Automatic servomotor control for lathes providing sfm and chip thickness control

Claim 2

An SFM control for automatically controlled lathes including feed supply means for automatically feeding a part being machined relative to a cutter tool of the lathe along at least one axis of movement, spindle motor speed control means for controlling the spindle speed of the lathe, and change-in-radius speed control means for deriving a speed control signal related to the change in radius of a part being machined on the automatically controlled lathe, the output speed control signal from said change-in-radius speed control means being supplied to control the spindle speed control means whereby the spindle speed of the lathe is adjusted automatically with changes in radius of a part being machined to maintain a desired value of surface feet per minute moving past the lathe cutter tool, said spindle motor speed control means including an operational amplifier, and means for changing the gain of said operational amplifier in accordance with the change in radius of a part being machined on the automatically controlled lathe whereby the output signals from the operational amplifier automatically are corrected to maintain a desired value of surface feet per minute moving past the lathe cutter tool tip as the part being Machined changes in radius.

Claim 3

An SFM control for automatically controlled lathes according to claim 1 additionally including gear range selector means for selectively changing the gain of the operational amplifier in accordance with a predetermined selected one of a plurality of speed range changing gear ratios of a selectively changeable gear train employed to drive the lathe spindle.

Claim 4

An SFM control for an automatically controlled lathe according to claim 2 wherein the gain of said operational amplifier varies inversely with the radius of a part being machined and inversely with the ratio of spindle speed to spindle motor speed as determined by said selected gear ratio.

Claim 5

An SFM-RPM control for lathes according to claim 3 further including spindle speed mode select means for selectively disconnecting the change-in-radius speed control means for controlling the operational amplifier, and means for connecting RPM speed control means to control the gain of the operational amplifier whereby the spindle speed of the lathe selectively may be operated in a desired value of surface feet per minute mode or in a desired value of revolutions per minute mode at pre-programmed command speeds.

Claim 6

An SFM-RPM-chip thickness control for lathes according to claim 4 further including means coupled to the lathe spindle for deriving a spindle speed indicating control signal representative of the spindle speed of the lathe, and means responsive to the spindle speed indicating control signal for slaving the feed supply means to the lathe spindle speed so that the feed rate and hence chip removal is proportional to the spindle speed and a controlled thickness of chip removal is achieved.

Claim 7

An SFM-RPM-chip thickness control for automatically controlled lathes according to claim 5 further including means coupled to said spindle motor speed control means for controlling the operation thereof selectively either in pre-programmed command values of surface feet per minute of the part being machined moving past the cutter tool tip, or selectively in accordance with preprogrammed values of revolutions per minute of the lathe spindle.

Claim 8

An SFM control for automatically controlled lathes including feed rate control servo drive means for automatically controlling the feed rate operation of the lathe along at least one axis of movement in accordance with a set of pre-programmed instructions, a spindle motor, spindle motor speed control means for controlling the spindle speed of the lathe, a selectable ratio gear train driven by the spindle motor, said gear train driving the lathe spindle and change-in-radius speed control means for deriving a speed control signal related to the change in radius of a part being machined on the automatically controlled lathe, said spindle motor speed control means including an operational amplifier and means for changing the gain of said operational amplifier, said gain changing means being responsive to said speed control signal so that the gain of said operational amplifier varies inversely with the radius of the part being machined and inversely with the ratio of spindle speed to spindle motor speed as determined by said selected gear ratio, whereby the spindle speed of the lathe is adjusted automatically with changes in radius of a part being machined to maintain a desired value of surface feed per minute moving past the lathe cutter tool independently of the operation of the feed rate control servo drive means.

Claim 9

An SFM control for automatically controlled lathes including feed rate control servo drive means for automatically controlling the feed rate operation of the lathe along at least one axis of movement in accordance with a set of pre-programmed instructions, a spindle motor, spindle motor speed control means for controlling the spindle speed of the lathe, a selectable ratio gear train driven by the spindle motor, said gear train driving the lathe spindle and change-in-radius speed control means for deriving a speed control signal related to the change in radius of a part being machined on the automatically controlled lathe, said spindle motor speed control means including an operational amplifier and means for changing the gain of said operational amplifier, said gain changing means being responsive to said speed control signal so that the gain of said operational amplifier varies inversely with the radius of the part being machined and inversely with the ratio of spindle speed to spindle motor speed as determined by said selected gear ratio, whereby the spindle speed of the lathe is adjusted automatically with changes in radius of a part being machined to maintain a desired value of surface feed per minute moving past the lathe cutter tool independently of the operation of the feed rate control servo drive means.

Claim 10

An SFM-RPM control for lathes according to claim 7 further including spindle speed mode select means for selectively disconnecting the change-in-radius speed control means for controlling the operation of the operational amplifier, and means for connecting in RPM speed control means to control the gain of the operational amplifier whereby the spindle speed of the lathe selectively may be operated in a desired value of surface feet per minute mode or in a desired value of revolutions per minute mode at pre-progrAmmed command speeds.

Claim 11

An SFM-RPM-chip thickness control for lathes according to claim 8 further including means coupled to the lathe spindle for deriving a spindle speed indicating control signal representative of the spindle speed of the lathe, and means responsive to the spindle speed indicating control signal for slaving the feed rate control servo drive means to the spindle speed so that the feed rate is proportional to the spindle speed and a controlled thickness of chip removal is achieved.

Claim 12

An SFM-RPM-chip thickness control for automatically controlled lathes according to claim 9 further including means coupled to said spindle motor speed control means for controlling the operation thereof selectively either in pre-programmed command values of surface feet per minute to be maintained past the cutter tool tip, or selectively in accordance with pre-programmed values of revolutions per minute of the lathe spindle.

Claim 13

An SFM-RPM-chip thickness control according to claim 10 wherein the feed rate control servo drive means automatically controls the feed rate operation of the lathe along at least two mutually perpendicular axes of movement in accordance with a set of pre-programmed instructions.

Claim 14

An improved SFM digital numerical control for automatically controlled lathes including command data input means and digitally operable numerical controlled feed rate servo drive means for automatically controlling the feed rate operation of a lathe along at least one axis of movement in accordance with a set of pre-programmed instructions supplied from the command data input means, motor speed control means for controlling the spindle speed of a lathe and including variable gain amplifying means for amplifying a spindle speed controlling signal used to control the speed of the spindle drive motor, and change-in-radius speed control means for deriving a speed control signal related to the change in radius of a part being machined on an automatically controlled lathe, said change-in-radius speed control means comprising radius counter means supplied with an input initial radius value from the command data input of the numerical control and with a change-in-radius input signal from the numerically controlled feed rate servo drive means, and means coupling the output from the radius counter means to the variable gain amplifying means for controllably varying the gain of the variable gain amplifying means in response to changes in radius of the part being machined whereby the spindle speed of the lathe is adjusted automatically to maintain a desired value of surface feet per minute past the lathe cutter tool.

Claim 15

An improved SFM digital numerical control for automatically controlled lathes including command data input means and digitally operable numerical controlled feed rate servo drive means for automatically controlling the feed rate operation of a lathe along at least one axis of movement in accordance with a set of pre-programmed instructions supplied from the command data input means, motor speed control means for controlling the spindle speed of a lathe and including variable gain amplifying means for amplifying a spindle speed controlling signal used to control the speed of the spindle drive motor, and change-in-radius speed control means for deriving a speed control signal related to the change in radius of a part being machined on an automatically controlled lathe, said change-in-radius speed control means comprising radius counter means supplied with an input initial radius value from the command data input of the numerical control and with a change-in-radius input signal from the numerically controlled feed rate servo drive means, and means coupling the output from the radius counter means to the variable gain amplifying means for controllably varying the gain of the variable gain amplifying means in response to changes in radius of the part being machined whereby the spindle speed of the lathe is adjusted automatically to maintain a desired value of surface feet per minute past the lathe cutter tool.

Claim 16

An improved SFM digital numerical control according to claim 12 wherein the variable gain amplifying means includes a plurality of selectively operable digital to analog converter means connected in a feedback path for adjustably controlling the gain of the amplifier, and the radius counter means selectively control the digital to analog converter means in accordance with the value of the radius recorded in the counter.

Claim 17

An improved SFM-RPM control for lathes according to claim 13 further including spindle speed mode selector means for selectively disconnecting the radius counter means and associated digital to analog converter means connected in the feedback path of the variable gain amplifying means, and means for connecting in a fixed gain RPM speed control means in the feedback path of the variable gain amplifying means whereby the spindle speed of the lathe selectively may be operated in a desired value of surface feet per minute mode or in a desired value of revolutions per minute mode at pre-programmed command speeds.

Claim 18

An SFM-chip thickness control for lathes according to claim 12 further including digital encoding means coupled to the lathe spindle for deriving a spindle speed indicating digitized pulse train representative of the spindle speed of the lathe, and means for supplying the spindle speed pulse train thus derived To the digitally operable numerical controlled feed rate servo drive means as an input supply pulse train whereby the operation of the numerically controlled feed rate servo drive means is slaved to the spindle speed of the lathe for automatically controlling the feed rate operation of the lathe relative to the lathe spindle speed through the spindle speed pulse train whereby the feed rate can be made to be proportional to the spindle speed, and a controlled thickness of chip removal can be achieved.

Claim 19

An SFM-RPM-chip thickness control for lathes according to claim 14 further including digital encoding means coupled to the lathe spindle for deriving a spindle speed indicating digitized pulse train representative of the spindle speed of the lathe, and means for supplying the spindle speed pulse train thus derived to digitally operable numerical controlled feed rate servo drive means as an input command pulse train whereby the operation of the numerically controlled feed rate servo drive means is slaved to the spindle speed of the lathe for automatically controlling the feed rate operation of the lathe relative to the lathe spindle speed through the spindle speed pulse train whereby the feed rate can be made to be proportional to the spindle speed, and a controlled thickness of chip removal can be achieved.

Claim 20

An SFM digital numerical control according to claim 12 further including spindle speed command counter means adapted to derive an output command spindle speed pulse train and designed to be programmed in terms of command values of surface feet per minute of the part being machined moving past the lathe cutter tool, and digital to analog converter means having the output command spindle speed pulse train from the spindle speed command counter means supplied thereto and having its output supplying the variable gain amplifying means with a command spindle speed analog control signal that is proportional to the input command spindle speed pulse train supplied from the spindle speed command counter means.

Claim 21

An SFM-chip thickness digital numerical control according to claim 15 further including spindle speed command counter means adapted to derive an output command spindle speed pulse train and designed to be programmed in terms of command value of surface feet per minute of the part being machined moving past the lathe cutter tool, and digital to analog converter means having the output command spindle speed pulse train from the spindle speed command counter means supplied thereto and having its output supplying the variable gain amplifying means with a command spindle speed analog control signal that is proportional to the input command spindle speed pulse train supplied from the spindle speed command counter means.

Claim 22

An SFM-RPM-chip thickness control according to claim 16 further including spindle speed command counter means selectively operable to derive an output command spindle speed pulse train calibrated either in terms of surface feet per minute or in terms of revolutions per minute, digital to analog converter means having the output from the spindle speed command counter means supplied thereto for deriving an output analog spindle speed command signal proportional to the command spindle speed pulse train supplied from the spindle speed command counter means, and having the output thereof supplied to the input of the variable gain amplifying means for deriving a spindle speed motor controlling signal measured either in terms of a desired command value of surface feet per minute or in terms of a desired command value of revolutions per minute.

Claim 23

An SFM-RPM-chip thickness control according to claim 19 wherein the digital to analog converter means connected intermediate the output of the spindle speed command counter means and the input to the variable gain amplifying means comprises a plurality of digital to analog converter means selectively connected in circuit relationship in accordance with a desired speed range changing gear ratio.

Claim 24

An SFM-RPM-chip thickness control according to claim 20 wherein the numerically controlled feed rate servo drive means automatically controls the feed rate operation of the lathe along at least two mutually perpendicular axes of movement in accordance with a set of pre-programmed instructions supplied from the command data input means.