Patent Application
20240316844
This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2023-047555 filed on Mar. 24, 2023, the entire content of which is incorporated herein by reference.
The present disclosure relates to a molding cycle stopping method for shifting a molding cycle from an operation state to a stop state in an injection molding machine, an injection device including a molding cycle stopping process, and an injection molding machine.
An injection molding machine includes a mold clamping device for clamping a mold, an injection device for melting an injection material and injecting the material into the mold, and the like. The injection device includes a heating cylinder and a screw placed in the heating cylinder. When the heating cylinder is heated by a heater and a resin is supplied from a hopper while rotating the screw, the resin is melted and fed to the front of the heating cylinder. That is, the resin is metered. An injection nozzle provided at a distal end of the heating cylinder is brought into contact with the clamped mold, and the screw is driven in an axial direction. As a result, the resin is injected into the mold to obtain a molded product.
Methods for operating an injection molding machine that can produce a high-quality molded product are proposed in various patent literature. For example, JP2018-111297A proposes a method for operating an injection molding machine when starting a molding cycle from a state where the injection molding machine is stopped. In the method for operating described in JP2018-111297A, the number of times of molding cycles required from the start of the molding cycle to the stabilization of the molding, that is, the number of times to stabilization is estimated. The number of times to stabilization is obtained by dividing an amount of resin remaining in the heating cylinder when the heating cylinder is stopped by an amount of resin injected in one molding cycle. The resin can be purged by an injection operation until the number of times to stabilization is reached. In a molding cycle after the number of times to stabilization, a resin that does not deteriorate can be injected, so that a high-quality molded product can be obtained.
As in the method described in JP2018-111297A, if the method for operating an injection molding machine when starting the molding cycle from a stop state of the molding cycle is implemented, a molded product can be molded without using the resin remaining in the heating cylinder during a stop period. This should result in a high-quality product. However, there is also a problem to be solved. For example, a molded product molded by injection molding includes an optical product such as lenses mounted on mobile phones. Such an optical product cannot be adopted as a product even if a slightest amount of so-called contamination, such as inclusion of a black spot, occurs. When the molding cycle stops for a long time, the resin remaining in the heating cylinder is likely to deteriorate. When the resin deteriorates, even if the resin is purged for a number of times equal to or more than the number of times to stabilization, there is a risk that a part of the deteriorated resin remains in the heating cylinder, and the quality of a molded product cannot be guaranteed.
The present disclosure provides a molding cycle stopping method that prevents deterioration of a resin in a heating cylinder.
Other problems and novel features will become apparent from description of the present description and the accompanying drawings.
One illustrative aspect of the present disclosure provides a method of stopping an operation of a molding cycle in an injection device including a heating cylinder and a screw provided in the heating cylinder. The molding cycle stopping method includes performing a temperature lowering process including lowering a temperature of the heating cylinder from a molding cycle execution temperature to a standby temperature, and performing a continuous purge process including repeatedly purging a resin until a predetermined termination condition is satisfied.
The present disclosure can reliably prevent the resin in the heating cylinder from deteriorating.
Hereinafter, specific illustrative embodiments will be described in detail with reference to the drawings. The present invention is not limited to the following illustrative embodiments. In order to clarify the description, the following description and the drawings are simplified as appropriate. In the drawings, the same elements are denoted by the same reference numerals, and repeated description thereof is omitted as necessary. In addition, hatching may be omitted to avoid complicating the drawings.
As shown in
The mold clamping device 2 includes a fixed plate 7, a movable plate 8, and a mold clamping housing 9. The fixed plate 7 is fixed to the bed B. The movable plate 8 is slidably provided on the bed B. The fixed plate 7 and the mold clamping housing 9 are connected by a plurality of tie bars 11, 11, . . . . The movable plate 8 is freely slidable between the fixed plate 7 and the mold clamping housing 9. A mold clamping mechanism, that is, a toggle mechanism 13 in the present illustrative embodiment is provided between the mold clamping housing 9 and the movable plate 8. The fixed plate 7 and the movable plate 8 are provided with a fixed mold 15 and a movable mold 16, respectively. Accordingly, the molds 15 and 16 are opened and closed when the toggle mechanism 13 is driven.
{Injection Device}
The injection device 3 includes a heating cylinder 19, a screw 20 provided in the heating cylinder 19, and a screw driving device 22. The heating cylinder 19 is supported by the screw driving device 22. The screw 20 is driven by the screw driving device 22 in a rotational direction and an axial direction. The heating cylinder 19 is provided with a hopper 23 and an injection nozzle 24. Further, heaters 25, 25, . . . are provided in the heating cylinder 19.
Among the zones HP, H1, . . . of the heating cylinder 19, zones H1, H2, . . . other than the hopper zone HP are provided with heaters 25, 25, . . . and temperature sensors 27, 27, . . . respectively. The temperatures of the respective zones HP, H1, . . . can be independently controlled by the heaters 25, 25, . . . and the temperature sensors 27, 27, . . . .
As shown in
In the first illustrative embodiment, the following setting data is stored in the setting information file 32.
The molding cycle execution temperature is a target temperature for controlling the heating cylinder 19 during operation of the molding cycle. The molding cycle execution temperature is set for each of the zones HP, H1, H2, . . . . For example, when the injected resin is polycarbonate, 290° C. is set for the first zone H1, and 300° C. is set for the second zone H2.
The standby temperature is a temperature of the heating cylinder 19 in the stop state of the molding cycle. The standby temperature is a temperature at which the resin maintains a molten state, temperature at which there is no risk of deterioration even if the molten state is maintained for a long time. For example, when the resin is polycarbonate, the temperature is set to 160° C., 170° C. and the like. An appropriate standby temperature is a temperature up to +30° C. from the glass transition point or melting point of the resin, preferably a temperature up to +10° C. to +20° C. from the glass transition point or melting point.
The molding cycle stopping process software group 30 according to the first illustrative embodiment repeats purging by the continuous purge process 35 when shifting the molding cycle to the stop state. The termination condition is a condition for terminating the continuous purge process 35. Although various conditions can be adopted as the termination conditions, in the first illustrative embodiment, an injection pressure abnormality generally provided in the injection molding machine 1 is adopted as the termination condition. In the injection molding machine 1, when the screw 20 is driven to inject the resin, an axial force acting on the screw 20, that is, injection pressure is monitored. When the injection pressure is higher than a normal range, it is detected as an injection pressure abnormality and an alarm is output. In the first illustrative embodiment, when the screw 20 is driven to purge, if the injection pressure abnormality occurs, it is assumed that the termination condition has been met and the purge is terminated.
The molding cycle stopping process according to the first illustrative embodiment will be described. When the operator performs a stop operation in the control device 4, the molding cycle stopping process according to the first illustrative embodiment is performed. Specifically, the control device 4 performs the temperature lowering process 33 and the continuous purge process 35 to be described below in parallel as the molding cycle stopping process.
In the temperature lowering process 33 according to the first illustrative embodiment, step S01 is first executed as shown in
In step S03, for the zones H1, H2, . . . reaching the standby temperature, temperature control is switched such that the standby temperature is set as the target temperature. That is, the zones H1, H2, . . . reaching the standby temperature are maintained at the standby temperature thereafter. Next, the temperature lowering process 33 executes step S04 to check whether all the zones H1, H2, . . . have reached the standby temperature. If there is a zone not reaching the standby temperature among the zones H1, H2, . . . (NO), the process returns to step S02. That is, monitoring is continued until a zone that newly reaches the standby temperature appears among the zones H1, H2, . . . . On the other hand, if all the zones H1, H2, have reached the standby temperature (YES), the temperature lowering process 33 is completed.
The continuous purge process 35 (see
The continuous purge process 35 then executes step S12. That is, it is checked whether a termination condition is satisfied. During the injection operation in the purging, the control device 4 monitors the injection pressure. If there is no injection pressure abnormality, it is determined that the termination condition is not satisfied (NO), and the process returns to step S11. That is, the purging is repeated. On the other hand, if the injection pressure abnormality occurs, it is determined that the termination condition is satisfied (YES), and the continuous purge process 35 is completed. Incidentally, the injection pressure abnormality occurs when the injection pressure during the injection operation is high. That is, the injection pressure abnormality occurs when the temperature of the resin decreases and the viscosity increases. Since the temperature is sufficiently low, even if the purging is terminated upon detection of such injection pressure abnormality, there is no risk of resin deterioration thereafter. The continuous purge process 35 may be stopped by the operator operating the control device 4 (see
In the molding cycle stopping process according to the first illustrative embodiment, the temperature of the resin is lowered from the molding cycle execution temperature to the standby temperature, and the purging is repeatedly executed while the temperature is high. Therefore, there is no risk that the resin in the heating cylinder 19 (see
For an injection molding machine according to a second illustrative embodiment, each device, each member, and the like are configured in the same manner as the injection molding machine 1 and the injection device 3 according to the first illustrative embodiment shown in
The molding cycle stopping process software group 30A according to the second illustrative embodiment also includes a setting information file 32A, a temperature lowering process 33A, and a continuous purge process 35A. Among them, the continuous purge process 35A is configured in the same manner as the continuous purge process 35 (see
Similarly to the setting information file 32 (see
In the temperature lowering process 33A of the molding cycle stopping process according to the second illustrative embodiment, the resin temperature is lowered with a substantially constant temperature change as described below. The setting data is for making the temperature change constant.
When the operation of the molding cycle is stopped, the operator performs the operation of stopping the operation in the control device 4, and the molding cycle stopping process according to the second illustrative embodiment is performed. The control device 4 performs the temperature lowering process 33A and the continuous purge process 35A to be described below in parallel as the molding cycle stopping process according to the second illustrative embodiment.
In the temperature lowering process 33A according to the second illustrative embodiment, step S21 is first executed as shown in
In step S23, it is checked whether there is a zone reaching the standby temperature among the zones H1, H2, . . . . If not (NO), the process returns to step S21 to repeat the process. That is, for each of the zones H1, H2, . . . , the target temperature is further lowered by the specified temperature range, and temperature control is performed. On the other hand, if there is a zone reaching the standby temperature among the zones H1, H2, . . . (YES), step S24 is executed. That is, the temperature control is switched such that the standby temperature is constant for the zones H1, H2, . . . .
Next, step S25 is executed. In step S25, it is checked whether all the zones H1, H2, . . . have reached the standby temperature. If there is a zone not reaching the standby temperature among the zones H1, H2, . . . (NO), the process returns to step S21. If all the zones H1, H2, . . . have reached the standby temperature (YES), the temperature lowering process 33A is completed.
The continuous purge process 35A is the same as the continuous purge process 35 in the first illustrative embodiment, and a description thereof will be omitted.
In the molding cycle stopping process according to the second illustrative embodiment, a rate of temperature drop in each of the zones H1, H2, . . . can be made substantially constant. Accordingly, the purging is performed while stably lowering the resin temperature, and the deterioration of the resin in the heating cylinder 19 (see
For an injection molding machine according to a third illustrative embodiment, each device, each member, and the like are configured in the same manner as the injection molding machine 1 and the injection device 3 according to the first illustrative embodiment shown in
The molding cycle stopping process software group 30B according to the third illustrative embodiment also includes a setting information file 32B, a temperature lowering process 33B, and a continuous purge process 35B.
Similarly to the setting information file 32A (see
In the molding cycle stopping process according to the third illustrative embodiment, when the operation of the molding cycle is stopped, the control device 4 (see
The allowable injection pressure is one of termination conditions for determining whether the continuous purge process 35B terminates the purging. In the first illustrative embodiment, the injection pressure abnormality generally provided in the injection molding machine 1 is adopted as the termination condition, and it is determined that the termination condition is satisfied when the injection pressure abnormality is detected in the injection operation of the purging. In the third illustrative embodiment, the allowable injection pressure is set separately from the injection pressure for detecting the injection pressure abnormality. These may be the same value or different values. When the injection pressure exceeding the allowable injection pressure is detected in the injection operation of the purging, it is determined that the termination condition is satisfied.
The purge unnecessary temperature is one of the termination conditions for determining whether the continuous purge process 35B terminates the purging. If the temperature of all the zones H1, H2, . . . (see
In the third illustrative embodiment, the operator may perform the operation of stopping the operation of the molding cycle in the control device 4 (see
The operator stops the molding cycle. Then, the control device 4 executes step S31 as shown in
In the continuous purge process 35B, the metering operation and the injection operation are executed to perform the purging as in the first illustrative embodiment. If the termination condition is not satisfied, the purging is continued, and if the termination condition is satisfied, the purging is completed. In the third illustrative embodiment, two termination conditions of the continuous purge process 35B are provided as described above. That is, the allowable injection pressure and the purge unnecessary temperature. When the injection pressure exceeding the allowable injection pressure is detected in the injection operation of the purging, it is determined that the termination condition is satisfied. Alternatively, if it is detected that the temperature of all the zones H1, H2, . . . (see
After the continuous purge process 35B is started in step S32, the control device 4 executes step S33. That is, it is determined whether the molding cycle is restarted by the operator. If the molding cycle is not restarted (NO), step S34 is executed to determine whether the grace time has elapsed. If the grace time has not elapsed (NO), the process returns to step S33. On the other hand, in step S33, if the restart of the molding cycle by the operator is detected (YES), step S35 is executed. That is, the continuous purge process 35B being executed is stopped. Next, the process returns to step S31. That is, the temperature lowering process 33B is not executed, and the shift to the stop state is cancelled. Thereafter, the control device 4 performs a molding cycle.
If it is determined in step S34 that the grace time has elapsed (YES), the control device 4 ends the preparatory stage and starts shifting to the stop state. That is, the temperature lowering process 33B is started in step S36. In the third illustrative embodiment, the temperature lowering process 33B is the same as the temperature lowering process 33A (
When the temperature lowering process 33B is started and a predetermined time has elapsed, the continuous purge process 35B, which is already being executed, ends when one of the termination conditions described above is satisfied. When the standby temperature is reached for all zones H1, H2, . . . , the temperature lowering process 33B is also terminated as described above. That is, the molding cycle stopping process is completed.
In the molding cycle stopping process according to the third illustrative embodiment, the control device 4 (see
The first, second, and third illustrative embodiments may be modified in various ways. For example, other conditions may be adopted as the termination condition. For example, the torque during rotation of the screw 20 may be adopted as the termination condition. When the temperature of the resin decreases, the torque increases. When the torque during the rotation of the screw 20 reaches a specified allowable torque, it can be determined that the termination condition is satisfied. Further, the termination condition may be satisfied when other abnormal states are detected. For example, an abnormal state such as resin material shortage. If the material runs out, when performing the metering operation in the continuous purge process 35, even if the screw 20 is rotated, the metering is not done properly. When a metering time exceeds a specified time or when an abnormal rotation occurs in which the screw 20 does not retreat, it is naturally necessary to terminate the continuous purge process 35. That is, the occurrence of such an abnormality can also be regarded as the termination condition.
Although the invention made by the present inventors is specifically described based on the illustrative embodiments, it is needless to say that the present invention is not limited to the illustrative embodiments described above, and various modifications can be made without departing from the scope of the invention. The plurality of examples described above may be appropriately combined.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-047555 | Mar 2023 | JP | national |
