JPH0548168B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Application Field) The present invention prevents the screw from rotating when the molten resin in the heating cylinder is not melted when starting the screw of an injection molding machine. This invention relates to an injection molding machine equipped with a screw start protection device that prevents screw breakage.

(Prior art) Conventionally, when starting the screw of an injection molding machine,
This is done after checking with a temperature controller on the control panel that the resin temperature inside the heating cylinder has reached, for example, 200°C or higher.

However, even if the temperature in the front zone or all zones of the heating cylinder reaches the set temperature, the resin in the portion of the heating cylinder attached to the screw may not yet be melted.

Therefore, after the temperature reaches the specified temperature indicated by the temperature controller, an additional 10
A screw activation protection circuit is built in that allows the screw to rotate and reciprocate after a safe temperature rise time of approximately 15 minutes has elapsed.

This circuit is composed of, for example, a sequence circuit shown in FIG. That is, the operation of the circuit is such that when the power to the heater circuit is turned on, the normally open contact of the temperature controller ATC of the circuit 26 closes, and the band heater 7
The ON-OFF electromagnetic contactor MH is excited, current flows through the heater 7 and heats the heating cylinder 6, and the normally open contact of the temperature controller ATC of the circuit 20 closes to excite the coil of the relay R1 and close the circuit. 21, it is self-maintained by the normally open contact of relay R1.

When the heating cylinder temperature rises and enters the proportional range of the set temperature of the temperature controller after about 35 to 40 minutes, the temperature controller ATC's a
The contact is turned OFF, turning off the heater 7 and closing the normally closed contact of the circuit 22, so that the timer T1 starts counting.

At this time, the normally open contact of timer T1 is closed, and timer T1 is self-held and continues counting.

When the set time (10 to 20 minutes) of timer T1 has elapsed, normally open contact T1a of timer T1 closes, and the coil of relay R2 connected to the starting circuit (not shown) of the motor that operates screw 9 is energized. (see circuit 23). Therefore relay R2 works,
Since the screw 9 is made operable, the screw 9 can be activated by operating a PB switch or the like provided in the motor starting circuit.

As a result, the screw is activated before the resin on the front end side of the screw is melted, and a twisting moment due to its rotational force is applied to the long screw shaft, thereby preventing fatigue and breakage of the screw.

(Problem to be Solved by the Invention) However, with the above method, even when restarting the screw when the heating cylinder temperature has dropped slightly, such as during lunch or during short-term maintenance, the temperature controller cannot be set. Once the temperature has been reached, the timer must be activated for 10 to 15 minutes before starting the screw and performing injection molding.

Therefore, in the injection molding process where the production volume per hour increases with the cost of the molded product, even though this is to prevent screw breakage, extra molding stop time is required, which leads to an increase in product costs. The dot was hot.

In order to solve these problems, an object of the present invention is to provide a circuit for preventing early screw activation, which activates the screw after a set time of a timer after the temperature has been raised to a predetermined temperature, and also to prevent the screw from restarting after a temporary stop of the injection molding machine. At startup, when the resin temperature in the heating cylinder is still within a predetermined range, the screw is protected through a screw operating circuit that rotates the screw faster, and the warm-up time of the injection molding machine is shortened to improve productivity. It's about trying.

(Means for solving the problem) In order to achieve the above object, the present invention raises the temperature of the heating tube to the set temperature of the temperature controller, and then repeats the on/off operation of the heater circuit at a predetermined period to maintain a constant temperature. Equipped with a temperature controller that controls the temperature within the proportional range of the temperature range,
The injection molding machine that makes the resin retachable in the heating cylinder is provided with a screw start protection device that starts the screw of the injection molding machine according to the temperature of the heating cylinder, and the screw start protection device is connected to the temperature control device. A self-holding circuit that keeps the contact connected to the heater circuit in the ON state, a delay timer that is activated by a signal output when the set temperature is reached, and a screw operation prohibition circuit that is set in advance after the operating time of the delay timer has elapsed. a first relay means that is turned on; and a bypass circuit that is connected from a circuit for operating the delay timer to the first relay means and that operates the screw without going through the delay timer. , a screw operating circuit including another timer that is turned on by the activation signal of the heater circuit, and a second relay means that disconnects the bypass circuit after the operating time of the other timer has elapsed; When the injection molding machine is restarted, when the heating cylinder temperature is within the lower limit of the proportional band temperature or slightly lower than that temperature, each of the delay timer line and the other timer line It is characterized in that the contacts are alternately turned on and off, while the bypass circuit is maintained in a conductive state, and the first relay means is energized and the screw operating circuit is turned on without waiting for the time-up of the delay timer. .

(Function) With the above configuration, if the temperature controller is turned off and restarted after the temperature of the heating cylinder has risen to the set temperature of the temperature controller, the temperature of the heating cylinder will not reach the set temperature. When the temperature is maintained in the proportional band or when the temperature is raised to the proportional band before the operation of other timers is completed, the other timers do not complete their operation and the R of the second relay means
3 is not excited, the delay timer bypass circuit is on. Therefore, R2 of the first relay means is energized, and the preset interlock of the screw activation inhibiting circuit is released, so that the screw activation circuit can be operated without using the delay timer of the early screw activation prevention circuit. Activate the screw early.

In addition, when the setting conditions are not the above, after the temperature of the heating cylinder rises to the set temperature of the temperature controller, it is kept warm for the time set by the delay timer, and after the resin near the screw in the heating cylinder is sufficiently melted, the screw is removed. Activate it.

This action corrects the difference between the temperature detected by the temperature control device and the actual resin temperature near the screw, and adjusts the temperature of the molten resin in the heating cylinder to eliminate unnecessary warm-up time and restart the screw. can be done quickly.

(Example) Embodiments of the present invention will be described based on the drawings.

In Fig. 1, the screw start protection device is a temperature control device (indicated by the symbol ATC) that raises the temperature of the heating cylinder 6 to the set temperature of the temperature controller 1 and controls the temperature within a proportional band that repeats ON/OFF at a predetermined cycle. ) connected to 2,
It is comprised of an early screw operation prevention circuit consisting of a screw operation delay circuit 3 and a screw start inhibition circuit 4, and a screw operation circuit 5.

The temperature control device 2 is composed of the same device as the conventional device, and a plurality of temperature controllers 1 are used to set the molding resin material fed from the hopper 10 into the heating cylinder 6 of the injection molding machine shown in FIG. It is heated to a certain temperature. Temperature controller 1 is usually installed at the front, middle, and rear of the heating cylinder 6.
Three heaters are provided corresponding to each heater 7 that heats each zone.

The temperature of the resin melted within the heating cylinder 6 is detected by a temperature sensor 8 (for example, a thermocouple TC) provided on the inner surface of the heating cylinder 6.
Temperature controller 2 that controls the temperature to the set temperature of each temperature controller 1
Temperature information is managed by

When the temperature controller 1 reaches the set temperature, it enters a proportional band that rises and falls within a predetermined temperature range relative to the set temperature, thereby stabilizing the temperature of the molten resin in the heating cylinder 6.

In this case, since the heating cylinder 6 is heated from the outside, the resin temperature near the surface of the screw 9 has a temperature distribution that is considerably lower than the resin temperature near the inner surface of the heating cylinder 6. That is, since the temperature controller 1 measures the resin temperature on the inner surface of the heating cylinder with the temperature sensor 8, the resin temperature on the surface of the screw 9 has not yet reached the set temperature of the temperature controller 2.

Therefore, the set temperature is maintained for about 10 to 20 minutes and the screw 9 is operated after waiting for the resin on the screw surface to melt.

The screw operation delay circuit 3 consists of the circuit shown in FIG.
It consists of ,, and ′, and the setting time is 10~
It consists of a timer T1 for about 20 minutes, a relay R1, R2 as a first relay means, and a plurality of contacts.

The screw operating circuit 5 is the circuit shown in FIG.
and a delay timer T connected between the circuit and
1, and includes a timer T2 with a set time of about 1 to 2 minutes, a relay R3 as a second relay means, and a plurality of contacts.

The screw start inhibiting circuit 4 is shown in the circuit of FIG. 1, and is composed of a normally open contact of a relay R2 and an electromagnetic contactor MC that excites the screw motor starting circuit.

Next, the operation of the above circuit will be explained.

In Fig. 1, when the heater circuit power is turned on when the temperature of the heating cylinder 6 is at room temperature, the temperature of the heating cylinder is lower than the set temperature of the temperature controller 1, so the normally open contact of the temperature controller ATC connected to the heater circuit is closed and the heater
Excite ON/OFF electromagnetic contactor MH, and heater 7
The heating cylinder 6 is heated by passing an electric current through it. At the same time, relay R1 is also energized and self-maintained.

On the other hand, the circuit's timer T2 has a set time of 1 to 2 minutes, and starts counting when the normally open contacts of the relay R1 and the temperature controller ATC close, and after the time is up, the circuit's timer T2 operates for a limited time. The normally open contact T2a of is closed to energize relay R3.

In the circuit, relay R3 is self-held by the normally open contact of relay R3, and the normally closed contact of relay R3 in the circuit is kept open.

When the temperature of the heating cylinder rises and enters the proportional range of the set temperature after about 35 to 40 minutes, the normally open contact of the ATC opens and turns off the heater 7, and the normally closed contact of the ATC closes and the delay timer T1 starts counting. At the same time, the normally open contact of timer T1 is closed in the circuit, and timer T1 is self-held and continues counting.

When the set time (10 to 20 minutes) of the timer T1 has elapsed, the normally open contact T1a of the circuit closes and the relay R2 is energized. In addition, by closing the normally open contact of relay R2 of the screw start inhibition circuit 4 in the circuit, the interlock that prohibits screw operation is released, so the motor start circuit that operates the screw is activated, causing the screw to rotate and advance. , retraction is possible and the forming process begins.

During this molding process, when the heater power is turned off during a lunch break or for a short period of time for inspection such as maintenance, the self-holding of relays R1, R2, and R3 is released.

When the power is turned on again, if the temperature of the heating cylinder is within the lower limit of the proportional band of the set temperature of temperature controller 1 or slightly below that temperature, the heating cylinder is maintained at a temperature that allows plasticization. .

In such a case, when the heater power is turned on, relay R1 of the circuit is energized, and the circuit is turned on.
The normally closed contact of the ATC and the normally open contact of the ATC in the circuit, if the temperature controller ATC is within the proportional band,
For example, ON/OFF operations are always repeated within a proportional period of 30 seconds.

In addition, even if the temperature is lower than the proportional band, if the temperature rises to the proportional band of the temperature controller ATC within the operating time range of timer T2 (1 to 2 minutes), the above
In the circuit by performing ON/OFF operation.
Since the normally open contact of ATC is opened, timer T2 returns to its original state and is no longer timed up.

Therefore, since relay R3 in the circuit is also not energized and not self-holding, the normally closed contact of relay R3 in the circuit continues to conduct, passing through the normally open contact of relay R1 in the circuit and the normally closed contact of ATC,
Relay R2 is energized without waiting for delay timer T1 (10 to 20 minutes) to complete the circuit.

Claims (1)

[Claims] 1. A temperature control device that raises the temperature of a heating cylinder to a set temperature of a temperature controller, and then repeats the on/off operation of a heater circuit at a predetermined period to control the temperature within a proportional band of a certain temperature range. In the injection molding machine that makes the resin traceable in the heating cylinder, there is provided a screw start protection device that starts the screw of the injection molding machine according to the temperature of the heating cylinder, and the screw start protection device is configured to control the temperature control. A self-holding circuit that maintains the ON state by a contact connecting the device and the heater circuit, a delay timer that is activated by a signal output when the set temperature is reached, and a preset screw operation prohibition after the delay timer's operating time has elapsed. a circuit for preventing early screw operation, including a first relay means for turning on the circuit; and a bypass circuit connected from the circuit for operating the delay timer to the first relay means and operating the screw without going through the delay timer. and,
The screw operating circuit includes another timer that is turned on by the activation signal of the heater circuit, and a second relay means that disconnects the bypass circuit after the operation time of the other timer has elapsed; When the injection molding machine is restarted, when the temperature of the heating cylinder is within the lower limit of the proportional band temperature or slightly lower than that temperature, the respective contacts of the delay timer line and the other timer line is turned on and off alternately, the bypass circuit is maintained in a conductive state during that time, and the first relay means is energized to turn on the screw operating circuit without waiting for the time-up of the delay timer. Injection molding machine with start-up protection device.