Customer References - SennheiserTHE SHAPE OF SOUND3D CAD in headphone development Only manufacturers who constantly revise and optimize their methods of product development are able to maintain a leading edge in today's market. One manufacturer in the entertainment-electronics sector followed the path from the drawing board via 2D CAD and the early days of solid modeling to a latest-generation solid modeler. Written by Wolfgang H. Niehoff and Ulrich Sendler in April 94 Translated by Siegmar Siegel Home-entertainment connoisseurs would miss the pitch of perfection if a certain company of acoustic specialists was not quite so good at its job. Nor would they be alone: Sennheiser has also supplied the equipment for numerous public performances. The company's engineering excellence has contributed to audience enjoyment of musicals such as "Cats", "Starlight Express" and "Phantom of the Opera". Wireless microphones and pocket-sized mini-transmitters have long been the norm for performers who delight their audiences by roller-skating across the stage. Guitar virtuosos giving their very best need artistic freedom of movement to perform. Headphones, microphones, infrared and high-frequency transmission are the fields in which the company ranks among those who call the tune. Sennheiser is based in Hannover, Germany, but the fame of their ability has spread far beyond the borders of Germany, and some 60 percent of production now goes abroad.
Sennheiser went CAD in 1987 with Hewlett-Packard's 2-D application HP PE/ME10. Ease of use and straightforward customizing were the telling features of the system back then, and within the space of a year all the company's designers had forsaken their drawing boards in favor of on-screen designing. The company now operates 27 installations. From 2D to 3D In 1991 the company installed its first three HP PE/ME30 seats. Even though this modeling system still warranted improvement in a few points, there was soon no doubting the potential for boosting productivity through 3D design. Rapid prototyping cuts the time needed to develop working prototypes so dramatically that in recent years virtually every single product has been designed with 3D CAD. HP PE/SolidDesigner, the new solid modeler, has been in use since the fall of 1993. Based on the popular Acis geometry kernel, the new solid modeler improves on the older system in several major ways. From the user's point of view the most significant advance is the ability to use free-form surfaces along with rule-based bodies and faces to define the solid model. Wire-frame, surface and solid geometries can be combined at will - the classic split between different models no longer applies. The procedure adopted in the development of a new headset is a case in point that aptly illustrates the natural functionality and benefit for users in industry.
Acoustic requirements can to some extent be expressed in terms of precise parameters that ultimately produce a certain sound experience. Such parameters constitute one central criterion by which this new development stands or falls. The second is design- increasingly important in this market as in others. The designer who sets out to construct an attractive product must work within certain boundary conditions (such as those presented by current-production components). The result is the hardware sketch, a physical model already approximating closely to the final lines of the finished product. When the model has been tested and corrected and finally accepted, it is digitized and the data loaded into HP PE/ME10. The system converts the data into B splines, which are virtual "slices" through the outer skin of the new headset. The central role of the 3D model The Loft command of the modeling system applies a free-form surface over this ribbing. The digitized design model is thus turned into a CAD solid model ready to be employed in a number of ways:
The advantage over conventional development methods is perfectly obvious. The stereolithographic body, plastic model and tool are lifted directly from the CAD part. Instead of time-consuming problem analysis, correction is fast and simple and involves only a single source - the solid model. Development in half the time Progress in terms of user benefit is measurable. The sound patterns are impressive, and so too are the cost savings. The manufacturer gave the go-ahead for the new series in November 1993. The finished product will be the pride of hi-fi listeners by August 1994. The time from initial idea to production is a mere nine months, as compared with one and a half to two years for a comparable product in the past. Customer pressure is the motivating force. Whereas a series could be expected to have a life cycle of between five and seven years in the past, the market now demands new-look, new-feel, new-experience products every two to three years. Free-form surfaces are a prime example, because only a few years ago they called for enormous outlay - and the over-the-counter price of the finished product was correspondingly high.
Slowly but surely, the designers in Hannover are already opting away from 2D toward solid modeling. The rate of change is determined by the time the designers need to familiarize themselves with the new techniques. All training for mechanical CAD is in-house within the framework of system support and maintenance, which also includes the development of company-specific macros, the testing of new versions and on-the-spot solutions to specific problems. Michael Nickel bears responsibility for all aspects of CAD in mechanical design. The down-home feeling The new data structure is only one of the clear benefits that have emerged since the volume modeler was introduced:
Workplanes can be defined at will, a feature that cuts out many complex stages in design. The HP implementation of feature-based modeling, too, has proved extremely useful. When the operator selects a particular detail - such as a rib or a pocket - the software automatically analyzes the relationships with adjacent elements and recognizes contiguous features. The geometry identified in this way is easily moved, enlarged, reduced, copied, mirrored or manipulated in other ways. The new system allows the designer to work directly on the solid model. The designer can pick aces or individual parts without having to execute complicated Boolean operations for each modification. As free-form surfaces become more and more important, customers are eagerly awaiting the next development. The technology partnership between Hewlett-Packard and Cisigraph will bear fruit in the fall of this year. The new arrival will be a special Strim 100 free-form package for use in conjunction with SolidDesigner. Sennheiser will be among the Beta customers, as it was when solid modeling came of age last year. Standard functions for the tracing of scanned surfaces, face generation and graphically interactive manipulation of existing free-form geometries are the new features. These will be part of the package in the next product generations and beyond. About the authors Dr.-Ing. Wolfgang H. Niehoff, born 1945, studied radio-frequency engineering and electrical acoustics at TU Dresden and was Head of Design for Praecitronic (electronic instruments) before joining Sennheiser in 1987. He is now Head of Development. Dipl.-Ing. Ulrich Sendler, born 1951, trained as tool-and-die maker and NC programmer before studying precision engineering at FH Heilbronn. Worked in CAD software development and in trade publications, freelance journalist and management consultant since 1989. |