Casting Study: Housings for Laser Photocoagulator

The laser photocoagulator is used in the treatment of eye disease, particularly the treatment of broken blood vessels within the eye. Such a sensitive – and expensive – high-tech tool needs a housing which, besides its functional qualities of soundness, strength and durability, has to be ergonomically correct, and to give an immediate impression of quality and efficiency. Investment castings were considered – as quantities are not large – but machining and handling costs, and lack of inherent accuracy made this alternative unattractive. Plastic mouldings lacked the necessary weight and rigidity. Finally, zinc alloy castings (to BS 1004A) were chosen to achieve the required weight, rigidity and finish, at reasonable cost. Although tooling costs were relatively high, the finished component costs were attractive. A total of four castings are used: two to form the head cover, and two to form the casing for the control panel.