Okuma Corporation

Tatsuhiro Yoshimura

Fumitoshi Terasaki

Masaaki Nagaya

Masahiro Furukawa

Homare Adachi

Kenji Yoshimura

The present invention achieves machining operation without grind-burning and grinding crack and improves the profile accuracy of a workpiece, by automatically generating X/C axis data that controls the headstock and the wheel spindle head while taking into account speed, acceleration, change in acceleration and contact arc length. Storage means 33 for storing the time taken by the workpiece to make one turn, reference X/C axis data computing element 53 for computing machining data from given angle and a set of lift points to control the grinding peripheral speed constant within a range where the machine can follow, computing element 56 for computing contact arc during grinding from the X/C axis data, storage means 53 for storing limitation value of X axis based on the contact arc while changing it according to C axis, computing means 46 for storing said reference X/C axis data and computing speed, acceleration and change in acceleration while reading the reference X/C axis data by skipping a specified number of steps, and modifying element 57 for reducing said number of steps to bring the speed, acceleration and change in acceleration within limits when any of these values exceeds the limit are provided, thereby to carry out synchronous control of the work spindle rotation and reciprocal motion of the wheel spindle head according to the modified X/C axis data.

Method of grinding and machining non-circular workpiece and apparatus

A dressing method comprises the steps of rotating a rotary dresser at a high speed for dressing a surface of the grindstone, previous to contact of the rotary dresser with the surface of the grindstone, and detecting a rotational vibration caused by a bearing adapted to support the rotary dresser in rotation, by use of a vibration sensor for detecting a contact vibration having a specific frequency band generated when the rotary dresser in rotation comes into contact with the grindstone. Providing that the rotational vibration has been detected, an output signal from the vibration sensor is judged to be active, allowing the grindstone to be dressed. Prior to the execution of the dressing, failures in the vibration sensor and other deficiencies are detected. After dressing grindstone, a workpiece is ground and a load of a grindstone axle motor is detected to determine if dressing was positively performed.

Method of dressing grindstone for NC grinder

A dressing method comprises the steps of rotating a rotary dresser at a high speed for dressing a surface of the grindstone, previous to contact of the rotary dresser with the surface of the grindstone, and detecting a rotational vibration caused by a bearing adapted to support the rotary dresser in rotation, by use of a vibration sensor for detecting a contact vibration having a specific frequency band generated when the rotary dresser in rotation comes into contact with the grindstone. Providing that the rotational vibration has been detected, an output signal from the vibration sensor is judged to be active, allowing the grindstone to be dressed. Prior to the execution of the dressing, failures in the vibration sensor and other deficiencies are detected.

A numerical control unit for a non-circular workpiece fabricating machine automatically smoothes and interpolates lift data containing errors so as to obtain new substantially error-free lift data, and allows the fabricating machine to fabricate a non-circular workpiece with a smooth rotation of a main spindle and with less vibrations of a wheel spindle stock. The numerical control unit converts lift data whose pitch is unequal into lift data whose pitch is equal. Errors in the equal pitch lift data are extended by a second finite difference calculation, are repeatedly smoothed and interpolated until they meet an application criterion. Then, the lift data are subject to inverse calculation to obtain new lift data. The new lift data are used to obtain X/C-axis data taking a diameter of the wheel spindle stock and period of time per rotation of the workpiece into consideration. Thereafter, the workpiece is fabricated on the basis of the X/C-axis data.

Numerical control unit for non-circular workpiece fabricating machine

When a non-circular workpiece is to be machined by an NC cylindrical grinding machine, the latter is controlled such that the velocity of each of the main spindle and grinding head does not exceed a threshold allowable by the machine. A non-circle data pre-processing section is provided to convert a group of angle and lift points relating to the shape data into profile data to determine the complete circumferential length of the profile. The circumferential length of the profile is divided into line segments of minute and equal length at a plurality of division points. When the tool is brought into contact with the workpiece at each of the division points, a reference X/C axes data relating to the X-axis position of the tool and the rotational angle of the main spindle at this time is prepared. The reference X/C axes data are selected out to prepare temporary X/C axes data which in turn are used to determine the velocity, acceleration and rate of acceleration change in each of the main spindle and tool head. These determined values are compared with the respective thresholds. If they exceed the respective thresholds, the rate of selecting is changed. If the calculated values do not exceed the respective thresholds, the temporary X/C axes data is taken as modified X/C axes data. The machining will be carried out in accordance with the modified X/C axes data.

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Aichi, Japan

Tatsuhiro Yoshimura