SCREW ADJUSTMENT METHOD IN THERMOSETTING RESIN INJECTION MOLDING MACHINE

A screw adjustment method in a thermosetting resin injection molding machine including a cylinder having a nozzle at a tip end of the cylinder and a screw accommodated in the cylinder. The screw adjustment method includes: contacting a screw and nozzle including bringing a tip end surface of the screw into contact with a tip end inner surface of an inner peripheral surface of the nozzle; moving the screw backward by a specified length after the contacting of the screw and the nozzle; and determining a screw position of the screw moved backward as a most forward position of the screw in a molding cycle.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based on and claims priority under 35 USC 119 from Japanese Patent Application No. 2023-049833 filed on Mar. 27, 2023, the entire content of which is incorporated herein by reference.

TECHNICAL FIELD

The present disclosure relates to a screw adjustment method in an injection molding machine for injecting a thermosetting resin, a thermosetting resin injection device, and a thermosetting resin injection molding machine.

BACKGROUND

A thermosetting resin injection molding machine for injecting a thermosetting resin as an injection material includes a mold clamping device and an injection device, for example, as described in JPH11-216754A. The injection device includes a cylinder, a screw accommodated in the cylinder, and a screw driving device that drives the screw while supporting the cylinder. The cylinder is heated to a temperature at which the thermosetting resin is not cured in the cylinder, and the screw is rotated. Then, the thermosetting resin melts and is fed to the front of the screw, and the screw moves backward. That is, the thermosetting resin is metered. When the screw is driven in an axial direction, a mold clamped by the mold clamping device is filled with the thermosetting resin. The mold is heated to cure the thermosetting resin. When the resin is cured, the mold is opened and a molded article is taken out.

SUMMARY

When the thermosetting resin is injected in a molding cycle, the screw is driven to a most forward position to inject the thermosetting resin into the mold to avoid occurrence of insufficient filling of the resin. However, if the most forward position is not appropriately adjusted, inconvenience occurs. For example, when the most forward position is not set sufficiently forward, even if the screw is driven to the most forward position, a large gap is formed between an inside of a nozzle provided at a tip end of the cylinder and a tip end portion of the screw, and an amount of remaining resin increases. Thus, the resin remains in the cylinder until a next molding cycle, which is not preferable in terms of quality. On the other hand, when the most forward position is adjusted forward, a tip end surface of the tip end portion of the screw comes into contact with a tip end inner surface inside the nozzle when the screw is driven to the most forward position.

Illustrative aspects of the present disclosure provide a screw adjustment method that can appropriately adjust a most forward position of a screw in a thermosetting resin injection molding machine, a thermosetting resin injection device in which a most forward position of a screw is appropriately adjusted, and a thermosetting resin injection molding machine. 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 screw adjustment method in a thermosetting resin injection molding machine including a cylinder having a nozzle at a tip end of the cylinder and a screw accommodated in the cylinder, the screw adjustment method including: contacting a screw and nozzle including bringing a tip end surface of the screw into contact with a tip end inner surface of an inner peripheral surface of the nozzle; moving the screw backward by a specified length after the contacting of the screw and the nozzle; and determining a screw position of the screw moved backward as a most forward position of the screw in a molding cycle.

According to the illustrative aspects of the present disclosure, the most forward position of the screw can be appropriately adjusted.

DETAILED DESCRIPTION

Hereinafter, specific embodiments will be described in detail with reference to the drawings. However, the present invention is not limited to the following embodiment. 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.

Illustrative Embodiment

As shown inFIG.1, a thermosetting resin injection molding machine1according to the illustrative embodiment includes a mold clamping device2, a thermosetting resin injection device3, and the like. As to be described in detail below, the mold clamping device2is of a vertical type in which a mold platen is vertically driven to open and close a mold. On the other hand, the thermosetting resin injection device3for injecting a thermosetting resin is of a horizontal type as to be described later. The thermosetting resin injection molding machine1includes a control device4for controlling these devices.

The mold clamping device2in the illustrative embodiment includes a fixed platen9fixed to a bed7, an upper movable platen10provided above the fixed platen9, and a lower movable platen11provided in the bed7. The upper movable platen10and the lower movable platen11are coupled by a plurality of, for example, four tie bars12,12. . . . A mold clamping mechanism is provided between the lower movable platen11and the fixed platen9. The mold clamping mechanism in the illustrative embodiment is implemented by a toggle mechanism14. An upper mold15is provided on the upper movable platen10, and a lower mold16is provided on the lower movable platen11. When the toggle mechanism14is driven, the upper mold15and the lower mold16are opened and closed. Although not shown in the figure, the upper mold15and the lower mold16are each provided with a temperature control device, temperatures of the upper mold15and the lower mold16are increased to cure the thermosetting resin.

The thermosetting resin injection device3is of a horizontal type. The thermosetting resin injection device3is provided on the bed7. The thermosetting resin injection device3includes a cylinder18provided horizontally, a screw19accommodated in the cylinder18, and a screw driving device21that supports the cylinder18and is configured to drive the screw19. The screw driving device21will be described in detail below. A nozzle23is provided at a tip end of the cylinder18. A hopper24is provided at a rear part of the cylinder18. When the nozzle23touches the molds15,16, an injection material made from the thermosetting resin can be injected to the molds15,16.

As shown inFIG.2, the screw driving device21includes a frame28. The frame28includes a front plate30, a rear plate31, and an injection plate32. The front plate30and the rear plate31are coupled by a plurality of, for example, four guide rods34,34. . . , and the injection plate32is penetrated by these guide rods34,34. . . . That is, the injection plate32is guided by the guide rods34,34. . . to move forward and backward. A hollow nose portion36is provided on the front plate30of the frame28. The cylinder18is fixed to the nose portion36by bolts or the like.

A rotating shaft38is provided in the injection plate32. The rotating shaft38is rotatably supported by the injection plate32at one end portion thereof. The rotating shaft38extends forward through the front plate30. The screw19is connected to the other end portion of the rotating shafts38via a coupling40. A plasticizing motor42is provided on the injection plate32. The plasticizing motor42is configured to rotate the rotating shaft38via a rotation transmission mechanism43. That is, when the plasticizing motor42rotates, the rotating shaft38and the screw19are rotated.

A ball screw mechanism45is provided between the injection plate32and the rear plate31. Specifically, a ball nut46is fixed to the injection plate32, and a ball screw47is rotatably provided on the rear plate31. An injection motor49is provided on the rear plate31, and rotates the ball screw47via a rotation transmission mechanism50. Accordingly, when the injection motor49rotates, the ball screw47is rotated and the ball screw mechanism45extends and contracts. That is, the injection plate32moves forward and backward, and the screw19moves forward and backward.

A load cell52is provided between the injection plate32and the ball nut46. Accordingly, an axial force acting on the screw19is detected. As to be described later, in a screw adjustment method according to the illustrative embodiment, a backward movement of the screw19is detected. The backward movement of the screw19can be detected based on a change in the axial force detected by the load cell52.

The injection motor49is provided with an encoder. A rotational position of the injection motor49is detected by the encoder. Accordingly, magnitude of extending and contracting of the ball screw mechanism45is detected, and a screw position of the screw19is detected. That is, a screw position detection unit is provided. The backward movement of the screw19may be detected by the screw position detection unit.

The screw adjustment method according to the illustrative embodiment will be described. The screw adjustment method according to the illustrative embodiment is an adjustment method for appropriately adjusting the most forward position of the screw19in the molding cycle. The most forward position is a screw position of the screw19at the time of completion of injection. When the screw19is adjusted to an appropriate most forward position, a specified gap is formed between a tip end inner surface of an inner peripheral surface of the nozzle23and a tip end surface of a tip end portion of the screw19at the time of completion of injection. An amount of the thermosetting resin remaining in the cylinder18at the time of completion of injection can be reduced, and heat generation due to contact between the tip end inner surface of the nozzle23and the tip end surface of the tip end portion of the screw19can be prevented, and quality deterioration of the thermosetting resin can be prevented. The specified gap is preferably from 0.4 mm to 0.7 mm. A tip end inner surface23aof the nozzle23and a tip end surface19aof the tip end portion of the screw19are shown inFIG.3A. In the illustrative embodiment, the tip end inner surface23ais formed in a conical concave surface, and the tip end surface19ais formed in a conical surface.

In the screw adjustment method according to the illustrative embodiment, first, the screw is moved backward (step S01), as shown inFIG.4. When the control device4(seeFIG.1) is operated, as shown inFIG.3A, the injection motor49is driven to move the screw19backward. Next, as shown inFIG.4, the nozzle is detached (step S02). As shown inFIG.3B, an operator detaches the nozzle23from the cylinder18. A male thread is formed on an outer peripheral surface of the nozzle23, and a female thread is formed on a tip end portion of the cylinder18. The nozzle23is rotated and detached. A reason why step S01is performed in advance is to prevent the tip end inner surface23aof the nozzle23and the tip end surface19aof the tip end portion of the screw19from colliding with each other and being damaged when the nozzle23is detached in step S02.

As shown inFIG.4, the screw is moved forward (step S03). When the control device4(seeFIG.1) is operated, as shown inFIG.3C, the injection motor49is driven to move the screw19forward. Accordingly, the tip end surface19aof the tip end portion of the screw19is exposed from the tip end of the cylinder18. The screw19moves forward such that the tip end surface19ais sufficiently exposed.

The control device4(seeFIG.1) is operated to select a screw adjustment mode. Then, the control device4automatically starts step S04to be described below. Predetermined steps are sequentially performed until the operator notifies the control device4of completion of the work after completion of step S08. When the screw adjustment mode is selected in the control device4, the control device4performs first axial force application (step S04). Specifically, the injection motor49starts torque control with a relatively small torque to generate a weak axial force in a forward direction, that is, a first axial force on the screw19. The first axial force is adjusted to, for example, about 100 N. This state is shown inFIG.3D.

In a state where the first axial force is applied to the screw19, the nozzle is attached (step S05) as shown inFIG.4. That is, as shown inFIG.3E, the operator attaches the nozzle23to the tip end of the cylinder18. The nozzle23may be attached by any means, but the nozzle23is preferably rotated by hand. This is because the nozzle23can be attached to the cylinder18with a relatively small torque at the beginning of the attachment, which is efficient. When the nozzle23is rotated, the tip end surface19aof the tip end portion of the screw19eventually comes into contact with the tip end inner surface23aof the nozzle23. Thus, a torque required to rotate the nozzle23temporarily increases. However, since the first axial force applied to the screw19is relatively small, the nozzle23can be slightly rotated. A state in which a small gap54is formed between the nozzle23and the cylinder18is shown.

As shown inFIG.4, the control device4monitors the backward movement of the screw19(step S06). The backward movement of the screw19can be detected by various methods. For example, a method is to detect a change in the axial force measured by the load cell52. Another method is to monitor the presence or absence of the backward movement of the screw19by monitoring the encoder of the injection motor49. When the tip end inner surface23aof the nozzle23comes into contact with the tip end surface19aof the tip end portion of the screw19, a change in the axial force is detected. When the nozzle23is rotated after the contact, the screw19is moved backward, which is detected by the encoder. The detection may be performed by any method. The control device4monitors the backward movement of the screw19and allows the operator to continue performing step S05while the backward movement is not detected (NO). When the backward movement of the screw19is detected (YES), the control device4performs the next step S07.

The control device4performs second axial force application (step S07). The torque control of the injection motor49is performed to increase the torque to a slightly higher torque, and a slightly larger axial force in the forward direction, that is, a second axial force is generated on the screw19. The second axial force is larger than the first axial force, and is adjusted to, for example, about 20 kN. This state is shown inFIG.3F. When the second axial force is applied to the screw19, the nozzle23cannot be rotated and tightened by hand. The operator tightens the nozzle23using a spanner (step S08). When the nozzle23is tightened in a state where the tip end inner surface23aof the nozzle23and the tip end surface19aof the tip end portion of the screw19are in contact with each other, the screw19is also moved backward due to the tightening of the nozzle23.

A graph ofFIG.5shows the axial force on the screw19detected in the load cell52in step S05to step S08. That is, when the nozzle23is attached by hand in a state where the first axial force is applied to the screw19first, an axial force close to the first axial force is detected in the load cell52. As the male thread of the nozzle23is tightened, the axial force increases as indicated by the reference numeral56. That is, the tip end inner surface23aof the nozzle23comes into contact with the tip end surface19aof the tip end portion of the screw19. As described above, the control device4switches to the second axial force. Thereafter, when tightening the nozzle23by the spanner, the nozzle23cannot be tightened eventually. That is, a state of reaching a tightening completion position is shown.

FIG.3Gshows a state in which the tightening of the nozzle23is completed and the tightening completion position is reached. The operator operates the control device4(seeFIG.1) to inform the control device4of the completion of the work. The control device4performs step S09as shown inFIG.4. That is, the screw is moved backward by a specified length. Specifically, the injection motor49is driven to move the screw19backward by a specified length. The specified length is preferably 0.4 mm to 0.7 mm, and is 0.5 mm, for example. This state is shown inFIG.3H. The backward movement length is indicated by the reference numeral58. The control device4stores a current screw position of the screw19as the most forward position. The screw adjustment mode is completed.

The control device4may perform a confirmation operation upon completion of the screw adjustment mode. Specifically, after step S09is completed, the injection motor49is driven to drive the screw19forward by a specified length59, as shown inFIG.3I. The injection motor49is driven to confirm the contact between the tip end inner surface23aof the nozzle23and the tip end surface19aof the tip end portion of the screw19. The contact is detected by the load cell52. After the confirmation, as shown inFIG.3H, the screw is moved backward by the specified length58. By performing such a confirmation operation, the position of the screw19can be adjusted more accurately. The control device4completes the screw adjustment mode.

The screw adjustment method according to the illustrative embodiment includes: a screw and nozzle contact step of bringing the tip end surface19aof the screw19into contact with the tip end inner surface23aof the nozzle23; and a screw specified-length backward movement step of moving the screw19backward by a specified length. Step S01to step S08described above correspond to the screw and nozzle contact step, and step S09corresponds to the screw specified-length backward movement step. With such a configuration, the screw adjustment method according to the illustrative embodiment is simple and excellent in adjustment. Since the nozzle23is attached and then tightened to the cylinder18while switching the axial force applied to the screw19in the screw and nozzle contact step in two stages, that is, the first and second axial forces, the contact between the tip end inner surface23aof the nozzle23and the tip end surface19aof the screw19is ensured. That is, it is ensured that the most forward position of the screw19can be accurately adjusted.

{Screw Adjustment Method According to Comparative Example}

Although being different from the screw adjustment method according to the illustrative embodiment, other methods of adjusting the most forward position of the screw19are also considered. In a screw adjustment method according to a comparative example, the most forward position can be adjusted as follows, for example. First, as shown inFIG.6A, the injection motor49is driven to move the screw19forward, and the tip end inner surface23aof the nozzle23and the tip end surface19aof the tip end portion of the screw19are brought into contact with each other. In this state, a stopper60is placed between the front plate30and the injection plate32to prevent the injection plate32from further moving forward. Alternatively, the stopper60may be provided on the front plate30to perform length adjustment of the stopper60. A screw position of the screw19at this time is set in the control device4(seeFIG.1) as the most forward position.

Next, as shown inFIG.6B, the coupling40is detached to separate the screw19from the rotating shaft38, and the cylinder18is detached from the nose portion36. A shim61is attached to the nose portion36from which the cylinder18is detached. Finally, as shown inFIG.6C, the cylinder18is attached to the nose portion36with the shim61interposed therebetween, and the screw19and the rotating shaft38are connected to the coupling40. The stopper60is detached. The screw adjustment method according to the comparative example is completed.

When the screw adjustment method according to the comparative example is performed, even if the screw19is moved forward to the most forward position set in the control device4, a gap between the tip end inner surface23aof the nozzle23and the tip end surface19aof the tip end portion of the screw19is secured by a thickness of the shim61. That is, as long as the thickness of the shim61is adjusted to the specified length, the most forward position can be appropriately adjusted. However, it is necessary to detach the cylinder18from the nose portion36, attach the shim61, and attach the cylinder18again, making the work complicated. It can be said that the screw adjustment method according to the illustrative embodiment is superior.

Modification to Illustrative Embodiments

The illustrative embodiment can be variously modified. For example, it has been described that the encoder of the injection motor49is used as the position detection unit of the screw19. However, by installing a magnetostrictive linear position sensor, for example, between the injection plate32and another plate, such as the front plate30, it becomes possible to detect the position of the screw19. Although it has been described that the nozzle23is attached to the cylinder18while the axial force acting on the screw19is switched in two stages, that is, the first and second axial forces, the axial force may be applied only in one stage. Alternatively, the axial force may be switched in three or more stages.

The mold clamping device2can also be modified. In the illustrative embodiment, it has been described that the mold clamping device2is of a vertical type, but may be of a horizontal type. Similarly, although it has been described that the thermosetting resin injection device3is of a horizontal type, but may be of a vertical type.

Although the invention made by the present inventors is specifically described based on the embodiments, it is needless to say that the present invention is not limited to the embodiments described above, and various modifications can be made without departing from the gist of the invention. The plurality of examples described above may be appropriately combined.