Development of polarity-changeable magnetizer for manufacturing coding patterns in rotary encoder

Demands for high precision machine tools have been increased as technology advances. Such demands require higher position control to allow the machine tools to produce higher precision end products. To facilitate the position control, magnetic and optical encoders are been widely used in the machine tools. Due to its advantage in withstanding hard environment such as oil, grease and dust over an optical encoder, along with its wide applications in industrial position control, a magnetic encoder has become a desirable choice for machine tools. The objective of this study is to develop a polarity changeable magnetizer for manufacturing coding patterns in a rotary encoder which is used to monitor runout errors for rotating components in machine tools. As opposed to commonly used capacitive pulse magnetizer in which significant amount of energy is required for its electromagnets that potentially causes high energy hazard, in this study, a polarity changeable permanent magnet is proposed and investigated through parameter studies to overcome such issue with the aim placed on producing sufficient magnetization on a thin silicon steel plate to produce desirable coding patterns on the rotary encoders.