Direct bending and edge sealing process for panel for wooden door

Abstract

The invention relates to the technical field of wooden door bending and edge sealing, in particular to a direct bending and edge sealing process for a wooden door panel, which comprises the following steps: injecting molten high-temperature glue into an open groove in the inner side of the panel, and outwards diffusing and transferring heat energy of the glue to the inner side surface of the panel from the inside of the open groove of the panel; infrared radiation heating is synchronously applied to the bent position of the outer side surface of the panel, radiant heat can be transmitted to the inner side surface of the panel from the outer side of the panel, penetrates through a facing layer on the outer side of the panel and intersects with glue heat energy in the bent surface of the panel to form an isothermal softening area, and then the isothermal softened panel is bent and extruded to achieve curing forming. And edge sealing of the wooden door is completed. According to the invention, the technical problems of bidirectional collaborative isothermal heating of the panel, veneer protection and temperature difference reduction are realized.

Description

Technical Field

[0001] This invention relates to the field of wooden door bending and edge banding technology, and more specifically, to a process for directly bending and edge banding wooden door panels. Background Technology

[0002] The panel bending edge banding process for wooden doors is a technique that involves heating and softening the edges of the board, then bending it to fit the side of the door, ultimately achieving a seamless and continuous wrapping of the door's edges. Compared to the traditional edge banding strip process used for wooden doors, this process solves the problems of seams at corners and the susceptibility of edge banding strips to damage and breakage.

[0003] The aforementioned panel bending and edge sealing process for wooden doors involves milling grooves on the inside of the panel and injecting glue, then using a hot press to bend the panel to the side of the door. The heat during hot pressing softens the panel during bending, reducing the likelihood of panel breakage.

[0004] However, some current edge banding processes for wooden door panels rely solely on hot presses to heat and soften the panels, which leads to temperature differences between the inner and outer layers of the panel. This causes internal stress in the bending area, and this internal stress continues to act on the panel after it cools down, making the panel prone to cracking. Moreover, the contact hot pressing of the hot press can cause some panels with decorative layers (such as PVC and melamine) to overheat in certain areas, resulting in problems such as yellowing and blistering, which in turn affects the yield rate of wooden doors.

[0005] To solve the above problems, a direct bending and edge-sealing process for wooden door panels is needed that can reduce the temperature difference when the panel softens due to heating and protect the surface layer of the wooden door. Summary of the Invention

[0006] The purpose of this application is to provide a direct bending and edge-sealing process for wooden door panels, which achieves bidirectional coordinated isothermal heating of the panel, protects the finish, and reduces temperature differences.

[0007] To solve the above-mentioned technical problems, the solution adopted in this application is as follows:

[0008] A process for directly bending and sealing the edges of wooden door panels involves the following steps:

[0009] Step 1: Align the core board of the wooden door with the panel, and groove the inside of the panel where it is to be bent.

[0010] Step 2: Inject molten high-temperature adhesive into the groove on the inside of the panel. The heat energy of the adhesive diffuses outward from the groove to the inner layer of the panel.

[0011] Step 3: Simultaneously apply infrared radiation heating to the bend on the outer surface of the panel. The radiant heat energy is transferred from the outer side of the panel to the inner side of the panel, penetrates the outer decorative layer of the panel, and merges with the heat energy of the adhesive inside the bend of the panel to form an isothermal softening zone.

[0012] Step 4: The heated and softened panel is passed through a gradient curvature guide plate at a uniform rate to perform gradient bending and shaping, with the bending angle continuously increasing from 0° to 90°.

[0013] Step 5: Press the edge of the bent panel to provide pressure for the adhesive to cure during the curing process, thus completing the edge sealing of the wooden door core board.

[0014] Preferably, the ratio of the groove depth to the panel thickness is within the range of 0.3 to 0.6.

[0015] Preferably, the infrared wavelength range during infrared radiation heating is within 3μm to 6μm.

[0016] Preferably, the injection temperature range of the molten high-temperature adhesive is within 165~200℃.

[0017] Preferably, the extrusion time of the panel sealing edge is longer than the cooling and curing time of the molten high-temperature adhesive.

[0018] The technical solution of this application has at least the following advantages and beneficial effects:

[0019] In this invention, to address the temperature difference along the thickness of the panel in the traditional panel bending and edge-sealing process for wooden doors, and to reduce cracking in the bending area caused by internal stress, molten high-temperature adhesive is injected into the grooved panel. This allows the inner layer of the panel to soften through the heat energy of the adhesive. Furthermore, infrared radiation heating is applied to the outer surface of the panel. Specific wavelengths of infrared radiation penetrate the panel's finish and act on the substrate layer of the inner layer, causing the outer layer of the panel to soften through infrared heat energy. The combined heat energy from the inner and outer layers converges in the middle of the panel substrate to form an isothermal softening zone with a small temperature difference, further eliminating internal stress caused by temperature differences and reducing the occurrence of cracks and breaks during panel bending. Simultaneously, the specific wavelengths of infrared radiation, while heating the panel substrate layer, also slow down the temperature rise of the panel finish layer, reducing heat damage such as yellowing and bubbling caused by high temperatures, thus protecting the integrity of the finish layer.

[0020] To ensure uniform heat transfer (softening effect) at the panel bending points, the molten high-temperature adhesive on the inner side of the panel works in conjunction with the grooves. The adhesive penetrates rapidly into the inner layer of the panel through the grooves, maintaining the bonding function of the panel's inner bending area (grooved area) while allowing the adhesive's heat energy to quickly and evenly penetrate and be conducted to the inner layer of the panel. This allows the inner heat energy to be quickly and evenly conducted to the isothermal softening zone in the center of the panel. Meanwhile, infrared radiation from the outer side of the panel uses a specific wavelength to penetrate the outer decorative layer of the panel, thus acting on the outer layer of the panel. This reduces the temperature rise of the decorative layer and accelerates the temperature rise of the panel layer, thereby reducing the likelihood of cracks occurring when the decorative material is heated and bent. At the same time, it accelerates the conduction of infrared heat energy from the outer side of the panel to the isothermal softening zone in the center of the panel, working together with the molten high-temperature adhesive on the inner side to achieve a uniform softening effect for the panel. Detailed Implementation

[0021] The technical solutions of the present invention will be clearly and completely described below with reference to the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of the present invention.

[0022] It should be noted that similar reference numerals and letters below indicate similar items; therefore, once an item is defined, it does not require further definition or explanation thereafter. The use of terms such as "center," "upper," "lower," "inner," and "outer" to indicate orientation or positional relationships is based on the indicated orientation or positional relationship, or the orientation or positional relationship commonly used when the product is in use, and is only for the convenience of describing this application and simplifying the description, and does not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation, and therefore should not be construed as a limitation on this application. It should also be noted that unless otherwise explicitly specified and limited, the terms "set," "install," and "connect" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; a mechanical connection or an electrical connection; a direct connection or an indirect connection through an intermediate medium; or a connection within two components. Those skilled in the art can understand the specific meaning of the above terms in this application based on the specific circumstances.

[0023] Example

[0024] This invention provides a process for directly bending and sealing the edges of wooden door panels, the steps of which are as follows:

[0025] Step 1: Align the core board of the wooden door with the panel, and groove the inside of the panel where it is to be bent.

[0026] The process involves using a conveyor wheel assembly to synchronously transport and displace the wooden door core board and the panel, and then using a grooving structure to mill a groove on the inner side of the panel where it is to be bent.

[0027] Among them, grooving can provide bending avoidance grooves for the inner side of the panel when bending the panel, reducing the excessive compressive stress on the inner side of the panel, which can cause wrinkles or cracks, and improving the verticality of the panel after bending, thus improving the fit with the side of the wooden door.

[0028] The depth of the groove also affects the bending effect of the panel. When the groove is too shallow, the compressive stress on the inside of the panel is too great, which increases the thermal resistance and causes insufficient softening inside the panel. Insufficient softening will cause the internal fibers of the panel to break when bending (the strain force that the unsoftened area bears during bending will exceed the elongation at break).

[0029] When the groove is too deep, it affects the integrity of the panel structure. If the panel bend is too thin, after the wooden door edge banding is completed, the bend is prone to hidden cracks or even breakage due to external forces.

[0030] In this embodiment, please refer to Table 1. In order to test the best bending effect of different groove depths on the panel, panels with different groove depths were used to perform the same bending process, and crack detection was performed on the bending part of the panel to form a control group in order to determine the optimal groove depth / thickness ratio.

[0031] The configuration conditions for each experimental group are as follows: the panel is a 3mm paint-free board, the initial temperature is 25℃, the bending angle is 90°, and the experiment for each group with different infrared wavelengths is repeated 4 times. The detection value is based on the 4 parallel measurement values.

[0032] Comparison table of panel bending cracks at different groove depths

[0033] Groove depth / thickness ratio Measured trench depth (mean ± SD) Mean crack length (mean ± SD) Crack type Cross-sectional microscopic features 0.1 0.3±0.05 1.9±0.05 Surface radial microcracks Fiber breakage in unsoftened area 0.2 0.6±0.05 1.3±0.05 Surface radial microcracks Fiber breakage in unsoftened area 0.3 0.9±0.05 0.5±0.05 transverse cracks at the bottom of the tank Partial fiber plastic deformation 0.4 1.2±0.05 0.1±0.05 Localized pinpoint cracks Fibers are evenly stretched 0.5 1.5±0.05 0.1±0.05 Non-penetrating crack Complete plastic deformation 0.6 1.8±0.05 0.8±0.05 Longitudinal cracks at the bottom of the trench Partial fiber plastic deformation 0.7 2.1±0.05 1.6±0.05 Penetrating crack Shear fracture at the thin wall at the bottom of the trough

[0034] As shown in Table 1, when the groove depth / thickness ratio reaches 0.3~0.6, the panel bending point is in the plastic deformation stage, and its internal fiber structure is not easy to break, which can meet the requirement that the panel is not prone to cracking after grooving and bending.

[0035] Step 2: Inject molten high-temperature adhesive into the groove on the inside of the panel. The heat energy of the adhesive diffuses outward from the groove to the inner layer of the panel.

[0036] When the glue is injected into the groove, the molten glue flows to the bottom of the groove and fills it completely. Because the molten glue is at a high temperature, and the groove cuts open the inner layer of the panel, the high temperature of the glue can be quickly conducted through the groove surface to the inner layer area of ​​the panel, so that the inner layer area of ​​the panel is heated evenly and softened quickly.

[0037] It is worth noting that because the grooving creates a longitudinal groove depth in the inner layer of the panel, the thickness direction of the inner layer forms the groove depth direction. When the glue is injected into the groove, the molten glue will fill the groove depth, allowing the high-temperature glue to evenly contact the thickness direction of the inner layer. This allows the high temperature of the glue to be evenly conducted in the inner layer, reducing the temperature difference in the thickness direction when the inner layer softens due to heating.

[0038] Step 3: Simultaneously apply infrared radiation heating to the bend on the outer surface of the panel. The radiant heat energy is transferred from the outer side of the panel to the inner side of the panel, where it merges with the heat energy of the adhesive inside the bend of the panel to form an isothermal softening zone.

[0039] In the traditional wood door panel edge banding process, the wood doors used for sale need to have a decorative layer on their surface. Therefore, in the wood door panel bending process, melamine-faced boards are used as the panel. The outer surface of the melamine-faced board is a decorative surface, mainly composed of melamine-impregnated paper, which can form a decorative veneer and also has the characteristics of fireproof, moisture-proof and corrosion-resistant.

[0040] However, melamine-impregnated paper has a low glass transition temperature and a thermal decomposition temperature of only about 180-200℃. The wood substrate inside the melamine board needs to be above 150℃ to soften. This makes the temperature difference between the softening of the substrate and the decomposition of the veneer very small. Once the substrate is heated, if the temperature fluctuates, it can easily cause the outer veneer to decompose and crack.

[0041] Furthermore, the two have significantly different coefficients of thermal expansion; the CTE of melamine-impregnated paper is approximately 60 × 10⁻⁶. -6 / K, while the longitudinal CTE of the wood substrate is only 5×10 -6 / K. Therefore, when the surface of the melamine board is heated to 150℃, the expansion of the outer veneer is 12 times that of the inner wood substrate, which can easily cause the two to delaminate and the veneer to bubble.

[0042] Therefore, in the process of bending and sealing wooden door panels, when the traditional hot press is used to bend the panel to the side of the wooden door, the heat generated by the hot press will accumulate directly on the surface of the panel, resulting in uneven temperature transfer. This causes heat to accumulate on the surface of the panel and create temperature differences, which can easily cause the surface to yellow, crack, and bubble, thus affecting the overall quality of the wooden door.

[0043] To address the aforementioned issues, this embodiment employs infrared radiation heating to soften the outer layer of the panel, thereby reducing heat accumulation and uneven heating caused by direct heating.

[0044] By selecting different infrared wavelengths, different materials can be selectively penetrated. The infrared wavelengths penetrate the melamine layer of the veneer and are mostly absorbed by the internal wood substrate, thereby reducing the temperature rise of the veneer surface and accelerating the temperature rise of the substrate. This results in a lower veneer breakage rate and faster softening of the substrate. Furthermore, the infrared wavelengths diffuse evenly into the substrate, resulting in more uniform temperature conduction and smaller temperature variations.

[0045] In this embodiment, please refer to Tables 2 and 3. In order to test the optimal infrared wavelength for the melamine layer, infrared wavelengths of different lengths were used to heat the outer side of the panel for the same time, and the temperature of the panel finish layer and substrate layer was measured to form a control group to determine the optimal infrared wavelength.

[0046] The configuration conditions for each experimental group are as follows: heating time is set to 5s, surface layer thickness is 0.3mm melamine impregnated paper, substrate is 3mm high-density fiberboard, initial temperature is 25℃, infrared power is constant at 1.5 kW / m², and the experiment of each group with different infrared wavelengths is repeated 4 times, and the temperature detection is based on 4 parallel measurements.

[0047] Comparison of panel temperature rise for different infrared wavelengths

[0048] Infrared wavelength Finishing temperature (mean ± SD) Substrate layer temperature (mean ± SD) Temperature gradient 0μm 25±0.1 25±0.1 0 0.75μm 195±0.1 92±0.1 103±0.1 1.5μm 182±0.1 150±0.1 32±0.1 4μm 164±0.1 155±0.1 9±0.1 6μm 175±0.1 164±0.1 11±0.1 8μm 191±0.1 163±0.1 18±0.1 10μm 201±0.1 161±0.1 45±0.1 25μm 209±0.1 146±0.1 63±0.1 500μm 253±0.1 123±0.1 130±0.1

[0049] As shown in Table 2, when the infrared wavelength range reaches 1.5μm~8μm, that is, the mid-far infrared wavelength, the temperature of the decorative layer gradually decreases to below 200 degrees, and the temperature of the substrate layer gradually increases to above 150 degrees. Moreover, the temperature gradient change is small and tends to be stable, indicating that the heating effect of the panel material is sufficient within this infrared wavelength range.

[0050] Comparison of panel temperature rise for different infrared wavelengths

[0051] Infrared wavelength Finishing temperature (mean ± SD) Substrate layer temperature (mean ± SD) Temperature gradient 1.5μm 182±0.1 150±0.1 32±0.1 2μm 176±0.1 161±0.1 15±0.1 3μm 172±0.1 162±0.1 10±0.1 4μm 172±0.1 163±0.1 9±0.1 5μm 174±0.1 163±0.1 11±0.1 6μm 175±0.1 164±0.1 11±0.1 7μm 179±0.1 164±0.1 15±0.1 8μm 191±0.1 163±0.1 18±0.1

[0052] Within the infrared wavelength range of 1.5μm-8μm, the infrared wavelength range was further narrowed, resulting in the data in Table 2. Based on Table 3, it can be seen that when the infrared wavelength range reaches 3μm~6μm, the temperature of the decorative layer gradually decreases to around 170 degrees Celsius, which is below the thermal decomposition temperature of 180 degrees Celsius, while the temperature of the substrate layer gradually rises to around 160 degrees Celsius and begins to soften. Furthermore, the temperature gradient gradually stabilizes at a difference of 10 degrees Celsius, with the smallest variation range. This indicates that within this infrared wavelength range, the heating effect on the panel material is sufficient.

[0053] Infrared wavelengths in the 0.7μm-1.5μm range are near-infrared waves, which have shorter wavelengths and a penetration depth of 5–10mm. Their energy penetrates directly into the substrate layer of the panel. However, the surface layer, due to its low heat capacity and high absorption rate, is more prone to exceeding the thermal decomposition critical point (180℃), leading to damage. Infrared wavelengths above 6μm are far-infrared waves, which have longer wavelengths and a penetration depth of only 0.1–0.5mm. Their energy accumulates on the surface layer of the panel, causing rapid temperature rise and thermal decomposition, while the substrate layer heats up more slowly. When the infrared wavelength is in the 1.5μm-6μm range, the infrared wavelength matches the absorption peak of the wood substrate layer more closely. Energy is preferentially absorbed by the substrate, causing it to heat up rapidly, while the surface layer heats up more slowly. This results in a gentler heating gradient between the two, with a temperature difference of around 10℃, thus minimizing interfacial delamination stress.

[0054] In this embodiment, please refer to Table 4. In order to make the heat energy of the adhesive converge with the infrared heat energy on the inside and outside of the panel bending surface to form an isothermal softening zone and reduce the temperature gradient between the two, molten adhesives at different temperatures are injected into the groove of the panel, and the temperature of the middle part of the substrate layer of the panel is measured to form a control group to determine the optimal temperature for adhesive injection.

[0055] The configuration conditions for each experimental group are as follows: after injecting the glue, the time interval for each temperature measurement is set to 5 seconds, the substrate is 3mm high-density fiberboard, the initial temperature is 25℃, and the experiment of different glue temperatures in each group is repeated 4 times, and the temperature is measured based on 4 parallel measurements.

[0056] Comparison of the temperature rise of the panel substrate in the middle of the adhesive at different temperatures

[0057] Injection temperature (mean ± SD) 160±0.1 165±0.1 170±0.1 180±0.1 190±0.1 200±0.1 210±0.1 220±0.1 Substrate layer temperature (mean ± SD) 153±0.1 158±0.1 161±0.1 163±0.1 166±0.1 168±0.1 174±0.1 179±0.1

[0058] As shown in Table 4, when the glue is injected into the panel groove for 10 seconds, the glue temperature reaches 165~200℃, and the temperature in the middle of the substrate layer is about 160℃. At this time, the temperature (158~168℃) from the glue heat energy transferred from the inside of the panel to the middle of the substrate layer is small, which is similar to the temperature (162~164℃) from the infrared heat energy transferred from the outside of the panel to the middle of the substrate layer. This indicates that within this temperature range, the glue injected into the panel is sufficient to meet the heating effect of forming an isothermal softening layer in the panel.

[0059] Step 4: The heated and softened panel is passed through a gradient curvature guide plate at a uniform rate to perform gradient bending and shaping, with the bending angle continuously increasing from 0° to 90°.

[0060] As the panel passes through the gradient curvature guide plate, the grooved side panel of the panel is gradually bent towards the side of the wooden door by the gradually changing angle of the guide plate until the grooved side panel of the panel is bent and fits against the side of the wooden door. At this time, the glue in the groove of the panel will be reduced due to the bending of the panel and the compression of the groove space. The glue is squeezed into the inner side panel of the panel and contacts the side of the wooden door, providing adhesive force for the bonding surface. At this time, the grooved side panel of the panel forms a right angle with its original panel surface, and the bending angle is 90°.

[0061] During bending, the isothermal softening zone at the groove of the panel softens and gradually bends under the pressure of the guide plate. Because the temperature difference in the bending area is small, the fiber structure of the wood substrate softens and deforms without breaking, and it is not easy to accumulate internal stress. The outer decorative layer, on the other hand, does not reach the thermal decomposition temperature because its melamine layer still maintains its deformation characteristics and can be bent and deformed, making it less prone to cracking during bending.

[0062] Step 5: Press the edge of the bent panel to keep it under pressure during the glue curing process, thus completing the edge sealing of the wooden door.

[0063] The process involves using an extruder to press the entire bent panel, allowing sufficient time for the adhesive on the bonding surface to cool and cure before it is properly sealed to the wooden door. If no pressure is applied to the panel, there will be no force between the panel and the wooden door side after bending. At this point, the hot adhesive has not fully cooled down and is still in a molten state, resulting in low adhesion. This can easily cause the panel to separate from the wooden door side, creating gaps and resulting in a loose bond and poor sealing.

[0064] It is worth noting that the pressing time of the extruder on the panel should be longer than the time for the glue to cool and cure, reducing the occurrence of loose edges between the panel and the wooden door.

[0065] The various embodiments of the present invention have now been described in detail. To avoid obscuring the concept of the invention, some details known in the art have not been described. Those skilled in the art will fully understand how to implement the technical solutions of this invention based on the above description, and the scope of the invention is defined by the appended claims.

Claims

1. A process for directly bending and sealing the edges of wooden door panels, characterized in that: Step 1: Align the core board of the wooden door with the panel, and groove the inside of the panel where it is to be bent. Step 2: Inject molten high-temperature adhesive into the groove on the inside of the panel. The heat energy of the adhesive diffuses from the groove on the panel outward to the inner layer of the panel. Step 3: Simultaneously apply infrared radiation heating to the bend on the outer surface of the panel. The radiant heat energy is transferred from the outer side of the panel to the inner side of the panel, penetrates the outer decorative layer of the panel, and merges with the glue heat energy inside the bend of the panel to form an isothermal softening zone. Step 4: The heated and softened panel is passed through a gradient curvature guide plate at a uniform rate to perform gradient bending and shaping, with the bending angle continuously increasing from 0° to 90°. Step 5: Press the edge of the bent panel to provide pressure for the adhesive to cure during the curing process, thus completing the edge sealing of the wooden door core board.

2. The direct bending and edge-sealing process for wooden door panels according to claim 1, characterized in that, The ratio of the groove depth to the panel thickness is within the range of 0.3 to 0.

6.

3. The direct bending and edge-sealing process for wooden door panels according to claim 1, characterized in that, The infrared wavelength range during infrared radiation heating is within 3μm~6μm.

4. The direct bending and edge-sealing process for wooden door panels according to claim 1, characterized in that, The injection temperature range of the molten high-temperature adhesive is within 165~200℃.

5. The direct bending and edge-sealing process for wooden door panels according to claim 1, characterized in that, The extrusion time of the panel sealing surface is longer than the cooling and curing time of the molten high-temperature adhesive.