A continuous process for producing a wood grain pattern on a plastic substrate for automotive interior decoration

Abstract

This invention discloses a continuous process for creating a natural wood grain effect on a plastic substrate for automotive interior trim, belonging to the field of automotive interior trim processing technology. The process includes the following steps: cutting → lamination and compounding → hot pressing preforming → insert injection molding → milling separation → grinding → spraying → packaging. During cutting, the corresponding positions of the wood grain are pre-planned and numbered on the wood veneer according to the assembly relationship of adjacent interior trim parts; the high-temperature film, wood veneer, adhesive film, and base fabric are laminated and compounded in the order of "high-temperature film—wood veneer—adhesive film—base fabric" and then hot-pressed into a curved shape; the preformed wood shell is used as an insert for injection molding, making the wood veneer and plastic substrate integrally formed; finally, milling separation, grinding, spraying, and packaging are performed to obtain the finished product. This invention has the advantages of simple process, strong mass production capability, and adaptability to irregularly shaped curved interior trim parts. While retaining the natural wood texture, it also possesses the dimensional stability of the plastic substrate, making it suitable for the mass production of high-end automotive interior trim parts.

Description

Technical Field

[0001] This invention belongs to the field of automotive trim panels, specifically relating to a continuous process for creating a real wood grain effect on a plastic substrate for automotive interior trim. Background Technology

[0002] As car consumption continues to upgrade, high-end models are paying more and more attention to the luxurious feel of their interiors. Real wood trim, with its unique natural grain, warm touch, and three-dimensional texture, is considered a hallmark of luxury cars and is widely used in areas such as the dashboard, center console, door panels, and steering wheel. Each grain of natural wood is unique, and this unreplicable natural attribute is precisely the core value of real wood trim.

[0003] Currently, the main technical routes for processing automotive wood interior parts are as follows: (1) Solid wood slab assembly process The design utilizes large slabs of raw wood, directly shaping them to achieve a natural and realistic wood grain. This approach directly processes solid wood into interior trim shapes, relying on the natural grain of the wood to achieve the decorative effect.

[0004] (2) Wood veneer application process Natural wood veneer is bonded to the surface of plastic or metal substrates using adhesives, allowing it to adapt to certain curved shapes. This process is mostly done on a piece-by-piece basis, with each interior component selected and veneered separately.

[0005] (3) Real wood IMD (In-Mold Decoration) process Real wood is extruded into sheets, and then attached to the surface of a plastic material through in-mold injection molding, achieving the integral molding of wood veneer and plastic substrate.

[0006] (4) Water transfer printing / heat transfer printing / UV printing simulated wood grain process Wood grain patterns are printed on the surface of plastic substrates using methods such as water transfer printing, heat transfer printing, or UV digital printing to simulate the appearance of real wood.

[0007] The aforementioned existing technologies have the following shortcomings: (1) The problem of wood grain splicing breakage is prominent. When the assembly gap between adjacent interior trim pieces is ≤4.5mm, existing technologies cannot achieve a smooth wood grain transition. Whether using solid wood veneer or wood paneling, each interior trim piece is typically made from independently selected materials, lacking wood grain alignment design between adjacent pieces. This results in broken or misaligned grain patterns at the joints after assembly, creating an abrupt visual effect and disrupting the overall aesthetic of the interior. While water transfer printing and other simulation techniques can achieve continuous grain, they are not based on natural wood materials.

[0008] (2) Solid wood slab solutions have poor adaptability The traditional log panel overlay solution is difficult to adapt to the irregular curved surfaces of plastic substrate interiors. After molding, the wood grain is prone to misalignment, resulting in extremely low material utilization and high processing costs. It is difficult to meet the needs of automotive interiors for complex shapes and mass production.

[0009] (3) The texturing process is complex and difficult to mass-produce. To achieve a continuous wood grain effect, high-end models employ a strict manual selection process for matching wood grain patterns (such as a selection rate of only 0.13% and 0.4% for mountain grain and straight grain patterns, respectively). This process is extremely time-consuming and costly, making it difficult to adapt to the needs of mass production. Furthermore, it is highly dependent on manual experience, making it difficult to guarantee consistent quality.

[0010] (4) The limitations of pure solid wood substrate are obvious. Solid wood substrates are susceptible to deformation and cracking due to temperature and humidity fluctuations, which limits their design options and makes them too expensive to meet the functional requirements of automotive interiors for dimensional stability and complex shapes. Summary of the Invention

[0011] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: A continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim includes the following steps: S1): Cutting: The high-temperature film, wood veneer, base fabric and adhesive film are placed into the cutting fixture according to the preset size for cutting; during cutting, according to the assembly relationship of adjacent interior parts, the corresponding positions of the wood grain of each part are pre-planned on the wood veneer, and each piece of wood veneer after cutting is numbered and marked. S2): Layered composite: The cut high-temperature film, wood veneer, adhesive film and base fabric are stacked and composited in the order of high-temperature film, wood veneer, adhesive film and base fabric to form a layered structure; S3): Hot pressing preforming: The laminated wood shell is placed into a hot pressing mold for hot pressing, so that the wood veneer is preformed into a semi-finished product with the same curved surface shape as the target interior part; S4): Insert injection molding: The pre-formed semi-finished product after hot pressing is placed into the injection mold as an insert for injection molding. The molten plastic flows on the back of the wood shell and solidifies to form a plastic substrate layer, so that the wood veneer and the plastic substrate are integrally formed. S5): Milling separation: Place the injection-molded semi-finished product into a milling fixture, and mill and separate the multiple interior parts that are connected as one piece according to the preset dividing line; S6): Grinding: Grinding the semi-finished product after milling to make it smooth; S7): Spraying: Spraying the ground semi-finished product; S8): Packaging: Package the qualified products according to their serial numbers.

[0012] Furthermore, the thickness of the wood veneer is 0.3~0.8mm.

[0013] Furthermore, the high-temperature film is made of PET and has a thickness of 0.3~0.8mm.

[0014] Furthermore, the base fabric is a fiber membrane.

[0015] Furthermore, in step S3, the process parameters for hot pressing are: temperature 135~145℃, pressure 80~90MPa, and time 180 seconds.

[0016] Furthermore, in step S4, the plastic substrate is a PC / ABS reinforced material, and the injection molding temperature is 230~270℃.

[0017] Furthermore, in step S7, the spraying includes sequentially applying a primer, applying a topcoat, and baking and curing, with the number of sprayed layers being 2 to 4.

[0018] Furthermore, the assembly gap between adjacent interior trim pieces is ≤4.5mm.

[0019] Furthermore, in step S1, the numbering mark is in the same numbering system as the numbering after milling and separation in step S5 and the numbering of packaging in step S8, and is used for matching and tracking of each component of the same set of interior parts throughout the entire process.

[0020] Compared with the prior art, the present invention has the following significant advantages: 1. Achieve natural and continuous wood grain even in narrow splicing gaps, eliminating abrupt visual breaks. This invention, through the core process concept of "planning the grain first and then injection molding," completes the grain alignment and splicing fixation of adjacent interior wood veneers before injection molding. This fundamentally solves the industry technical problem of wood grain breakage and misalignment and visual abruptness when adjacent real wood interior parts have an assembly gap of ≤4.5mm. It makes the wood grain at the splicing point connect naturally as if "the same piece of wood was cut and then put back together," greatly improving the overall coordination and high-end texture of the car interior.

[0021] II. Simplified process and strong mass production capability significantly reduce manufacturing costs. This invention achieves a continuous wood grain effect through seven core processes: cutting, lamination, hot pressing, injection molding, milling, grinding, spraying, and packaging. Combined with a unified numbering and tracking system throughout the entire process, texture matching can be completed in batches during the cutting stage, eliminating the need for traditional manual selection of grain patterns (the selection rate for mountain grain and straight grain is only 0.13%~0.4%). This significantly reduces the time and labor costs associated with grain matching, and the invention is simple to operate, has a low barrier to entry, and offers good mass production stability, making it suitable for large-scale industrial production.

[0022] Third, it balances the feel of real wood with structural performance and is compatible with irregularly shaped curved interior parts. This invention adopts a combination of "hot pressing preforming + insert injection molding" to allow the wood veneer to first adapt to the three-dimensional curved surface shape and then be integrally molded with the plastic substrate. This solves the problems of difficult wood veneer bonding and easy misalignment of wood grain in irregular curved interior parts. It also overcomes the defects of solid wood, such as easy deformation and cracking and limited shape, by replacing the pure solid wood substrate with the plastic substrate. At the same time, it fully preserves the texture, feel and three-dimensional layering of natural wood veneer, combining the high-end real wood feel with the dimensional stability of the plastic substrate, and fully adapts to the complex shape and functional requirements of automotive interiors.

[0023] The above description is merely an overview of the technical solution of the present invention. In order to better understand the technical means of the present invention and to implement it in accordance with the contents of the specification, the preferred embodiments of the present invention are described in detail below with reference to the accompanying drawings. Attached Figure Description

[0024] Figure 1 This is a schematic diagram of the process of this invention; Detailed Implementation

[0025] The preferred embodiments of the present invention will now be described in detail with reference to the accompanying drawings, so that the advantages and features of the present invention can be more easily understood by those skilled in the art, thereby providing a clearer and more explicit definition of the scope of protection of the present invention.

[0026] Example 1: Continuous wood grain processing for left and right trim pieces of automotive dashboard This example uses the two real wood trim pieces on the left and right sides of the dashboard of a high-end car model (see...). Figure 1 Taking [example 1] as an example, the implementation process of this invention will be described in detail. The assembly gap between the two decorative pieces is 4.5mm, requiring that the wood grain at the splicing point be naturally connected without any obvious breakage.

[0027] Materials preparation: Select the following materials: Wood veneer: White ash straight-grain natural wood veneer, 0.6mm thick; High-temperature film: 0.1mm thick transparent PET film, used to protect wood veneer from high-temperature damage during the injection molding stage; Base fabric: Fiber membrane, 0.3mm thick, used to enhance the tear resistance of wood veneer; Adhesive film: hot melt adhesive film, 0.1mm thick.

[0028] Step 1: Cutting The high-temperature film, wood veneer, base fabric, and adhesive film are placed into a cutting fixture according to the outline dimensions of the left and right trim pieces of the dashboard for cutting. During cutting, the grain direction is pre-planned on the wood veneer based on the assembly relationship (4.5mm gap) and final assembly position of the left and right trim pieces—ensuring that the wood grain of the left and right trim pieces connects naturally at the dividing line. After cutting, the corresponding wood veneers for the left and right trim pieces are marked with the numbers "L-01" and "R-01" respectively to ensure that the left and right trim pieces of the same dashboard are used in a matching manner.

[0029] Step 2: Lamination and Composite Stack the cut materials in the following order: high-temperature film—wood veneer—adhesive film—base fabric. When stacking, ensure that the edges of each layer are aligned and there are no wrinkles, and check the numbering marks to ensure that the left and right decorative pieces match accurately.

[0030] Step 3: Hot pressing preforming The laminated wood veneer is placed in a hot-press mold for hot pressing, pre-forming the flat wood veneer into the three-dimensional shape of the dashboard's curved surface. The hot-pressing process parameters are as follows: Temperature: 140℃ (allowable deviation ±5℃); Pressure: 85 MPa (range 80~90 MPa); Time: 180 seconds.

[0031] After hot pressing, the wood veneer, high-temperature film, adhesive film, and base fabric are bonded together to form a semi-finished wood shell that conforms to the curved shape of the dashboard. During the hot pressing process, the adhesive film melts and firmly bonds the wood veneer to the base fabric; the high-temperature film remains intact at high temperatures, providing protection for subsequent injection molding.

[0032] Step 4: Insert Injection Molding The pre-formed wood veneer is placed into an injection mold as an insert, and then injection molded. PC / ABS reinforcement is used as the injection material, and the injection temperature is 250℃ (the standard processing temperature for PC / ABS is 220-260℃). The molten plastic flows and solidifies on the back of the wood veneer, forming a 2.5-3.5mm thick plastic substrate layer, permanently bonded to the wood veneer.

[0033] During the injection molding process, the high-temperature film (PET film, 0.1mm thick) acts as a heat insulation and protective layer, effectively blocking the direct impact of the high temperature of injection molding on the wood veneer and preventing the wood veneer from being burned and discolored; the fiber film base cloth enhances the tear resistance of the wood veneer and prevents the wood veneer from cracking under injection pressure.

[0034] Step 5: Milling Separation The injection-molded semi-finished product is placed into a milling fixture, and the left and right decorative parts, which are connected as one piece, are separated by milling according to the preset dividing lines. Key points for milling accuracy control: The positional deviation of the dividing line is controlled within 0.3mm; The milled surface is smooth and burr-free.

[0035] After milling and separation, affix the same numbers "L-01" and "R-01" as in step one to the back of the left and right trim pieces respectively, and place them in a turnover box. The numbering system is used throughout the entire process to ensure that all parts of the same set of interior trim pieces are processed in a matching manner from beginning to end.

[0036] Step Six: Grinding The milled semi-finished products are then ground using a grinding machine to remove burrs and flash generated during injection molding and milling, resulting in a smooth and even surface for the wood veneer. Grinding is performed using progressively increasing grit (coarse grinding → fine grinding), achieving a surface roughness Ra ≤ 0.4μm after grinding. After grinding, the veneers are placed in turnover boxes with the same numbering system.

[0037] Step 7: Spraying The ground semi-finished products are placed on the paint tray according to their numbers "L-01" and "R-01" for uniform spraying. The spraying process includes: Primer application: Seals the wood veneer surface, providing basic protection; Topcoat application: provides gloss and weather resistance; Baking and curing: After each layer is sprayed, it is dried and cured at a temperature of 25~35℃ and a humidity of <60% for ≥24 hours.

[0038] In this embodiment, the number of sprayed layers is 3 (1 layer of primer + 2 layers of topcoat).

[0039] Step 8: Packaging The inspected and qualified left and right trim pieces are paired and placed in the packaging box according to the numbers "L-01" and "R-01" to ensure that the left and right trim pieces of the same dashboard are shipped together.

[0040] Implementation effect The dashboard's left and right wood trim pieces, processed using the above techniques, exhibit a 4.5mm assembly gap, with the wood grain seamlessly connecting at the joints, creating a continuous and uninterrupted grain pattern. The product combines the texture and feel of natural wood with the dimensional stability of a plastic substrate, resulting in a smooth and even surface that meets the requirements of high-end vehicle interiors.

[0041] Example 2: Continuous processing of wood grain on upper and lower trim pieces of automobile door panels This embodiment takes the upper and lower genuine wood trim pieces (assembly gap 2.8mm) of a certain car model door panel as an example. The process steps are basically the same as those in Embodiment 1, with the main differences as follows: Material differences: The wood veneer is made of black walnut straight-grain veneer, with a thickness of 0.5mm; The injection molding substrate is made of PP material (polypropylene); The high-temperature film is made of PET film with a thickness of 0.5mm.

[0042] Differences in process parameters: The injection temperature is adjusted to 230℃ (suitable processing temperature for PP material); Other hot-pressing parameters (140°C, 85MPa, 180 seconds) remain the same as in Example 1.

[0043] Implementation results: With a narrow assembly gap of only 2.8mm, the wood grain of the upper and lower trim pieces flows naturally and seamlessly at the dividing line, creating a strong sense of unity and meeting the stringent requirements of high-end models for genuine wood interior trim on door panels.

[0044] Example 3: Continuous wood grain processing of multiple decorative parts for the center console This embodiment takes three pieces of real wood trim on the center console of a certain car model (main trim + left and right auxiliary trim, with assembly gaps of 3.0mm and 3.2mm respectively) as an example to illustrate the implementation method of continuous wood grain processing for multiple (two or more) trim pieces of the present invention.

[0045] Materials and parameters: Wood veneer: White ash straight-grain veneer, 0.6mm thick; High-temperature film: PC film, 0.5mm thick; Base fabric: non-woven fabric, 0.3mm thick; Plastic substrate: PC / ABS reinforcing material; Hot pressing parameters: 140℃, 85MPa, 180 seconds; Injection temperature: 250℃.

[0046] Key implementation points: (1) Texture planning during the cutting stage: During cutting, the texture correspondence between the three pieces needs to be planned simultaneously—the main piece and the left auxiliary piece should connect in texture at a 3.0mm gap, and the main piece and the right auxiliary piece should connect in texture at a 3.2mm gap. The wood grain direction of the three pieces needs to be planned as a whole to ensure that the texture is continuous and smooth after the three pieces are assembled.

[0047] (2) Numbering Management: After cutting, the three pieces of wood veneer are numbered "C-01" (main decorative piece), "CL-01" (left auxiliary decorative piece), and "CR-01" (right auxiliary decorative piece). The numbering system runs through the entire process.

[0048] (3) Milling separation: After injection molding, the three pieces of the decorative parts that are connected as one piece are milled and separated according to the preset dividing line. The position deviation of the dividing line is controlled within 0.3mm.

[0049] Implementation results: The three center console trim pieces are seamlessly connected by wood grain within their respective assembly gaps, resulting in a continuous and smooth overall texture without any breaks or misalignments. This greatly enhances the overall harmony and luxurious feel of the center console area.

[0050] The above description is merely an embodiment of the present invention and does not limit the patent scope of the present invention. Any equivalent structural transformations made based on the content of the present invention specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the patent protection scope of the present invention.

Claims

1. A continuous process for creating a real wood grain effect on a plastic substrate for automotive interior trim, characterized in that... Includes the following steps: S1): Cutting: The high-temperature film, wood veneer, base fabric and adhesive film are placed into the cutting fixture according to the preset size for cutting; during cutting, according to the assembly relationship of adjacent interior parts, the corresponding positions of the wood grain of each part are pre-planned on the wood veneer, and each piece of wood veneer after cutting is numbered and marked. S2): Layered composite: The cut high-temperature film, wood veneer, adhesive film and base fabric are stacked and composited in the order of high-temperature film, wood veneer, adhesive film and base fabric to form a layered structure; S3): Hot pressing preforming: The laminated composite structure is placed into a hot pressing mold for hot pressing, so that the wood veneer is preformed into a semi-finished product with the same curved surface shape as the target interior part; S4): Insert injection molding: The pre-formed semi-finished product after hot pressing is placed into the injection mold as an insert for injection molding. The molten plastic flows on the back of the wood shell and solidifies to form a plastic substrate layer, so that the wood veneer and the plastic substrate are integrally formed. S5): Milling separation: Place the injection-molded semi-finished product into a milling fixture, and mill and separate the multiple interior parts that are connected as one piece according to the preset dividing line; S6）： Grinding: Grinding the semi-finished product after milling to make it smooth; S7): Spraying: Spraying the ground semi-finished product; S8): Packaging: Package the qualified products according to their serial numbers.

2. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interiors according to claim 1, characterized in that: The thickness of the wood veneer is 0.3~0.8mm.

3. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interiors according to claim 1, characterized in that: The high-temperature film is made of PET and has a thickness of 0.3~0.8mm.

4. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interiors according to claim 1, characterized in that: The base fabric is a fiber membrane.

5. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim according to claim 1, characterized in that: In step S3, the hot pressing process parameters are: temperature 135~145℃, pressure 80~90MPa, and time 180 seconds.

6. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim according to claim 1, characterized in that: In step S4, the plastic substrate is a PC / ABS reinforced material, and the injection molding temperature is 230~270℃.

7. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim according to claim 1, characterized in that: In step S7, the spraying includes sequentially applying primer, topcoat, and baking / curing, with 2 to 4 layers applied.

8. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim according to claim 1, characterized in that: The assembly gap between adjacent interior trim parts is ≤4.5mm.

9. The continuous process for producing genuine wood grain texture on a plastic substrate for automotive interior trim according to claim 1, characterized in that: In step S1, the numbering mark is in the same numbering system as the numbering after milling and separation in step S5 and the numbering of packaging in step S8, and is used for matching and tracking of each component of the same set of interior parts throughout the entire process.

Images