosophy; a symbol; a metric; a goal; a methodology." We couldn't agree more.

Six Sigma Costs And Savings

In the world of Six Sigma quality, the saying holds true: it takes money to save money using the Six Sigma quality methodology. You can't expect to significantly reduce costs and increase sales using Six Sigma without investing in training, organizational infrastructure and culture evolution.

Many people say that it takes money to make money. In the world of Six Sigma quality, the saying also holds true: it takes money to save money using the Six Sigma quality methodology. You can't expect to significantly reduce costs and increase sales using Six Sigma without investing in training, organizational infrastructure and culture evolution.

Sure you can reduce costs and increase sales in a localized area of a business using the Six Sigma quality methodology -- and you can probably do it inexpensively by hiring an ex-Motorola or GE Black Belt. I like to think of that scenario as a "get rich quick" application of Six Sigma. But is it going to last when a manager is promoted to a different area or leaves the company? Probably not. If you want to produce a culture shift within your organization, a shift that causes every employee to think about how their actions impact the customer and to communicate within the business using a consistent language, it's going to require a resource commitment. It takes money to save money.

How much financial commitment does Six Sigma require and what magnitude of financial benefit can you expect to receive? We all have people that we must answer to -- and rhetoric doesn't pay the bills or keep the stockholders happy (anymore). I was tired of reading web pages or hearing people say:

"Companies of all types and sizes are in the midst of a quality revolution. GE saved $12 billion over five years and added $1 to its earnings per share. Honeywell (AlliedSignal) recorded more than $800 million in savings."

"GE produces annual benefits of over $2.5 billion across the organization from Six Sigma."

"Motorola reduced manufacturing costs by $1.4 billion from 1987-1994."

"Six Sigma reportedly saved Motorola $15 billion over the last 11 years."

The above quotations may in fact be true, but pulling the numbers out of the context of the organization's revenues does nothing to help a company figure out if Six Sigma is right for them. For example, how much can a $10 million or $100 million company expect to save?

I investigated what the companies themselves had to say about their Six Sigma costs and savings -- I didn't believe anything that was written on third party websites, was estimated by "experts," or was written in books on the topic. I reviewed literature and only captured facts found in annual reports, website pages and presentations found on company websites.

While recent corporate events like the Enron and WorldCom scandals might lead us to believe that not everything we read in a company's annual report is valid, I am going to provide the following information based on the assumption that these Six Sigma companies operate with integrity until proven otherwise.

I investigated Motorola, Allied Signal, GE and Honeywell. I choose these four companies because they are the companies that invented and refined Six Sigma -- they are the most mature in their deployments and culture changes. As the Motorola website says, they invented it in 1986. Allied Signal deployed Six Sigma in 1994, GE in 1995. Honeywell was included because Allied Signal merged with Honeywell in 1999 (they launched their own initiative in 1998). Many companies have deployed Six Sigma between the years of GE and Honeywell -- we'll leave those companies for another article.

Table 1: Companies And The Year They Implemented Six Sigma
Company Name	Year Began Six Sigma
Motorola (NYSE:MOT)	1986
Allied Signal (Merged With Honeywell in 1999)	1994
GE (NYSE:GE)	1995
Honeywell (NYSE:HON)	1998
Ford (NYSE:F)	2000

Table 2 identifies by company, the yearly revenues, the Six Sigma costs (investment) per year, where available, and the financial benefits (savings). There are many blanks, especially where the investment is concerned. I've presented as much information as the companies have publicly disclosed.

Table 2: Six Sigma Cost And Savings By Company
Year	Revenue ($B)	Invested ($B)	% Revenue Invested	Savings ($B)	% Revenue Savings
Motorola
1986-2001	356.9(e)	ND	-	16 1	4.5
Allied Signal
1998	15.1	ND	-	0.5 2	3.3
GE
1996	79.2	0.2	0.3	0.2	0.2
1997	90.8	0.4	0.4	1	1.1
1998	100.5	0.5	0.4	1.3	1.2
1999	111.6	0.6	0.5	2	1.8
1996-1999	382.1	1.6	0.4	4.4 3	1.2
Honeywell
1998	23.6	ND	-	0.5	2.2
1999	23.7	ND	-	0.6	2.5
2000	25.0	ND	-	0.7	2.6
1998-2000	72.3	ND	-	1.8 4	2.4
Ford
2000-2002	43.9	ND	-	1 6	2.3
Key: $B = $ Billions, United States (e) = Estimated, Yearly Revenue 1986-1992 Could Not Be Found ND = Not Disclosed Note: Numbers Are Rounded To The Nearest Tenth

Although the complete picture of investment and savings by year is not present, Six Sigma savings can clearly be significant to a company. The savings as a percentage of revenue vary from 1.2% to 4.5%. And what we can see from the GE deployment is that a company shouldn't expect more than a breakeven the first year of implementation. Six Sigma is not a "get rich quick" methodology. I like to think of it like my retirement savings plan -- Six Sigma is a get rich slow methodology -- the take-away point being that you will get rich if you plan properly and execute consistently.

As GE's 1996 annual report states, "It has been estimated that less than Six Sigma quality, i.e., the three-to-four Sigma levels that are average for most U.S. companies, can cost a company as much as 10-15% of its revenues. For GE, that would mean $8-12 billion." With GE's 2001 revenue of $111.6 billion, this would translate into $11.2-16.7 billion of savings. Although $2 billion worth of savings in 1999 is impressive, it appears that even GE hasn't been able to yet capture the losses due to poor quality -- or maybe they're above the three-to-four Sigma levels that are the average for most U.S. companies?

In either case, 1.2-4.5% of revenue is significant and should catch the eye of any CEO or CFO. For a $30 million a year company, that can translate into between $360,000 and $1,350,000 in bottom-line-impacting savings per year. It takes money to make money. Is investing in Six Sigma quality, your employees and your organization's culture worth the money? Only you and your executive leadership team can decide the answer to that question

Sigma Performance Levels - One to Six Sigma

Related articles

Sigma Performance Levels - One to Six Sigma
Sigma Level	Defects Per Million Opportunities (DPMO)
1	690,000
2	308,537
3	66,807
4	6,210
5	233
6	3.4

What Would This Look Like In The Real World?

It's one thing to see the numbers and it's a whole other thing to see how it would apply to your daily life.

Real-world Performance Levels
Situation/Example	In 1 Sigma World	In 3 Sigma World	In 6 Sigma World
Pieces of your mail lost per year [1,600 opportunities per year]	1,106	107	Less than 1
Number of empty coffee pots at work (who didn't fill the coffee pot again?) [680 opportunities per year]	470	45	Less than 1
Number of telephone disconnections [7,000 talk minutes]	4,839	467	0.02
Erroneous business orders [250,000 opportunities per year]	172,924	16,694	0.9

Inspection terms -

Acceptance Limit (c)

The upper limit on the number of non-conforming items in a sample, that would still lead to the acceptance of the entire lot. If the number of non-conforming items in the sample exceeds this number, the entire batch must not be accepted.

Average Outgoing Quality Limit (AOQL)

The highest/worst possible average percent of non-conforming items in the process, after employing some inspection scheme. This measure is usually used in rectifying inspection, where the inspection procedure changes the outgoing rate of non-conforming items in the batch or process, relative to the incoming rate. For example, by removing the non-conforming items that are encountered during inspection. Note that this is only the worse possible average percent of non-conforming items, and therefore there is still a possibility that the percent non-conforming of a single batch will exceed this limit.

Average Run Length (ARL)

The mean (average) of the run length. This is the average number of samples that are taken until an alarm is signaled by the control chart.

Acceptable Quality Level (AQL)

The maximal percent of nonconforming items (or the maximal number of nonconformities per 100 items), which is considered, for inspection purposes, as a satisfying process mean.

The AQL is generally specified by the authority responsible of sampling. Different AQLs may be designated for different types of defects. It is common to use an AQL of 1% for major defects, and 2.5% for minor defects.

Values of AQL that are 10% or less are suitable for percent nonconforming or nonconformities per 100 items. Values of AQL over 10% are only suitable for nonconformities per 100 items.

Alarm Zones

The alarm zones in an ordinary 3-sigma control chart are beyond the upper control limit (3,infinity), and below the lower control limit (-infinity, -3).

• To specify the alarm zone as the area between the warning limits and control limits, enter a=2, b=3.
• In a control chart with 0.001 probability control limits (3.09 "sigma") and 0.025 warning limits (2.24 "sigma"), the rule "two consecutive points between the control and warning limits" is given by: k=2, a=2.24, b=3.09.
• Alarm zones are usually symmetric around the center line. For example: [-3,-2] and [2,3].

Batch/Lot

A batch is a collection of items from which a sample will be drawn, for deciding on its conformance to the acceptance inspection. A batch should include items of the same type, size, etc. and that were produced under the same production conditions and time.

The batch size is the number of items in a lot or a batch.

Clearance Number

The number of consecutive items (or batches, in Skip lot sampling) that must be found conforming, in order to quit the screening phase (100% inspection) when applying continuous sampling.

Inspection Levels for Military Standard 105E (MIL-STD-105E)

The inspection level determines the relation between the batch size and sample size.

Levels I, II, and III are general inspection levels:

• Level II is designated as normal.
• Level I requires about half the amount of inspection as level II, and is used when reduced sampling cost are required and a lower level of discrimination (or power) can be tolerated.
• Level III requires about twice the amount of inspection as level II, and is used when more discrimination (or power) is needed.

The four special inspection levels S-1,S-2,S-3,S-4 use very small samples, and should be employed when small sample sizes are necessary, and when large sampling risks can be tolerated.

Inspection Levels for Military Standard 414 (MIL-STD-414)

The inspection level determines the relation between the batch size and sample size.

Levels I, II, III, IV, V are general inspection levels:

• Level IV is designated as normal.
• Level V requires a larger amount of inspection than level IV, and is used when more discrimination (or power) is needed.
• Levels I,II,III require less inspection than level II, and is used when reduced sampling costs are required, and lower level of discrimination (or power) can be tolerated.

Maximal run length value

The largest number on the horizontal axis, in the run length plot. Or, the largest value of t on the plot for which P(RL=t) is plotted. For example, selecting 500 will give a probability plot of run-lengths in the range 1,2,...,500.

Nonconforming items

The nonconformity of an item is expressed as the percent of nonconforming items. When each item can contain more than one defect, the nonconformity of an item is expressed as the number of non-conformities (defects) per 100 items.

Percent/Proportion Non-Conforming (p)

The percent or proportion of non-conforming items in a batch or in a process. In many cases this is unknown, but it is used to learn about scenarios for different values of p.

Rejection Limit (r)

The smallest number of non-conforming items in a sample that would lead to the rejection of the entire lot. In most cases (besides reduced sampling) this value is equal to the acceptance limit -1.

Run Length

The run length is the number of samples taken until an alarm is signaled by the control chart.

Sample size (n)

The number of items that should be randomly chosen from a batch.

Sampling Fraction f

The proportion of items (or batches, in Skip lot sampling) that are inspected during some phase, when applying continuous sampling. f is between 0 and 1. There are three ways to sample with a fraction of f:

1. Probability Sampling: Each item/batch is sampled with probability f.
2. Systematic Sampling: Every 1/f 'th item/batch is sampled.1/f must then be a natural number (e.g., every 3rd item is inspected, when f=1/3).
3. Block-Random Sampling: From each 1/f consecutive items/batches, one is chosen at random. 1/f must then be a natural number (e.g., in each block of 3 items one is chosen, when f=1/3).

Shift size

The purpose of using a control chart is to detect a shift in the process mean, of a specific size. To detect a shift of two standard-deviations-of-the mean, enter the value 2.

SPC

Statistical Process Control.

SQC

Statistical Quality Control.

Type of Inspection

There are three types of inspection:

• Normal inspection is used at the start of the inspection activity.
• Tightened inspection is used when the vendor's recent quality history has deteriorated (acceptance criteria are more stringent than under normal inspection).
• Reduced inspection is used when the vendor's recent quality history has been exceptionally good (sample sizes are usually smaller than under normal inspection).

What is AQL

AQL Inspection Manual

Acceptance Number

The acceptance number is the maximum number of defects or defective units in the sample that will permit acceptance lot or batch.

AQL has two different definitions due to standard changes.

MIL-STD-105E, ISO 2859-1 (1999)

Acceptable Quality Level. The acceptable level (AQL) is defined as the maximum percent defective (or the maximum number of defects per hundred units) that, for purpose of sampling inspection, can be considered satisfactory as a process average. The sampling plans most frequently used by the department of Defense are based on the AQL.

ANSI/ASQC Z1.4-2003

Acceptance Quality Limit. The AQL is the quality level that is the worst tolerable process average when a continuing series of lots is submitted for acceptance sampling.

The following note on the meaning of AQL was introduced with the ANSI/ASQ Z1.4-2003 revision.

The concept of AQL only applies when an acceptance sampling scheme with rules for switching between normal, tightened and reduced inspection and discontinuance of sampling inspection is used. These rules are designed to encourage suppliers to have process averages consistently better than the AQL. If suppliers fail to do so, there is a high probability of being switched from normal inspection to tightened inspection where lot acceptance becomes more difficult. Once on tightened inspection, unless corrective action is taken to improve product quality, it is very likely that the rule requiring discontinuance of sampling inspection will be invoked.

Although individual lots with quality as bad as the AQL can be accepted with fairly high probability, the designation of an AQL does not suggest that this is necessarily a desirable quality level. The AQL is a parameter of the sampling scheme and should not be confused with a process average which describes the operating level of a manufacturing process. It is expected that the product quality level will be less than the AQL to avoid excessive non accepted lots.

The AQL values are defined as percent nonconforming or defects or nonconformities per hundred units.

Defects and Defectives. A defect is any nonconformance of the unit of product with the specified requirements. A defective is a unit of product which contains one or more defects. Failure to meet requirements with respect to quality characteristics are usually described in terms of defects or defectives.

Critical - A critical defect is on that judgment and experience indicate is likely to:

1. result in hazardous or unsafe conditions for individuals using, maintaining, or depending upon the products; or

2. prevent performance of the tactical function of a major end item. A critical defective is a unit of product that contains one or more critical defects.

Major - A major defect is one, other than critical, that is likely to result in failure, or to reduce materially the usability of the unit of product for its intended purpose. A major defective is a unit of product that contains one or more major defects.

Minor - A minor defect is one that is not likely to reduce materially the usability of the unit of product for its intended purpose, or is a departure from established standards having little bearing on the effective use or operation of the unit of product. A Minor defective is a unit of product that contains one or more defects.

Double Sampling Plan. A double sampling plan involves sampling inspection in which the inspection of the first sample to a decision to accept, to reject or to take a second sample. The inspection of a second sample, when required, lead to a decision to accept or reject.

Drawing of Samples. Basic to sampling inspection is the assurance that the sample selected from a quantity of units represents the quality of that quantity of units. Hence, the procedure used to select units from a lot must be such that it assures a sample free of bias.

Expression of Nonconformance. The extent of nonconformance of product shall be expressed either in terms of percent defective or in terms of defects per hundred units (DHU).

Defects per Hundred Units. The number of defects per hundred units of any given quantity units of product is one hundred times the number of defects contained therein (one or more defects being possible in any unit of product) divided by the total number of units of product, i.e.:

Defects per hundred units =	number of defectives x 100
	number of units inspected

Inspection. Inspection is the process of measuring, examining, testing, or otherwise comparing the unit of product with the requirements.

Inspection by Attribute. Inspection by attributes is inspection where by either the unit of product is classified simply as defective or non-defective, or the number of defects in the unit of product is counted, with respect to a given requirement or set of requirements.

Inspection Levels. The standards provides for three general inspection levels and four special inspection levels. These seven levels permit the user to balance the cost of inspection against the amount of protection required.

Lot or Batch. The term lot or batch shall mean "inspection lot" or "inspection batch" i.e., a collection of units of product from which a sample is to drawn and inspected to determine conformance with the acceptance criteria, any may differ from a collection of units designated as a lot or batch for other purposes (e.g., production, shipment, etc.).

Nonconformance. Nonconformance may be defined as the failure of a unit of product to conform to specified requirements for any stated quality characteristic. The extent of nonconformance of product to the required quality characteristics shall be expressed either in terms of percent defective or in terms of defects per hundred units (DHU).

Normal Inspection. Normal inspection is that which is used where there is no evidence that the quality of product being submitted is better or poorer than the specified quality level.

Percent Defective. The percent defective of any given quantity of units of product is one hundred times the number of defective units of product contained therein divided by the total number of units of product, i.e.: Percent defective = number of defectives x100 / number of units inspected

Reduced Inspection. Reduced inspection under a sampling plan uses the same quality level as for normal inspection, but requires a smaller sample for inspection.

Rejection Number. The rejection number is the minimum number of defects or defective units in the sample that will cause rejection of the lot represented by the sample.

Representative Sampling. When appropriate, the number of units in the sample shall be selected in proportion to the size of sub-lots or sub-batches, or parts or the lot or batch, identified by some rational criterion. When representative sampling is used, the units from each part of the lot or batch shall be selected at random.

Resubmitted Lots or Batches. Lots or batches found unacceptable shall be resubmitted for reinspection only after all units are re-examined or retested and all defective units are removed or defects corrected. The responsible authority shall determine whether normal or tightened inspection shall be used and whether reinspection shall include all types or classes of defects or only the particular types or classes of defects which caused initial rejection.

Sample. A sample consists of one or more units of product drawn from a lot or batch, the units of the sample being selected at random without regard to their quality. The number of product in the sample is the sample size.

Sampling Plans. A lot sampling plan is a statement of the sample size or sizes to be used and the associated acceptance and rejection numbers.

Single Sample Plan. A single sampling plan is a type of sampling plan by which the results of a single sample from an inspection lot are conclusive in determining acceptability. The number of sample units inspected shall be equal to the sample size given by the plan.

Severity of Inspection. The severity of inspection concerns the total amount, kind and extent of inspection specified by the quality assurance provisions established for the unit of product, or as dictated by quality history.

Unit of Production. The unit of product is the thing inspected in order to determine its classification as defective or non-defective or to count the number of defects. It may be a single article, a pair, a set, a length, an area, an operation, a volume, a component of an end product, or the end product itself. The unit of product may or may not be the same as the unit of purchase, supply, production, or shipment.

Tightened Inspection. Tightened inspection under a sampling procedure plan uses the quality level as for normal inspection, but requires more stringent acceptance criteria

introduction to this blog

I started this blog to post apparel / Home textile related / stitching related articles based on my experience.

I have rich experience in Spinning / weaving / Final Fabric Inspection / Stitching industry.

Currently working in a composite textile mill as Quality Assurance Manager.

Basically i am a Diploma holder in textile technology, then I got my BBA, GMTA, and a Certificate course in Apparel Manufacturing Technology and currently doing my MBA.

I hope i can help all persons related to Apparel Quality Assurance through this blog by posting various articles in future.

Happy learning