TWI711524B - Cladding type plastic injection molding method for thick lens - Google Patents

Abstract

A cladding type plastic injection molding method for thick lens is provided, which includes the following steps: conducting first injection molding, perform a first shot semi finished product which has a first main body and at least one supporting leg with melted plastic which has first melted plastic volume, the supporting leg is disposed extending out of the side of first main body; conducting second injection molding, perform a finished product by cladding the first shot semi finished product and part of the supporting leg with melted plastic which has second melted plastic volume, the sum of the first melted plastic volume and the second melted plastic volume is total melted plastic volume of the finished product, the first melted plastic volume is 17~40% of the total melted plastic volume, the finished product has a total thickness which along a first direction and is equal to or bigger than 20mm.

Description

Coated plastic injection molding method for thick lens

The present invention relates to a coating plastic injection molding method for thick lenses, in particular to a method that can effectively reduce the problems of coating bonding lines and quality defects (such as warpage, shrinkage, encapsulation, etc.) that can be A covered plastic injection molding method that shortens the molding time of thick lenses.

Nowadays, in the manufacture of plastic products, the Multi-Component Molding (MCM) process has been widely used in diversified plastic part design and manufacturing processes. The MCM process mainly uses two or more materials to be injected and injected into a mold to produce products. For example, common electric tools are coated with soft plastic in a hard plastic shell to provide sufficient structural strength and soft feel. However, the MCM process in actual production still faces many problems and challenges. For example, the MCM process may involve multiple inserts or multiple different materials, so the design and development rules of single material injection molding often cannot be directly applied to MCM. In addition, due to the complexity of the MCM process and the physical mechanism of multiple materials, the traditional empirical rule of single-material injection molding cannot effectively optimize or design changes to key molding conditions, resulting in uncertainty in quality control.

The MCM process is summarized into two categories. The first category is that when two materials are compounded and molded, a distinct distinct interface will be produced, including insert molding, over molding, and multi-shot Sequential molding (sequential multiple shot molding). The second type is that when two materials are compounded and molded, an uncertain interface will be produced. This type of common manufacturing process includes co-injection and bi-injection.

Regarding the uncertain intermediate interface system, how the product designer can correctly guess the best gate position and material ratio so that the finished product can obtain the ideal material distribution and product characteristics will be a considerable challenge for the product designer.

In addition, for large-size plastic injection of thick optical lenses (for example, a diameter greater than 60 mm (mm) and a thickness greater than 20 mm (mm)), because the heat of the molten plastic injected into the mold cavity is too concentrated, when the outer plastic Cooling makes the heat in the center difficult to conduct outward to the mold, causing the problem of excessive cooling time. When using the existing straight-through cooling water path, the water path is not easy to approach the mold cavity for cooling due to the limitation of the traditional drilling processing method, causing the problem of excessive temperature difference between the plastic and the mold or different cooling rates, resulting in shrinkage and warpage of the finished product Defects such as residual stress.

The production time of the above-mentioned thick optical lens using the straight-through cooling water circuit is extremely long, which can be as long as 600 to 900 seconds in practice. An excessively long cooling time will greatly reduce production efficiency and increase manufacturing costs.

Based on this, how can there be a "thick part" that can effectively reduce the problems of the coating and bonding line and quality defects (such as warpage, shrinkage, encapsulation, etc.) of the step-by-step molding, and greatly shorten the cooling and production time of the thick lens The encapsulated plastic injection molding method of the lens" is an urgent issue to be solved by those in the relevant technical field.

In one embodiment, the present invention proposes a thick lens encapsulated plastic injection molding method, which includes the following steps: performing the first injection molding, and forming a first injection semi-finished product with a melt having a first melt volume The first injection semi-finished product includes a first main body and at least one supporting leg, the supporting leg protruding from the side of the first main body; and the second injection molding is performed, and the molten glue with the second molten glue volume is coated on The outside of the first semi-finished product is shot and part of the supporting feet is covered to form a finished product. The sum of the first melt volume and the second melt volume is the total melt volume of the finished product, and the first melt volume accounts for the total melt volume 17~40%, the finished product has a total thickness along a first direction, and the total thickness is equal to or greater than 20 millimeters (mm).

100: Process of coating plastic injection molding method for thick lens

102, 104: Steps of the process flow of the thick lens covered plastic injection molding method

10: First shot semi-finished product

11, 11A, 11B: the first body

111: first side

112: second side

12, 12A, 121B, 122B, 123B: supporting feet

121: The first side

122: second side

123: Linear segment

124: arc section

20: Melt glue

30, 30A, 30B: finished product

31: third side

32: Fourth side

33, 33A, 33B: gate

40: Mould

41: The first injection molding area

42: The second injection molding area

D: diameter

F1: First direction

R: Fillet treatment

T0: total thickness

T1: first thickness

T2: second thickness

T3: third thickness

T12: thickness

W: width

FIG. 1 is a flow chart of the coating plastic injection molding method for thick lenses of the present invention.

FIG. 2 is a schematic structural diagram of an embodiment of the first semi-finished product formed by the method of FIG. 1. FIG.

FIG. 3 is a schematic structural diagram of an embodiment of the finished product formed by the method of FIG. 1.

Fig. 4 is a top view of the structure of the embodiment in Fig. 3;

Fig. 5 is a cross-sectional structural view of A-A in Fig. 4;

6A to 6D are schematic diagrams of manufacturing process embodiments of the coating plastic injection molding method for thick lenses of the present invention.

FIG. 7 is a structural diagram of an embodiment in which the finished product formed by the method of FIG. 1 has two supporting legs.

Fig. 8 is a schematic structural view of an embodiment in which the finished product formed by the method of Fig. 1 has three supporting legs.

Please refer to FIG. 1 to FIG. 5, the process 100 of a thick lens covering plastic injection molding method provided by the present invention includes the following steps: Step 102: Perform the first injection molding to form a first injection semi-finished product 10 with a melt having a first melt volume. The first injection semi-finished product 10 includes a first body 11 and a supporting leg 12, and the supporting leg 12 protrudes On the side of the first main body 11; and step 104: perform a second injection molding, and cover the outside of the first injection semi-finished product 10 with a melt 20 having a second melt volume and cover part of the supporting legs 12 to A finished product 30 is formed. The sum of the first melt volume and the second melt volume is the total melt volume of the finished product 30. The first melt volume accounts for 17-40% of the total melt volume. The direction F1 has a total thickness T0, which is equal to or greater than 20 millimeters (mm).

Please refer to FIG. 2 to FIG. 5, the thick lens of this embodiment is a fisheye lens, but it can also be in other forms, such as a square lens or a cone lens. The first body 11 has a first side 111 and a second side 112 opposite to each other along the first direction F1. The finished product 30 has a third side 31 and a fourth side 32 opposite to each other along the first direction F1. The third side 31 Correspondingly disposed outside the first side 111, the fourth side 32 is correspondingly disposed outside the second side 112, and the supporting legs 12 of other parts not covered by the melt adhesive 20 protrude outside the finished product 30 and are close to the first side. Three sides 31.

As shown in FIG. 5, the appearance of the first semi-finished product 10 is similar to that of the finished product 30, so that the melt 20 can flow smoothly when filling and cover the outside of the first semi-finished product 10. In this embodiment, the first side 111 and the second side 112 of the first body 11 are both convex arc surfaces, but other aspects are also possible. For example, the first side 111 may be a flat surface, and the second side 112 may be It is a regular or irregular tapered surface, or a curved surface formed by multiple straight lines.

In this embodiment, the third side 31 is a circular flat surface, and the fourth side 32 is a convex arc surface. The diameter D of the third side 31 is equal to or greater than 60 millimeters (mm), the radian of the fourth side 32 is determined by the focal length and curvature of the fisheye lens and the diameter D of the third side 31, and the total thickness T0 is equal to Or the principle of greater than 20 millimeters (mm). For example, if the diameter D of the third side 31 is 75 millimeters (mm), the total thickness T0 can be 27.5 millimeters (mm).

4 to 5, the fourth side 32 and the second side 112 have a first thickness T1 along the first direction F1, the first body 11 has a second thickness T2 along the first direction F1, and the first A third thickness T3 is formed between the side 111 and the third side 31 along the first direction F1. The first thickness T1 and the third thickness T3 are smaller than the second thickness T2, and the second thickness T2 accounts for 40-62% of the total thickness T0.

The ratio of the first thickness T1 to the third thickness T3 is designed according to actual needs. For example, the first thickness T1 may account for 16-40% of the total thickness T0, and the third thickness T3 may account for 14-40% of the total thickness T0. But it is not limited to this.

Please refer to Figures 2 and 3, the supporting leg 12 has a thickness T12 and a width W. The thickness T12 is a dimension parallel to the first direction F1, the width W is a dimension perpendicular to the first direction F1, and the thickness T12 and a width W The size ratio is roughly 1:2 to 1:4.

The supporting leg 12 has a first surface 121 and a second surface 122 opposite to each other. The first surface 121 corresponds to the second side 112 of the first body 11 and has been rounded R, and the second surface 122 corresponds to the first The first side 111 of the main body 11 is flat. The rounded corners of the supporting leg 12 are designed with R design, and the shape of the supporting leg 12 is adjusted to reduce the resistance of plastic wave front flow and reduce the chance of encapsulation.

Please refer to FIG. 4 and FIG. 5, the supporting leg 12 is composed of a linear section 123 and an arc section 124. The second surface 122 of the linear segment 123 is correspondingly flush with the third side 31 of the finished product 30. The linear segment 123 is connected to the first body 11 by the arc-shaped segment 124. The length of the linear section 123 and the arc of the arc-shaped section 124 are not limited, depending on the size of the finished product 30. In other words, the supporting leg 12 can conform to the aforementioned thickness T12 and the width W in a ratio of approximately 1:2 to 1:4. The design principle of being partially covered by the melt adhesive 20 and partially protruding outside the finished product 30 is sufficient.

In this embodiment, the finished product 30 has a supporting foot 12, and the other side of the finished product 30 relative to the supporting foot 12 is a gate 33 formed during the second injection molding process, and the gate 33 is used to fill the molten glue 20.

Please refer to FIG. 6A to FIG. 6D, which illustrate an embodiment of the manufacturing process of a thick lens encapsulated plastic injection molding method provided by the present invention.

Please refer to FIG. 6A, a mold 40 is prepared, and the mold 40 has a first injection molding area 41 and a second injection molding area 42. After the mold 40 is closed, the first injection molding is performed in the first injection molding area 41 to form a first injection semi-finished product 10 with a first melt volume of melt (step 102 shown in FIG. 1). In this embodiment, the supporting leg 12 is formed after the runner of the first injection molding zone 41 is cooled.

Referring to FIG. 6B, the mold 40 is opened, and the first semi-finished product 10 is moved from the first injection molding area 41 to the second injection molding area 42. The support leg 12 of the first semi-finished product 10 is set upward, and the gate 33 for the second injection molding is set on the other side of the support leg 12.

6C, the mold 40 is closed, and the second injection molding is performed in the second injection molding area 42 to form a finished product 30 (step 104 shown in FIG. 1). At the same time, it is performed in the first injection molding area 41 Another first injection molding and forming another first semi-finished product 10.

6D, the mold 40 is opened, the finished product 30 is taken out from the second injection molding area 42, and the first semi-finished product 10 is moved from the first injection molding area 41 to the second injection molding area 42 for second injection molding. Secondary injection molding is performed to form another finished product 30.

Accordingly, by repeating the manufacturing processes shown in FIG. 6C and FIG. 6D, mass production of the finished product 30 can be carried out.

Please refer to FIG. 7. In this embodiment, the first semi-finished product 10A includes two supporting legs 12A, and the two supporting legs 12A are symmetrically arranged on two opposite sides of the first body 11A. In the finished product One side of 30A has a gate 33A, and two supporting legs 12A are symmetrically arranged with the gate 33A as the center. The configuration of the supporting legs 12A allows the molten glue entering from the gate 33A to have the same path length and the same resistance during the filling process (the supporting legs 12A and the first body 11A).

Please refer to FIG. 8, in this embodiment, the first semi-finished product 10B includes a first support leg 121B, a second support leg 122B, and a third support leg 123B, wherein the second support leg 122B and the third support leg 123B The first supporting legs 121B are centrally symmetrically arranged on two opposite sides of the first body 11B. There is a gate 33B on the other side of the finished product 30B relative to the first supporting leg 121B. In this embodiment, the first support leg 121B, the second support leg 122B, and the third support leg 123B are set on the side of the first body 11B at equal angles with the center of the first body 11B as the center. The one supporting leg 121B, the second supporting leg 122B, the third supporting leg 123B and the gate 33B can be arranged at equal angles apart. The supporting legs 121B, 122B, and 123B are arranged in such a way that the melt entering from the gate 33B has the same path length and the same resistance (support legs 122B, 123B and the first body 11B) during the filling process, so that the melt The flowing wave front of the glue is completely integrated at the supporting leg 121B and covers the supporting leg 121B.

The embodiments shown in Figure 4, Figure 7 and Figure 8 show that the finished product formed by the thick-piece lens covered plastic injection molding method provided by the present invention can be molded into different numbers of supporting legs according to the requirements. The change and design of quantity and position can prevent the flow wave front from meeting or combining early at the supporting foot and reduce the chance of encapsulation.

The coating plastic injection molding method of thick lens provided by the present invention has been used for many experiments, and the results are shown in Table 1 below:

In Table 1, the thickness T0 represents the total thickness T0 in FIG. 5. The thicknesses T1, T2, and T3 respectively represent the first thickness T1, the second thickness T2, and the third thickness T3 in FIG. 5. The “first shot” in the “melt volume” column represents the first shot used for the first shot of the semi-finished product 10 by the first injection molding method of the thick lens provided by the present invention. Melt volume. The “second shot” in the “melt volume” column represents the second melt volume used for the second injection molding using the thick lens covered plastic injection molding method provided by the present invention. The "first shot" in the "cooling time" column represents the cooling time required after the first shot of the semi-finished product 10 is completed. The "second shot" in the "cooling time" column represents the cooling time required after the finished product 30 is completed.

The "single shot" in the group represents the conventional one-shot injection molding method, and the numbers 1 to 9 in the group represent the two-shot injection molding method of the thick lens provided by the present invention. Nine sets of results from nine trials.

The finished product formed in Table 1 is the finished product 30 shown in FIG. 5. The diameter D of the third side 31 is 75 millimeters (mm), and the total thickness T0 is 27.5 millimeters (mm).

In terms of "single shot", the total volume of melt used is 63.86 cubic centimeters (cm ³ ), and the cooling time is 900 seconds.

Nine sets of results show that using the coating plastic injection molding method for thick lenses provided by the present invention, even if the thicknesses T1, T2, and T3 of each group are different, the volume of the first shot and the second shot are different, and the first shot The cooling time of shot and the second shot are different, but both can significantly save the cooling time by 16~33%. For example, compared to the 900 seconds required for a single shot, the cooling time of the sixth group is 761 seconds, and the cooling time of the seventh group is 603 seconds. The time saving ratio is 16% (saving 139 seconds) and 33% (saving 297 seconds) ). And the test results show that the quality of the finished product can be improved, and the shrinkage, deformation, and encapsulation of the finished product can be reduced.

The calculation of cooling time is based on the following formula:

among them:

t _k : cooling time d : thickness T _M : melting temperature

T _W : Mold temperature T _D : Demold temperature n : Number of times of product delamination measurement

The above formula shows that when the thickness decreases, the cooling time also decreases.

And, the calculation of the heat transfer rate of injection molding is based on the following formula:

among them:

Q : Heat transfer rate T _m : Melting temperature T _W : Mold temperature

K _I : Plastic thermal conductivity coefficient K _II : Mold thermal conductivity coefficient

h : heat convection coefficient S : thickness A _I : product surface area

The above formula shows that the smaller the value of the denominator, the higher the heat transfer rate.

In summary, the covered plastic injection molding method for thick lenses provided by the present invention is designed for the melt flow characteristics of thick lenses and the heat dissipation efficiency of the mold. The technical features include the layering of plastics. Thickness ratio, supporting foot structure, gate location and its injection molding method can indeed effectively reduce the coating bond line and quality defects (such as warpage, shrinkage, encapsulation, etc.) caused by the difference in wavefront flow during fractional molding And by reducing the heat of each injection of the melt, the cooling and production time of thick lenses can be greatly shortened.

Although the present invention has been disclosed in the above embodiments, it is not intended to limit the present invention. Anyone with ordinary knowledge in the technical field can make some changes and modifications without departing from the spirit and scope of the present invention. The scope of protection of the present invention shall be determined by the scope of the attached patent application.

100: Process of coating plastic injection molding method for thick lens

102, 104: Steps of the process flow of the thick lens covered plastic injection molding method

Claims (15)

A coating plastic injection molding method for thick lenses includes the following steps: performing the first injection molding to form a first injection semi-finished product with a first melt volume of melt, the first injection semi-finished product including a first A main body and at least one supporting leg, the supporting leg protruding from the side of the first main body; and a second injection molding is performed to cover the outside of the first semi-finished product with a second molten glue volume and Part of the supporting leg is covered to form a finished product. The sum of the first melt volume and the second melt volume is the total melt volume of the finished product. The first melt volume accounts for 17 of the total melt volume. ~40%, the finished product has a total thickness along a first direction, and the total thickness is equal to or greater than 20 millimeters (mm). As described in the first item of the scope of patent application, the covered plastic injection molding method of a thick lens, wherein the first body has a first side and a second side opposite to each other along the first direction, and the finished product is along the first side. One direction has a third side and a fourth side opposite to each other. The third side is correspondingly arranged outside the first side, and the fourth side is correspondingly arranged outside the second side. The supporting leg covering other parts protrudes from the outer side of the finished product and is close to the third side. As described in claim 2 of the covered plastic injection molding method of a thick lens, wherein the fourth side and the second side have a first thickness along the first direction, and the first body is along the The first direction has a second thickness, the first side and the third side have a third thickness along the first direction, the first thickness and the third thickness are smaller than the second thickness, and the second thickness accounts for 40~62% of the total thickness. As described in item 3 of the scope of patent application, the covered plastic injection molding method of thick lens, wherein the first thickness accounts for 16-40% of the total thickness, and the third thickness accounts for the total thickness 14~40%. As described in claim 2 of the covered plastic injection molding method for a thick lens, the third side is a circular flat surface, and the fourth side is a convex arc surface. As described in item 5 of the scope of patent application, the covered plastic injection molding method of a thick lens, wherein the diameter of the third side is equal to or greater than 60 millimeters (mm). As described in claim 2 of the covered plastic injection molding method for thick lenses, the first side is one of a flat surface or a convex arc surface, and the second side is a convex arc surface, a convex arc surface One of regular or irregular tapered surfaces. As described in any one of items 1 to 7 of the scope of the patent application, the covered plastic injection molding method for a thick lens, wherein the supporting leg has a thickness and a width, and the ratio of the thickness to the width is approximately 1: 2 to 1:4. As described in any one of items 2 to 7 of the scope of the patent application, the covered plastic injection molding method of a thick lens, wherein the supporting leg has a first surface and a second surface opposite to each other, and the first surface corresponds to The second side of the first body is rounded, and the second surface corresponds to the first side of the first body and is flat. As described in item 9 of the scope of patent application, the covered plastic injection molding method of thick lens, wherein the supporting leg is composed of a linear section and an arc section, and the second surface of the linear section corresponds to the finished product The third side is flush, and the linear section is connected with the first body through the arc section. The covered plastic injection molding method for thick lenses as described in claim 1, wherein the first semi-finished product has the supporting leg, and the other side of the finished product relative to the supporting leg has a gate . As described in claim 1 of the covered plastic injection molding method of a thick lens, the first semi-finished product includes two supporting legs, and the two supporting legs are symmetrically arranged on two opposite sides of the first body. As described in item 12 of the scope of patent application, the covered plastic injection molding method of thick lens, wherein a gate is provided on one side of the finished product, and the two supporting legs are symmetrically arranged with the gate as the center. The covered plastic injection molding method of thick lens as described in claim 1, wherein the first semi-finished product includes a first supporting leg, a second supporting leg, and a third supporting leg, wherein the second supporting leg The third supporting leg is symmetrically arranged on two opposite sides of the first body with the first supporting leg as the center. As described in claim 14 of the covered plastic injection molding method of a thick lens, wherein the finished product has a gate on the other side of the first supporting leg.

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