The present invention relates to readily programmable automatic control of plastic flow through two (or more) separate injection nozzles to the cavities of separate mold inserts which are readily removable from and insertable into a mold housing of an injection molding machine. More particularly the invention relates to a system and method for programming proportional control of plastic flow injection through a nozzle into the cavity of any modular mold insert having any desired cavity configuration and volume different from the cavity configuration/volume of a first modular mold insert which it replaces. Normally, in injection mold apparati/processes, the pressure, flow rate, temperature and other parameters of the polymer fluid(s) and operating parameters of components of the injection mold machine itself, are preselected and fixed throughout an injection mold machine operating cycle according to the size, configuration and volume of the cavity of the mold into which the plastic fluid is to be injected. Such prior systems do not enable the user to vary, control or tailor the fluid flow rate or stop/start of the system with respect to any desired mold cavity configuration/size.
The present invention provides injection control over two or more modular molds (mold inserts) which are readily removable/changeable/variable and which have different sizes, shapes, volumes or configurations, the injection for which can be independently customized for maximum end product (part) and injection quality, speed of part production and the like using a single existing size and configuration of injection machine screw/barrel, hotrunner(s), manifold(s), actuators, nozzles, valve pins, rotary valves, plungers, shooting pots and the like, the operation of which are readily programmably controllable and can be operationally programmed for maximum performance with respect to each mold insert having any selected part or cavity configuration, size, shape or volume.
In accordance with the invention therefore, there is a provided a system, apparatus and method for selectively and readily controlling the injection flow into the cavities of modular injection mold inserts which are readily replaceable with inserts having different cavities of different size, shape, configuration, volume and the like.
More particularly there is provided, in an injection molding machine, an apparatus for controlling delivery of a fluid material to mold cavities of selectively variable size or configuration, the apparatus comprising:
A modular mold mounting mechanism having mounting apertures for receiving first and second molds having first and second mold cavities of different size or configuration, the mounting apertures being adapted for ready insertion and ready removal of the first and second molds;
A manifold into which fluid material is injected, the manifold having first and second fluid delivery channels through which the fluid material is injected, one channel having an exit aperture communicating with a gate to the cavity of one mold, the other channel having an exit aperture communicating with a gate to the cavity of the other mold;
Each channel being associated with a drive mechanism which is interconnected to and controls operation of a fluid flow controller which varies flow of the fluid material through an associated channel,
A sensor for sensing a selected condition of the fluid material being injected through at least one of the channels or at least one of the mold cavities;
A controller interconnected to each drive mechanism, the controller comprising a computer interconnected to a sensor which receives a signal representative of the selected condition sensed by the sensor, the computer including an algorithm utilizing a value corresponding to a signal received from the sensor as a variable for controlling operation of at least the drive mechanism associated with the at least one channel.
Most preferably the modular mold housing comprises first and second housings readily openable and closeable for enabling ready insertion and removal of the first and second molds.
Typically the apparatus includes a second sensor for sensing a selected condition of the fluid material being injected through the other channel or the other mold cavity, the computer being interconnected to the second sensor and receiving a signal representative of the selected condition sensed by the second sensor, the algorithm utilizing a value corresponding to a signal received from the second sensor as a variable for controlling operation of the drive mechanism associated with the other channel.
Typically, at least one of the channels includes a nozzle having a seal surface surrounding the exit aperture of the channel, the nozzle being expandable upon heating to a predetermined operating temperature, the nozzle being mounted relative to a complementary surface surrounding the gate such that the seal surface of the nozzle is moved into compressed contact with the complementary surface surrounding the gate upon heating of the nozzle to the predetermined operating temperature. At least one of the channels preferably includes a nozzle comprising an outer unitary piece formed of a first material and an inner unitary piece formed of a second material, the first material being substantially less heat conductive than the second material.
The sensor may comprise a pressure transducer interconnected to at least one of the channels or a mold cavity for detecting the pressure of the fluid material. The actuator controller may include a solenoid interconnected to the computer, the solenoid having at least two chambers and a piston controllably movable between selected positions for selectively delivering a pressurized actuator drive fluid to one or the other of the chambers of the actuator.
In one embodiment, at least one channel includes a valve pin interconnected to the actuator controller, the valve pin having a surface for forming a gap with a complementary surface of the at least one channel spaced upstream and away from the gate, the size of the gap being controllably variable to control flow of the fluid material through the gate. The valve pin is reciprocally movable toward and away from the gate and wherein the surface of the valve pin and the surface of the channel are adapted to increase the size of gap as the valve pin is moved away from the gate and decrease the size of the gap as the valve pin is moved toward the gate.
The apparatus may include a plug mounted in a recess of the manifold, the plug having a bore through which a stem of the valve pin passes, the valve pin having a head, the bore of the plug through which the stem passes having a smaller diameter than the valve pin head at the valve pin head""s largest point and the recess of the manifold having a larger diameter than the diameter of the valve pin head at the valve pin head""s largest point, so that the valve pin can be removed from the manifold from a side of the manifold in which the recess is formed when the plug is removed from the manifold.
The sensor may be selected from the group consisting of a pressure transducer, a load cell, a valve pin position sensor, a temperature sensor and a barrel screw position sensor.
The fluid flow controller is preferably disposed within or communicates with the flow of fluid material through the manifold or one or more of the channels and is typically selected from the group consisting of a valve pin, a rotary valve and a plunger.
Further in accordance with the invention there is provided, in an injection molding system including a manifold having first and second channels to direct fluid material into respective first and second modular cavity inserts each modular cavity insert having respective first and second cavity volumes and shapes, the modular cavity inserts being readily removably mounted in respective first and second receiving apertures in a mold, a method of injection molding comprising the steps of:
(A) independently controlling first and second rates at which fluid material is injected respectively through the first and second channels or into the first and second modular cavity inserts;
(B) readily removing the second modular cavity insert from the second receiving aperture in the mold and readily inserting a third modular cavity insert into the second receiving aperture, the third modular cavity insert having a volume or shape different from the volume or shape of the second modular cavity insert; and
(C) after step (B), independently controlling the first and a selected third rate at which the fluid material is injected respectively into the first and third modular cavity inserts, the selected third rate being different from the first rate.
The method preferably further comprises:
selecting an automatically executable algorithm which utilizes as variables first and second values corresponding to first and second respective signals received from respective first and second sensors of respective first and second conditions of the fluid material injected through or into respective ones of the first and second channels or the first and third modular cavity inserts;
wherein the algorithm includes programmable instructions for directing the rates of flow of the first and third flow rates; and,
executing the algorithm automatically with a computer after the third modular cavity insert is inserted into the second receiving aperture.
The flow controller of the apparatus typically comprises a pin which is controllably slidable via interconnection to an actuator along a reciprocal path of movement within the bore of a nozzle, or the controller may comprise a rotary valve having a rotatable flow channel connecting an input flow channel to the exit aperture of at least one of the nozzles, the rotatable channel being interconnected to the actuator and controllably rotatable via the actuator to selectively vary the rate of flow of plastic melt through the rotatable flow channel to the exit aperture according to the degree of rotation of the rotary valve. The rotary valve typically comprises a cylinder rotatably mounted within a housing the cylinder having a bore rotatably communicable with a pair of bores in the housing.
The flow controller may alternatively comprise a ram or plunger driven by an actuator as described herein. In such embodiments, the ram or plunger may be disposed within a channel within the manifold or within a well or chamber within the manifold which communicates with a channel within the manifold.
In an embodiment, one or more of the actuators comprises a piston mounted within a fluid sealed housing, the piston having a stem extending outside the fluid sealed housing, the valve pin having a head wherein the stem is readily detachably interconnected to the head of the valve pin outside the fluid sealed housing.
In another embodiment, one or more actuators comprises an electrically driven motor, the motor being mechanically interconnected to either a valve pin disposed in a bore of one of the nozzles such that the valve pin is reciprocally drivable within the bore of the nozzle by the motor, or a rotary valve for rotatable drive of a rotatable component having a fluid flow bore, or a ram or plunger, the motor being electrically interconnected to the algorithm, the algorithm controlling the drive of the motor.
Each actuator for each of the first and second nozzles may be fluid driven wherein each actuator is commonly supplied with an actuator drive fluid flowing through a manifold which commonly delivers fluid to each of the nozzles.
The actuator controller for a fluid driven actuator typically comprises a solenoid having a position controllably movable between selected positions for selectively delivering a pressurized actuator drive fluid to one or the other of at least two chambers of the actuator.
The actuator controller for a fluid driven actuator may include a drive fluid valve which receives pressurized drive fluid from a source, the drive fluid valve leaving one or more fluid ports sealably communicating with one or more complementary fluid drive chambers disposed within the fluid driven actuator, the drive fluid valve being controllably driven to selectively distribute received pressurized fluid through the one or more fluid ports to the one or more complementary fluid drive chambers of the actuator. The drive fluid valve typically comprises a sealed housing and a plunger movable within the sealed housing to positions along a path wherein the one or more fluid ports are open to communication, partially open to communication, or closed from communication with the one or complementary fluid drive chambers by the plunger, the plunger being controllably movable to any position along the path between the open and closed positions such that flow of the drive fluid to drive fluid chamber is controllably variable to a selected rate. The plunger typically comprises a slidably movable rod having interference projections which are selectively slidable by movement of the rod over the fluid ports to open, partially open to any desired degree, or close the fluid ports.
In another embodiment, at least one gate of a mold may be an edge gate extending radially outward through a mold cavity plate, at least one of the nozzles having a bore having a first portion having an inlet for the plastic melt which is not in alignment with the edge gate and a second portion extending radially outward from the first portion terminating in the exit aperture being in alignment with the edge gate. In such an embodiment the nozzle may have an exit end comprising a center nozzle member and a circumferential nozzle member surrounding the center nozzle member, the exit aperture extending through the center nozzle member in alignment with one of the gates, the circumferential nozzle member surrounding the one gate, wherein a groove is formed between the circumferential nozzle member and the center portion.
The apparatus typically includes a plurality of enclosed heat conductive tubes containing a fluid which vaporizes and condenses within each tube and a wick disposed within and along the length of each tube, at least one of the manifold and one of the nozzles having the tubes embedded within the manifold or the nozzle making heat conductive contact with the manifold or the nozzle.
The apparatus may include a melt flow reservoir sealably communicating with and disposed between a common feed channel of the manifold and an exit aperture of a nozzle, the reservoir having a defined volume sealably fillable and closed off from communication with the common feed channel, the reservoir including an injection mechanism such as a ram or plunger operable on melt material residing in the reservoir to force the melt material through the exit aperture of the nozzle under pressure. In such an embodiment, the melt flow controller preferably comprises a valve disposed in the melt flow between the reservoir and the exit aperture of the nozzle.
The melt flow controller may also alternatively comprise the injection mechanism itself such as a ram or plunger the actuator for which is controlled by the actuator controller to control the flow directly via the ram or plunger without an intermediate valve between the ram/plunger and the exit aperture of the channel (e.g. ram/plunger/cylinder 565, FIG. 31, without the intermediate valve 512).
The sensor typically comprises a pressure transducer interconnected to or communication with at least one of the bore of a nozzle or a mold cavity or elsewhere within the flow channel upstream of the bore of the nozzle for detecting the pressure of the melt material. The sensor may alternatively comprise a mechanism selected from the group consisting of a pressure transducer, a load cell, a valve pin position sensor, a temperature sensor and a barrel screw position sensor.