How to use a shell-type vacuum suction port

Abstract

This invention provides a process for manufacturing molded thermoplastic sheets using a formed shell-shaped mold. [Means for Solving the Problem] A method for using a shell mold manufactured by: a pattern groove forming step of forming a pattern groove in a shell mold prototype; a vacuum suction hole forming step of irradiating the same position on the back side of the shell mold prototype where the pattern groove position is formed on the shell mold prototype with laser light multiple times under different conditions to form a vacuum suction hole in which the hole diameter on the back side of the shell mold is at least twice the hole diameter on the front side of the shell mold; a thermoplastic sheet placement step of placing a thermoplastic sheet on the surface of the shell mold; a heating step of heating the thermoplastic sheet at a temperature between 100°C and 220°C; and a suction step of applying a vacuum suction force on the back side of the shell mold at a rate of -0.01 kilograms per square centimeter to -1.5 kilograms per square centimeter.

Description

Technical Field

[0001] The present invention relates to a method of using a shell mold with vacuum suction holes.

Background Art

[0002] Conventionally, there has been a technique for transferring a fine pattern onto a sheet using a mold for sheet insert molding (hereinafter referred to as a "shell mold"). In this technique, when the fine pattern is on the micron order, it becomes difficult to accurately transfer the pattern. Therefore, a device has been devised in which fine vacuum suction holes are arranged in the fine pattern recesses of the shell mold to draw in the softened sheet member against the fine recesses. Also, various devices have been made for these vacuum suction holes, and the following techniques are known. In Patent Document 1, in order to solve the problems existing before, such as (1) it takes time and effort to form holes, (2) it takes time to reduce the pressure, (3) the openings are burned and soiled, (4) the hole diameters vary, and (5) the vacuum suction efficiency is reduced, when laser processing the vacuum suction holes of the shell mold, the laser beam is irradiated multiple times under different conditions at the position where the vacuum suction holes should be formed, thereby forming vacuum suction holes in which the hole diameter on the back surface of the shell mold is twice or more the hole diameter on the surface of the shell mold. A method for forming the vacuum suction holes of the shell mold is disclosed.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, even when using the method for forming the vacuum suction holes of the shell mold described in Patent Document 1, it is not possible to transfer a desired fine pattern onto the sheet unless the heat treatment of the sheet and the suction force of the vacuum suction holes are optimized. This is because these conditions must be optimized according to the structure of the vacuum suction holes and the like.

[0005] Therefore, the present invention provides a process for manufacturing a molded thermoplastic sheet using a formed shell-shaped mold. [Means for solving the problem]

[0006] As the first invention, a method for using a shell mold manufactured by forming a pattern groove in a shell mold prototype and forming a vacuum suction hole by irradiating the same position on the back side of the shell mold prototype where the pattern groove is formed with a pattern groove multiple times under different conditions, thereby forming a vacuum suction hole where the hole diameter on the back side of the shell mold is at least twice the hole diameter on the front side of the shell mold, is provided, comprising a thermoplastic sheet placement step of placing a thermoplastic sheet on the surface of the shell mold, a heating step of heating the thermoplastic sheet at a temperature between 100°C and 220°C, and a suction step of applying a vacuum suction force on the back side of the shell mold at a rate of -0.01 kilograms per square centimeter to -1.5 kilograms per square centimeter.

[0007] As a second invention, building upon the first invention, a method for using a shell-type structure with vacuum suction holes as described in claim 1 is provided, wherein the air pressure on the shell-type surface is 2 kilograms per square centimeter to 4 kilograms per square centimeter.

[0008] As a third invention, based on the first or second invention, a method for using a shell mold with a vacuum suction hole according to claim 1 or 2 is provided, wherein the diameter of the vacuum suction hole on the shell mold surface is 0.1 mm or more and 0.15 mm or less, and the thickness of the thermoplastic sheet is 0.8 mm or more and 4.5 mm or less.

[0009] As a fourth invention, based on the first or second invention, the present invention provides a method for using a shell-type vacuum suction device as described in claim 1 or claim 2, where the material of the thermoplastic sheet is one of polystyrene, ABS, polymethyl methacrylate, polycarbonate, polyphenylene sulfide, polytetrafluoroethylene, polyacrylonitrile, or a composite material of two or more of these, and the relationship between the thickness of the thermoplastic sheet and the heating temperature is T°C is 16.2a + 87 ≤ T ≤ 16.2a + 147.

[0010] As a fifth invention, a method for using a shell-type vacuum suction hole according to claim 1 or claim 2, based on the first or second invention, wherein the thermoplastic sheet is made of one of the following or a composite material of two or more of the following: polyethylene (PolyethylenePE) sheet, polypropylene (Polypropylene, PP) sheet, polyvinyl chloride (Polyvinyl Chloride, PVC) sheet, polyethylene terephthalate (Poly Ethylene Terephthalate, PET) sheet, acrylic (Poly Methyl Methacrylate, PMMA) sheet, polycarbonate (Polycarbonate, PC) sheet, ABS (Acrylonitrile Butadiene Styrene) resin sheet, polystyrene (Polystyrene, PS) sheet, and polyethylene terephthalate glycol (Polyethylene Glycol Terephthalate, PETG). [Effects of the Invention]

[0011] The invention comprising the above steps provides a method for using a shell mold with vacuum suction holes to manufacture a molded product of a thermoplastic sheet. [Brief explanation of the drawing]

[0012] [Figure 1] This figure shows an example of the processing flow for the method of using the shell-type vacuum suction port according to Embodiment 1. [Figure 2]Figure showing an example of the process flow of the method of using a shell mold with vacuum suction holes according to Embodiment 1 [Figure 3] Cross-sectional view showing an example of the step of forming a pattern groove according to Embodiment 1 [Figure 4] Cross-sectional view showing an example of the step of forming a vacuum suction hole according to Embodiment 1 [Figure 5] Cross-sectional view showing an example of the step of placing a thermoplastic sheet in a mold according to Embodiment 1 [Figure 6] Cross-sectional view showing an example of the step of heating a thermoplastic sheet according to Embodiment 1 [Figure 7] Cross-sectional view showing an example of the step of performing vacuum suction after heating according to Embodiment 1 [Figure 8] Cross-sectional view showing an example of the optimization of the method of using a shell mold with vacuum suction holes according to Embodiment 1 [Figure 9] Diagram of the material, softening temperature, and heating temperature of the thermoplastic sheet according to Embodiment 1 [Figure 10] Cross-sectional view showing an example of the width and depth of the pattern groove according to Embodiment 1 [Figure 11] Diagram showing an example of the optimization of the width of the pattern groove and the heating temperature for the method of using a shell mold with vacuum suction holes according to Embodiment 1 [Figure 12] Diagram showing an example of the optimization of the depth of the pattern groove and the vacuum suction force for the method of using a shell mold with vacuum suction holes according to Embodiment 1 [Figure 13] Cross-sectional view showing an example of a mold composed of a shell mold and a mold fixing member according to Embodiment 1 [Figure 14] Diagram showing an example of the dimensions of the pattern groove and the vacuum suction hole according to Embodiment 1 [Figure 15] Diagram showing an example of the pattern on the surface of the molded product according to Embodiment 1 [Figure 16] Figure showing an example of the process flow of the method of using a shell mold with vacuum suction holes according to Embodiment 2 [Figure 17] Cross-sectional view showing an example of a mold fixing member and a shell mold when applying air pressure according to Embodiment 2 [Figure 18]A diagram showing an example of the process flow of the method of using a shell type with vacuum suction holes according to Embodiment 3 [Figure 19] A diagram showing an example of the process flow of the method of using a shell type with vacuum suction holes according to Embodiment 4 [Figure 20] A diagram showing an example of the material and heating temperature of a thermoplastic sheet according to Embodiment 4

Modes for Carrying Out the Invention

[0013] Hereinafter, embodiments of each invention will be described. The present invention should not be limited to these embodiments, and can be implemented in various modes without departing from the gist thereof. The present invention should not be limited to these embodiments, and can be implemented in various modes without departing from the gist thereof.

[0014] <Embodiment 1> Embodiment 1 mainly relates to Claim 1 and the like.

[0015] <Embodiment 1: Outline> A method of using a shell type manufactured by a pattern groove forming step of forming a pattern groove in a shell type prototype and a vacuum suction hole forming step of forming a vacuum suction hole having a hole diameter on the back surface of the shell type that is 2 times or more the hole diameter on the front surface of the shell type by irradiating a plurality of laser lights at different conditions at the same position on the back surface side of the pattern groove position formed in the shell type prototype. A thermoplastic sheet is placed on the surface of the shell type, the thermoplastic sheet is heated at a temperature between 100°C and 220°C, and the vacuum suction force on the back surface of the shell type is -0.01 kilogram per square meter to -1.5 kilograms per square meter. This is a method of using a shell type with vacuum suction holes, characterized by suction. The softening point of the thermoplastic sheet is a very important index in the molding process. By grasping the softening point, optimal molding conditions can be set and high-quality products can be manufactured. (1) Determination of molding conditions: By heating the sheet at a temperature higher than the softening point, the fluidity necessary for molding can be ensured. (2) Heat resistance of the product: Deformation of the product can be prevented by using it at temperatures below its softening point. (3) Recycling: Thermoplastic resins can be remolded by heating, but if they are heated beyond their softening point, the resin may decompose. Factors determining the softening point include the type of resin, such as polyethylene and polypropylene, which have different softening points. Furthermore, higher molecular weights tend to result in higher softening points. Additionally, additives such as plasticizers can alter the softening point.

[0016] <Embodiment 1: Processing Flow> (Embodiment 1: Processing Flow: Overview) Figure 1 shows an example of the processing flow in the method of using the vacuum suction hole shell type according to this embodiment. As shown in the figure, the method of using the vacuum suction hole shell type according to this embodiment consists of a groove pattern formation step S0101, a vacuum suction hole formation step S0102, a thermoplastic sheet placement step S0103, a heating step S0104, and a suction step S0105. The processing in each of these steps will be explained below using Figures 2 to 8.

[0017] Figure 2 is a conceptual diagram for visually understanding the processing content at each step in the processing flow of the present invention, and is a schematic cross-sectional view showing the central longitudinal section of each component. Details of the arrangement at each step will be explained in detail step by step using Figures 3 to 8, and here we will briefly overview the overall processing flow.

[0018] Figure 2(a) is an enlarged cross-sectional view of a part of the shell mold prototype. The shell mold primarily serves two purposes: (1) to shape the molded product and (2) to transfer patterns to the surface of the molded product. Because the shell mold is very thin (3 to 5 millimeters), it is placed on a mold fixing member that is shaped similarly to the shell mold, and the molded product is manufactured. The material of the shell mold prototype can be metals such as zinc alloy, nickel, and steel, or ceramics. Note that this figure is merely a schematic representation of the shell mold prototype and does not accurately show the actual specific shape, the dimensional ratio of the shell mold portion to the entire mold, or the dimensional ratio with respect to the base which is the mold fixing member (the same applies to the specific shapes and dimensions of each component and the dimensional ratios between components in Figures 2(b) to (f), and also to these in Figures 3 to 9).

[0019] As shown in Figure 2(b), in the groove pattern formation step, pattern 0201 is applied to the surface of the shell mold. The pattern is for transfer to the molded product, and the surface of the shell mold is inverted. The pattern is not particularly limited, but can be a repeating arrangement of a textured pattern, a mesh pattern, a geometric pattern, etc.

[0020] Next, as shown in Figure 2(c), in the vacuum suction hole formation step, vacuum suction holes are formed at the locations where the surface pattern of the shell mold is located. Vacuum suction is a method of pressing a thermoplastic plastic sheet to the mold by removing the air from inside the mold and creating a vacuum state. By expelling the air with a vacuum pump, the plastic sheet is pressed against the mold by atmospheric pressure, and is molded into a more precise shape. In addition, patterns can be applied to the molded product by transferring the inverted pattern applied to the surface of the mold. The shape of the vacuum suction port is not particularly limited, but it may be cylindrical or conical.

[0021] As shown in Figure 2(d), in the thermoplastic sheet placement step, a thermoplastic sheet is placed on the surface of the shell-shaped mold. A thermoplastic sheet is a sheet made from thermoplastic resins such as polyethylene, polypropylene, and ABS resin, using co-extrusion molding or other methods. Thermoplastic sheets have the property of softening when heated and solidifying when cooled, and are also recyclable.

[0022] Next, as shown in Figure 2(e), the heating step involves heating the thermoplastic sheet with a heater to soften it. The dashed arrows extending from the heater indicate that the thermoplastic sheet is being heated by the heater.

[0023] Finally, as shown in Figure 2(f), in the suction step, vacuum suction is performed from the back side of the shell mold. This ensures that the thermoplastic sheet adheres closely to the shell mold, allowing for precise shape fabrication and transferring the inverted pattern applied to the surface of the shell mold to the molded product. After a predetermined time has elapsed, the vacuum suction is stopped and the thermoplastic sheet is removed from the shell mold.

[0024] The following details the processes involved in each step. First, there is the preparation step for forming the shell mold. The preparation step comprises a pattern groove formation step and a vacuum suction hole formation step. The preparation step does not need to be performed for each molded product, and the shell mold can be used repeatedly. After that, the process moves on to the molded product manufacturing step. The molded product manufacturing step comprises a thermoplastic sheet placement step, a heating step, and a suction step.

[0025] (Embodiment 1: Processing flow: Pattern groove formation step) Figure 3 is a conceptual diagram for visually understanding the process in the step of forming the pattern groove, and is a schematic cross-sectional view of the central longitudinal section of the shell-shaped prototype. Conventional methods for applying patterns to a shell-shaped prototype include (1) etching, (2) laser processing, and (3) insert molding. (1) Etching Methods: Methods of directly etching a mold include methods that involve immersing the mold material in chemicals and selectively dissolving it (wet etching), and methods that use energy such as plasma to physically or chemically remove the material (dry etching). Wet etching is relatively inexpensive, suitable for processing large areas, and has the advantage of being able to form fine patterns. Dry etching allows for high-precision microfabrication and has the advantage of having a lower environmental impact compared to wet etching. (2) Laser processing method: Laser processing is a method of creating patterns by irradiating a material with laser light to vaporize it or cause a chemical reaction. There are various types of lasers, such as CO2 lasers (suitable for processing non-metallic materials), YAG lasers (suitable for processing metallic materials), and femtosecond lasers (lasers with extremely short pulse widths, used for microfabrication). It has the advantages of being non-contact, having little thermal deformation, enabling high-precision processing, and being able to handle a wide variety of materials. (3) Insert molding method: This method uses a technology to integrate metal or other materials with plastic. Inserts, which are pre-molded parts made of metal or other materials and conforming to the shape of the product, are placed in a mold, and molten plastic is injected around them and solidified to complete a product in which the insert and plastic are integrated. Insert molding is expected to improve production efficiency and reduce costs because multiple processes can be combined into a single molded product. By combining metal and resin, it is possible to create lightweight and high-strength parts, and the shape and function can be freely adjusted, making it suitable for a variety of applications.

[0026] The textured pattern applied to the shell-shaped surface refers to a pattern created by applying fine wrinkles to the surface, mimicking the texture of materials such as leather, fabric, or carbon fiber. An inverted pattern of the textured surface is formed on the shell-shaped surface. This is because the inverted pattern is transferred to the thermoplastic sheet to create the textured pattern. In this embodiment, the dimensions of the pattern grooves vary depending on the type of pattern and are designed appropriately according to the intended use, shape, and dimensions of the molded product. In this embodiment, it is important that the reversal pattern agent fills the grooves, holes, and other depressions formed by the pattern without any gaps. The specific dimensions of the pattern grooves will be described later.

[0027] Although not shown in the diagram, it is desirable to include a shell mold placement guide installation step before the pattern groove formation step S0101. This step involves creating grooves or steps on the surface of the mold fixing member using NC (Numerical Control) machining to guide the placement of the shell mold. The purpose of this step is to prevent misalignment or distortion of the shell mold relative to the mold fixing member by precisely controlling the placement of the shell mold using these guide grooves or steps. In this way, the fine patterns that appear on the final molded product can be positioned and shaped as intended.

[0028] (Embodiment 1: Process flow: Vacuum suction hole formation step) Figure 4 is a conceptual diagram for visually understanding the process in the step of forming a vacuum suction hole, and is a schematic cross-sectional view of the central longitudinal section of the shell-type prototype. The vacuum suction holes 0401 may be formed by laser processing. Numerous vacuum suction holes 0401 are formed dispersed throughout the entire surface of the shell-type prototype, but not at the edges. The step of forming the vacuum suction holes 0401 is performed by forming them at the same position on the back surface as the pattern grooves formed on the surface of the shell mold prototype. The vacuum suction holes 0401 may be formed by irradiating the same position on the back surface of the shell mold with laser light multiple times under different conditions, so that the diameter of the holes on the back surface of the shell mold is at least twice the diameter of the holes near the pattern grooves formed on the surface of the shell mold. Furthermore, the step of forming the vacuum suction hole 0401 may include a sub-step of forming a pilot hole that penetrates the shell mold by irradiating a laser beam at a predetermined position on the back surface of the shell mold under a first condition, and a sub-step of forming a vacuum suction hole by irradiating a laser beam at the same position as the predetermined position under a second condition different from the first condition, such that the diameter of the pilot hole is enlarged on the back surface of the shell mold by an amount of enlargement greater than the amount of enlargement near the pattern groove formed on the surface of the shell mold.

[0029] In the step of forming the vacuum suction hole 0401, when irradiating with laser light multiple times under different conditions, it is preferable to lower the output in later irradiations than in earlier irradiations. Furthermore, it is preferable to lower the output in the second condition than in the first condition. This is because lowering the output makes it difficult to enlarge the hole diameter on the surface of the shell type, while making it easier to enlarge the hole diameter on the back surface of the shell type. It is preferable that the hole diameter on the back surface of the shell type is 2.5 times or more than the hole diameter on the surface of the shell type of the vacuum suction hole. For example, the step of forming the vacuum suction hole 0401 may be performed by using a laser processing machine to drill a hole using a CO2 laser (pulsed oscillation, frequency: 50Hz, output: 110~140W, difference between peak output and average output: 20%) and an assist gas. Alternatively, the hole diameter may be enlarged such that the enlargement on the back surface of the shell type is greater than the enlargement on the front surface by irradiating a predetermined position on the back surface of the shell type with laser light perpendicular to the surface under first conditions (spot diameter: 200 micrometers, output: 120W, irradiation time: 1~2 seconds) and then irradiating a second condition different from the first condition (spot diameter: 200 micrometers, output: 110W, irradiation time: 1~2 seconds). This completes the preparation step.

[0030] (Embodiment 1 Processing Flow: Thermoplastic Sheet Placement Step) Figure 5 is a conceptual diagram for visually understanding the process in the step of placing a thermoplastic sheet on a shell mold, and is a schematic cross-sectional view showing the central longitudinal section of the shell mold.

[0031] Thermoplastic sheet 0501 is a sheet-like plastic product that softens when heated and hardens when cooled. Types of thermoplastic sheet 0501 include polyethylene (PolyethylenePE) sheets, polypropylene (Polypropylene, PP) sheets, polyvinyl chloride (Polyvinyl chloride, PVC) sheets, polyethylene terephthalate (Poly Ethylene Terephthalate, PET) sheets, acrylic (Poly Methyl Methacrylate, PMMA) sheets, polycarbonate (Polycarbonate, PC) sheets, ABS (Acrylonitrile Butadiene Styrene) resin sheets, polystyrene (Polystyrene, PS) sheets, polyethylene terephthalate glycol (Polyethylene Glycol Terephthalate, PETG), polymethyl methacrylate, polyphenylene sulfide, polytetrafluoroethylene, and polyacrylonitrile. These composite materials may also be used. The composite may consist of not only two types of materials, but also three or more.

[0032] While there are no specific limitations on the thickness of the thermoplastic sheet 0501, it should be within the range of 0.8 mm to 4.5 mm. For products requiring a balance between strength and flexibility, such as automotive interior materials, home appliance exteriors, and signage, a typical thickness of 1 mm to 2 mm is desirable.

[0033] (Embodiment 1 Processing Flow: Heating Step) Figure 6 is a conceptual diagram for visually understanding the process in the step of heating the thermoplastic sheet, and is a schematic cross-sectional view showing the central longitudinal section of the shell-shaped sheet. The rectangle located above the thermoplastic sheet represents a heater, which heats and softens the thermoplastic sheet placed on the shell mold using heater 0601. The wavy arrow 0602 extending from heater 0601 indicates that the thermoplastic sheet is being heated by the heater. The temperature of heater 0601 is in the range of 100°C to 220°C. The heating time varies depending on the temperature of heater 0601 and the thickness of the thermoplastic sheet, but is in the range of 0.5 seconds to 10 seconds. Heating can be performed by an electric heater, but heat transfer to the thermoplastic sheet may be by radiant heating or hot air heating. Contact heating may also be used, but it is preferable to do so gently at a rate of 2 kg / cm² or less on the thermoplastic sheet. The temperature setting is based on the surface temperature of the radiant heating element in the case of radiant heating, the hot air outlet temperature in the case of hot air heating, and the temperature of the contact surface in the case of contact heating. The shell mold surface temperature is preferably room temperature or room temperature + 30°C at the time of the thermoplastic sheet placement step. Room temperature refers to the indoor working temperature, which is approximately between 18°C ​​and 28°C.

[0034] The following are some methods for heating: (1) Oven heating: A method of heating by placing the entire thermoplastic sheet in an oven. (2) Infrared heating: A method of directly heating the side of the thermoplastic sheet that is not in contact with the shell type using an infrared heater. (3) High-frequency heating: A method of heating from the inside of a thermoplastic sheet using high-frequency current. (4) Hot air heating: A method of heating a thermoplastic sheet by blowing hot air onto it.

[0035] (Embodiment 1 Processing Flow: Suction Step) Figure 7 is a conceptual diagram for visually understanding the process in the step of aspirating a thermoplastic sheet, and is a schematic cross-sectional view showing the central longitudinal section of a shell-shaped structure. The thermoplastic sheet, softened by heating, adheres tightly to the surface of the shell-shaped mold by suction from the vacuum suction holes, forming the shape of the object. More specifically, as shown in the figure, the thermoplastic sheet, softened by heating, fits almost seamlessly into the pattern grooves formed on the surface of the shell-shaped mold, thus taking shape.

[0036] The vacuum suction force should ideally be between -0.01 kilograms per square centimeter and -1.5 kilograms per square centimeter. The vacuum suction force will vary depending on the heater temperature, the thickness of the thermoplastic sheet, and the heating time.

[0037] Figure 8 is a conceptual diagram for visually understanding the process of heating and vacuum-suctioning a thermoplastic sheet, and is a schematic cross-sectional view showing the central longitudinal section of a shell-shaped sheet. Figure 8(a) shows an example of the state of a thermoplastic sheet that may occur when the heating temperature is high, the heating time is long, or the vacuum suction force is strong. For example, if the heating temperature is high and the heating time is long (even if the heating temperature is appropriate, if the heating time is long), the thermoplastic sheet will soften too much, its viscosity will decrease (it will flow easily), and it will melt. As a result, there is a risk that the melted thermoplastic sheet will flow out from the pattern grooves into the vacuum suction holes, resulting in the creation of unintended protrusions and other shapes. Figure 8(b) shows that when the heating temperature is low (or the heating time is short, even if the heating temperature is appropriate), the thermoplastic sheet does not soften, becomes highly viscous (difficult to flow), and is difficult to deform. As a result, the thermoplastic sheet may not fill the grooves of the pattern, and unintended patterns may be created. Figure 8(c) shows that by setting optimized heating temperature, optimized heating time, and optimized vacuum suction force for a thermoplastic sheet of a predetermined material and thickness of the thermoplastic sheet, it is possible to manufacture molded products with the desired shape and pattern.

[0038] Figure 9 shows the materials, softening temperatures, and heating temperatures (softening temperature + 20°C) of thermoplastic sheets. For example, the softening temperature of polyethylene is 80°C to 90°C and the heating temperature is 100°C to 110°C, the softening temperature of polypropylene is 110°C to 140°C and the heating temperature is 130°C to 160°C, and the softening temperature of ABS resin is 70°C to 100°C and the heating temperature is 90°C to 120°C. Each thermoplastic sheet material has an appropriate heating temperature, and the degree of softening of the thermoplastic sheet varies depending on the thickness of the thermoplastic sheet and the heating time.

[0039] Figure 10 is a conceptual diagram illustrating the relationship between pattern grooves and vacuum suction holes in a thermoplastic sheet, and is a schematic cross-sectional view of the central longitudinal section of a shell-shaped sheet. W represents the width of the pattern groove, D represents the depth of the pattern groove, d1 represents the diameter of the vacuum suction hole on the surface of the shell-shaped sheet, and d2 represents the diameter of the vacuum suction hole on the back surface of the shell-shaped sheet. Heating by a heater is indicated by a dashed arrow. Furthermore, vacuum suction is indicated by a white arrow. In the case of textured surfaces, the length of each groove is typically around 100 to 500 micrometers, the width W is around 100 to 300 micrometers, and the depth D is around 100 to several hundred micrometers. In the case of fine patterns, the general dimensions are that the length of each groove is around 50 to 1000 micrometers, the width W is around 50 to 500 micrometers, and the depth D is around 50 to 1000 micrometers. Furthermore, there is a certain correlation between length / width and depth; the longer (wider) the length (width), the deeper the depth, and the aspect ratio (width:depth) is generally within the range of approximately 2:1 to 1:2.

[0040] The spacing r of the vacuum suction holes is approximately 0.6 mm to 2.0 mm. Furthermore, the diameter d1 of the vacuum suction holes is 0.05 to 0.15 mm near the pattern groove on the surface side of the shell mold prototype, and widens towards the back side, with the diameter d2 of the vacuum suction holes being 0.2 to 0.3 mm on the back side of the shell mold prototype. The diameter d1 of the vacuum suction holes on the surface of the shell-type is smaller than the diameter d2 of the vacuum suction holes on the back surface of the shell-type. Therefore, the vacuum suction force near the vacuum suction holes on the surface of the shell-type is stronger than that near the vacuum suction holes on the back surface. As a result, when a heated thermoplastic sheet is vacuumed, a portion of the thermoplastic sheet adheres to the area near the vacuum suction holes on the surface of the shell-type, increasing the surface roughness (see Z in Figure 10). This may cause the diameter of the vacuum suction holes on the surface of the shell-type to become slightly smaller, and the vacuum suction force near the vacuum suction holes on the surface of the shell-type may become stronger than the desired vacuum suction force. Surface roughness should be measured periodically, and if it exceeds a certain value, the thermoplastic sheet adhering to the area near the vacuum suction holes on the surface of the shell-type should be removed. There are two methods for measuring surface roughness: contact-type shape measuring machines and non-contact-type shape measuring machines. (1) Contact-type shape measuring machine: A needle called a diamond stylus is brought into contact with the surface, and its movement is measured to capture the surface shape, which is then evaluated using parameters such as average roughness (Ra) and maximum height (Rz). (2) Non-contact shape measuring machine: This machine measures surface shape non-contact using laser light or optical interference. It can measure three-dimensional shapes and provides a more detailed understanding of the surface shape.

[0041] The process of smoothing surface roughness is called surface polishing, and there are various methods, with the optimal method varying depending on the material of the product and the required surface quality. (1) Mechanical polishing Polishing using abrasives is a method of physically removing material from a surface using abrasive paper, abrasive cloth, or polishing paste. The type of abrasive used, such as diamond paste, cerium oxide, or alumina, is selected based on the material being polished and the desired surface roughness. This method has the advantages of being relatively inexpensive and suitable for processing large areas. However, it has the disadvantage of potentially reducing dimensional accuracy because it removes the surface layer. (2) Chemical polishing Electrolytic polishing is a method of smoothing a metal surface by dissolving it with an electric current. Chemical polishing, on the other hand, is a method of dissolving a surface using chemicals. Both methods have the advantage of being able to smooth even minute irregularities and achieve a mirror finish. However, they also have the disadvantages of potentially having a high environmental impact and requiring long processing times. (3) Physical polishing Ultrasonic polishing is a method of polishing a workpiece surface by using ultrasonic vibrations to cause polishing particles to collide with the workpiece.

[0042] Figure 11 is a graph illustrating the relationship between the width W of the pattern groove and the temperature T added to the softening temperature (heating temperature). Based on empirical observation, the curved region shown in Figure 11 represents the desirable range for manufacturing molded products. The range expressed by the following equation represents a more desirable and optimized range. 200 ≤ W ≤ 550, T1 ≤ T ≤ T2 Here, T1 = -0.024W + 17.3 and T2 = -0.034 + 34.8. Furthermore, the relationship between the width W of the pattern groove and the temperature T may be within the region enclosed by the dotted line in Figure 11. However, in this case, the yield of the molded product may be reduced.

[0043] Figure 12 is a graph illustrating the relationship between the groove depth D and the vacuum suction force F. Based on empirical observation, the curved region shown in Figure 12 represents the desirable range for manufacturing molded products. The range expressed by the following equation represents the more desirable and optimized range. 50 ≤ D ≤ 300, F1 ≤ T ≤ F2 Here, F1 = 3.4 × 10 -3 D is -0.17, and F2 = 3.3 × 10 -3 The value is D+0.574. Furthermore, the relationship between the width W of the pattern groove and the temperature T may be within the area enclosed by the dotted line in Figure 12. However, in this case, the yield of the molded product may decrease.

[0044] (Embodiment 1 Processing Flow: Other Permitted Steps: Confirmation of Molded Product) There may be a step to verify whether the molded product has been manufactured as expected. This could involve visually inspecting a specified area of ​​the thermoplastic sheet, or randomly checking the width and depth of the pattern grooves. After checking, if there are no problems, proceed to the next step. If it is better to start over, you can go back to the heating step.

[0045] (Embodiment 1 Processing flow: Other permissible steps: Removal of molded product) The process may include a step of removing the thermoplastic sheet from the shell mold after the molded product has been manufactured. When removing the thermoplastic sheet from the shell mold, the molded product may be cooled to prevent deformation due to heating by the heater, or air may be blown onto the molded product for cooling.

[0046] <Embodiment 1: An example of a mold consisting of a shell mold and a mold fixing member> (Embodiment 1: Shell Type - Overview) Figure 13 is a conceptual diagram for visually understanding an example of a mold consisting of a shell mold 1301 and a mold fixing member 1305, and is a schematic cross-sectional view showing the central longitudinal section of the shell mold 1301 and the mold fixing member 1305. The shell mold 1301 is a thin mold that mimics a desired shape and includes a plurality of pattern grooves 1302, vacuum suction holes 1303 at the same positions on the back side of the pattern grooves 1302, and a fringe 1304 on the edge of the shell mold 1301. The fringe 1304 is for fixing the shell mold 1301 to the mold fixing member 1305.

[0047] (Embodiment 1: Mold Fixing Member: Overview) The mold fixing member 1305 is provided with a plurality of ventilation grooves 1306 and a plurality of ventilation holes 1307. The ventilation grooves 1306 are grooves formed on the surface of the mold fixing member 1305 and are passages for vacuum suction leading to the pattern grooves 1302 and vacuum suction holes 1303 formed in the shell mold 1301. The ventilation holes 1307 are passages for vacuum suction formed to penetrate the mold fixing member 1305 and are connected to an external vacuum suction device.

[0048] (Embodiment 1: Mold fixing member: Ventilation groove) Figure 14(b) schematically shows a plan view of the ventilation grooves formed in the mold fixing member. The groove width w1 of the path provided in the mold fixing member is approximately 0.3 mm to 0.7 mm, and these grooves are arranged at intervals w2 of approximately 0.9 mm to 1.5 mm in both the vertical and horizontal directions. Since all vacuum suction holes face the ventilation grooves and all ventilation grooves lead to the ventilation holes, air is drawn in from all vacuum suction holes, ensuring that the thermoplastic sheet adheres tightly to all recesses in the pattern of the shell-shaped surface. The shape of the ventilation grooves is not particularly limited; in addition to the rectangular cross-sectional shape shown in Figures 13 and 14, they may also be circular, semicircular, triangular, or the like.

[0049] (Embodiment 1: Mold fixing member: Ventilation hole) Returning to Figure 13, multiple ventilation holes 1307 may be provided in the mold fixing member. The diameter of the ventilation holes 1307 is not particularly limited, but 5 to 10 millimeters is preferable. The ventilation holes 1307 are connected to an external vacuum suction device. The ventilation holes 1307 may also be configured to allow fluid for temperature control to flow through them. For example, after manufacturing the molded product, flexible SUS piping may be connected to the ventilation holes and air, water, or other fluids may be flowed through them to cool the molded product and the mold.

[0050] (Embodiment 1: Mold fixing member: Material and thickness) The material of the mold fixing member 1305 is not particularly limited, but may be, for example, metal (aluminum alloy, steel, etc.), ceramic, etc. The thickness X of the mold fixing member shown in Figure 13 is not particularly limited, but is preferably 10 mm or more, and more preferably 20 mm or more. It provides high rigidity as a base and receiving tray for the shell type.

[0051] <Embodiment 1: Pattern applied to the surface of a molded product> (Embodiment 1: Pattern applied to the surface of a molded product: Overview) Figure 15 shows an example of the surface of a molded product with a pattern applied. Figure 15(a) shows an example of a textured pattern, Figure 15(b) shows an example of the planar shape of a fine pattern with a holographic pattern, and Figure 15(c) shows an example of the planar shape of a fine pattern with a lenticular pattern.

[0052] (Embodiment 1: Pattern applied to the surface of the molded product: Holographic pattern) Holographic patterns are created using a technology that reproduces three-dimensional images and patterns by recording the interference patterns produced by light reflected from an object onto a photosensitive material using two laser light sources. By making different images visible depending on the observer's viewpoint and the angle of incidence of light, a sense of depth is achieved. Although shown in achromatic in Figure 15(b), in reality, when viewed from this angle, the material appears in various colors such as red, orange, yellow, green, blue, and purple. Thus, transparent films with holographic patterns exhibit a rainbow-like shimmer due to the mutual interference of light reflected from objects. For this reason, micro-patterned films with holographic designs are often used in products where a sense of luxury is desired. For example, they are used in instrument panels and console boxes in car interiors, and in the packaging of high-end products such as luxury cosmetics. Furthermore, because holographic patterns are extremely difficult to replicate, they are also frequently used in products where counterfeiting should be prevented, such as banknotes and credit cards.

[0053] (Embodiment 1 Pattern applied to the surface of the molded product: Lenticular pattern) A lenticular pattern is a pattern created using a sheet of lenticular lenses, where the image changes depending on the viewing angle. Figure 15(c) shows an example of a perspective view of a lenticular patterned micro-patterned film. As shown in the figure, a lenticular patterned micro-patterned film consists of a lenticular lens and a composite image placed beneath it. The composite image is made up of images cut into strips, which are arranged so that a specific strip is visible when viewed from a specific angle. The dimensions of the lenticular pattern are also designed appropriately according to the application, shape, and dimensions of the molded product, but the length of a single recess is approximately 200 to 1000 micrometers, the width is approximately 200 to 500 micrometers, and the depth is approximately 200 to 1000 micrometers. In the case of lenticular patterns, there is a certain correlation between length, width, and depth, and the aspect ratio of width to depth is generally within the range of approximately 2:1 to 1:2.

[0054] <Effect of Embodiment 1> The present invention can provide an optimized process for manufacturing molded thermoplastic sheets using a formed shell-shaped mold.

[0055] <Embodiment 2> Embodiment 2 relates to claim 2, etc.

[0056] <Overview of Embodiment 2> The method of using the shell type with vacuum suction holes according to Embodiment 2 is based on the method of using the shell type with vacuum suction holes according to Embodiment 1, but is characterized in that the air pressure on the surface of the shell type is 2 kilograms per square centimeter to 4 kilograms per square centimeter.

[0057] <Embodiment 2: Processing Flow: Air Pressurization> Figure 17 is a cross-sectional view showing an example of a mold fixing member and shell mold when air pressurization is applied. In Embodiment 1, vacuum suction is performed from the back surface of the shell mold to make the thermoplastic sheet adhere tightly to the shell mold, but in Embodiment 2, in addition to vacuum suction, a step of pressing the thermoplastic sheet from above (the surface of the shell mold) with air pressure is included. As shown in Figure 17, the configuration involves installing a shield 1701 that covers a shell-type structure with vacuum suction holes in which a thermoplastic sheet 1702 is placed. This is to isolate it from the outside and increase the air pressure on the thermoplastic sheet. The shield 1702 has small holes 1703, and compressed air is injected through these holes 1703 into the internal space formed by the shield 1702 and the thermoplastic sheet. The thermoplastic sheet is pressed against the shell-type structure by the pressure of the compressed air, and adheres more tightly to the shell-type structure. In particular, when the thermoplastic sheet is flexed, or when the thermoplastic sheet does not soften sufficiently by heating, pressing the thermoplastic sheet from above with compressed air makes it adhere more tightly to the surface of the shell-type structure. The compressed air pressure ranges from 2 kilograms per square centimeter to 4 kilograms per square centimeter, which is several times the atmospheric pressure.

[0058] <Effects of Embodiment 2> The present invention provides an optimized process for manufacturing molded thermoplastic sheets using a formed shell-shaped mold, thereby ensuring that the thermoplastic sheet adheres more closely to the shell mold.

[0059] <Embodiment 3> Embodiment 3 mainly relates to claim 3, etc.

[0060] <Embodiment 3: Overview> The method of using the shell mold with vacuum suction holes according to Embodiment 3 is based on the method of using the shell mold with vacuum suction holes of Embodiment 1 or Embodiment 2, but is characterized in that the diameter of the vacuum suction holes on the shell mold surface is 0.1 mm or more and 0.15 mm or less, and the thickness of the thermoplastic sheet is 0.8 mm or more and 4.5 mm or less. The reason for this limitation is that the relationship between the thickness of the thermoplastic sheet and the diameter of the vacuum suction holes on the shell mold surface is important to prevent the thermoplastic sheet from being drawn into the vacuum suction holes and causing unwanted micro-protrusions to appear on the surface of the molded product. In other words, if the thermoplastic sheet is too thin relative to the diameter of the vacuum suction holes on the shell mold surface, the thermoplastic sheet will become more viscous and be drawn into the vacuum suction holes, and if the diameter of the vacuum suction holes on the shell mold surface is too large relative to the thickness of the thermoplastic sheet, the same thing will happen. Therefore, there is an appropriate numerical range for both, and this range is suitable for the purpose of producing micro-patterned molded products with a micro-pattern mold. The size specifications of the micro-patterns and the heating temperature are as described.

[0061] While the acceptable range for the diameter of the vacuum suction hole on the shell-shaped surface is 0.1 mm ± 0.05 mm, in Embodiment 3, the diameter of the vacuum suction hole on the shell-shaped surface is limited to 0.1 mm or more and 0.15 mm or less. Furthermore, the thickness of the thermoplastic sheet is limited to between 0.8 millimeters and 4.5 millimeters.

[0062] <Embodiment 3 Effects> The present invention provides an optimized process for manufacturing molded thermoplastic sheets using a formed shell-shaped mold, by limiting the thickness of the thermoplastic sheet and the diameter of the vacuum suction holes.

[0063] <Embodiment 4> Embodiment 4 mainly relates to claim 4, etc.

[0064] <Embodiment 4: Overview> The method of using the shell type with vacuum suction holes according to Embodiment 4 is based on the methods of using the shell type with vacuum suction holes of Embodiments 1 to 3, but has the characteristic that when the material of the thermoplastic sheet is one of polystyrene, ABS, polymethyl methacrylate, polycarbonate, polyphenylene sulfide, polytetrafluoroethylene, polyacrylonitrile, or a composite material of two or more of these, and the thickness of the thermoplastic sheet is a millimeter and the heating temperature is T°C, the relationship between the two satisfies the following relationship. 16.2a+87≦T≦16.2a+147

[0065] Figure 20 is a graph showing the relationship between the thickness a of the thermoplastic sheet and the heating temperature T. Based on experience, the thickness a of the thermoplastic sheet used is between 0.8 mm and 4.5 mm, and the heating temperature is between 100°C and 220°C, which allows for the provision of an optimized method for using a shell-type structure with vacuum suction holes. The gist of this equation is that as the thickness of the thermoplastic sheet increases, the heating temperature needs to be increased, and it is preferable to increase the temperature by approximately 16.2 times in millimeters. If the temperature T is lower than this lower limit, the resin will not flow into the fine shell-type pattern with sufficient yield, and if it is higher than this upper limit, the resin will flow into the inside of the vacuum suction hole, which is a problem.

[0066] <Embodiment 4 Effects> The present invention provides an optimized process for manufacturing molded thermoplastic sheets using a formed shell-shaped mold, by limiting the thickness of the thermoplastic sheet and the heating temperature.

[0067] <Embodiment 5> Embodiment 5 mainly relates to claim 5, etc.

[0068] <Embodiment 5: Overview> The method of using the shell type with vacuum suction holes according to Embodiment 5 is based on the methods of using the shell type with vacuum suction holes of Embodiments 1 to 4, and the material of the thermoplastic sheet is characterized by being one or more composite materials of two or more of the following: polyethylene (PolyethylenePE), polypropylene (Polypropylene, PP), polyvinyl chloride (polyvinyl chloride, PVC), polyethylene terephthalate (Poly Ethylene Terephthalate, PET), acrylic (Poly Methyl Methacrylate, PMMA), polycarbonate (Polycarbonate, PC), ABS (Acrylonitrile Butadiene Styrene) resin, polystyrene (Polystyrene, PS), and polyethylene terephthalate glycol (Polyethylene Glycol Terephthalate, PETG).

[0069] <Embodiment 5: Effects> The present invention can provide an optimized process for manufacturing molded products of specific thermoplastic sheets using a formed shell-shaped mold. [Explanation of Symbols]

[0070] S0101 Groove pattern forming step S0102 Vacuum suction hole formation step S0103 Shell type preparation steps S0104 Thermoplastic sheet placement step S0105 Heating step S0106 Suction Step S0107 Molded product verification step S0108 Thermoplastic sheet removal step 0201 Shell type 0202 Patterned groove 0203 Vacuum suction hole 0204 Thermoplastic Sheet 0205 Heater 1305 Mold fixing member 1306 Ventilation groove 1307 Ventilation holes

Claims

1. A pattern groove forming step in which pattern grooves are formed on a shell-shaped prototype, A vacuum suction hole formation step involves irradiating the same position on the back side of the pattern groove formed in the shell mold prototype with laser light multiple times under different conditions, thereby forming a vacuum suction hole in which the hole diameter on the back side of the shell mold is at least twice the hole diameter on the front side of the shell mold. A method of using a shell type manufactured by A thermoplastic sheet placement step involves placing a thermoplastic sheet on a shell-shaped surface, A heating step in which a thermoplastic sheet is heated to a temperature between 100°C and 220°C, A method for using a shell-type structure with a vacuum suction port, comprising a suction step in which a vacuum suction force on the back surface of the shell-type structure is applied at a rate of -0.01 kilograms per square centimeter to -1.5 kilograms per square centimeter.

2. A method for using a shell-type mold with vacuum suction holes according to claim 1, wherein the air pressure on the surface of the shell-type mold is 2 kilograms per square centimeter to 4 kilograms per square centimeter.

3. A method for using a shell mold with a vacuum suction hole according to claim 1 or claim 2, wherein the diameter of the vacuum suction hole on the shell mold surface is 0.1 mm or more and 0.15 mm or less, and the thickness of the thermoplastic sheet is 0.8 mm or more and 4.5 mm or less.

4. When the material of the thermoplastic sheet is one of the following: polystyrene, ABS, polymethyl methacrylate, polycarbonate, polyphenylene sulfide, polytetrafluoroethylene, polyacrylonitrile, or a composite material of two or more of these, If the thickness of the thermoplastic sheet is a millimeter and the heating temperature is T°C, the relationship between the two is: 16.2a+87≦T≦16.2a+147 A method for using a shell-type vacuum suction port according to claim 1 or claim 2, which satisfies the relationship.

5. A method for using a shell-type vacuum suction hole according to claim 1 or claim 2, wherein the material of the thermoplastic sheet is one of polyethylene, polypropylene, polyvinyl chloride, polyethylene terephthalate, acrylic, polycarbonate, ABS resin, polystyrene, polyethylene terephthalate glycol, or a composite material of two or more of these.

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