JPH01176538A - Method and apparatus for controlling temperature of mold in plastic injection molding machine - Google Patents

Abstract

PURPOSE:To prevent the generation of the irregularity of a molded product at the start time of molding or the generation of rust on a mold caused by dew condensation at the stop time of molding, by receiving the electric signal corresponding to an operation mode from a sequence controller by a temp. regulator to change the temp. set value of a liquid medium. CONSTITUTION:A pump 7 for recirculating a recirculation liquid medium 9 to the piping jackets 4a, 4b provided to fixed and movable molds 1, 2 and a heating/cooling tank 8, and a temp. regulator 17a for controlling a cooling electromotive control valve 11 for regulating the cooling quantity of the heating/cooling tank 8 and a heating electromotive control valve 14 for regulating heating quantity on the basis of output electric signals 18a, 19a are provided. The temp. set value TS of the liquid medium 9 of the temp. regulator 17a changes corresponding to the operation mode of an injection molding machine by the output signals 21, 22 of a sequence control apparatus 20 and, during the stoppage of the injection molding machine, the temp. TM of the molds 1, 2 is held to the preset corresponding temp. TM1 of the molds 1, 2 during the operation of the injection molding machine and, at the start time of the operation of the injection molding machine, the temp. set value TS of the liquid medium 9 is continuously changed in a gradient state (TS1 TS2) so as to be well-balanced with the quantity of heat applied from a molten molding material.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method and apparatus for controlling the temperature of a mold in a plastic injection molding machine.

[Conventional technology]

FIG. 5 shows a block diagram of a method for controlling mold temperature in a conventional plastic injection molding machine.

This will be briefly explained below.

In the figure, 1 is a fixed mold, 2 is a movable mold, 3 is a plastic molded product obtained by the above mold 1.2 and an injection molding machine (not shown), and 4a and 4b are provided in the mold. Piping jacket for temperature control, 5 is the inlet side piping,
6 is the return side piping, 7 is the pump, 8 is the heating and cooling tank, 9
10 is a frozen water generator, 11 is an electric control valve for cooling to adjust the amount of frozen water, 12 is a frozen water pipe, and 13 is a heating steam 14 is a steam electric control valve that adjusts the amount of steam; 15 is a heating steam pipe; 16 is a thermometer that detects the temperature of the medium liquid discharged from the pump 7; 17 is a temperature controller; 18 is a temperature controller 17 is a control output electric signal for cold water, and 19 is a control output electric signal for steam from the temperature controller 17.

The operation of the conventional system shown in FIG. 5 will be briefly described below.

In FIG. 5, the circulating medium liquid 9, which has been adjusted to a predetermined temperature by the heating and cooling tank 8, is discharged by the pump 7.
Infeed piping 5, piping jacket 4a processed into mold
, 4b, and returns to the heating and cooling tank 8 through the return side piping 6 in a closed circulation, thereby controlling the temperatures of the fixed mold 1 and the movable mold 2. In this system, temperature controller 17
is a temperature measuring element 1 that detects the temperature of the medium liquid at the discharge port of the pump 7.
In order to make the temperature of the circulating medium liquid 9 the same as the temperature setting value, the control output electricity for cooling is determined based on the medium liquid temperature detected by the temperature controller 6 and a preset temperature value (not shown) of the temperature controller 17. Signal 18 or regulating output electrical signal 1 for steam
9 is generated and sent to the electric cooling control valve 11 or the steam electric control valve 14. Thereby, the circulating medium liquid 9 in the heating/cooling tank 8 is cooled or heated by the frozen water from the frozen water generator 10 or the steam from the heating steam generator 13, and the circulating medium liquid flows in the feed-side pipe 5. The temperature t1 is controlled to be constant as shown in the sixth diagram.

To summarize what has been said above, fixed mold 1. Movable mold 2
Although the temperature depends on the temperature of the circulating medium liquid 9 set by the temperature controller 17, the mold temperature can be kept at a predetermined temperature.

Next, the situation when molding is performed using this conventional mold temperature control device will be explained with reference to FIG.

In the figure, the area indicates the mold temperature when no molding is being performed, the BeJf area is the state after molding has started, the C area is the mold temperature during molding, and the D'v4 area is the mold temperature when molding is stopped. This shows the changes in TM. In Figure 6, A eJf
Since molding is not performed in this region, no heat is applied to the molds 1 and 2 in FIG. 5, so the mold temperature is the medium liquid temperature tA. When the B 9i region, that is, the molding is started, heat is applied to the molds 1 and 2 by high temperature molten resin (usually 200° C. to 300° C.) in order to obtain the plastic molded product 3 shown in FIG.

(The explanation of the injection molding operation is omitted because it is not the main purpose of this application.) Therefore, the temperature tB of the molds 1 and 2 can no longer be maintained at the medium liquid temperature, and gradually begins to rise, and the injection molding The temperature is stabilized at a certain constant temperature tC commensurate with the cycle time of the machine and the amount of resin, and molded products can be stably obtained thereafter.

Next, in the D'J region, when molding is stopped midway, the temperature tD of the molds 1 and 2 depends on the medium liquid temperature, and therefore rapidly decreases toward the temperature tA.

[Problem that the invention seeks to solve]

Here, in the Bvj area of FIG. 6, there are the following notable problems. In other words, molding starts when the temperatures of molds 1 and 2 are low (Ti = tA), and resin is injected into molds 1 and 2, but because the mold temperatures are cold, the flow of the resin is poor. , the mold is not completely filled, and the weight W of the molded product 3 becomes slightly lighter, as shown by the lower dot graph in FIG.

This tendency is improved in region B, as the mold temperature tB approaches the temperature tC and becomes stable as the molding shot progresses (during molding in the JAM region, it becomes less affected). As described above, the conventional method has the disadvantage that it is difficult to obtain a homogeneous molded product for a while after the start of molding.

Next, D in Figure 6? In the iJt range, that is, when molding is stopped, as shown in Figure 5, the temperature of molds 1 and 2 drops rapidly, which can cause condensation on the surface of molds 1 and 2 when the temperature and humidity are high, such as in the summer. There are many. Therefore, when molding is restarted, it takes time to remove the condensation, and the condensation causes problems such as rust on the molds 1 and 2.

Conventionally, such a problem has been solved by having an operator change the temperature setting value of the temperature controller 17 shown in FIG.

An object of the present invention is to provide a method and apparatus that solve the problems of the prior art.

[Means for solving problems]

The present invention includes molds 1 and 2, piping jackets 4a and 4b provided on these molds 1 and 2, and piping jacket 4.
a, 4b and a heating/cooling tank 8, a pump 7 that circulates a circulating medium liquid 9 for adjusting the temperature TM of the mold 1.2, and a cooling electric control valve that adjusts the cooling amount of this heating/cooling tank 8. 11, a heating electric control valve 14 that adjusts the amount of heating, a temperature controller 17a that controls the cooling electric control valve 11 and the heating electric control valve 14 by output electric signals 18a and 19a, and this temperature control This is a plastic injection molding machine consisting of a sequence control device 20 that controls a total of 17a.

The temperature controller 17a has a medium liquid temperature set value Ts(1) when the injection molding machine is stopped, and a medium liquid temperature set value Ts ti during operation when the injection molding machine is in operation.

Slowdown time set value TS LOW that changes continuously from the set value during stoppage to the set value during operation + Wait time set value TWAIT that maintains the set value during operation for a while even if the operation of the injection molding machine is stopped and the RUN signal 21 or STOP signal 22, which is a contact signal from the outside of the temperature controller 17a, are received.
Control output signals 21 from the SF3 section that controls the PROG section and the 5IEQ section during operation and stop of the injection molding machine,
22, the above set value Ts, 1+ or Ts
(Switch 21 programmatically, set value output ESET
a PROG section that generates a feedback signal EFB in response to an electric signal a proportional to the temperature of the medium liquid 9 detected by the temperature sensing element 16; , and a C0NT section that generates a control output θo for controlling the temperature of the medium liquid 9 based on the deviation output ε.

[For production]

The temperature set value Ts of the medium liquid 9 of this temperature controller 17a changes according to the operation mode of the injection molding machine by the output signals 21 and 22 of the sequence control device 20, and when the injection molding machine is stopped, the mold 1. During the operation of the injection molding machine, the temperature TM of the molds 1 and 2 is maintained at the temperature T0 of the corresponding molds 1 and 2, and at the start of operation of the injection molding machine, the temperature TM is set in advance to balance the amount of heat given from the molten molding material. Then, the temperature setting value Ts of the medium liquid 9 is continuously changed in a gradient manner (Ts L+, -TS (21)).

〔Example〕

Embodiments of the temperature control method according to the present invention will be described in detail below with reference to FIGS. 1 to 4.

In FIG. 1, the same parts as in the conventional FIG. 5 are given the same reference numerals, and only the different parts will be explained.

17a is a temperature controller according to the method of the present invention, 18a is a cold water regulation output electric signal from the temperature controller 17a, 19a
is a steam control output electric signal from the temperature controller 17a, and 20 is a sequence control device, which is responsible for controlling the operation sequence of the injection molding machine (sequence control of the sequence control injection machine is not the gist of this application. (so it will be omitted). Reference numeral 21 indicates a RUN signal detected by the sequence control device 20 indicating that the injection machine is in operation, and 22 similarly indicates a STOP signal indicating that the injection machine is stopped.

FIG. 2 is a control block diagram of the temperature controller 17a in FIG. 1. In Fig. 2, TS (11 is the medium liquid temperature setting value during stoppage + TS, 2
+ is the operating setting value of the medium liquid temperature during operation of the injection molding machine + TSLOW is the slowdown time setting value that sets the time for continuous change from the stopping setting value to the operating setting value, T, IALT are Indicates the wait time setting value that sets the time to maintain the set value during operation for a while even if the operation of the injection molding machine is stopped. The SEQ section receives a RUN signal 21 or a STOP signal 22, which is a contact signal from the outside of the temperature controller 17a, and controls the PROG section. The PROG section has the role of programmatically switching Ts (1) or Ts +21 in response to control signals from the SEQ section when the injection molding machine is in operation (RUN signal ON in this case) and stopped (STOP signal ON in this case). It has the function of generating the set value output E3,1.

In FIG. 2, TC indicates the temperature measuring element 16 in the first embodiment shown in the first figure, and sends an electric signal a proportional to the temperature of the medium liquid 9 detected by the temperature measuring element 16 to the FB section, Assume that a feedback signal EFB at the addition point X is generated. Addition point X compares set value output ESET and feedback signal E□ (temperature of medium liquid 9) to obtain deviation output ε. The C0NT section receives this deviation output ε, performs automatic control calculations such as PID calculation, and generates a control output θo.

The HC section receives this control output θo and distributes it to the next level 8007 section and CoUT section to switch the control amount. That is, the section 8007 outputs an opening adjustment output θ8 corresponding to the electric signal 19a for operating the electric steam control valve 14 in FIG. 1 of the embodiment. Further, the CoUT section outputs an opening adjustment output θ, which corresponds to the electric signal 18a for operating the electric cold water adjustment valve 11 in FIG. 1 of the embodiment.

As described above, the temperature controller 17a according to the present invention has a preset medium liquid temperature setting value Ts(1) during stoppage.

Medium liquid temperature operating setting value TS+Z) + slowdown time setting value TSLO, wait time setting value TwA+r
As shown in FIG. 2, when the 0N-OFF state of the RUN signal 2L and STOP signal 22, which are contact signals of the sequence control device 20 from the outside, changes as shown by lines A and B in FIG. Then, the temperature controller 17a is
It acts to change the temperature set value output BSET as indicated by line C in the figure, and acts to control the temperature of the medium liquid 9 to be constant in accordance with the temperature set value output E3.7.

In FIG. 4, TM indicates the temperature of the mold 1°2 in FIG. 1. T8 is the circulating medium liquid 9 in FIG.
It shows the temperature of

Next, referring to FIGS. 3 and 4, the operation of the embodiment of the present invention will be described.

First, in region 0 during operation of the molding machine, a medium liquid having a temperature TW is circulated through the mold 1.2 shown in the first figure, and molding is performed. Temperature T...
1 and the set value Ts(1) of the medium liquid temperature Tw at that time, and set this temperature TMI as the medium liquid temperature set value (Ts(1) - TM) in the area ■ in Fig. 4, that is, during stoppage. . Also, the temperature setting value Ts of the medium liquid 9 during good operation
+2) and set it as the medium liquid temperature setting value T during operation.
Set s and z+ together. Therefore, while the injection molding machine is stopped, the temperature TM of the molds 1 and 2 is maintained at the preset temperature TMI of the molds 1 and 2, which corresponds to the temperature TMI during operation of the injection molding machine.

Next, when the RUN signal 21 in FIG. 4 is turned on, that is, molding starts in the @ area, the temperature TM of the mold 1.2 in FIG. Since the temperature is originally Ts (11" TMI, that is, stable molding temperature), the fluidity of the resin is moderate, and the resulting filling weight does not deviate greatly from the state at stable molding.

Next, as the injection is repeated, the temperature of the mold 1.2 increases due to the temperature of the resin of the molded product 3.
As can be seen with the conventional method shown in the figure, the temperature setting value Ts of the medium liquid 9 is gradually lowered from Ts(1) in a gradient manner as shown by the line C in @ in Figure 3 at a rate just enough to eliminate the increase.
Set it to tz+. That is, at the start of operation of the injection molding machine, the temperature set value Ts of the molds 1 and 2 is set at a gradient (TS++1-
Since the temperature T of molds 1 and 2 changes continuously to TS (21),
is balanced with the amount of heat given from the molded product 3, and does not change much compared to the conventional one shown in FIG.

That is, even if the temperature of the medium liquid 9 gradually decreases to the temperature during operation as shown by the line in the @ area of FIG. 4, the mold temperature T,
does not change as shown by the line E in the @ area in Figure 4, and therefore the fluidity of the resin is not affected and the weight W of the molded product remains at the 4th mark.
As shown in the dot graph at the bottom of the figure, variations are also reduced.

In this way, the injection molding machine shifts to stable operation as shown in the O-molding machine operating region in FIGS. 3 and 4.

Next, the STOP signal 22 is turned ON as shown in the area ■ in FIG.
In other words, when the molding machine stops, the set value Ts is delayed by 7 hours as shown by line C in FIG.
is Ts (returns from 21 to the original stop temperature set value TS (11), and increases the temperature Tw of the medium liquid 9 as shown by the line in the ■ area in FIG. To prevent.

〔Effect of the invention〕

As described above, according to the temperature control method according to the present invention,
Prevents variations in molded product weight at the start of molding,
It prevents the occurrence of molding defects, stabilizes the quality of molded products, and is extremely useful for improving the quality of molded products.

Furthermore, it is possible to prevent rust from occurring due to dew condensation on the mold caused by stopping molding.

[Brief explanation of the drawing]

Fig. 1 is a block diagram of a mold temperature control device according to an embodiment of the present invention, Fig. 2 is a block diagram of the function of the temperature controller, which is the gist of the device, Fig. 3 is an explanatory diagram of its operation, and Fig. 4 is A graph showing the relationship between mold temperature and medium temperature and fluctuations in the weight W of the molded product in an embodiment of the present invention, FIG. 5 is a block diagram of a mold temperature control device according to the conventional method, and FIG. It is a graph showing the relationship between mold temperature and medium temperature and the variation in weight W of the molded product. 1.2...Mold, 17a...Temperature controller, 4a, 4b...Piping jacket, 7.
... Pump, 8 ... Heating and cooling tank, 9
...Medium liquid, 11...Electric control valve for cooling, 14...Electric control valve for heating, 20...
...Sequence control device, 21, 22...Electric signal, TM...Mold temperature, Ts...
Mold temperature setting value, 3... Molded product, 18a, 19
a...Output electrical signal.

Claims (2)

[Claims] (1) In a method for controlling the temperature of a mold in a plastic injection molding machine, a temperature controller receives an electric signal corresponding to the operating mode of the injection molding machine from a sequence control device, thereby adjusting the temperature setting value of the medium liquid. The temperature of the mold is set in advance while the injection molding machine is stopped.The temperature of the mold is maintained at the corresponding mold temperature while the injection molding machine is in operation, and when the injection molding machine starts operating, the amount of heat given from the molten molding material and A mold temperature control method for a plastic injection molding machine, characterized by continuously changing the temperature setting value of a medium liquid in a gradient manner so as to act in a balanced manner. (2) A mold, a piping jacket provided on this mold, a pump that circulates a circulating medium liquid for controlling the temperature of the mold through this piping jacket and a heating and cooling tank, and cooling of this heating and cooling tank. A cooling electric control valve that adjusts the amount of heating, a heating electric control valve that adjusts the amount of heating, a temperature controller 17a that controls these cooling electric control valves and heating electric control valves by output electric signals, and In a plastic injection molding machine including a sequence control device that controls a temperature controller 17a, the temperature controller 17a is configured to adjust the temperature of the medium liquid during stoppage Ts_(_1
_), medium liquid temperature during operation of the injection molding machine, operating set value Ts_(_2_), slowdown time set value T that continuously changes from the set value during stop to the set value during operation.
_S_L_O_W, a setting section for setting a wait time set value T_W_A_I_T that maintains the set value for a while during operation even if the operation of the injection molding machine is stopped, and a RUN signal 21 which is a contact signal from the outside of the temperature controller 17a.
Alternatively, the SEQ section that receives the STOP signal 22 and controls the PROG section, and the control output signals 21 and 22 from this SEQ section during operation and stop of the injection molding machine, set the above set value Ts_(_1_ ) or Ts_(_2_) in a programmatic manner to generate a set value output E_S_E_T, and a PROG unit that receives an electric signal a proportional to the temperature of the medium liquid 9 detected by the temperature measuring element 16 and generates a feedback signal E_F_B. an FB section that compares the set value output E_S_E_T and this feedback signal E_F_B to obtain a deviation output ε; and a control output θ_o that controls the temperature of the medium liquid 9 from this deviation output ε.
A mold temperature control device for a plastic injection molding machine, characterized in that it has a CONT section that generates.