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PC-based DNC takes off at Convair.

How would you like to get a new state-of-the-art computer system for about what your present annual computer maintenance costs are running? A system that is faster, more flexible, easier to repair, and less costly to upgrade? That is exactly what General Dynamic's Convair Div, San Diego, did in June 1991. General replaced its minicomputer-based proprietary system, originally installed in 1979, and costing $200,000 a year to maintain, with a Greco PC-based DNC system at a cost of $250,000, and a yearly maintenance fee of $40,000.

Error-free data is vital at Convair because of the high-precision required for aircraft and missile components produced at the plant. It's not unusual for the aerospace supplier to be cutting three $10,000 parts at the same time. Parts are sometimes 60-ft long with dimensional tolerances of only [+ or -]0.005" from end-to-end. The largest machines include seven vertical-spindle gantry mills. Two gantries share a 70-ft bed, two share a second 70-ft bed, and the remaining three share a 110-ft bed. One of the longest parts ever machined, the keellongeron for the space shuttle, was produced on one of Convair's large gantry mills.

DNC then

The original DNC system, installed by a computer manufacturer for Convair in 1979, cost several million dollars. It was based on two Gould minicomputers located in a 20 ft x 40 ft environmentally controlled computer room. The second minicomputer was a backup. Each had 512K of RAM and was connected through individual cables with each of the machines on the shop floor.

Machine-control manufacturers--including White-Sundstrand, Allen-Bradley, and Cincinnati Milacron--worked with the DNC vendor to modify its control hardware and software specifically to accept serial input directly from the minicomputers. The modified hardware and software allowed DNC menus and other screens to be displayed directly on the machine control CRTs rather than on separate DNC displays. However, the control system modifications required giving up memory capacity in many of the controls. As a result, many machines could only receive data on a block-by-block basis.

Part programmers liked the DNC system mainly because they could modify programs and download them to the shop in an hour compared to a day or two without DNC. Some programs required as much as 10,000 ft of tape and up to 15 separate tapes. It sometimes took two days to punch out new tapes and have them delivered to the shop. DNC also allowed much better control over part program changes.

Minicomputer reliability was not a problem, but there were downtime problems with the tape drives and the large disk drives attached to the minicomputers. It became difficult to find replacement parts or even to locate someone to perform maintenance when the computers became obsolete. If the minicomputers were down, most machines couldn't keep running longer than it took to process a single block of data. In one instance, the entire computer system was down for three days. The only backup was tape, and it took 23 hours to get the first tapes delivered to the shop.

DNC now

One of the more recent trends in manufacturing has been the shift from proprietary computers, software, and peripherals to an open architecture based on PC-compatible products. PC-based products have only begun to appear in quantity and at attractive prices within the past few years. This trend, however, is gaining momentum and providing many new opportunities to reduce costs and increase productivity through new software, networking, and systems integration technology.

To take advantage of these recent trends, Convair collaborated with Computer Science Corp, the service contractor to General Dynamics for all computer and networking services. The plan was to install a new DNC system that would mimic the existing system while delivering major improvements in DNC maintenance costs and shop productivity. Bid specifications required that the new system adhere to the following requirements:

1. Use PC-based DNC computers with DOS software.

2. Transfer part programs reliably to the DNC computers from an IBM mainframe in Convair's Kearny Mesa facility 10 miles away where the part programs are stored.

3. Download part programs to the machines more reliably and much faster than the 15 min it was currently taking.

4. Keep existing operator screen menus intact, in order to minimize operator training time.

5. Provide precise document configuration control to prevent unauthorized access to files and to insure the accuracy of part programs and their distribution from the DNC computers to the shop.

6. Work with binary machine control language as well as with character-based part program languages.

7. Connect all controls (even older controls with parallel interfaces) into the DNC network.

8. Provide the equivalent of at least 2000 feet of tape storage at each machine.

The winning bidder was Greco Systems. The company was able to quickly interface its system with 43 NC machine tools, retain all operator DNC menus, and meet all other specifications. As a result, Convair did not have to change any manufacturing methods or procedures, resulting in a very significant savings on installation, training, and downtime costs.

The Greco DNC system provides high speed (1 Mbaud) local area communications for up to 64 machine tools and is easily expandable. it includes two dual (one backup) IBM-compatible 80386 PCs, each with two 320 MB SCSI drives, 14" VGA color monitors, 4 MB RAM, two floppy disk drives, SDLC high speed communications to the shop, and a remote job entry link to the CSC Dada Center in the Kearny Mesa facility.

The active file server is connected to one of nine network interface units (NIUs) wired in series in a bus network configuration. Part program data is sent to the NIUs using RS-422 standard protocol for data transmission. This protocol allows error-free serial data transmission at 1 Mbaud using inexpensive shielded cable over distances up to 4000 ft.

The proprietary DNC interface at each machine was replaced with a Greco mass-memory CNC/DNC interface that stores the equivalent of 10,000 ft of paper tape on floppy disk. This shop-hardened rack-mounted device, located in the compartment formerly reserved for the tape reader, has a serial port for data input. It converts serial data from the network to parallel or serial data for input to the NC/CNC machine.

Once the CNC/DNC interface receives the part program, the machine tool can operate from memory regardless of problems occurring on the network. This is a significant improvement over the older system. In addition, part programs can be written to a DOS-compatible floppy disk and manually loaded into the CNC/DNC interface if the network is down for an extended period.

The DNC file servers are easily replaceable with similar 386 computers located throughout the Convair facility. They can be upgraded to larger, more powerful file servers such as an 80486 computer at any time using low cost off-the-shelf hardware. New machines can be added to the network for $4000, including the cost of cable, a CNC/DNC interface, and a Wyse CRT--about one-fourth the cost of adding a machine to the old system.

About ten part programs are downloaded to the machines each day. Programs that used to take as long as 5 min to download are now do less than a minute. In addition, at the start of a new shift, operators usually have the data they need stored on a floppy disk right at the machine. There is no need to download again from the file server.

When a new part program is needed, an operator uses the machine's CRT terminal to access a menu from the file server. If the program exists on the file server, the operator can immediately download it. If the program isn't on the server, the operator can order it from the remote IBM Panvalet library, which will download it via modem to the server. Today, Convair's system operates virtually unattended. It requires minimal manual intervention to keep it running. A small amount is budgeted yearly for routine maintenance such as changing CNC/DNC interface fan filters and regularly changing out diskettes.

Greco Systems, El Cajon, CA, circle 280.

NC in Windows

Solution ware Corp has introduced Geopath for Windows, an NC programming system designed specifically to run under Windows. Geopath is said to fully utilize Windows' advantages such as extended memory, so that the user can load larger part programs and CAD files.

The software allows instant access to CAD files and can read IGES surfaces, DXF, and other popular CAD files. Features include Z depth from CAD models, 3D splines, and a full set of 3D surfaces, including parametric cubic surfaces, B-spline, ruled or swept, four-comer patch, surface of revolution, and 3D project.

Solutionware Corp, San Jose, CA, circle 261.

Windowing in on SPC

QI Analyst from SPSS is a low-cost Windows-based software package providing a full set of 23 SPC charts, capability statistics, Shewhart control tests, and reports.

Running under Microsoft Windows, QI Analyst makes collecting and analyzing new data easy. Users can enter data directly into charts via a prompt mode or import data from other sources. The points are quickly tested with a variety of statistical tests, and the color-coded chart is updated immediately. A special spreadsheet-like data editor is designed for simple batch entry, definition and editing of data, viewing of data and related assignable causes, corrective actions, and notes.

Imported data can be entered directly from RS-232-equipped gages, or from popular software such as dBASE, Excel, Lotus, and SPSS system files without translation.

The shrinkwrapped package lists for $695 but carries a special introductory price of $395 available through September 30, 1993, which includes a bonus of a free gage R&R program. The title page from a competing product will get you an additional $50 discount.

SPSS Inc, Chiago, IL, circle 266.

NC for DOS

Surfcam, a full-featured computer-aided manufacturing (CAM) software package running under MS-DOS is designed to meet all the NC programming needs for 2D and 3D wireframe design; surface modeling; and 2-, 3-, 4-, and 5-axis machining for mills, lathes, wire EDMs, lasers, plasma, and waterjets.

Version 4.0 features over 200 new and improved features, most of which resulted from customer suggestions and feedback. The new version adds numerous 2D and 3D wireframe design, sculptured surface modeling, CAD data translation, and NC machining improvements to Surfcam.

Several industry specific CAD translators have been added, such as: Chrysler Standard Format (CSF); General Motors' Data Exchange Standard (DES); Ford Standard Tape (FST); VDA-FS German Automotive; SPAC's French Aerospace, NCAL/NCAD; Northrop Surface; and FastSURF ASCII. Existing IGES, DXF, and CADL translators have been improved with Surfcam Version 4.0.

Over half of the 200 improvements are specific to NC, with improvements across all 2-, 3-, 4-, and 5-axis machining operations.

Surfware Inc, San Fernando, CA, circle 260.

Putting DNC on a network

Shopnet 2000 DNC system combines a user-friendly DNC software package with a line of shop-hardened workstations. Using a 10 Mbit Ethernet/Novell LAN with an open architecture configuration, the Shopnet 2000 system can be easily interfaced to existing in-house systems and is available in Standard and Database versions.

The Standard DNC system (for small to medium-sized shops) is designed to store, manage, and distribute part programs and other support documentation where and when required. Built-in DNC features include a windows-like user interface, file management, file upload/download, and machine work list entry. The station's interfacing capabilities allow both serial and parallel behind-the-reader applications, without the use of customized hardware.

The Database version (for larger shops) provides all of the standard-version features, plus job folders, expanded work lists, job tracking, status monitoring, and data collection. With these facilities, fists can be developed, data analyzed, and reports produced for management evaluation.

Complementing the software, Numeridex CAM is offering 286- and 386-based workstations built into shop-hardened housings. The workstations are equipped with an LCD display and an 84-key standard ASCII keyboard. A large 25-line by 80-character display supports full gray scale VGA graphics capabilities.

Automation Intelligence, Maitland, FL, circle 264.

"Take me to your doctor"

RobotPro is a PC-based diagnostic expert system designed to diagnosis robot problems. Running under Microsoft Windows, the program guides the user through robot diagnosis, repair, and restart procedures with photos, drawings, schematics, text, and other display methods. Packaged RobotPro solutions are tailored to each Motoman robot model.

Three key components of the program are: the consultation window, where the user enters a menu-driven question and answer session to pinpoint his/her individual needs; the information window, where important graphical information is displayed to assist the user in identifying needed information, or to provide visual instruction on required repair procedures; and the placeholder window, which keeps a reference of where the user is in his/her diagnostic or maintenance procedure session, as well as providing a mechanism to back up or jump forward in the menu.

Motoman Inc, West Carrollton, OH, circle 262.

Link CNC to PC

Greco Systems CNC MiniLink software provides shop-floor users with the ability to connect existing CNC mini-files or CNC stations to a personal computer and send files directly to the connected machine tools.

Users can view directories located on the CNC station or mini-file directly at the PC. Directories on the PC can be viewed at the CNC station while connected to the machine tool control. CAD/CAM operators can send programs via RS-232 directly to the machine tool control without having to physically walk back and forth between the CAD/CAM system and the machine tool.

Greco Systems, El Cajon, CA, circle 263.

32-bit control for 5X power

Mazak's M-32 and T-32 CNCs offer five times the processing power of conventional 16-bit controls, speeding all operations from rapid feedrate acceleration and deceleration to table indexing and machining calculations. Multi-tasking capabilities enable the control to perform operations such as pallet changing and door opening/closing simultaneously, thus reducing non-cutting time.

Programming is aided by the control's conversational format and 50 help screens. Experienced users can easily bypass the help screens to adjust pre-determined machining parameters to fine-tune programs.

Built-in intelligence contains expert machinist data about optimum cutting conditions, tool-path determination, tool selection, and other variables. Additionally, the control's 32-bit technology provides the ability to synchronize multiple axes at high speeds without any mechanical linkage, making high-speed accuracy possible.

Program verification is assisted through the control's color-graphic displays that simulate programs and check machining processes (including boring) with single- and two-plane displays, zoom, and other graphic functions.

Mazak Corp, Florence, KY, circle 265.
COPYRIGHT 1993 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1993 Gale, Cengage Learning. All rights reserved.

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Title Annotation:software use in machining controls
Publication:Tooling & Production
Date:Aug 1, 1993
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