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Simulation optimizes gage cost/life.

Computer simulation of manufacturing operations can be used to optimize machining, fabrication, and inspection prior to actual building and assembling of parts. Craft Line, a design services company specializing in automotive manufacturing equipment, has used computer simulation to help the auto industry avoid their traditional time-consuming and expensive build-test-fix" cycle. Of particular interest was a simulation involving gaging fixtures. The widely used auto-industry standard repeatability and reproducibility (R&R) study used to test gaging fixtures measures the ability of a fixture to repeatably locate a component in its holding nest after manual insertion. It consists of placing the part in the fixture a given number of times, measuring its location each time, and expressing the variance as a percentage of part tolerance. Raising the roof

In this case, the fixture inspects truck-roof panels whose tolerances must be held within I mm. Fifteen datum points (rests) are used to locate the 10-ft x 5-ft panel. Twelve are up-down rests spaced throughout the panel, two are cross-car datums, and one a fore-aft datum. Most use clamps. Ideally, the panel would touch all rests, but in practice, a small gap appears at each rest.

We have been building these fixtures since the 1950s. The traditional approach is to build the fixture by following as closely as possible the design of proven fixtures, and then test it to see if it works. Invariably, it doesn't work the first time, and must be reworked, usually by repositioning the rests until acceptable results are achieved. Getting optimum results is often expensive in terms of both re-work and re-testing time required.

This case was different because, prior to building the gage, we built a model of the concept using the VSA variation simulation analysis program from Applied Computer Solutions, St Clair Shores, MI. VSA simulates the manufacture and assembly of a product to provide an accurate indication of actual production variation due to design and assembly tolerances. The model includes a 3-D model of each component, variation of critical surfaces based on specified tolerances, and a representation of each assembly operation. The software program puts the assembly together, one step at a time, in the proper processing sequence. The program then simulates a production run of the final assembly and provides statistical analysis of the results.

Here, the operation of placing the part onto the fixture was treated as one assembly operation. Lab tests by the customer measured the location variation of a single rest. This provided information to the model on how well the gage

could locate the panel in position. The part itself was modeled as a rigid body, even though it does have some flex. Although this approximation prevents the results from being exact, they still reflect relative effectiveness when comparing different gage deSigns.

Using a program feature for customizing output, we produced printouts in standard R&R proof-test format. The gap at each datum location was expressed in terms of percentage of total allowable tolerance. The analysis simulated five operators placing ten parts onto the fixture. The analysis showed that the fixture would frequently produce a gap of 1.5 mm at several datum points, an unacceptably high tolerance.

Studying the results helped us understand exactly what was going wrong. Most of the variation was on from each bin, and "builds" 1000 final assemblies.

The results of the simulation are then displayed in statistical form, including the predicted location or relationship of critical points on an assembly after final build. Based on a large sample size, the predicted percentage of high, low, and out-of tolerance dimensions can be obtained for each output variable defined in the math model. Output variables are not only locations on given surface, they also can be relationships such as gaps, interferences or any other mathematically defined variable. VSA simulations have predicted compression-ratio variation, cracking-pressure variation tion, friction, and spring tension.

The statistical results also provide a percent contribution analysis that predicts what percent certain input variables contribute to a given output variable. This provides the engineer with a tool to determine the critical cal tolerances and relationships in the assembly. Design emphasis can be placed on changing the largest contributing factors (or relaxing the smallest contributing tolerances) to reduce cost.

The software can be used to model very complex, 3-D assemblies with over 2000 input variables and several hundred components. It can also simulate the build of fairly simple assemblies where the objective is to optimize tolerances for mass production. Generally, it can be applied to any product build or process where the interaction of numerous variables (dimensional or functional) effect final design. Featured this monthSoftware products: Deployment software QFD Designer is a software program that permits the generation of quality charts or charts for other phases of quality function deployment without the need for extensive computer instruction or documentation. Because the program works the way people do, it allows you to work directly on the chart.

American Supplier Institute Inc, Six Parklane Blvd, Suite 411, Dearborn, MI 48126 or circle 417. SPC enhancements Custom/QC Version 3 SPC software for IBM PCs and compatibles now incorporates greater speed, new custom configurations, enhanced control charts, and a wider range of special data analysis functions. An advanced user interface uses color pop-up menus to guide the user through data collection, analysis, and reporting. Expanded output options include subgroup markets, connecting lines, labeling, scaling, number of digits, lettering size, grid appearance, and colors. Special handling includes direct input of ASCII text files from spreadsheets, data bases, or word processors, plus optional automatic data capture from a serial gage.

Stochos Inc, 14 N College St, Schenectady, NY 12305 or circle 421. 1903 Portable data collector GageTalker III Hand Held is a portable data collection device used for SPC and is compatible with a companion fixed workstation. By interfacing directly with electronic gages, it provides real-time process-control information to machine operators. It has a 20-line x 21 character screen, and collects and displays attribute data, variable data, and short-production-run data in a unit that weighs less than 3 lb.

GageTalker Corp, a subsidiary of Brown & Sharpe, Bellevue, WA or circle 430.

1903 QC computer for SPC Model 72OCQ computer features 32K RAM, a full-size keyboard, liquid-crystal screen with 20 x 4 character display, a built-in microcassette that runs SPC or user-written programs, and a microprinter that prints 2 1/4 "charts, graphs, or text. A five-port interface accepts sequential measurements from up to five electronic gages. Battery operated, it runs up to 50 hr per charge. An optional 411 printer and hand-held data collector are available.

L S Starrett Co, 121 Crescent St, Athol, MA 01331-1915 or circle 431.

1903 Statistics test A 20-question pre-test is used to confirm an individual's working knowledge of statistical principles and their application in SPC. It is designed to uncover areas of weakness for later corrective training. The six-page test is part of "No Sweat Statistics", a nonacademic video-based training program.

Excel Training Inc, 19 Alpha Park, Cleveland, OH 44143-2202 or circle 449. 1903 Quality management modules QMS Programs/370 is an integrated set of quality modules for implementing total quality management. The system tracks the quality of materials as they flow through the manufacturing system much as MRP 11 systems track the quantities of these same materials. The SQC starter group of modules addresses incoming inspection, SPC, defect analysis, quality audits, finished goods release, field failures, customer complaints, and environmental monitoring. Prices for the SQC starter group begin at $27,000 for use on the IBM 9370 Model 20. Developed by John A Keane and Associates, Princeton, NJ, it is being marketed by IBM. Contact your local IBM representative or circle 436. 1903 Inspection systems Cadarcheck electronic inspection system for shop-floor batch sampling, auditing, and SPC analysis can measure up to 16 dimensional features on one component. Up to eight column digital or 16 analog displays and charts can be linked to a wide variety of measuring devices. Cadarlog is a hand held, menudriven, and battery operated tool for remote data collection and SPC analysis.

Kaufmann Instrument Laboratory, 1125 Dixwell Ave, Hamden, CT 06514 or circle 425. 1903 SPC video course A 49-min video training course on statistical process control is offered, developed by the Greater Cincinnati Industrial Training Corp. It introduces SPC, describes its use in quality control, and provides extensive instruction in fundamental principles. Course demonstrates the uses, patterns, and applications of X-bar and R charts. Cost is $495, and it is available in various video formats as well as video laser disk.

Metcut Research Associates Inc, 11240 Cornell Park Dr, Cincinnati, OH 45242-1812 or circle 6. Machinist-oriented software M-STAT software package provides easy measurement input, statistical process control, and data transfer. It is designed with the machinist in mind, incorporating many features that make it simple to use and understand. These include singlestroke entry for all commands particularly important where operators are required to wear gloves), extensive error trapping to prevent program crashes, built-in warnings for critical key strokes, and a menu flow diagram to aid learning. It runs on IBM or compatible computers.

Mitutoyo Measuring Instruments, 18 Essex Rd, Paramus, NJ 07652 or circle 444. Color-plotting SPC software Upgraded color-formulation and QC software now supports HP-GL compatible plotters and more graphic-display terminals and printers for greater detail than black-and-white printers. With the appropriate six- or eight-pen plotter, the software can produce hardcopy plots or overhead transparencies from spectral or colorimetric data. Capabilities include pass/fail, colorant strength, color difference, and shade sorting. Match Pak formulation software adds color-formula prediction, batch correction, and formula inventory and search capabilities.

Nuiton Roy, Diano Color Products Group, 820 Linden chester, NY 14625 or circle 457 Radio-linked SPC Telemeasure is a 1 1/8" x 1 1/8" x 1/2" transmitter that sends measurements from a measuring tool-calipers, micrometers, indicators, etc-to a computer for quality analysis and reporting, eliminating restrictive wire connections of conventional SPC systems. Operators can be anywhere on the shop floor within a 33-ft radius of the computer. A single receiver can process data from up to 100 tools.

Nitto Kohki USA Inc, 808-C North Central Ave, P 0 Box 129, Wood Dale, IL 60191 or circle 491. SPC package Operator friendly SPC software package runs on either standalone or networked IBM PC or compatible systems. Sublot mode organizes measurement data in small, fixed quantity groups for regularly sampled, on-going process control work. Bulk mode allows larger samples of varying quantities to be handled for machine-capability testing and receiving inspections. Because the system charts and histograms are available on screen, a printer is not required to retrieve or view results.

Brunswick Instruments, 6150 W Mulford St, Niles, IL 60648 or circle 428. 1903 SQC data station Gage monitor SQC data-station software package links electronic gages to the Quality Analyst for real-time SQC charts on demand. it runs on IBM PC, PS/2, and compatible computers. It can be set for keyboard entry or to take data directly from individual gages, multiple gages, or multiplexers. Measurements are date and time stamped, and repeated identifiers or batch numbers can be automatically entered.

Northwest Analytical Inc, 520 NW Davis, Portland, OR 97209 or circle 429. 1903 SPC and gage management Latest versions of QA/S SPC and GageTrol software have added realtime control and runs testing to help operators identify out-of-control conditions. Because QA/S is network aware, LAN users can share SPC data throughout the plant. Any type of data distribution can be analyzed, including data from non-normal processes. GageTrol now has enhanced gage calibration management and reliability/repeatability (R&R) features, including the GR and R calculations required by Ford and GM, and expanded gage-tracking capabilities.

Paul Hertzier & Co Inc, P 0 Box 578, Goshen, IN 46526 or circle 476.

1903 Pocket SPC analyzer DataNet 3000 handheld data collection PC computer has the computing power of a high-performance XT computer in a pocket-size unit. It performs multi-part, multi-process SPC on machined, stamped, ground, formed, or cast parts. Direct gage connection from electronic digital, analog, or LVDT gages gives quick pushbutton data transmission into the data collector. Real-time SPC charts are displayed lighted LCD screen of 8 lines x 26 characters or separate full-size monitor.

Ecco Systems Inc, 1300 W Hamlin Rd, P 0 Box 090159, Rochester Hills, MI 48309 or circle 472.

1903 SPC management TurboSPC 3.0 software manages an SPC program using pull-down menus and pop-up windows for ease of learning and use. A mouse is optional. It receives data collected manually or by data collectors for automatic acquisition and easy-touse feedback to the machine operator. it enables reviewing control charts and capability performance, performing additional statistical analysis or "what if" investigations, sorting data by machine or shift, generating management reports, storing archival data, and managing data-collection setups. DataMyte Corp, 14960 Industrial Rd, Minnetonka, MN 55345 or circle 470. 1903 Dataloging software Logger software package directly integrates datalogger hardware and PCs for computer-based datalogging. It combines the mass storage and data-analysis power of a PC with the measuring capability and ease-of-use of a datalogger. It is for use with the Beckman Model 245 and 278 dataloggers and an IBM PC, PC-XT, or PC-AT compatible. It collects analog sensor data through the PC serial port after conditioning and transmittal from the datalogger. Once received, the data can be displayed in groups of 100 channels, stored in memory, and recalled for analysis.

Beckman Industrial, Instrumentation Products Div, 550 S Harbor Blvd, La Habra, CA 90631 or circle 463. 1903 Quality management system RQM, Revision 3. 1, is a management system for real-time SQC/SPC monitoring of factory-floor processes. It provides automated data analysis and interpretation, alarming only on detected changes in the process. Factory-floor personnel can concentrate on solving problems rather than searching for them. Status screens allow users to view current state of their processes as well as investigate alarm conditions. Available for use on HP9000, HP1000, DEC VAX, and Motorola X computers. Automated Technology Associates, 9000 Keystone Crossing, Indianapolis, IN 46240 or circle 4".

1903 Other products Laser sensor The addition of a laser sensor to a video-based vision system enables critical measurements of surface flatness or contour to be performed in less time (on the fly) and more accurate height measurement of micro features found in the electronics industry. Two types are offered: a back-scatter laser for scanning surfaces at 4"/sec with a 50-micron 0-002') spot and measuring range of +/- 3 mm (0. 12"), and a coaxial laser with a 2-micron spot (0.000 080") and measuring range of .012" for measuring extremely small features.

View Engineering, 1650 N Voyager Ave, Simi Valley, CA 93063 or circle 540. 1903 Robotic CMM Sirio high through-put robotic CMM brings this technology directly to the production floor, next to the manufacturing Process, fOr standalone, cell, and FMS applications. Machine-tool structure provides mechanical stiffness for rapid acceleration and positioning velocities. It is totally enclosed for thermal uniformity and protection from dirt, dust, chips, and coolant. Volumetric accuracy is maintained over a shop-floor temperature range of 60 to 104 F through a proprietary modeling system and index-table calibration process. Quindos measurement software, hosted on a DEC VAX computer, provides part measurement, real-time statistics, menu programming, error-condition control, graphics, and remote-host operation.

Wild Leitz USA Inc, 24 Link Dr, Rockleigh, NJ 07647 or circle 492.

1903 Large-workpiece CMM Mauser/Zeiss MMZ bridge-type coordinate measuring system is for large workpieces such as automotive engine blocks, transmissions, and jet-engine housings. Main guideway Y axis) is located at the level of the main working stage for optimum drive characteristics-acceleration of 40"/sec/sec and traverse speed of 1011/sec. Measuring accuracy IS .00021, including probing. Three measuring ranges offered are: 48" x 48 " x 4011, 48 x 80 " x 40 ", and 48" x 961, x 40". Because its weight is half that of previous models, it can be mounted on an antivibration system and does not require a foundation.

IMT Div, Carl Zeiss Inc, One Zeiss Dr, Thornwood, NY 10594 or circle 527. 1903 Coating thickness Digi-Derm gages are compact ultrasonic instruments for nondestructive measurement of coating thickness. One model is for nonmagnetic coatings on magnetic materials, the other for nonconductive coatings on nonmagnetic material. A large LCD readout presents measurements in inch or metric units with a resolution of 0.000 05 /O.001 mm. Gages operate on AC power or rechargeable batteries with 80 hr continuous use between charging.

Mitutoyo Measuring Instruments, 18 Essex Rd, Paramus, NJ 07652 or circle 498.

1903 Thickness module USK7 DTM microprocessor-controlled digital display and output module upgrades the USK7 flaw detector for erosion/corrosion measurement, weld inspection, flaw location, and through-coating thickness gaging. Thickness readings are shown directly on a four-digit LCD with 0.001 " resolution. Two modes and a range of probes cover many inspection applications, including through-coating measurement with the multi-echo mode.

Krautkramer Branson, 50 Industrial Park Rd, Lewistown, PA 1704 or circle 381.

1903 Slim readouts Futaba/Pulscale SD digital linear readout features slim, compact design in a one-piece extrusion. A 15V power source, square-wave signaling at the readerhead, and individually shielded twisted wire pairs contribute to exceptional noise immunity. Travel lengths range from 75 mm to 1200 mm (2.9 to 47.2 19 in 19 standard lengths. Scale resolution is 10 micrometers 0.00041).

Schweda International, 2400 Milwaukee St, Delafield, WI 53018 or circle 493.

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Author:Morgan, Earl
Publication:Tooling & Production
Date:Apr 1, 1990
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