Engineers at Merivaara Oy, in Finland had to redesign a medical examination lamp so it wouldn't get too hot. It used housings made from extruded aluminum profiles with injection-molded plastic end caps and faceted aluminum reflectors.
According to Jyrki Nieminen, R&D head for Merivaara, "The most important concern was the excessive heat generated by the lamp's metal reflector." Too much heat makes patients uncomfortable and also raises operating and exam room temperatures, affecting clinical staff. In addition, designers wanted to reduce costs by consolidating parts via metal-to-plastic conversion. "The switch to plastic would give us more flexibility for future versions of the lamp," Nieminen says.
The company chose a 30% glass-fiber-reinforced blend of polybutadiene terephthalate (PBT) and polyethylene terephthalate (PET) to replace the aluminum lamp housing. The Valox 865 resin, from GE Plastics, Pittsfield Mass., is rated for temperatures to 120°C, withstands harsh cleansers, and can be custom colored.
Designers determined that a high-performance polytherimide (PIE) was the best option for lamp reflectors. Reflectors injection-molded from Ultem 1000 PIE, in combination with aluminum metallization, produce what's called a cold mirror — it directs visible light downward while radiating infrared heat upward toward the top of the lamp and away from the patient.
Another benefit of Ultem PIE is its ability to be metallized without pretreatment, says Rob de Jong, GE Plastics industry manager. "GE has devoted significant resources to developing lighting for the health-care industry. The Ultem resin family delivers improved performance compared to metal reflectors in terms of temperature management, dimensional stability, and lighter weight."
The Merilux X1 lamp redesign let designers eliminate secondary processes. Two injection-molded halves replace a three-part metal assembly that had hard-to-clean through-holes and hard-to-reach surfaces — an important consideration in healthcare environments. In addition, GE provided an exact color match, thus eliminating a costly secondary painting step.
Injection molding let designers mold in assembly elements and fixture points instead of adding them later, thus reducing cycle times. Injection molding the reflector improved faceting and light-source positioning.