Numerical controlling unit having tool-breakage detecting function

• US 6,859,680 B2
• Filed: 02/28/2003
• Issued: 02/22/2005
• Est. Priority Date: 03/01/2002
• Status: Active Grant

• Current Assignee: Toshiba Kikai Kabushiki Kaisha
• Original Assignee: Toshiba Kikai Kabushiki Kaisha
• Inventors: Fujita, Jun, Katoh, Kouichi, Matsumoto, Ichiro
• Primary Examiner(s): Picard, Leo
• Assistant Examiner(s): Rapp, Chad
• Application Number:
  US10/375,101
• Publication Number:
  US 20030167100A1
• Time in Patent Office: 725 Days
• Field of Search: 700/96, 700/159, 700/170, 700/174, 700/175, 700/177, 700/182, 700/188, 702182-186, 408/6, 408 8- 13, 318/565, 318/566, 318/563, 318/537, 318/568.18, 318/571
• US Class Current: 700/177
• CPC Class Codes: G05B 19/4065 Monitoring tool breakage, life or condition
• CPC Class Codes: G05B 2219/37246 Compare estimated torques of different axis with reference for breakage
• CPC Class Codes: Y10T 408/14 Responsive to condition of Tool or tool-drive
• CPC Class Codes: Y10T 408/165 to control Tool rotation

Abstract

A numerical controlling unit includes: an inputting part into which a machining program is inputted; an analyzing part that analyzes the machining program to generate an instructed spindle rotational speed and calculates a spindle load ratio of a load applied to a spindle under a machining condition according to the machining program to a spindle load caused when the workpiece is machined: and a distributing part that generates, based on the machining program, a distribution amount per unit period inputted into a feed-axis servo driver. A spindle-rotational-amount-command outputting part receives the instructed spindle rotational speed and outputs a spindle-rotational-amount command for commanding a rotational amount per unit period which is inputted into a spindle driver. A cutting-load-for-judgment calculating part calculates a reference torque value based on the spindle load ratio, the distribution amount, and the spindle-rotational-amount command. A spindle-load comparing part compares the reference torque value with a load torque value which is feedback inputted by the spindle driver and outputs a tool-breakage detecting signal when the load torque value is higher than the reference torque value.

Claims

1. A numerical controlling unit comprising:

an inputting part into which a machining program for machining a workpiece is inputted;

an analyzing part that analyzes the machining program to generate an instructed spindle rotational speed and calculates a spindle load ratio indicating a ratio of a load applied to a spindle under a machining condition according to the machining program, with respect to a spindle load being caused when the workpiece is machined under a machining condition of a certain reference;

a distributing part that generates, based on the machining program, a distribution amount per unit period to be inputted into a feed-axis servo driver for moving a feed axis;

a spindle-rotational-amount-command outputting part that receives the instructed spindle rotational speed and outputs a spindle-rotational-amount command for commanding a rotational amount per unit period;

a spindle driver into which the spindle-rotational-amount command is inputted;

a cutting-load-for-judgment calculating part that calculates a reference torque value based on the spindle load ratio outputted by the analyzing part, the distribution amount outputted by the distributing part, and the spindle-rotational-amount command outputted by the spindle-rotational-amount-command outputting part; and

a spindle-load comparing part that compares the reference torque value with a load torque value which is feedback inputted by the spindle driver and outputs a tool-breakage detecting signal when the load torque value is higher than the reference torque value.

2. A numerical controlling unit according to claim 1, wherein

the machining program includes a feed speed indicating a relative speed between the workpiece and a tool, and additional machining information relating to the workpiece and the tool.

3. A numerical controlling unit according to claim 1, further comprising:

a spindle-override part that instructs a ratio for increasing and decreasing a rotational speed of a spindle, wherein

the spindle-rotational-amount-command outputting part generates a spindle-rotational-amount command for commanding the rotational amount per unit period by multiplying the instructed spindle rotational speed by the ratio instructed by the spindle-override part.

4. A numerical controlling unit according to claim 2, further comprising:

a spindle-override part that instructs a ratio for increasing and decreasing a rotational speed of a spindle, wherein

the spindle-rotational-amount-command outputting part generates a spindle-rotational-amount command for commanding the rotational amount per unit period by multiplying the instructed spindle rotational speed by the ratio instructed by the spindle-override part.