Injection molding control

Claim 2

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, a control system for selectively varying the velocity of said ram as it advances toward said mold as a function of the position of said ram, said control system comprising: drive means for advancing said ram; ram position signal generating means for generating signals corresponding to the position of said ram; a programmable electronic function generator controlled by signals from said ram position signal generating means for generating velocity command signals correlated with the position of said ram; a velocity feedback signal generator for generating ram velocity feedback signals corresponding to the velocity of said ram; a servoamplifier for energizing said drive means in accordance with said velocity command and velocity feedback signals; whereby the velocity of said ram is varied in a predetermined manner in accordance with ram position.

Claim 3

The apparatus of claim 1 further including: a sensor responsive to the pressure of material within said mold cavity; and means responsive to said mold cavity pressure sensor for rendering said servoamplifier ineffective to control said drive means when said mold cavity pressure reaches a predetermined cutoff pressure.

Claim 4

The apparatus of claim 2 further including: second means responsive to said mold cavity pressure sensor for applying a second predetermined hydraulic pressure on said ram when said mold cavity pressure reaches said predetermined cutoff pressure.

Claim 5

The apparatus of claim 1 in which said ram advances from a retracted shot position and in which the signals generated by the ram position generator are correlated with the displacement of the ram from said retracted shot position.

Claim 6

The apparatus of claim 4 including: means for varying said retracted shot position.

Claim 7

The apparatus of claim 1 further including: an offSet signal generator for additively modifying the velocity command signals from said function generator.

Claim 8

The apparatus of claim 1 further including: a range function generator for multiplicatively modifying the velocity command signals from said function generator.

Claim 9

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram; electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; means responsive to said mold cavity pressure sensor for actuating said electrically responsive valve means to reduce the pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure, whereby said mold cavity pressure is reduced to a holding pressure.

Claim 10

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram; electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; means responsive to said mold cavity pressure sensor for actuating said electrically responsive valve means to reduce the pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure, whereby said mold cavity pressure is reduced to a holding pressure.

Claim 11

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram; first electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; second electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; means responsive to said mold cavity pressure sensor for removing said first electrically responsive valve means from control of said hydraulic pressure fluid circuit means and for actuating said second electrically responsive valve means to establish a different pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure, whereby said mold cavity pressure is changed to a holding pressure.

Claim 12

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram; first electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; second electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; means responsive to said mold cavity pressure sensor for removing said first electrically responsive valve means from control of said hydraulic pressure fluid circuit means and for actuating said second electrically responsive valve means to establish a different pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure, whereby said mold cavity pressure is changed to a holding pressure.

Claim 13

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, said ram being reciprocated between a retracted shot position and a forwardmost position, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram, electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; first means responsive to said mold cavity pressure sensor for actuating said electrically responsive valve means to reduce the pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure; second means responsive to said mold cavity pressure sensor for comparing the position of said ram at the time when said mold cavity pressure reaches said predetermined cutoff pressure with a preselected reference position of said ram; means responsive to said comparison for controlling the retracted position of said ram during the next succeeding stroke of said ram.

Claim 14

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, said ram being reciprocated between a retracted shot position and a forwardmost position, a control system for said ram, said control system comprising: hydraulic pressure fluid circuit means for advancing said ram, electrically responsive valve means for controlling said hydraulic pressure fluid circuit means; a sensor responsive to the pressure of material within said mold cavity; first means responsive to said mold cavity pressure sensor for actuating said electrically responsive valve means to reduce the pressure on said hydraulic fluid circuit means when said mold cavity pressure reaches a predetermined cutoff pressure; second means responsive to said mold cavity pressure sensor for comparing the position of said ram at the time when said mold cavity pressure reaches said predetermined cutoff pressure with a preselected reference position of said ram; means responsive to said comparison for controlling the retracted position of said ram during the next succeeding stroke of said ram.

Claim 15

The control system of claim 10 further comprising: means for controlling the velocity of said ram at the time said mold cavity pressure reaches said predetermined cutoff pressure.

Claim 16

In an injection molding machine having a reciprocating screw ram which rotates and reciprocates between a retracted shot position at the beginning of an injection stroke and an advanced position at the end of an injection stroke, said ram injecting plasticized material into a mold cavity, a control system comprising: a position feedback signal generator for generating a position feedback signal correlated with the position of said ram; means for establishing a first reference signal corresponding to a selected advanced position; means for establishing a second rEference signal corresponding to a selected retracted shot position; means for initiating advancement of said screw ram when said screw ram is retracted to a position in which said position feedback signal corresponds to said second reference signal; a pressure feedback signal generator for providing a pressure feedback signal corresponding to the pressure of said material in said mold cavity; means for establishing a third reference signal corresponding to a given pressure; means for comparing said position feedback signal and said first reference signal when said pressure feedback signal corresponds to said third reference signal; and means for modifying said second reference signal in accordance with the results of said comparison.

Claim 17

In an injection molding machine having a reciprocating screw ram which rotates and reciprocates between a retracted shot position at the beginning of an injection stroke and an advanced position at the end of an injection stroke, said ram injecting plasticized material into a mold cavity, a control system comprising: a position feedback signal generator for generating a position feedback signal correlated with the position of said ram; means for establishing a first reference signal corresponding to a selected advanced position; means for establishing a second rEference signal corresponding to a selected retracted shot position; means for initiating advancement of said screw ram when said screw ram is retracted to a position in which said position feedback signal corresponds to said second reference signal; a pressure feedback signal generator for providing a pressure feedback signal corresponding to the pressure of said material in said mold cavity; means for establishing a third reference signal corresponding to a given pressure; means for comparing said position feedback signal and said first reference signal when said pressure feedback signal corresponds to said third reference signal; and means for modifying said second reference signal in accordance with the results of said comparison.

Claim 18

The apparatus of claim 12 further comprising: means responsive to said first and second reference signals to determine the total stroke of said ram; means for electrically dividing said total stroke into a plurality of segments; and means for controlling the velocity of said ram over each of said segments.

Claim 19

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, said ram being reciprocated between a retracted shot position and a forward position, a control system for selectively varying the velocity of said ram as it advances from said retracted shot position to said forward position as a function of the position of said ram, said control system comprising: drive means for advancing said ram; ram position signal generating means for generating signals correlated with the position of said ram; a programmable electronic function generator interconnected with said ram position generating means for generating velocity command signals correlated with the position of said ram; means for establishing electrical signals corresponding to the retracted shot and forward positions of the ram to thereby establish the stroke of said ram therebetween; said ram position signal generating means including means for automatically dividing the said ram stroke into a plurality of segments, and means generating a discrete signal for each segment; said programmable electronic function generator generating a separate preset velocity command signal for each signal from the ram signal generator; a velocity feedback signal generator for generating ram velocity feedback signals corresponding to the velocity of said ram; a servoamplifier for energizing said drive means in accordance with said velocity command and velocity feedback signals; whereby the velocity of said ram is varied in a predetermined manner during substantially the entire ram stroke as a function of ram displacement from the ram retracted shot position.

Claim 20

In an injection molding machine having a reciprocating ram for injecting plasticized material from an injection barrel into a mold cavity, said ram being reciprocated between a retracted shot position and a forward position, a control system for selectively varying the velocity of said ram as it advances from said retracted shot position to said forward position as a function of the position of said ram, said control system comprising: drive means for advancing said ram; ram position signal generating means for generating signals correlated with the position of said ram; a programmable electronic function generator interconnected with said ram position generating means for generating velocity command signals correlated with the position of said ram; means for establishing electrical signals corresponding to the retracted shot and forward positions of the ram to thereby establish the stroke of said ram therebetween; said ram position signal generating means including means for automatically dividing the said ram stroke into a plurality of segments, and means generating a discrete signal for each segment; said programmable electronic function generator generating a separate preset velocity command signal for each signal from the ram signal generator; a velocity feedback signal generator for generating ram velocity feedback signals corresponding to the velocity of said ram; a servoamplifier for energizing said drive means in accordance with said velocity command and velocity feedback signals; whereby the velocity of said ram is varied in a predetermined manner during substantially the entire ram stroke as a function of ram displacement from the ram retracted shot position.