Punch press system and its control method

A punch press system in which the operation of a punch press is controlled by a numerical control unit, said punch press system comprising:

• a ram having an end to which a tool for pressing and punching a workpiece is attached;
• a servo motor for said punch press to control a linear movement of the ram;
• a table to fix the workpiece;
• and
• a servo motor for said table to position said table;
• and the numerical control unit comprising:
• a position control means for controlling the position of said table by operating said servo motor for said table according to a working program;
• a press operation data storage means for storing an operation command to be issued to said servo motor for said punch press;
• and
• a press operation control means for reading out the operation command stored in said press operation data storage means, and for controlling said servo motor for said punch press according to the operation command;
• wherein said position control means is provided with a function for issuing a read-out start signal to said press operation control means at a time prior to a time at which position control is completed in one working cycle, by a predetermined time;
• and
• when said press operation control means receives the read-out start signal from said position control means, said press operation control means starts to read out the operation command for controlling said servo motor for said punch press from said press operation data storage means.

A method of controlling a punch press system, in which a first servo motor controlled by a CNC unit drives a table on which a workpiece is loaded and fixed and a second servo motor controlled by said CNC unit drives a press tool of a punch press comprising the steps of:

• starting the position control of the table by driving the first servo motor for said table, and then starting the driving of the second servo motor for said punch press at a time prior to the time when the position control for the table is completed, by the time which is close to but not exceeding an approach time required for the press tool to approach to a workpiece from its home position;
• lowering the press tool halfway at rapid acceleration according to an operational pattern stored in the CNC unit during approach to the workpiece started at the start of operation, and then lowering the press tool to an approach end position while gradually reducing a lowering speed;
• lowering the press tool at a low substantially fixed speed during press operation following the approach;
• and
• lowering the press tool at rapid acceleration again during punching operation after press operation is finished, and then lifting the press tool halfway at rapid acceleration during return to the home position after the punching operation is completed, and afterward, stopping the press tool at the home position, while gradually reducing a lifting speed.