Numerical controller having workpiece setting error compensation means

• US 8,041,447 B2
• Filed: 08/15/2008
• Issued: 10/18/2011
• Est. Priority Date: 10/04/2007
• Status: Active Grant

• Current Assignee: Fanuc Ltd (Fanuc Corporation)
• Original Assignee: Fanuc Ltd (Fanuc Corporation)
• Inventors: Sasaki, Takafumi, Otsuki, Toshiaki, Ide, Soichiro
• Primary Examiner(s): Decady; Albert
• Assistant Examiner(s): NORTON, JENNIFER L
• Application Number:
  US12/192,590
• Publication Number:
  US 20090093905A1
• Time in Patent Office: 1,159 Days
• Field of Search: 700/175, 700/193, 700/28, 700/30, 700/117, 700/159, 700/173, 700/174, 318/572, 318/568.15, 318/573
• US Class Current: 700/174
• CPC Class Codes: G05B 19/4086 Coordinate conversions; Other special calculations
• CPC Class Codes: G05B 2219/35557 Workpiece related data to axis related data
• CPC Class Codes: G05B 2219/50049 Control machine as function of position, angle of workpiece

Abstract

A numerical controller controlling a 5-axis machine tool compensates setting error that arises when a workpiece is set on the table. Error in the three linear axes and the two rotation axes are compensated using preset error amounts to keep the calculated tool position and tool direction in a command coordinate system. If a trigonometric function used for error compensation has a plurality of solution sets, the solution set closest to the tool direction in the command coordinate system is selected from the plurality of solution sets and used as the positions of the two rotation axes compensated in the above error compensation.

Claims

1. A numerical controller controlling a 5-axis machine tool for machining a workpiece set on a table using three linear axes and two rotation axes, the numerical controller comprising a workpiece setting error compensation means for compensating setting error arising during setting of the workpiece, the workpiece setting error compensation means including:

a tool position/direction calculation means for calculating a tool position and a tool direction in a command coordinate system based on command values;

an error compensation means for compensating error in the three linear axes and the two rotation axes based on preset error amounts in order to keep the tool position and the tool direction in the command coordinate system calculated by the tool position/direction calculation means; and

a solution selection means for, if a trigonometric function used for error compensation performed by the error compensation means has a plurality of solution sets, selecting, from the plurality of solution sets, a solution set closest to the tool direction in the command coordinate system calculated by the tool position/direction calculation means and using the solution set as the positions of the two rotation axes compensated in the above error compensation;

wherein the three linear axes and the two rotation axes are driven based on coordinates in the three linear axes and the two rotation axes obtained by the workpiece setting error compensation means.

2. The numerical controller of claim 1, wherein if a trigonometric function used for error compensation performed by the error compensation means has a plurality of solution sets with arctangent, arccosine or arcsine for the two rotation axes, the solution selection means selects, from the plurality of solution sets, a solution set closest to the tool direction in the command coordinate system calculated by the tool position/direction calculation means.

3. The numerical controller according to claim 1, further comprising a rotation axis operation range setting means for setting operable ranges of rotation axes in advance, wherein said workpiece setting error compensation means further comprises:

a rotation axis position rounding means for rounding positions of the two rotation axes obtained by the error compensation means so that the positions fall within the operable ranges set by the rotation axis operation range setting means;

wherein the three linear axes and the two rotation axes are driven based on the coordinates in the three linear axes and the two rotation axes obtained by the workpiece setting error compensation means.