JP2016175210A - Injection molding device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an injection molding device which, even when a thin molded article is injection molded, can prevent the occurrence of sinking and thinning while suppressing an overload on an injection device.SOLUTION: Since the ratio of the diameter φt of an injection port 21t to the inner diameter φb of a body part 21b of a nozzle 21 is in a range of 3:10 to 3:20, the pressure loss in the nozzle 21 due to a decrease in a cross section area can be reduced. Since a clearance Ga between a check ring 24 and a cylinder 22 is 50 μm or more and 100 μm or less, the pressure loss due to a back flow is reduced. Consequently, the filling performance of a resin is improved to enable filling of the resin into a cavity CA corresponding to a thin lens LP. At this time, the filling can be performed without excessively increasing the temperature of the resin and the temperature of molds 41, 42, so that molding can be performed without destroying the physical properties of the resin. In addition, the filling can be performed without excessively increasing the filling speed of a molten resin, so that loads applied to a servomotor and a screw 23 of an injection device 16, and the like can be reduced.SELECTED DRAWING: Figure 2

Description

  The present invention relates to an injection molding apparatus for molding optical parts and other molded articles, and more particularly to an injection molding apparatus including an in-line type screw.

  In an injection molding apparatus, since the stagnation and leakage of molten resin can be reduced and uniform kneading is possible, an injection apparatus incorporating an in-line screw type injection metering mechanism is widely used.

  In recent years, with the increasing demand for miniaturization of optical components and other products, miniaturization and thinning of molded products by injection molding are progressing. The thinner the molded product, the more difficult it is to inject molten resin. When the filling capacity of the injection device is low, defects such as sink marks and thinning of the molded product due to insufficient filling occur. As a solution to these, there are methods such as increasing the resin temperature and mold temperature to increase the fluidity of the molten resin, increasing the injection speed setting and increasing the flow speed, but the resin temperature setting range is defined by the resin properties Also, since the injection speed is related to the pressure control on the injection device side, there is a limit to its adjustment.

  Even when the resin temperature is within the allowable range, if the temperature of the molten resin is raised to lower the viscosity, there is a problem that backflow at the time of resin injection increases and escape and variation of the filling pressure increase. For this reason, it is generally known to reduce the pressure escape and variation of the filling by adjusting the check ring and suppressing the back flow of the molten resin.

  However, in the case of a very thin molded product, the relief of the filling pressure can be reduced by reducing the clearance between the check ring and the cylinder and suppressing the backflow. The problem that the load to a screw also increases will arise. If the load on the servo or screw is too high, the sensor may stop when it detects a pressure peak, or it may lead to a failure depending on the condition. In particular, when the switching from the filling process to the pressure holding process is controlled by the pressure setting, there is a possibility that if the pressure peak as described above is detected, the molding cannot be performed as set.

  Although it is for extrusion molding rather than injection molding, a technique is known that reduces the resistance received when the molten resin passes through the nozzle by adjusting the nozzle inner diameter so that the injection capability does not decrease (Patent Document). 1).

  However, when a very thin molded product is injection-molded, it cannot be handled only by adjusting the nozzle inner diameter as described above. Especially when the clearance between the check ring and the cylinder is reduced to such an extent that the load on the servo does not become a problem, and the relief of the filling pressure is reduced within a range where the load on the servo and the screw does not become too large, the shape of the nozzle tip Depending on the case, an overload is applied to the joint between the nozzle and the cylinder, and the nozzle may come off.

JP 2008-188772 A

  The present invention has been made in view of the above-mentioned problems of the background art, and even when a thin molded product is injection-molded, it prevents occurrence of sink marks and thinning while suppressing an overload to the injection device. An object of the present invention is to provide an injection molding apparatus that can be used.

  In order to achieve the above object, an injection molding apparatus according to the present invention includes a cylinder having a nozzle fixed to the tip, a screw housed in the cylinder, and a check ring attached to a head portion of the screw. The ratio of the diameter of the injection port formed at the tip of the nozzle and the inner diameter of the body of the nozzle is in the range from 3:10 to 3:20, and the check ring and cylinder The gap amount is 50 μm or more and 100 μm or less.

  In the above injection molding apparatus, the ratio between the diameter of the injection port and the inner diameter of the nozzle body is in the range from 3:10 to 3:20. Since the pressure loss due to the reduction of the cross-sectional area can be reduced and the gap amount between the check ring and the cylinder is 50 μm or more and 100 μm or less, the pressure loss due to the backflow is reduced particularly on the upper limit side of the gap amount. As a result, the filling performance of the resin is improved, and the cavity corresponding to the thin product can be filled. At this time, the filling can be performed without excessively raising the temperature of the resin and the temperature of the mold, so that the molding can be performed without destroying the physical properties of the resin. In addition, it is possible to prevent the occurrence of resin burning (yellowing) or black dust due to the temperature rise of the resin. Further, since the filling can be performed without excessively increasing the filling speed of the molten resin, it is possible to reduce the load applied to the connection portion between the nozzle and the cylinder in addition to the load applied to the servo and screw of the injection apparatus.

  In a specific aspect of the present invention, in the injection molding apparatus, the ratio of the inner diameter of the body of the nozzle to the inner diameter of the cylinder is in the range of 1: 1 to 1: 5. In this case, the pressure loss due to the reduction of the cross-sectional area in the nozzle can be more reliably reduced.

  In another aspect of the invention, the inner diameter of the cylinder is 25 mm or less. In this case, the cylinder corresponds to a relatively small molded product.

  In still another aspect of the present invention, resin is filled into a mold space corresponding to a thin molded product having a thickness of the thinnest portion of 0.2 mm or less. In this case, in general, it becomes difficult to fill the cavity, and sink marks and thinning of the molded product due to insufficient filling tend to occur, but as described above, the diameter of the injection port and the inner diameter of the body of the nozzle Since the ratio and the gap amount between the check ring and the cylinder are appropriately set, it is possible to prevent the occurrence of sink marks and thinning in the molded product without destroying the physical properties of the resin and without increasing the load on the injection device.

It is a conceptual diagram explaining the shaping | molding apparatus for implementing the injection molding apparatus which concerns on 1st Embodiment. It is sectional drawing to which a part of shaping | molding apparatus of FIG. 1 was expanded. It is sectional drawing which shows an example of the molded article formed with the shaping | molding apparatus of FIG.

  Hereinafter, an injection molding apparatus according to an embodiment of the present invention will be specifically described with reference to the drawings.

  With reference to FIG. 1, the shaping | molding apparatus for implementing the injection molding apparatus which concerns on embodiment is demonstrated. The molding apparatus 100 includes an injection molding machine 10 that is a main body part that performs injection molding to produce a molded product MP, and a control device 30 that comprehensively controls the operation of each part of the molding apparatus 100.

  The injection molding machine 10 is a horizontal molding machine and includes a molding die 40, a fixed platen 11, a movable platen 12, an opening / closing drive device 15, and an injection device 16. The injection molding machine 10 is also provided with a mold temperature controller 47 and the like. The injection molding machine 10 clamps both molds 41 and 42 by sandwiching a first mold 41 and a second mold 42 constituting the molding mold 40 between the fixed platen 11 and the movable platen 12. This enables molding.

  The fixed platen 11 fixed on the support frame 14 detachably supports the first mold 41. The fixed platen 11 is formed with an opening 11b through which a nozzle 21 described later is passed.

  The movable platen 12 is supported by the linear guide 15a so as to be movable back and forth with respect to the fixed platen 11. The movable platen 12 detachably supports the second mold 42. Note that an ejector driving unit 45 is assembled to the movable platen 12.

  The opening / closing drive device 15 is supported by the mold clamping plate 13 and includes a linear guide 15a, a power transmission unit 15d, and an actuator 15e. The power transmission unit 15 d expands and contracts by receiving a driving force from an actuator 15 e that operates under the control of the control device 30. Thereby, the fixed platen 11 and the movable platen 12 can be brought close to or away from each other, and the first mold 41 and the second mold 42 can be clamped or opened.

  The injection device 16 is an inline screw type device and includes a feed unit 16a, a raw material storage unit 16b, a drive unit 16c, and the like. The injection device 16 operates at an appropriate timing under the control of the control device 30 and is a molten resin in which the temperature and the filling pressure are controlled from the resin injection nozzle 21 provided at the tip of the feed portion 16a. Can be injected at a desired timing. At this time, the drive unit 16c is provided with a screw 23 (see FIG. 2) inserted into the feed unit 16a by a servo mechanism (not shown) incorporated in the drive unit 16c so as to enable kneading, metering, injection and the like of the resin. Can be rotated or advanced at a required speed.

  A mold temperature controller 47 provided along with the injection molding machine 10 circulates a temperature-controlled heat medium in both molds 41 and 42. Thereby, the temperature of both metal mold | dies 41 and 42 can be kept at an appropriate temperature at the time of shaping | molding.

  The control device 30 includes an opening / closing control unit 31, an injection device control unit 32, and an ejector control unit 33. The opening / closing control unit 31 enables the molds 41 and 42 to be closed, clamped, opened, and the like by operating the actuator 15e. The injection device control unit 32 causes the molten resin to be injected at a desired pressure into the cavity formed between the molds 41 and 42 by appropriately operating the feed unit 16a, the drive unit 16c, and the like. The ejector control unit 33 operates the ejector driving unit 45 to push out the molded product MP remaining in the second mold 42 when the mold is opened from the second mold 42 to release the mold.

  The molding die 40 will be described with reference to FIG. The first die 41 on the fixed side of the molding die 40 is formed with a sprue bush or nozzle touch part 41d having a hollow shape corresponding to the tip of the nozzle 21 on the back side fixed to the stationary platen 11 shown in FIG. Has been. A sprue 41e is formed from the nozzle touch part 41d toward the surface side facing the second mold 42. On the other hand, the movable second mold 42 can be reciprocated in the AB direction by the mechanism shown in FIG. The second mold 42 is moved toward the first mold 41 on the fixed side, the molds 41 and 42 are matched with the mold matching surfaces PS1 and PS2, and the mold is clamped to mold the optical element. A cavity CV for this purpose and a runner RU communicating with this via a gate are formed. The runner RU and the sprue 41e constitute a flow path space FC for supplying molten resin to the cavity CV.

A cavity CV that is a space between the first mold 41 and the second mold 42 corresponds to the shape of the optical element that is a molded product.
As shown in FIG. 3, a lens LP, which is a partial molded product cut out from the molded product MP as a whole in FIG. 1, is made of plastic and has a central portion LPa as an optical functional portion having an optical function. And an annular flat flange portion LPb extending in the outer diameter direction from the center portion LPa. The lens LP is, for example, an objective lens that is incorporated in an optical pickup device, an element lens that constitutes an imaging lens incorporated in a mobile phone, a smartphone, or the like. A thin portion PLc is formed between the center portion LPa and the flange portion LPb. In the thin portion PLc, the thinnest portion where the thickness in the direction of the optical axis OA is the smallest has a thickness Th of 0.2 mm or less.

  As shown in FIG. 2, in the injection device 16, the feed unit 16 a includes a nozzle 21 fixed to the tip, a cylinder 22 that supports the base side of the nozzle 21, a screw 23 housed in the cylinder 22, and a screw And a check ring 24 attached to the head portion 23a. The nozzle 21 has a cylindrical shape, has a flow path 21a therein, and has a thin injection port 21t at the tip 21b. The flow path 21 a is wide at the root side and is connected to the internal space 22 a of the cylinder 22. The cylinder 22 has a uniform cross section and houses the screw 23 in the internal space 22a. A nozzle 21 is screwed to the tip of the cylinder 22. Around the cylinder 22, a heater 25 with a temperature sensor is disposed, and the temperature of the molten resin accumulated in the internal space 22a is maintained in a desired state based on the output of a temperature sensor (not shown). The screw 23 is a rod-shaped member, and a spiral or thread-like convex portion 23b is formed on the outer peripheral side surface. By rotating the screw 23 while applying back pressure, the resin can be fed to the tip side. By advancing the screw 23 toward the nozzle 21, the molten resin can be injected at a desired speed from the injection port 21t. Thereafter, the pressure holding is performed by maintaining the state in which the forward pressure is applied to the screw 23. The check ring 24 is a cylindrical member that extends rearward from the rear end of the head portion 23a. The detailed description of the check ring 24 is omitted, but when the screw 23 rotates in the forward direction so as to feed the molten resin to the tip, a flow path is secured between the screw 23 and the molten resin. When the screw 23 rotates in the reverse direction, the flow path between the screw 23 and the screw 23 is blocked to prevent the molten resin from flowing backward.

  Hereinafter, the dimension of the resin flow path in the feed part 16a will be described. First, the inner diameter φc of the cylinder 22 is 25 mm or less. In the cylinder 22, the gap Ga between the outer surface 24 p of the check ring 24 and the inner surface 22 p of the cylinder 22 is 50 μm or more and 100 μm or less. The inner diameter φb of the body 21b of the nozzle 21 is not particularly limited, but the ratio between the diameter φt of the injection port 21t formed at the tip of the nozzle 21 and the inner diameter φb of the body 21b of the nozzle 21 is 3:10. To 3:20, that is, φt / φb is in the range of 0.3 to 0.15. Furthermore, the ratio of the inner diameter φb of the body 21b of the nozzle 21 to the inner diameter φc of the cylinder 22 is in the range from 1: 1 to 1: 5, that is, φb / φc is in the range of 1 to 0.2. .

  In the injection molding apparatus of the present embodiment, the ratio of the diameter φt of the injection port 21t and the inner diameter φb of the body 21b of the nozzle 21 is in the range of 3:10 to 3:20 (particularly 3:20 or 0.15). Therefore, the pressure loss due to the reduction of the cross-sectional area in the nozzle 21 can be reduced, and the gap amount Ga between the check ring 24 and the cylinder 22 is 50 μm or more and 100 μm or less (particularly 100 μm or less). The pressure loss due to is reduced. As a result, the resin filling performance is improved, and the cavity CV corresponding to the thin lens LP can also be filled. At this time, the filling can be performed without excessively raising the temperature of the resin and the temperatures of the molds 41 and 42, so that molding can be performed without destroying the physical properties of the resin. Further, since the filling can be performed without excessively increasing the filling speed of the molten resin, the load applied to the servo mechanism of the injection device 16 and the screw 23 and the load applied to the connecting portion between the nozzle 21 and the tip of the cylinder 22 can be reduced. . By setting the ratio of the diameter φt and the inner diameter φb to 3:10 or 0.3 or less, sufficient resin can be accumulated in the nozzle 21, and by setting the gap amount Ga to 50 μm or more, a check is made. It becomes easy to ensure the operation of the ring 24.

以上の表１において、記号「◎」は、問題なく充填可能であることを意味し、記号「×」は、ヒケ、未充填等があって充填不可能であることを意味する。なお、成形結果が◎ということは、樹脂が有するエネルギーが成形機内部で滞留していないということであり、サーボ、スクリュー、並びに、ノズルとシリンダーとの接続部に掛る負荷が少ないと言える。以上の表１から明らかなように、広い樹脂温度及び充填時間の範囲内で成形可能であることがわかる。 Specific examples will be described below. First, the ratio of the diameter φt of the injection port 21t at the tip of the nozzle 21 to the inner diameter φb of the body 21b of the nozzle 21 is set to 0.3 (that is, 1.5: 5), and the clearance between the cylinder and the check ring is 50 μm. The experiment was conducted by changing the resin temperature and filling speed. The material used as the resin was a cyclic olefin copolymer (specifically, APEL (trademark) manufactured by Mitsui Chemicals), and the thickness of the thinnest part of the lens as a molded product was 0.11 mm. In the experiment, the holding pressure was 7.4 × 10 ⁷ N / m ² for 1 second, then 6.4 × 10 ⁷ N / m ² for 3 seconds, and finally 0.98 × 10 ⁷ N / m. m ² for 2 seconds. The mold temperature around the cavity CV was 130 ° C. The cooling time after filling with the molten resin was 10 seconds, the resin drying temperature and the resin drying time were 90 ° C. and 12 hours, and the cylinder temperature (that is, the resin temperature) was 250 to 280 ° C. The results of the first experimental example are summarized in Table 1 below.
[Table 1]

In Table 1 above, the symbol “◎” means that filling is possible without any problem, and the symbol “x” means that there is a sink, unfilling, etc., and filling is impossible. In addition, the molding result “◎” means that the energy of the resin does not stay in the molding machine, and it can be said that the load applied to the connection portion between the servo, the screw, and the nozzle and the cylinder is small. As apparent from Table 1 above, it can be seen that molding is possible within a wide range of resin temperature and filling time.

以上の表２から明らかなように、樹脂温度３１０℃及び充填時間０．０６秒のピンポイント領域で成形可能であった。 Next, as a second experimental example, the ratio of the diameter φt of the injection port 21t at the tip of the nozzle 21 to the inner diameter φb of the body 21b of the nozzle 21 is set to 0.15 (that is, 1.5: 10), and the cylinder The gap between the check ring and the check ring was set to 100 μm, and the experiment was performed by changing the resin temperature and the filling speed. The material used as the resin was APEL, and the thickness of the thinnest part of the lens as a molded product was 0.11 mm. In the experiment of the second experimental example, the holding pressure, the cooling time, the resin drying temperature and time, the cylinder temperature, and the like were the same as in the first experimental example. The results of the second experimental example are summarized in Table 2 below.
[Table 2]

As is apparent from Table 2 above, molding was possible in a pinpoint region with a resin temperature of 310 ° C. and a filling time of 0.06 seconds.

以上の表３において、記号「◎」は、問題なく充填可能であることを意味し、記号「×」は、ヒケ、未充填等があって充填不可能であることを意味する。記号「○」は、ヒケが発生しないが、厚み０．１１ｍｍ程度の最薄部を有する成形品では０．００１〜０．００２ｍｍ程度の減肉が発生するため、記号「◎」より充填性能が劣る領域であることを意味する。ただし、光学的には問題がない。記号「△」は、充填は可能であるが圧力損失が大きくヒケが発生する。 A combination of the diameter of the injection port 21t (injection port diameter) φt and the inner diameter (nozzle inner diameter) φb of the body 21b of the nozzle 21 is appropriately set, and the dimension between the check ring 24 and the gap amount Ga between the cylinder 22 is changed. Conducted experiments. The diameter φt was changed in the range of 1.5 mm to 3.0 mm, the inner diameter φb was changed in the range of 2.5 mm to 10 mm, and the gap amount Ga was changed in the range of 25 to 100 μm. Other conditions were the same as in the case of the first experimental example. The results are summarized in Table 3 below.
[Table 3]

In Table 3 above, the symbol “◎” means that filling is possible without any problem, and the symbol “x” means that there is sink, unfilling, etc., and filling is impossible. The symbol “◯” does not cause sink marks, but the molded product having the thinnest portion having a thickness of about 0.11 mm causes a thinning of about 0.001 to 0.002 mm. It means an inferior area. However, there is no optical problem. The symbol “Δ” can be filled, but the pressure loss is large and sinking occurs.

以上の表４において、記号「◎」、「○」、「△」、「×」等の意味は、表３の場合と同様である。 An experiment was also conducted in which the inner diameter (nozzle inner diameter) φb of the body 21b of the nozzle 21 and the gap amount Ga between the check ring 24 and the cylinder 22 were appropriately set, and the size of the inner diameter φc of the cylinder 22 was changed. The inner diameter φb was changed in the range of 5 mm to 10 mm, the gap amount Ga was changed in the range of 25 to 100 μm, and the inner diameter φc was changed in the range of 10 mm to 50 mm. Other conditions were the same as those in the first experimental example or Table 3. The results are summarized in Table 4 below.
[Table 4]

In Table 4 above, the meanings of symbols “◎”, “◯”, “Δ”, “x”, and the like are the same as those in Table 3.

  Although the present invention has been described based on the above embodiments, the present invention is not limited to the above embodiments, and various modifications are possible. For example, in the above embodiment, the injection molding machine 10 is a horizontal type, but can be a vertical type molding machine in which the first mold 41 and the second mold 42 are arranged vertically.

  Moreover, in the said embodiment, although the shape of the molding surface (namely, cavity CV) of the 1st metal mold | die 41 and the 2nd metal mold | die 42 shall correspond to the shape illustrated in FIG. 3, the shape and magnitude | size of a molding surface Can be appropriately changed depending on the application.

DESCRIPTION OF SYMBOLS 10 ... Injection molding machine, 11 ... Fixed board, 12 ... Movable board, 15 ... Opening / closing drive device, 16 ... Injection device, 16a ... Feed part, 16b ... Raw material storage part, 16c ... Drive part, 21 ... Nozzle, 21b ... Tip 21t ... injection port, 21a ... flow path, 21b ... body, 21t ... injection port, 22 ... cylinder, 22a ... internal space, 22p ... inner diameter surface, 23 ... screw, 23b ... convex part, 23a ... head part, 24 ... Check ring, 24p ... Outer surface, 25 ... Heater, 30 ... Control device, 31 ... Opening / closing control unit, 32 ... Injection device control unit, 40 ... Mold, 41, 42 ... Mold, 41d ... Nozzle touch , 47 ... Mold temperature controller, 100 ... Molding device, CV ... Cavity, FC ... Channel space, LP ... Lens, LPa ... Center part, LPb ... Flange part, P ... moldings, PLc ... the thin portion, PS1, PS2 ... die matching surface

Claims (4)

An injection molding apparatus comprising an injection device having a cylinder having a nozzle fixed to a tip, a screw housed in the cylinder, and a check ring attached to a head portion of the screw,
The ratio of the diameter of the injection port formed at the tip of the nozzle and the inner diameter of the body of the nozzle is in the range from 3:10 to 3:20;
An injection molding apparatus, wherein a gap between the check ring and the cylinder is 50 μm or more and 100 μm or less.   2. The injection molding apparatus according to claim 1, wherein the ratio of the inner diameter of the body of the nozzle to the inner diameter of the cylinder is in the range of 1: 1 to 1: 5.   The injection molding apparatus according to any one of claims 1 and 2, wherein an inner diameter of the cylinder is 25 mm or less.   The injection molding apparatus according to any one of claims 1 to 3, wherein a resin is filled into a mold space corresponding to a thin molded product having a thickness of 0.2 mm or less at the thinnest part.

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