CAD-CAM - flying high.
Of all major US industries, aerospace is one of the heaviest users of computer-aided design, drafting, analysis, and NC programming (CAD/ CAM/CAE). At the same time, the industry is highly diversified, ranging from assemblers of aircraft and spacecraft, through builders of engines and landing gear, to suppliers of subassemblies, components, and parts. Companies range in size from those with hundreds of thousands of employees, to those with fewer than ten.
Despite this great diversity, however, aerospace companies using CAD/CAM/CAE consistently report the same results. Among these are increased speed in product design and NC programming, faster response to changes, better use of capital equipment--and, at the bottom line, lower costs.
Following are brief case histories from different industry segments. Perhaps you'll be able to apply ideas from these stories in your own company's operations.
Shielding our shuttles
When a NASA space shuttle reenters the earth's atmosphere after a mission, friction generates temperatures as high as 2300 F on the vehicle's outer surfaces. To protect the vehicle and its crew, Rockwell International's Space Transportation Systems Div, general contractor for space shuttles, applies reusable insulation tiles made of a pure silica fiber material. Design, machining, and installation take place at the company's assembly facility in Palmdale, CA.
Developed by Lockheed Missiles & Space Co, Sunnyvale, CA, the material transfers heat so slowly that a piece can be held in bare hands only seconds after it is removed from a 2300 F oven. In those few seconds, heat has rapidly escaped from the tile surfaces, but the fiery internal heat has not yet moved out to the surfaces.
At their Palmdale facility, Rockwell takes measurements from a shuttle's exterior surfaces, and develops a pattern for insulation tiles. From this pattern, drawings for individual tiles are made.
In final form, the tiles range from 1" X 1" up to 12" X 12". Most tiles have complex, curved surfaces that exactly match the shuttle's shape.
To speed design and machining processes, Rockwell uses a CAD/CAD system from Numerical Control Computer Services (NCCS), Irvine, CA. Running on a DEC MicroVAX computer, the software--tradenamed NCL--provides fully integrated, 3-D wireframe design, drafting, and NC programming. This CAD/CAM system also includes several Tektronix 4224 graphics terminals and a Hewlett-Packard plotter.
Machine code developed from postprocessed NC programs goes over a small DNC network to CNC machining centers having three to five programmable axes. Most machining of the silica billets is done with end mills faced with industrial diamonds. Machine spindles operate at speeds to 10,000 rpm.
According to Tom Baal, senior NC programmer at Rockwell, the CAD/CAM system has reduced combined design and machining time for tiles by 50 percent. Total manufacturing costs are lower than previously, and the procedure is easier. "NCL gives us the ability to visualize each step throughout the entire, complex tile-making procedure," Baal says.
For information on NCL CAD/CAM software, write to NCCS, 17321 Murphy Ave, Irvine, CA 92714. Phone (714) 474-7444.
Cutting antenna parts
One of the nation's leading suppliers of radar and microwave antennas for military aircraft is Nurad Inc, Baltimore, MD. Five years ago, Nurad felt it needed to reduce costs by increasing speed and efficiency of design and manufacturing procedures. The company then installed the first of four E-Z-Cam CANC systems from Bridgeport Machines Inc, Bridgeport, CT.
According to Robert Sidelinger, senior NC programmer at Nurad, these CANC systems have helped reduce part-programming time by a factor of 8:1. "Before installing E-Z-Cam, a typical program took one to two days of work," he says. "Now we can develop that same program in one to two hours."
An antenna begins as a series of rough refined, final design drawings of individual parts or molds are made. Programmers then construct electronic geometry drawings on an E-Z-Cam system. A 3-D software module called E-Z-Surf Plus is used to draw complex surfaces.
"This software enables us to draw and machine parts that would have been impossible or cost-prohibitive to make manually," says Sidelinger. "In many cases, postprocessed machine code runs over 1.5 million characters of text. Writing programs of that length would take an excessively long time."
From the geometry, a machining program is developed. This is post-processed and downloaded directly to a CNC machine tool, or to a networked CNC machine by RS-232 over a small DNC network. The company generates 10 to 15 part programs a day. Lot sizes range from 100 to 9000.
To machine antenna parts--most of them are aluminum--Nurad uses 12 Bridgeport CNC milling machines and six Matsuura CNC machining centers. All their CNCs are connected to the DNC network.
All four E-Z-Cam systems include NEC PCs. The older systems, installed in 1984, use Model Ho3 PCs with 8086 processors and 8087 math coprocessors. The newer systems, called E-Z-Cam II, have Model 286 PCs with 80286 processors and 80287 math coprocessors. These PCs include 40 MB hard disks.
To develop long, complex part programs for sculptured surfaces, Nurad lets the Model 286 crunch numbers overnight. A complex program may require up to five hours of computation.
Between the PCs and CNC units, the company has installed E-Z-File program storage devices. These accept part programs stored on floppy disks, and can either download to a CNC or upload to a PC.
"Our machine tool CNCs have maximum program storage capacity of 200 KB each," Sidelinger explains. "These intermediate storage devices enable us to store and download long part programs without tying up the PCs."
As a result of speeding up the NC-programming process, Nurad has been able to pass along cost-savings to its customers. "What's more, we're now able to react quickly to changes or modifications in antenna designs, and still deliver orders on time and with minimum disruption," Sidelinger concludes.
For information on E-Z-Cam systems, write to Bridgeport Machines Inc, 500 Lindley St, Bridgeport, CT 06606. Phone (203) 367-3651.
Making airframe parts
Manufacturers of aircraft, spacecraft, missiles, and rockets make many parts in house, but they also job out much work to fabricators, machine shops, and tool and die shops. One such job shop is Davis Tool Inc, Hillsboro, OR. Founded in 1980, this 73-person contract machining company produces various parts for Pacific Northwest OEMs, including Boeing Commercial Airplane Co, Seattle, WA.
About five years ago, Davis Tool's managers were looking for ways to increase speed and efficiency of part design and NC programming. After searching the CAD/CAM marketplace, the company bought a Smart-CAM NC programming system from Point Control Co, Eugene, OR, and a Cadkey CAD system from Cadkey Inc, Manchester, NH.
The two systems interface through SmartCAM's CAM Connection software, forming a fully integrated CAD/CAM system. This runs on any of 20 PCs, each of which has an 80286 or 80386 microprocessor and corresponding math coprocessor. A shop-wide Ethernet local-area network links the PCs, and ties them to CNC units on 19 machine tools and one Sheffield CMM. A 130 MB file server provides extra storage capacity.
For new jobs, programmers input geometry directly into SmartCAM. Tool and fixture drawings and specs are designed in Cadkey, then sent to SmartCAM.
For jobs that were programmed on other CAD systems, CAM Connection software allows programmers to bring part geometry into Cadkey for design of new fixturing. Updated CAD files are then moved to SmartCAM for generation of new machining programs.
In the shop-wide network, all information relating to a given job is available to anyone with access to a PC or CNC unit. Schedules are put on the network as soon as a new job comes in. For each new job, a programmer creates a directory on the file server, which also stores process plans and other files created in SmartCAM.
The company has dedicated four CNC machine tools--two Kuraki vertical mills and two Okuma horizontal mills--to Boeing jobs. The other 15 are available on demand for special processing. Most parts are machined from titanium or stainless steel.
Typical of parts made at Davis Tool is a door-hinge fitting installed in Boeing 767s (photo). For parts such as this, Boeing provides dimensioned part prints. Certain dimensions that may be missing from these drawings are added in Smart-CAM.
Some parts have oddly shaped pockets with islands. To minimize and simplify machining, the company puts these parts on four-axis or five-axis indexers, and uses standard end mills. SmartCAM's interactive viewing capability allows programmers to dynamically rotate part drawings on-screen and verify cutter paths from several angles.
Using SmartCAM's template files, programmers created a code generator for the CMM. Part geometry for NC programming is used for a quality control program. This is converted into NC code that drives the CMM.
Since installing SmartCAM and Cadkey, Davis Tool has been able to handle more complex parts but still meet just-in-time delivery requirements. Data management has improved greatly, and much less time is needed for design, drafting, and NC programming.
For example, in some complex jobs, NC programming time dropped from four hours to 40 min. The longer the program, the greater the savings.
For information on SmartCAM, write to Point Control Co, 2468 W 11th St, PO Box 2709, Eugene, OR 97402. Phone (503) 344-4470.
Designing landing gear
Cleveland Pneumatic Co (CP), Cleveland, OH, is one of the world's leading suppliers of landing gear for commercial and military aircraft. Customers include Boeing, McDonnell-Douglas, British Aerospace, Grumman, Sikorsky, Rockwell International, Bromon, and Gulf-stream.
Six years ago, CP perceived a need to convert from manual product design and analysis to CAD/CAM. "A number of our customers wanted to send us drawings electronically and eliminate transfer of paper," says John Rembert Jr, supervisor of design engineering. "They felt electronic transfer would be more expedient. Moreover, drawings would last longer and would be easier to change or update.
"On top of that, we wanted to shorten our lead-times and deliver detail or layout drawings to customers more quickly. A CAD/CAM system plus electronic transfer by IGES appeared to be the best solution."
So in 1983, CP installed a Schlumberger Bravo CAD/CAM system with six workstations. Since then, the company has added two more workstations.
Six of the eight workstations are used exclusively in design engineering for design, drafting, and analysis. The six are on a small network served by a DEC VAX 751 minicomputer. Also part of this system are a Versatek electrostatic plotter, Schlumberger hard-copy printer, and Benson color plotter.
Bravo CAD/CAM software provides 3-D color wireframe, surface, and solid modeling. Programmers perform design and drafting of parts and assemblies, plus finite-element and kinematic analysis of assemblies.
Served by a DEC VAX 750 mini-computer, the other two workstations are used by CP's manufacturing engineering dept for generation of machining and assembly process plans. A central library of CAD drawings is accessible to people in both design and manufacturing.
Typically, a landing-gear project begins as a set of preliminary drawings or data received electronically from a customer. IGES conversion translates the graphics files into Bravo code. Programmers refine the drawings in 3-D, and perform analyses of the electronically created assemblies.
In some cases, engineers employ detail drawings to build, part by part, a full-scale wooden model of a landing-gear component. This model can be used for predicting weight-reduction areas and possible manufacturing problems regarding tool clearances.
Included in most kinematic analyses are studies of linkages and clearances. Results of the studies are used to refine detailed part drawings in CAD.
"We find that making changes in CAD is much faster than on a drawing board," Rembert observes. "This alone would be enough to justify use of CAD.
"In some projects, it takes longer to generate new drawings in CAD than it would on paper. Revisions and updates can be done much more quickly in the electronic medium, however. The net result is a large savings of time."
For details on Bravo CAD/CAM systems, write to Schlumberger Technologies, CAD/CAM Div, 4251 Plymouth Rd, PO Box 986, Ann Arbor, MI 48106. Phone (313) 995-6000.
PHOTO : These seven tiles show the variety of shapes required on each shuttle. No two in a 24,000-tile shipset are exactly alike; each must be designed, machined, and installed individually. The coating is a black borosilicate glass, which is baked onto tiles destined for a shuttle's underside. The main material in tiles is a silica fiber that weighs 9 to 12 lb/cu ft, depending on composition. Source: Lockheed Missiles & Space Co.
PHOTO : At Rockwell's assembly facility in Palmdale, CA, workmen attach tiles to a shuttle body panel. Coated, machined tiles are bonded to strain-isolator pads of Nomex felt. Workers apply a room-temperature silicone adhesive to attach felt pads and tiles to a shuttle's aluminum skin. Clearance between tiles is 0.025" min, 0.065" max. Source: Rockwell International.
PHOTO : Artist's conception of how a NASA space shuttle looks as it re-enters earth's atmosphere after a mission. Note that the undersurfaces glow red-hot. Temperatures on the vehicle's outer, lower surfaces may reach 2300 F during re-entry. Some 24,000 tiles absorb heat and prevent it from harming the vehicle or its occupants. Source: NASA.
PHOTO : Typical parts made by Nurad Inc for assembly into aircraft radar and microwave antennas. Note the complex curves that must be machined. The company now does almost all its NC part programming on PC-based CANC systems. The dime indicates relative size.
PHOTO : At Davis Tool Inc, this screen display shows a drawing from a machining program for a door hinge. Each color in a tool path indicates a different tool to be used. Source: Point Control Co.
PHOTO : Door-hinge fittings are among the parts machined by Davis Tool Inc for Boeing airplanes. A finished part rests on raw forgings. source: Point Control Co.
PHOTO : A Boeing 767 takes off over Puget Sound west of Seattle. Davis Tool Inc, Hillsboro, OR, provides precision machined parts for this and other Boeing models. Source: Boeing Commercial Airplane Co.
PHOTO : At Cleveland Pneumatic Co, landing gear are put through thousands of retraction/extension cycles to validate expected operating life. The company has eight CAD/CAM workstations, and is considering addition of more stations to the system. Source: Cleveland Pneumatic Co.
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|Author:||Quinlan, Joseph C.|
|Publication:||Tooling & Production|
|Date:||Apr 1, 1989|
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