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Trends in laser measurement.

Trends in laser measurement

The laser has been a major boon to measurement. It's coherent light has enabled us to measure a few inches of sway in skyscrapers miles away, pace off great distances with accuracies down to a single wavelength, and split hairs inside miniature molecules. For metal-working, it has meant a new era of precision devices to align tools, digitize prototypes, and measure dimensions in millionths.

This review of laser-based measurement instruments and systems will help shed new light on what laser measurement can do for metal-working.

Laser replaces digitizing probe

A new laser digitizer for vertical milling machines and machining centers is replacing the conventional contact stylus. The result is improved accuracy and speed of gathering dimensional measurement (grid of points) of surface information for toolmaking. In combination with the machine controller, it gives the user the ability to select a variety of cutting tools for the task at hand, plus the flexibility to modify or manipulate surface information to improve the contour or shape details of molds, patterns, dies, models, or prototypes.

The laser probe transmits measurements up to 30 times faster than mechanical digitizing. The information is stored on a hard disc and used by the control to direct cutting operations. The laser probe is offered as an optional machine attachment and offers these advantages: 1. Improved tooling accuracy. 2. Improved tooling productivity (by a ratio as large as 8:1) with the faster digitizing speed. 3. One scan is sufficient to create the tool path for any kind of tool, and to make male and female molds, left-or right-handed parts, allow for shrinkage, and stretch mold dimensions. 4. Surface data is easily downloaded to CAD/CAM workstations for further analysis or shape modifications.

Previously, contact probes measures these dimensions and part shapes, moving along the part in constant physical contact. Because the probe could not make measurements in hard-to-reach areas, such as corners, the data was usually incomplete. Also, cutter offset capabilities for mechanical probes was very limited.

In contrast, the laser probe eliminates many of these deficiencies. Mounted in the spindle of the mill or machining center, it is a solid-state device for semi-continuous scanning, creating a high density of measured points. It emits a laser beam at a fixed distance (focal point) from the part. This distance is the basis for dimensional measurements interpolated to define shape and form of the part.

As the machine moves the probe in a scanning orbit, the data is stored in the host computer's hard disc. This data is then processed to create tool paths for both roughing and finishing operations using a wide variety of cutters (including ball nose, bull nose, flat, and taper).

When scanning is complete, the probe is removed from the spindle, replaced by cutting tools, and milling is ready to begin. The machine operator inputs the required cutting parameters and starts the machining cycle.

An AT-compatible PC stores the dimensional data and numerical code on a hard disc, offloading it as required to the machine controller via a high-speed RS-232 link. The laser-digitizing probe can be retrofitted to existing vertical milling machines and centers.

Sharnoa Corp, 23996 Freeway Park Dr, Farmington Hills, MI 48024 or circle 468.

Surface mapping

Three-dimensional surface mapper can measure objects at the rate of 15,000 3D points/sec and convert those measurements into CAD format. This speed is particularly important with complex prismatic and contoured parts. It is used primarily for quality-control inspection, process control, and reverse engineering; i.e., creating CAD drawings from prototypes and models.

The mapper uses proprietary structured laser-light scanning technology along with optical triangulation and other 3D image-processing techniques. The resulting geometric map is then translated into either IGES or PDES (CAD languages) format. When used as a quality-control tool, actual part dimensions are evaluated against design dimensions, and out-of-tolerance conditions reported for repair and upstream process control.

Noncontact measurement allows mapping of soft and pliable parts, rough-cast parts, and complex shapes. Three models address a wide range of part sizes up to 5 ft X 10 ft x 20 ft.

Robotic Vision Systems Inc, 425 Rabro Dr East, Hauppauge, NY 11788 or circle 469. 1903

Trilateration calibration

The LTS-1000 laser trilateration system is a fast and accurate method for machine-tool calibration and error mapping. It uses standard interferometers to perform 3D volumetric performance measurement of machine tools both statically and dynamically. It can be used for measurement, inspection, calibration, in-process quality control, 3D error mapping, and creation of a database error log.

Used as a portable coordinate measuring machine, trilateration can inspect large-scale molds, jigs, fixtures, assembly tools, and critical parts. Calibration of CMMs, machine tools, robots, or multiaxis equipment can be performed with no down time. Or the laser system can be an integral part of such machines to enhance their performance via real-time, closed-loop feedback. It measures up to six degrees of freedom (X,Y,Z axes, plus roll, pitch, and yaw) to correct machine movement and give robots CMM accuracy through their ranges of motion.

A helium-neon laser beam is split and delivered through four (three or more required) two-axis trackers and focused onto a spherical retro-reflector mounted on the object being measured and tracked automatically by a quadrant-photodetector-controlled servo. Each interferometer calculates the radial distance to the retro-reflector from the pivotal axes of the tracker. Three or more length measurements can locate points in three-dimensional space with micron accuracy.

LK Tool USA Inc, 1625 West University Dr, Tempe, AZ 85281 or circle 470

Machine calibration

The HP 5528A laser measurement system is used as a primary standard to measure parameters that affect machine-tool accuracy and repeatability, such as pitch, yaw, horizontal and vertical straightness, as well as linear displacement. It assures that a new machine is in spec at startup, and by periodic checks, remains in spec throughout production.

Measurements can be made without lengthy interruptions in the production schedule - taking hours instead of days. New users can quickly learn to use the system effectively. With these periodic measurements, users can improve productivity, optimize their machine-tool investment, and achieve improved part quality and work flow and reduced maintenance costs and downtime.

Federal Products Corp, 1144 Eddy St, Dept 8947, Providence, RI 02940 or circle 472. 1903

Bore parallelism

A new system for gear-case bore parallelism measurement has been developed, including application-specific software. It uses the L-731 sweep tooling laser and three targets that check alignment of a four-bore gear unit in less than 1 hr.

The portable system uses the sweep tooling laser as the primary reference to be positioned in front of each bore to be measured. After the laser is "bucked in", a parallel condition is achieved by three targets forming an L-shaped setup. The computer software measures the three plane targets and computes the width of parallel condition for each of the bores relative to the first bore reference point. The operator enters the X-Y dimensions between each bore center and measurement accuracy of 0.0002"/ft can be achieved.

Other alignments systems provide inspection and alignment of machine tools, large equipment, and parts for a variety of industries. The basic system components are the laser unit, a target, and a readout device. The system determines misalignment using the laser beam as a refernce and provides adjustment information for fast corrective action.

Hamar Laser Instruments Inc, 1047 Danbury Rd, Wilton, CT 06897 or circle 473. 1903

Ball-screw measurement

The time it takes to calibrate thread-lead over the length of a ball screw can be reduced by a factor of five through the use of this laser measuring machine. This was the case at American Ball Screw, a manufacturer of ball screws for industrial machinery and aircraft landing gear, flaps, and ailerons. Their machine accomodates ball screws from 1/2" to 6" dia, and lengths to 18 ft.

Previously, lead verification of an 8-ft-long, 2"-dia screw took 2.5 hr. With the new measuring machine, the same screw is now checked in 30 min. Repeatable accuracies are within [ + - ] 0.000 010" with a resolution of 0.000 001". After placing the ball screw in the machine, the operator positions a material sensor that automatically compensates for ambient conditions. The machine is then zeroed, and the ball screw checked at specified increments. Base of the device is a granite surface plate 150" long, 26" wide, and 30" high. A stable Meehanite casting floats on air bearings the length of the checking area to provide frictionless motion.

A staking-type probe is inserted into the thread form and positions the laser reflection mirror. Data is triggered manually into the computer by a remote input device carried by the operator. The system includes a Hewlett-Packard 5528C laser head, interferometer, reflector, and HP85 computer.

AA Gage, 350 Fair St, Ferndale, MI 48220 or circle 474. 1903

Real-time positioning

CMS-2000 laser coordinate measuring system combines laser interferometry with one or more servo-controlled trackers and target retro-reflectors to provide real-time position data at a 100-Hz rate. Applications include assembly and inspection of antennas, aircraft, propellers, and tooling and gages; and the calibration and error mapping of CMMs, machine tools, robots, and antennas.

Tracking is automatic without manual sighting or photogrammetry, tracking the retro-reflector at 2-g acceleration and velocities to 20 fps. No special lighting is required. The unit is self calibrating and compact, mounting on portable tooling stands. Software is menu-driven.

Chesapeake Laser Systems Inc, 4473 Forbes Blvd, Lanham, MD 20706 or circle 475. 1903

Submicron measurements

Laserscale laser-based system uses holographic techniques to measure linear motion of a positioning device with a resolution of 0.01 micron (0.000 000 5"). An ultra-fine array of lines are photolithographically deposited on a glass scale to create a three-dimensional grid. As a split beam of light passes through the moving glass, it detects the phase shift of the grid as motion of a hologram. The holographic effect provides a highly reliable signal, even with variations in the wavelength of the light source, since the two beams are constant in relation to each other.

This approach provides stable measurement and repeatability in unqualified environments. By enclosing the semiconductor laser in a special housing, the scale is far more tolerant of manufacturing-floor conditions than the traditional open-beam laser. Scale is available without a housing for custom integration with user equipment. The system includes probe units, fixtures, and a digital display with joystick control for zeroing, presetting, and recall. Applications include the machining of magnetic heads and optical components, and precision laboratory measurements and quality-assurance inspections.

Sony Magnescale America Inc, 37 Bristol Lane, Orange, CA 92665 or circle 476. 1903

Noncontact measurement

Optocator noncontact system uses laser-beam triangulation for rapid and precise measurement of dimensions, surface profiles, thickness, level, and vibration of nearly any material, regardless of its surface texture, temperature, density, or color. For example, the level of molten iron or the thickness of extruded rubber can be measured with this approach.

Production applications have included high-speed measuring of rubber and plastic extruded profiles; gaging thickness, width, and flatness of hot and/or cold-rolled metals; measuring bar, beam, or tube diameters; checking waviness, twist, and symmetry of rails; and profiling turbine blades. Other uses include optimizing pouring levels in metal casting and robotic inspection of stamped, cast, or forged parts.

Unlike other noncontact systems, the Opticator does not have to be close to the surface being measured, and measurement is accomplished with no moving parts: no mirrors, prisms, video imaging devices, or radiation sources. Packaged systems range from a simple gage probe and signal processor outputting to an indicator to highly sophisticated systems and seam finders for arc welding.

Selective Electronic Inc (Selcom), P O Box 250, Valdese, NC 28690 or circle 477. 1903

Dimensional measurement

Connected with a Laser Mike laser scanner, the new 1000 Series processors cover applications from simple SPC data acquisition to full closed-loop process control. Adding a second scanner can provide dual-axis measurement and process control. Multiple setup libraries are available to enable operators to easily adjust parameters. The 1000 Series can interface with host computers, other data-gathering devices, or older LaserMike scanners.

LaserMike Inc, 6060 Executive Blvd, Dayton, OH 45424 or circle 478. 1903

Other products:

Shop-floor CMM

Universal Measuring System (UMS) is a shop-hardened coordinate measuring machine that takes parts measuring out of the QC lab to the production floor. All ways and sensitive components are protected to withstand dust, dirt, and contaminants, and the 4-ton granite slab absorbs thermal shock to minimize dimensional effects of rapid temperature change. Additional compensation for slow change is provided in the software. Top speed is 17 ips, measuring volume is 47" x 24" x 31", and accuracy within that volume is between 0.0004" and 0.0006". Horizontal Y axis provides access to the work area and is reversible to access transfer lines or AGVs.

Federal Products Corp, 1144 Eddy St, Providence, RI 02940 or circle 479. 1903

Gaging options

Family of plug-in optional modules for the XL-2000 digital gage amplifier provide new data-output formats and control features. One actuates internal relay contacts or logic outputs based on tolerance-limit settings to control sorting or automation equipment. Another allows external programmable controllers to select or sequence any gage function using contact closures or logic signals. The base unit has dual LVDT-gage inputs that operate individually or in A+B/A-B modes and offer 0.000 01" (0.001 mm) resolution.

Brunswick Instrument, Div of X-L Engineering Corp, 6150 W Mulford St, Niles, IL 60648 or circle 481. 1903

Tool-setting gage

Precision tool-setting gage for boring mills, milling machines, drill machines, and NC machining systems is hardened throughout and supplied with a 0.0001" test indicator. Zero setting is quick and the large axial range in the feeler head prevents damage to the tool. Reference height is 50 mm and repeatability is 0.000 04" (0.001mm).

Fred V Fowler Co Inc, Dept L, 66 Rowe St, P O Box 299, Newton, MA 02166 or circle 482. 1903

Flaw detector

Sonic 136 portable flaw detector with microprocessor controls enables all instrument functions to be accessed through a primary function-key parameter display. Secondary arrows move the cursor up and down to the selected function, and a "Smart" knob changes function values. The unit also has a tradtional CRT with analog RF display, program storage capabilities, waveform and instrument settings storage, and RS232 computer link.

Staveley Instruments Inc, 421 N Quay St, Kennewick, WA 99336 or circle 486. 1903

Surface and form

Modular line of surface texture and form measuring systems allow updating when measurement requirements change. Modules include 50-mm and 120-mm traverse units, a selection of stylus arms, motorized columns, accessories, and data-processing options. Gaging via laser and inductive methods permits analysis of both form and surface texture at high resolution with one measurement. Dynamic range of the basic inductive pickup is 1.8 mm, and 20 mm for a contour pickup.

Rank Taylor Hobson Inc, 411 E Jarvis Ave, Des Plaines, IL 60018 or circle 488. 1903

Video measuring system

The Turbo 300 addition to the Q-See line of noncontact video measuring systems includes a dual-magnification optical system, three axes of precision coordiante movement, six individual iluminators, and a number of software options. The 16" x 12" worktable can handle loads to 55 lb. High-speed closed-loop DC servos drive all axes. Measurement speeds are 157 mm/sec, X and Y, and 102 mm/sec, Z.

Optical Gaging Products Inc, 850 Hudson Ave, Rochester, NY 14621 or circle 496. 1903

Free quality software

A formal system for statistically assessing variation in measuring devices (repeatability and reproducibility or R&R) is essential for a quality program. An R&R manual and software program was developed for LTV Steel by IQS Inc, Cleveland, OH. It provides suggestions for implementing and performing R&R calibration studies and is offered free of charge by LTV to its customers, suppliers, and outside processors. For more information, contact Larry Barrentine, LTV Steel, 25 W Prospect Ave, Cleveland, OH 44115 or call (216) 622-5932.

Universal measuring

Diamar No. 829 universal measuring instrument uses a variety of accessories to measure IDs, ODs, recesses, collars, grooves, eccentricity, concentricity, and right-angle relationships of ODs to work faces. A precision ball bushing in the moveable arm holder eliminates play and friction. There are two fixed measuring-arm holders, one for coarse setting, the other centers the work. Mounting table is inclinable for aligning the work, and measuring pressure is adjustable for delicate work.

Mahr Gage Co Inc, 274 Lafayette St, New York, NY 10012 or circle 490. 1903

Gear test fixture

VGF 1 gear fixture for the Microdur hardness testing product line permits quick measurement of hardness of the flank and root area of gears without destructive sectioning. It combines ultrasonic contact impedance measurement with micro-hardness testing. The hardness indentation is very shallow-approximately 0.0002" deep for a case carburized gear with surface hardness of 60 Rc-and requires no corrective machining or grinding. The fixture accommodates gears from 2" to 12" OD. Hardness tests can be performed at rates of six to ten per minute.

Krautkramer Branson, P O Box 350, Lewistown, PA 17044 or circle 494. 1903
COPYRIGHT 1989 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1989 Gale, Cengage Learning. All rights reserved.

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Publication:Tooling & Production
Article Type:product announcement
Date:Nov 1, 1989
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