JPS646933B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for controlling the temperature of a heating cylinder of an in-line injection molding machine.

[Prior art and its drawbacks]

In an in-line injection molding machine, the rotation of the screw installed in the heating cylinder allows the raw resin supplied from the hopper to be passed through the flow path, which is made up of the inner wall of the heating cylinder and the screw groove, by heat from an external heater and by the screw. The resin is configured to be melted and sent forward due to shear heat generation of the resin within the groove.

The heating cylinder temperature control is an external heating method that uses a thermocouple and a band heater.The entire area of the heating cylinder is divided into multiple control zones, and each control zone is controlled according to the set value of each temperature controller. ing. The resins used in injection molding machines have different thermal properties and require different heating cylinder temperature settings. Figure 2 shows a conventional example, which is divided into four sections: a nozzle temperature control area 11, a heating cylinder front temperature control area 12, a heating cylinder center temperature control area 13, and a heating cylinder rear temperature control area 14. , each region has thermocouples 15 to 18, respectively, and the temperature is controlled by a corresponding temperature regulator (not shown).

Today's injection molding machines require reliable color and resin changes, but during the molding operation after changing colors and resins, pigments used in the previous molding were found to have adhered to the inner wall of the heating cylinder and the screw. Phenomena were occurring where resin came out during injection and burnt resin got mixed into the molded product. This phenomenon was often observed in the following cases.

In other words, if the operation is stopped and the work is completed with the resin remaining in the heating cylinder at the end of the molding operation, the fixed residual resin must be melted before starting the molding operation for the next operation. No. For this reason, initially, the temperature controller was set to the molding temperature, the heater was turned on, and the molding operation was started after the residual resin had melted. In this case, as shown in FIG. 3, the heat from the band heater 19 is applied to the residual resin 21 via the heating cylinder 20, so much heat is applied to the residual resin portion that is in contact with the inner wall of the heating cylinder 20. It starts melting immediately, but the part that comes into contact with the screw 22 melts later. and,
By the time the part in contact with the screw melts, the residual resin part in contact with the inner wall of the cylinder receives excessive heat energy, causing discoloration, etc.
A phenomenon occurs in which pigments and the like adhere to the inner wall.

[Object of the present invention]

The present invention was made in order to eliminate the above-mentioned problems, and its purpose is to prevent the heating cylinder from burning due to residual resin when the heating cylinder and nozzle heat up. It is an object of the present invention to provide a method for preventing the occurrence of sticking to an inner wall.

[Summary of the invention]

In the present invention, when the heating cylinder and nozzle part heat up, the temperature of the heating cylinder and nozzle part is divided into a plurality of temperature intervals until the temperature reaches the molding temperature, and the heating cylinder and nozzle part are heated up in the first relatively low temperature division. After the part temperature reaches the maximum temperature in this temperature division section, it is controlled to maintain a thermal equilibrium state for a certain period of time, and after a certain period of time,
Move to a divided section with a temperature setting higher than the reached temperature, and after reaching the maximum temperature of this divided section, control is performed to maintain thermal equilibrium at the reached temperature for a certain period of time, and after a certain period of time, the temperature is set higher than the reached temperature. Repeat the control to move to a divided section with a higher temperature setting,
It is characterized in that the heat is gradually increased until the final molding temperature is reached.

[Embodiments of the invention]

The present invention will be explained below with reference to FIGS. 1 and 2 showing one embodiment. Conventional temperature control range 1
In addition to the temperature regulators 23 to 26 used for 1 to 14, there are provided temperature regulators 27 to 29 for slow heat-up, which are set at temperatures successively lower than these set temperatures. The temperature controllers 27 to 29 for slow heat up may be installed in any of the temperature control regions 11 to 14, but in this embodiment, the temperature controllers 27 to 29 for slow heat up can be connected to the thermocouples provided in the nozzle temperature control regions through the changeover switches 30, respectively. To explain the case where they are connected, the changeover switch 30 has the nozzle temperature regulator 23 and thermocouple 15, the front temperature regulator 24 and its thermocouple 16, and the center temperature regulator 25 and its thermocouple 17. , rear temperature regulator 26
In addition to opening and closing the thermocouple 18, the switching relay 31 of the step temperature increasing circuit 40 is also opened and closed.

The relay 31 has an A contact 31a and a B contact 31b.

Further, each of the temperature regulators 23 to 26 is connected to the electromagnetic switch 3 via the B contact 31b of the relay 31.
2 to 35 are connected. This electromagnetic switch 3
2 to 35 are A contacts 32a, 33a, 34, respectively.
a, 35a, a nozzle heater 36, a front heater 37, a center heater 38, and a rear heater 3.
9 opening and closing. 41 to 43 are a first step temperature start circuit, a second step temperature start circuit, and a third step temperature start circuit, and are timer relays 44 to 47, respectively.
has.

The timer relays 44 to 47 have A contacts 44a to 47a and B contacts 44b to 47b, respectively.

48 is a step temperature termination circuit, which is connected to the timer relay 4 in the third step temperature start circuit 43.
7 passes a predetermined time, its B contact 47b
is energized, and a relay 49 that issues an alarm such as a buzzer to switch to molding operation is activated.

Next, the operation will be explained. During normal molding, as shown in FIG.
7 to 29, and thermocouples 15 to 18 are connected to respective temperature regulators 23 to 26. At this time, since the relay 31 is not operating, the A contact 31a is open and each electromagnetic switch 32 to 35 is independent, and the B contact 31a is open.
b is closed and each electromagnetic switch 32 to 35 is connected to each temperature regulator 23 to 26, so each heater 36 to 39 shown in FIG.
are individually controlled and heated to a predetermined temperature. Note that the heater 36 is connected to the nozzle temperature control area 11.
The heater 37 is for the front temperature control area 14, the heater 38 is for the center temperature control area 13, and the heater 39 is for the rear temperature control area 12. When the heating cylinder and nozzle section of the injection molding machine heat up, when the changeover switch 30 is switched to slow heat up mode, the thermocouple 15 of the nozzle section
are connected to temperature regulators 27 to 29 for slow heat up, and are connected to thermocouples 15 to 18.
is open to each temperature regulator 23-26. At the same time, the relay 31 is turned on, the B contact 31b of the relay 31 is opened, and the electromagnetic switches 23 to 26 are opened, and the A contact 31a of the relay 31 is closed, and the electromagnetic switches 32 to 35 are connected in series. A contact 31a of relay 31 of circuit 41
closes, so the timer relay 45 operates,
Since the A contact 45a is closed, it is connected to the temperature regulator 27 for slow heat up. moreover,
When the timer relay 45 completes operation, the circuit 42
Since the A contact 45a of the timer relay 45 closes, the timer relay 46 is activated;
Since the A contact 46a of No. 6 is closed, it is connected to the temperature regulator 28 for slow heat up. moreover,
When the timer relay 46 completes operation, the B contact 4
6b (circuit 43) is closed, the timer relay 47 is activated, and the A contact 47a of the relay is closed, so the slow heat-up temperature regulator 29 is activated.
connected to. As a result, the heaters 36 to 39 are controlled by the slow heat-up temperature regulators 27 to 2.
9, the temperature is heated sequentially from the lowest temperature division to the highest, and a buzzer sounds when the final set temperature is stable.

For your reference, for safety reasons, ordinary injection molding machines are equipped with an interlock that prevents the screw from rotating while the residual resin remains unmelted. Since the screw rotation operation is not possible until several tens of minutes have elapsed since then, the molding operation can be started only after this interlock is released. Therefore, even if the set temperature is gradually increased to reach the required molding temperature at the final point, no problem will occur because the actual molding operation start time will not change.

〔Effect of the invention〕

As explained above, the temperature control device for the heating cylinder of an injection molding machine according to the present invention is provided with a slow heat-up circuit, so that the resin in the heating cylinder is not heated rapidly, and the burnt waste is removed during molding operation. It is now possible to obtain molded products of good quality with no contamination.

[Brief explanation of drawings]

FIG. 1 is a control circuit diagram for carrying out the method of the invention. 2 and 3 are explanatory diagrams of the conventional method, and FIG. 2 is an explanatory diagram of the heating cylinder section. FIG. 3 is an explanatory diagram of the material resin inside the heating cylinder. 15, 16, 17, 18...Thermocouple, 21-2
9... Temperature controller, 30... Changeover switch, 31
...Switching relay, 32-35...Electromagnetic switch,
36-39...Heater, 40-43...Temperature rising circuit.

Claims (1)

[Claims] 1 When the heating cylinder and nozzle part heat up, the temperature of the heating cylinder and nozzle part is divided into multiple temperature intervals until the temperature reaches the molding temperature, and the temperature of the heating cylinder and nozzle part is increased in the first relatively low temperature divided interval. However, after reaching the maximum temperature in the temperature division section, control is performed to maintain a thermal equilibrium state for a certain period of time, and after a certain period of time, the temperature is moved to a division section with a temperature setting higher than the reached temperature, and the temperature in the division section is increased. After reaching the maximum temperature, control is performed to maintain a thermal equilibrium state for a certain period of time, and after a certain period of time, control is repeated to move to a divided section with a temperature setting higher than the reached temperature, until the final molding temperature is reached. A method for controlling the temperature of the heating cylinder and nozzle of an injection molding machine, which gradually heats up until the temperature reaches the temperature.