JP2004001563A - Injection molding method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an injection molding method which can improve the quality of a molding by removing harmful substances produced during melting of resin pellets in an injection molding machine. <P>SOLUTION: The resin pellets before being dried are supplied into the cylinder of the injection molding machine for the first injection. The quality of the purge of a resin injected in a prescribed period of time from the first injection is examined, and injection molding is done by injecting an optimum pile volume per obtained unit shot. <P>COPYRIGHT: (C)2004,JPO

Description

The present invention relates to an injection molding machine, an injection molding method, and an injection molded product for performing injection molding using resin pellets, particularly, undried resin pellets.

(4) In a conventionally used injection molding machine, resin pellets are dried for several days by a dryer set at a predetermined temperature in advance. Then, the resin pellets obtain a predetermined dry state. During this drying, moisture in the resin pellets is removed to a predetermined value. Then, the dried pellets having a predetermined moisture value are put into an injection molding machine. That is, before the resin pellets are put into the injection molding machine, sufficient attention is paid to quality control of the water content of the resin pellets.

However, the injection molded product has bubbles. This means that conventional drying methods are inadequate. It is considered that the cause is that the chemical bond of the resin component of the pellet generates moisture by heating. That is, the chemicals used for the resin raw material and the plasticizer forming the pellets generate steam and gas by heating. Further, the chemical substances in the pellets are generated as harmful gases in the melting process in the injection molding machine. Then, the generated harmful gas is discharged into the atmosphere.

Today, there is a problem of harmful substances contained in plastics, in particular, endocrine disrupting substances (environmental hormones), which affect the human body. Therefore, prevention of the release of such harmful substances into the atmosphere is a major social issue.
The present invention has been made to solve the above problems, an object of the present invention is to remove harmful substances generated during the melting of resin pellets in an injection molding machine, can improve the quality of molded products, In addition, the number of defective products can be reduced by 20% or more as compared with the conventional case, and the number of cleaning maintenances on the inner surface of the mold can be reduced. Therefore, productivity can be improved and electric energy required for injection molding can be significantly reduced.

The present invention provides a unit shot obtained by supplying undried resin pellets into a cylinder of an injection molding machine, performing a first injection, and inspecting a quality of a resin purge injected after a lapse of a predetermined time from the first injection. This is an injection molding method for performing injection molding by performing injection with an optimum amount of deposition per unit.

The present invention provides: (a) a step of depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine; ;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) performing injection molding with the optimal deposition amount;
An injection molding method comprising:

The present invention provides: (a) a step of depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine; ;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) detecting the amount of pellets supplied during injection molding;
(F) controlling the amount of pellets deposited based on the detection information;
(G) performing injection molding with the optimal deposition amount;
An injection molding method comprising:

The present invention provides: (a) a step of depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine; ;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) identifying optimum operating conditions for operating conditions such as the amount of pellet supply per unit shot, the degree of decompression, and the pellet temperature as a result of the inspection;
(E) injection molding under said optimal operating conditions;
An injection molding method comprising:

The present invention provides: (a) a step of depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine; ;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) controlling operating conditions such as the amount of pellet supply, the degree of pressure reduction, and the temperature of the pellet so that the optimal amount of deposition is present in the pellet supply;
(F) injection molding under said optimal operating conditions;
An injection molding method comprising:

The present invention provides: (a) a step of depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine; ;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) a step of supplying the pellets supplied to the injection molding machine separately from moisture and gas discharged from the molten pellets;
(F) performing injection molding with the optimum deposition amount;
An injection molding method comprising:

In the above-described injection molding method, the pellets in the inspection step are supplied as one shot of a deposition amount in which the pellets do not overflow from the cylinder of the injection molding machine even if the pellets are continuously supplied into the cylinder of the injection molding machine. Is done.
In the injection molding method, in place of the step of specifying the optimum operating conditions of the pellet supply amount, the degree of decompression, and the temperature of the pellet, those recommended in specifications or catalogs or those already obtained by inspection. Use the value of

In the injection molding method, the step of specifying the optimum deposition amount is performed by changing operating conditions such as a pellet supply amount, a pellet temperature, and a degree of pressure reduction.
In the injection molding method, the deposition amount control step is controlled by changing a supply amount.
In the injection molding method, the deposition amount control step is controlled by changing a supply time while keeping a supply amount constant.

In the above-mentioned injection molding method, the deposition amount control step turns off and on the supply.
The injection molding method may further include a step of changing the position to be detected.
The injection molding method further includes a gas supply step for supplying a gas such as air or an inert gas into the injection molding machine.
In the injection molding method, a dry pellet or a recycled resin is used instead of the undried pellet.

The present invention provides a unit shot obtained by supplying undried resin pellets into a cylinder of an injection molding machine, performing a first injection, and inspecting a quality of a resin purge injected after a lapse of a predetermined time from the first injection. This is an injection molding machine for performing injection with an optimal amount of deposit per unit.
The injection molding machine further includes a pellet accumulation amount control unit that controls at least one of operation conditions such as a pellet supply amount, a degree of pressure reduction, and a pellet temperature.
In the injection molding machine, the pellet deposition amount control means includes a pellet supply adjusting device.

In the injection molding machine, the pellet supply adjusting device varies a supply amount.
In the injection molding machine, the pellet supply adjusting device varies a supply time while keeping a supply amount constant.
In the injection molding machine, the pellet supply adjusting device turns off and on the supply.
In the injection molding machine, at least one detection device is provided at a position of an optimum deposition amount.
The present invention is an injection molded product manufactured by the injection molding machine or the injection molding method.

According to the present invention, water and gas generated during melting of resin pellets in an injection molding machine can be sufficiently removed. Further, moisture and gas on the inner surface of the mold can be sufficiently removed. Thus, a molded article having excellent quality can be obtained. Therefore, maintenance in the mold is facilitated and productivity is improved. Furthermore, unmanned and automated injection molding is achieved.

As described above, the substantial configuration of the present invention is as follows: After the virgin resin pellets are supplied through the pellet supply path into the cylinder of the injection molding machine to perform the first injection, The quality of the resin purge injected after a lapse of a predetermined time from the first injection is inspected, and as a result of the inspection, an optimum deposition amount per unit shot is specified. Injection molding is performed with this optimum deposition amount. Further, the amount of the pellets supplied during the injection molding is detected, and the amount of the pellets is controlled based on the detection information so that the amount of the pellets always keeps an optimum value. Thus, the cylinder of the injection molding machine always obtains the optimum deposition amount per unit shot. Further, the water and gas discharged from the mold and / or the water and gas discharged from the pellets melted in the cylinder of the injection molding machine are exhausted to the atmosphere under reduced pressure. The configuration of the invention is applied to an injection molding machine, an injection molding system, a pellet supply unit, and an injection molding method.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings to explain the present invention in detail.
Conventionally, resin pellets are dried for several days in a drying oven until a certain amount of water is obtained. However, in the present embodiment, instead of using dried resin pellets, undried resin pellets whose water content is not adjusted are used.

FIG. 1 shows a schematic diagram of an injection molding system. In the figure, reference numeral 10 denotes an injection molding system. A storage tank 12 stores resin pellets such as nylon. The pellets are conveyed to a pellet storage 22 via an air blower 14, an autoloader 16, and a vacuum shutoff valve 20 which constitute a pellet automatic supply device. Vacuum shut-off valves 18 are provided on the transport paths connecting the storage tank 12 and the autoloader 16 and between the exhaust fan 14 and the autoloader 16, respectively. When the pellets move to the autoloader 16, the vacuum shutoff valve 18 closes.

The pellets are transferred from the autoloader 16 to the pellet storage 22 via the vacuum shutoff valve 20. The autoloader 16 includes a level sensor 21 that detects a position where the pellet is deposited. When the pellets are transferred from the autoloader 16 to the pellet storage 22, the vacuum shutoff valve 20 closes. Next, the resin pellets are conveyed from the pellet storage 22 to the injection molding machine 26 through the pellet supply 24.

The injection molding machine 26 melts the pellets supplied into the cylinder, and injects the molten resin from an injection hole provided at one end thereof. The injection molding machine 26 feeds the pellets into the cylinder to perform the first injection, and inspects the quality of the injected resin purge after a lapse of a predetermined time from the first injection to obtain the optimum deposition per unit shot. Inject by volume.

ペ レ ッ ト As shown in FIG. 2, the pellet feeder 24 includes a pellet feed adjusting device 28. The pellet feeder 24 includes first and second pellet feeders 30 and 32. The amount of pellets controlled by the pellet supply adjusting device 28 is supplied from the pellet storage 22 to the pellet supply 24.

Here, the pellet supplier 24 has a double structure. That is, the pellet feeder 24 includes a transparent acrylic first pellet feeder 30 and a copper second pellet feeder 32 housed in the first pellet feeder 30. The tip of the second pellet supply 32 protrudes toward the injection molding machine from the tip of the first pellet supply. Thus, the pellets pass through the second pellet feed 32 and moisture, gas, etc. pass through the space between the first pellet feed 30 and the second pellet feed 32. Reference numeral 31 denotes a net for removing moisture exhausted from the pellets melted in the cylinder, dust in the gas, and the like.

Thus, the first pellet feeder 30 and the second pellet feeder 32 accommodated in the first pellet feeder 30 constitute the contact prevention device 34. And the 1st pellet supply body 30 is provided with exhaust port 36. The exhaust port 36 is connected to a pressure reducing device 38 described later. With the above configuration, the pellet supply path body 40 is configured.

Detection devices 50 and 52 described below are attached to the second pellet supply body 32. Preferably, the detection device is provided below the second pellet supply 32.
The above-described pellet supply path body 40 is integrally formed, but may be configured so that each component can be removed in consideration of maintenance and cleaning. The autoloader and the inside of the pellet storage are cleaned by flowing gas from above. The pellets rub against each other when transported or dropped. As a result, the pellet is charged with static electricity. When static electricity is generated on the pellet, smooth supply of the pellet is prevented. Therefore, preferably, a static electricity preventing means (not shown) is provided in the supply path from the storage tank to the pellet supply. For example, the antistatic means is ground.

The supply of the pellets by the pellet supply controller 28 is controlled by varying the amount of pellets supplied to the injection molding machine, by varying the supply time while keeping the supply amount constant, or by turning the supply OFF-ON. The pellet supply adjusting device 28 includes a motor 42. Then, the number of revolutions of the motor is varied by adjusting the supply amount of the pellets. Alternatively, the rotation speed of the motor is varied (including the stop) while the rotation speed of the motor is kept constant. Or, the rotation of the motor is turned off and on. In addition, the supply amount of pellets can be varied also by the degree of pressure reduction and the pellet temperature. Therefore, the supply amount of the pellets, that is, the pellet deposition amount, increases as the degree of pressure reduction increases and the pellet temperature increases.

ペ レ ッ ト Although the pellet supply adjusting device 28 in FIG. 2 is mounted in the horizontal direction, it can be mounted in the vertical direction. The pellet supply adjusting device 28 includes a rotary shaft bar 44, a spiral supply unit 46 having a predetermined pitch, and a drive motor 42 at the other end. The rotating shaft bar 26 and the spiral supply unit 28 of the pellet supply adjusting device 28 are housed in a housing 48. The drive motor is controlled based on information from a detection device described later. Here, by controlling the number of rotations of the rotating shaft connected to the motor, the supply amount of the pellets conveyed through the spiral portion supply unit is adjusted. In addition, the pellet supply amount adjusting device 28 is not limited to the above-described configuration, and may include various adjusting mechanisms, for example, an adjusting blade for adjusting the diameter of the pellet supply path.

Reference numerals 50 and 52 are detection devices, for example, position sensors. The detection devices 50 and 52 are attached to the second supply body 32. The detecting device 50 detects a state in which the pellet overflows from the cylinder and comes out into the second pellet supply body. In addition, the detecting device 50 detects a state in which the pellets have begun to deposit beyond the specified depositing position in the second pellet supply. Then, when the detection device operates, information is sent to the system control device 54. The system controller 54 sends a signal for controlling the amount of the deposited pellets to the pellet supply controller based on this information. Thus, the pellet feed rate adjusting device 28 adjusts the feed rate of the pellets by adjusting the number of revolutions of the motor 30, or adjusts the drive time while keeping the number of revolutions of the motor 30 constant, or turns off the drive of the motor 30. Turn ON. Further, a signal from the pressure control device 56 in the system control device 54 is sent to the exhaust fan 14, and the supply amount of the pellets from the storage tank 12 is changed.

駆 動 Furthermore, a drive detecting device 58 for detecting variation in driving of the screw is provided at one end of the screw. Reference numeral 60 denotes an injection molding machine control device for controlling the operation of the injection molding machine such as the movement of a screw provided in the injection molding chamber 62 of the injection molding machine. The information of the injection molding machine controller 60 is sent to the system controller 54, and the entire injection molding system is controlled.

射出 The injection molding machine has a heater around the periphery, an injection hole at one end, and a screw. The screw has a metering zone, a compression zone and a feed zone. Thus, the pellets rise to a homogeneous temperature with self-heating. In the compression zone, the pellets are melted and kneaded. By this action, a certain amount of molten resin is sent out to the nozzle side. The pellets supplied into the injection molding machine have a cushion pressure when compressed by a screw. The range of variation in cushion pressure is set to 5 mm ± 0.5 mm or less.

内部 The inside of the injection molding machine may be kept in a sealed state, but atmospheric air or an inert gas may be introduced from the other end of the injection molding machine. The gas supply means is an opening 64 provided at the other end facing the injection hole of the cylinder of the injection molding machine. The gas introduced into the cylinder may be an inert gas in addition to air. Further, preferably, the gas is heated. The air supply rate in a 50 ton injection molding machine manufactured by FANUC, which is usually used, is about 200 Nl / min to about 300 Nl / min.

(4) The pellets supplied from the pellet supply into the injection molding chamber of the injection molding machine are moved in the chamber by a screw, and moisture and gas in the pellets are discharged during melting. The gas containing water and gas discharged from the pellets is taken out of the injection molding machine by a vacuum pump constituting the pressure reducing device 38. The pressure reducing device 38 is attached near the lower end of the second supply body 32. Thus, the pressure reducing device 38 sucks in moisture and gas generated from the molten pellets and exhausts the moisture and gas to the atmosphere. At this time, the inside of the injection molding chamber or the supply body is set to a reduced pressure state, preferably about 300 Torr or more.

The gas containing the extracted moisture and gas is transferred to the pellet heating device 68 through the exhaust gas treatment unit 66 and the vacuum pump 38. The pellet heating device 68 is a heat exchanger. Hot gas from the injection molding machine is carried to the heat exchanger. On the other hand, air in the atmosphere is conveyed to a heat exchanger via a compressor (not shown). Thus, atmospheric air is warmed to about 80 ° C. as it passes through the heat exchanger. Then, the hot air is supplied to the pellet storage tank 12. Here, by disposing the heat exchanger 68 in the housing, the housing is heated to about 40 ° C. The air is warmed and transported to the heat exchanger 68 while the external air passes through the housing. Further, it is preferable that the housing houses a vacuum pump, an exhaust gas treatment device, and a compressor.

Preferably, harmful substances contained in the moisture and gas in the hot exhaust gas are treated by an exhaust gas treatment device 66 such as a filter before entering the heat exchanger. Then, the purified hot gas is deprived of heat by the heat exchanger and discharged to the atmosphere. Thus, the undried resin pellets are heated in the pellet storage tank. Then, the heated pellets are supplied into the injection molding machine through the pellet supply path body. Heating the pellets is particularly effective when using undried resin pellets.

Note that the pellet heating device may have a configuration other than the configuration described above. For example, purified hot gas is introduced directly into the pellet supply path. Further, a heating device such as a band heater may be attached to the pellet supply path body. The amount of water discharged by heating the pellets by the heating device 75 such as a band heater is smaller than the amount of water discharged by melting in the injection molding machine. The amount of the impurity gas discharged by the former is smaller than the amount of the gas discharged by the latter.

Furthermore, the second pellet feeder 32 made of copper in FIG. 2 constitutes a second pellet heating device. That is, the hot gas generated in the injection molding machine is released to the atmosphere by the decompression device. When the hot gas passes through the space between the first pellet feeder 30 and the second pellet feeder 32, the second pellet feeder 32 is heated by the hot gas. Thus, the pellets are heated while they pass through the heated copper feed.

Next, the molten resin injected from the injection port of the injection molding machine is injected into a mold 70 placed forward. The molten resin solidifies in the mold 70, and an injection molded product is produced. Here, most of the gas and moisture in the injected resin are already removed in the melting step in the injection molding machine, but gas and moisture partially remaining in the resin enter the mold. The mold is connected to a pressure reducing device 38 to prevent moisture and gas from adhering to the inner surface of the mold. Further, the harmful substances in the gas discharged from the mold are taken into the filter 66, and the harmful substances are removed. The decompression device forcibly exhausts the water and gas discharged from the injection molding machine and / or the water and gas discharged from the mold.

Here, the same vacuum pump as the vacuum pump for discharging gas and moisture in the injection molding machine may be used, or a separate vacuum pump may be used. Further, the vacuum pump extracts water and gas discharged from the injection molding machine and / or the mold under reduced pressure. Thus, a pellet exhaust path body 71 is constituted by a path from the injection molding machine and / or the mold to take out moisture and gas from the mold under reduced pressure and discharge the gas and air to the atmosphere.

FIG. 3 shows a schematic view of the injection molding system 72. In the figure, a plurality of injection molding machines 26 are arranged. The supply of the pellets to each of the injection molding machines 26 is performed by a single central controller 74 that controls the supply amount, the operation parameters of the injection molding machine, the pressure for supply, the heating control, and the like. Thus, an unmanned and automated injection molding system can be achieved by one central control device.

Hereinafter, the operation according to the present invention will be described in detail.
The resin pellets supplied to the injection molding machine according to the present invention are undried pellets that have not been dried before being supplied to the injection molding machine. Further, as the resin pellets, generally used dry resin pellets and recycled resin can be used in place of the undried resin pellets.

に お い て In the present invention, the undried resin pellets are supplied into the injection molding machine. At this time, a unit for obtaining a non-defective product is obtained by operating conditions such as a kind of a resin material as a raw material of the pellet, a supply amount of the pellet, a pellet temperature, and a degree of decompression when discharging moisture or gas in the injection molding machine to the outside. The shot, for example, the injection amount per shot is different. That is, the amount of the pellets supplied into the cylinder of the injection molding machine per unit shot is different.

Therefore, undried resin pellets made of a certain type of resin material are supplied into a cylinder of an injection molding machine, and operating conditions such as a supply amount of the pellets, a temperature of the pellets, and a degree of pressure reduction are specified. At this time, first, even if the pellets are continuously supplied into the injection molding machine, the amount of deposition that does not cause the pellets to overflow from the cylinder of the injection molding machine is supplied as one shot.

Next, injection is performed using the pellets deposited for one shot. Then, inspection or evaluation of the quality of the injected resin purge is performed. The inspection is performed by a resin purge injected after a predetermined time, for example, two to three minutes after the resin purge first injected. If a good product is obtained by this inspection, the operating conditions such as the supply amount of the pellet are specified. Further, it is preferable to increase the specified accumulation amount and obtain a threshold value of the accumulation amount from a good product to a defective product. In addition, it is preferable to reduce the specified accumulation amount and obtain a threshold value of the accumulation amount from a good product to a defective product.

Here, a deposition amount between the specified deposition amount and the threshold value of the deposition amount is referred to as an optimum deposition amount. In addition, between the operating conditions such as the pellet supply amount at which the specified deposition amount is obtained, the pellet temperature, the degree of decompression, and the operating conditions such as the pellet supply amount, the pellet temperature, and the degree of decompression at which the threshold value of the deposition amount is obtained. The operating conditions are called optimal operating conditions. That is, in order to obtain a good injection molding, the injection molding should be performed with the accumulation amount between the specified accumulation amount and the threshold value of the accumulation amount. Here, the optimum deposition amount includes the specified deposition amount and a threshold value of the deposition amount. Therefore, the injection molding may be performed using the specified accumulation amount obtained by the above-described evaluation without obtaining the accumulation amount threshold value.

Therefore, as a result of the inspection, the optimum deposition amount for a unit shot differs depending on the type of the resin material, the supply amount of the pellet, the temperature of the pellet, the degree of pressure reduction, and other operating conditions. Further, the optimum deposition amount can be obtained by changing at least one of the operating conditions such as the type of the resin material, the supply amount of the pellet, the temperature of the pellet, and the degree of pressure reduction.

Here, in the case of a certain kind of resin material and operating conditions such as a certain pellet supply amount, a pellet temperature, and a degree of pressure reduction, the optimum deposition amount is in the cylinder (Case 1). In addition, in the case of operating conditions such as the type of other resin material, the other supply amount, the temperature of the pellet, and the degree of pressure reduction, the optimum deposition amount overflows from the inside of the cylinder and is located at the position of the pellet supply body. Thus, in order to obtain a good molded product, it is necessary to carry out injection molding with setting the optimal operating conditions for the optimal deposition amount.

樹脂 If the pellets are injected beyond the optimum deposition amount, the resin purge becomes defective. Therefore, it is important to control the deposition amount so as not to exceed the optimum deposition amount for each operating condition such as the type of resin material, the amount of pellet supply, the temperature of the pellet, and the degree of pressure reduction. Here, for example, under a reduced pressure of 300 Torr or more, the supply amount is about 1 g / sec to about 7 g / sec. At a heating temperature of 60 ° C. under a reduced pressure of 100 Torr or more, the supply amount is about 1 g / sec to about 10 g / sec.

However, the injection molding machine is apt to cause troubles in the driving process. Therefore, even when the injection molding is performed under the optimum operating conditions, the accumulation amount of the pellets may start to increase beyond a certain amount at a certain time. In such a case, even if the optimum pellet supply amount continues to be supplied, the injection molded product becomes defective.

Therefore, it is necessary to control the amount of pellets deposited to always be the optimum amount. Basic control of the amount of deposited pellets is performed by the following method. Vary the supply of pellets. Alternatively, the supply time of the pellet is varied while keeping the supply amount of the pellet constant. Alternatively, supply is turned OFF-ON. Further, operating conditions such as the temperature of the pellet and / or the degree of pressure reduction are varied.

Therefore, in order to prevent the pellets from being deposited in excess of the optimum deposition amount, the deposition status is managed using a detector, for example, a position detection sensor. Here, at least one detector is placed between the position of the specified deposition amount and the position of the threshold value of the deposition amount. Preferably, the detector is located at a predetermined position between the specified deposition amount position and the deposition amount threshold value position. Further, the detector is placed at a specific position of the specified deposition amount, a threshold position of the threshold value of the deposition amount, and a predetermined position between these positions. It is preferable that the installation positions of these detectors are variably set in relation to the optimum deposition amount.

And in case 1 above, the optimal amount of deposition is in the cylinder. In this case, the detector is preferably provided in the cylinder, but it is difficult to provide the detector in the cylinder. Thus, the detector is placed as low as possible below the pellet feed, i.e. in the vicinity of the feed port of the cylinder, at a position which is assumed to be the threshold position for the amount of deposition. When the amount of the deposited pellets reaches the position of the detector, the supply of the pellets is temporarily stopped. When the accumulation amount of the pellets starts to drop below the position, the supply of the pellets under the optimum condition or the supply of the arbitrary amount is started.

In this case, the detector may use a counting sensor instead of the position detection sensor. The counting sensor measures the number of pellets passing through a certain position in the pellet supply in a unit time. In this case, pellets per unit time at which an optimum deposition amount is obtained are obtained in advance, and when the number of pellets exceeds this number and the number of pellets is supplied into the cylinder, the operating conditions are controlled to optimize the number of pellets. Feed the number of pellets into the cylinder.

ケ ー ス In case 2 above, the optimal deposition volume is in the pellet feed. In this case, the detector is located on the pellet feed. That is, the detector is placed at a predetermined position between the specified position of the specified deposition amount and the position of the threshold value of the deposition amount. Further, the detector is placed at a specific position of the specified deposition amount, a threshold position of the threshold value of the deposition amount, and a predetermined position between these positions.

Thus, in the former case, when the deposition amount of the pellet reaches the position of the detector placed at the predetermined position, the control of the deposition amount is performed by the above-described basic control method. In the latter case, when the deposition amount of the pellet reaches the position of the detector placed at a predetermined position, the control of the deposition amount is performed by the above-described basic control method.

And, especially when the amount of the deposited pellets reaches the position of the detector located at the threshold position, the control of the deposited amount temporarily stops the supply of the pellets, and the amount of the deposited pellets is reduced. When it begins to drop below the position, supply of pellets under optimum conditions or supply of an arbitrary amount is started. In this case, the deposition amount may be controlled by selecting either of the two detection methods. In this case, a counting sensor can be used instead of the position sensor as the detector.

Thus, in the above case, as the pellets accumulate past the detector, the detector sends that information to the system controller, which sends a feed control signal to the pellet feed controller. When this signal is sent, the pellet supply adjusting device changes the supply amount of pellets, or changes the supply time while keeping the supply amount of pellets constant, or temporarily turns off the supply. Therefore, the pellets are always deposited with the optimum deposition amount. In addition, the system controller controls the pellets to optimal operating conditions such as the temperature and the degree of pressure reduction.

Note that the step of specifying the optimum amount of deposition per shot and the step of melting and injecting the pellet having the optimum amount of deposition may be performed by the same injection molding machine or by different injection molding machines. Good.

In addition, in injection molding, the values of the optimal operating conditions, such as the pellet supply amount, pellet temperature, and the degree of decompression, at which the optimal deposition amount can be obtained, can be obtained from the recommended values described in specifications and pamphlets or by preliminary evaluation tests. The obtained value may be used. In this case, the injection may be performed using the recommended value or the like, but preferably, the injection is first performed using the recommended value, and the injected product is inspected by the above-described evaluation method, and the evaluation is performed. As a result, injection is performed under optimal working conditions. By using such known values, it is possible to shorten the time required to obtain the optimum deposition amount and the optimum operating conditions.

ペ レ ッ ト As described above, the control of the amount of deposited pellets is performed for two purposes. That is, one is a control for specifying an optimum deposition amount per unit shot for obtaining a good resin purge. The two controls are such that the deposited amount of the supplied pellets always exists within the optimum deposited amount per unit shot. When controlling the amount of deposited pellets, for example, the supply is adjusted by the above-described pellet supply adjusting device.

水分 Also, when the pellets are melted in the cylinder of the injection molding machine, moisture, gas and the like are discharged from the pellets. The present invention has a configuration for forcibly releasing these moisture and gas to the atmosphere. That is, these moisture and gas are released to the atmosphere under reduced pressure. Further, these moisture and gas are released to the atmosphere under reduced pressure together with air and inert gas introduced from the atmosphere.

水分 As described above, moisture and gas are released to the atmosphere under reduced pressure. At this time, if the rising flow of moisture or gas collides with the falling pellet, the falling of the pellet is hindered. Therefore, a specific supply amount of pellets cannot be supplied into the injection molding machine. The present invention has a structure that does not allow the upward flow of moisture or gas to contact the falling pellet. That is, the first section through which the rising moisture or gas passes is separated from the second section through which the falling pellets pass. And the 1st area where moisture and a gas pass is connected to a decompression device. The length of the member forming the second section is longer than the length of the member forming the first section. Thereby, contact can be reliably prevented and a specific amount of pellets can be reliably supplied to the injection molding machine.

水分 Furthermore, moisture and gas are discharged from inside the pellet during the melting process of the injection molding machine. Some of the moisture and gas are discharged to the inner surface of the mold when the resin is injected into the mold. The present invention has a configuration in which water and gas discharged from inside a pellet during the melting process of an injection molding machine and water and gas discharged to the inner surface of a mold when injected into a mold are released to the atmosphere under reduced pressure. Prepare. Further, the gas exhaust path body for discharging to the atmosphere is provided with a removing device for removing moisture and harmful substances in the gas. Therefore, no harmful substances are released to the atmosphere. Therefore, harmful substances such as dioxin generating substances contained in the resin are not released to the atmosphere.

When the pellets are undried resin pellets, it is preferable that the pellets supplied to the injection molding machine have been dried to some extent. The present invention includes a heating device that uses high-temperature gas discharged in a melting process of an injection molding machine. Preferably, the heating device comprises first and second heating devices. The second heating device is provided in the pellet supply path on the side of the injection molding machine.

Further, the pellets supplied into the injection molding machine have a cushion pressure when compressed by a screw. The range of variation in cushion pressure can be set to 5 mm ± 0.5 mm or less.
Further, since the pellet supply path is under reduced pressure, automatic supply of the pellets becomes possible. Further, the pellet supply path and the gas exhaust path are connected to one pressure reducing system. This simplifies the pellet supply and gas exhaust system.

Note that the above-described injection molding method according to the present invention only needs to include each step. Therefore, the order of each step is not limited to this order, and various orders can be adopted.
In addition, the present invention can include various modified configurations without being limited to this embodiment within the scope of the present invention.

As described above, the present invention can be applied to an injection molding machine in which a resin or the like is melted in a cylinder and injected from one end thereof under pressure, and of course, the resin or the like is melted in a cylinder and injected under pressure from one end thereof. The present invention is applicable even if it does not have to be the name of an injection molding machine as long as it performs the function described above.
Further, the injection molded products include various molded products such as electronic parts and mechanical parts.

1 is a schematic view of an injection molding system according to the present invention. It is the schematic of the pellet supply body which concerns on this invention. 1 is a schematic view of an injection molding system according to the present invention.

Explanation of reference numerals

DESCRIPTION OF SYMBOLS 10 Injection molding system 12 Storage tank 14 Air blower 16 Autoloader 18, 20 Vacuum shutoff valve 21 Level sensor 22 Pellet storage body 24 Pellet supply body 26 Injection molding machine 28 Pellet supply adjustment device

Claims (24)

The undried resin pellets are fed into the cylinder of the injection molding machine to perform the first injection, and after a predetermined time has elapsed from the first injection, the quality of the injected resin purge is inspected to obtain the optimum value per unit shot. An injection molding method for performing injection molding by performing injection with a deposition amount. (A) depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) performing injection molding with the optimal deposition amount;
An injection molding method comprising: (A) depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) detecting the amount of pellets supplied during injection molding;
(F) controlling the amount of pellets deposited based on the detection information;
(G) performing injection molding with the optimal deposition amount;
An injection molding method comprising: (A) depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) identifying optimum operating conditions for operating conditions such as the amount of pellet supply per unit shot, the degree of decompression, and the pellet temperature as a result of the inspection;
(E) injection molding under said optimal operating conditions;
An injection molding method comprising: (A) depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) controlling operating conditions such as the amount of pellet supply, the degree of depressurization, and the temperature of the pellet so that the optimal amount of deposition is present in the pellet supply;
(F) injection molding under said optimal operating conditions;
An injection molding method comprising: (A) depressurizing a gas exhaust path body to exhaust moisture and gas discharged from a mold and / or moisture and gas discharged from a pellet melted in a cylinder of an injection molding machine;
(B) supplying the undried resin pellets through a pellet supply path into a cylinder of an injection molding machine to perform a first injection;
(C) inspecting the quality of the resin purge injected after a lapse of a predetermined time from the first injection;
(D) specifying an optimum deposition amount per unit shot as a result of the inspection;
(E) a step of supplying the pellets supplied to the injection molding machine separately from moisture and gas discharged from the molten pellets;
(F) performing injection molding with the optimum deposition amount;
An injection molding method comprising: The pellets in the inspection process are characterized in that even if the pellets are continuously supplied into the cylinder of the injection molding machine, the amount of the pellets that are not overflown from the cylinder of the injection molding machine is supplied as one shot. The injection molding method according to claim 1, 2, 3, 4, 5, or 6. In place of the step of specifying the optimum operating conditions of the pellet supply amount, the degree of depressurization, and the temperature of the pellet, use a recommended value described in a specification or a catalog or an optimum value already obtained by evaluation. The injection molding method according to claim 5, wherein: 7. The injection molding method according to claim 2, wherein the step of specifying the optimum deposition amount is performed by changing operating conditions such as a pellet supply amount, a pellet temperature, and a degree of pressure reduction. 4. The injection molding method according to claim 3, wherein the deposition amount control step is controlled by changing a supply amount. 4. The injection molding method according to claim 3, wherein the deposition amount control step is controlled by changing a supply time while keeping a supply amount constant. 4. The injection molding method according to claim 3, wherein in the deposition amount control step, the supply is turned off and on. 4. The injection molding method according to claim 3, further comprising a step of changing the position to be detected. 7. The injection molding method according to claim 1, further comprising an expected supply step for supplying a gas such as air or an inert gas into the injection molding machine. 7. The injection molding method according to claim 1, wherein dried pellets or recycled resin is used in place of the undried pellets. An injection-molded article produced by the injection molding method according to claim 1. The undried resin pellets are fed into the cylinder of the injection molding machine to perform the first injection, and after a predetermined time has elapsed from the first injection, the quality of the injected resin purge is inspected to obtain the optimum value per unit shot. Injection molding machine for performing injection with the accumulation amount. 18. The injection molding machine according to claim 17, further comprising: a pellet accumulation amount control unit that controls at least one of operation conditions such as a pellet supply amount, a degree of pressure reduction, and a pellet temperature. 19. The injection molding machine according to claim 18, wherein said pellet accumulation amount control means includes a pellet supply adjusting device. 20. The injection molding machine according to claim 19, wherein the supply amount of the pellet is variable. 20. The injection molding machine according to claim 19, wherein the pellet supply adjusting device varies a supply time while keeping a supply amount constant. 20. The injection molding machine according to claim 19, wherein the pellet supply adjusting device turns off and on the supply. 18. The injection molding machine according to claim 17, further comprising: at least one detection device installed at a position of an optimal amount of deposition. An injection molded article produced by the injection molding machine according to claim 17.

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