JP2008044152A - Plastication device of injection molding machine and plastication method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide the plastication device of an injection molding machine in which the total length of a screw is shortened to shorten an injection machine and which can perform good plastication by increasing a shearing heat value and a plastication method for the injection molding machine. <P>SOLUTION: The plastication device 10 of the injection molding machine is arranged in the heating cylinder 12 of the injection machine 11 and has the screw 20 composed of a feed zone 26, a compression zone 27, and a metering zone 28 which are arranged in turn from the rear side in the cylinder direction. The ratio L/D of the total length L of the screw 20 to the outer diameter D of the screw 20 is 8-14, and the depth H of grooves in the metering zone 28 is 0.02D+0.5 to 0.02D+0.9. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a plasticizing apparatus and a plasticizing method for an injection molding machine.

  Generally, when plasticizing a resin material and injection molding, a screw constituted by each part of a feed zone, a compression zone, and a metering zone is arranged in the heating cylinder of the injection device in order from the rear side in the cylinder direction. An injection molding machine equipped with a plasticizing device is used. The injection molding machine is configured to knead the resin material with the screw, to generate heat by shearing and to melt the resin material, and to promote the melting of the resin material with a band heater disposed in a heating cylinder.

  In such a plasticizing apparatus for an injection molding machine, kneading with a screw and heating with a band heater greatly affect the plasticization of a resin material. Therefore, conventionally, in order to achieve good plasticization of the resin material, the length of the entire length of the screw is increased (the ratio of the total length of the screw to the outer diameter of the screw is increased) to heat the resin material for a long time. It was. However, the conventional injection molding machine requires a long installation space because the injection device is long, and in addition, a large number of band heaters must be arranged in the heating cylinder, which increases power consumption during heating. It was a problem.

In order to solve the above problem, for example, a plasticizing device for an injection molding machine is known in which the ratio of the total length of the screw to the outer diameter of the screw is reduced (see, for example, Patent Document 1). In the plasticizing device of this injection molding machine, the entire length of the screw is shortened without extremely increasing the outer diameter of the screw to shorten the injection device, and the thread length of the screw is increased to increase the screw pitch ( By reducing the (groove length) (increasing the number of pitches), the resin material is configured to stay in the heating cylinder for a long time. Thereby, the heating time of a resin material becomes long and plasticization of the said resin material is accelerated | stimulated. However, in this plasticizing apparatus, the amount of shear heat generation may be insufficient in some cases, and it has been difficult to perform good plasticization.
2005-119277

  The present invention has been made in view of the above points, and in a plasticizing apparatus in which the entire length of the screw is shortened to shorten the injection apparatus, it is possible to perform good plasticization by increasing the amount of heat generated by shearing. The present invention provides a plasticizing apparatus and a plasticizing method for an injection molding machine.

  That is, the invention of claim 1 is a plasticization of an injection molding machine having a screw which is arranged in a heating cylinder of an injection apparatus and which is constituted by each part of a feed zone, a compression zone and a metering zone in order from the rear side in the cylinder direction. In the apparatus, the ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8 to 14, and the groove depth (H) in the metering zone is 0.02D + 0.5. The present invention relates to a plasticizing device for an injection molding machine, characterized in that the value is -0.02D + 0.9.

  In the invention of claim 2, the ratio of the length of the metering zone to the total length of the screw is 10 to 20%, and the ratio of the pitch (P) of the screw to the outer diameter (D) of the screw (P / D ) Is 0.3 to 0.9. The plasticizing apparatus for an injection molding machine according to claim 1.

  The invention of claim 3 is a method of plasticizing an injection molding machine having a screw which is arranged in a heating cylinder of an injection device and which is constituted by each part of a feed zone, a compression zone and a metering zone in order from the rear side in the cylinder direction. The ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8 to 14, and the groove depth (H) in the metering zone is 0.02D + 0.5. ˜0.02D + 0.9, and the relationship between the groove depth (H) in the metering zone and the screw rotation speed (n) during measurement is 200 ≦ (nπD) / (60H) ≦ 650 The present invention relates to a plasticizing method for an injection molding machine characterized in that weighing is performed at a rotational speed.

  According to the plasticizing device for an injection molding machine according to the first aspect of the present invention, the plasticizing device is disposed in the heating cylinder of the injection device, and is configured by the feed zone, the compression zone, and the metering zone in order from the rear side in the cylindrical direction. In the plasticizing device for an injection molding machine having a screw, the ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8 to 14, and the groove depth in the metering zone Since (H) is 0.02D + 0.5 to 0.02D + 0.9, the injection device can be shortened and at the same time the shear heating value can be increased, and good plasticization can be carried out and heating can be performed. It is possible to effectively reduce power consumption at the time.

  According to a second aspect of the present invention, in the first aspect, the ratio of the length of the metering zone to the total length of the screw is 10 to 20%, and the pitch of the screw (P) with respect to the outer diameter (D) of the screw ) Ratio (P / D) is 0.3 to 0.9, the resin material can be plasticized more effectively.

  According to the method for plasticizing an injection molding machine according to the invention of claim 3, the injection molding machine is disposed in the heating cylinder of the injection device, and is configured by the feed zone, the compression zone, and the metering zone in order from the rear side in the cylinder direction. A method for plasticizing an injection molding machine having a screw, wherein the ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8 to 14, and the groove in the metering zone The depth (H) is 0.02D + 0.5 to 0.02D + 0.9, and the relationship between the groove depth (H) in the metering zone and the screw rotation speed (n) during measurement is 200 ≦ (nπD) / Since the measurement is performed at the screw rotation speed such that (60H) ≦ 650, the resin material can be plasticized effectively using the above-described plasticizing apparatus.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
1 is a cross-sectional view of a plasticizing apparatus for an injection molding machine according to an embodiment of the present invention, FIG. 2 is a side view of a screw, FIG. 3 is a cross-sectional view of a screw groove, and FIG. 4 is a screw outer diameter and a metal ring. It is a graph showing the relationship with the groove depth of a zone.

  A plasticizing apparatus 10 for an injection molding machine according to an embodiment of the present invention shown in FIG. 1 has a screw 20 disposed in a heating cylinder 12 of an injection apparatus 11, and performs injection molding. The resin material supplied from the hopper (not shown) into the heating cylinder 12 of the plasticizing apparatus 10 is applied with a back pressure by an injection motor or an injection cylinder (not shown) while the screw 20 is rotated by a metering motor (not shown). Plasticize. When plasticization is completed, the molten resin stored in front of the heating cylinder 12 is injected into a cavity of a mold (not shown) that is clamped by a mold clamping device (not shown) by the injection motor or the injection cylinder. Configured to do. In this embodiment, polyacetal (POM) is used as the resin material, but a crystalline resin such as polyethylene or polypropylene, or an amorphous resin such as polystyrene or acrylonitrile butadiene styrene (ABS) may be used. In the figure, reference numeral 13 is a nozzle screwed to the tip of the heating cylinder 12, 14 is a band heater arranged on the heating cylinder 12 to promote melting of the resin material, and 15 is a resin material to which a hopper (not shown) is connected. Supply port.

  As shown in FIGS. 1 to 3, the screw 20 has a shaft portion 21 that gradually decreases in diameter from the front side to the rear side in the cylindrical direction, and a predetermined spiral shape is formed on the outer peripheral surface of the shaft portion 21. Grooves 23 are formed by threads 22 standing at a pitch (groove length) P. Further, the boundary between the thread 22 and the groove portion 23 is an R surface 24, which prevents the molten resin from staying. In this screw 20, the outer diameter D corresponds to the diameter of the thread 22 formed slightly smaller than the inner diameter of the heating cylinder 12, as shown in FIGS. 2 and 3, and the total length L is as shown in FIG. This corresponds to the linear distance of the shaft portion 21 on which the thread 22 is erected.

  The screw 20 is composed of a feed zone 26, a compression zone 27, and a metering zone 28 in order from the rear side in the cylindrical direction.

  The feed zone 26 is formed on the rear side of the screw 20 and is configured to preheat a resin material supplied from a hopper (not shown) and transport it to the front side. The length F of the feed zone 26 is 45 to 70% with respect to the total length L of the screw 20. Further, in the feed zone 26, since the shaft portion 21 is formed to be the narrowest in the entire screw 20, the groove portion 23a of the feed zone 26 is configured as a deep groove.

  The compression zone 27 is formed on the front side of the feed zone 26 and is configured to compress and heat the resin material preliminarily heated and conveyed in the feed zone 26. The length C of the compression zone 27 is 20 to 35% with respect to the total length L of the screw 20. Further, in the compression zone 27, since the shaft portion 21 is formed so as to gradually increase from the rear side to the front side of the compression zone 27, the groove portion 23b of the compression zone 27 is gradually shallower toward the front side. It is configured to be a groove.

  As shown in FIGS. 1 to 3, the metering zone 28 is formed on the front side of the screw 20, and is configured to cause the resin material melted and conveyed in the compression zone 27 to generate heat to be pushed out to the front of the screw 20. Is done. The length M of the metering zone 28 is 10 to 20% with respect to the total length L of the screw 20 and preferably includes at least two pitches P. Further, in the metering zone 28, since the shaft portion 21 is the thickest and the same thickness in the entire screw 20, the groove portion 23c of the metalling zone 28 is formed as a shallow groove. In FIG. 3, the symbol H represents the groove depth in the metering zone 28 and corresponds to the height of the thread 22 protruding from the groove 23c. Reference numeral 30 denotes a screw head that is screwed to the tip of the screw 20 and includes a backflow prevention valve (not shown) at the base. The screw head 30 and the backflow prevention valve are not included in the total length L of the screw 20.

  In the screw 20, the pitch P in the feed zone 26, the compression zone 27, and the metering zone 28 is fixed. Further, in this screw 20, the groove depth is formed so as to become deep grooves in the feed zone 26, in the compression zone 27 gradually becomes shallow grooves from the deep groove, and in the metering zone 28, so that the resin material is conveyed. When compressed, it is compressed as it is sent to the front side. The compression ratio of the screw 20 can be obtained by (length of one pitch of the feed zone × groove depth of the feed zone) / (length of one pitch of the metal ring zone × groove depth of the metal ring zone). 1.9 to 3.0.

  In the plasticizing device 10 for an injection molding machine of the present invention, the ratio L / D of the total length L of the screw 20 to the outer diameter D of the screw 20 is 8 to 14, and the groove depth H in the metering zone 28 is Is configured to be 0.02D + 0.5 to 0.02D + 0.9 (mm).

  The ratio L / D between the outer diameter D of the screw 20 and the total length L of the screw 20 has been regarded as important as an index of the ability in plasticizing the screw. In general, the total length L of the screw 20 is long and L The larger the value of / D, the better the plasticization. At this time, 20 to 22 is adopted as the value of L / D. However, by making L / D as relatively small as 8 to 14, more preferably 9.5 to 12 as described above, the total length of the screw 20 is achieved. The injection device 11 can be shortened by shortening L. When the injection device 11 is shortened in this way, the heating cylinder 11 is also shortened and heating is usually insufficient, but the groove depth H of the metering zone 28 is set to 0.02D + 0.5 to 0.02D + 0. .. 9 (mm) shallow grooves can increase the amount of heat generated by shearing to promote melting of the resin material, and can perform sufficient heating. In this plasticizing apparatus 10, when L / D is less than 8, it is difficult to secure a sufficient length for the compression zone 27 and the metering zone 28, and when L / D is greater than 14, The injection device 11 cannot be shortened sufficiently.

  In the screw 20, the overall length of the groove portion 23 formed by the thread 22 standing in a spiral shape affects the heating time of the resin material in the heating cylinder 12, and generally the outer diameter D with respect to the screw 20. The ratio P / D of the pitch P of the screw 20 is set to 0.9-1. However, when the screw 20 is configured to be shortened as described above, the pitch P of the screw 20 is reduced to ensure the entire length of the groove portion 23 and the resin material is configured to stay in the heating cylinder 12 for a long time. It is preferable. At this time, if the pitch P is too small, solidification at the time of cooling of the resin material is likely to occur when the screw 20 is stopped (at the time of adjustment or the like), so P / D is 0.3 to 0.9. More preferably, it is 0.5 to 0.7.

  Further, as a plasticizing method using the plasticizing apparatus 10 configured as described above, the shear rate by the screw 20 is 200 to 650 (mm / sec), more preferably 280 to 558 (mm / sec). A method of measuring at a screw rotation speed n (rpm) at the time of measurement may be mentioned. For example, as described in JP-A-10-180823, the shear rate is calculated from the relationship between the groove depth H (mm) of the metering zone 28 and the screw rotation speed n (rpm) during measurement ( nπD) / (60H). In this embodiment, the screw rotation speed n (rpm) is 200 to 400 (rpm), more preferably 300 to 400 (rpm). In this plasticization method, when the shear rate is 200 (mm / sec) or less, there are problems that it takes too much time to plasticize the resin material, unplasticization occurs, and the like, and 650 (mm / sec) or more. In the case of, there is a problem that resin burning occurs.

  Next, specific examples of visual evaluation of melting and degassing of the resin material will be described for the plasticizing apparatus 10 of the present invention. In the following examples, polyacetal (POM) was used as the resin material. Also, the metering stroke is 140 (mm), the injection time including the pressure holding time is 7 (mm / s), the molding cycle time is 45 (s), the cooling time is 35 (s), and the heating cylinder temperature is 200 (° C. ).

  In the plasticizing apparatus of Example 1, a screw having an L / D of 10, a screw outer diameter D of 40 mm, and a metal ring zone groove depth H of 1.5 mm was used. In the plasticizing apparatus of Example 2, a screw having an L / D of 10, a screw outer diameter D of 40 mm, and a groove depth H of the metering zone of 2.8 mm was used. In the plasticizing apparatus of Example 3, a screw having an L / D of 13, a screw outer diameter D of 40 mm, and a metal ring zone groove depth H of 2.8 mm was used. In the plasticizing apparatus of Example 4, a screw having an L / D of 22, a screw outer diameter D of 40 mm, and a metering zone groove depth H of 2.8 mm was used.

  Regarding each of the above Examples 1 to 4, each screw rotation speed 200 (when the measured values of the back pressure of the resin material are 7.1 (MPa), 14.2 (MPa), and 28.4 (MPa), respectively. rpm), 300 (rpm), and 400 (rpm), the presence or absence of an unmelted portion of the resin material was visually evaluated, and the measurement time was measured. In addition, since the molding cycle time was 45 (s), the standard of the measurement time was set to 35 (s), which is equal to the cooling time, from the relationship of injection, holding pressure, mold opening / closing, and the like.

  In the plasticizing apparatus of Example 1, the resin material could be melted in any case, and the metering time was within 35 seconds, so that the plasticization could be carried out satisfactorily. In the plasticizing apparatuses of Examples 2 to 4, good plasticization could not be performed because an unmelted portion was present in the resin material in any case regardless of the measurement time.

  As can be understood from the results shown in Table 1, the screw 20 capable of performing good plasticization in the plasticizing apparatus 10 has an L / D of 10, a screw outer diameter D of 40 mm, a metering zone. The groove depth H is 1.5 mm.

  In the screw 20 capable of performing the above-described good plasticization, the pitch P is set to 24 mm, and the groove depth H (1.5 mm) of the metering zone 28 is about 6.3% with respect to the pitch P. is there. The ratio of the groove depth H of the metalling zone 28 to the pitch P of the screw 20 is preferably about 5.4 to 7.1%. When the screw outer diameter D is 40 mm, the groove depth of the metalling zone 28 is A preferable value of H is 1.3 to 1.7 mm which is a range of ± 0.2 of the optimum value (1.5 mm). A more preferable value is 1.4 to 1.6 mm which is a range of ± 0.1. When the ratio of the groove depth H of the metal ring zone 28 to the pitch P of the screw 20 is smaller than 5.4%, the shear heat generation becomes excessive, and the molten resin must be reduced unless the screw rotational speed is reduced so as to affect the molding cycle. There is a possibility that the thermal deterioration of the resin proceeds, and there is a problem that the amount of the molten resin delivered decreases due to insufficient force for conveying the molten resin forward. If it is larger than 7.1%, the groove depth H is too deep even if the screw rotation speed is increased, so that a sufficient amount of heat generated by shearing cannot be obtained. There is a problem that the heat of the band heater 14 is not sufficiently transferred to the resin, and the molten resin becomes unplasticized.

  Further, the groove depth H of the metering zone 28 of the screw 20 has an optimum value changed according to the screw outer diameter D and the type of resin material to be plasticized, and further compared with the thickness of the pellet to be molded. When the depth H is extremely shallow, problems such as slow biting and excessive generation of shearing heat occur, so it is preferable to make the depth deeper than ½ of the thickness of the pellet.

Here, when changing the screw outer diameter D on the basis of the screw 20 (the outer diameter D is 40 mm and the groove depth H of the metering zone 28 is 1.5 mm), Hirota Hamada: “Extruder to be used in the field” "Manual" (issued on May 20, 1993) Page 32 to Page 33, hm / H = (d / D) By using the calculation formula of ^0.7 , meta corresponding to the appropriate screw outer diameter The groove depth of the ring zone 28 can be estimated. In this equation, d is the screw outer diameter at the time of change, and hm is the groove depth of the metering zone 28 at the time of change.

  From these facts, experience shows that when the screw outer diameter D is 20 mm, 0.9 to 1.3 mm, when the screw outer diameter D is 60 mm, 1.7 to 2.1 mm, and when the screw outer diameter D is 120 mm Is 2.9 to 3.3 mm, which is preferably the groove depth H of the metering zone 28. Moreover, since the outer diameter of a general screw is 20-120 mm and it is used suitably also in the said screw 20 within this range, as shown in FIG. 4, the value of the screw outer diameter D is 20-120. Thus, the inside of the shaded portion A where the groove depth H of the metalling zone 28 is 0.02D + 0.5 to 0.02D + 0.9 is the optimum condition of the screw 20. In addition, when the screw outer diameter D is smaller than 20 mm, it is inappropriate from the relationship with the outer diameter of a normal pellet, and when it is larger than 120 mm, the groove depth due to the scale-up becomes deeper than a certain level and is inappropriate.

  As can be understood from the above description, in the plasticizing apparatus 10 for an injection molding machine of the present invention, L / D is set to 8 to 14, and the groove depth H in the metering zone 28 is set to 0. .02D + 0.5 to 0.02D + 0.9 makes it possible to shorten the injection device 11 and simultaneously increase the amount of heat generated by shearing. Therefore, heating is insufficient when the injection device 11 is shortened. Therefore, it becomes possible to carry out good plasticization. Further, by shortening the injection device 11, it is possible to reduce the power consumption during heating by reducing the band heater 14 disposed in the heating cylinder 12, and further, by increasing the shear heating value as described above, Since the operating time of the band heater 14 can be reduced, the power consumption can be more effectively reduced.

  Further, the ratio of the length M of the metal ring zone 28 to the total length L of the screw 20 is set to 10 to 20%, and P / D is set to 0.3 to 0.9, whereby heating in the metal ring zone 28 is performed. Sufficient time can be secured and the resin material can be plasticized more effectively.

  In addition, this invention includes what can be implemented in the aspect which added various change, correction, improvement, etc. based on the knowledge of those skilled in the art. Further, it goes without saying that any of the embodiments to which the above-mentioned changes are added is included in the scope of the present invention without departing from the gist of the present invention.

It is principal part sectional drawing of the plasticizing apparatus of the injection molding machine which concerns on one Example of this invention. It is a side view of a screw. It is sectional drawing of the groove part periphery of a screw. It is a graph showing the relationship between the screw outer diameter and the groove depth of the metering zone.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Plasticizer of injection molding machine 11 Injection apparatus 12 Heating cylinder 14 Band heater 20 Screw 26 Feed zone 27 Compression zone 28 Metalling zone C Length of compression zone D Outer diameter of screw F Feed zone length H Metalling zone Groove depth L Total length of screw M Metering zone length P Screw pitch

Claims (3)

In a plasticizing device for an injection molding machine, which is arranged in a heating cylinder of an injection device and has a screw constituted by each part of a feed zone, a compression zone and a metering zone in order from the rear side in the cylinder direction,
The ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8-14, and the groove depth (H) in the metering zone is 0.02D + 0.5-0. An injection molding machine plasticizing device characterized by being 02D + 0.9.   The ratio of the length of the metering zone to the total length of the screw is 10 to 20%, and the ratio (P / D) of the pitch (P) of the screw to the outer diameter (D) of the screw is 0.3 to 0. The plasticizing device for an injection molding machine according to claim 1, which is .9. A plasticizing method for an injection molding machine, which is arranged in a heating cylinder of an injection device and has a screw constituted by each part of a feed zone, a compression zone and a metering zone in order from the rear side in the cylinder direction,
The ratio (L / D) of the total length (L) of the screw to the outer diameter (D) of the screw is 8 to 14, and the groove depth (H) in the metering zone is 0.02D + 0.5 to 0. 02D + 0.9
The measurement is performed at the screw rotation speed such that the relationship between the groove depth (H) in the metering zone and the screw rotation speed (n) during measurement is 200 ≦ (nπD) / (60H) ≦ 650. A method for plasticizing an injection molding machine.

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