JP7165167B2 - Injection molding machine and injection molding method - Google Patents

Description

TECHNICAL FIELD The present invention relates to an injection molding machine and an injection molding method for performing molding by injecting and filling a resin with a predetermined injection pressure into a mold clamped with a predetermined clamping force.

Conventionally, an injection molding machine performs molding by injecting and filling resin at a predetermined injection pressure from an injection device into a mold consisting of a fixed mold and a movable mold which are clamped with a predetermined mold clamping force by a mold clamping device. Widely known. On the other hand, the present applicant has proposed a molding mode using a general molding method, that is, a mold in which the mold positions of the movable mold and the fixed mold are fixed on the mold clamping device side. We have already proposed an injection molding machine equipped with a specific molding mode based on a new molding method different from the molding mode in which injection filling is performed inside, and this injection molding machine (molding method) is disclosed in Patent Document 1. ing.

This injection molding machine (molding method) ensures high quality and homogeneity of molded products even with low-viscosity resins that are sensitive to temperature, pressure, etc., and uses simple molding conditions. The purpose is to improve mass productivity and economic efficiency by making it easier and easier to set up, further facilitating quality control, and shortening the molding cycle time. Specifically, As a mold clamping device, a mold clamping device that enables natural compression of the resin at least as the resin in the mold solidifies is used. The molding injection pressure and mold clamping force that enable good product molding are found and set, and during production, the mold clamping device is clamped by the mold clamping force, and the molding injection pressure is set as the limiter pressure to drive the injection device. Then, the resin is injected and filled into the mold.

International publication WO2011/161899

However, conventional injection molding machines, including the injection molding machine having the above-described specific molding mode, have the following problems to be solved.

That is, when a molded product is produced by an injection molding machine, molding is usually performed by setting various molding conditions such as injection speed, injection pressure, resin temperature, etc. that match the type of molded product. Molding defects may occur to some extent in the resulting molded product, and there are also molded products which are susceptible to molding defects, depending on the type of the molded product. For example, molding using recycled pellet materials that tend to have uneven pellet shapes compared to ordinary pellets due to the inclusion of crushed materials, etc. In particular, molded products with a large injection volume that require a large amount of plasticization at one time are prone to molding defects and a decrease in the yield rate (good product rate).

For this reason, conventionally, it has been dealt with by setting highly accurate settings for various molding conditions and stabilizing control. However, even if such measures are taken sufficiently, a considerable number of molding defects occur at actual production sites, and the specific cause of defects is not always known. Not a little, there was a limit to ensuring a high yield rate.

In particular, the problem of not being able to secure a high yield rate not only leads to a decrease in production efficiency and an increase in production costs in the production of large molded products and special resin molded products, but also causes resource loss and wasteful energy consumption. As a result, there has been a demand for the realization of a new injection molding method (injection molding machine) to further increase the so-called marginal yield rate of the conventional method.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an injection molding machine and an injection molding method that solve the problems existing in the background art.

In order to solve the above-described problems, an injection molding machine M according to the present invention includes a mold clamping device Mc that clamps a mold 2 consisting of a fixed mold 2c and a movable mold 2m with a predetermined mold clamping force; When constructing an injection molding machine equipped with an injection device Mi that injects and fills the mold 2 with a resin under a predetermined injection pressure, the screw 4 accommodated in the heating cylinder 3 of the injection device Mi is moved forward. At the same time, the resin R in front of the screw head portion 4s at the front end portion of the mold 2 is injected and filled, and at the same time, the resin selected in the range of 10 to 60 [%] with respect to the volume of the resin R is used as the return resin Rm. A partial return injection function part 5 is provided to cause the return to the screw main body 4m side behind the screw head part 4s through the inner side of the screw head part 4s and/or the outer peripheral part side of the screw head part 4s. .

On the other hand, in the injection molding method according to the present invention, in order to solve the above-described problems, for the mold 2 composed of the fixed mold 2c and the movable mold 2m clamped with a predetermined mold clamping force by the mold clamping device Mc, When resin is injected and filled at a predetermined injection pressure by the injection device Mi to perform molding, the screw 4 housed in the heating cylinder 3 of the injection device Mi is moved forward so that the front end portion of the screw 4 is positioned in front of the screw head portion 4s. of the resin R is injected into the mold 2, and at the same time, a resin selected in the range of 10 to 60 [%] with respect to the volume of the resin R is injected into the inside of the screw head portion 4s and/or It is characterized by flowing back to the screw main body 4m side behind the screw head portion 4s through the outer peripheral portion side of the screw head portion 4s.

Further, according to a preferred embodiment of the present invention, when configuring the partial recirculation injection function part 5, the screw head part 4s is provided with at least one recirculation passage 11 through which the resin Rm is recirculated. , the injection pressure additional setting function part Fs for setting the injection pressure Pis at the time of molding higher than the injection pressure Pi when the resin Rm does not flow back by a predetermined amount. A reverse rotation control function unit Fc for reverse rotation may be provided, and more preferably, the reverse rotation control function unit Fc may be provided with a reverse rotation setting function unit Fcs for the period during which the screw 4 is reversely rotated and the rotation speed. . On the other hand, when the injection molding method is carried out, at least a mold clamping device Mc is used as the mold clamping device, which enables natural compression of the resin R as the resin R in the mold 2 solidifies. A predetermined mold gap Lm is generated between the mold 2m and the fixed mold 2c, and an injection pressure (hereinafter referred to as molding injection pressure) Pi and a mold clamping force (hereinafter referred to as mold clamping force) Pc which are capable of molding a non-defective product are obtained. At the time of molding, the mold clamping device Mc is clamped by the mold clamping force Pc, the molding injection pressure Pi is set as the limiter pressure Ps, and the injection device Mi is driven to inject the resin into the mold 2. It is desirable to apply it to a molding method that performs filling.

According to the injection molding machine M and the injection molding method according to the present invention, the following remarkable effects can be obtained.

(1) By moving forward the screw 4 housed in the heating cylinder 3 of the injection device Mi, the resin R in front of the screw head portion 4s at the front end portion of the screw 4 is injected and filled into the mold 2, and at the same time, the resin R is injected. A predetermined amount of the recirculated resin Rm, which becomes a part, is recirculated to the screw main body 4m behind the screw head 4s through the inner side of the screw head 4s and/or the outer peripheral side of the screw head 4s. , the yield rate of the final molded product can be significantly increased, and in particular, it can be provided as a new injection molding method (injection molding machine) capable of further increasing the conventional, so to speak, marginal yield rate. As a result, it becomes possible to improve production efficiency and reduce production costs in the production of large-sized molded products and special resin molded products, effectively contributing to avoidance of resource loss and wasteful energy consumption.

(2) Since the amount (predetermined amount) of the circulating resin Rm is selected in the range of 10-60 [%] with respect to the volume of the resin R injected and filled into the mold 2, production efficiency and yield in the production of molded products It is possible to balance the ratios well. As a result, it is possible to optimize both from the viewpoints of securing production efficiency and securing a yield rate.

(3) If at least one circulation passage 11 through which the resin Rm circulates is provided in the screw head portion 4s when configuring the partial circulation injection function portion 5 according to a preferred embodiment, the screw head portion 4s can be changed or Since it can be realized by additional processing, etc., it can be implemented easily and at low cost, and it can be implemented as a form with excellent versatility, such as being easily applicable to existing injection molding machines.

(4) According to a preferred embodiment, when configuring the partial recirculation injection function unit 5, the injection pressure Pis during molding is set higher than the injection pressure Pi when the resin R does not recirculate by a predetermined amount. If the additional pressure setting function section Fs is provided, the amount of the recirculating resin Rm (recirculation amount) can be arbitrarily set by the additional injection pressure setting function section Fs even when the recirculation passages 11 are provided. In addition, it is possible to easily set the recirculation amount, and to avoid affecting the original amount (filling amount) of the resin R to be injected and filled into the mold 2 .

(5) According to a preferred embodiment, if the reverse rotation control function section Fc for rotating the screw 4 in the reverse direction is provided when configuring the partial return injection function section 5, the screw 4 itself does not need to be modified in terms of form. As a result, it becomes possible to realize the circulation by the control processing for the screw 4, and it is possible to further facilitate the implementation and further improve the versatility.

(6) According to a preferred embodiment, when configuring the reverse rotation control function unit Fc, if a reverse rotation setting function unit Fcs for setting the period and rotation speed for reverse rotation of the screw 4 is provided, the recirculation amount of the recirculation resin Rm can be controlled. , can be set by the reverse rotation setting function unit Fcs, so that an arbitrary reflux amount can be easily set, and the influence on the original filling amount to be injected and filled into the mold 2 can be avoided.

(7) According to a preferred embodiment, when the injection molding method is carried out, at least a mold clamping device Mc is used as the mold clamping device, which enables natural compression of the resin R in the mold 2 as the resin R solidifies. At the time of injection filling, a predetermined mold gap Lm is generated between the movable mold 2m and the fixed mold 2c, and the molding injection pressure Pi and the mold clamping force Pc that enable the molding of a non-defective product are determined and set. It should be applied to a molding method in which the mold clamping device Mc is clamped by the mold clamping force Pc, the molding injection pressure Pi is set as the limiter pressure Ps, and the injection device Mi is driven to inject and fill the mold 2 with resin. For example, the injection molding method according to the present invention can be applied to a specific molding mode that does not have a weighing process, that is, a specific molding mode that is hardly affected by the state of the injection device Mi, so that production efficiency can be improved and production costs can be improved. can be implemented as an optimal form from the viewpoint of contributing to the reduction of resource loss and the avoidance of wasteful energy consumption.

An overall configuration diagram of an injection molding machine according to a preferred embodiment of the present invention, A cross-sectional side view showing a part of an injection device provided in an injection molding machine according to the first example of the embodiment (virtual line circle A part in FIG. 1), A bar graph showing the injection molding method using the same injection molding machine and the magnitude of various physical quantities when there is no reflux. A flow chart for explaining the molding procedure by the injection molding method using the same injection molding machine, Explanatory diagram showing the behavior of the resin in the plasticization process by the same injection molding method, Explanatory diagram showing the behavior of the resin in the molding process by the same injection molding method, Relationship diagram of time versus mold gap in the molding process by the same injection molding method, Comparison chart of standard deviation values showing variation in mold displacement amount due to the same injection molding method and variation in mold displacement amount in the case of no reflux; A cross-sectional side view showing a part of the injection device provided in the injection molding machine according to the second example of the embodiment (virtual line circle A part in FIG. 1), Detailed step diagram of step SN in FIG. 4 for explaining the molding procedure by the injection molding method using the same injection molding machine, Relational diagram of screw reverse rotation and reflux amount when using the same injection molding method, FIG. 2 is a cross-sectional side view showing a part of an injection device according to each modification of the first example and the second example of the same embodiment (virtual line circle A portion in FIG. 1);

Next, preferred embodiments according to the present invention will be presented and explained in detail based on the drawings.

First, an overall main configuration of an injection molding machine M according to this embodiment will be described with reference to FIG.

In FIG. 1, M is an injection molding machine, which includes an injection device Mi and a mold clamping device Mc. The injection device Mi includes a heating cylinder 3 having an injection nozzle 3n at its front end and a hopper 21 at its rear part. A portion 23 is provided. The screw drive unit 23 includes an injection cylinder (hydraulic cylinder) 24 containing a single-rod type injection ram 24r. A shaft of a metering motor (oil motor) 25 attached to the injection cylinder 24 is spline-connected to the rear end of the injection ram 24r. Reference numeral 26 denotes an injection device moving cylinder that advances and retreats the injection device Mi to touch the mold 2 or cancel the nozzle touch. As a result, the injection device Mi can bring the injection nozzle 3n into contact with the mold 2 and inject and fill the cavity of the mold 2 with the melted (plasticized) resin R (FIG. 5).

On the other hand, the mold clamping device Mc is a direct pressure type hydraulic mold clamping device that displaces the movable mold 2m by a driving ram 27r of a mold clamping cylinder (hydraulic cylinder) 27. As shown in FIG. The mold clamping device Mc includes a stationary platen 28 fixed in position and spaced apart, and a movable platen slidably mounted on a plurality of tie bars 29 constructed between the fixed platen 28 and the mold clamping cylinder 27. 30. The tip of the ram rod 27rs protruding forward from the mold clamping cylinder 27 is fixed to the movable platen 30. As shown in FIG. A fixed mold 2c is attached to the fixed platen 28, and a movable mold 2m is attached to the movable platen 30. The mold 2 is composed of the fixed mold 2c and the movable mold 2m. As a result, the mold clamping cylinder 27 can open, close and clamp the mold 2 . In this case, since the mold clamping device Mc uses a mold clamping cylinder (hydraulic cylinder) 27, the mold clamping device Mc can at least naturally compress the resin R in the mold 2 as the resin R solidifies. be.

On the other hand, the injection molding machine M has a hydraulic circuit 35 shown in FIG. A pump circuit 38 is provided. Since the hydraulic pump 36 incorporates a swash plate (not shown), increasing the inclination angle (swash plate angle) of the swash plate increases the stroke of the pump piston, thereby increasing the discharge flow rate. A smaller angle reduces the stroke of the pump piston and can reduce the discharge flow rate. Therefore, by setting the swash plate angle to a predetermined angle, it is possible to set a fixed discharge flow rate in which the discharge flow rate (maximum displacement) is fixed at a predetermined value.

The discharge port of the hydraulic pump 36 is connected to the primary side of the valve circuit 37, and the secondary side of the valve circuit 37 is connected to the injection cylinder 24, metering motor 25, mold clamping cylinder 27, and ejector of the injection molding machine M. It connects to the cylinder 31 and the injection unit moving cylinder 26 . Therefore, the valve circuit 37 includes switching valves (electromagnetic valves) connected to the injection cylinder 24, the metering motor 25, the mold clamping cylinder 27, the ejector cylinder 31 and the injection device moving cylinder 26, respectively. Each switching valve is composed of one or more valve parts and necessary auxiliary hydraulic parts. It has a switching function for supplying, stopping, and discharging hydraulic oil to the cylinder 26 .

The pump circuit 38 can vary the discharge flow rate and discharge pressure by controlling the pump motor (servo motor) of the variable discharge hydraulic pump 36. Based on this, the injection cylinder 24, metering motor 25, The mold clamping cylinder 27, the ejector cylinder 31, and the injection device moving cylinder 26 can be driven and controlled, and each operation process in the molding cycle can be controlled. In this way, by using the variable discharge hydraulic pump 36 that can set a fixed discharge flow rate by changing the swash plate angle, the pump capacity can be set to a fixed discharge flow rate (maximum capacity) of a predetermined size, and a fixed discharge flow rate can be set. Since the discharge flow rate and discharge pressure can be varied based on the flow rate, easy and smooth control can be performed.

Furthermore, the injection molding machine M has a control system 41 shown in FIG. This control system 41 has a control function for executing molding processing in a specific molding mode. In this specific molding mode, a predetermined mold gap Lm is generated between the movable mold 2m and the fixed mold 2c at the time of injection and filling, and the molding injection pressure Pi and the mold clamping force Pc that enable the molding of a non-defective product are obtained in advance. At the time of molding, the mold clamping device Mc is clamped by the mold clamping force Pc, the molding injection pressure Pi is set as the limiter pressure Ps, and the injection device Mi is driven to inject the resin R into the mold 2. It becomes a molding method that performs filling.

The control system 41 includes a molding machine controller 42 having a molding machine controller body 42c and a display 42d attached to the molding machine controller body 42c. The molding machine controller main body 42c has a computer function including hardware such as a CPU and an internal memory. ) and a data area 42md capable of storing various data (databases). Therefore, the program area 42mp stores software for executing the specific molding mode described above, and can function as the specific molding mode function unit Fa.

The display 42d has a display main body 42dd and a touch panel 42dt attached to the display main body 42dd. The display main body 42dd and the touch panel 42dt are connected to the molding machine controller main body 42c via a display interface (not shown). Therefore, various setting operations and selection operations can be performed by the touch panel 42dt.

Furthermore, various sensors 43 including at least a mold gap sensor for detecting the mold gap Lm, and various switches 44 are connected to the molding machine controller main body 42c, and the pump circuit 38 and valve circuit 37 described above are also connected. do.

Next, the configuration and functions of the main parts of the injection molding machine M according to this embodiment will be specifically described with reference to FIGS. 1 to 12. FIG.

The injection molding machine M according to the present embodiment has, in addition to the main components described above, a partial recirculation injection function unit 5, which constitutes the main part of the present invention, that is, a screw 4 housed in a heating cylinder 3 of the injection device Mi. By moving the screw 4, the resin R in front of the screw head portion 4s at the front end portion of the screw 4 is injected and filled into the mold 2. A partial return injection function part 5 is provided to return the liquid to the screw main body 4m side behind the screw head part 4s through the inner side and/or the outer peripheral part side of the screw head part 4s.

For this reason, as shown in FIG. 1, the molding machine controller 42 partially stores software for operating the recirculation injection function unit 5. This software controls the injection pressure additional setting function unit Fs, which will be described later. The reverse rotation control function part Fc and the reverse rotation setting function part Fcs can be made to function.

Hereinafter, an injection molding machine M having a partial recirculation injection function unit 5, which is a main part of the present invention, will be described with reference to a first embodiment and a second embodiment.

First embodiment

First, the configuration of the partial recirculation injection function unit 5 provided in the injection molding machine M according to the first embodiment will be described with reference to FIGS. 1 to 3. FIG.

FIG. 2 is a part of the injection device Mi in the injection molding machine M shown in FIG. 1 shows part of an injection device Mi.

In FIG. 2, 4 is a screw having a spiral screw flight 4f on the peripheral surface of the screw main body 4m and a screw head 4s at the front end of the screw 4. As shown in FIG. The exemplified screw head portion 4s has a conical tip portion 4sc at the front end, and the rear end surface of the conical tip portion 4sc is connected to the front end surface of the screw main body portion 4m via the mounting shaft portion 4sj arranged in the axial direction Ds. A cylindrical check valve portion 4sn movable back and forth is arranged between the conical tip portion 4sc and the screw body portion 4m.

The function of the check valve in the molding mode of a general injection molding machine is as follows. First, in the weighing process, resin is weighed by moving from the screw main body side to the front of the screw head, so the check valve moves forward to the open position as the resin moves. That is, forward movement of the resin is permitted. Also, in the injection process, the metered resin pressure acts backward, so the check valve moves backward to the closed position. As a result, the backward flow of the resin is blocked by the check valve. Therefore, the shape of the check valve is cylindrical, and the outer peripheral surface of the check valve is in contact with the inner peripheral surface of the heating cylinder, leaving almost no gap. , the resin passage through which the resin can flow is blocked.

On the other hand, in the injection molding machine M according to the first embodiment of the present invention, as shown in FIG. 2, the check valve portion 4sn is formed in a cylindrical shape as a whole, and the circulating resin Rm is formed on the outer peripheral surface of the check valve portion 4sn. At least one return passage 11 passing backward, in the case of the example, a plurality of return passages 11 arranged at regular intervals in the circumferential direction were formed. If such a circulation passage 11 is provided, it can be realized by changing or adding processing to the screw head portion 4s, so that it can be implemented easily and at low cost, and can be applied to existing injection molding machines. It can be implemented as a form with excellent properties.

In this case, the recirculation passage 11 is formed by a straight groove parallel to the axial direction Ds, and the size of the cross-sectional area of the recirculation passage 11 is determined by the amount of the recirculation resin Rm (recirculation amount) injected into the mold 2. It is desirable to select the amount in the range of 10 to 60 [%] with respect to the capacity of the resin R. If selected in this way, it is possible to achieve a good balance between production efficiency and yield rate in the production of molded products, so it is possible to optimize both from the viewpoint of securing production efficiency and securing yield rate. can.

In FIG. 2, 12 indicates a resin passage provided between the inner peripheral surface of the check valve portion 4sn and the outer peripheral surface of the mounting shaft portion 4sj, and 13 . shows the resin passage of Therefore, the resin passages 13 are notched at equal intervals in the circumferential direction. As a result, even when the check valve portion 4sn moves forward to the open position and abuts against the rear end surface of the conical tip portion 4sc, the resin passage 12 and the resin passage 13 are kept in communication, and the reverse state is maintained. When the stop valve portion 4sn moves rearward to the closed position and contacts the front end surface of the screw main body portion 4m, the resin passage 12 is blocked.

In addition, since the amount of recirculation resin Rm recirculated depends on the presence of the recirculation passages 11 and the magnitude of the injection pressure during molding, the partial recirculation injection function unit 5 in the first embodiment does not include the molding machine controller 42 is provided with an injection pressure additional setting function unit Fs capable of changing the molding injection pressure Pi (limiter pressure Ps), which will be described later. This injection pressure addition setting function section Fs has at least a function of setting the injection pressure Pis during molding higher than the molding injection pressure Pi when the resin R does not flow back by a predetermined amount.

By providing such an injection pressure additional setting function unit Fs, even in the case where the circulation passages 11 are provided, the recirculation amount of the recirculation resin Rm can be arbitrarily set by the injection pressure additional setting function unit Fs. Therefore, the recirculation amount can be easily set, and the influence on the original amount (filling amount) of the resin R to be injected and filled into the mold 2 can be avoided. Therefore, it is desirable to set the injection pressure Pis at the time of molding that is refluxed so as not to affect the original molding by the molding injection pressure Pi that is not refluxed.

FIG. 3 shows magnitudes of various physical quantities during molding when the resin R does not recirculate (no recirculation) and when a predetermined amount of recirculating resin Rm recirculates (with recirculation). In FIG. 3, the injection peak pressure Pp corresponds to a limiter pressure Ps, which will be described later. For this reason, as an example, the injection peak pressure Pp (limiter pressure Ps) without reflux is 50.5 MPa, whereas with reflux, that is, in the injection molding method according to the present embodiment, 52.5 [MPa], which is a slightly larger value than nothing, is shown. This injection peak pressure Pp (limiter pressure Ps) can be set by the injection pressure addition setting function section Fs.

As a result, the injection volume Qi with no reflux was 71.2 [cubic centimeters], whereas the injection volume Qi with reflux was increased to 98.0 [cubic centimeters]. Therefore, the reflux rate is {(98.0-71.2)/71.2}×100=37.6[%], which secures the range of 10-60[%]. Along with this, the injection stroke Xi of the screw at the time of injection is 44.8 [mm] when there is no reflux, whereas it is increased to 61.4 [mm] when there is reflux. The results are shown.

In this way, when configuring the partial circulation injection function unit 5, the injection pressure addition setting function of setting the injection pressure Pis at the time of molding higher than the injection pressure Pi when the resin R does not circulate by a predetermined amount. If the portion Fs is provided, even if the recirculation passages 11 are provided, the recirculation amount of the recirculation resin Rm can be arbitrarily set by the injection pressure addition setting function portion Fs, so that the recirculation amount can be easily set. In addition, it is possible to avoid affecting the original amount (filling amount) of the resin R to be injected and filled into the mold 2 .

Next, the molding procedure of the injection molding method using the injection molding machine M according to the first embodiment will be described with reference to FIGS. 1 to 8. FIG.

First, a specific molding mode to be used in the injection molding method according to this embodiment is preset. The basic molding procedure of this specific molding mode is the same as the procedure described in the aforementioned Patent Document 1 (International Publication No. WO2011/161899) already proposed by the present applicant.

The pre-setting procedure will be described below. First, the molding machine controller main body 42c initially sets the injection pressure, which is the injection condition of the injection device Mi. The injection pressure at this time can be set based on the capability (driving force) of the injection device Mi. In addition, the molding machine controller main body 42c initially sets the mold clamping force, which is the mold clamping condition of the mold clamping device Mc. The mold clamping force at this time can be set based on the capacity (driving force) of the mold clamping device Mc.

Next, the molding injection pressure Pi used in production is obtained by performing optimization processing for the initially set injection pressure, and the molding clamping force Pc used in production is obtained by performing optimization processing for the initially set mold clamping force. . Optimization of clamping force and injection pressure can be performed as follows. First, trial molding is performed using the initially set mold clamping force and injection pressure. When the mold clamping force is set to a large value, burrs do not occur, and sink marks, warpage, and degassing tend to be defective or slightly defective. Then, the size of the mold gap Lm between the fixed mold 2c and the movable mold 2m is determined by changing the magnitude of the mold clamping force and the magnitude of the injection pressure in stages and performing trial molding at each stage. This is acquired by a mold gap sensor (reflective optical sensor or the like), displayed on the waveform display section on the screen of the display 42d, and the quality of the molded product is observed.

FIG. 7 shows the changing state of the die gap Lm displayed on the waveform display section. In FIG. 7, after the start of injection, the mold 2 begins to open at time to, and the maximum mold gap Lmp occurs at time tp. After that, it is gradually displaced in the closing direction, and finally settles and stabilizes at the remaining die gap Lmr.

The optimization of the injection pressure is such that the above-mentioned predetermined mold gap Lm (approximately 0.03-0.30 [mm]) is generated between the moving mold 2m and the fixed mold 2c during injection filling, and good products can be molded. The molding injection pressure Pi can be set on the condition that Specifically, the injection pressure can be appropriately changed to select a size before the resin R does not normally fill the mold 2 . Further, the obtained molding injection pressure Pi is set as a limiter pressure Ps for the injection pressure during production.

In this case, as described above, the injection pressure additional setting function unit Fs is used to set the injection pressure Pis at the time of molding higher than the injection pressure Pi at the time of no reflux by a predetermined amount. In the case of the example, the injection pressure Pis at the time of molding was set to a slightly larger value (52.5 [MPa]) with respect to the injection pressure Pi of 50.5 [MPa], and this injection pressure Pis was set as the limiter pressure Ps. On the other hand, by repeating these trial moldings with different conditions, it is possible to select a mold clamping force that satisfies the conditions described above. The selected mold clamping force is set as the molding mold clamping force Pc when the mold 2 is clamped during production. In this case, the magnitudes of the mold clamping force and the injection pressure may be arbitrarily set by the operator, or may be obtained automatically or semi-automatically using an auto-tuning function provided in the injection molding machine M in combination.

Next, a specific processing procedure during production will be described with reference to the flowchart shown in FIG.

At the time of production, first, the resin R is plasticized based on the processing procedure of the specific molding mode, which is the basic molding method of the injection molding method according to this embodiment (step S1). In this case, since a predetermined amount of recirculated resin Rm, which will be described later, is also mixed, the plasticization process includes a plasticization acceleration process. During the plasticizing process, by controlling the hydraulic pump 36 and switching the valve circuit 37, the metering motor 25 of the injection device Mi is rotationally driven.

Note that the specific molding mode does not require a weighing process for accurately weighing the resin R, unlike the molding method in the general molding mode. That is, since the injection process in the specific molding mode only needs to perform the injection operation until the cavity is filled with the resin R, it is sufficient to plasticize a large amount of the resin R in the plasticizing process. In other words, weighing operation in a general weighing process is performed, but weighing control for obtaining an accurate weighing value is not required. In particular, the injection molding machine according to the present embodiment includes the recirculation operation by the partial recirculation injection function unit 5, and the part of the remaining plasticized accumulated resin R (recycled resin Rm), that is, the injection resin amount Ri, is , 10 to 60 [%], it is desirable to secure a plasticizing treatment amount that is at least twice the volume of the molded product (one shot amount).

FIG. 5 shows the behavior of the resin R during the plasticizing process. In this case, the screw 4 rotates over a set rotation speed and period. Since the resin R is transferred forward by the rotation of the screw 4, as indicated by arrows D1 in FIG. That is, as the resin R moves forward from the screw main body 4m side, the check valve portion 4sn moves to the front open position shown in FIG. It reaches the front of the conical tip portion 4sc through the resin passage 12 inside the portion 4sn and the resin passages 13 of the conical tip portion 4sc. As a result, the plasticized resin R gradually accumulates in the heating cylinder 3 in front of the conical tip portion 4sc, and the screw 4 moves backward along with the accumulation.

Further, by controlling the hydraulic pump 36 and switching the valve circuit 37, the mold clamping cylinder 27 of the mold clamping device Mc is driven, and the mold for the mold 2 is adjusted so that the mold clamping force becomes the set molding mold clamping force Pc. Tightening is performed (step S2). After that, by switching the valve circuit 37 and controlling the hydraulic pump 36, the injection cylinder 24 of the injection device Mi is driven to start injection processing of the resin R into the mold 2 (step S3). In this case, the screw 4 should be advanced by rated operation, and speed control for the screw 4 is unnecessary. When injection is started, the plasticized and melted resin R in the heating cylinder 3 is filled into the cavity of the mold 2 through the injection nozzle 3n as indicated by the arrow D2 in FIG. 6 (step S4). Then, as the resin R is filled, the injection pressure rises (step S5). After that, when the injection pressure reaches the limiter pressure Ps, control to maintain the limiter pressure Ps (injection pressure Pis), that is, control to prevent overshoot, is performed, and the injection pressure is maintained (restricted) at the limiter pressure Ps. ) (step S6). Therefore, substantial one-pressure control is performed in the injection operation.

On the other hand, as the injection of the resin R is started in step S3, as shown in FIG. Due to the function, a predetermined amount of recirculated resin Rm, which becomes part of the resin R, is gradually recirculated toward the screw main body 4m behind the screw head 4s (step SN). That is, since the screw 4 moves forward during injection, the check valve portion 4sn moves backward to the closed position due to the forward resin pressure. As a result, the resin passage 12 inside the check valve portion 4sn is blocked, but the circulating resin Rm, which is a part of the resin R accumulated in front of the screw head portion 4s, is released as shown in FIG. 6 by the injection pressure Pis. As indicated by arrows D3 . . . , the screw passes through the gap between the outer peripheral surface of the conical tip portion 4sc of the screw head portion 4s and the inner peripheral surface of the heating cylinder 3, and further through the circulation passage 11 on the outer peripheral surface of the check valve portion 4sn. It is returned to the main body 4m side.

On the other hand, when the cavity of the mold 2 is filled with the resin R, the mold 2 is pressurized by the resin R, and a mold gap Lm (FIG. 7) is generated between the fixed mold 2c and the movable mold 2m (step S7 ). This mold gap Lm is generated based on the preset mold clamping force Pc and molding injection pressure Pi (injection pressure Pis). In this case, when a preset injection time elapses from the start of injection, the injection filling of the resin R into the mold 2 is completed, so the application of the molding injection pressure Pi (injection pressure Pis) is stopped or reduced. As a result, the injection process is substantially completed, and accordingly, the reflux action is also completed (step S8).

Upon completion of the injection process (refluxing action), the resin R is plasticized (step S9). In this case, a predetermined amount of recirculated resin Rm is mixed in the front side of the screw main body 4m, that is, a part of the recirculated resin Rm of the primary plasticized resin R accumulated in front of the screw 4 is mixed. Since the resin R is returned to the screw main body 4m and mixed, the resin R in which the recirculated resin Rm is mixed is subjected to a plasticizing treatment. Therefore, even if insufficiently plasticized resin R accumulates in front of the screw 4, re-plasticization treatment is performed, and plasticization is further promoted.

Further, when the injection process ends, the solidification of the resin R progresses with the lapse of time, and the resin R is naturally compressed along with the solidification (step S10). That is, since the volume decreases due to solidification of the resin R, the mold 2 (particularly, the movable mold 2m) is naturally compressed by the pressurizing action due to the elastic return so as to follow this decrease in volume. When the set cooling time has passed, the mold clamping cylinder 27 is driven by switching the valve circuit 37 and controlling the hydraulic pump 36 to move the movable mold 2m backward to open the mold, and the ejector cylinder 31 is moved. Then, the molded product adhering to the movable mold 2m is ejected (steps S11 and S12). This removes the molded product and completes one molding cycle. After that, when the next molding is continued, mold clamping, injection, cooling, etc. are similarly performed (steps S13, S2, . . . ).

FIG. 8 shows the standard deviation values of the variation in the mold displacement amount when reflux occurs (with reflux) and the variation in the mold displacement amount when there is no reflux (without reflux) by the injection molding method according to the present embodiment (first example). shows a comparison diagram of That is, FIG. 8 shows variations in the maximum value Lmp of the mold gap Lm in FIG. 7 when 30 molded products were molded. According to this, the standard deviation value without reflux is 4.2 [μm], while the standard deviation value with reflux is 3.8 [μm], which is about 11 [%]. Improvement was seen. This means that the homogenization of the plasticized resin R was further enhanced, and the yield rate of the molded product was also obtained corresponding to the rate of this improvement.

Therefore, according to the injection molding machine M (injection molding method) according to the first embodiment, the basic configuration (function) is to advance the screw 4 accommodated in the heating cylinder 3 of the injection device Mi. at the front end of the screw 4, the mold 2 is filled with the resin R in front of the screw head portion 4s. . . , to the side of the screw main body 4m behind the screw head 4s, the yield rate of the final molded product can be greatly increased. It can be provided as a new injection molding method (injection molding machine) that can be enhanced. As a result, it becomes possible to improve production efficiency and reduce production costs in the production of large-sized molded products and special resin molded products, effectively contributing to avoidance of resource loss and wasteful energy consumption.

In particular, in the injection molding machine M (injection molding method) according to the first embodiment, at least the mold clamping device Mc, which enables natural compression of the resin R in the mold 2 as the resin R solidifies, is used as the mold clamping device. A molding injection pressure Pi and a mold clamping force Pc capable of forming a non-defective product are obtained and set in advance so that a predetermined mold gap Lm is generated between the movable mold 2m and the fixed mold 2c during injection filling. At the time of molding, the mold clamping device Mc is clamped by the molding clamping force Pc, the molding injection pressure Pi is set as the limiter pressure Ps, and the injection device Mi is driven to inject and fill the mold 2 with resin. Since it is applied to the method, the injection molding method according to the present invention can be applied to a specific molding mode that does not have a weighing process, that is, a specific molding mode that is hardly affected by the state of the injection device Mi side. It can be implemented as an optimal form from the viewpoint of improving efficiency, reducing production costs, and contributing to avoidance of resource loss and avoidance of wasteful energy consumption.

Second embodiment

Next, the configuration of the partial recirculation injection function unit 5 provided in the injection molding machine M according to the second embodiment will be described with reference to FIGS. 9 to 10. FIG.

FIG. 9 is a part of the injection device Mi in the injection molding machine M shown in FIG. 1 shows part of an injection device Mi.

As shown in FIG. 9, the injection device Mi of the second embodiment has the same basic configuration as the injection device Mi provided in the injection molding machine M shown in FIG. 2 of the first embodiment. In the second embodiment, when configuring the partial recirculation injection function unit 5, a reverse rotation control function unit Fc for reversely rotating the screw 4 is additionally provided in the molding machine controller 42 shown in FIG. This makes it possible to promote reflux of Rm and control its quantity. Therefore, the program area 42mp of the internal memory 42m stores software for implementing the reverse rotation control function unit Fc. If such a reverse rotation control function part Fc is provided when configuring the partial recirculation injection function part 5, the screw 4 itself does not need to be modified in terms of form. This makes it possible to achieve further ease of implementation, and further increases versatility.

Further, the reverse rotation control function unit Fc is provided with a reverse rotation setting function unit Fcs for setting the period and rotation speed for reverse rotation of the screw 4 . If such a reverse rotation setting function unit Fcs is provided, the amount of recirculation of the recirculation resin Rm can be set by the reverse rotation setting function unit Fcs. On the other hand, it is possible to avoid affecting the original filling amount of injection filling.

In this case, when setting the reverse rotation period and rotation speed of the screw 4, the screw 4 is moved forward by the molding injection pressure Pi, and the resin R in front of the screw head portion 4s is injected into the mold 2. A predetermined amount of circulating resin Rm to be part of the resin R, that is, the amount of circulating resin Rm selected in the range of 10 to 60 [%] with respect to the capacity of the resin R to be injected and filled in the mold 2 is injected into the screw. It is desirable to set a period and a rotational speed in which the resin can flow back to the screw main body 4m behind the screw head 4s through the resin passage 12 inside the head 4s.

In addition, in FIG. 9, the same parts as those in FIGS. 1 and 2 are denoted by the same reference numerals to clarify the configuration thereof, and detailed description thereof will be omitted.

Next, the molding procedure of the injection molding method using the injection molding machine M according to the second embodiment will be described with reference to the flow charts shown in FIGS. 1 and 10 (FIG. 4).

The flowchart shown in FIG. 10 shows specific processing in step SN in the flowchart shown in FIG. 4, and the overall molding procedure of the injection molding method is performed according to the flowchart shown in FIG. That is, in the injection molding method using the injection molding machine M according to the second embodiment, the same presetting as the specific molding mode in the first embodiment is performed, and the specific processing procedure during production is shown in FIG. Steps S1 to S11 are basically the same except for the processing contents of step SN. Therefore, in the following, only the processing portion according to the second embodiment in step SN will be described in detail with reference to FIG.

Assume that step S3 in the flowchart shown in FIG. 4 is being performed. In step S3, the injection cylinder 24 of the injection device Mi is driven to start the process of injecting the resin R into the mold 2, and the mold 2 is filled with the resin R accumulated in front of the screw 4 (step S4).

On the other hand, reverse rotation control of the screw 4 is performed by the reverse rotation control function unit Fc at a predetermined timing, for example, the timing at which the injection process is started or the timing at which a predetermined set time has elapsed (step SN1). As a result, the screw 4 rotates backward in the direction of the arrow Drn at the rotational speed set by the reverse rotation setting function section Fcs. As a result, part of the resin R accumulated in front of the screw head portion 4s and existing on the side of the screw head portion 4s is promoted to flow back to the side of the screw main body portion 4m (step SN2). That is, since the backward rotation of the screw main body 4m acts to move the resin R backward, a predetermined amount of the recirculated resin Rm, which is part of the resin R accumulated in front of the screw head 4s, is removed from the screw head 4s. At 4s, the fluid flows back to the screw main body 4m side through the circulation passages 11, and the circulation is promoted.

Then, when the period (recirculation time) set by the reverse rotation setting function unit Fcs has elapsed, the reverse rotation control is stopped (steps SN3 and SN4). On the other hand, on the side of the mold 2, the mold gap Lm is generated by the injection filling, and when the injection process is completed, the solidification of the resin R progresses with the lapse of time, and the resin R naturally recovers as the solidification progresses. The same processing (behavior) as in the first embodiment, such as compression, is performed (steps S5, S6, S7, . . . ).

Therefore, according to the injection molding method using the injection molding machine M according to the second embodiment, the partial recirculation injection function unit 5 can perform the same action (function) as in the first embodiment. In addition to being able to enjoy the same basic effect as the first embodiment, it is possible to enjoy an effect greater than that of the first embodiment, that is, acceleration of the reflux action.

FIG. 11 shows the relationship between the screw rotation and the amount of reflux when using the injection molding method according to the second embodiment. As described above, if the injection molding method according to the second embodiment is used, it is possible to promote the circulation of the circulation resin Rm and to control the amount of the circulation resin. can be controlled.

Although the preferred embodiments (first and second embodiments) have been described in detail above, the present invention is not limited to such embodiments, and detailed configurations, shapes, quantities, numerical values, Methods and the like can be arbitrarily changed, added, or deleted without departing from the gist of the present invention.

For example, the first embodiment shown in FIG. 2 illustrates the screw head portion 4s using the cylindrical check valve portion 4sn, but the ball-shaped check valve portion 4sn as shown in FIG. The check valve portion 4sn and the screw head portion 4s of various forms can be applied, and their configurations and types are not limited. In addition, in FIG. 12(a), 51 indicates a resin passage. In addition, in FIG. 12(a), the same constituent parts and the same functional parts as those in FIG. 2 are denoted by the same reference numerals to clarify the structure and to omit detailed description thereof. Therefore, FIG. 12(a) is a modified example of the first embodiment, and the basic configuration of the injection molding machine M and the basic processing procedure of the injection molding method are the same as those of the first embodiment.

Further, the injection molding machine M and the injection molding method according to the present invention can be applied even to a screw head portion 4s having no check valve portion 4sn as shown in FIG. The presence or absence of the stop valve portion 4sn does not matter. In addition, 52 shows a flight part in FIG.12(b). In addition, in FIG. 12(b), the same components and functional parts as those in FIG. 9 are denoted by the same reference numerals to clarify the configuration and to omit detailed description thereof. Therefore, FIG. 12(b) is a modified example of the first embodiment or the second embodiment, and the basic configuration of the injection molding machine M and the basic processing procedure of the injection molding method are the same as those of the first embodiment described above. Or it will be the same as the second embodiment.

In the construction of the partial recirculation injection function unit 5, the configuration in which at least one recirculation passage 11 for recirculating the recirculation resin Rm is provided in the screw head portion 4s was exemplified. The recycling passage 11 also includes the case of selecting a small size, increasing the inner diameter of the heating cylinder 3 , or grooving a part of the inner wall of the heating cylinder 3 . Further, the additional injection pressure setting function section Fs is not an essential element, and depending on the form of the circulation passages 11, for example, the additional injection pressure setting function section Fs may not necessarily be provided. When a predetermined amount of recirculating resin Rm is circulated to the screw main body 4m side, there is a method of passing it through the inside of the screw head portion 4s, a method of passing it through the outer peripheral side of the screw head portion 4s, and a method of passing it through the inside of the screw head portion 4s. and the outer peripheral side of the screw head portion 4s. On the other hand, although it is most suitable for using a specific molding mode, it is equally applicable to injection molding machines M and injection molding methods that use general molding modes. Further, the injection molding machine M may be a hydraulic injection molding machine or an electric injection molding machine, and the driving system thereof is not limited.

INDUSTRIAL APPLICABILITY The present invention can be used for various injection molding machines and injection molding methods that carry out molding by injecting and filling a mold clamped with a predetermined mold clamping force with a resin under a predetermined injection pressure.

2: Mold, 2c: Fixed type, 2m: Movable type, 3: Heating cylinder, 4: Screw, 4s: Screw head portion, 4m: Screw body portion, 5: Partial reflux injection function portion, 11: Reflux passage , M: injection molding machine, Mc: mold clamping device, Mi: injection device, R: resin, Rm: circulating resin, Pi: injection pressure, Pis: injection pressure, Fs: injection pressure additional setting function unit, Fc: reverse rotation Control function part, Fcs: reverse rotation setting function part, Lm: mold gap, Pc: mold clamping force, Ps: limiter pressure

Claims (7)

Injection molding equipped with a mold clamping device that clamps a mold consisting of a fixed mold and a movable mold with a predetermined mold clamping force, and an injection device that injects and fills the clamped mold with resin at a predetermined injection pressure. In the machine, by moving forward the screw housed in the heating cylinder of the injection device, the resin in front of the screw head at the front end of the screw is injected and filled into the mold, and at the same time, the capacity of the resin is 10-60. A partial reflux injection function in which the resin selected in the range of [%] is returned to the screw main body side behind the screw head through the inner side of the screw head and/or the outer peripheral side of the screw head as a reflux resin. An injection molding machine characterized by providing a part. 2. The injection molding machine according to claim 1, wherein the partial reflux injection function section is configured by providing at least one circulation passage for resin circulation in the screw head section. In the partial reflux injection function part, the injection pressure during molding is set higher by a predetermined amount than the injection pressure when the resin does not reflux, which is set when the partial reflux injection function part is not provided. 3. The injection molding machine according to claim 2, further comprising an injection pressure additional setting function unit for adjusting the injection pressure. 2. The injection molding machine according to claim 1, wherein said partial recirculation injection function section is provided with a reverse rotation control function section for rotating said screw in reverse. 5. The injection molding machine according to claim 4, wherein the reverse rotation control function section is provided with a reverse rotation setting function section for a period and a rotation speed for reverse rotation of the screw. In the injection molding method, a mold consisting of a fixed mold and a movable mold clamped with a predetermined mold clamping force by a mold clamping device is injected with resin at a predetermined injection pressure by an injection device. By moving forward the screw accommodated in the heating cylinder of the device, the resin in front of the screw head portion at the front end of the screw is injected and filled into the mold, and at the same time, 10 to 60 [%] of the volume of the resin. An injection molding method characterized in that the resin selected in the range is circulated as a circulating resin to the screw main body side behind the screw head portion through the inner side of the screw head portion and/or the outer peripheral portion side of the screw head portion. As the mold clamping device, a mold clamping device that enables natural compression of the resin at least as the resin in the mold solidifies is used. In addition, the injection pressure (hereinafter referred to as molding injection pressure) capable of molding a good product and the mold clamping force (hereinafter referred to as mold clamping force) capable of molding a good product are obtained and set, and during molding, the mold clamping device is operated by the mold clamping force. 7. The injection molding method according to claim 6, wherein the mold is clamped, the molding injection pressure is set as a limiter pressure, and the injection device is driven to inject and fill the mold with the resin.

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