JP2529412B2 - Injection molding machine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an inline screw type injection molding machine provided with an arithmetic and control unit composed of a microcomputer for integrally controlling the entire injection molding machine, and more particularly to a charge -Injection molding machine with improved monitoring accuracy during the weighing process.

[Prior Art] In recent years, injection molding machines have come to be controlled by a computer, and a microcomputer can refer to measurement information from various sensors based on a program and a set condition value created in advance. , For example, mold opening, eject,
Product removal process, mold closing / tightening process, injection / pressure holding process,
It is designed to control the charge and weighing process.
In addition, in some high-end models, the monitoring information that is set in advance is constantly monitored using the measurement information from the above-mentioned sensors installed in each part of the injection molding machine, and the molding conditions are determined to be acceptable. When it is out of the range, a so-called automatic monitoring function is provided so that a product (molded product) due to the shot is regarded as a defective product and taken out to a different place from the non-defective product.

By the way, the above-mentioned charge / metering process (the resin material is kneaded and plasticized by the rotation of the screw in the heating cylinder to feed the molten resin to the front side of the screw tip, and the molten resin is fed to the front side of the screw tip). While controlling the back pressure as it is stored, retract the screw,
As a monitoring item in the process of stopping the rotation of the screw when the molten resin stored on the front side of the screw reaches the amount of one shot), at present, the temperature of each part of the heating cylinder and the nozzle [° C ]. Or
Molten resin temperature [° C] stored at the tip of the screen.

Charge completion position [mm] based on the measurement information of the injection stroke sensor.

Charge time [sec] based on information from the timekeeping means.

Back pressure at the time of screen retreat [kg ・ f /
cm ² ].

Charge rotation speed [rpm] based on the measurement information of a screw rotation sensor consisting of a slit plate attached to the screw rotation shaft and a photo interrupter.

The above-mentioned back pressure and charge rotation speed are measured at the dividing position of the multi-divided area by dividing the retreat area of the screw into a plurality of areas.・ The weighing process conditions were carefully monitored.

[Problems to be Solved by the Invention] The details of the plasticizing / melting mechanism of the resin material in the in-line screw type injection molding machine have not yet been clarified at present, and each part of the screw (meter Ring zone, complexion zone,
The resin behavior in the feed zone) tends to change suddenly and fluidly.

As the one closely related to this resin behavior, the resin temperature in each part in the heating cylinder is first mentioned, but the above-mentioned monitoring item is to measure the temperature of the metal outer cylinder, and the actual resin It is hard to say that it accurately reflects the temperature. It suffices if the temperature of the molten resin stored at the tip of the screw can be measured, but for this purpose the sensor must be inserted in the molten resin passage, which is considerably complicated and expensive, and also causes stagnation in the resin flow. I also have concerns. Also, the monitoring items in and can be measured relatively accurately, but the charge completion position and charge time in and are monitoring items related to resin amount (measurement) and actual cycle time control. It is hard to say that it is closely related to the resin behavior in.

On the other hand, the back pressure and the rotational speed of the charge are closely related to the resistance (viscosity and density) of the resin and are considered to be monitoring items that greatly contribute to the monitoring of the resin behavior. These are set at each predetermined position. It is designed to be compared with operating condition values (monitoring set values). However, even with this back pressure and charge rotation speed, there is still a limit to accurately grasp the resin behavior that changes accidentally and fluidly and improve the monitoring accuracy during the charge / measurement process. It was pointed out.

The above items are provided to monitor the resin properties that change from moment to moment, but the back pressure is actually measured by the pressure of the hydraulic drive source such as the injection hydraulic cylinder. Since the resin pressure accumulated on the tip side of the screw is not actually measured,
There is a problem with measurement accuracy. In addition, the charge rotation speed is also calculated as the rotation speed is calculated by counting the number of pulses within a predetermined sampling time (for example, 0.5 sec) for each predetermined retract position of the screw. However, it was not possible to monitor the rotation condition continuously and continuously throughout the entire charge / weighing process.

Therefore, in order to improve the monitoring accuracy during the charge / weighing process, it is desirable to add another monitoring factor. Especially, the rotation state of the screw is continuous and continuous throughout the entire charge / weighing process. It was desired to add a significant monitoring item for monitoring.

The present invention has been made in view of the above points, and an object of the present invention is to provide an injection molding machine capable of more accurately monitoring a charge / measuring process.

[Means for Solving the Problems] In order to achieve the above-mentioned object, the present invention provides an in-line screw type injection molding machine equipped with an arithmetic and control unit including a microcomputer, wherein the arithmetic and control unit is a screw in a charge / measurement process. The cumulative amount of screw rotation from the start of rotation to the stop of rotation is cumulatively calculated, and the cumulative amount of screw rotation including at least the total screw rotation amount during the charge / measurement process is used as one of the monitoring items during the charge / measurement process. Composed.

[Operation] During the charge / measurement process, the arithmetic and control unit determines the temperature of each part, the charge complete position, the charge time, the back pressure at each measurement position, the charge rotation speed, and the rotation start time of the screw from the start time. The amount of screw rotation is cumulatively calculated, and this amount of screw rotation is also used as a monitoring item. This screw rotation amount can be easily measured and calculated by accumulating the number of pulses generated by the screw rotation sensor for detecting the charge rotation speed by the counter means, and the measurement accuracy is significantly higher than the above-described rotation speed measurement accuracy. improves. Furthermore, the amount of rotation of the screw is an extremely significant item for continuously monitoring the rotation state of the screw, since the rotation is continuously counted from the start of rotation of the screw (starting point of charge) without interruption. .

The amount of rotation of the screw is divided into a plurality of sections from the rotation start position of the screw (the charge start position, which usually coincides with the injection completion position of the screw) to the last position of the screw in the charge / weighing stroke. A set value is provided at each of the delimiter positions and the last retracted position, and the arithmetic and control unit determines whether or not the measurement data is within the set range at each position.

According to the experiments by the inventors, the total rotation amount of the screw in one cycle depends on the resin temperature, the retreat speed of the screw, the back pressure, etc., but if the same resin material is used, the resin temperature is high. It was confirmed that the lower the resin viscosity (resistance), the greater the total rotation amount of the screw, and the lower the resin temperature, the higher the resin viscosity (resistance) and the lower total rotation amount of the screw. It was also confirmed that when the backward speed of the screw was high, the total rotation amount of the screw was small, and when the backward speed was low, the total rotation amount of the screw was high. Furthermore, when the back pressure is high, the reverse speed is small and the total amount of rotation of the screw is large. When the back pressure is low, the reverse speed is large and the total amount of rotation of the screw is small. Was confirmed.

Therefore, the rotation amount of the screw is a factor that is effective for monitoring the kneading / plasticizing state of the resin, the degree of resin clogging (density), and the like. By comparing the rotation amount (cumulative number of pulses generated by the sensor) accurately counted at each backward position of the screen, the monitoring accuracy during the charge / measuring process is greatly improved.

[Embodiment] The present invention will be described below with reference to an embodiment shown in FIGS. 1 to 3.

 FIG. 1 is an explanatory view showing the outline of an injection molding machine.

In FIG. 1, reference numeral 1 denotes a base, and a plurality of tie bars 4 are disposed between a fixed die plate 2 and a support board 3 installed on the base 1, and the tie bar 4 is slidably movable. The die plate 5 is inserted. A mold clamping cylinder 6 is fixed to the support plate 3, and its piston rod 6a is connected to the movable die plate 5 via a toggle link mechanism 7. The movable die plate 5 is moved by the forward and backward movement of the piston rod 6a. It moves forward or backward with respect to the fixed die plate 2. Reference numeral 8 is a fixed-side mold attached to the fixed die plate 2, and 9 is a movable-side mold attached to the movable die plate 5.

Reference numeral 10 is a heating cylinder, 11 is a screw arranged in the heating cylinder 10 so as to be rotatable and forward / backward, 12 is a hopper for supplying a resin material, 13 is a motor for rotationally driving the screw 11, and 14 is It is an injection cylinder (hydraulic cylinder) that controls the forward / backward movement of the screw 11.

As is known, from the hopper 12 to the screen 11
The resin material supplied to the rear end is kneaded and plasticized by the rotation of the screw 11 and is transferred forward while being kneaded and plasticized. Retreats while controlling the back pressure, and the rotation of the screw 11 is stopped when the molten resin stored at the tip end side of the screw 11 reaches the amount of one shot. Then, the screw 11 is driven forward at the injection start timing after a lapse of a predetermined time, and the molten resin is injected into the cavity formed by the molds 8 and 9 in which the molds are closed (mold clamping). The pressure is maintained for a predetermined time. After that, the resin injected into the mold cools.
The mold is opened in the solidified state, and the product (molded product) is taken out by a take-out machine 15 or the like attached as necessary.

Reference numeral 20 denotes an injection stroke sensor including an encoder attached to a member which moves back and forth together with the screw 11, 21
Is a rotation sensor, 22 is an injection output sensor including a load cell attached to the injection cylinder 14, 23 is a mold opening / closing stroke sensor attached to the piston rod of the mold clamping cylinder 23, and 24 is attached to the mold. An eject detection sensor attached to an eject mechanism for pushing out a product, 25 is an unloader operation detection sensor attached to the unloader 15, 26 is a heating cylinder temperature sensor, and each of these sensors
20-26, and measurement information from other sensors not shown,
It is sent to an arithmetic and control unit, which will be described later, through an input conversion circuit as needed. The screen rotation sensor 21
Is composed of a slit disk that rotates in synchronization with the screw 11 and a photointerrupter (combination unit of a light emitting element and a light receiving element) that detects the slit. In this embodiment, detection of 50 pulses per rotation of the screw 11 It is designed to generate a signal. In addition, the temperature sensor 26
Is composed of thermocouples arranged in the respective parts of the heating cylinder 10 and nozzles, and only one temperature sensor 26 is shown for convenience of illustration, but there are actually a plurality of temperature sensors 26.

30 is an arithmetic and control unit mainly composed of a microcomputer that controls the entire injection molding machine, 31 is a key input device for inputting various commands to the arithmetic and control unit 30, and 32 is a processing result by the arithmetic and control unit 30 and A display device, such as a color CRT display, for displaying a display pattern created in advance, and 33 are printers for printing out the processing results by the arithmetic and control unit 30.

The arithmetic and control unit 30 includes an input processing unit 34 and an output processing unit 3
5, including a molding sequence control unit 36, a monitoring control unit 37, etc., to control the automatic operation and automatic monitoring operation of the injection molding machine, to display various display mode screens on the display device 32, or The printer 33 is made to print out desired data and the like. As described above, the arithmetic and control unit 30 is mainly composed of a microcomputer, and in reality, various I / O interfaces, ROM storing main programs and fixed data, measurement data and various flags, etc. It is equipped with a RAM for reading and writing, a clock, and an MPU that controls the overall control. The clock and main memory are backed up as needed. Then, the arithmetic and control unit 30 is adapted to control and execute automatic operation of the injection molding machine, monitoring operation and the like based on various programs created in advance.

That is, the molding sequence control unit 36 of the arithmetic and control unit 30, while taking in the output from each of the above-mentioned sensors from the input processing unit 34 based on the molding sequence control program created in advance and the setting condition value, and referring to the output. , For example,
Mold opening / ejection / product take-out process, mold closing / tightening process, injection / pressure holding process, charge / measuring process, etc. are controlled and executed, and output control signals sent from the output processing unit 35 to the driver circuit 38 are used. Then, the drive source of each part of the injection molding machine is controlled.

Further, the monitoring controller 37 of the arithmetic and control unit 30.
Is a set value (and upper and lower limit values) set in advance for each of a number of monitoring items based on a monitoring control program created in advance, and measurement by the respective sensors that have been taken in and converted through the input processing unit 34. In contrast to the data, if the measured data is out of the allowable range, it is regarded as a defective product and this fact is notified to the molding sequence control unit 36.
To recognize. Then, the molding sequence control unit 36, when receiving the defect occurrence signal from the monitoring control unit 37, at the time of the product removal process by the unloader 15, the product for which a failure is determined is different from the place where a non-defective product is placed. For example, it is designed to be transported to a scrap stacking place.

Here, the above-mentioned monitoring items correspond to a mold opening / eject / product take-out process, a mold closing / tightening process, an injection / pressure holding process, a charge / measuring process, and the like, and a plurality of monitoring items respectively. The set values and allowable ranges (upper and lower limits) for each monitoring item are set by case studies. The upper and lower limits of this monitoring item can also be set automatically.For details of this automatic setting method and the monitoring items during the injection / pressure-holding process, etc. See Japanese Patent Application No. 1-169993.

By the way, in this embodiment, the temperature [° C] of each part of the heating cylinder 10 and the nozzle by the temperature sensor 26 is a monitoring item in the charge / measurement process.

Charge completion position [mm] based on the measurement information of the injection stroke sensor 20. That is, as shown in FIG.
Distance to the last retracted position of the screw 11 (measurement end position) P _{4 based on} the most advanced position of the screw 11 (injection / pressure holding completion position) P ₀ .

Charge time (time from the start of charge to the end of measurement) [se by the timing means built in the arithmetic and control unit 30]
c].

Back pressure [kg · f / cm ² ] for each predetermined retracted position of the screw 11 based on the measurement information of the injection pressure sensor 22. That is, as shown in FIG. 2, the most advanced position of the screw 11
Back pressure at predetermined positions P _{1 to} P ₃ and at the last retracted position P ₄ from P ₀ to the last retracted position P ₄ of the screw 11.

Charge rotation speed (screen rotation speed) [rpm] for each predetermined retracted position of the screen 11, which is obtained by sampling the pulse generated by the screen rotation sensor 21 and converting the speed.
That is, the charge rotation speed at the positions P _{1 to} P ₄ in FIG.

A screw rotation amount [number of pulses] obtained by cumulatively calculating the pulses generated by the screw rotation sensor 21 from the start of screw rotation to each predetermined retract position of the screw. That is, from the start of rotation of the screw, each position P _{1 in} FIG.
~ Cumulative amount of rotation at P ₄ .

Has been adopted.

FIG. 3 shows an example of monitoring set values of the back pressure, the charge rotation speed, and the screw rotation (cumulative) amount among the above-mentioned monitoring items. The monitoring set value and the upper and lower limit values are obtained by performing case studies on the data at the time of molding the non-defective product, respectively, and
It is set / stored in a predetermined storage area within 30 and is set, for example, in consideration of the average value and variation range of data of 50 to 100 shots at the time of molding a good product. This setting work can be automatically set as in the above-mentioned prior application (Japanese Patent Application No. 1-169993), or the monitor item setting mode can be selected to display the key on the setting mode screen of the display device 32. It is also possible to set manually with the input device 31.

Then, the molding sequence control unit 36 of the arithmetic and control unit 30.
At the time of charge / weighing process in the actual cycle, it compares the set value (allowable range) with the measured data for each of the above-mentioned monitoring items to determine whether the measured (measured) data is outside the allowed range, and In this case, as described above, the product of the cycle is excluded as a defective product, and if necessary, all measurement data is temporarily stored in a predetermined recording area so that it can be printed out.

In the present embodiment, as described above, in addition to the other monitoring items that have been conventionally used during the charging / measuring process in the actual molding cycle, the retracted positions P _{1 to} P _{4 in} FIG. The amount of rotation of the screw at is cumulatively calculated as the number of pulses and used as a monitoring item. Since this screw rotation amount is simply counting pulses, the measurement precision is extremely high, and this can be realized by a simple counter means, and the rotation is seamlessly started from the screw rotation start time (charge start time). Since it counts, the rotation state of the screw can be continuously and continuously monitored. According to the experiments conducted by the inventors of the present application, by setting the screw rotation amount as a monitoring item during the charging / measuring process, uniform plasticization is achieved and high dimensional accuracy is required, for example, in optical plastic products. It was confirmed that the monitoring accuracy was significantly improved and defective products could be effectively extracted.

In addition, in the embodiment, the rotation amount of the screw is monitored at each of the retracted positions P _{1 to} P ₄ , but only the final retracted position P ₄ , that is, the total amount of screw rotation is sufficiently monitored. The accuracy can be improved.

[Effects of the Invention] As described above, according to the present invention, by adding the rotation amount of the screw from the rotation start time of the screw (charge start time) as a monitoring item,
It is possible to provide an injection molding machine which is significant for continuous monitoring of the screw rotation state in the measuring process and has high measurement accuracy and which enables more accurate monitoring. Its value is remarkable.

BRIEF DESCRIPTION OF THE DRAWINGS The drawings all relate to one embodiment of the present invention. FIG. 1 is an explanatory view showing the outline of an injection molding machine, and FIG. 2 is a measurement point such as a charge and a rotation amount during a measurement process. FIG. 3 is a table showing an example of monitoring items. 1 ... Base, 2 ... Fixed die plate, 3 ... Support board, 4 ... Tie bar, 5 ... Movable die plate, 6 ...
Mold clamping cylinder, 6a ... Piston rod, 7 ... Toggle link mechanism, 8 ... Fixed side mold, 9 ... Movable side mold, 10 ...
… Heating cylinder, 11 …… Screen, 12 …… Hopper,
13 …… Motor, 14 …… Injection cylinder, 15 …… Unloader, 20
…… Injection stroke sensor, 21 …… Screw rotation sensor, 22 …… Injection pressure sensor, 23 …… Mold opening / closing stroke sensor, 24 …… Eject detection sensor, 25 …… Unloader operation detection sensor, 26 …… Temperature sensor, 30 ... Arithmetic control device,
31 …… Key input device, 32 …… Display device, 33 …… Printer, 34 …… Input processing unit, 35 …… Output processing unit, 36 …… Molding sequence control unit, 37 …… Monitoring control unit.

Claims (1)

(57) [Claims] 1. An arithmetic and control unit provided in an injection molding machine,
In the injection molding machine, which determines whether or not the measurement data corresponding to each preset monitoring item is within the allowable range from the measurement information of the sensors arranged in each part of the injection molding machine, the arithmetic control device is The cumulative screw rotation amount including at least the total screw rotation amount in the charge / measurement process is calculated by cumulatively calculating the screw rotation amount from the rotation start to the rotation stop of the screw in the charge / measurement process. An injection molding machine characterized by being used as one of the above.