DEMAGNETIZATION METHOD

To process a workpiece while an electromagnetic chuck using an electromagnet is magnetized to adsorb the workpiece and cause demagnetizing current to flow through the coil of the electromagnet when the workpiece is detached, thereby performing demagnetization of the workpiece in a short time.SOLUTION: In a method of performing excitation by applying an alternating magnetic field using a coil of an electromagnetic chuck, a commercial power supply is stored in a capacitor, and a DC voltage which is 1.414 times as large as a commercial power supply voltage is alternately switched over time and applied to the coil as a pulse voltage, and a pulse voltage which is successively attenuated by setting the pulse width of a first wave of demagnetization and an attenuation rate of an alternating pulse is applied to supply an alternating current whose current peak value successively decreases linearly. When the pulse voltage width to be applied is 0.01 second or less, the minimum pulse width is switched to 1/10 or less, and a voltage pulse having a pulse width of 0.01 second to 0.0005 second is applied to the coil, thereby causing a minute alternating attenuated current to flow through the coil of the electromagnetic chuck.SELECTED DRAWING: Figure 3 【課題】電磁石を利用した電磁チャックを着磁させてワークを吸着した状態で加工し、ワークを取り外すに際し、電磁石のコイルへ消磁電流を流し、ワークの消磁を短時間で実施する。【解決手段】電磁チャックのコイルを用いて交番的な磁界をかけることにより励磁を行う方法において、前記コイルに、商用電源をコンデンサーに蓄え、商用電源電圧の１．４１４倍の直流電圧を時間の経過と共に交番的に切換えてパルス電圧として印加し、消磁の第１波のパルス幅、及び交番パルスの減衰率を設定することにより順次減衰したパルス電圧を印加して電流ピーク値が順次直線的に減少する交流電流を通電し、また印加するパルス電圧幅が０．０１秒以下になると最小パルス幅を１／１０以下に切り換えて、０．０１秒パルス幅から０.０００５秒パルス幅の電圧パルスをコイルに印加することより微小な交番減衰電流を電磁チャックのコイルに通電することを特徴とする。【選択図】図３