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Networked CMMs save shoe leather.

With its four CMMs spread out over a mile-long circuit at its plant in San Diego, Solar Turbines Inc needed physical-fitness buffs to shuffle measurement data and programming for over 1000 inspection programs. A subsidiary of Caterpillar, Solar produces gas-turbine engines up to 12,600 hp as part of a variety of packaged compression, power-generation, and mechanical drive sets.

The solution to the CMM-data dilemma was a four-CMM network begun as part of a long-term move to flexible manufacturing. The four CMMs (all from Sheffield Measurement and located in different buildings) are: a large manual Cordax 805 in receiving to inspect incoming castings, a manual Cordax 1815 in fabrication, a direct computer controlled (DCC) Cordax Apollo Series RS-50 where airfoils and small components are machined, and a large DCC Apollo Series RS-150 where turbine wheels, compressor housings, and other large parts are manufactured.

Except for the receiving-area machine, all are used for first-piece inspection and in air-conditioned rooms. Inspectors operating the CMMs use the teach mode for programming, except for complex airfoils which are created on a PC and downloaded. Lead machinists in each area are being trained to operate the CMMs and free inspectors for more programming.

MIL-Q-52779A requires a manufacturer to have audit control over inspection programs. The intent is to lock in place valid inspection programs that cannot be altered to allow an out-of-spec part to pass. "We have to prove we have control of all CMM inspection software," says Tom Ellsworth, Solar quality engineer. "We also have to ensure uniform updating so all CMM operators are working in the same software environment. There are also routine chores such as backing up and archiving."

Network basics

Rather than hire a long-distance runner to shuttle the thousand part programs and hundreds of megabytes of inspection data, Ellsworth networked the four CMMs to a MicroVAX II using Sheffield's Sheffnet software. The MicroVAX, in turn, connects to a VAX cluster over Ethernet, from which hundreds of terminals can access CMM data, including a PC in Ellsworth's home.

Designed for flexible inspection cells, Sheffnet capabilities include a remote factory-control interface, advanced statistical analysis, database management, multipleCMM support, and status reporting. There is a routine tape backup of the two hard drives in the MicroVAX.

The MicroVAX cluster consists of several CPUs and disk drives that can be selected by name and data moved from one CPU to another to access particular software. System advantages

"The greatest advantage we derive from the system is the automatic weekly upload of inspection programs over Ethernet to the larger drives in the cluster," says Ellsworth. "DEC command language is the tool used to upload and compare current part programs to the previous week's versions. All newly generated part programs, modified programs, and recently deleted programs are automatically routed to separate directories for review as part of our software QA program. We can check new or changed programs to see if they follow proper conventions, and deleted programs can be held in a one-week buffer for emergency recovery."

When an operator is struggling with a programming or measurement problem, help is always close at hand on the network. If a problem can't be handled internally, Ellsworth can allow outside people to access the system. "Sheffield has dialed in on at least two occasions to help resolve a problem," he recalls. "In one instance, we made a mistake while upgrading the database, and were about to lose almost four weeks of measurement data, and Sheffield provided a fix."

Three months of measurement data is maintained on-line, and older data is archived over the network. If a part made months before doesn't fit, assembly people can access measurement data to help analyze the problem.

"The requirement for delivery of dimensional data along with the engine hardware is becoming a fact of life, too," Ellsworth points out. "There have been several occasions that have called for the regeneration of measurement data on a part that is ready for delivery. Archived data avoids delays for disassembly and remeasurement."

Beyond the Sheffield statistical package, company engineers can route measurement data to higher-level analysis and graphics systems they are more familiar wi seamlessly over the network.
COPYRIGHT 1991 Nelson Publishing
No portion of this article can be reproduced without the express written permission from the copyright holder.
Copyright 1991 Gale, Cengage Learning. All rights reserved.

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Title Annotation:Solar Turbines Inc.; coordinate measuring machines
Publication:Tooling & Production
Date:Feb 1, 1991
Words:694
Previous Article:Simultaneous engineering.
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