KR20240017577A - Simultaneous realization of automobile fuel port cover injection olding and two-color coating using in-mold coating - Google Patents

Abstract

The present invention relates to a technology that improves the existing in-mold coating process to simultaneously implement injection molding and two-color coating of an automobile gas cover. The first step of injection molding the automobile gas filler cover is to perform the first coating on the central area of the gas filler cover. The process consists of two steps, a second coating on the border area, and a third step of secondary coating on the border area. The first and second coating channels and coating materials that allow the coating material discharged from the mixing head to flow to the surface of the product to be coated The mold is designed by installing primary and secondary overflow areas to remove air bubbles generated during the flow process. During the injection molding process, the surface of the molded product is coated before taking it out of the mold, so the viscosity is very high. By using a low coating material, micro shapes can be created on the surface, defects in the appearance of injection molded products such as weld lines and flow marks are concealed after coating, and a very thick coating thickness can be realized in a single process, and the coating film is formed through a curing reaction. Because it forms a molding process, it has the advantage that volatile organic compounds are not discharged during the molding process. Since all coating materials are attached to the product as a coating film, the generation of waste is greatly reduced, as well as the pressure is reduced when the coating solution dries during the in-mold coating process. By relatively increasing the compressive residual stress, the effect of extending the fatigue life can be expected by increasing the surface properties of the product.

Description

Simultaneous realization of automobile fuel port cover injection olding and two-color coating using in-mold coating}

The present invention relates to a technology that improves the existing in-mold coating process to simultaneously implement injection molding and two-color coating of an automobile gas cover.

Injection molding is a polymer molding method that can produce high-quality processed products at a fast production speed without going through other post-processes, and is the most widely used process among polymer product manufacturing processes.

The coating process is a process to protect the finished product from external factors such as chemicals and water. It is an essential post-process that covers the surface of an object using processing methods such as evaporation coating, bar coating, dipping, blasting, and spreading to improve surface properties and decoration.

Flow analysis shortens the product development period by reducing the trial and error that occurs in the process of mass production from mold design. The problem of existing injection defects was solved through multiple experiments by installing the mold on an injection molding machine with real resin. Breaking away from the conventional method, we use a computer to analyze cooling assumptions, pressure behavior, and resin movement that were not visible during actual injection, and through this, we predict and suggest solutions for defects such as bending, weld lines, and shrinkage. Using flow analysis, you can expect to respond to design changes, solve problems, develop new products and increase design speed, implement ideal models for actual processes, systematically accumulate know-how, and expand and establish the scope of design management.

The in-mold coating method commercialized by Krauss Maffei in Germany is a mold cavity replacement method that allows substrate injection molding and coating to be carried out in different cavities. After injection molding the substrate using a thermoplastic resin, the mold is opened and the cavity plate attached to the fixed side is moved by sliding or the movable side mold is rotated to combine the core to which the substrate is attached and the coating cavity and apply the coating material. It consists of an injection and hardening process.

Automotive plastic molded products are advantageous for mass production and cost reduction, but have significant limitations in terms of the high quality demanded by customers, and separate post-processing processes such as plating, painting, and deposition are required to respond to this. However, the post-treatment process has a complex manufacturing process, a long lead time due to multiple repetitive operations, and the use of hazardous substances, which generates a large amount of volatile organic compounds and bad odors.

Most of the existing surface treatment methods for injection molding have complex manufacturing processes and require multiple repetitive coating processes when the coating thickness is thick. In addition, there is a problem that many defective products are generated due to the influence of the surface condition and manufacturing environment of the plastic injection molded product.

In order to reduce these problems, technologies such as in-mold decoration, in-mold label, and film insert molding, which integrate the injection and coating processes by placing a coating material molded into the desired shape in advance in the mold during the injection molding process, have been introduced, but the post-processing steps are reduced. Although it is long, it has the disadvantage of having to prepare the coating material in advance.

Existing in-mold coating was to implement injection molding and one type of coating material simultaneously in the mold, but recently, the need to coat two different colors in automobile interior and exterior parts to enhance design sensitivity is increasing. .

In order to develop a technology for coating an automobile gas filler cover with two colors in a mold at the same time as injection molding, a sealing edge to prevent leakage of the coating material that occurs during the first and second coating processes, an overflow area to remove air bubbles, There is a need to develop molds by improving coating channels, etc.

The process consists of the first step of injecting the car gas cover, the second step of performing the first coating on the central area of the gas filler cover, and the third step of performing the second coating on the border area, and the coating material discharged from the mixing head is coated. The mold is designed to install primary and secondary coating channels that allow the product to flow to the surface of the desired product, and primary and secondary overflow areas to remove air bubbles generated during the flow of the coating material.

In the substrate injection molding process including the coating channel and overflow area, the gate position and thickness design to satisfy the flow balance of the resin are important, so three types of design plans were created by varying the design variables of the width and depth of the coating channel. Using Moldex3D, the optimal design is derived through flow analysis.

During the injection molding process, since the surface of the molded product is coated within the mold before taking it out of the mold, micro shapes can be created on the surface using a coating material with very low viscosity, and external defects in the injection molded product such as weld lines and flow marks are prevented by coating. It has the effect of being concealed afterwards.

A very thick coating thickness can be achieved in a single process, and since the coating film is formed through a curing reaction, there is an advantage that volatile organic compounds are not discharged during the molding process.

In addition, since all coating materials are attached to the product as a coating film, the generation of waste is greatly reduced.

When the coating liquid dries during the in-mold coating process, pressure is applied to relatively increase the compressive residual stress, thereby increasing the surface properties of the product, which has the effect of extending fatigue life.

Schematic diagram of the mold for 1st and 2nd coatings

Before manufacturing the mold according to the present invention, injection molding flow analysis is performed using Moldex3D to calculate and design the width and depth values of the coating channel and overflow area. This is because the gate location and thickness that satisfy the flow balance of the resin are very important in the substrate injection molding process.

Based on the above flow analysis, the coating channel is designed to have a width of 7.952 mm and a depth of 1 m so that the coating material injected through the mixing head satisfies uniform flow and flows on the surface of the substrate.

The coating material used at this time is a two-component polyurea, and the viscosity of the base material and hardener is very small, about 1/10,000 to 1/100,000 compared to general thermoplastic resin, so a sealing edge is installed along both lines of the coating channel to prevent leakage of the coating material. Designed to be installed.

In the overflow area, a groove with a width of 9.107 mm and a depth of 9 mm, which is 3 to 4 times the coating thickness, is installed in consideration of the above flow analysis to control the flow direction of the coating material and prevent bubbles from occurring on the product surface. It is designed so that air bubbles can be easily discharged.

The sealing edge is designed to prevent coating material from leaking during the first and second coating processes. In the case of the first coating in the center area, a square-shaped sealing edge is installed in the coating channel and overflow area, and a separate sealing edge is not installed on the parting surface.

Additionally, in the case of secondary coating on the border area, a separate sealing edge is required to prevent the secondary coating material from infiltrating the primary coating area. Therefore, the first coating material is used to form a triangular sealing edge with a width of 0.7 mm and a height of 1 mm. When the mold is closed for the second coating, the sealing edge is pressed to prevent the second coating material from invading the first coating area. It is designed to prevent leakage of the secondary coating material by forming a triangular sealing edge with a width of 0.1 mm and a height of 0.5 mm using injection molding materials in the parting part.

In summary, the design described above is combined with the primary coating cavity while the substrate is attached to the core mold, and the primary coating material discharged through the mixing head attached to the side coats the center area of the product through the coating channel and 1 It is configured to flow into the secondary overflow area.

After curing of the primary coating material is completed, the mold is opened and the hydraulic cylinder is operated to move the coating cavity upward. Afterwards, the core mold to which the primary coated substrate is attached and the secondary coating cavity are combined and the mixing head is operated. The secondary coating material discharged through the product is configured to coat the edge area of the product. Figure 1 below shows the coating cavity and core mold for performing the first and second coatings on the injection molded substrate surface within the mold.

After injection molding is completed, the mold is rotated 180 degrees with the template while the substrate is attached to the mold on the movable side, and the mixing head is fastened to the side of the first coating cavity and the second coating cavity. When the first coating is completed, the hydraulic cylinder is operated. The template is designed to move upward and perform secondary coating.

Coating is achieved by the base material and hardener supplied to the mixing head by a high-pressure pump, passing through a filter, then being sprayed through nozzles A and B, respectively, mixed uniformly by the collision energy generated during spraying, and discharged into the mold through the mixing head exit. Design. Based on the above flow analysis, the diameter of each nozzle of the mixing head for coating is 0.38 mm and 0.40 mm for nozzles A and B for the first coating, and 0.18 mm and 0.20 mm for nozzles A and B for the second coating, respectively. Designed in mm.

Claims (3)

The process consists of the first step of injecting the car gas cover, the second step of performing the first coating on the central area of the gas filler cover, and the third step of performing the second coating on the border area, and the coating material discharged from the mixing head is coated. In-mold coating is designed to design a mold by installing primary and secondary coating channels that allow the product to flow to the desired product surface, and primary and secondary overflow areas to remove air bubbles generated during the flow of the coating material. A method of simultaneously implementing injection molding and two-color coating on a car gas filler cover.
In claim 1,
A method of simultaneously implementing injection molding of a car gas tank cover and two-color coating using in-mold coating to design a mold through flow analysis using Moldex3D for three types of design plans by varying the design variables of the width and depth of the coating channel.
In claim 1,
After injection molding is completed, while the base material is attached to the mold on the movable side, it rotates 180 degrees with the template and fastens the mixing head to the side of the first coating cavity and the second coating cavity. When the first coating is completed, the hydraulic cylinder is operated to move the template. A method of simultaneous injection molding and two-color coating of an automobile gas filler cover using in-mold coating designed to move upward and perform secondary coating.