JP7458298B2 - Method for raising the temperature of a hot runner mold, hot runner mold, and injection molding machine - Google Patents

Description

The present invention relates to a method for increasing the temperature of a hot runner mold in which multiple heaters and temperature sensors are provided inside the mold and the resin temperature of the runner inside the mold is controlled, in which the resin in the runner is melted from its solidified state by a heater to a state where a molding cycle is possible.

A hot runner mold is a mold in which a heater that heats the runner is provided in the mold, and the temperature of the resin in the runner can be controlled. When molding using a hot runner mold, the resin in the runner can be maintained in a molten state even when the resin filled in the mold cavity cools and solidifies, so the solidified runner can be discarded. There is no need for it and there is less waste of resin. Hot runner molds include an open gate type in which the gate is always open and a valve gate type in which the gate is opened and closed by a valve.

Japanese Patent Application Publication No. 9-150444

In an open gate type hot runner mold, in order to prevent stringing from the gate when taking out a molded product, it is necessary to temporarily lower the resin temperature near the gate, that is, the resin temperature at the hot runner nozzle.

Patent Document 1 describes a temperature control method for raising the resin temperature of each hot runner nozzle in an open-gate hot runner mold with multiple gates from a reduced state to a temperature at which injection is possible. According to this document, output time data is obtained in advance for each of the multiple hot runner nozzles, which is the time required to reach the desired temperature when a certain level of heating power is applied to the heater. In the molding cycle, the timing for turning on the heater is shifted based on the output time data of each hot runner nozzle, and control is performed so that the temperature rise is completed simultaneously for the multiple hot runner nozzles. In this way, there is no need to provide a temperature sensor for each hot runner nozzle, and all hot runner nozzles can be brought to the desired temperature simultaneously.

The temperature increase method described in Patent Document 1 is intended for open-gate type hot runner molds, and aims to simultaneously raise the temperatures of multiple hot runner nozzles to the desired temperature during injection when the molding cycle is repeated. However, hot runner molds include not only open-gate types but also valve-gate types, and both types have common problems that need to be solved.

Specifically, in a hot runner mold, when the molding cycle is stopped and the resin inside the runner is completely solidified, the runner is heated by a heater to melt the resin and become ready to start the molding cycle. However, there is a problem in that the resin remains at a high temperature for a long period of time, resulting in a decrease in the quality of the resin. Among the plurality of hot runners in the mold, there are parts where heating is completed quickly, and parts where heating is completed later. The parts whose temperature has been raised earlier will remain at high temperature and will have to wait for the parts whose temperature has been raised later to be raised, causing a problem of resin deterioration during the waiting time. Therefore, in the present disclosure, a method for increasing the temperature of a hot runner mold is provided that suppresses deterioration of resin quality as much as possible.

Other objects and novel features will become apparent from the description of this specification and the accompanying drawings.

This disclosure is directed to a hot runner mold in which a plurality of heaters and a plurality of temperature sensors are provided within the mold, and is a method of heating the runner with heaters from a state in which the mold has cooled and the resin in the runner has solidified, thereby melting the resin and making it possible to start a molding cycle. According to this disclosure, the heating method is composed of a preparation stage and an execution stage. The preparation stage is composed of a first step of determining a sensor-specific set temperature, which is the temperature at which heating is completed for each of the plurality of temperature sensors, and a second step of turning on the plurality of heaters from a state in which the mold has cooled and the resin in the runner has solidified, and obtaining a sensor-specific temperature arrival time, which is the time it takes each of the temperatures detected by the plurality of temperature sensors to reach the sensor-specific set temperature. And the execution stage is to control the plurality of heaters so that the timing at which each of the temperatures detected by the plurality of sensors reaches the sensor-specific set temperature is consistent based on the sensor-specific temperature arrival time, when the mold has cooled and the resin in the runner has solidified, thereby heating the runner with the plurality of heaters to melt the resin and make it possible to start a molding cycle.

According to the present disclosure, when the mold is cooled and the resin in the runner is solidified, when the heater heats the runner, the resin in the runner is not maintained at a high temperature for a long time, and the resin deteriorates. It can be prevented.

1 is a front view showing an injection molding machine according to an embodiment of the present invention; 1 is a front sectional view showing a part of an injection molding machine according to an embodiment and an open gate type hot runner mold according to an embodiment. 1 is a front sectional view showing a part of an injection molding machine according to an embodiment and a valve gate type hot runner mold according to an embodiment. It is a flowchart which shows the preparation stage of the temperature raising method of the hot runner mold based on this Embodiment. 7 is a graph showing changes in temperature detected by a plurality of temperature sensors in the mold when the mold is heated in the preparatory stage of the hot runner mold temperature raising method according to the present embodiment. It is a flowchart which shows the execution stage of the temperature raising method of the hot runner mold based on this Embodiment. 2 is a graph showing changes in temperature detected by a plurality of temperature sensors in the mold when the mold is heated in an execution step of the hot runner mold temperature raising method according to the present embodiment. 2 is a graph showing changes in temperature detected by a plurality of temperature sensors in the mold when the mold is heated in an execution step of the hot runner mold temperature raising method according to the present embodiment.

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiments. For clarity of explanation, the following description and drawings have been simplified where appropriate. In each drawing, the same elements are designated by the same reference numerals, and redundant explanation will be omitted as necessary. In addition, hatching is omitted in some parts to avoid cluttering the drawings.

<Injection molding machine>
As shown in FIG. 1, an injection molding machine 1 according to the present embodiment is roughly configured from a mold clamping device 2 and an injection device 3 provided on a bed B. The mold clamping device 2 includes a fixed platen 7, a movable platen 8, a mold clamping housing 9, tie bars 10, 10, . . . connecting the mold clamping housing 9 and the fixed platen 7, and a toggle mechanism 11. The mold can be opened and closed by driving the toggle mechanism 11. The fixed platen 7 and the movable platen 8 are provided with hot runner molds 14 according to this embodiment, and the hot runner molds 14 will be explained in detail later.

The injection device 3 is roughly composed of a heating cylinder 16 and a screw inserted into the heating cylinder 16. The injection molding machine 1 according to the present embodiment is provided with a controller 18, and not only the mold clamping device 2 and the injection device 3 but also the hot runner mold 14 are connected to the controller 18 and controlled. There is.

<Hot runner mold open gate type>
The hot runner mold 14 according to the first embodiment will be explained. FIG. 2 shows a so-called open gate type hot runner mold 14. As shown in FIG. The hot runner mold 14 includes a fixed mold 21 attached to the fixed platen 7 and a movable mold 22 attached to the movable platen 8.

The movable mold 22 has two relatively large protrusions 24, 25 and two small protrusions 26, 27 formed at its parting line. To correspond to these protrusions 24, 25, 26, 27, the fixed mold 21 has two relatively large recesses 29, 30 and small recesses 31, 32 formed at its parting line. Therefore, when the molds 21, 22 are clamped, two relatively large cavities and two small cavities are formed.

Inside the stationary mold 21, there are a sprue bushing 35, a manifold 36, two relatively large hot runner nozzles 38 and 39 provided in the manifold 36, and two small hot runner nozzles 40. 41 are provided. The hot runner nozzles 38, 39, 40, and 41 have gates at their tips and are connected to their respective cavities to inject resin. Further, the sprue bushing 35 is touched by an injection nozzle 17 provided at the tip of the heating cylinder 16.

<Heater>
The sprue bushing 35 provided on the stationary mold 21 is provided with a heater 43 on the outside thereof, and the hot runner nozzles 38-41 are provided with heaters 45-48 on the outside thereof, respectively. A plurality of heaters 44, 44, . . . are embedded in the manifold 36. Power can be supplied to these heaters 43 to 48 independently by the controller 18. Further, when the heaters 43 to 48 are supplied with electric power, they heat the sprue bushing 35, the manifold 36, and the hot runner nozzles 38 to 41 so that the resin flow paths, that is, the runners formed inside these are heated. It has become. Note that the connections between each of the heaters 43 to 48 and the controller 18 are omitted in FIG. 2 so as not to complicate the diagram.

<Temperature sensor>
The stationary mold 21 is provided with temperature sensors 50 to 55 corresponding to the sprue bushing 35, the manifold 36, and the four hot runner nozzles 38 to 41 to detect their respective temperatures. These temperature sensors 50 to 55 are also connected to the controller 18 so that the temperatures of the sprue bushing 35, the manifold 36, and the four hot runner nozzles 38 to 41 are input to the controller 18. However, the connections between the temperature sensors 50 to 55 and the controller 18 are omitted in FIG. 2 so as not to complicate the diagram.

The temperature raising method according to this embodiment is carried out on the hot runner mold 14 according to the first embodiment, but it can also be carried out on the hot runner mold 14' according to other embodiments. can. Before explaining the temperature raising method according to this embodiment, the hot runner mold 14' according to the second embodiment will be explained.

<Hot runner mold valve gate type>
The hot runner die 14' according to the second embodiment is of a valve gate type, as shown in Fig. 3. Descriptions of the same members as those in the hot runner die 14 according to the first embodiment will be omitted. The hot runner die 14' according to this embodiment is provided with needle-shaped valves 57-60 for the hot runner nozzles 38-41. These valves 57-60 are driven by piston-cylinder units 61-64, respectively.

<Method for increasing temperature of hot runner mold according to this embodiment>
The method of raising the temperature of the hot runner mold according to the present embodiment is to heat the heaters 43 to 48 so that the resin inside the runners is heated after the molds 14, 14' have cooled and the resin inside the runners has completely solidified. This is a temperature raising method that melts the material and makes it possible to perform a molding cycle. This temperature raising method can be carried out for both the hot runner molds 14 and 14' according to the first and second embodiments. The method for increasing the temperature of a hot runner mold according to this embodiment includes a preparation stage and an execution stage.

<Preparatory stage>
<Setting the temperature setting for each sensor>
In the preparation stage, as shown in FIG. 4, the controller 18 first performs setting S1 of the temperature setting for each sensor. The sensor-specific set temperature is the temperature set for each of the temperature sensors 50 to 55 at the time of completion of heating. Once each temperature sensor 50-55 reaches its respective sensor specific set temperature, the molding cycle can begin. Since the temperature suitable for injection differs depending on the type of resin, the set temperature for each sensor needs to be determined according to the type of resin. The appropriate temperature also differs depending on the type of gate, whether an open gate type hot runner mold 14 or a valve gate type hot runner mold 14' is used. The table below summarizes the appropriate injection temperatures for different resin types and gate types.

For example, when polymethyl methacrylate (PMMA) is used, the set temperature for each sensor is set with reference to 250° C., which is the temperature at the time of injection. The temperature setting for each sensor may be set to the same temperature for the temperature sensors 50 to 55, or may be set to different temperatures. For example, temperature sensor 50 can be set to 246°C, temperature sensor 51 can be set to 248°C, and temperature sensors 52 to 55 can be set to 250°C. However, in the case of an open gate type hot runner mold 14', the set temperature for each sensor may be set with reference to the temperature during standby. For example, the temperature sensor 50 can be set to 245°C, the temperature sensor 51 can be set to 247°C, and the temperature sensors 52 to 55 can be set to 210°C, which is the standby temperature. The time required to raise the temperature from the standby temperature to the injection temperature is 2 to 3 seconds.

<Temperature increase test from solidified state>
In the preparation stage, next a temperature increase test S2 from the solidified state is performed. The molding cycle is stopped and the power supply to the heaters 43 to 48 of the hot runner molds 14, 14' is stopped to completely solidify the resin in the runner. From this state, the heaters 43 to 48 are started to be energized all at once, and the standardly set power is supplied to each of them. FIG. 5 shows how the temperature changes in each of the temperature sensors 50 to 55. Reference numerals 71 and 72 indicate sensor-specific set temperatures for the temperature sensors 50 and 51, reference numeral 73 indicates sensor-specific set temperatures for the temperature sensors 52 and 53, and reference numeral 74 indicates sensor-specific set temperatures for the temperature sensors 54 and 55. There is. The respective times when the temperature sensors 50 to 55 reach the set temperatures 71 to 74 for each sensor, that is, the temperature attainment times 76 to 79 for each sensor are obtained and set in the controller 18.

As mentioned above, in the temperature increase test S2 from the solidified state, the heaters 43 to 48 are energized all at once from the state where the resin in the runner is completely solidified, and the temperature reaching time 76 for each sensor is increased at once. It is preferable to obtain a score of 79. However, the sensor-specific temperature arrival times 76 to 79 may be obtained separately for each of the temperature sensors 50 to 55. For example, to obtain the sensor-specific temperature arrival time of a certain temperature sensor, from the state where the resin in the runner is completely solidified, only the heater near the temperature sensor is energized and the time it takes for the temperature sensor to reach the set temperature is measured. do. If this operation is performed for each of the temperature sensors 50 to 55, temperature attainment times 76 to 79 for each sensor can be obtained, respectively.

<Execution stage>
The execution stage is a process carried out when starting a molding cycle from a state where the injection molding machine 1 has been stopped for a long time. 14 and 14' are heated and heated to a state where the molding cycle can be started. The injection molding machine 1 according to the present embodiment is provided with two temperature raising modes, which can be selected. One of the temperature increase modes is set in advance in the controller 18. As shown in FIG. 6, the controller 18 performs temperature increase mode selection S11.

<Staggered start mode>
The controller 18 executes processing S12 when the time difference startup mode is set as the temperature increase mode. First, the sensor-specific temperature attainment time which is the longest among the sensor-specific temperature attainment times 76 to 79 shown in FIG. 5 is found. Since the sensor-specific temperature arrival time 77 is the longest, the corresponding heater 44 is started to be energized with standard power.

Then, find the temperature arrival time for each sensor with the next longest time. Since the sensor-specific temperature arrival time 76 is the next longest, the corresponding heater 43 is started to be energized with standard power. At this time, the timing of turning on the heater 43 is delayed by the time difference between the sensor-specific temperature arrival time 77 of the heater 44 that is turned on first and the sensor-specific temperature arrival time 76 of the heater that is turned on next.

Then, search for the temperature arrival time for each sensor, which is the next longest time, that is, the third longest time. Since the sensor-specific temperature arrival time 79 is the third longest, the corresponding heaters 47 and 48 are started to be energized with standard power. At this time, the timing of turning on the heaters 47 and 48 is delayed by the time difference between the sensor-specific temperature arrival time 77 of the heater 44 that is turned on first and the sensor-specific temperature arrival time 79 of the heaters 47 and 48 that are turned on third. .

Finally, the heaters 45 and 46 corresponding to the shortest sensor-specific temperature arrival time 78 are energized with standard power. At this time, the timing of turning on the heaters 45 and 46 is delayed by the time difference between the sensor-specific temperature arrival time 77 of the heater 44 that is turned on first and the sensor-specific temperature arrival time 78 of the heater that is turned on last.

By sequentially turning on the heaters 43 to 48 in this manner, the timings at which the respective temperatures detected by the temperature sensors 50 to 55 reach the set temperature for each sensor can be made to coincide. This situation is shown in the graph of FIG. That is, the timing 80 at which all the temperature sensors 50 to 55 reach the set temperature for each sensor is made to coincide. After timing 80, it is possible to start the molding cycle.

<Power adjustment mode>
When the power adjustment mode is set as the temperature increase mode, the controller 18 executes processing S13. That is, the heaters 43 to 48 start being energized all at once. However, although the heater 44 corresponding to the longest sensor-specific temperature attainment time 77 (see FIG. 5) among the sensor-specific temperature attainment times 76 to 79 is energized with standard power, the other heaters 43, 45 -47 should be energized with less power than the standard power. Specifically, the shorter the time required for each sensor to reach the temperature, the smaller the electric power applied to the heaters 43, 45-47.

As a result, as shown in FIG. 8, the timing 81 at which all the temperature sensors 50 to 55 reach the set temperature for each sensor is made to coincide. After timing 81, it is possible to start the molding cycle. The controller 18 performs processing S14 following processing S13. That is, when all the temperature sensors 50 to 55 reach their individual sensor set temperatures, the power supplied to the heaters 43 to 48 is returned to the standard power.

Although the invention made by the present inventor has been specifically explained based on the embodiments above, the present invention is not limited to the embodiments already described, and various changes can be made without departing from the gist thereof. It goes without saying that it is possible. The plurality of examples explained above can also be implemented in combination as appropriate.

1 Injection molding machine 2 Mold clamping device 3 Injection device 7 Fixed plate 8 Movable plate 9 Mold clamping housing 10 Tie bar 11 Toggle mechanism 14 Hot runner mold 16 Heating cylinder 18 Controller 21 Fixed side mold 22 Movable side mold 35 Sprue bushing 36 manifold
38~41 Hot runner nozzle 43~48 Heater 50~55 Temperature sensor 57~60 Valve 61~64 Piston cylinder unit 71~74 Set temperature for each sensor 76~79 Temperature attainment time for each sensor

Claims (15)

In a hot runner mold that includes a plurality of heaters and a plurality of temperature sensors in the mold and controls the temperature of a resin in a runner in the mold, the mold is cooled and the resin in the runner is solidified. A temperature raising method that heats the runner from a state in which the runner is heated by a plurality of the heaters to melt the resin and bring it into a state where a molding cycle can be started,
The temperature raising method includes a preparation step carried out in advance and an execution step,
The preparation step includes a first step of determining a set temperature for each sensor, which is a temperature at which heating is completed, for each of the plurality of temperature sensors;
The time it takes for each of the temperatures detected by the plurality of temperature sensors to reach the set temperature for each sensor by turning on the plurality of heaters from a state in which the mold has cooled and the resin in the runner has solidified. a second step of obtaining temperature arrival time for each sensor;
The execution step is when the mold is cooled and the resin in the runner is solidified, and then the plurality of heaters heat the runner to melt the resin and make it possible to start the molding cycle. , controlling the plurality of heaters so that the timing at which each of the temperatures detected by the plurality of sensors reaches the set temperature for each sensor is the same based on the temperature arrival time for each sensor; How to raise temperature. 2. The method of heating a mold according to claim 1, wherein in the execution step, the timing of starting energization is shifted for each of the plurality of heaters so that the timing of completion of heating coincides with each other. 2. The mold heating method according to claim 1, wherein in the execution step, electric power supplied to each of the plurality of heaters is controlled to match the timing of completion of heating. The mold heating method according to any one of claims 1 to 3, wherein the mold is a valve gate type having a valve at the gate. 4. The method of heating a mold according to claim 1, wherein the mold is of an open gate type with an open gate. A hot runner mold in which the resin temperature of a runner in the mold is controlled,
a plurality of heaters provided within the mold;
comprising a plurality of temperature sensors provided in the mold and a controller that controls the plurality of heaters,
The controller contains sensor-specific set temperatures, which are temperatures at which heating is completed for each of the plurality of temperature sensors, and turns on the plurality of heaters from a state in which the mold has cooled and the resin in the runner has solidified. A sensor-specific temperature arrival time is set, which is a time for each of the plurality of temperature sensors to reach the sensor-specific set temperature,
The controller includes:
When the mold is cooled and the resin in the runner is solidified, the runner is heated by the plurality of heaters to melt the resin and make it possible to start a molding cycle;
For each of the temperatures detected by the plurality of temperature sensors, the plurality of heaters are controlled based on the temperature arrival time for each sensor so that the timing of completion of temperature rise to reach the set temperature for each sensor coincides. , hot runner mold. The hot runner mold according to claim 6, wherein the controller determines the timing of starting energization for each of the plurality of heaters so that the timing of completion of temperature increase coincides. The hot runner mold according to claim 6, wherein the controller controls the electric power supplied to each of the plurality of heaters so that the timing of completion of temperature increase coincides. The hot runner mold according to any one of claims 6 to 8, wherein the mold is of a valve gate type in which a valve is provided at the gate. The hot runner mold according to any one of claims 6 to 8, wherein the mold is an open gate type with an open gate. a mold clamping device in which a mold is installed;
an injection device that injects resin;
comprising a controller;
The mold is a hot runner mold in which a plurality of heaters and a plurality of temperature sensors are provided inside to control the resin temperature of a runner in the mold,
The controller contains sensor-specific set temperatures, which are temperatures at which heating is completed for each of the plurality of temperature sensors, and turns on the plurality of heaters from a state in which the mold has cooled and the resin in the runner has solidified. A sensor-specific temperature arrival time is set, which is a time for each of the plurality of temperature sensors to reach the sensor-specific set temperature,
The controller includes:
When the mold is cooled and the resin in the runner is solidified, the runner is heated by the plurality of heaters to melt the resin and make it possible to start a molding cycle;
For each of the temperatures detected by the plurality of temperature sensors, the plurality of heaters are controlled based on the temperature arrival time for each sensor so that the timing of completion of temperature rise to reach the set temperature for each sensor coincides. ,Injection molding machine. The injection molding machine according to claim 11, wherein the controller determines the timing of starting energization for each of the plurality of heaters so that the timing of completion of temperature increase coincides. The injection molding machine according to claim 11, wherein the controller controls the electric power supplied to each of the plurality of heaters so that the timing of completion of temperature increase coincides. The injection molding machine according to any one of claims 11 to 13, wherein the mold is of a valve gate type in which a valve is provided at the gate. The injection molding machine according to any one of claims 11 to 13, wherein the mold is an open gate type with an open gate.

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