The University of Tokyo

Dmg Mori Company Limited

Dmg Mori Seiki Co., Ltd.

Yuki Terada

Shinji Ishii

Hiroshi Fujimoto

Koji Yamamoto

Teruaki Ishibashi

Satoshi Fukagawa

A machine tool includes a spindle retaining a tool, a spindle motor, a feed device relatively moving a workpiece and a tool with a feed motor, a spindle motor control unit, and a feed motor control unit. In a method of machining a workpiece with the machine tool, the spindle motor control unit continuously varies a rotational speed of the spindle in a periodic or non-periodic manner with a predetermined amplitude with respect to a target rotational speed. The feed motor control unit continuously varies a relative moving speed between the tool and the workpiece in synchronization with the spindle motor such that a ratio of the rotational speed of the spindle to the moving speed does not become constant at least in a predetermined time zone in which a spindle speed reaches a maximal value and a predetermined time zone in which the spindle speed reaches a minimal value.

Workpiece machining method

A controller has a varying speed signal generation unit generating a varying speed command signal varying at predetermined amplitude and period, a current control unit generating a current command signal based on the varying speed command signal, a feedback control unit generating a correction signal based on a deviation between the varying speed command signal and a present rotational speed of the spindle motor and adding the correction signal to the current command signal, and a learning control unit calculating a disturbance component caused by cutting resistance based on the deviation every predetermined rotation angle of the spindle motor and, in synchronism with a rotation angle of the spindle motor corresponding to the varying speed command signal input into the current control unit, generating a compensation signal based on the disturbance component corresponding to the rotation angle and adding the compensation signal to the varying speed command signal.

Controller for spindle motor

Using a machine tool, a workpiece is machined while periodically varying the rotational speed of a spindle thereof. Correlation data on correlation between a speed variation rate RVA of the spindle rotational speed, a speed variation period ratio RVF thereof, and vibration of a tool when machining the workpiece while periodically varying the spindle rotational speed is previously obtained. Based on the correlation data, the speed variation rate RVA and the speed variation period ratio RVF are set so that the vibration of the tool and machining accuracy are within their respective allowable ranges, and based on the set speed variation rate RVA and speed variation period ratio RVF, a variation amplitude and a variation period of the spindle rotational speed are determined. The spindle is rotated at the rotational speed varying at the determined amplitude and period with respect to a target rotational speed, thereby machining the workpiece.

Machining method

A parameter setting apparatus includes a calculator calculating a first resonance frequency &#x3c9;of a structure composed of a table, a rotor of a drive motor, and an object and a second resonance frequency &#x3c9;of a structure composed of a stator of the drive motor and a base using equations given below, and a setter setting a frequency band to be removed for a first damping filter based on the calculated first resonance frequency &#x3c9;and setting a frequency band to be removed for a second damping filter based on the second resonance frequency &#x3c9;.

Parameter setting method and parameter setting apparatus for positioning apparatus, and positioning apparatus provided with the parameter setting apparatus

Growing community of inventors

Nara, Japan

Yuki Terada