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SurfaceWorks Eases Design of Complex Antenna Surfaces

SurfaceWorks and CAD provide tightly integrated CAD and surfacing solution.

By Michael Brenner, EMS founder, president and principal consulting engineer

Engineering Metrology Services (EMS) was founded in 1992 and offers industrial coordinate measurement services, engineering design, and software consulting. Since its inception, we have measured and aligned radio telescopes, radar antennas, satellite communicationReflector top - click on thumbnail antennas, and compact antenna test range reflectors. We have also designed measurement tooling and antenna systems. More information is available at the EMS web site http://www.engr-metr.com.

We provide CAD design services, specialty analysis software, and industrial measurement services. Customers include Raytheon Co., Allied Signal, Radiation Systems, Inc., Smithsonian Astrophysical Observatory, Harvard Center for Astrophysics, Mission Research Corp., Atlantic Microwave, and MIT's Lincoln Laboratory.

EMS design challenges

For a consulting company, the biggest challenge is usually making connections with companies who need our services. Once that is accomplished, the rest is just hard work. Our customers demand accuracy, flexibility, timely response, and support. To meet these requirements, we often travel globally. EMS has worked on six continents, and we’re hoping to be sent to Antarctica soon. Last year we worked in Taiwan, California and Kwajalein. This year we’ll do field work in Alaska and Norway. Sweden and Alaska are on the calendar for next year.

To help us do our work we use SolidWorks for CAD design, SurfaceWorks for specialized surfaces for custom dish antennas, Visual Basic for software development, and MathCAD for generating analytical reports. We plan to start using CosmosWorks FEA software in the near future. SurfaceWorks has allowed EMS to expand the scope of its design work on specialized surfaces for compact range reflector antennas. We can now do more than we once could in less time. SurfaceWorks enables us to realize greater productivity, improved design flexibility, and timely response to customers.

Recent project

EMS is currently under contract to design and install a 21-foot compact antenna test range reflector for a major aerospace contractor. The indoor test facility will be completed in the autumn of 1999 and used to measure the Radar Cross Section (RCS) of military aircraft components.

Unlike dish antennas used on satellite communication systems, the low-noise and low-frequency operation of this test range requires a complex "rolled-edge" wrap-around reflector surface. The surface was developed by the ElectroScience Laboratory of the Ohio State University (OSU) for its low-noise characteristics. OSU provided it to EMS as a regular grid of more than 10,000 points in space. We used Visual Basic to format the points into rows, which were then imported into SurfaceWorks and built up into C-spline curves and then C-spline surfaces. A total of fourteen surfaces were knit together to make a solid curved object 16 feet wide by 14 feet high by four feet deep. The solid object was then imported into SolidWorks. There it was shelled, divided into seven discrete panels, and stiffened with ribs, bosses, and plates. The panels are currently being cast at a foundry in Franklin, OH.

We selected SurfaceWorks because of its compatibility with SolidWorks and its ability to create surfaces from imported point data. The learning curve was pretty quick. After reading the critical portions of the manual, we went through the tutorial step-by-step, and did some experimental runs to get a feel for things. Then we started on the real project. When we got stuck we got some very valuable pointers from the SurfaceWorks technical support staff, who also critiqued an early version of the surface model. From our first look at SurfaceWorks until we had a completed a surface model of the reflector was about three to four weeks.

SurfaceWorks benefits

We can now complete 20% of the design job that we previously had to subcontract out to others. In the case of the project described below, this brought about $25,000 of consulting in-house. This has given us a competitive advantage, simplified project management, given us much greater in-house control over technical details and schedules, and allowed us to offer a totally integrated solution.

Trends in the marketplace

In this reflector project we have been able to place "virtual reality" images of the design in-progress on the EMS web site at http://www.engr-metr.com/current.html in which our customer and manufacturing partners can zoom in, rotate, pan, and generally travel around and through various design options. This has streamlined decision-making, eliminated the need for time-consuming meetings, and saved money and time.

The foundry engineers doing the castings can get a good early feel for what they’ll be building, right on our web site. Later we’ll be placing DXF-format files on the web for ready-access by our sheet-metal manufacturing partners.

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