100% inspection and measurement error ++ Automating quality


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MAY 3, 2011 — This issue sponsored by TechnorazziLIVE featuring Zeiss
Today’s Top Story

comingtompicspacer100% Inspection and Measurement Error
How to handle the problem of misclassified product
by Donald J. Wheeler

One-hundred-percent inspection is commonly used to avoid shipping nonconforming product. Each of the items produced is measured and judged to be either conforming or nonconforming. The conforming items get shipped, and the nonconforming items get set aside for use as factory-authorized replacement parts or some other equally ignominious fate. It all seems quite simple until you do the math. The purpose of this article is to show what happens when a product stream is subjected to 100-percent screening inspection with less-than-perfect measurement systems. [full story]

videos
Featured Video:
Minitab Quality
Companion: Value
Stream Mapping

[click to view]
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Live Video Event
Quality Digest Live
April 29, 2011

[click to view]
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TOP FIVE STORIES

  1. Root Cause Analysis, Part 2: Critical Success Factors
  2. Root Cause Analysis, Part 1: Technique
  3. Your Process Lies
  4. What Did Deming Really Say?
  5. De-Stress for Success

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CONTEST!
REDEFINE QUALITY

Try thinking outside the QC glossary. Take a quality term and then add, subtract, or change one letter of it. (You may only make one of those changes per word.) Give it a new definition. Send your terms to qdcontest1. We’ll publish the three best definitions next month and ask you to vote on the winner. The winner will receive a TomTom GPS. Contest ends May 25.

Here are some examples to get you started. Good luck!

1. Stadistical: Inflicting complicated equations on a captive audience

2. Root clause analysis: Trying to figure out which section of a standard is the most confusing.

3. Dimention: A particularly brainless suggestion made at a meeting.

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BRAINGAMES

Need a break from serious number-crunching? Since sociologists have determined that humans work best in on-off cycles, we’re offering some weekly downtime along with our daily quality news. Check it out—you may become more productive.

1. Points of Order: Deming’s 14
2. Bionic Arm Design Challenge

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ODDS & ENDS

News bits for the water-cooler crowd

Danish tech company is revolutionizing pitching data

But it ain’t over till the fat lady weighs in.

Learning science through gaming
Why didn’t they teach us like this back in the day?

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IMAGE OF THE WEEK

Nocturnal Aye Aye lemurs are famous for their thin, spidery middle fingers, which they use to detect hidden prey like beetle grubs. The finger is packed with sensitive nerve endings so it uses a lot of energy, and like any delicate device, it is best turned off when not in use. This thermal image shows substantial temperature differences in a Duke Lemur Center Aye Aye’s right middle finger (near its nose), which is warming to probe a treat it has been offered.

Send pictures to:
qdpictures

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comingtompicspacerAre You a Sheet or Shelf Thinker?
How you think will govern organizational performance
by Tripp Babbitt

My first job was in industrial distribution, and with distribution came learning to count inventory. An annual inventory tax was levied, so an accurate count was important. I was given a computer list of items to count. An important lesson I learned was that to get an accurate count, there was a right and wrong method. [full story]

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ADVERTISEMENT

buttonadpicspacerTechnorazziLIVE
Join us for a Live one-hour video presentation on May 4 at 1:00 p.m. EDT
by TechnorazziLIVE featuring Zeiss

1:00-1:30 p.m.—See the benefits of using MCC to manage your measuring systems, including machines, programs, and results.

1:30-2:00 p.m.—Get a live demo of out ACCTee software on the high-accuracy integrated Surface 2000 texture and contour measuring system.

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comingtompicspacerAutomating That Quality Job
Robots are finding their way into consumer manufacturing, including quality assurance
by Robotics Industries Association

As robots and their control systems become more powerful and flexible, robotics are moving from heavy industrial applications into producing consumer products we all use in our daily lives. Fickle consumers demand products in new forms, which plays to the strength of robotics’ inherent flexibility to change while keeping production local. Vision-enabled robots are also used in warehouse distribution systems and to test consumer goods for quality control. [full story]

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News — Products — Events

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Highlighted Event

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Free Leadership E-book From ASQ

ASQ, the leading community of people passionate about quality, is offering you an exclusive e-book. In this book, Finding the Leader in You, you will discover the leadership skills within to become an effective leader in today’s rapidly changing world of business. Get more tools and resources as an ASQ member. If you are looking for the most up-to-date training, certifications, publications, and knowledge on topics such as Six Sigma, lean, process improvement, and social responsibility, ASQ is your resource. Click here to download and learn how ASQ can give you a strong competitive advantage. Demonstrate your commitment to quality to help you take your career and organization to the next level and continue to raise the voice of quality worldwide.

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Coming Tomorrow

comingtompicspacerAn Interview with Donald J. Wheeler
The statistician talks about Deming, quality issues, and his own interesting career
by Dirk Dusharme

Donald J. Wheeler has been awarded the Deming Medal by the American Society for Quality for "the propagation of Dr. Deming’s ideas throughout the world through his numerous books and seminars on quality management and statistical quality improvement." Here he answers some questions for Quality Digest Daily.

3D Scanning Glossary


* 2D Drawing – A 2D representation of a CAD model typically complete with measurements and dimensions for use in many manufacturing processes.

* 3D Laser Scanner – A 3D scanning device that uses a laser to reflect off the part and triangulate with a camera lens, allowing the scanner to determine and create XYZ coordinates. The scanner then uses these points to form a 3D digital model of the part.

* 3D Modeling – 3D modeling refers to the creation of three-dimensional objects that are defined mathematically and geometrically (i.e. a circle extruded to a certain value to create a cylinder defined by its location, radius and length). 3D modeling can be aided by the use of scan data (see Reverse Engineering).

* 3D Scanner – 3D scanners come in many forms, but the purpose of every one of them is to capture the shape, and sometimes color, of real-world physical objects or environments. This captured data is typically stored as a list of xyz-coordinates in a point cloud file. 3D scanners can be categorized as contact (CMM arms) or non-contact (white light, 3D laser scanners, or stereo-vision based). Some can even capture internal features. "3D scanner" is sometimes mispelled as "3D scaner".

* 3D Scanning – 3D scanning is the fast and accurate process of using a 3D scanner to capture and convert physical objects into digital 3D data.

* Accuracy – The accuracy is the closeness of a measurement to the actual feature. The opposite of accuracy is uncertainty, which is an inverse perspective of the same value. See Uncertainty.

* Alignment – The process of aligning two objects in a common coordinate system. Commonly refers to aligning scan data to reference objects in inspection applications.

* As-Built – An object’s real-world condition and appearance.

* As-Designed – How the object was originally designed, usually in a CAD environment.

* Auto Surfacing – Wrapping a patch-work quilt of freeform NURBS surfaces around scan data, quickly and automatically generating surfaces.

* CAD – Computer Aided Design. CAD is a standard term defining a group of software that aides in design. CAD software is what is used for 3D modeling and to create 2D drawings. It is typically used in manufacturing or other engineering disciplines. For example: An engineer designs in SolidWorks, Pro-E, AutoCAD, CATIA, or Unigraphics; all of which are CAD or CAE programs. Often confused with CAE.

* CAI – Computer Aided Inspection. CAI is a set of technologies that convert designs into data used to run the inspection process.

* CAM – Computer Aided Manufacturing. CAM is a set of technologies that convert designs into data used to run the manufacturing process.

* CAQ – Computer Aided Quality Assurance / Inspection / Control. See CAI.

* Class A – The most simple mathematical curve or surface that can describe a shape. Example: A customer requests a "Class A" IGES surface when he needs a super smooth surface typically used in aerospace or automotive applications.

* Color Map – A color plot visually representing deviations from actual to theoretical. Example: A customer requests a colormap inspection when needing to compare an as-built object to its as-designed CAD data.

* Computational Fluid Dynamics (CFD) – Computational fluid dynamics is the study and analysis of fluid and gas flow in a system with the use of numerical methods algorithms. Computers are required to handle the millions of calculations involved in CDF analysis with applications such as aerodynamic (wind tunnel) and hydrodynamic testing. It is common to use a 3D scanner to capture object surface data for use in such tests.

* Datum – A certain feature such as a point, line, plane, cylinder, etc. that can be used to establish the location or geometric relationship of another feature.

* Decimation – Decimation in general refers to reducing the number of samples in a population. In 3D scanning, decimation usually refers to lowering the number of triangles on a surface without distorting the detail or color. Decimation is used when there are a large number of unnecessary triangles.

* Degrees of Freedom – Describes the numbers of directions of movement and refers to how the position and orientation of an object is described relative to a coordinate system. In 3D scanning it usually consists of three linear translations (X, Y, and Z) and three rotations about the three axes (pitch, yaw, and roll).

* Deviation – As typically applied to 3D scanning, deviation refers to the difference in the size and shape of a manufactured part versus its design specifications. Deviation is easily discovered by quality inspection with the use of color maps and cross-sectional analysis found in CAI applications.

* Digital Archiving – Storing data digitally. Objects can be scanned and processed for digital archiving purposes, reducing the need to store physical parts in locations such as a warehouse.

* "Dumb" IGES – "Dumb" IGES is a term used to refer to any IGES, STEP or other surface file format. Though technically a mathematical model, it is considered "dumb" because the data contains no parametric history of the model; it is simply a surface that cannot be intelligently edited. Ex: If a cylinder is modeled in 3D and exported in .IGES file format, the cylinder cannot be edited by changing its radius or extrusion length.

* FEA – Finite Element Analysis. When a surface model is subjected to various tests to determine or establish its integrity under specified conditions.

* FEM – Finite Element Model. The creation of a mathematical surface description of an object resulting in a model ready for analysis.

* Fillet – A surface that connects two or more faces. This surface is usually an arc.

* Geometric Dimensioning & Tolerancing (GD&T) – Geometric Dimensioning and Tolerancing is a standard used to define the nominal geometry of parts and assemblies, to define the allowable variation in form and possibly size of individual features, and to define the allowable variation between features.

* Hybrid Surface Model – An IGES or STEP surface that usually combines auto-surfaced features with typical 3D modeling operations. Hybrid models are "dumb" because the data contains no parametric history of the model; it is simply a surface that cannot be intelligently edited. Such models have areas that are not ideally mathematical in nature, and instead are composed of NURBS surface estimates of the scan data.

* IGES – Initial Graphics Exchange Specification / System is a standard mathematical surface file, used for over 25 years in most CAD systems to mathematically represent physical data. It is the most common format for exchanging CAD data between software programs. See also STEP.

* Inspection – See Quality Inspection.

* Laser Scanner or Laser-Line Scanner – See 3D Laser Scanner.

* Legacy Part – A part that is already created or existent in the customer environment. As typically applied to 3D scanning, legacy parts usually do not have CAD data.

* Median Part Verification – When several of the same parts are scanned and the resulting data is averaged and used to create one representative 3D model. Median part verification is used to minimize the effect of manufacturing defects on the resultant model.

* Merge – Combining two or more scan data sets into one larger data set.

* Mesh – See Poly-mesh.

* Noise – Noise is the existence of extraneous recorded data within a point cloud. It can be caused by an object obstructing the sensor or ambient light and reflections into the sensor during the data capture process.

* NURBS – Non Uniform Rational Basis, or Bézier Spline. It is a mathematical model commonly used for generating and representing curves and surfaces that cannot be decimated in a uniform manner. It can also be a surface created by two or more b-splines. First developed mid-century but didn’t arrive on the desktop until 1989.

* Organized STL – Mesh data consisting of point cloud data with mathematical point spacing based on surface data. An organized STL of a cube would consist of 8 points (1 for each corner).

* Parametric Model – A data set that retains the history of how it was designed, so that modifications update all downstream features. Exchange of such models is supported by IGES. SolidWorks is a software program that is popular for creating and modifying parametric models.

* Performance Surfaces – Surfaces that are affected by certain aerodynamic and hydrodynamic forces. The shape of these surfaces is usually key to the performance of the object.

* Photogrammetry – The process of taking precise measurements by using digital pictures and coded targets. For 3D scanning purposes, the coded targets and reference markers in the picture frame serve as anchor points where scans can be aligned to. Photogrammetry ensures extremely accurate scan data. Also see Videogrammetry.

* Precision – The repeatability of performing a measurement.

* Point Cloud – A point cloud is the computer visualization of the XYZ coordinates that describe a physical object or environment. Each point represents an actual point on the object or in the environment, and collectively describes its shape and measurements. Points can be captured individually, such as with a CMM, or thousands at a time, such as with a 3D laser scanner that captures multiple point sets from different perspectives that can be merged into a cloud. Point clouds are typically represented by an unorganized STL file. Synonomous with raw scan data.

* Poly-mesh – A polygonal model that is used in 3D computer graphics. A mesh is a visualization of point cloud data that basically connects the dots to form triangles. See also STL.

* Quality Inspection – The process of evaluating a physical part and comparing it to the design specifications that are described in the object’s CAD file. Inspection is an "as built" vs "as designed" comparison. See also Deviation.

* Rapid Surfacing – See Auto Surfacing.

* Reference Markers – Adhesive backed retro-reflective dots used in 3D scanning applications to create reference points and help align pieces of scan data. Some scanners, such as the Handyscan 3D, use reference markers to position themselves in space, eliminating the need for attachment to a CMM arm or a fixed focal length.

* Registration – The process of aligning two data sets together based on known coordinates in each. Registration enables the alignment and integration of two of more point cloud data sets to complete larger models that must be captured in multiple scans.

* Rendering – A graphical representation of a computer model. It is often used to describe the visual output of CAD and Modeling software. By rendering a computer model, you can often add characteristics and effects to its surfaces and features.

* Resolution – The spacing of points in a grid. The higher the resolution, the more data that will be captured. Likewise, the lower the resolution, the "flatter" the detail.

* Reverse Engineering – Reverse engineering broadly refers to analyzing and dissecting something with the goal of recreating it. In 3D scanning, reverse engineering typically means the process of measuring an object using a 3D scanner and then creating CAD data that reflects its original design intent. This can also be done by using rulers, calipers, or a CMM. Reverse engineering is sometimes referred to as Reverse Modeling.

* Reverse Modeling – See Reverse Engineering.

* Scan – Measuring the part, capturing data, and transferring the measured points to the computer. It also refers to the computer file that is based on the physical part, i.e., xyz coordinates that represent physical measurements taken by the scanner.

* Shell – A particular operation for CAD. In 3D scanning, involves the creation of an offset surface from the original surface in order to create thickness.

* Shrink Wrap Surface Model – Refers to the way in which 3D scanning software like Geomagic, RapidForm, and Paraform fit mathematical IGES surfaces to a "physical" scan. Similar to how plastic shrinkwrap "shrinks" down onto a part being "wrapped".

* Stereo Vision – A method of capturing three dimensional data based only on cameras. An algorithm of stereo vision involves receiving inputs from two or more different cameras oriented at different angles and analyzing the differences between the images to obtain 3D information. This 3D information is easily read as a 3D point cloud.

* STEP – Standard for the Exchange of Product Model Data is a comprehensive ISO data standard (ISO 10303) for the exchange of object descriptions between systems. STEP is a file format that is usually interchangeable with IGES.

* STL – Standard Tessellation Language. STL is a special internationally recognized file format that stores XYZ coordinate measurements and their normals. Gives the added functionality beyond XYZ coordinates enabling visualization of a part’s "front" and "back." STL is the standard file format for rapid prototyping, and is used in reverse engineering. See Organized STL and Unorganized STL.

* Surface – Refers to the part being scanned or to the computer file from the scanner. It typically means a computer file in IGES format. See also IGES.

* Surfacing – The process of defining or creating a surface on a CAD model. Typically refers to converting a polygonal representation of an object to a NURBS or other mathematical representation. It is the process of converting physical based 3D data to mathematical based 3D data. See also Auto Surfacing and Reverse Engineering.

* Talc – Talc powder is typically applied to translucent, reflective, or black/near-black objects during the 3D laser scanning process in order to improve the ability of the laser scanner to capture data. Talc powder is predominantly white and is usually applied with a pen or an aerosol spray. Talc can easily be wiped off and cleaned, and generally will not damage an object.

* Targets – See Reference Markers.

* Tessellation – Generally refers to filling a surface plane or surface with shapes that create no gaps or holes. In 3D scanning, this concept applies to wrapping a mesh around a CAD body. A jigsaw puzzle is a great real world example of a collection of tessellated shapes.

* Time of Flight – 3D laser scanners that calculate measurements based on the time it takes for the laser beam to detect a surface and report back.

* Touch Probe – A Coordinate Measuring Machine (CMM) that requires physical contact with the part to measure it.

* Triangulation – Using trigonometric functions to calculate measurements, used in certain types of 3D laser scanners to determine point locations based on transmission and reflection positions of the laser beam. In 3D modeling, triangulation also refers to the generation of triangles out of point cloud data in creating 3D surfaces.

* Uncertainty – The uncertainty is the quantity of how much a measurement is unknown compared to the actual feature. Uncertainty is the inverse perspective of accuracy, which is defined as the closeness of a measurement to the actual feature. The uncertainty essentially describes how much of a measurement is uncertain. See Accuracy.

* Unorganized STL – Mesh data based on point cloud data taken from a scan. Point spacing is based off the number and resolution of scans and not dependant on the shape or features of the object being scanned.

* Videogrammetry – The process of taking precise measurements by using video images taken from two or more video cameras taken at different angles.

* Watertight – Refers to mesh or surface data that does not contain any holes much like a real object’s ability to hold water.

* White Light Scanning (Interferometry) – Optical non-contact method for measuring physical parts. White light scanners obtain measurements of an object by determining changes in the fringe and distortion of a pattern of white light projected on an object

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