Molding method and injection molding machine system

Abstract

To provide a molding method capable of acquiring a molded article which has high quality, by properly filling a resin in a metal mold.SOLUTION: There is provided a molding method capable of filling a resin formed of a liquid thermosetting resin in metal molds (20, 21) whose temperature is set to a hardening temperature, for hardening the resin for acquiring a molded article. The method uses: an injection device (8) comprising, an injection cylinder (23) and a screw (24); and a resin supply unit (3) for supplying a resin to the injection cylinder (23). In a filling step for filling the resin in the metal molds (20, 21), there is provided a flow filling step S3 for rotating the screw (24) for feeding the resin, where a supply pressure of the resin from the resin supply device (3) is set to become great relative to a pressure in other steps.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a molding method and an injection molding machine system in which a liquid thermosetting resin is injected into a mold controlled at a curing temperature and cured to obtain a molded product. [Background technology]

[0002] When molding a molded product that is larger than the injection capacity of the injection unit of an injection molding machine, flow molding, as described in Patent Document 1, for example, is suitable. Flow molding includes a flow filling process in which a screw is rotated to feed the resin into a mold during the filling process in which the resin is filled into the mold. In the flow filling process, the resin is melted and fed into the mold by the rotation of the screw, so there is no restriction on the injection capacity that is determined by the stroke length of the screw. In other words, it is possible to fill the mold with an amount of resin that exceeds the injection capacity. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 6-210685

[0004] Although the molding method described in Patent Document 1 targets thermoplastic resins, flow molding can also be applied to liquid thermosetting resins. Specifically, a mold is controlled to a curing temperature, and a flow filling process in which the screw rotates is added to the filling process in which the resin is filled into the mold. The resin hardens within the mold. If necessary, an injection filling process in which the screw advances to fill the resin at the beginning and end may be performed. In other words, the filling process is performed in the following order: injection filling process, flow filling process, and injection filling process. This allows the resin to be properly filled into the mold and enables the molding of various molded products without being restricted by the injection capacity of the injection device. Summary of the Invention [Problem to be solved by the invention]

[0005] Even with liquid thermosetting resins, if a flow filling process is implemented in the filling process, molded products can be produced without being limited by injection volume. In particular, molded products made from silicone resins are often produced in small quantities and in a relatively wide variety of products, so the flow filling process, which is not limited by injection volume, is suitable. However, there are also issues that need to be resolved. Specifically, the flow filling process may not be able to achieve a sufficiently high resin filling speed or pressure, resulting in inadequate filling.

[0006] The present disclosure provides a molding method that allows resin to be properly filled into a mold to obtain a high-quality molded product, and an injection molding machine system that can implement such a molding method.

[0007] Other objects and novel features will become apparent from the description of this specification and the accompanying drawings. [Means for solving the problem]

[0008] The present disclosure relates to a molding method for filling a mold with a liquid thermosetting resin at a controlled curing temperature, followed by curing the resin to obtain a molded product. This molding method uses an injection device equipped with an injection cylinder and a screw installed within the injection cylinder, and a resin supply device that supplies the resin to the injection device. The present disclosure also provides a flow filling process in which the screw is rotated to deliver the resin during the filling process for filling the mold with resin, and controls the supply pressure of the resin from the resin supply device to be higher during the flow filling process than during other processes. [Effects of the Invention]

[0009] The present disclosure makes it possible to properly fill a mold with resin and obtain a high-quality molded product. [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a front view showing an injection molding machine system according to an embodiment of the present invention; [Figure 2] 3 is a flowchart of a molding method according to the present embodiment. [Figure 3] 4 is a graph showing changes in injection speed, screw rotation speed, resin supply pressure, and injection pressure when the molding method according to the present embodiment is carried out. [Figure 4] 6 is a graph showing the changes in injection speed, screw rotation speed, resin supply pressure, and injection pressure when a molding method according to a second embodiment is carried out. DETAILED DESCRIPTION OF THE INVENTION

[0011] Specific embodiments will be described in detail below 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 as appropriate. In each drawing, the same elements are given the same reference numerals, and duplicate explanations are omitted as necessary. Furthermore, hatching has been omitted in some areas to avoid cluttering the drawings.

[0012] The present embodiment will be described. <Injection molding machine system> The injection molding machine system 1 according to this embodiment is a system for molding a molded product using a resin made of a liquid thermosetting resin. As shown in Fig. 1, the injection molding machine system 1 includes an injection molding machine 2, a resin supplying device 3 that supplies resin to the injection molding machine 2, and a mold temperature adjusting device 4 that supplies a heat medium to molds 20 and 21 (described later) to heat them.

[0013] <Injection molding machine> The injection molding machine 2 includes a mold clamping device 7 provided on the bed B, an injection device 8 also provided on the bed B, and a control device 10 that controls these. The control device 10 controls not only the injection molding machine 2, but also the resin supply device 3 and the mold temperature adjustment device 4.

[0014] <Mold clamping device> The mold clamping device 7 includes a fixed platen 12 fixed to a bed B, a movable platen 13 slidably provided on the bed B, and a mold clamping housing 14 similarly slidably provided on the bed B. The fixed platen 12 and the mold clamping housing 14 are connected by a plurality of tie bars 16, 16, ..., and the movable platen 13 is slidably provided between the fixed platen 12 and the mold clamping housing 14. A mold clamping mechanism, that is, a toggle mechanism 18 in this embodiment, is provided between the mold clamping housing 14 and the movable platen 13. A fixed mold 20 and a movable mold 21 are provided on the fixed platen 12 and the movable platen 13, respectively. Therefore, when the toggle mechanism 18 is driven, these molds 20, 21 are opened and closed.

[0015] <Injection device> The injection device 8 includes an injection cylinder 23, a screw 24 provided in the injection cylinder 23, and a screw drive device 25. The injection cylinder 23 is supported by the screw drive device 25, and the screw 24 is driven in the rotational direction and the axial direction by the screw drive device 25. An injection nozzle 27 is provided at the tip of the injection cylinder 23 and is in contact with the fixed mold 20. In this embodiment, the resin supply device 3 is connected to the injection cylinder 23, and a liquid thermosetting resin is supplied into the injection cylinder 23.

[0016] <Resin supply device> The injection molding system 1 according to this embodiment is configured to mold molded products using a resin made of a so-called two-component silicone resin. Therefore, in this embodiment, the resin supply device 3 is a two-component silicone resin supply device. Although not shown in FIG. 1, the resin supply device 3 includes a container for a base resin, a container for a hardener, pumps for each of these containers, and a mixer for mixing the base resin and hardener delivered by the pumps in a predetermined ratio. The resin supply device 3 according to this embodiment is configured to control the pump output in response to commands from the control device 10, thereby varying the supply pressure of the resin delivered into the injection cylinder 23.

[0017] <Mold temperature control device> The mold temperature adjusting device 4 is configured to supply a heat medium such as oil to the molds 20, 21. The mold temperature adjusting device 4 is controlled by the control device 10, and is configured to control the molds 20, 21 to a curing temperature at which the silicone resin cures, for example, 120 to 180°C.

[0018] <Forming method> The molding method according to this embodiment will be described below. First, the state where the resin has been metered into the injection cylinder 23, i.e., the standby state, will be described. Also, it is assumed that the molds 20 and 21 are adjusted to a curing temperature at which the resin will harden by the control device 10 controlling the mold temperature adjustment device 4.

[0019] As shown in Fig. 2, the control device 10 first performs the mold clamping step S1. That is, the mold clamping device 7 clamps the molds 20 and 21. In the graph of Fig. 3, the mold clamping step S1 is included in the standby state. At this time, the control device 10 controls the resin supply device 3 (see Fig. 1) to maintain the resin pressure, i.e., the resin supply pressure, low as indicated by the reference numeral 31.

[0020] Next, the control device 10 carries out a filling step in which resin is filled into the molds 20, 21. In this embodiment, the filling step consists of three steps. First, the first injection filling step S2 is carried out. In the injection device 8 (see Figure 1), the screw 24 is advanced in the axial direction. The screw 24 is provided with a backflow prevention device (not shown), and the resin is delivered as the screw 24 advances. In Figure 3, the forward speed of the screw 24, i.e., the injection speed, is indicated by the symbol 32.

[0021] In the molding method according to this embodiment, the control device 10 controls the resin supply device 3 to increase the resin supply pressure, as indicated by the reference numeral 33, simultaneously with the start of the first injection filling step S2. This allows the resin delivered from the injection cylinder 23 to the molds 20 and 21 during the first injection filling step S2 to be quickly replenished, and also increases the resin filling speed and filling pressure during the flow filling step S3, which will be described next. A cavity and a gate are formed within the molds 20 and 21. When the screw position of the screw 24 reaches a preset position, the control device 10 stops the advancement of the screw 24, thereby completing the first injection filling step S2. This screw position is the position where the tip of the resin reaches the gate, or where a predetermined amount of resin has been filled into the cavity. The injection speed returns to zero.

[0022] As shown in FIG. 2, after the first injection filling step S2 is completed, the control device 10 promptly performs the flow filling step S3. In the flow filling step S3, the screw 24 of the injection device 8 (see FIG. 1) is rotated while maintaining the screw position, and the resin is dispensed. The screw rotation speed is indicated by reference numeral 34 in FIG. 3. The resin supply pressure is controlled to a high level, as indicated by reference numeral 33 in FIG. 3. Silicone resin, which has a low viscosity, is efficiently dispensed by a high resin supply pressure. In other words, the resin filling speed and filling pressure into the cavities of the molds 20 and 21 can both be increased, resulting in efficient filling. As indicated by reference numeral 35 in FIG. 3, it can be seen that the resin filling pressure is high in the flow filling step S3.

[0023] The resin supply pressure to be set in the flow filling process S3 may be changed depending on the type of resin used. For example, it may be possible to set a higher resin supply pressure for a resin with a relatively high viscosity. Once a predetermined amount of resin has been filled into the cavity, the rotation of the screw 24 is stopped. This completes the flow filling process S3.

[0024] The control device 10 then carries out the second injection filling step S4 as shown in FIG. 2. That is, the screw 24 in the injection device 8 (see FIG. 1) is advanced axially to deliver the resin. The screw speed of the screw 24, i.e., the injection speed, is indicated by reference numeral 36. As the resin is filled by advancing the screw 24, the filling pressure increases as indicated by reference numeral 37 in FIG. 3. Therefore, the resin is properly filled into every corner of the cavities in the molds 20 and 21. Once the resin has been fully filled into the cavities, the advancement of the screw 24 is stopped. That is, the second injection filling step S4 is completed. The three-step filling process is then completed.

[0025] The control device 10 performs the pressure holding step S5 as shown in Figure 2. In the pressure holding step S5, the screw 24 is not rotated but is moved back and forth to control the pressure. The resin supply pressure from the resin supply device 3 is maintained high as shown in Figure 3. As the resin hardens inside the molds 20 and 21, sink marks can be prevented.

[0026] Next, the control device 10 performs the metering step S6. In the metering step S6, the screw 24 is rotated to accumulate the resin in front of the injection cylinder 23. In other words, the resin is metered. At this time, the control device 10 controls the resin supply device 3 to reduce the resin supply pressure, as indicated by reference numeral 38 in FIG. 3. However, the resin supply pressure is set to be higher than the pressure during standby. This allows the resin to be efficiently sent forward and metered in a short time. In FIG. 3, the screw speed of the screw 24 retracting during metering is indicated by reference numeral 40, and the number of rotations of the screw 24 is indicated by reference numeral 41. When the screw position of the screw 24 reaches a specified position, the rotation of the screw 24 is stopped, and the metering step S6 is completed.

[0027] Once the metering step S6 is complete, the control device 10 controls the resin supply device 3 to reduce the resin supply pressure. In other words, it is put into a standby state. In this embodiment, the resin supply pressure is reduced in the standby state, thereby preventing the occurrence of resin leakage, etc. By the way, when the metering step S6 is complete, the resin in the molds 20, 21 has already hardened. As shown in Figure 2, the mold opening / ejection step S7 is carried out. That is, the control device 10 drives the mold clamping device 7 (see Figure 1) to open the mold. Then, an ejection device (not shown) is driven to eject the molded product. The control device 10 moves on to the next molding cycle. That is, as shown in Figure 2, the process returns to the mold clamping step S1.

[0028] <Comparison with other related methods> As a comparative example, consider a case where the resin supply pressure by the resin supply device 3 is controlled constant during the molding cycle. The resin supply pressure when the molding cycle is performed using this method is indicated by reference numeral 45 in FIG. 3. When the molding cycle is performed, the filling pressure becomes low during the flow filling step S3, as indicated by reference numeral 46. Therefore, the filling speed into the molds 20 and 21 is low, and the time required for filling is long. Furthermore, because the filling pressure is low, there is a possibility that the cavity will not be properly filled. Furthermore, because the resin supply pressure is lower during the metering step S6 than in the molding method according to this embodiment, the time required for metering is long. On the other hand, because the resin supply pressure is not sufficiently low during the standby state, there is a risk of resin leakage. In contrast to this comparative example, the molding method according to this embodiment changes the resin supply pressure during the molding cycle, thereby solving all of these problems.

[0029] <Second embodiment> This embodiment can be modified in various ways. For example, the molding method can be modified. FIG. 4 shows changes in the injection speed, screw rotation speed, resin supply pressure, etc. when carrying out the molding method of the second embodiment. The molding method of the second embodiment differs from the first embodiment in several respects. First, the injection speed is controlled to be slightly lower in the second injection filling step S4, as indicated by the reference numeral 45. By lowering the resin filling speed, it is possible to prevent the resin from leaking out of the cavities in the molds 20 and 21 and causing flash.

[0030] Next, the screw rotation speed is changed in three stages in the flow filling step S3, as indicated by the reference numerals 46, 47, and 48. If the molded product to be molded has a shape such as a constriction and it is preferable to reduce the resin flow rate, this can be achieved by changing the screw rotation speed.

[0031] In this embodiment, the resin supply pressure is controlled to a low level in the first injection filling step S2 and then increased in the flow filling step S3. However, in the flow filling step S3, the resin supply pressure is changed in three stages, as indicated by reference numerals 50, 51, and 52. This is synchronized with changes in the screw rotation speed, as indicated by reference numerals 46, 47, and 48, and the flow rate during resin filling is adjusted according to the shape of the molded product. In the second injection filling step S4, the resin supply pressure is slightly increased, as indicated by reference numeral 53, to ensure proper filling of the cavity.

[0032] <Other variations> Other variations are possible. The resin used in this embodiment has been described as a two-component silicone resin. However, a one-component silicone resin can also be used. In this case, the resin supply device 3 (see FIG. 1) should be designed to accommodate the one-component type. Furthermore, other resins than silicone resin may be used as long as they are liquid thermosetting resins. The mold temperature adjustment device 4 can also be varied. The mold temperature adjustment device 4 can be configured from a heater embedded in the molds 20, 21 and a power device that supplies power to this heater.

[0033] The filling process can also be modified. In this embodiment, the filling process has been described as consisting of three steps: the first injection filling step S2, the flow filling step S3, and the second injection filling step S4. However, the filling process can also be composed of two steps by omitting either the first or second injection filling step S2 or S4. Alternatively, the filling process can be composed of four or five or more steps by adding a filling step using another method after the second injection filling step S4.

[0034] The invention made by the inventor has been specifically described above based on the embodiments, but it goes without saying that the present invention is not limited to the above-described embodiments and various modifications are possible without departing from the spirit of the invention. The multiple examples described above can also be implemented in appropriate combinations. [Explanation of symbols]

[0035] 1 Injection molding machine system 2 Injection molding machine 3 Resin supply device 4 Mold temperature control device 7 Mold clamping device 8 Injection device 10 control device 12 stationary platen 13 Movable platen 14 Mold clamping housing 16 Tie bar 18 Toggle mechanism 20 Fixed side mold 21 Movable side mold 23 Injection cylinder 24 Screw 25 Screw drive device 27 Injection nozzle

Claims

1. A molding method in which a liquid thermosetting resin is filled into a mold controlled at a curing temperature, and cured to obtain a molded product, comprising: An injection device including an injection cylinder and a screw provided in the injection cylinder, and a resin supply device for supplying resin to the injection device are used, The filling step of filling the resin into the mold includes a flow filling step of rotating the screw to feed out the resin, A molding method in which the supply pressure of the resin from the resin supply device is controlled to be higher in the flow filling step than in other steps.

2. the filling step includes an injection filling step of advancing the screw in the injection cylinder to feed out the resin, 2. The molding method according to claim 1, wherein the filling step comprises a first injection filling step which is the injection filling step, a subsequent flow filling step, and a subsequent second injection filling step which is the injection filling step.

3. 3. The molding method according to claim 1, wherein a supply pressure of the resin supplied from the resin supply device in the flow filling step is changed while the resin is being filled into the mold in accordance with a shape of the molded product.

4. 3. The molding method according to claim 1, wherein a supply pressure of the resin supplied from the resin supply device in the flow filling step is changed depending on the type of resin.

5. The molding method includes a metering step of retracting the screw within the injection cylinder to meter a resin into the injection cylinder, 3. The molding method according to claim 1, wherein the supply pressure of the resin supplied from the resin supply device is reduced after the metering step is completed.

6. 3. The molding method according to claim 1, wherein the liquid thermosetting resin is a silicone resin.

7. an injection molding machine including a mold clamping device that clamps a mold and an injection device that fills the mold with a resin made of a liquid thermosetting resin; a mold temperature control device that controls the mold to a curing temperature; a resin supply device that supplies resin to the injection device; a control device; the injection device includes an injection cylinder and a screw provided in the injection cylinder, and the resin from the resin supply device is supplied to the injection cylinder; the control device controls the injection device to carry out a filling step of filling the mold with resin, and the filling step includes a flow filling step of rotating the screw to feed out the resin, The control device controls the supply pressure of the resin supplied from the resin supply device in the flow filling process so that the supply pressure is higher than in other processes.

8. the filling step includes an injection filling step of advancing the screw in the injection cylinder to feed out the resin, 8. The injection molding machine system according to claim 7, wherein the control device performs the filling process including a first injection filling process which is the injection filling process, the flow filling process which is subsequently performed, and a second injection filling process which is the injection filling process which is subsequently performed.

9. 9. The injection molding machine system according to claim 7, wherein the control device changes a supply pressure of the resin supplied from the resin supply device during the flow filling step while the resin is being filled into the mold in accordance with a shape of the molded product.

10. 9. The injection molding machine system according to claim 7, wherein the control device changes a supply pressure of the resin supplied from the resin supply device in the flow filling step depending on the type of resin.

11. 9. The injection molding machine system according to claim 7, wherein the control device performs a metering step of retracting the screw within the injection cylinder to meter resin into the injection cylinder, and reduces a supply pressure of the resin supplied from the resin supply device after completion of the metering step.

12. 9. The injection molding machine system according to claim 7, wherein the liquid thermosetting resin is a silicone resin.

Images