Numerical control method and apparatus with feedrate difference

Claim 3

A numerical control apparatus for machining a workpiece under a machining program, comprising: means for establishing an allowable feedrate difference setting for a control axis of the numerical control apparatus; means for calculating a feedrate difference for said control axis from command data in successive blocks in the machining program for said control axis; means for calculating a deceleration for said control axis from said allowable feedrate difference setting and said calculated feedrate difference; and means for calculating a point to start deceleration in a present block from said calculated deceleration, whereby said feedrate difference will be held within said allowable feedrate difference setting at a block-to-block junction based on said calculated deceleration.

Claim 4

A numerical control apparatus for machining a workpiece under a machining program, comprising: means for establishing an allowable feedrate difference setting for a control axis of the numerical control apparatus; means for calculating a feedrate difference for said control axis from command data in successive blocks in the machining program for said control axis; means for calculating a deceleration for said control axis from said allowable feedrate difference setting and said calculated feedrate difference; and means for calculating a point to start deceleration in a present block from said calculated deceleration, whereby said feedrate difference will be held within said allowable feedrate difference setting at a block-to-block junction based on said calculated deceleration.

Claim 5

A numerical control apparatus according to claim 2, wherein said machine tool has a plurality of control axes, said establishing means including means for establishing a plurality of allowable feedrate difference settings for said control axes, respectively.

Claim 6

A numerical control apparatus according to claim 3, wherein said deceleration calculating means includes means for calculating a plurality of decelerations for said control axes, respectively, and for specifying one of the calculated decelerations.

Claim 7

A numerical control apparatus according to claim 4, wherein said deceleration calculating means includes means for calculating the deceleration for each of said control axes from the present block to the following block based on a commanded feedrate stored in the block for each control axis, a present feedrate corresponding to the block for each control axis, and the established block-to-block feedrate difference setting for each control axis.

Claim 8

A numerical control apparatus according to claim 4, including means for selecting the smallest one of said calculated decelerations.

Claim 9

A numerical control apparatus according to claim 4, wherein said means for calculating a point to start deceleration comprises an interpolator for issuing a product of the smallest one of said decelerations supplied from said deceleration calculating means and the feedrate of an object controlled by the numerical control apparatus as a feedrate command signal.

Claim 10

A numerical control apparatus according to claim 7, wherein said interpolator includes means for calculating a point to start deceleration in the present block and for calculating initial and final feedrates upon deceleration.

Claim 11

A numerical control apparatus according to claim 4, wherein said means for calculating a point to start deceleration comprises an interpolator, said point to start deceleration being determined by a product of the present feedrate for each of said control axes and the feedrate difference which most deviates from the allowable feedrate difference setting for each control axis between the present block and the following block.

Claim 12

A numerical control apparatus according to claim 4, wherein said establishing means includes means for establishing the allowable feedrate difference setting for one of said control axes which is subject to a larger feedrate change than the other control axes.

Claim 13

A numerical control apparatus according to claim 10, wherein each of said allowable feedrate difference settings is selected and entered beforehand as a constant.

Claim 14

A numerical control apparatus according to claim 2, wherein said deceleration calculating means includes means for calculating as said deceleration a ratio of said allowable feedrate difference setting to the feedrate difference between the blocks.

Claim 15

A numerical control apparatus according to claim 12, including means for excluding said calculated deceleration from control data for said control axis when said calculated deceleration is at least 1.

Claim 16

A numerical control apparatus according to claim 2, wherein said deceleration calculating means includes means for calculating as said deceleration a ratio of said allowable feedrate difference setting to an actual commanded feedrate difference produced by multiplying the feedrate difference between the blocks by an override percent.

Claim 17

A numerical control apparatus according to claim 2, wherein said apparatus is used in combination with a cutting machine tool.