AEG/Robert Hofmann Modellbau GmbH

Stereolithography prototypes allow AEG Hausgeräte to apply concurrent engineering and, subsequently, to halve the company's typical product development time.

The Challenge
Design engineers at AEG Hausgeräte were assigned the arduous task of bringing a
completely new vacuum cleaner to market in just 13 months. Given the latest consumer information, designers were to apply this knowledge to develop a competitive product in half the time of their usual development time frame of 2.5 years. Missing the deadline could cost the company its share in the aggressive vacuum cleaner market.

The 13-month time frame would encompass the entire design of the product, prototyping and manufacturing of initial shipments. Furthermore, the new Yallo vacuum cleaner design had to prove reliable and robust.

The Results
AEG Hausgeräte turned to Robert Hofmann Modellbau GmbH and Hofmann Wekzeugbau and that group's stereolithography expertise to meet its tight deadline. In 140 hours, AEG had stereolithography (SL) prototypes from which its designers could analyze form, fit up and assembly of components. Digitized surface data taken from a foam model of the vacuum cleaner allowed Hofmann engineers to create a 3-dimensional CAD solid model of the vacuum cleaner. A master pattern, milled using the initial CAD model, was a base from which AEG engineers designed the components. Hofmann engineers quickly created prototypes of all components using stereolithography.

The SL prototypes proved useful in analyzing assembly of the components, allowing fine-tuning of the primary CAD model and quick building of iterative SL prototypes. The SL prototypes also verified tooling designs that would meet production molding demands. AEG easily met its deadline, turning out an easy-to-produce and accurately assembled vacuum cleaner in just 13 months. Stereolithography technology allows AEG Hausgeräte to:

• Cut product development time by 56%
• Identify flaws in fit-up not visible in 3-dimensional CAD models
• Optimize design criteria before building hard tooling
• Evaluate form and fit of all components
• Save DM 30,000, nearly U.S. $20,000, in tool development costs

"We could not have carried out a project like this without SL prototypes. They help us save time and, above all, costs for our customers."
                                                      - Robert Hofmann, President
                                                      Robert Hofmann Modellbau GmbH

The Process
Design engineers at AEG Hausgeräte used initial design ideas to create a foam model of its new vacuum cleaner. Digitizing the foam model using EDS Unigraphics and CATIA software, designers at Robert Hofmann Modellbau created a solid-CAD model that provided NC milling information to machine a master pattern.

Engineers from AEG, Hofmann Modellbau and Hofmann Werkzeugbau used the master to verify the surface data as well as check the aesthetic design of the product.

The master pattern became a foundation upon which engineers designed the 15 components that make up the vacuum cleaner. These components included upper and lower shell halves, controls, handle parts, buttons, cable roller, micro-filter trim, vacuum cleaner cover, latches and fan cup.

Downloading the 3-dimensional CAD model for each component to an SLA 500 system at Hofmann Modellbau, AEG was able to obtain prototypes based on its initial design in only 140 hours.

The fit-up of these components, especially the fan cup, was critical. The SL prototypes, which held tolerances of 0.05 mm, allowed designers to test form and fit of the components. Assembly of the prototypes revealed design flaws not detected in the 3-dimensional CAD model. Modifications to the CAD model were quickly turned into SL prototypes, allowing designers to fine-tune component design before building any hard mold-making tooling. AEG Hausgeräte, using SL prototypes, applied concurrent engineering to successfully introduce its new Yallo vacuum cleaner in just 13 months.

The Tools
EDS Unigraphics software, version 10
CATIA software
SLA 500 system

Company Profile
AEG Hausgeräte, headquartered in Nuremburg, Germany, is a leading manufacturer of consumer products. Employing 9,000 people worldwide, AEG manufactures washing machines, vacuum cleaners, fabric-care appliances, coffee makers and other consumer products. Robert Hofmann Modellbau is a rapid-development service provider offering
comprehensive design, production tooling, rapid tooling and prototyping, tooling design and NC data generation. Hofmann primarily serves the auto industry and its vendors. The company also serves the household-appliance, consumer-products, toy, ceramic and computer industries.