KR20200068473A - Method of the film insert injection molding - Google Patents

Abstract

The present invention relates to a method of injection-molding a film insert. The method of injection-molding a film insert comprises: dividing a product into a plurality of polygon regions having a predetermined area by drawing a Centroidal Voronoi Diagram (CVD) with respect to a surface area of the product using a computer program and extracting a central point position of the plurality of divided polygon regions to set a position of a gas pin (S1); forming a through hole communicating with an inside of a cavity at a rear surface of a mold at the position of the gas pin of the central point of the plurality of divided polygon regions obtained using the computer program (S2); installing a gas pin connected with a gas supply device in the formed through hole (S3); positioning a film inside a cavity of a mold in which the gas pin is installed (S4); injecting melt resin inside the mold in which a film is inserted by injection (S5); supplying gas to the gas pin installed at a rear surface of the mold through the gas supply device after injecting the melt resin (S6); and cooling the film insert for a predetermined time to form an injection product (S7).

Description

Method of the film insert injection molding

The present invention relates to a film insert injection molding method, and more specifically, to prevent the primer layer and the printing layer of the film from being wiped out in a conventional packing process through gas filling after injection during film insert injection molding, thereby providing a high quality product. It relates to a film insert injection molding method that can be produced.

Film insert injection molding is a technique of inserting a thin film of metal material printed in a mold in advance and injecting a plastic resin to mold a final product.

Conventional product surfaces have been plated or painted to improve durability or improve the appearance, but various problems such as performing many processes, performing post-processing, and generating environmental pollutants occur, and there are limitations on improving the appearance of products. It was necessary to develop a new manufacturing method against the back.

As one of the methods for solving such a conventional problem, a film insert injection molding technology has been developed in which resin is injected by inserting a film with a gloss or pattern printed thereon before injection of molten resin into a mold.

Film insert injection molding technology not only improves the durability and appearance of the product, but also solves problems that have occurred in the conventional plating or painting process, so it is widely used not only in the interior and exterior of automobiles, but also in mobile phones and various electronic products. .

However, in the film used to perform the film insert injection molding process, a printing layer is mainly formed through printing to implement various colors or patterns, and a primer treatment is performed on the film to be adhered to the material.

However, the treated film is frequently washed out due to the high injection pressure generated during injection, and a wash out phenomenon in which the primer and the printed layer are wiped out, and this phenomenon is particularly high when performing a holding process. The problem is marked by the injection pressure.

In recent years, not only a simple printed layer is used on the film surface, but various circuits are printed on the printed surface to supply power to a single product without a separate circuit. This is happening.

Of course, omitting the pressure holding step in the injection molding process can prevent the printing layer from being damaged or scratched, but when the pressure holding step is omitted, it is difficult to solve the shrinkage or deformation of the product surface due to pressure unevenness in the cavity. There was a problem.

-Republic of Korea Patent Publication No. 10-2010-11281 (Publication date: 2010.02.03, title of the invention: insert injection molding method of film) -Republic of Korea Patent Registration No. 10-1454159 (Registration Date: October 17, 2014, Title of the invention: Film insert injection molding apparatus and method) -Republic of Korea Patent Publication No. 10-2009-97037 (Publication date: 2009.09.15, title of the invention: film insert injection material and injection method)

The present invention was devised to solve the problems that occurred in the conventional film insert injection molding method, and in particular, prevents the inserted film from being damaged in the packing process during the injection molding process, thereby improving product productivity, and of course, high quality. The purpose is to provide a film insert injection molding method that enables the production of products.

In order to achieve the above object, the film insert injection molding method according to the present invention is divided into a plurality of polygonal regions having a certain area by drawing a central Voronoi Diagram (CVD) for a product surface area using a computer program. And extracting the positions of the center points of the divided polygonal regions to set the gas pin positions (S1); A through-hole perforation step (S2) of drilling through holes through the inside of the cavity at the rear surface of the mold at gas pin installation positions of a plurality of polygonal center points obtained using the computer program; Installing a gas pin connected to a gas supply device in the perforated through-hole (S3); A film insert step (S4) for positioning the film into the cavity of the mold where the gas pin is installed; Melt resin injection step (S5) for injecting the molten resin through injection into the mold into which the film is inserted; A gas filling step (S6) of supplying and filling gas with a gas pin installed on the back surface of the mold through a gas supply device after injection of the molten resin; Cooling for a certain period of time after filling the gas to form an injection product (S7); consists of a configuration comprising a.

In addition, the gas pressure charged in the gas filling step is 100 to 200 bar, the filling time is 5 to 10 seconds, and the filling gas used in the gas filling step is composed of air or nitrogen gas.

When injection molding is performed by the film insert injection molding method according to the present invention as described above, it is possible to improve the quality of the film insert product by preventing the phenomenon that the primer layer and the printing layer of the film generated by performing the conventional holding process are wiped out. It is possible to prevent loss of material due to occurrence of defective products.

In particular, when circuits and the like are printed on the film, damage to the circuit printed on the film is prevented, so that high-quality film insert products can be injected, thereby broadening the scope of application with a variety of functional products to further increase profitability.

1 and 2 are conceptual diagrams for dividing a product surface into a plurality of polygonal regions by using CVD applied to the present invention and an exemplary view of the Voronoi polygon obtained through the same.
Figure 3 is a state diagram showing a center point for installing a gas pin in the center of a polygonal region divided into a number using CVD,
Figure 4 is a schematic diagram of the gas pin is installed in the mold in the injection molding method according to the present invention,
Figure 5 is a schematic flow chart of the film insert injection molding method according to the present invention,
6 is a cross-sectional view of a film insert injection molded by the film insert injection molding method according to the present invention.

The film insert injection molding method according to the present invention is performed in the same or similar manner to the conventional general film insert injection molding method, but the gas filling process is omitted instead of the conventional holding process and omitting the holding pressure process that influences the quality of the injection molded product. Through this, it is possible to improve the quality of the injection molded product, which provides an injection molding method.

Particularly, the present invention obtains a plurality of polygonal regions by using a CVD (Centroidal Voronoi Diagram) for the location of a gas pin installed in a mold for gas injection, finds a center point of the polygonal region, and sets the installation location of the gas pin It is configured to complete injection molding through a gas filling process.

Therefore, the film insert injection molding method according to the present invention is divided into a plurality of polygonal regions having a certain area using a central Voronoi diagram (CVD) for a product surface area using a computer program, and the divided plurality The step of setting the central position of the polygonal area of the gas pin to set the installation position, and punching through holes through the cavity to the back of the mold corresponding to the gas pin installation position of the plurality of polygonal center points obtained through a computer program. A through-hole perforation step, a step of installing a gas pin connected to a gas supply device in the perforated through-hole, a film insert step of positioning the film into the cavity of the mold where the gas pin is installed, and a mold into which the film is inserted. The molten resin injection step of injecting the molten resin through injection, and the pressure inside the cavity through a plurality of pressure sensors sensing the pressure inside the cavity after injection of the molten resin to identify the pressure inside the cavity to the gas pin near the gate maintaining a relatively low pressure. It consists of a configuration including; a gas filling step of supplying gas and allowing gas to be filled into the cavity to maintain the same level as the upper pressure, and a cooling step of forming an injection product by cooling for a predetermined time after gas filling.

In addition, the filling gas used in the gas filling step is preferably composed of air or nitrogen gas.

Hereinafter, specific embodiments of the present invention will be described in detail with reference to the accompanying drawings.

In the present invention, by using a CVD (Centroidal Voronoi Diagram), the surface area of a mold (product) is divided into a number of polygons to find its center point, and a gas pin is installed at the center point to inject the molten resin and then gas charging through the gas pin It provides a method to obtain a high-quality film insert injection product by replacing the holding pressure process.

First, the CVD (Centroidal Voronoi Diagram) used in the present invention will be briefly described with reference to FIGS. 1 and 2.

FIG. 1 shows the concept of dividing a plurality of polygonal regions with respect to a product surface in order of using CVD in the present invention in order of (a), (b), (c), and FIG. 2 through the process of FIG. 1 The Voronoi polygon is divided into a plurality of polygonal regions.

CVD (Centroidal Voronoi Diagram) is to find the center point using a Voronoi Diagram.

That is, the Voronoi diagram (Voronoi Diagram), as shown in Figure 1 (a), by placing several points on the plane (generating point), select the two closest points perpendicular to the line perpendicular to the line connecting the two points Draw a bisector (b).

By connecting adjacent lines in this way and continuously drawing the vertical bisector of the connected line segment, the face on which the polygon that turns the vertical bisector is created is divided into polygons (c).

If this method is continued, as shown in FIG. 2, a Voronoi diagram is created from a polygon divided into a plurality.

On the other hand, CVD (Centroidal Voronoi Diagram) showing a central point in the center of a plurality of polygons divided into the above-described Voronoi polygon through a computer program is illustrated in FIG. 3.

In the present invention, the center point of the polygon found using CVD is determined as the installation position of the gas pin, which will be described later.

To find the center point of a plurality of Voronoi polygons, a computer into which basic information of a mold has been input is used, and [Equation 1] and [Equation 2] below are used to find the center point.

After finding the center point of each polygon by using the above-mentioned [Equation 1] and [Equation 2], a through hole is formed after marking the position to install the gas pin on the back surface of the mold at a position corresponding to the center point.

The through-hole to install the gas pin is formed to penetrate into the cavity from the back surface of the mold, and the gas pin is installed in the formed through-hole. In FIG. 4, the gas pin is formed inside the mold consisting of the upper mold 10 and the lower mold 20. The state in which 30 is installed is briefly shown.

As shown in FIG. 4, the gas pin 30 has an injection nozzle 32 for injecting gas into a cavity C filled with molten resin, and the injection nozzle through a through hole penetrated into the mold. The gas pipe 34 is installed inside the through-hole to supply the furnace gas.

Of course, although it is possible to install only the injection nozzle without inserting a separate gas pipe into the through hole processed in the mold, it is preferable to separately insert and install a gas pipe to prevent leakage of gas.

In addition, a gas supply hose 36 for receiving and supplying gas from the gas supply device 40 is connected to the end of the gas pipe 34 exposed to the back surface of the mold, and the operation and gas supply of the gas supply device 40 The time is configured to be automatically controlled by the main control unit of the computer on which the automatic control program is installed, and the automatic control process in such an injection molding process is performed normally, so a detailed description thereof will be omitted.

As described above, in the state in which the gas supply device 40 is connected to a plurality of gas pins 30 penetrating the rear surface of the mold, injection of the molten resin and product molding are performed by the following process. As gas filling using air or nitrogen gas is performed by the gas fins in the device, the non-uniform pressure inside the cavity is uniformly maintained so that products with improved quality can be produced.

That is, FIG. 5 shows a flowchart of a film insert injection molding method according to an embodiment of the present invention, and the injection molding process according to the present invention will be described with reference to this.

In order to perform injection molding using CVD according to the present invention, basically, after taking arbitrary points (creation points) with respect to the surface area of the mold while information related to the mold is input to the computer, draw the above-described Voronoi polygon, and boro Find the center point of each of the Noi polygons (S1).

Of course, in the process of obtaining the center point for each Voronoi polygon, after finding the center point for each polygon through the computer program using [Formula 1] and [Formula 2], the center point is displayed on the back surface of the mold.

The size or number of Voronoi polygons can be arbitrarily set by the operator on a computer program according to the type of resin forming the product or the size of the product.

The Voronoi polygon described above can be displayed or obtained in a 2D plane or a 3D shape, and the center point of the polygon can also be obtained in 2D and 3D coordinates.

Therefore, after finding the center point of each Voronoi polygon using a computer program, after marking the center point on the back surface of the actual mold, a through hole is drilled to penetrate the cavity inside the mold (S2).

After drilling a plurality of through holes, the prepared gas pin is inserted into each through hole (S3).

A gas pipe and a gas supply hose are connected to the gas pin, and the gas supply hose is connected to the gas supply device so that the gas supplied from the gas supply device is filled into the cavity of the mold through the gas pin.

After preparing the injection mold as described above, a film insert step of positioning the film into the cavity of the mold where the gas pin is installed is performed (S4).

In the film to be inserted, various pictures, patterns, and electric circuits are printed according to the characteristics of each product, and a primer layer is formed on the back surface in contact with the molten resin.

As described above, after inserting the film to be formed on the surface of the product into the cavity of the mold, the injection device is operated to inject the molten resin into the cavity to inject the molten resin (S5).

As the molten resin is injected into the cavity, its internal pressure rises, and the molten resin filled in the cavity is filled up to about 85 to 95% of the cavity volume, and is in contact with the primer layer of the film pre-installed therein. It is fused to the surface of the injection product.

As described above, after filling the molten resin, there was an inconvenience of performing a separate holding process in the prior art, but the present invention is air for 5 to 10 seconds at a pressure of about 100 to 200 bar into the cavity filled with the molten resin through a gas pin. Alternatively, nitrogen gas is filled (S6).

When the gas pressure to be filled is 100 bar or less, it is difficult to apply fluidity to the molten resin filled in the cavity, and if it is 200 bar or more, there is a risk that the printed layer of the film may be damaged by excessive pressure, and thus it is usually formed inside the cavity after pouring the molten resin. It is preferable to fill the gas with a pressure slightly higher than the pressure to be applied.

In addition, the gas filling time is set within 5 to 10 seconds, and it is preferable to quickly fill the molten resin in a relatively short time before the fluidity decreases, and gas filling may be controlled by dividing several times within the time.

As the gas filling is performed, the molten resin moves into the cavity where the pressure is kept low, thereby maintaining a uniform pressure distribution throughout the cavity, thereby damaging the primer layer and the print layer of the film contacting the surface of the injection product. When the cooling is performed for a certain period of time (S7) without being maintained in the first printed state, the inserted film maintains the printed layer as it is, and thus a solid fusion with the injection product is achieved.

The gas filling is automatically performed according to the time and pressure control set in the computer program, and the gas filling step may be repeated several times as necessary to be configured to allow gas filling.

When the film insert injection molding is performed through such a process, as shown in the cross-sectional view of FIG. 7, the primer layer and the printing layer of the film are not projected to one side, and the overall uniform state is maintained to prevent defects in the molded product. By reducing the product productivity, it is possible to produce high-quality products.

10: hieroglyph 15: gate
20: lower shape
30: gas pin 32: spray nozzle
34: gas pipe 36: gas supply hose
40: gas supply device
C: cavity

Claims (2)

Using a computer program, a central Voronoi diagram (CVD) is drawn for the product surface area to be divided into a plurality of polygonal regions with a certain area, and the location of the gas pin is extracted by extracting the locations of the center points of the divided polygonal regions. Setting step (S1);
A through-hole drilling step (S2) of drilling through-holes through the cavity from the rear surface of the mold at the installation positions of the gas pins of the plurality of polygonal center points obtained by using the computer program;
Installing a gas pin connected to a gas supply device in the perforated through-hole (S3);
A film insert step (S4) of positioning the film into the cavity of the mold where the gas pin is installed;
Melt resin injection step (S5) for injecting the molten resin through injection into the mold into which the film is inserted;
A gas filling step (S6) of supplying and filling the gas with a gas pin installed on the rear surface of the mold through the gas supply device after injection of the molten resin;
Film insert injection molding method characterized in that it consists of a configuration comprising a; cooling step (S7) for cooling a predetermined time after gas filling to form an injection product. According to claim 1,
The gas pressure charged in the gas filling step is 100 to 200 bar, and the filling time is 5 to 10 seconds.
Film insert injection molding method characterized in that the filling gas used in the gas filling step is composed of air or nitrogen gas.

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