WO2009062433A1

WO2009062433A1 - Method of foaming plastic injection molding and machine thereof

Info

Publication number: WO2009062433A1
Application number: PCT/CN2008/072607
Authority: WO
Inventors: Chih-Shiang Han
Original assignee: Lu, Hsaio-Ting
Priority date: 2007-11-09
Filing date: 2008-10-07
Publication date: 2009-05-22
Also published as: CN101428462A; CN101428462B

Abstract

Disclosed herein are a method of foaming plastic injection molding and the machine thereof. The method comprises: forming the mixture of melt plastics and gas in a feeding barrel (1) by a screw (2), which is leaded into an accumulating barrel (7), then is pushed into an injection barrel (4) and is injected by the pressure; measuring the present injection amount of the injection barrel (14), the present pushing amount of the accumulating barrel (7), and the present output velocity of the feeding barrel (1); adapting the next pushing amount of the accumulating barrel (7) to be equal to the present injection amount of the injection barrel (14) and adjusting the screw rotary speed and the gas input velocity to ensure the uniform dispersion of gas in plastics and to make the output velocity of the feeding barrel (1) fit the next pushing amount of the accumulating barrel (7) by a central controller. The machine thereof comprises: the measuring assembly (11) of pushing amount of the accumulating barrel (7), the measuring assembly (19) of injection amount of the injection barrel (14), a servomotor (4), an assembly delivering gas (3), a central controller connecting with them and etc.

Description

Foam plastic injection molding method and injection device thereof

(1) Technical field

The present invention relates to a foamed plastic injection molding method and an injection device thereof, mainly for producing a foamed plastic by an injection molding method and apparatus.

(2) Background technology

Foamed plastic is generally formed by feeding plastic into a feeding tube equipped with a screw and injecting gas. The feeding tube is equipped with a heating device to melt the plastic. Under the stirring of the screw, the melted plastic is thoroughly mixed with the gas to form an inner portion. Plastic melt containing bubbles. The melt is discharged from the front end of the feed tube and cooled by the mold. Since the foamed plastic manufacturing process must ensure uniform mixing of the molten plastic and the gas at a constant rotation of the screw and maintain a uniform pressure in the material tube, the dissolution of the bubbles in the plastic will be uneven or The expansion phenomenon occurs, and the molding of the material will be unstable at this time. Due to this characteristic of foamed plastics, it is generally only suitable for extrusion molding, and is suitable for the manufacture of profile products.

For general injection molding products, foam molding is almost impossible to use in current injection molding machines. The key to injection molding machinery not adapting to foamed plastics is that the injection mechanism is produced in a single mold. Each injection of a mold requires the input of the plastic melt to be stopped, and the smooth formation and feeding of the foamed plastic melt must be continuous. In order to maintain the stable melting of the gas in the plastic and the stability of the material pressure, the bubbles in the material are evenly distributed to ensure the quality of the product. Once paused, the pressure in the chamber will change, the gas will not continue to enter and melt evenly in the plastic, and the bubbles in the remaining plastic melt will immediately expand. Destroy the pressure environment in the cavity, so that the next mold plastic melt can not be smoothly fed. The contradiction between the two cannot be reconciled. However, due to the soaring prices of raw materials, the characteristics of foamed plastics to save raw materials without reducing the structural strength have become very attractive. Actual production has the demand for injection molding methods and equipment for foamed plastics. However, the existing injection foaming technology cannot effectively solve this problem.

(III) SUMMARY OF THE INVENTION The present invention is to overcome the above disadvantages of the prior art, and to provide a reliable foamed plastic injection molding method and an injection device therefor. The foamed plastic injection molding method of the present invention comprises the following steps:

1. Inject plastic and gas into the feeding barrel, and melt and mix the above-mentioned gas to form a mixed foamed plastic by heating and screw stirring.

2. Introduce the mixed foamed plastic melt into another hopper; • Pour the plastic that fits the capacity of one shot into the barrel while pressure control and compensation in the chamber of the hopper. Keep the pressure in the chamber of the storage machine cylinder stable; 4· Pressurize the injection barrel and shoot out;

⁵ · Measure the current injection volume of the injection barrel, the current extrusion volume of the storage barrel, and the current output speed of the loading barrel;

6. According to the current injection quantity of the injection barrel, adjust the next extrusion amount of the storage barrel to be equal to the current injection amount of the injection barrel; and adjust the rotation speed of the screw on the feeding barrel to control the addition of plastic. Speed, simultaneous adjustment The whole intake speed is matched with the plastic addition speed to ensure the uniformity of the gas in the plastic, so that the output speed of the feeding barrel is matched with the next pressing amount of the storage barrel.

The special equipment foam plastic injection molding device for the foam plastic injection molding method of the present invention comprises a feeding barrel for injecting plastic and gas to form a bubble-containing plastic melt, and a gas conveying device is connected to the feeding barrel The hopper and the heating device are equipped with a screw in the inner cavity of the feeding barrel, and the screw is connected to the rotary driving mechanism; the front end of the inner cavity of the feeding machine communicates with the inner cavity of the storage machine barrel, and the storage machine barrel also has a quantitative pressing mechanism and pressure The output measuring mechanism; the front end of the volume of the storage barrel is connected to the inner cavity of the barrel through a check valve, and the injection barrel is further equipped with a quantitative injection mechanism and an injection quantity measuring mechanism, and the front end of the injection barrel is equipped with a nozzle; Further, there is an injection amount measuring mechanism that connects the injection barrel, a discharge amount measuring mechanism of the stocker cylinder, a servo motor of a screw of the feeding barrel, and a central controller of an air intake mechanism of the gas conveying device, The central controller compares the secondary injection amount of the injection barrel and the current extrusion amount of the storage barrel, and outputs an adjustment command signal to the quantitative pressure of the storage barrel when the two are not equal. The mechanism makes the next extrusion amount of the storage barrel equal to the current injection amount of the injection barrel; and sends an adjustment command signal to the servo motor of the screw on the loading barrel and the air intake mechanism of the gas transmission device to control the plastic The speed is added, and the intake speed is adjusted to match the plastic addition speed to ensure the uniformity of the gas in the plastic, so that the output speed of the feeding barrel is matched with the next pressing amount of the storage barrel.

Further, the quantitative pressing mechanism of the hopper barrel has the following structure: a first annular bearing seat is mounted in the cavity of the hopper barrel, and the first piston rod is slidably mounted in the first bearing seat, first The piston rod is sealingly engaged with the first bearing seat, the first piston rod and There is a gap between the walls of the cavity, and the material inlet of the cavity abuts against the first bearing seat; the rear part of the first piston rod cooperates with the trigger switch of the oil cylinder and the oil cylinder.

Further, the quantitative injection mechanism of the injection barrel has the following structure: a second annular bearing seat is mounted in the injection cavity of the injection barrel, and the second piston rod is slidably mounted in the second support seat, the second piston rod a sealing fit with the second bearing seat, a gap between the second piston rod and the wall of the injection cavity, the material inlet of the injection cavity abutting the second bearing seat; the rear part of the second piston rod and the pushing cylinder, the top Push cylinder trigger switch fit.

Further, the hopper barrel is further provided with a pressure detecting device for detecting the pressure in the cavity and a pressure control device for receiving the signal of the pressure detecting device and adjusting the cylinder pressure in the quantitative pressing mechanism according to the signal. By controlling the pressure inside the hopper, the stability and uniformity of the bubbles in the bubble-containing plastic melt can be further maintained, and the bubble density of the product is even and stable.

Further, the front end of the injection barrel is connected to the nozzle by a stirring device.

The injection amount measuring mechanism of the injection barrel and the discharge amount measuring mechanism of the stocker cylinder are a potentiometer or an optical scale.

In order to simplify the mechanics and control, the quantitative injection mechanism of the injection barrel has the same dimensions as the volume and piston rod of the quantitative extrusion mechanism of the storage barrel. The storage capacity of the hopper barrel 7 is greater than the capacity of the injection barrel 14.

The invention realizes the production of the foamed plastic by the establishment of the storage machine cylinder as the intermediate transition station, taking into consideration the contradiction between the intermittent feeding of the injection molding method and the continuous generation of the foamed plastic. Expanding the application range of foamed plastics, it can save plastics, promote environmental protection, and reduce the cost of plastic products. The barrels of the quantitative injection (extrusion) mechanism on the existing injection molding machine are all piston type. The injection tube has a nozzle at the front end and a hydraulic cylinder at the rear of the piston. When the piston chamber is fed, the pressure of the liquid material is used to retreat the piston to increase the volume of the piston chamber. Since the liquid is not completely ejected at the time of injection, the material remains on the end face of the piston, and the feed of the piston chamber is the front end injection type. Therefore, a dead space is formed near the end face of the piston, and the material here always remains. On the end face of the piston, the material of the end face of the material is carbonized. Secondly, the repeated movement of the piston tends to wear the inner wall of the cavity. On the other hand, the piston cavity is sealed by the piston and the cavity wall. There must be a precise size fit between the two, and the machining requirements are high. Therefore, the barrel and the piston are used. In a short period of time, overhaul is required, and the fitting size of the piston and the inner wall of the barrel is corrected, and the use cost is greatly increased. Finally, the piston needs to be sealed to the inner wall of the barrel, and the injection speed is slow. The piston can only be pushed in the barrel at a low speed, otherwise the inner wall of the barrel will be scratched.

The feeding mode of the cavity of the quantitative injection (extrusion) mechanism of the present invention is a backward type, which ensures that there is no material dead angle and can effectively prevent carbonization of the material. Secondly, there is no friction between the piston rod and the cavity wall, and no sealing is needed. On the one hand, the processing precision of the cavity wall is reduced, on the other hand, the wear of the cavity wall is eliminated, the service life of the barrel is prolonged, and the service life can be eliminated. Frequent overhauls reduce maintenance costs and increase production efficiency. Finally, the invention also ensures that the cavity walls are not subject to wear when the injection speed is increased.

The invention has the advantages of providing a reliable foaming plastic injection molding method and an injection device thereof, and realizing the injection molding production of the foamed plastic, the bubble density of the product is uniform, and the mechanical device can prevent the material from being carbonized and durable in the material tube. , the injection speed is fast.

(4) Description of the drawings Figure 1 is a schematic view of the structure of the present invention

2 is a schematic diagram of the pressure control in the cavity of the hopper barrel of the present invention;

(5) Specific implementation methods

The invention will be further described below with reference to the accompanying drawings

Embodiment 1

Refer to Figure 1:

The foamed plastic injection molding method of the present invention comprises the following steps:

1. Injecting plastic and gas into the feeding barrel, melting the plastic and mixing with the gas to form a mixed foamed plastic melt by heating and screw stirring;

2. introducing the previously mixed foamed plastic melt into a hopper barrel;

3. The plastic which is suitable for the injection capacity is melted into the barrel, and the pressure is controlled and compensated in the chamber of the storage barrel to keep the pressure in the chamber of the storage machine stable;

4. Pressurizing the injection barrel and injection molding;

5. Measure the current injection volume of the injection barrel, the current extrusion volume of the storage barrel, and the current output speed of the feeding barrel;

6. According to the current injection quantity of the injection barrel, adjust the next extrusion amount of the storage barrel to be equal to the current injection amount of the injection barrel; and adjust the rotation speed of the screw on the feeding barrel to control the addition of plastic. Speed, at the same time adjust the intake speed to match the plastic addition speed, to ensure the uniformity of the gas in the plastic, so that the output speed of the feeding barrel is matched with the next extrusion of the storage barrel.

A small difference must be given to the small difference between the current injection volume of the injection barrel and the current extrusion volume of the storage barrel. The accumulated difference will cause interference or interruption in the flow channel. The storage tank can not be adjusted, causing the feeding cylinder to not run continuously or the material pressure conditions in the machine are discontinuous, thereby destroying the pressure control conditions, causing the bubbles in the foamed plastic to expand, or the gas cannot be uniformly mixed with the plastic. , interrupt normal production.

The special equipment foam plastic injection molding device for the foam plastic injection molding method of the present invention comprises a feeding barrel 1 for injecting plastic and gas to form a bubble-containing plastic melt, and the feeding barrel 1 is connected with the input. The gas device 3, the hopper, the heating device, the inner cavity of the feeding barrel is provided with a screw 2, and the screw 2 is connected to a rotary driving mechanism comprising a servo motor 4, a speed reducer 5, and a transmission device 6.

The front end of the inner cavity of the feeding barrel 1 communicates with the inner cavity of the hopper barrel 7, and the hopper barrel 7 also has

The front end of the chamber of the hopper 7 is connected to the inner chamber of the barrel 14 through a check valve 16, and the injection barrel 14 is also equipped with a quantitative injection mechanism and an injection amount measuring mechanism for injection.

The front end of the 14 is equipped with a nozzle 12.

The present invention is provided with an injection amount measuring mechanism 19 for connecting the above-described injection barrel 14, an ejection amount measuring mechanism 11 of the hopper barrel, a servo motor 4 of the screw 2 of the charging machine barrel 1, and an air inlet mechanism of the cymbal device 3. The central controller, said central controller is compared when it is fired;

The quantitative pressing mechanism that outputs the adjustment command signal to the stocker cylinder 7 when the two are not equal causes the next pressing amount of the stocker cylinder 7 to be equal to the current shot amount of the shooting barrel 14. The central controller simultaneously sends an adjustment command signal to the servo motor 4 of the screw 2 of the loading barrel 1 and the air intake mechanism of the gas conveying device 3 to control the joining speed of the plastic, and simultaneously adjust the intake speed to match the plastic joining speed. To ensure the uniformity of the gas in the plastic, so that the filling machine 1 The output speed is adapted to the next extrusion of the magazine barrel 7.

The central controller is a microprocessor that is electrically connected to other components.

The injection amount measuring mechanism 19 of the injection barrel 14 and the extrusion amount measuring mechanism 11 of the hopper barrel 7 are potentiometers or optical scales, or other mechanisms capable of measuring the displacement distance.

The quantitative extrusion mechanism of the hopper barrel 7 and the quantitative injection mechanism of the injection barrel 14 may employ a piston injection mechanism of a conventional injection molding machine injection mechanism. A piston is arranged in the cavity of the barrel, and the pressure generated by the material entering the cavity forces the piston to retreat to expand the volume to a certain amount, and then the piston touches the trigger switch of the pushing cylinder, and the cylinder pushes the piston to make the material injection molding.

The invention realizes the production of the foamed plastic by the establishment of the storage machine cylinder as the intermediate transition station, taking into consideration the contradiction between the intermittent feeding of the injection molding method and the continuous generation of the foamed plastic. Expanding the application range of foamed plastics, it can save plastics, promote environmental protection, and reduce the cost of plastic products. Embodiment 2

Refer to Figures 1 and 2:

The difference between this embodiment and the first embodiment is the improvement of the quantitative extruding mechanism of the hopper barrel 7 and the quantitative injection mechanism of the ejector barrel 14, and the rest is the same as the first embodiment.

The quantitative pressing mechanism of the hopper barrel 7 has the following structure: a first annular bearing seat 8 is mounted in the cavity of the hopper barrel 7, and the first piston rod 9 is slidably mounted in the first bearing seat 8. The first piston rod 9 is sealingly engaged with the first bearing seat 8, the first piston rod There is a gap between the chamber 9 and the cavity wall, and the material inlet of the cavity abuts against the first bearing seat 8; the rear portion of the first piston rod 9 cooperates with the cylinder 10 and the cylinder 10 to trigger the switch.

The quantitative injection mechanism of the injection barrel 14 has the following structure: a second annular bearing seat 17 is mounted in the injection cavity of the injection barrel 14, and the second piston rod 15 is slidably mounted in the second support base 17, The second piston rod 15 is in sealing engagement with the second bearing seat 17, and there is a gap between the second piston rod 15 and the wall of the injection chamber, and the material inlet of the injection chamber abuts against the second bearing seat 17; the second piston rod 15 The rear portion cooperates with the trigger cylinder 18 and the jacking cylinder 18 trigger switch.

In order to simplify the mechanics and control, the quantitative injection mechanism of the injection barrel 14 has the same dimensions as the chamber and the piston rod of the quantitative extrusion mechanism of the magazine barrel 7. The storage capacity of the hopper barrel 7 is greater than the capacity of the injection barrel 14.

The barrels of the quantitative injection (extrusion) mechanism on the existing injection molding machine are all piston type. The injection tube has a nozzle at the front end and a hydraulic cylinder at the rear of the piston. When the piston chamber is fed, the pressure of the liquid material is used to retreat the piston to increase the volume of the piston chamber. Since the liquid is not completely ejected at the time of injection, the material remains on the end face of the piston, and the feed of the piston chamber is the front end injection type. Therefore, a dead space is formed near the end face of the piston, and the material here always remains. On the end face of the piston, the material of the end face of the material is carbonized. Secondly, the repeated movement of the piston tends to wear the inner wall of the cavity. On the other hand, the piston cavity is sealed by the piston and the cavity wall. There must be a precise size fit between the two, and the machining requirements are high. Therefore, the barrel and the piston are used. In a short period of time, overhaul is required, and the fitting size of the piston and the inner wall of the barrel is corrected, and the use cost is greatly increased. Finally, the piston needs to be sealed to the inner wall of the barrel, and the injection speed is slow. The piston can only be pushed in the barrel at a low speed, otherwise the inner wall of the barrel will be scratched. The feeding mode of the volume of the quantitative injection (extrusion) mechanism of the embodiment is backward, which ensures that there is no material dead angle and can effectively prevent carbonization of the material. Secondly, there is no friction between the piston rod and the cavity wall, and no sealing is needed. On the one hand, the processing precision of the cavity wall is reduced, on the other hand, the wear of the cavity wall is eliminated, the service life of the barrel is prolonged, and the service life can be eliminated. Frequent overhauls reduce maintenance costs and increase production efficiency. Finally, this embodiment also ensures that the cavity wall is not worn when the injection speed is increased. Embodiment 3

Refer to Figures 1 and 2:

The difference between this embodiment and the second embodiment is that the pressure control device in the cavity of the hopper barrel 7 is increased, and the rest is the same as in the second embodiment.

The hopper barrel 7 is further provided with a pressure detecting device 20 for detecting the pressure in the cavity and a pressure control device. The pressure control device receives the signal of the pressure detecting device 20 and adjusts the cylinder 19 in the quantitative pressing mechanism according to the signal. pressurized. The pressure detecting device 20 can select a pressure sensor.

When the set pressure value in the stocker cylinder 7 is compared with the pressure measured by the pressure detecting device 20 (pressure sensor) in the central controller 23, the central controller 23 is responsible for controlling the servo valve 21 and the servo pressure valve 22 The direction of the port A, B and the pressure thereof cause the piston rod pressed by the cylinder 19 to axially expand and contract to increase or decrease the pressure in the storage barrel 7 so that the pressure in the hopper 7 is stabilized at a set value. Inside.

By controlling the pressure in the hopper 7 , the stability and uniformity of the bubbles in the bubble-containing plastic melt can be further maintained, so that the bubble density of the product is uniform and stable. Embodiment 4

Refer to Figures 1 and 2:

The difference between this embodiment and the third embodiment is that the stirring device for the injection barrel 14 is increased. The remaining embodiment 3 are the same.

The front end of the injection barrel 14 is connected to the nozzle 12 by a stirring device 13. The agitating device 13 may be an impeller type or other commonly used fluid channel agitating device.

Even if the material of the hopper barrel is uniformly mixed and enters the injection barrel under a stable pressure, the bubbles may still expand or combine with each other to reduce the bubbles because the injection barrel is not immediately injected during storage or storage. The uniformity of the product reduces the quality of the product during injection molding. Therefore, the front end of the barrel must be equipped with a stirring device to spray the gas containing plastic. The gas-containing plastic is thoroughly stirred by the stirring device to enhance the mixing effect and enhance the bubble. The uniformity of the plastic ensures the quality of the molding, and then enters the mold after being ejected by the nozzle. The content described in the embodiments of the present specification is merely an enumeration of the realization forms of the inventive concept, and the scope of protection of the present invention should not be regarded as only The scope of the present invention is also limited by the embodiments of the present invention.

Claims

Claim

1. The foamed plastic injection molding method of the present invention comprises the following steps:

2. Introducing the previously mixed foamed plastic melt into another hopper barrel;

3. The plastic melted into the barrel of the plastic suitable for one shot;

4. Pressurizing the injection barrel and injection molding;

5. Measure the current injection volume of the injection barrel, the current extrusion volume of the storage barrel, and the current output speed of the loading barrel;

2. The method of injection molding of a foamed plastic according to claim 1, wherein: in step 3, the plastic which is suitable for one shot is melted and hydraulically injected out of the barrel, and the pressure in the chamber of the stocker is pressurized. Control and compensation to keep the pressure in the chamber of the hopper is stable.

3. The special equipment foam plastic injection molding apparatus for a foamed plastic injection molding method according to claim 1, comprising a feeding barrel for injecting plastic and gas to form a bubble-containing plastic melt, and connecting the feeding barrel There are gas transmission devices, hoppers, heating devices, feeding The inner cavity of the barrel is equipped with a screw, and the screw is connected with the rotary driving mechanism; the characteristic is that: the front end of the inner cavity of the feeding machine communicates with the inner cavity of the storage machine barrel, the quantitative storage mechanism of the storage machine barrel, and the measurement of the extrusion quantity The front end of the cavity of the hopper barrel communicates with the inner cavity of the barrel through a check valve, and the injection barrel is further equipped with a quantitative injection mechanism and an injection quantity measuring mechanism, and the front end of the injection barrel is equipped with a nozzle; The injection amount measuring mechanism of the injection barrel, the extrusion amount measuring mechanism of the stocker cylinder, the servo motor of the screw of the feeding barrel, the central controller of the air inlet mechanism of the gas conveying device, the central controller Comparing the secondary injection amount of the injection barrel and the current extrusion amount of the storage barrel, and outputting the adjustment command signal to the quantitative extrusion mechanism of the storage barrel to make the lower portion of the storage barrel under the condition that the two are not equal The secondary extrusion amount is equal to the current injection amount of the injection barrel; and an adjustment command signal is sent to the servo motor of the screw on the loading cylinder and the air intake mechanism of the gas transmission device to control the joining speed of the plastic while adjusting the intake speed. In addition rate with the plastic, in order to ensure uniformity of the gas in the plastics, the output speed of the feeder cylinder and the next cylinder stocker extrusion with appropriate amounts

4. The foamed plastic injection molding apparatus according to claim 3, wherein: the quantitative pressing mechanism of the hopper barrel has the following structure: a first annular bearing seat is disposed in the cavity of the hopper barrel The first piston rod is slidably mounted in the first bearing seat, and the first piston rod is in sealing engagement with the first bearing seat. The first piston rod has a gap with the cavity wall, and the material inlet of the cavity abuts the The first support base; the rear part of the first piston rod cooperates with the oil cylinder and the cylinder trigger switch.

5. The foamed plastic injection molding apparatus according to claim 3, wherein: the quantitative injection mechanism of the injection barrel has the following structure: an injection capacity of the injection barrel a second annular bearing seat is mounted in the cavity, the second piston rod is slidably mounted in the second bearing seat, the second piston rod is in sealing engagement with the second bearing seat, and a gap is formed between the second piston rod and the wall of the injection cavity. The material inlet of the injection cavity abuts the second support seat; the rear part of the second piston rod cooperates with the jacking cylinder and the jacking cylinder trigger switch.

6. The foamed plastic injection molding apparatus according to claim 4, wherein: the quantitative injection mechanism of the injection machine barrel has the following structure: a second annular support seat is disposed in the injection cavity of the injection machine barrel, a second piston rod is slidably mounted in the second bearing seat, the second piston rod is in sealing engagement with the second bearing seat, and a gap is formed between the second piston rod and the wall of the injection cavity, and the material inlet of the injection cavity abuts The second support seat; the rear portion of the second piston rod cooperates with the jacking cylinder and the jacking cylinder trigger switch.

The foamed plastic injection molding apparatus according to any one of claims 3 to 6, wherein: said hopper barrel is further provided with a pressure detecting means for detecting the pressure in the cavity and a receiving pressure detecting means. The signal and the pressure control device that adjusts the cylinder pressure in the quantitative extrusion mechanism according to the signal.

The foamed plastic injection molding apparatus according to claim 7, wherein the front end of the injection barrel is connected to the nozzle by a stirring device.

9. The foamed plastic injection molding apparatus according to claim 8, wherein: the injection amount measuring mechanism of the injection barrel and the extrusion amount measuring mechanism of the hopper barrel are a potential ruler or an optical scale.

The foamed plastic injection molding apparatus according to claim 9, wherein the quantitative injection mechanism of the injection barrel has the same size as the volume and the piston rod of the quantitative extrusion mechanism of the hopper barrel.