Injection molding apparatus and method for reducing the increase in velocity of the flow front during injection molding

Abstract

The present disclosure relates to an injection molding device (1) comprising at least a first mold plate comprising a first injection inlet (3) arranged in fluid connection with a first gate (4) to a cavity (2) and a second injection inlet (5) arranged in fluid connection with a second gate (6) to the cavity (2). The first and second injection inlets (3, 5) are arranged to be opened in sequence. The second gate (6) comprises a first gate volume (11) to the cavity (2). The second gate (6) is further provided with a second gate volume (12) to allow injection material to flow into the second gate volume (12) at the same time as into the first gate volume (11) and thereafter into the cavity (2). The present disclosure also relates to a method for reducing the velocity increase of a flow front (10) during injection molding.

Description

Technical Field

[0001] This disclosure relates to injection molding apparatus and methods for reducing the velocity increase of the flow front during injection molding. Background Technology

[0002] Injection molding is a well-known plastic molding technology used to mold plastic parts of many shapes and sizes. When injection molding large parts, modern injection molding equipment uses several inlets that open sequentially, and the injection of liquid plastic usually begins in the middle of the part.

[0003] When the second inlet opens during the filling stage, the flow front of the injected liquid plastic associated with the second inlet experiences a velocity increase. This velocity increase is undesirable because it affects the final quality of the injection-molded part. Excessive velocity variations at the flow front will result in visible surface deformation on the part after painting.

[0004] One way to solve this problem is to use a step-by-step entry point (see link https: / / www.synventive.com / products / active-gate-control.aspx). However, these entry points are both expensive and require a significant amount of time to install.

[0005] Therefore, there is a need to improve previously known methods for addressing the increase in flow front velocity during injection molding. Summary of the Invention

[0006] One object of this disclosure is to provide an injection molding apparatus and method capable of solving the aforementioned problems. This object is achieved by the injection molding apparatus of claim 1 and the method of claim 8. The dependent claims provide advantageous exemplary embodiments.

[0007] This disclosure relates to an injection molding apparatus including at least a first template. The first template includes a first injection inlet and a second injection inlet, the first injection inlet being arranged in fluid connection with a first gate leading into a cavity, and the second injection inlet being arranged in fluid connection with a second gate leading into the cavity. The first and second injection inlets are arranged to open sequentially, with the first injection inlet opening before the second injection inlet. The second gate includes a first gate volume leading into the cavity. The second gate also has a second gate volume to allow injection material to flow into the second gate volume simultaneously with the first gate volume and subsequently into the cavity, thereby reducing the velocity of the injection flow from the second gate in the cavity.

[0008] By adding a second gate volume to the second gate in addition to the existing first gate volume that flows into the mold cavity, the increased volume can be used as a damper (buffer) for the injected liquid plastic. The increase in velocity at the flow front of the injected material from the second gate is reduced, and in some cases even reduced to zero.

[0009] Although the injection molding apparatus according to this disclosure is most advantageous during the filling stage, improvements have been shown to be provided also during the holding stage.

[0010] Another advantage of the injection molding apparatus according to this disclosure is that the second gate volume can be increased on existing injection molding apparatuses. Even though this increases the cost compared to adding the second gate volume during the design phase of the injection molding apparatus, the cost will still be significantly lower than the cost of using a progressively opening gate.

[0011] The second gate volume can be provided by a first increased volume extending from the second injection inlet along the first direction. The second gate volume can take various forms, and in the least complex form, it extends along the first direction, for example, in a direction away from the direction into the cavity from the second gate.

[0012] A second gate volume can also be provided by extending a second volume from the second injection inlet along a second direction different from the first direction. If increasing the second gate volume by extending only in the first direction cannot produce a sufficiently large second gate volume to meet the needs, the second gate volume can extend along a second direction different from the first direction. The second direction can be perpendicular to the first direction and extend in a direction that is horizontal or vertical relative to the extension of the first direction. Optionally, the second direction can extend along a direction that forms an angle of less than or greater than 90° with the first direction. The second gate volume can also extend along positive and negative second directions; an example could be that the second gate volume is substantially T-shaped.

[0013] The first and / or second additional volume can take the form of one or more shapes, such as a cuboid, ellipsoid, parallelepiped, or cylinder. Depending on the available space in the first mold, the first and / or second additional volume can adopt different shapes to achieve the desired second gate volume. Various combinations of shapes can be used to achieve the desired second gate volume.

[0014] The second gate includes a throttling valve that leads to the first increased volume. The throttling valve reduces the flow rate of liquid plastic into the second gate volume, preventing it from being filled too quickly. If the second gate volume is filled too quickly, its effectiveness is reduced.

[0015] The throttle valve may have a cross-sectional area between approximately 1 / 4 and 3 / 4 of the cross-sectional area of ​​the second gate volume, wherein the throttle valve connects the first and second gate volumes. This cross-sectional area has been shown to provide the desired filling rate of the second gate volume. It is also desirable that the material in the throttle valve hardens once the second gate volume is filled, so that the second gate volume is not completely filled during the filling phase.

[0016] The size of the second gate volume is a function of the distance between the first and second injection inlets. Depending on the size and shape of the part to be molded, the injection inlets must be arranged at different distances between them (the first and second injection inlets) to achieve the desired filling and holding pressure characteristics. When designing an injection molding apparatus including a second gate volume according to this disclosure, the distance between the first and second injection inlets will determine the size, i.e., the final volume of the second gate volume.

[0017] This disclosure also relates to a method for reducing the velocity increase of the flow front during injection molding, wherein the injection molding apparatus includes at least a first template, the first template including a first injection inlet and a second injection inlet, the first injection inlet being arranged in fluid connection with a first gate leading into a cavity, and the second injection inlet being arranged in fluid connection with a second gate leading into a cavity, wherein the first and second injection inlets are arranged to open sequentially, and the first injection inlet opens before the second injection inlet, wherein the second gate includes a first gate volume leading into a cavity, wherein the method includes:

[0018] - Provide a second gate volume for the second gate to allow the injected material to flow into the second gate volume at the same time as it flows into the first gate volume, and then into the cavity, thereby reducing the velocity of the injection flow from the second gate in the cavity.

[0019] The method may also include:

[0020] - A second gate volume is provided by providing a first increased volume extending from the second injection inlet along the first direction.

[0021] The method may also include:

[0022] -A second gate volume is also provided by providing a second increased volume extending from the second injection inlet in a second direction different from the first direction.

[0023] The method may also include:

[0024] - Provide a first increased volume and / or a second increased volume having one or more shapes of cuboid, ellipsoid, parallelepiped, or cylinder.

[0025] The method may also include:

[0026] - Provide a throttling valve for the second gate to allow the first increased volume to flow in.

[0027] The advantages of this method are the same as those of the injection molding apparatus described above. Attached Figure Description

[0028] Figure 1 The diagram schematically illustrates a prior art injection molding apparatus during cavity filling.

[0029] Figure 2 An injection molding apparatus according to this disclosure is schematically shown during cavity filling.

[0030] Figures 3a to 3c A close-up view schematically illustrating the volume of the second gate according to an embodiment of the present disclosure is shown.

[0031] Figures 4a to 4b The diagram schematically illustrates the gates of various injection molding devices during cavity filling, and

[0032] Figures 5a to 5b Schematic illustration of having according to Figure 1 A comparison between existing injection molding apparatuses with gates and injection molding apparatuses with gates according to this disclosure. Detailed Implementation

[0033] Figure 1 A prior art injection molding apparatus 1 is schematically shown during the filling of cavity 2. Injection molding apparatus 1 includes a first template and a second template (not shown). The first template includes a first injection inlet 3 and a second injection inlet 5, the first injection inlet 3 being arranged in fluid connection with a first gate 4 leading into cavity 2, and the second injection inlet 5 being arranged in fluid connection with a second gate 6 leading into cavity 2. The first injection inlet 3 and the second injection inlet 5 are arranged to open sequentially, with the first injection inlet 3 opening before the second injection inlet 5.

[0034] exist Figure 1 In this design, cavity 2 has an exemplary shape corresponding to a simplified vehicle bumper. The width of the bumper is approximately 1000 mm. The injection molding apparatus 1 also includes a third injection inlet 7, which is arranged in fluid connection with a third gate 8 leading into cavity 2. The third injection inlet 7 is arranged to open sequentially after the first inlet 3 and the second inlet 5.

[0035] The first injection inlet 3, the second injection inlet 5, and the third injection inlet 7 are provided with liquid plastic through a flow channel 8, which in turn is supplied from a nozzle 9, as previously known in the art.

[0036] In the diagram, the first injection inlet 3 has been open for some time and the second injection inlet 5 has just finished opening. The flow front 10 is... Figure 1 Clearly visible in the image. The first velocity v1, measured at the wall of cavity 2, and the second velocity v2, measured at a certain distance from the wall of cavity 2, represent the flow front velocity of the injected liquid plastic and show the local velocity difference that may cause surface defects or flow marks on the product.

[0037] exist Figure 1 In the equation, v1 is approximately equal to 57.1 cm / s, and v2 is approximately equal to 45.8 cm / s.

[0038] Figure 2 An injection molding apparatus 1 according to this disclosure is schematically shown during the filling of cavity 2. Figure 2 In, with Figure 1 The difference in the injection molding apparatus 1 is that the second gate 6 includes a first gate volume 11 that flows into the cavity 2, and the second gate 6 also has a second gate volume 12 to allow the injection material to flow into the second gate volume 12 simultaneously with the first gate volume 11, and then into the cavity 2. This reduces the velocity of the injection flow from the second gate 6 in the cavity 2.

[0039] exist Figure 2 In the middle, the first injection port 3 and the second injection port 5 are connected to... Figure 1 Open in the same order and for the same duration. For example... Figure 1 As shown, the first velocity v1 measured at the wall of cavity 2 and the second velocity v2 measured at a certain distance from the wall of cavity 2 represent the flow front velocity of the injected liquid plastic.

[0040] exist Figure 2 In the figure, v1 is approximately 23.3 cm / s, and v2 is approximately 21.7 cm / s. This clearly shows that the second gate volume 12 reduces the velocity of the liquid plastic injection flow from the second gate 6 into the cavity 2, as well as the local velocity difference. The lower velocity at the flow front 10 reduces the injection molding product's (e.g., according to...) Figure 1 and 2 The example bumper) poses the following risks: obtaining a surface that does not meet the desired visual appearance of the product or a surface that is deformed due to liquid plastic entering the cavity 2 at an excessively high speed.

[0041] The final volume of the second gate is a function of the distance between the first injection inlet 3 and the second injection inlet 5. If the first and second injection inlets 3 and 5 are not located in the same plane, the distance is measured as the radius of an ellipsoid, where the first injection inlet 3 is located at the center of the ellipsoid and the second injection inlet 5 is located on the surface of the ellipsoid.

[0042] Figures 3a to 3c A close-up view of the second gate volume 12 according to an embodiment of the present disclosure is shown schematically. Figure 3a In, it is shown as follows Figure 2 The second gate 6 shown includes a throttle valve 13 and a second gate volume 12. The second gate volume 12 is provided by a first increased volume 14 extending primarily from the second injection inlet 5 in a first direction, wherein the first direction extends substantially in the same direction as the extension direction of the second gate 6.

[0043] exist Figure 3b In the process, a second gate volume 12 is provided by a first increased volume 14, which mainly extends from the second injection inlet 5 along a first direction, wherein the first direction is perpendicular to the extension of the second gate 6.

[0044] exist Figure 3c In the process, a second gate volume 12 is provided by a first increased volume 14 extending along a first direction and a second direction, wherein the first direction extends substantially in the same direction as the extension of the second gate 6, and wherein the second direction is perpendicular to the extension of the second gate 6.

[0045] In addition to the first increased gate volume, a second increased gate volume 12 can also be provided by a second increased volume, the second increased volume extending from the second injection inlet 5 in a second direction different from the first direction. For example, combined with Figure 3a and 3b The shape of the first additional volume 14 can produce a second gate volume 12 with a T-shape. Depending on the amount of space in the first injection mold or other suitable location, the shape of the second gate volume 12 can be one or more of a cuboid, ellipsoid, parallelepiped, or cylinder.

[0046] Figures 3a to 3c The throttle valve 13 reduces the flow rate of liquid plastic into the second gate volume 12, preventing it from being filled too quickly. If the second gate volume 12 is filled too quickly, its effectiveness decreases.

[0047] The throttle valve 13 may have a cross-sectional area between approximately 25% and 75% of the cross-sectional area of ​​the second gate volume 12, wherein the throttle valve 13 connects the first gate volume 11 and the second gate volume 12. The cross-sectional area of ​​this size is shown to provide the desired filling rate of the second gate volume 12. It is also desirable that the material in the throttle valve 13 hardens once the second gate volume 12 is filled, so that the second gate volume is not completely filled during the filling phase.

[0048] exist Figures 3a to 3bIn this embodiment, the first gate volume 11 and the second gate volume 12 are substantially cuboid in shape and have a height of approximately 3 mm. The throttle valve 13 has a height of approximately 1 mm and is formed at the junction of the throttle valve 13 and the first gate volume 11, comprising 33% of the cross-sectional area of ​​the second gate volume 12. The effect of the throttle valve 13 is improved if its width is not wider than the width of the first gate volume 11. The interface between the second gate 6 and the cavity 2 remains unchanged.

[0049] An example of the height of the throttle valve is between approximately 0.5 mm and 2 mm. The throttle valve also has an extension in the same direction as the first gate volume 11. An example of the range of the extension of the throttle valve is between approximately 2 mm and 5 mm. Figure 3a The example length of the second gate volume is between 50mm and 70mm, of which a length of approximately 60mm is a good starting point for finding the appropriate design length.

[0050] In terms of design and manufacturing, the throttle valve is placed as close as possible to the second injection inlet.

[0051] Figures 4a to 4b The diagram schematically illustrates the filling process during cavity 2. Figure 1 and 2 A more detailed view of the flow rate of the injection molding apparatus 1.

[0052] Figure 4a schematically shown Figure 1 A more detailed view of the flow velocity of the injection molding apparatus 1. The velocities are indicated at three locations within the cavity 2: a first velocity v1 at the flow front 10 near the second gate 6, where the highest velocity is found; a second velocity v2 at a first distance from the flow front 10; and a third velocity v3 at a second distance from the flow front 10. Figure 4a In the equation, the first velocity v1 is approximately 47.3 m / s, the second velocity v2 is approximately 22.4 m / s, and the third velocity v3 is approximately 13.2 m / s.

[0053] Figure 4b schematically shown Figure 2 A more detailed view of the flow rate of the injection molding apparatus 1, which includes a second gate 6 with a second gate volume 12. Velocities are measured at three locations within the cavity 2: a first velocity v1 is measured near the flow front edge of the second gate 6; a second velocity v2 is measured at a first distance from the flow front edge 10; and a third velocity v3 is measured at a second distance from the flow front edge 10. Figure 4aIn the figure, the first velocity v1 is approximately 23.0 m / s, the second velocity v2 is approximately 21.1 m / s, and the third velocity v3 is approximately 13.1 m / s. This clearly demonstrates that the second gate volume 12 provides the desired effect of reducing the flow front velocity without compromising injection quality.

[0054] Figure 5a and 5b It schematically shows the following based on Figure 1 A comparison is made between an injection molding apparatus 1 with a prior art second gate 6 and an injection molding apparatus 1 with a second gate 6 according to the present disclosure. This comparison involves the pressure at the nozzle 9 required to achieve the desired (target) filling time.

[0055] Figure 5a The diagram shows a second gate 6 for existing technology (e.g.) Figure 1 The pressure at nozzle 9 of the gate (in the case of a gate). For this type of gate, a large pressure drop is usually interpreted as a change in the flow front velocity, which is something that people try to avoid.

[0056] Figure 5b The diagram shows the second gate 6 according to the invention (e.g. Figure 2 The pressure at nozzle 9 of the gate (in the process). For this type of gate, a large pressure drop does not necessarily indicate, for example... Figure 2 and 4b The flow front velocity is shown to be changing in this way.

[0057] The final volume of the second gate also depends on the dimensions of the product to be injection molded. Simulation software can be advantageously used to find the optimal second gate volume. In this case, the dimensions mentioned above will provide good starting values ​​for the simulation. The dimensions of the runner, such as the cross-sectional area or volume, can also be optimized to increase the effect of the second gate volume.

[0058] Although the present disclosure has been detailed and described in the accompanying drawings and the foregoing description, such description and illustration should be considered illustrative or exemplary, and the present disclosure is not limited to the exemplary embodiments disclosed.

Claims

1. An injection molding apparatus (1), the injection molding apparatus (1) comprising at least a first template, the first template comprising a first injection inlet (3) and a second injection inlet (5), the first injection inlet (3) being arranged in fluid connection with a first gate (4) leading into a cavity (2), and the second injection inlet (5) being arranged in fluid connection with a second gate (6) leading into the cavity (2), wherein, The first injection inlet (3) and the second injection inlet (5) are arranged to open sequentially, with the first injection inlet (3) opening before the second injection inlet (5), wherein the second gate (6) includes a first gate volume (11) leading into the cavity (2), characterized in that the second gate (6) is further provided with a second gate volume (12) to allow the injected material to flow into the second gate volume (12) while flowing into the first gate volume (11), and then into the cavity (2), thereby reducing the velocity of the injection flow from the second gate (6) in the cavity (2), wherein the second gate volume (12) is provided by a first increasing volume (14) extending from the second injection inlet (5) in a first direction, and the second gate (6) includes a throttle valve (13) leading into the first increasing volume (14).

2. The injection molding apparatus (1) according to claim 1, wherein, The second gate volume (12) is also provided by a second additional volume extending from the second injection inlet (5) in a second direction different from the first direction.

3. The injection molding apparatus (1) according to claim 2, wherein, The first increased volume and / or the second increased volume are in one or more of the following shapes: cuboid, ellipsoid, parallelepiped, cylinder.

4. The injection molding apparatus (1) according to claim 1, wherein, The throttle valve (13) has a cross-sectional area between about 1 / 4 and 3 / 4 of the cross-sectional area of ​​the second gate volume (12), wherein the throttle valve (13) connects the first gate volume (11) and the second gate volume (12).

5. The injection molding apparatus (1) according to any one of the preceding claims, wherein, The size of the second gate volume (12) is a function of the distance between the first injection inlet (3) and the second injection inlet (5).

6. A method for reducing the velocity increase of the flow front (10) during injection molding, wherein, An injection molding apparatus (1) includes at least a first template, the first template including a first injection inlet (3) and a second injection inlet (5), the first injection inlet (3) being arranged in fluid connection with a first gate (4) leading into a mold cavity (2), the second injection inlet (5) being arranged in fluid connection with a second gate (6) leading into the mold cavity (2), wherein the first injection inlet (3) and the second injection inlet (5) are arranged to open sequentially, and the first injection inlet (3) opens before the second injection inlet (5), wherein the second gate (6) includes a first gate volume (11) leading into the mold cavity (2), wherein the method includes: - A second gate volume (12) is provided for the second gate (6) to allow the injected material to flow into the second gate volume (12) at the same time as it flows into the first gate volume (11), and then into the cavity (2), thereby reducing the velocity of the injection flow from the second gate (6) in the cavity (2). - By providing a first increased volume (14) extending from the second injection inlet (5) along a first direction, the second gate volume (12) is provided, and - Provide a throttle valve (13) for the second gate (6) to allow access to the first increased volume (14).

7. The method according to claim 6, wherein, The method includes: - The second gate volume (12) is also provided by providing a second increased volume extending from the second injection inlet (5) in a second direction different from the first direction.

8. The method according to claim 7, wherein, The method includes: - Provide the first increased volume and / or the second increased volume having one or more shapes of cuboid, ellipsoid, parallelepiped, and cylinder.

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