Ultra-long grid type two-color decorative frame and production method thereof

Abstract

The present application relates to a kind of super-long grid type two-color decorative frame and its production method.The decorative frame has the structure such as elongated strip, arc-shaped outer surface, two end arc transition, etc., and is provided with grid-shaped light-emitting array and non-light-transmitting area on its light-emitting surface, and light forms light and shade interbedded light-emitting effect after passing through light-transmitting small square block on grid.The present application optimizes and improves forming die from gate structure and arrangement distribution, waterway structure and other aspects, to better solve the problem of weld line at lower cost, improve the quality of decorative frame product, meet the requirements of host factory, and has good economic benefit.

Description

Technical Field

[0001] This invention relates to the field of automotive lighting technology, specifically to an extra-long grille-style two-tone decorative frame and its manufacturing method. Background Technology

[0002] With the development of technology, car lights are constantly being upgraded and replaced. The original halogen bulbs have been gradually replaced by current LED car lights and even laser headlights. In addition to the change in light source, the shape and structure of car lights have also changed dramatically. Slender, continuous car lights and car lights with unique lighting shapes are more popular with consumers.

[0003] Therefore, our company specially developed and designed a combination taillight and matching decorative frame for a certain OEM, the structure of which is as follows: Figure 1-3 As shown in the image, the decorative frame is integrally injection molded, with a slender, elongated shape and an arc-shaped outer surface. Its light-emitting surface features a grid-like light-emitting array and opaque areas. The light-emitting array consists of rectangular or arc-shaped translucent squares arranged at regular intervals along a straight line. When the LED light source is lit, optical structures such as reflectors reflect the light onto the decorative frame. The light passes through the translucent squares on the grid, creating an alternating light and shadow effect, which is highly technological and enhances brand recognition.

[0004] However, the decorative frame is over 1.1 meters long. Due to its length and the fact that it is a two-tone injection molded part with a surface structure of small, dense grids (7mm wide and 30mm high) and a transparent part covering a black surface, products manufactured using conventional injection molding processes are prone to warping, deformation, and visible weld lines, severely impacting product yield and manufacturing costs. During the early mold design phase of this project, Moldflow analysis revealed that the weld lines (…) were caused by the product's shape. Figure 4 The problem (in the middle circle area) cannot be effectively avoided. Figure 4 The left-middle figure shows the temperature change of the product surface during the injection molding process when the temperature is increased. Combined with the right figure, it can be seen that the weld line problem becomes more obvious when the temperature is close to the decomposition temperature of PC material. Increasing the fluidity of the material is not conducive to improving the weld line. Summary of the Invention

[0005] The purpose of this invention is to provide a production method for an extra-long grid-style two-color decorative frame. The method includes the following steps: First, under the normal molding temperature of PC (290-300℃), molten plastic in a two-color injection molding machine is injected into the cavity through the mold gate. During the molding process, a specific water channel is used for water circulation. Finally, the mold is opened to obtain a qualified extra-long grid-style two-color decorative frame product.

[0006] Furthermore, the gate is specifically a single-sided straight-through gate, and there are 3 gates, which are distributed at a certain distance on the same side of the cavity.

[0007] Furthermore, all the gates are located at the top of the two-color decorative frame (i.e., in direction B).

[0008] Furthermore, the distance between the central gate and the left and right side gates is equal, and this distance is equivalent to 25% of the length of the decorative frame.

[0009] Furthermore, in a two-color injection molding machine, the molten plastic first enters the main runner, and then simultaneously enters each gate through the sub-runners and fills the mold cavity.

[0010] Furthermore, the waterway is specifically structured such that water transport is separated on both the upper and lower sides, and the circulating water on the same side is controlled independently in segments.

[0011] Furthermore, the circulating water temperature on the lower side (side B in the diagram) is higher than that on the upper side (side A in the diagram).

[0012] Furthermore, the circulating water temperature on the lower side is controlled between 110-140℃, and the circulating water temperature on the upper side is controlled between 90-120℃.

[0013] Furthermore, multiple sets of independent circulating cooling water are symmetrically arranged on the upper and lower sides of the water channel.

[0014] Furthermore, five sets of independent circulating cooling water are installed on both the upper and lower sides of the water channel, and the temperature of the circulating cooling water gradually increases from the middle to the left and right sides.

[0015] The second objective of this invention is to provide an extra-long grille-style two-color decorative frame manufactured according to the above method.

[0016] Compared with existing conventional technologies, the beneficial effects of this invention are manifested in the following aspects: It deeply analyzes the problems existing in the two-color injection molding process of the ultra-long grille-style decorative frame, and makes targeted improvements from multiple aspects such as mold structure, product structure, and injection molding process. From the design stage to the production stage, each link has corresponding data analysis as support, promoting the optimization of product parts; this invention is completely different from the traditional approach of simply relying on improving injection molding process parameters, avoiding problems such as long R&D cycles, high R&D costs, and uncontrollable risks; this invention solves the quality problem of the through-type combined rear light decorative frame at a relatively low cost, significantly reducing the defective product rate and improving the economic benefits of enterprises. Attached Figure Description

[0017] Figure 1 The main view of the extra-long grille-style two-tone decorative frame;

[0018] Figure 2 A bottom view of an extra-long, grille-style, two-tone decorative frame;

[0019] Figure 3 for Figure 1 Enlarged view of the area circled in the middle;

[0020] Figure 4 This is a graph showing the results of the Moldflow analysis.

[0021] Figure 5 This is a simulation diagram of injection molding at the gate.

[0022] Figure 6 This is a simulation diagram of injection molding at the gate.

[0023] Figure 7 This is a schematic diagram of the water channel structure of the mold;

[0024] Figure 8 This is a photo of the actual product: an extra-long grille-style two-tone decorative frame. Detailed Implementation

[0025] To enable those skilled in the art to fully understand the technical solution and beneficial effects of the present invention, the following description is provided in conjunction with specific embodiments and accompanying drawings.

[0026] The orientations described in this invention, such as up, down, left, right, front, and back, are generally based on the front view of the decorative frame.

[0027] In fact, products with a similar two-color grid structure to this invention can be manufactured in various ways, such as two-color injection molding or laser engraving. Different methods have their own advantages and applicable scope. The reason why this invention uses two-color injection molding instead of other methods is mainly based on a comprehensive consideration of product quality and appearance consistency, cost, and customers' high standards for products. If the two-color grid is implemented using the traditional painting method, on the one hand, an additional process is added, which inevitably leads to a longer product production cycle and reduced efficiency. At the same time, other quality defects (such as pitting, fuzz, etc.) will be introduced during the painting process. On the other hand, the difference in tooling will inevitably lead to problems such as poor product consistency and unclear edge boundaries at the junction. If a coating method is used, since local color coating is required, a tooling masking method must be used. However, the structure of different toolings varies, and the coating method will also cause problems such as poor product consistency and long cycle.

[0028] To address this, this invention develops a novel industrial-scale mass production process for an ultra-long, grid-style, two-color decorative frame: The first step involves injection molding transparent PC material from below the mold; the second step involves injection molding black PC from above the mold. Ultimately, a white transparent part covers a black part. This process requires solving the weld line problem, and this invention addresses this issue primarily through two approaches: first, at the mold level, changing the gate location and using a valve gate; second, at the process level, employing rapid heating and cooling molding technology. The principle of rapid heating and cooling molding technology is to quickly raise the surface temperature of the mold cavity before injection molding, bringing it above the glass transition temperature of the polymer material. After the molten plastic has filled the mold cavity, the mold surface temperature is immediately lowered to the ejection temperature. While rapid heating and cooling molding technology can effectively eliminate surface defects in plastic products (such as weld lines, orange peel, and air bubbles), it places high demands on the mold, requiring it to possess both high toughness and high corrosivity, leading to a significant increase in production costs. Furthermore, rapid heating and cooling molding technology requires a specific high-gloss, non-marking machine to achieve rapid mold temperature changes.

[0029] Structural analysis of the ultra-long grille-style two-color decorative frame described in this invention determined that only straight-through gates could be selected, and they must be arranged in a single-sided distribution. Otherwise, shrinkage and air trapping problems are likely to occur during product injection molding. Moldflow analysis showed that the shrinkage of the product meets the requirements according to this gate distribution design, as indicated by the results. Figure 5-6 As shown.

[0030] Although the gate was redesigned, it was found that the weld line problem could not be completely and effectively avoided due to the product's shape. Therefore, the cooling water system also needed to be modified and optimized simultaneously. Figure 7 As shown, the mold's water channels are designed with separate upper and lower sections for water flow and segmented control. Using the injection direction as a reference, five circulating cooling water channels (①-②-③-②-①) are set from left to right on both sides of the cavity. Channel ① has a higher water temperature, channel ② is relatively lower, and channel ③ in the center has the lowest temperature. The mold temperature is set in these three segments primarily because the decorative frame has a certain curvature (higher in the middle and lower on both sides, with a curved transition at the edges) and there are holes in channel ③. Lowering the mold temperature from both ends towards the middle is more conducive to fading or even eliminating the weld line at the flow separation point. Furthermore, the water temperatures on both sides of the mold need to be different: the water temperature in direction A is controlled at 90-120℃, and the water temperature in direction B is controlled at 110-140℃. This is because direction A is the gate direction, and direction B is the weld line direction; increasing the mold temperature in direction B can make the weld line shallower. In addition, segmented temperature control can effectively prevent burns on the product surface. The relevant process parameters are as follows:

[0031]

[0032] The actual product of the extra-long grille-style two-color decorative frame obtained by this invention is shown below. Figure 8 As shown, the surface is almost free of defects such as weld lines, and even with large-scale mass production, it can supply stably with a yield rate of over 95%.

Claims

1. A method for producing an ultra-long grid-type two-color decorative frame, characterized by, The method comprises the following steps: firstly, designing a mold matched with the shape of the decorative frame; then, injecting molten plastic in a double-color injection molding machine into the cavity through the gate of the mold; using a water channel for water circulation during the molding; and finally, opening the mold to obtain a qualified super-long grid type double-color decorative frame product; the specific structure of the water channel is that the water on the upper and lower sides is separately arranged and independently controlled in sections on the same side, and the temperature of the circulating water gradually increases from the middle to the left and right sides.

2. The method of claim 1, wherein: The gate is designed as a straight-through gate distributed on one side, and the number of the gates is three and they are distributed at a certain distance on the same side of the cavity.

3. The method of claim 2, wherein: The distance between the middle gate and the left and right gates is equal, and the distance is equivalent to 25% of the length of the decorative frame.

4. The method of claim 2, wherein: The molten plastic in the double-color injection molding machine first enters the main runner, and then enters each gate and fills the cavity through the sub-runner at the same time.

5. The method of claim 1, wherein: The temperature of the circulating water on the lower side is higher than that on the upper side.

6. The method of claim 5, wherein: The temperature of the circulating water on the lower side is controlled between 110-140℃, and the temperature of the circulating water on the upper side is controlled between 90-120℃.

7. The method of claim 6, wherein: The water channel is symmetrically provided with five groups of circulating water on the upper and lower sides.

8. The method of claim 7, wherein: The temperature of each circulating water on the lower side from left to right is 140℃, 120℃, 110℃, 120℃, and 140℃, and the temperature of each circulating water on the upper side is 20℃ lower than the temperature of the corresponding position on the lower side.

9. An ultra-long grid-type two-color trim frame, characterized by: The decorative frame is prepared according to any one of the methods in claims 1-8.

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