Moving Toward the Light in One Step
Light-emitting diodes (LEDs) are characterized by a long service life, minimal space requirement and high light yield. For these reasons, they are becoming increasingly important in optical systems. By employing multi-component injection molding, it is possible to produce complete LED lamps in a single step. Integration of the various functions such as lens and light conductor in conjunction with placing the illuminant and resistor into the mold reduces the number of manufacturing steps and increases quality by shortening the process and tolerance chain.
As part of a feasibility study conducted under the supervision of Oechsler AG, Ansbach, an LED light strip has been developed that is fully functional after production via insert and 3-component injection molding. The light strip is being used in a pocket-sized flashlight to demonstrate the technology.
The body of colored PC is produced first. Next, three lenses of transparent PA are molded in openings provided for this purpose. Then, a robot loads a resistor and the three LEDs. Following this, the body is completed by incorporating the third conducting component of PA and removed from the mold.
Loading uses standard holders commonly employed in the electronics industry. The mold was designed specifically with the requirements of the various resins in mind. While the body and lens are molded via hot-runner technology, the individual segments of the light conductor made of light-conducting resin are injection molded using a combination of hot-and cold-runner technology in a segmented three-plate mold.
The three-station rotary mold is indexed 120° from one station to the next by an electric drive. The three-plate mold design also provides for trimming, separation and ejection of the runners. They drop out and are collected in a bind under the machine.
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