JP2000000846A - Injection molding machine, pellet supply unit, method for injection molding, and injection molding article - Google Patents

Abstract

PROBLEM TO BE SOLVED: To completely remove a moisture and a gas in an undried resin pellet generated in a melt in an injection molding chamber by sensing a pellet amount in the chamber and controlling a supply amount of the pellets. SOLUTION: A supply of an undried resin pellet of a predetermined amount or more into an injection molding chamber 14 is sensed. A supply amount of the pellets to be supplied to the chamber is adjusted based on the sensed information. A moisture and a gas in the pellet supplied into the chamber are discharged in a melting step. A gas containing the moisture and the gas discharged from the pellet is exhausted under a reduced pressure into the atmosphere.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an injection molding machine, a pellet supply unit, an injection molding method and an injection molded article for performing resin molding using undried resin pellets.

[0002]

2. Description of the Related Art In an injection molding machine conventionally used conventionally, undried resin pellets are put in a dryer set at a predetermined temperature in advance and dried for several days until a predetermined dry state is obtained. You. Moisture and gas in the undried resin pellets are sufficiently removed in the dryer. Then, the dried pellets from which moisture and gas have been removed are introduced into an injection molding machine. For this reason, it is necessary to pay sufficient attention to the quality control of the moisture and gas of the pellet before the pellet is put into the injection molding machine. Further, it took time to dry the undried resin pellets. In addition, the installation of the dryer required a high cost.

As a method to solve this problem, it has been proposed to omit the drying step of the undried resin pellets before putting the undried resin pellets into an injection molding machine. That is, it is considered that the undried pellets are directly introduced into a dryer (Japanese Patent Application Laid-Open No. 7-60803). In the injection molding machine having the above-described configuration, a Venturi tube is provided in a compression zone of the screw to reduce the pressure in the Venturi tube. The inventor believes that by removing the water and gas in the molten pellets from the compression zone under reduced pressure, the water and gas in the resin pellets being melted are discharged to the atmosphere.

[0004]

The wet resin pellets are conveyed by screws from the feed zone to the compression zone and continue to melt. The moisture and gases in the undried resin pellets are dissolved and evaporated from the surface while the pellets move from the feed zone to the compression zone. In this compression zone, moisture and gas discharged from the undried resin pellets in the vicinity of the Venturi tube during melting are exhausted. However, the disadvantage is that most of the water and gas remains in the melting pellet, and thus the water and gas in the undried resin pellets are not exhausted completely.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and detects the amount of pellets in an injection molding chamber and controls the supply amount to thereby prevent the generation of melt generated in the injection molding chamber. It is intended to completely remove moisture and gas in the dried resin pellet. In consideration of the fact that the removal of moisture and gas in the pellet cannot be completely removed in the compression zone of the screw as in the past, the moisture discharged from the pellet in the melting process between the supply zone of the screw and the compression zone. And exhaust gas from the supply zone.

Further, the present invention can eliminate a drying step before being put into an injection molding machine, can improve productivity and reduce the cost of production equipment, and can perform molding by injection molding. The strength of the article can be increased. Further, since the water and the gas discharged from the inside of the pellet are not supplied into the mold, the life of the mold can be prolonged and the number of times of cleaning can be reduced.

[0007]

An injection molding machine according to the present invention melts undried resin pellets supplied through a pellet storage into an injection molding chamber while stirring the resin pellets in the injection molding chamber. A detecting device for detecting that a predetermined amount or more of the pellets are supplied into the injection molding chamber in an injection molding machine that injects a molten resin from an injection hole provided at one end of the injection molding chamber. And a pellet supply amount adjusting device for adjusting the supply amount of the pellets to the injection molding chamber based on information from the position detection device; and supplying gas into the injection molding chamber from outside the injection molding chamber. Gas supply means for discharging gas containing water and gas evaporated from the pellets during the melting process in the injection molding chamber. And a pressure reducing device.

The injection molding machine according to the present invention melts the undried resin pellets supplied through the pellet storage into the injection molding chamber while stirring the resin pellets in the injection molding chamber. In an injection molding machine that injects molten resin from an injection hole provided at one end,
A detecting device for detecting that a predetermined amount or more of the pellets are supplied into the injection molding chamber, and adjusting a supply amount of the pellets to the injection molding chamber based on information from the detecting device. The apparatus includes a pellet supply amount adjusting device, and a pressure reducing device for exhausting a gas containing moisture evaporated from the pellets in the melting process in the injection molding chamber.

In the injection molding machine according to the present invention, the detection device is disposed in the pellet storage.

[0010] In the injection molding machine according to the present invention, a predetermined supply amount of undried resin pellets is supplied at least from the pressure in the injection molding chamber or the pellet storage.

In the injection molding machine according to the present invention, the pressure reducing device is provided below the storage body.

The injection molding machine according to the present invention further comprises a heating device for heating the undried resin pellets before being supplied to the injection molding chamber.

A pellet supply unit according to the present invention detects a pellet storage for supplying undried resin pellets into an injection molding chamber and detects that a predetermined amount or more of the pellets has been supplied into the injection molding chamber. A detecting device for adjusting the supply amount of the pellets into the injection molding chamber based on information from the detecting device, and a pellet supply amount adjusting device for adjusting the supply amount of the pellets from the pellets in the melting process in the injection molding chamber. A decompression device for discharging gas containing evaporated moisture or gas.

In the injection molding method according to the present invention, a step of supplying undried resin pellets through a pellet storage to an injection molding chamber and detecting that a predetermined amount or more of the pellets have been supplied into the injection molding chamber. Adjusting the supply amount of the pellets into the injection molding chamber based on the detection information; and exhausting the gas containing moisture and gas evaporated from the pellets during the melting process to the outside of the injection molding machine. And extruding the pellets melted in the injection molding machine from the other end of the injection molding machine and injecting them into a mold.

An injection-molded article manufactured by the injection molding machine or the injection molding method according to the present invention.

[0016]

The undried resin pellets are supplied into the injection molding chamber through the pellet storage. In this case, it is preferable that a predetermined supply amount of undried resin pellets is supplied into the injection molding chamber. The pellets are conveyed while rotating into the feed, compression and metering zones of the screw. During this time, the undried pellets are heated and melted. In this melting step, moisture and gas in the undried resin pellets are released.

Here, the rotation of the screw in the cylinder is hardly performed constantly. Therefore,
When the undried resin pellets are continuously supplied into the injection molding chamber, the undried resin pellets overflow from the injection molding chamber and begin to accumulate in the pellet storage cylinder. If this state continues, exhaust of moisture, gas, and the like generated from the undried resin pellets during the melting process in the injection molding chamber is blocked. For example, when resin pellets exceeding 125 cc are supplied into the injection molding chamber in a 50-ton injection molding machine, the resin pellets overflow from the injection molding chamber.

As a result, moisture and gas are not exhausted to the outside even when the exhaust device is used, and moisture remains in the undried resin pellets, so that a molded article of good quality cannot be obtained.
Then, the detection device is attached to a predetermined position in the storage body, and the injection molding chamber becomes equal to or larger than a predetermined amount, and undried resin pellets from the injection molding chamber start to be deposited in the storage cylinder. Detecting that the deposit has reached a predetermined position in the storage, a signal of information indicating that the inside of the injection molding chamber has exceeded a predetermined amount is transmitted to the pellet supply amount adjusting device via the control device. The adjusting device adjusts the supply amount based on this information, and adjusts the adjusting device so that the undried resin pellets do not always overflow the injection molding chamber by a predetermined amount or more. Thus,
There will always be a certain amount of pellets in the injection molding chamber.

The detector can detect the amount of pellets contained in the supply zone as soon as it is closer to the supply zone. That is, since the information that the pellet has overflowed from the supply zone is transmitted to the pellet supply amount control device quickly, the supply amount from the pellet supply amount control device can be quickly adjusted. In this way, it is possible to keep a constant amount of pellets in the supply zone while minimizing the state in which the pellets overflow from the supply zone.

The above-mentioned predetermined supply amount of the undried resin pellets refers to a supply amount that does not include moisture or gas in a molded article formed by injection molding with an injection molding machine.
The predetermined supply amount is determined based on the pressure in the injection molding chamber or the storage, and the heating temperature of the pellet. The predetermined supply amount can be increased by increasing the degree of pressure reduction. By performing the heating, it is possible to increase the predetermined supply amount even if the degree of pressure reduction is reduced. Further, by increasing the heating temperature and the degree of pressure reduction, the predetermined supply amount can be increased.

The predetermined predetermined supply amount is 300 To.
About 1 g / sec to about 7 g / s under reduced pressure of rr or more
ec. Here, under a reduced pressure of 200 Torr or less, a good injection molded product cannot be obtained regardless of the supply amount of pellets. By heating the undried resin pellets under reduced pressure at a temperature of about 60 ° C. for several hours, the predetermined supply amount of the pellets is about 1 g / sec to about 7 g / sec. 100T
orr, at a temperature of about 60 ° C., a predetermined supply amount is about 1 g /
sec to about 7 g / sec.

A gas from the outside of the injection molding machine, for example, atmospheric air, preferably warm air is supplied into the injection molding chamber. The air from the atmosphere is supplied from the side opposite to the injection hole of the injection molding machine, for example, from the other end. In a commonly used FANUC 50 ton injection molding machine, the air intake is about 200
Nl / min to about 300 Nl / min. Here, the gas has an effect of absorbing moisture discharged from the molten pellets.

The released moisture and gas are discharged from the injection molding machine to the atmosphere by a pressure reducing device. That is, moisture or gas existing in the injection molding chamber or the storage is discharged from the injection molding machine to the atmosphere. Since water and gas are completely removed from the injected resin, the molded article does not contain water or gas. The pressure reducing device constituting the exhaust device should be at least about 300 Torr, preferably about 4 Torr.
By adjusting the pressure to 00 Torr or more, the moisture evaporated from the pellets can be discharged to the atmosphere.

[0024] The decompression device preferably comprises a gas intake pipe below the pellet storage. By disposing a decompression device at this position, moisture and gas discharged from the inside of the injection molding chamber can be efficiently exhausted to the atmosphere, and the pellets can smoothly fall in the pellet supply device.

A plurality of injection molding machines according to the present invention are arranged, and the plurality of the injection molding machines arranged are connected to a reduced number of decompression devices. Thus, the layout of the molding factory can be simplified, and the capital investment can be reduced.

The articles to be injection-molded by the injection molding machine and the injection molding method according to the present invention include functional parts that perform passive and active functions by resin molding, pellets for molding machines, and the like.

[0027]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 1 shows a cross section of an injection molding machine. The undried nylon resin pellets that have not been dried here
Preferably, a predetermined amount of undried resin pellets is supplied to the injection molding machine. In the figure, reference numeral 10 denotes an injection molding machine. The injection molding machine is provided with a heater 12 outside thereof. The temperature of the heater 12 is set to 280 ° C. The cylinder has an injection molding chamber 14 therein. The injection molding chamber 14 has a screw 16 therein for stirring the undried resin pellets.

The screw 16 has a metering zone 18, a compression zone 20 and a feed zone 22. The metering band 18
Is the shallowest part of the screw. Thus, a large shearing force is applied to the resin pellets in the measuring zone 18. The pellet is raised to a homogeneous temperature with self-heating. In the zone, the resin pellets are melted and kneaded. By this action, a certain amount of resin pellets is sent to the nozzle side. There is a gap between the resin pellets supplied to the compression zone 20. Therefore, when the resin pellets are melted, the volume is reduced to about half. In order to compensate for this decrease in volume, it is necessary to reduce the space through which the resin passes. Therefore, the groove of the screw 16 is formed shallow. This has the effect of compressing the molten resin pellets to increase the heat generation effect and increase the resin pressure. The supply zone 22 sends the resin to the compression zone as a solid or a part of the resin dissolved. An injection port 240 is provided at one end of a cylinder of the injection molding machine, and an opening 26 for taking in atmospheric air is provided at the other end.

Numeral 34 denotes a pellet storage, and undried resin pellets, preferably a predetermined supply amount of undried resin pellets, are supplied into the injection molding chamber 14 through the pellet storage 34. Reference numeral 38 denotes a decompression device. The pressure reducing device 38 is a vacuum pump 4
0 is provided. The exhaust port 42 is attached below the pellet storage 34. The decompression device 38 has a function of sucking a gas containing water and gas generated from the molten pellets and exhausting the gas to the atmosphere. At that time the degree of vacuum of the decompression device is about 100T
or more, preferably about 400 Torr or more.

The predetermined supply amount of the undried resin pellets is determined from the supply amount of the pellets, the pressure in the injection molding chamber, the heating temperature of the pellets, and the like. The predetermined supply amount is about 1 g / sec to about 7 g / sec under a reduced pressure of 300 Torr or more. By heating the undried resin pellets under reduced pressure at a temperature of about 60 ° C. for several hours, the predetermined supply amount of the pellets is about 1 g / sec.
c to about 7 g / sec. 100 Torr or more, about 6
At a temperature of 0 ° C., the predetermined supply amount is about 1 g / sec to about 7 g / sec.
sec.

Normally, since the rotation of the screw 16 in the injection molding chamber is hardly constantly performed, if a predetermined amount of the undried resin pellet is continuously supplied into the injection molding chamber, Undried resin pellets overflow the injection molding chamber and begin to accumulate in the pellet reservoir. If this state continues, exhaust of moisture, gas, and the like generated from the undried resin pellets during the melting process in the injection molding chamber is blocked.

As a result, moisture and gas are not exhausted to the outside even if the pressure reducing device 38 is used, and moisture remains in the undried resin pellets, so that a high quality molded product cannot be obtained. Then, the detecting device 44 is attached to a predetermined position in the storage body, and it is detected that the undried resin pellets have been deposited from the injection molding chamber at the predetermined position of the storage body 34, and the inside of the injection molding chamber becomes equal to or more than a predetermined amount. A signal of the information is transmitted to a pellet supply amount adjusting device 50 via a control device (not shown). For example, when resin pellets exceeding 125 cc are supplied into the injection molding chamber in a 50-ton injection molding machine, the resin pellets overflow from the injection molding chamber. When this signal is transmitted to the adjusting device, the adjusting device 50 adjusts the supply amount so that the undried resin pellets do not always overflow a predetermined amount from the injection molding chamber. Thus, there is always a certain amount of pellets in the injection molding chamber.

The detecting device 44 may have any function as long as it can detect that the pellet has reached a predetermined deposition position. For example, a level sensor is used as the detection device 44. Further, although the detection device 44 is attached to the pellet storage body 34, it is preferable that the detection device 44 is installed as close to the screw supply zone 22 as possible. The closer to the supply zone, the sooner the amount of pellets in the supply zone can be detected. That is, since the information that the pellets have overflowed from the supply zone can be transmitted to the pellet supply amount adjusting device quickly, the pellet supply amount adjusting device 5
The supply from zero can be adjusted quickly. In this way, it is possible to keep a constant amount of pellets in the supply zone while minimizing the state in which the pellets overflow from the supply zone.

The pellet feed rate adjusting device 50 is provided inside the pellet storage body 34. The adjusting device 50 includes a spiral supply unit 54 having a predetermined pitch provided at one end of the rotating shaft 52 and a drive motor 56 attached to the other end. Then, the pellets are conveyed through the gap of the spiral supply unit 54. At this time, the feed rate of the pellets conveyed through the spiral gap is adjusted by adjusting the rotation speed and / or pitch of the rotating shaft. Note that the pellet supply amount adjusting device 50 is not limited to the above-described configuration, and various adjusting mechanisms, for example, an adjusting blade for adjusting the diameter of the pellet supply path may be provided. Further, the pellet supply amount adjusting device 50 may be provided independently of the pellet storage body 34.

Reference numeral 58 denotes a heating device for preliminary heating the undried resin pellets when the undried resin pellets pass through the pellet storage 34. By preheating and heating the undried resin pellets at, for example, 60 ° C. for about 30 minutes, a good injection molded product can be obtained even if the supply amount of the pellets per unit time is large and the degree of pressure reduction is reduced. In this case, by appropriately adjusting the supply amount, the degree of pressure reduction can be reduced to 100.
Good products can be obtained even at Torr or less.

The gas supply means is the opening 60 provided at the other end opposite to the injection hole of the cylinder of the injection molding machine as described above. In addition, an introduction port may be provided near the supply zone of the screw in order to introduce a gas such as air from the outside of the cylinder. Further, the gas introduced into the cylinder may be an inert gas other than air. Further, the gas is preferably 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.

The present invention is not limited to this embodiment and can include various modified configurations.

[0039]

According to the present invention, it is possible to completely remove water and gas in the pellets generated during melting of the undried resin pellets. Further, moisture and gas in the undried resin pellets can be completely removed in a short time. The strength of the injection molded product is increased. Thus, according to the present invention, it is possible to omit the pre-drying step before introducing the undried resin pellets into the injection molding machine as in the related art, thereby improving the productivity and reducing the cost of the production equipment. The life of the mold can be prolonged and the number of times of cleaning can be reduced.

[Brief description of the drawings]

FIG. 1 is a schematic view of an injection molding machine according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1; Undried resin pellet 10; Injection molding machine 12; Heater 14; Injection molding chamber 16; Screw 24; Injection port 26; Opening 20; Compression zone 22; Supply zone 40; Vacuum pump 34; Pellet reservoir 38; 44; detection device 50; pellet supply amount adjustment device 58; heating device

Claims (9)

[Claims] An injection hole provided at one end of the injection molding chamber is melted while stirring the undried resin pellets supplied to the injection molding chamber through the pellet storage inside the injection molding chamber. In an injection molding machine that injects a molten resin from a detection device for detecting that a predetermined amount or more of the pellets are supplied into the injection molding chamber, and based on information from the position detection device, A pellet supply amount adjusting device for adjusting the supply amount of the pellets to the injection molding chamber, gas supply means for supplying gas into the injection molding chamber from outside the injection molding chamber, and A pressure reducing device for discharging a gas containing water and gas evaporated from the pellets during the melting process. Molding machine. 2. An injection hole provided at one end of the injection molding chamber while melting the undried resin pellets supplied through the pellet storage into the injection molding chamber while being stirred in the injection molding chamber. In the injection molding machine by injecting the molten resin from the, a detection device for detecting that a predetermined amount or more of the pellets are supplied into the injection molding chamber, and the pellets based on information from the detection device A pellet supply amount adjusting device for adjusting the supply amount to the injection molding chamber, and a decompression device for exhausting a gas containing moisture evaporated from the pellets in the melting process in the injection molding chamber. Injection molding machine. 3. The injection molding machine according to claim 1, wherein the detection device is provided in the pellet storage. 4. An injection molding machine according to claim 1, wherein a predetermined amount of undried resin pellets is supplied at least from the pressure in the injection molding chamber or the pellet storage. . 5. The injection molding machine according to claim 1, wherein the pressure reducing device is provided below the storage body. 6. The injection molding machine according to claim 1, further comprising a heating device for heating the undried resin pellets before being supplied to the injection molding chamber. 7. A pellet storage for supplying undried resin pellets into an injection molding chamber, a detecting device for detecting that a predetermined amount or more of the pellets have been supplied into the injection molding chamber, A pellet feed rate adjusting device for adjusting the feed rate of the pellets into the injection molding chamber based on the information from the detection device, and water and gas evaporated from the fat pellets during the melting process in the injection molding chamber. A pellet supply unit including a decompression device for discharging a gas containing the pellet. 8. A step of supplying undried resin pellets through a pellet storage to an injection molding chamber, a step of detecting that a predetermined amount or more of the pellets have been supplied into the injection molding chamber, and Adjusting the supply amount of the pellets into the injection molding chamber on the basis of the above, discharging the gas containing water and gas evaporated from the pellets in the melting process to the outside of the injection molding machine, and melting the gas in the injection molding machine. Extruding the pellet thus obtained from the other end of the injection molding machine and injecting it into a mold. 9. An injection molded article produced by the injection molding machine according to claim 1 or 2 or the injection molding method according to claim 8.