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The case for optical CMMs.

The case for optical CMMs

A common question is when to use machine vision for quality-control measurement. Although it is not a panacea for all your quality requirements, there are areas where machine vision excels, plus new areas where it is becoming more competitive as sophisticated systems become simpler to use and less expensive.

Off-line optical CMMs are based on a video camera and image processing, and fully automated; i.e., programmed to go to a measurement position, and then automatically focus on the desired part feature to get a precise reading. The accuracy of their three-dimensional measurements is based on three-axis positioning tables. They are excellent at measuring minute features and complex geometries, for example, checking parts from high-speed stamping presses, vertically milled parts, form-tooled rotary parts, and miniature-to medium-sized EDMed parts.

Although on-line or in-line vision systems are used in some manufacturing and assembly operations, three-dimensional optical CMMs are used off-line, monitoring metal-stampings, machined castings, and fine-blanked or screw-machined parts.

The optical CMM has obvious speed, accuracy, and SPC advantages over optical comparators, toolmaker's microscopes, and manual gages. It also offers flexibility, through its software, for handling many different types of measurements. First-part inspection, carbide-insert inspection of cutting tools, and die- or mold-wear monitoring can be performed with a single measurement system instead of an array of electronic, mechanical, or functional gages.

The optical CMM can be quicker than the touch-probe CMM, with one-dimensional measurements--between two points or a hole diameter--made in approximately 1 sec. For example, in one case, an optical comparator was required for each of ten stamping presses producing electrical terminals. Now, a single vision system handles the output of all ten presses.

Accuracies are typically better than optical comparators, touchprobe CMMs, and toolmaker's microscopes. A good optical CMM can deliver accuracies of plus or minus 0.000 16" in the X and Y axes and plus or minus 0.000 20" in the Z axis. Repeatability is plus or minus 0.0001" or better.

Most optical CMM manufacturers offer SPC packages to collect and display data based on some sampling procedure. The resulting documentation is becoming increasingly important in the auto, electronic, aircraft, and defense industries. It not only provides important feedback on the production process, but enables their users to become more competitive in meeting most sampling plans and SPC requirements demanded by today's requests for quotations.

User resistance

Despite these advantages, most metalworking shops have been reluctant to adopt machine-vision technology. Part of this is a belief that these systems are too complex and difficult to operate; that someone versed in computer programming is required to establish part-inspection programs. Also, initial cost of these systems has been in the $100,000 and up range.

Recent technological developments and manufacturing efficiencies are overcoming these objections. The cost of a full-featured, automated, optical CMM can be less than $65,000. This is making machine vision more affordable to the smaller shop and puts it in the price range of the touch-probe CMM and optical comparators.

Additional improvements have been made in machine programming and user interfaces. Extensive software development is making part inspection programming more user friendly and simple to use. On-screen menus provide easy-to-understand instructions for part programming, with features built in to reduce the number of steps and their complexity. The result is a system easier to learn and use.

Quality has become increasingly critical to manufacturing competitiveness. Just as the manufacturers of machine tools have embodied quality in their tools, machine-vision developments are offering an advanced measuring tool to monitor the quality of the work produced on these tools. It is flexible, less expensive and easier to use, and has demonstrated its ability to improve quality and productivity.

Other vision products:

Optical CMM software

Veristar, a targeting technique and software package, allows a Data-Cam quality measurement system to function as an optical CMM, either in-line or off-line. Precisely calibrated to a fixture point, it reports part-feature position in absolute spatial coordinates compatible with CAD data, accommodating nonprecision fixturing of parts. This permits measuring the dimensional mean as well as variance about the mean, and making process adjustments to restore the mean to target value. According to the system manufacturer, this approach is one of the least expensive of major measurement technologies and can be used in-line to measure 100 percent of part production.

Perceptron, 23855 Research Dr, Farmington Hills, MI 48024 or circle 435.

Solder-joint inspection

HR-2000 three-dimensional vision inspection system makes automatic joint-quality decisions based on thousands of 3-D X, Y, and Z measurements of a given joint. Expert-system software evaluates joint quality based on surface characteristics, and this can be used as a statistical process control tool.

Robotic Vision Systems Inc, 425 Rabro Drive East, Hauppauge, NY 11788 or circle 456.

Gage amplifier

Model 1025 electronic amplifier simplifies differential, comparative, or absolute measurements. It features digital/analog display, automatic or manual range selection, auto zeroing, limit indicator lights, and the ability to calculate maximum, average, and minimum values, TIR, difference, and SPC calculations.

Brown & Sharpe, Precision Tools Div, Precision Park, N Kingston, RI 02852 or circle 473.

Light sources

Six designs of industrial light sources for machine-vision applications provide direct, diffused, collimated, patterned, and fiber-optic illumination. They have a 10,000-hr mean time between failure (MTBF) and can be easily replaced. They meet NEMA 4 requirements, operate on 12-V AC or DC, and are shock and vibration resistant.

Micro Switch, a Honeywell Div, 11 W Spring St, Freeport, IL 61032 or circle 453.

Flexible gaging

Multispec high-precision gaging system for small parts and tools eliminates such contact-gaging problems as part damage, poor repeatability, operator fatigue, and slow speeds. Measurements can be made to 0.0001" in two or three dimensions, based on five axes of linear, rotary, or part-motion flexibility. The system provides the precision of a CMM without its setup time, operator involvement, or contact probes. Software automatically locates the part in the gaging envelope. Developed to inspect drill bits, the system has be used to measure turbine blades, precision fasteners, nozzles, and other tight-tolerance parts.

Automatix Inc, 1000 Tech Park Dr, Billerica, MA 01821 or circle 442.

Tool measurement

Tool Measure 2000 is an optical inspection system for drill bits, reamers, end mills, and taps. It uses a reticle projected onto a video display. A rotary collet provides tool rotation and a precision rotary table provides 90 deg positioning. Position linearity is 0.000 080 ipi and position repeatability is 0.000 020". A microcomputer performs geometric functions, stores program commands, and provides pre-programmed X,Y coordinates.

Measurement Concepts Inc, 9100 Independence Ave, Chatsworth, CA 91311 or circle 444.

Motion analysis

To keep on the cutting edge, Urschel Laboratories uses high-speed motion analysis to study high-speed food-slicing equipment (shown here, a pickle slicer making 554 cuts/sec). They use a Kodak EktaPro 1000 system to study the dynamics of variety of cutting machines and make quick fine-tuning adjustments. The analyzer records 1000 full frames/sec or 6000 partial frames/sec on 1/2" video tape that can be viewed in a variety of slowmotion modes. The readily portable system consists of a camera, processor/recorder, and monitor.

Eastman Kodak Co, 343 State St, Rochester, NY 14650 or circle 440.

Rapid CMM

RMS rapid metrology system measures gears, cams, turbine blades, prismatic parts, and sculptured surfaces. It features air bearings; a work envelope of 20" X, 16" Y, and 12" Z; accuracy of 0.0003"; repeatability of 0.0002"; and good dimensional stability and rigidity. Handheld microprocessor handles basic measurements, delivers hard-copy documentation, and provides touchscreen input and display. Sceptre probe offers 0.5-micron accuracy, 0.2-micron repeatability, and 50 data sets/sec data rate.

L S Starrett Co, 121 Crescent St, Athol, MA 01331-1915 or circle 471.

Sheet-metal inspection

Fabrivision uses machine vision to inspect flat sheet-metal parts up to 48" X 72" X 1/4" thick in less than 5 min without programming, setup, or clamping. Points are sampled every 0.001" and all information digitilized for analysis and comparison with pre-defined specifications. A monitor displays a graphic representation of the part, or a dimensioned drawing.

Metalsoft, 2110 S Yale St, Santa Ana, CA 92704 or circle 455.

Video inspection

Videoscope 12-12-12 automatic three-dimensional system increases inspection speed 100 percent over previous models. Parts can be inspected hundreds of times faster than manual methods, without operator judgement affecting results. System features a granite-based stage (center-driven by a leadscrew), digitally controlled top and bottom lighting, automatic part alignment and levelling, and linear stage-motion correction software. Accuracies range from plus or minus 0.0002" to plus or minus 0.000001" over a 12"-cube envelope. Menu-driven software includes SPC functions as a standard feature. Options include a microscope, macro optics (long working distance), and flaw-detection scales.

Matrix Videometrix, 5321 Sterling Center Dr, Westlake Village, CA 91361 or circle 443.

Measuring probes

A new line of carbide-, sapphire-, and nylon-tipped probes for CMMs and dial-test indicators covers 600 standard items and additional specially designed probes. Also available are master ball sets, basic references for roundness, sphericity, and diameter, and ball plug gages for go/no-go measurement of IDs and checking balls for inspection fixtures.

Industrial Tectonics Inc, P O Box 1128, Ann Arbor, MI 48106 or circle 470.



Laser interferometer calibration system, for use on machine tools and CMMs, features reduced size, flexible operation, resolution of 1 nm, and speeds to 1 m/sec. The basic system includes the ML10 stabilized measurement laser, a range of optical components, EC10 sensor system for environmental compensation, and support software. Options include the CS10 stand-alone display/computer, PC10 personal-computer, and components for measuring displacement, velocity, angle, straightness, squareness, parallelism, pitch, and yaw.

Renishaw Transducer Systems Ltd, Gloucester St, Wotton-under-Edge, Gloucestershire GL12 7DN, United Kingdom or circle 462.

Video borescope

Sectional borescope with 0.001"-resolution optics, videocamera, and ultraviolet penetrant inspection capability handles a wide variety of optical evaluations. Basic 3-ft instrument can be extended with 3-ft or 5-ft sections to lengths up to 150 ft. Freeze frames of the borescope's magnified closeups can be made from videotapes and blown up to even greater size.

Lenox Instrument Co Inc, 265 Andrews Rd, Scottsville Industrial Park, Trevose, PA 19047-3427 or circle 464.

Gaging computer

PC-based Kurt Check gaging computer supplies geometric-tolerance checkpoints and SPC data and charts in real time to ensure zero-defect production. Custom interface cards functionally replace gage amplifiers or signal-conditioning electronics. Each workstation accommodates up to 32 probes from multiple jig fixtures, and one unit can provide process control for several machining stations. Geometric tolerancing generates a single, real-time QC data value from multiple probes in the fixture, eliminating the need for operators to make multiple calculations.

Kurt Mfg Co, 211 St Anthony Blvd, Minneapolis, MN 55418-1197 or circle 463.



Q-See Turbo high-speed video system has a dual-magnification optical system: a 10-mm field of view with 0.002-mm resolution and 1.25-mm field with 0.0005-mm resolution. Seven light sources provide flexible illumination, including collimated backlighting, oblique fiber-optic illumination, and grid projection. In one case, a complex turned part with 32 dimensions was checked in 1.67 min. Measurement software incorporates ANSI Y14.5 and ISO geometric tolerancing for flatness, straightness, parallelism, perpendicularity, roundness, concentricity, angularity, true position, profile, and symmetry. Statistical software is an option.

Optical Gaging Products Int'l Inc, 850 Hudson Ave, Rochester NY 14621 or circle 438.

Dimension and flaws

RM 1000 vision system can make complex dimensional and flaw-analysis measurements at production-line speeds up to 2000 units/min. Revision 3.0 software provides asynchronous capability, accepting part-detect signals in any order. It also adds on-screen statistical reports, and enhanced windowing for surface-flaw analysis. An "electronic prism" module combines several fields of view into one frame. Calibration can be done at the production line by positioning a standard part in front of the camera without using calibration fixtures. Enhanced host communications link the system through an IEEE 488 interface to other factory-floor devices.

Videk, 1100 Corporate Dr, Candaigua, NY 14425-9597 or circle 436.

Concentricity checks

MRV-10 spin-roll rotary V-block inspection gage is only 3 1/8" high. It quickly loads/unloads small cylindrical parts, such as printed-circuit-board drill bits, and measures straightness and concentricity to 0.000 05" TIR. Three intermeshing contact rolls rotate the workpiece on its circumference. Gage can be mounted vertically or horizontally and accomodates body diameters from 1/64" to 1/4" and lenghts from 1 1/16" to 3".

St Mary Mfg Corp, 390 Sweeney St, N Tonawanda, NY 14120 or circle 468.

Measure 30-inch parts

Precis 3000 vision system measures parts to 30" X 30" X 6" to accuracies of plus or minus 0.0002" in all three axes. It is designed to handle everything from printed-circuit boards to large metal stampings and multiple parts mounted on a worktable. HIP, a semiautomatic hole-inspection software program, reduces programming time by automatic recognition of part features. Five choices of lenses have fields of view from 0.013" to 0.259". Three-dimentional staging is based on an NBS-traceable, 1-micron resolution linear scale. An SPC package is optional.

View Engineering Inc, 1650 N Voyager Ave, Simi Valley, CA 93063 or circle 437.

Stamping inspection

Autospec II vision inspection system is for flaw detection and gaging of metal stampings, sintered-metal parts, and castings. Fabricated panels up to 60" square can be checked for cut-out, louver, and hole sizes to a few thousandths of an inch, at cycle times of 90 sec for 300 features. Defects are CRT displayed and marked on the part by a stamp. Motion, sequencing, and communication of results to the manufacturing process are PC/AT computer controlled, with storage for dimensional information for over 50 panels. SPC software is available.

Shaum Mfg Inc, 1127 N Nappanee St, Elkhart, IN 46514-1798 or circle 451.

Industrial camera

High-resolution CCD monochrome camera with an electronic shutter is for manufacturing, pattern recognition, and image processing applications. Shutter speeds are 1/250, 1/500, and 1/1000 sec, with interlaced or non-interlaced scanning. Standard sensitivity is 150 lux (f5.6) and minimum illumination is 2 lux (f1.4). Pixel array is 728 horizontal and 492 vertical. Designed for industrial environments, the camera is compact (2" high) and weights 0.7 lb.

NEC America Inc, 1255 Michael Dr, Wood Dale, IL 60191 or circle 452.

CMM software

Concerto measurement software includes modules to measure, analyze, provide output, and assist the CMM operator. Machine motions are automatically modified to achieve correct probing trajectories and optimum probing pressure. Eight additional programs can be accessed to integrate specific measuring processes such as gear shapes or compound surfaces.

American SIP Corp, Dept P-129, 530 Saw Mill River Rd, Elmsford, NY 10523 or circle 479.

Surface inspection

WI-300 system for automatic surface-defect inspection of flat-rolled steel, galvanized or plated steel, and stainless provides real-time video display of scratches, bruises, dents, and other defects. The system assists the operator in classifying defects for more effective control over line conditions and reduced scrap. Single or dual video cameras resolve defects as small as 0.030" at line speeds over 8000 fpm.

Aerodyne Products Corp, 76 Treble Cove Rd, N Billerica, MA 01862 or circle 454.

Roundness measurement

Talyrond 250 measuring system has automated features for roundness and geometry inspection both on the shop floor and in metrology labs. Measuring internally or externally, it provides analyses of roundness, vertical straightness, squareness, flatness, parallelism, co-axiality, concentricity, run out, and harmonics with high resolution, graphics display, and automatic centering and axis alignment.

Rank Taylor Hobson Inc. 411 E Jarvis Ave, Des Plaines, IL 60018 or circle 466.

Other quality products

Surface measurement

Pocket Surf portable surface-roughness gage provides traceable measurements on a variety of surfaces, including small IDs. Weighing 14 oz, it operates on a 9-v battery, may be held in any position, and can be used with or without a fixturing stand. Four probe positions--extended, 90 deg, 270 deg, or closed--provide measuring flexibility. Standard probe is used for flats, ODs from 1/4" and IDs from 3/4", and additional probes handle sharp edges and smaller bores.

PHOTO : Ring light with independent lighting angle and intensity in each quadrant enables View's BaZic 8 optical CMM to measure dimensions on the highly reflective machined top surface of this casting.
COPYRIGHT 1989 Nelson Publishing
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Title Annotation:coordinate measuring machines
Author:Seifert, Charles
Publication:Tooling & Production
Date:May 1, 1989
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