JP2016052737A - Injection molding machine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the fraction defective of a molded article by removing unfavorable gas generated when melting a resin material in a heating cylinder.SOLUTION: A heating cylinder 3 is provided with a resin material supply device 6 for supplying a resin material. The resin material supply device 6 comprises: a material dropping cylinder 23 that, when a feed hopper 11 to which the resin material is supplied and the heating cylinder 3 communicating with the feed hopper 11 are in a vacuum state, supplies the resin material, having been supplied to the feed hopper 11, into the heating cylinder 3 installed with a screw 5; a cylindrical sleeve 15 that covers an outer periphery of the material dropping cylinder 23 with a space therebetween; and an exhaust port 19 that discharges unfavorable gas, generated by melting the resin material in the heating cylinder 3, through an exhaust passage 25 between the cylindrical sleeve 15 and the material dropping cylinder 23. A clearance dimension between a lower end of the material dropping cylinder 23 and an upper end of the screw 5 is 1 mm or more and 3 mm or less.SELECTED DRAWING: Figure 1

Description

  The present invention provides an injection molding machine that forms a molded body by supplying a resin material that can be a raw material of a molded body into a heating cylinder, and then injecting and filling the resin material heated and melted in the heating cylinder into a cavity of a mold. In particular, an injection molding machine capable of reducing a defective rate of a manufactured molded body by degassing a defective gas contained in the resin material from a resin material supplied into a heating cylinder About.

  In a general injection molding machine that has been used in the past, a granular thermoplastic resin (pellet) as a raw material is fed into a heating cylinder, and the resin is melted by a reciprocating screw provided in the heating cylinder. Sending to the nozzle side of the screw tip, injecting molten resin into the mold cavity from the injection nozzle provided on the screw tip side, cooling the molten resin in the cavity and solidifying it, then opening the mold, protruding pin The molded body is molded by removing the molded product attached to the mold from the mold.

  In an injection molding machine for molding such a molded body such as plastic, when the thermoplastic resin thrown into the hopper is heated and melted in a heating cylinder, water vapor and volatilization contained in the thermoplastic resin are accompanied accordingly. Gas or the like is generated as a defective gas. For this reason, it is known that when defective gas is supplied to the cavity together with the thermoplastic resin, the molded product manufactured due to the defective gas is burned, and defective products are generated.

  Those related to the above technique are disclosed in Patent Documents 1 and 2. Patent Document 1 has the following description of a melt molding machine 1 such as an injection molding machine or an extrusion molding machine. A cylindrical supply cylinder port 15 is provided at the lower end of the supply hopper 10 for charging the resin into the cylinder 4. A connecting pipe 11 connected in close contact with the lower portion of the supply hopper 10 is provided. The lower end portion of the connection pipe 11 is connected in close contact with the inner peripheral surface of the receiving port 7 of the cylinder 4. The connecting pipe 11 is provided as a double cylinder structure so as to cover the outer periphery of the supply cylinder port 15 at a predetermined interval. It is described that, with such a configuration, the resin is stably supplied from the supply tube port portion 15 and the defective gas is removed from between the connection tube 11 and the supply tube port portion 15.

  In addition, Patent Document 2 discloses a resin raw material supply device for a synthetic resin molding machine for the purpose of removing gas generated in a casing of a heating cylinder during a weighing process by using a rinsing effect by the atmosphere or the like. It is disclosed. In order to achieve the object, the synthetic resin molding machine resin raw material supply device is connected to the raw material inlet of the heating cylinder composed of a screw and a casing and the raw material inlet, and supplies the raw material to the heating cylinder. The raw material charging inner cylinder part to be charged, the damper provided above the raw material charging inner cylinder part, and the raw material charging inner cylinder part, which is opened between the raw material charging inner cylinder part and the damper, An atmosphere introduction port that communicates with the atmosphere introduction valve, an atmosphere release valve connected to the atmosphere introduction port, and a gas suction port that is disposed so as to surround the raw material introduction inner cylinder portion, and a lower end opening portion that is the raw material introduction port. And an exhaust outer cylinder portion that communicates with the control unit and a control unit that controls the opening of the atmosphere release valve in response to a predetermined control signal, thereby removing defective gas generated in the casing by a so-called rinsing effect. Listed That.

JP 2003-103522 A Japanese Patent No. 4142959

  In the prior arts such as Patent Documents 1 and 2, the purpose is to remove the defective gas generated when the resin material is heated and melted in the heating cylinder. For example, all of the defective gas is removed. If a part of the defective gas is supplied to the cavity of the resin material and the co-mold, the defective rate of the manufactured molded body is increased. Therefore, there has been a demand for a technique that reduces the amount of defective gas supplied together with the resin material to the cavity of the mold as much as possible, and further reduces the defective rate of the manufactured molded body.

  The present invention has been made in view of the above problems, and in an injection molding machine in which a resin material that can be a raw material of a molded body is supplied into a heating cylinder and melted, the resin material is melted in the heating cylinder. An object of the present invention is to provide an injection molding machine capable of reducing the defect rate of a molded article to be produced by effectively removing the generated defective gas.

The invention related to this injection molding machine
A heating cylinder that melts the resin material inside, a resin material supply device that supplies the resin material to the heating cylinder, and a resin material that is attached to the tip of the heating cylinder and is melted by the heating cylinder In an injection molding machine comprising: an injection nozzle that injects into a cavity; and a screw that is provided in the heating cylinder and sends the molten resin material to the injection nozzle side,
The resin material supply device includes a pump that generates a suction force by driving, a charging hopper that is charged with a resin material by the suction force generated by driving the pump, and an openable and closable seal provided at a lower portion of the charging hopper A proximity switch for detecting whether or not the resin material supplied to the supply hopper is in a predetermined amount, a supply hopper supplied with the resin material supplied to the input hopper via the sealing valve, When the proximity switch detects that the resin material supplied to the supply hopper is in a predetermined amount, it is driven to evacuate the supply hopper and the heating cylinder communicating with the supply hopper. A vacuum pump and the inside of the supply hopper and the inside of the heating cylinder communicating with the supply hopper are evacuated by driving the vacuum pump. A material dropping cylinder that supplies the resin material supplied to the supply hopper into the heating cylinder provided with the screw, and a cylindrical sleeve that covers the outer periphery of the material dropping cylinder with a gap therebetween. An exhaust port connected to the vacuum pump for discharging defective gas generated by melting the resin material in the heating cylinder through an exhaust path between the cylindrical sleeve and the material dropping cylinder And comprising
The gap dimension between the lower end portion of the material dropping cylinder and the upper end portion of the screw is 1 mm or more and 3 mm or less.

Furthermore, the invention relating to this injection molding machine
Among the length, height, or width dimension of the resin material supplied into the heating cylinder, it is between the lower end portion of the material dropping cylinder and the upper end portion of the screw than the smallest minimum dimension. The gap size is reduced.

  According to the present invention, the gap between the lower end portion of the material dropping cylinder and the upper end portion of the screw is 1 mm or more and 3 mm or less, so that a defective gas is generated when the resin material is melted in the heating cylinder. Is evacuated from the vacuum pump, smoothly led to the exhaust path between the cylindrical sleeve and the material dropping cylinder, and smoothly discharged from the exhaust port to the outside through the exhaust path for removal (deaeration). can do. That is, the defective gas generated when the resin material is melted in the heating cylinder can be effectively discharged to the outside, thereby preventing air bubbles from being mixed in the manufactured molded body. Thus, the defective rate of the molded article to be manufactured can be reduced. Further, the gap dimension between the lower end portion of the material dropping cylinder and the upper end portion of the screw is further smaller than the smallest minimum dimension among the length, height, or width dimension of the resin material supplied into the heating cylinder. Since it has been made smaller, it can prevent the resin material from being carried into the exhaust path between the cylindrical sleeve located on the outer peripheral side of the material dropping cylinder and the material dropping cylinder. It is possible to prevent the gas flow from being hindered. Therefore, it becomes possible to discharge | emit defective gas more smoothly from an exhaust port to the exterior, and, thereby, the defect rate of the molded object manufactured can be reduced more.

It is a block diagram which shows the injection unit comprised in the injection molding machine of Example 1. It is sectional drawing which shows the principal part of the injection unit comprised in the injection molding machine of Example 1. It is explanatory drawing which shows the dimension of the resin material supplied to a heating cylinder. It is a graph of the experimental result which shows the relationship between the clearance gap between the lower end part of a material dropping cylinder and the upper end part of a screw, and the defect rate of the molded object manufactured. It is sectional drawing which shows the principal part of the injection unit comprised in the injection molding machine of Example 2.

  Embodiments of the present invention will be described below with reference to FIGS. Needless to say, the present invention can be easily applied to configurations other than those described in the embodiments without departing from the spirit of the invention.

  An injection unit 1 configured in the injection molding machine of Example 1 shown in FIG. 1 includes a cylindrical heating cylinder 3 fixed to a hopper block 2, an injection nozzle 4 attached to the tip of the heating cylinder 3, and a heating cylinder 3. A screw 5 provided rotatably inside, and a resin material supply device 6 for supplying a resin material such as a thermoplastic resin as a raw material of a molded body to be manufactured to the heating cylinder 3 are provided. In the present embodiment, as shown in FIG. 3, the average dimensions of the resin material supplied from the resin material supply device 6 to the heating cylinder 3 are a length L of 2.96 mm, a height H of 3.26 mm, The width W is 2.47 mm.

  The resin material supply device 6 includes, in order from the top to the bottom, a pipe 7 for transporting the resin material, a charging hopper 9 provided with an air suction port 8 on the side, an openable / closable sealing valve 10, a supply hopper 11, a glass tube 13 The material dropping cylinder 23 is disposed, and a pump 12 is connected to the air suction port 8 of the charging hopper 9.

  A cylindrical glass tube 13 provided below the supply hopper 11 is opposed to a cylindrical cylindrical sleeve 15 fitted to the peripheral edge of a hole 14 formed in the hopper block 2. Has been placed. The material dropping cylinder 23 provided in the lower part of the glass tube 13 is inserted through a hole 16 formed in the upper part of the heating cylinder 3. Then, the resin material charged into the charging hopper 9 from the pipe 7 is supplied from the charging hopper 9 into the heating cylinder 3 through the sealing valve 10 that can be opened and closed, the supply hopper 11, the glass tube 13, and the material dropping cylinder 23. The The glass tube 13 below the supply hopper 11 is made of glass in order to prevent adverse effects due to static electricity.

  A proximity switch 17 as a sensor is provided on the side of the glass tube 13. The proximity switch 17 detects whether or not a predetermined amount of resin material is present in the glass tube 13. By this detection, it is possible to detect whether or not a predetermined amount of the resin material is in the supply hopper 11.

  At the upper part of the hopper block 2, a flange portion 18 is provided for holding a glass tube 13 in which the supply hopper 11 is integrally provided. An exhaust port 19 communicating with the inside of the glass tube 13 is formed in the flange portion 18. Then, the vacuum pump 20 connected to the exhaust port 19 is driven in a state in which the hermetic valve 10 is closed, whereby the inside of the glass tube 13 and the supply hopper 11 communicating with the inside of the glass tube 13, the material dropping cylinder The inside of 23 becomes a vacuum state. On the other hand, when releasing the vacuum state, the atmosphere release valve 21 provided on the side of the sealing valve 10 is opened, so that the atmosphere release valve 21 can supply the inside of the supply hopper 11, the glass tube 13, and the material dropping cylinder. Air is flowed into 23.

  The material dropping cylinder 23 arranged so as to be inserted through the hole 16 of the heating cylinder 3 is provided immediately above the screw 5, and the outer periphery of the material dropping cylinder 23 is spaced apart. A cylindrical sleeve 15 is provided to form a double structure.

  A slight gap is formed between the lower end portion of the material dropping cylinder 23 and the upper end portion of the screw 5. In the present embodiment, the gap dimension C is 1 mm or more and 3 mm or less, more specifically 1 mm, and the defective gas generated by melting the resin material in the heating cylinder 3 is, The length of the resin material supplied into the heating cylinder 3 when discharged from the exhaust port 19 connected to the vacuum pump 20 to the outside of the apparatus through the exhaust path 25 between the material dropping cylinder 23 and the cylindrical sleeve 15. The gap dimension C between the lower end portion of the material dropping cylinder 23 and the upper end portion of the screw 5 is formed smaller than any of the smallest minimum dimensions among the L, height H, and width W dimensions. For this reason, it is possible to prevent the resin material from being carried into the exhaust path 25 between the cylindrical sleeve 15 and the material dropping cylinder 23.

  Here, an operation when the resin material is supplied into the heating cylinder 3 and defective gas generated by melting the resin material in the heating cylinder 3 is discharged to the outside will be described. When the vacuum pump 20 is driven in a state in which the hermetic valve 10 is closed, the proximity switch when the inside of the supply hopper 11, the inside of the glass tube 13 communicating therewith, the inside of the material dropping cylinder 23, etc. is in a vacuum state. 17 detects that the resin material is not present in the glass tube 13, the air release valve 21 is opened and the sealing valve 10 is opened based on the detection, and air is supplied from the atmosphere release valve 21 through the sealing valve 10. In addition to the charging hopper 9, it flows into the supply hopper 11, the glass tube 13 communicating therewith, the material dropping cylinder 23, and the like.

  Next, when the pump 12 is driven, as the air in the charging hopper 9 is exhausted to the outside from the air suction port 8, the resin material is externally connected to the pipe 7, the charging hopper 9, the sealing valve 10, It is conveyed into the heating cylinder 3 through the supply hopper 11, the glass tube 13, and the material dropping cylinder 23.

  When the proximity switch 17 detects that there is a predetermined amount of resin material in the glass tube 13, both the air release valve 21 and the sealing valve 10 are closed, and then the vacuum pump 20 is driven, and the inside of the supply hopper 11, The inside of the glass tube 13, the material dropping cylinder 23, and the inside of the heating cylinder 3 communicating with these are evacuated.

  Then, in the state where the inside of the supply hopper 11, the inside of the glass tube 13, the inside of the material dropping cylinder 23, and the inside of the heating cylinder 3 communicating with these are evacuated, the resin material that the material dropping port 23 has as the screw 5 rotates. However, when the resin material is sequentially put into the heating cylinder 3 that is being heated, the resin material is conveyed to the injection nozzle 4 side at the tip end side of the screw 5 according to the rotation of the screw 5 and the measuring step is performed. In parallel with the metering step, defective gas generated by melting the resin material in the heating cylinder 3 by the vacuuming action by the vacuum pump 20 is discharged from the exhaust port 19 to the outside through the exhaust path 25. Is done. Then, after the measuring step, the injection nozzle 4 injects and fills the molten resin material into the cavity of the clamped mold, thereby forming a molded body.

  Here, the relationship between the gap dimension C between the lower end portion of the material dropping cylinder 23 and the upper end portion of the screw 5 and the defective rate of the molded body to be manufactured will be described based on the graph showing the experimental results of FIG. .

  In the graph of FIG. 4, the defect rate is represented on the vertical axis, the gap dimension is represented on the horizontal axis, and the product that is visually determined to contain bubbles (so-called silver) is counted as the number of defects. The defect rate is shown as an experimental result. As can be seen from the figure, of the total number “17” when the gap size is 1 mm, the number of defects was “3” and the defect rate (%) was “18%”. Of the total number “19” when the gap size is 3 mm, the number of defects was “4” and the defect rate was “21%”. Of the total number “16” when the gap size is 5 mm, the number of defects was “6” and the defect rate was “38%”. Of the total number “18” when the gap size is 10 mm, the number of defects was “5” and the defect rate was “33.4%”. Of the total number “17” when the gap size is 40 mm, the number of defects was “5” and the defect rate was “38.5%”. From these experimental results, it was found that when the gap size is 1 mm or more and 3 mm or less, the defect rate is low, but when it exceeds this, the defect rate is greatly improved. That is, it was possible to derive a result that the defective gas was effectively removed when the defect rate of the manufactured molded body was low and the gap size was 1 mm or more and 3 mm or less.

  According to the injection molding machine of the first embodiment as described above, the clearance dimension between the lower end portion of the material dropping cylinder 23 and the upper end portion of the screw 5 is set to 1 mm or more and 3 mm or less. When the defective gas generated when the resin material is melted at this time is evacuated from the vacuum pump 20, the defective gas is smoothly guided to the exhaust path 25 between the cylindrical sleeve 15 and the material dropping cylinder 23. The exhaust passage 19 can be smoothly discharged from the exhaust port 19 to the outside of the injection molding machine and removed (degassed). That is, the defective gas generated when the resin material is melted in the heating cylinder 3 can be effectively discharged to the outside, thereby preventing air bubbles from being mixed in the manufactured molded body. Thus, it is possible to reduce the defect rate of the manufactured molded body. Furthermore, the gap dimension C between the lower end portion of the material dropping cylinder 23 and the upper end portion of the screw 5 is the length L, height H, or width W of the resin material supplied into the heating cylinder 3. By making it smaller than the smallest minimum dimension, the resin material is prevented from being carried into the exhaust path 25 between the cylindrical sleeve 15 located on the outer peripheral side of the material dropping cylinder 23 and the material dropping cylinder 23. This can prevent the flow of defective gas passing through the exhaust path 25 from being hindered. Therefore, it becomes possible to discharge | emit defective gas more smoothly from the exhaust port 19 outside, and, thereby, the defect rate of the molded object manufactured can be reduced more.

  FIG. 5 shows a main part of an injection unit configured in the injection molding machine of the second embodiment. Since it has substantially the same configuration as the injection molding machine of the first embodiment, the same parts as those of the first embodiment are denoted by the same reference numerals, detailed description thereof is omitted, and only differences are mainly described below. explain.

  In the second embodiment, as shown in FIG. 5, an inclined notch 22 is formed at the rear part of the material dropping cylinder 23 arranged so as to be inserted through the hole 16 of the heating cylinder 3. The notch 22 of the material dropping cylinder 23 will be described as the front side of the screw 5 as the front side and the opposite side as the rear side. It is formed obliquely upward. The inclination angle of the notch 22 is 40 degrees in the second embodiment, but may be appropriately selected within a range of 12.5 degrees to 45 degrees. The notch 22 is formed on the rear side of the material dropping cylinder 23, while the exhaust port 19 is provided on the front side of the material dropping cylinder 23. Therefore, the defective gas is mainly discharged through the front exhaust path 25 without being affected by the notch 22, and the same effect as that of the first embodiment can be obtained. By being provided, it is possible to make the rear part of the material dropping cylinder 23 spread, so that it is possible to smoothly supply the resin material to the heating cylinder 3.

DESCRIPTION OF SYMBOLS 1 Injection unit 2 Hopper block 3 Heating cylinder 4 Injection nozzle 5 Screw 6 Resin material supply apparatus 7 Piping 8 Air suction port 9 Feeding hopper 10 Sealing valve 11 Supply hopper 12 Pump 13 Glass tube 14 Hole 15 Cylindrical sleeve 16 Hole 17 Proximity Switch 18 Flange part 19 Exhaust port 20 Vacuum pump 21 Atmospheric release valve 22 Notch part 23 Material drop cylinder 25 Exhaust path C Clearance dimension H Height L Length W Width

Claims (2)

A heating cylinder that melts the resin material inside, a resin material supply device that supplies the resin material to the heating cylinder, and a resin material that is attached to the tip of the heating cylinder and is melted by the heating cylinder In an injection molding machine comprising: an injection nozzle that injects into a cavity; and a screw that is provided in the heating cylinder and sends the molten resin material to the injection nozzle side,
The resin material supply device includes a pump that generates a suction force by driving, a charging hopper that is charged with a resin material by the suction force generated by driving the pump, and an openable and closable seal provided at a lower portion of the charging hopper A proximity switch for detecting whether or not the resin material supplied to the supply hopper is in a predetermined amount, a supply hopper supplied with the resin material supplied to the input hopper via the sealing valve, When the proximity switch detects that the resin material supplied to the supply hopper is in a predetermined amount, it is driven to evacuate the supply hopper and the heating cylinder communicating with the supply hopper. A vacuum pump and the inside of the supply hopper and the inside of the heating cylinder communicating with the supply hopper are evacuated by driving the vacuum pump. A material dropping cylinder that supplies the resin material supplied to the supply hopper into the heating cylinder provided with the screw, and a cylindrical sleeve that covers the outer periphery of the material dropping cylinder with a gap therebetween. An exhaust port connected to the vacuum pump for discharging defective gas generated by melting the resin material in the heating cylinder through an exhaust path between the cylindrical sleeve and the material dropping cylinder And comprising
An injection molding machine characterized in that a gap dimension between a lower end portion of the material dropping cylinder and an upper end portion of the screw is set to 1 mm or more and 3 mm or less.   Among the length, height, or width dimension of the resin material supplied into the heating cylinder, it is between the lower end portion of the material dropping cylinder and the upper end portion of the screw than the smallest minimum dimension. The injection molding machine according to claim 1, wherein the gap dimension is reduced.

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