A method for suppressing occurrence of print defects in a laser printer and an application

Abstract

The application relates to the technical field of laser printing, in particular to a method for inhibiting the generation of printing defective products of a laser printer and application, which comprises the following steps: printing a front layer on a first surface of a substrate, extracting printing coordinates of the front layer, and establishing a complement area; configuring a supporting tool and performing first sintering on the front layer, and controlling the force points of the supporting tool to only act on a projection range of the corresponding complement area on a second surface of the substrate; after the first sintering, controlling the substrate to cool down; printing a rear layer on the second surface of the substrate, configuring an auxiliary mechanism and performing second sintering on the rear layer, controlling the auxiliary mechanism to avoid the front layer, and restraining the supporting points of the auxiliary mechanism to the complement area on the first surface; and configuring a control unit, which blocks the heat on the first surface from escaping and conducting to the second surface. The application can inhibit the micro thermal resistance distortion and the out-of-control back heat flow dissipation, so as to stabilize the dynamic temperature field of the shadow contact surface.

Description

Technical Field

[0001] This application relates to the field of laser printing technology, and in particular to a method and application for suppressing the occurrence of defective prints by laser printers. Background Technology

[0002] With the widespread adoption of office automation technology, laser printers play an indispensable role in various high-speed graphic output scenarios. In the entire laser printing process, the fusing stage is the core step that determines the final image quality. When performing high-speed fusing operations, the internal heating element of the printer typically needs to be maintained within a critical high-temperature range of 180°C to 200°C. Under this dynamic working environment, room-temperature paper and cold toner continuously glide across the contact surface of the fusing element at extremely high relative speeds. This intense physical contact generates a significant transient heat dissipation effect. This necessitates that the core fusing component possess extremely high structural stability and highly uniform surface heat conduction to counteract this heat dissipation and ensure that the toner is fully melted.

[0003] To address print quality fluctuations under complex operating conditions, existing conventional technologies often focus on external intervention at the macroscopic system control algorithm level. For example, patent CN113341668B discloses a laser printer with adaptive print quality adjustment based on printing substrate detection. This solution integrates a substrate detector within the printer to acquire physical parameters such as paper type, thickness, and roughness in real time. These parameters are then processed and analyzed by a controller, which dynamically adjusts parameters such as photosensitive drum voltage, fixing temperature, and fixing pressure using commands. This closed-loop detection-based adaptive parameter adjustment mechanism can, to some extent, compensate for uneven toner adsorption or penetration caused by differences in paper material, attempting to maintain a relatively ideal imaging effect through adjustments in global operating temperature and pressure.

[0004] However, this technology, which relies on peripheral system-level compensation, gradually exposes its technical blind spots in the underlying physical structure when faced with extreme scenarios such as continuous, high-speed, transient thermal shocks. Specifically, during the traditional high-temperature sintering process, the multi-layered structure of the fixing heating component inevitably experiences macroscopic physical interference from the supporting fixtures while the coating is in a softened state. This results in microscopic pits or localized thinning and peeling within the coating. Consequently, when the component is powered on, discrete microscopic thermal resistance abrupt distortion zones form on the contact surface, creating localized hot and cold spots. Simultaneously, during high-speed continuous fixing, the rapidly passing cold paper causes a sharp temperature drop on the front side of the component. Due to the inherent bidirectional thermal conductivity of the alumina ceramic substrate, the critical heat urgently needed on the front side escapes irreversibly along the large thermodynamic temperature gradient to the lower, isothermal back side. This localized uneven heating caused by microscopic thermal resistance distortion is viciously coupled with the severe loss of heat flow at the macroscopic level, directly leading to the complete collapse of the dynamic temperature field at the fixing contact surface. At this point, simply relying on existing technology to increase the overall fixing temperature is insufficient to repair the fragmented heat distribution on the contact surface, inevitably leading to fatal product defects such as printing ghosting, blurred text, and poor fixing during continuous operation. Summary of the Invention

[0005] In order to suppress microscopic thermal resistance distortion and uncontrolled back heat dissipation, thereby stabilizing the dynamic temperature field of the fixed-image contact surface, this application provides a method and application for suppressing the occurrence of defective products printed by laser printers.

[0006] Firstly, this application provides a method for suppressing the occurrence of defective printed products by a laser printer, which adopts the following technical solution: A method for suppressing the occurrence of defective printed products by a laser printer includes: A front layer containing a front heating element is printed on the first surface of the substrate. The printing coordinates of the front layer are extracted, and the area on the first surface of the substrate corresponding to the area outside the printing coordinates is established as the complement area. Configure a support fixture and perform a first sintering on the front layer, controlling the force point of the support fixture to act only on the projection range of the supplementary area on the second surface of the substrate; After the first sintering, the substrate is controlled to cool down to release thermal stress; A rear layer containing a rear heating element is printed on the second surface of the substrate. An auxiliary mechanism is configured and a second sintering is performed on the rear layer. The auxiliary mechanism is controlled to avoid the front layer and its support point is constrained to the supplementary area on the first surface. A control unit is configured to connect to the front heating element and the rear heating element. The control unit is configured to control the front heating element to heat up to a preset fixing working temperature in response to a fixing command, and simultaneously control the rear heating element to heat up, so as to construct a temperature boundary matching the fixing working temperature on the second surface, eliminate the temperature gradient between the first surface and the second surface, and block the escape conduction of heat from the first surface to the second surface.

[0007] Optionally, the step of printing a pre-heating layer containing a pre-heating element on the first surface of the substrate, extracting the printing coordinates of the pre-heating layer, establishing the area on the first surface of the substrate corresponding to the area outside the printing coordinates as a supplementary area, configuring a support fixture and performing a first sintering on the pre-heating layer, and controlling the force point of the support fixture to act only within the projection range of the supplementary area on the second surface of the substrate, includes: A first conductor layer, a positive heating element layer serving as the front heating element, a temperature measuring layer, and a front glass layer are sequentially printed on the first surface to construct the front layer; Extract the joint printed coordinates of the first conductor layer, the positive heating element layer, the temperature measuring layer and the front glass layer, and establish the area on the first surface of the substrate that corresponds to the area outside the joint printed coordinates as the complement region; During the first sintering of the front layer to solidify the front glass layer, the force point of the support fixture is controlled to be locked within the projection range of the supplementary area on the second surface of the substrate, maintaining spatial avoidance and non-contact constraint for the joint printing coordinates.

[0008] Optionally, controlling the substrate to cool down to release thermal stress after the first sintering includes: After the first sintering of the front layer is completed, the step of printing the back layer on the second surface is blocked. Allow the substrate to cool down naturally; In response to the temperature of the substrate dropping to a preset room temperature threshold, the step of printing the back layer on the second surface is unlocked.

[0009] Optionally, allowing the substrate to cool down naturally includes: Cut off the external forced cooling source to maintain a cooling environment without external thermal intervention; The thermal stress accumulated on the substrate due to the first sintering is released in the cooling environment; After releasing the thermal stress, the relative spatial coordinates of the front layer and the supplementary area are locked, and the locked relative spatial coordinates are extracted as a physical avoidance reference, so that the support point of the auxiliary mechanism can be constrained to the supplementary area on the first surface by using the physical avoidance reference during the second sintering.

[0010] Optionally, the rear layer includes a second conductor layer, a heat-reflecting element layer, a rear temperature sensing layer, and a rear glass layer, wherein the heat-reflecting element layer serves as the rear heat-reflecting element; The step of printing a rear layer containing a rear heating element on the second surface of the substrate, configuring an auxiliary mechanism and performing a second sintering on the rear layer, controlling the auxiliary mechanism to avoid the front layer, and constraining its support points to the supplementary area on the first surface includes: The second conductor layer, the heat-conducting element layer, the rear temperature sensing layer, and the rear glass layer are sequentially printed on the second surface of the substrate; Extract the physical avoidance benchmark and map it as a three-dimensional spatial avoidance boundary for the auxiliary mechanism; During the second sintering process, the auxiliary mechanism is used to avoid boundary constraints in the three-dimensional space, positioning its support point in the supplementary area on the first surface and avoiding physical contact with the pre-layer, so as to solidify the post-glass layer.

[0011] Optionally, eliminating the temperature gradient between the first surface and the second surface includes: The rear glass layer, which is solidified on the outermost side of the second surface, is configured as a heat-insulating layer with a thermal conductivity less than a preset blocking threshold. The heat-insulating layer is used to limit the heat transfer path lost to the external space via the second surface; The same temperature boundary and the heat-insulating layer work together to suppress the physical channels through which heat is lost from the second surface, and force the heat generated by the front heating element to be output unidirectionally to the first surface side.

[0012] Optionally, the control unit is configured to synchronously control the heating of the rear heating element to construct a isothermal boundary on the second surface that matches the fixing operating temperature, including: The control unit is configured to acquire the actual heating temperatures of the front heating element and the rear heating element, respectively. The control unit is configured to adjust the operating power input to the rear heating element according to the preset fixing working temperature, and perform closed-loop feedback based on the actual heating temperature of the rear heating element to control the heating temperature of the rear heating element to be stable at the fixing working temperature. By utilizing the stabilized heating temperature, a constant isothermal boundary is constructed on the second surface, which, together with the heat-insulating layer, continuously eliminates the temperature gradient and blocks the backflow of heat.

[0013] Optionally, the synergistic effect of the heat-insulating layer in continuously eliminating the temperature gradient and blocking heat loss in the reverse direction includes: When the front layer experiences a transient temperature drop due to the high-speed passing of the paper, the rear heating element maintains a stable heating temperature to preserve the same temperature boundary on the second surface. The same temperature boundary is used to reverse the temperature gradient across the substrate, weakening and blocking the thermal conduction force transferred to the second surface; The heat-insulating layer works together to suppress heat loss to the external environment, forces the heat stored in the rear heating element to be directionally replenished to the first surface, and clamps the transient temperature drop of the front layer within a preset amplitude range.

[0014] Optionally, before configuring the control unit, the following may also be included: A planarization process is performed on the first surface of the substrate to optimize the microscopic flatness of the surface of the front layer, and the surface flatness of the front layer is constrained within a preset tolerance threshold. The supplementary area is extracted as the mounting reference, and when fixing the substrate, the supporting force of the external components is constrained to act only on the mounting reference; Using the installation reference, the front layer is spatially physically avoided, and the front layer, which reaches the preset tolerance threshold, is constructed to form a heat transfer interface without structural obstruction, so that the fixing heat generated by the front heating element can be conducted to the outside through the heat transfer interface.

[0015] Secondly, the application of the method for suppressing the occurrence of defective printed products in laser printers in the fixing operation of laser printers, as provided in this application, adopts the following technical solution: The application of the method for suppressing the occurrence of defective printed products in laser printers in the fixing operation of laser printers includes: The substrate prepared by the method is assembled into the fixing assembly, such that the first surface of the substrate abuts against the fixing belt of the fixing assembly. The fixing command is input to the control unit to trigger the heating of the front heating element and the rear heating element, thereby constructing the same temperature boundary and eliminating the temperature gradient between the first surface and the second surface; After the heating temperature reaches the preset fixing working temperature, the printing medium with toner attached is driven to move along the first surface with the fixing belt. The heat generated by the preheating element is conducted to the printing medium via the first surface and the fixing belt, causing the toner to melt and solidify on the surface of the printing medium.

[0016] In summary, this application includes the following beneficial technical effects: 1. This application constructs a non-contact sintering process based on three-dimensional spatial physical mapping avoidance, controlling the force point of the support fixture to act only within the projection range of the corresponding supplementary area on the second surface of the substrate, and using physical avoidance reference to constrain the support point of the auxiliary mechanism to the supplementary area of ​​the first surface during the second sintering, completely avoiding the macroscopic physical interference of the support fixture on the softened glass layer during high-temperature sintering, eliminating the local hot and cold spot problem caused by microscopic thermal resistance distortion from the physical manufacturing root, ensuring that the thermal resistance distribution consistency deviation after the pre-layer sintering is less than or equal to 2%, thereby effectively suppressing the occurrence of defective products printed by laser printers.

[0017] 2. This application configures a control unit connected to the front heating element and the rear heating element to synchronously control the rear heating element to heat up to the same fixing operating temperature as the front heating element in response to the fixing command. This creates a temperature boundary on the second surface of the substrate that matches the fixing operating temperature, eliminating the temperature gradient between the first and second surfaces. In conjunction with a heat-insulating layer on the outermost side of the second surface with a thermal conductivity less than a preset blocking threshold, the physical path of heat generated by the front heating element escaping to the second surface is completely cut off, forcing heat to be output unidirectionally to the first surface side, thus stabilizing the dynamic temperature field of the fixing contact surface.

[0018] 3. This application achieves positive synergy between the uniform thermal resistance distribution of the front layer and the extremely stable dynamic temperature field under the constraint of the same temperature boundary. When the front layer experiences a transient temperature drop due to the high-speed passing of cold paper, the constant same temperature boundary maintained by the rear heating element instantaneously reverses the temperature gradient across the substrate, forcing the heat stored in the rear heating element to be directionally replenished to the first surface. This precisely clamps the transient temperature drop of the front layer within a preset amplitude range, reducing the printing defect rate of the laser printer during continuous high-speed operation to below 1%, while increasing the production yield of the heating component to over 97%. Attached Figure Description

[0019] Figure 1 This is a logical flowchart of the method in the embodiments of this application; Figure 2 This is a top view of the structural distribution of the joint printing area and the supplementary area of ​​the substrate front layer in an embodiment of this application; Figure 3 This is a schematic diagram of the non-contact support assembly section during the first sintering process of the pre-layer in an embodiment of this application; Figure 4 This is a schematic diagram of the three-dimensional spatial avoidance support section when the post-layer performs the second sintering process in the embodiment of this application; Figure 5 This is a diagram comparing the underlying heat flow distribution of traditional single-sided heating technology with the same-temperature boundary heat flow directional control mechanism of this application. Figure 6 This is a schematic diagram illustrating the principle of directional heat replenishment in the event of transient thermal shock generated when a cold medium passes by at high speed, according to an embodiment of this application. Detailed Implementation

[0020] The following combination Figures 1-6 This application will be described in further detail.

[0021] like Figure 1 As shown in the figure, this application discloses a method for suppressing the occurrence of defective products printed by laser printers. It employs a technical solution that combines a non-destructive process based on three-dimensional spatial physical mapping avoidance with heat flow directional control based on dynamic isothermal boundaries. This eliminates the conditions for the generation of microscopic thermal resistance distortion, cuts off the physical path of backflow heat escape, and simultaneously achieves a logical closed loop in the process through reference latching, stably maintaining the dynamic temperature field of the fixing contact surface and suppressing the occurrence of defective products printed by laser printers. The following describes the steps in detail: S1 substrate pretreatment and global positioning reference construction S11 substrate selection and basic parameter control The production equipment first selects an alumina ceramic substrate as the processing base, and then controls the thickness of the substrate within the range of 0.6mm to 1.2mm. Alumina ceramic itself has stable high thermal conductivity. When the thickness is less than 0.6mm, the structural rigidity of the substrate is insufficient under high-temperature sintering conditions, and it is very easy to warp and deform, and the dimensional tolerance cannot meet the requirements of subsequent precision printing. When the thickness is greater than 1.2mm, the heat capacity and thermal resistance of the substrate are significantly increased, resulting in excessive thermal inertia of the system as a whole. This will not only slow down the initial preheating speed when the equipment is turned on, but also seriously hinder the rapid dynamic establishment of the same temperature boundary on both sides, making it impossible to match the transient temperature control requirements in high-speed printing scenarios. At the same time, this thickness range is also fully compatible with the standardized installation space of the fuser assembly of mainstream laser printers on the market.

[0022] S12 substrate double-sided planarization pretreatment The production equipment performs double-sided planarization pretreatment on the selected alumina ceramic substrate, followed by double-sided synchronous chemical mechanical polishing. During polishing, a silica polishing slurry with a particle size of 50nm to 100nm is used, the polishing pressure is controlled at 1psi to 2psi, and the polishing disc speed is controlled at 30rpm to 50rpm. After processing, the surface roughness of both sides of the substrate is controlled to Ra≤0.2μm, and the flatness of both sides is controlled to ≤0.01mm / 100mm. The accuracy of the ink transfer in screen printing directly depends on the uniform adhesion between the substrate and the printing screen. When the substrate surface roughness exceeds Ra 0.2μm, the printing ink will accumulate or be missed in the micro-depressions on the surface, directly causing the thickness uniformity of the printed layer to exceed the controllable range. When the substrate flatness exceeds 0.01mm / 100mm, the printing screen and the substrate surface cannot form a uniform adhesion gap, resulting in localized printing thickness deviations. Meanwhile, the double-sided synchronous polishing process ensures that the shape and position references of the front and back sides of the substrate are completely consistent, avoiding the problem of reference misalignment during subsequent flipping and printing.

[0023] S13 Global Positioning Benchmark Establishment and Accuracy Verification The production equipment establishes a global positioning reference on the first surface of the substrate using a high-precision vision positioning system. The global positioning reference adopts a cross-shaped mark. The production equipment prints the cross-shaped mark on the diagonal edge area of ​​the first surface of the substrate using a 325-mesh polyester screen printing process. After the mark is printed, it is dried and cured. The drying temperature is controlled between 120℃ and 150℃, the drying time is controlled between 10 minutes and 15 minutes, and the drying air volume is controlled between 0.5m / s and 1m / s to ensure that the mark will not wear off or fall off during the entire process.

[0024] The production equipment then uses a vision positioning system to verify the accuracy of the markings, controlling the shape and position accuracy of the markings to ≤±0.01mm. The vision positioning system used in conjunction with this system has a resolution of ≥4800dpi. This global positioning reference serves as the unified coordinate origin for all subsequent printing processes, coordinate extraction, and tooling positioning. If the shape and position accuracy of the markings exceeds ±0.01mm, subsequent processes will experience cumulative coordinate deviations, directly resulting in insufficient clearance between the tooling support points and the printing area, thus failing to effectively protect the printed layer. On the other hand, a collection resolution of 4800dpi or higher means that the size of a single physical pixel (approximately 0.0053mm) is far smaller than the 0.01mm tolerance requirement. This ensures, from a physical perspective, that the vision positioning system can accurately identify the boundaries of subsequent printed graphics, meeting the stringent accuracy requirements for establishing the supplementary area and ensuring that the positioning accuracy of each process remains consistent throughout the entire manufacturing process.

[0025] S2 Pre-layer Printing and Complementary Area Establishment S21 Pre-layer layer printing and drying / curing The production equipment first uses the global positioning reference established and verified by S13 as the unique coordinate origin, and then sequentially prints the first conductor layer, the positive heating element layer, the temperature measuring layer and the front glass layer on the first surface of the substrate to build a complete front layer structure.

[0026] The production equipment uses screen printing technology to complete the printing of each layer. The first conductor layer uses a 300-325 mesh screen and silver-palladium conductive paste. The printing thickness is controlled between 8μm and 12μm. This thickness range can ensure the current carrying capacity of the conductive circuit without forming too high a step on the substrate surface, which would affect the flat coverage of the subsequent glass layer.

[0027] The positive heating element layer, as the preheating element, is the core heating unit in the fixing process. It uses a 250-300 mesh screen and ruthenium-based resistive paste, with the printing thickness controlled at 10μm to 15μm to ensure the stability and consistency of the heating characteristics, providing a uniform heat source foundation for subsequent fixing processes.

[0028] Next, in order to accurately collect the dynamic working temperature, the production equipment uses a thick film thermistor without protrusions directly printed from the thermistor paste as the temperature measuring layer. It is placed in the main working contact surface of the fixing belt and is physically isolated from the positive heating element layer to avoid electrical short circuit.

[0029] The final pre-glass layer uses 180-200 mesh screen and crystalline borosilicate glass paste, with a printing thickness controlled between 35μm and 45μm. It completely covers the non-electrode areas of the positive heating element layer, temperature sensing layer, and first conductor layer, providing reliable insulation protection for the internal printed layers and forming a smooth fixing heat transfer interface.

[0030] After each printing layer is completed, the production equipment immediately sends the material into a hot air drying oven for drying. The drying temperature is controlled between 120℃ and 150℃, the drying time is controlled between 10 minutes and 15 minutes, and the drying airflow is controlled between 0.5 m / s and 1 m / s. This combination of temperature, time, and airflow parameters can effectively remove the organic carrier inside the paste, avoiding defects such as pinholes and bubbles inside the printed layer during subsequent sintering, while also preventing the paste from undergoing a pre-curing reaction, thus ensuring good adhesion between adjacent printed layers.

[0031] S22 Joint Printing Coordinate Acquisition and Accuracy Verification After the printing and drying of the entire front layer structure is completed, the production equipment uses the high-precision visual positioning system configured in S13 to collect the joint printing coordinates of the first conductor layer, the positive heating element layer, the temperature measuring layer and the front glass layer, with the collection accuracy controlled within ≤±0.02mm.

[0032] The joint printing coordinates here refer to the outer contour boundary coordinates of all structural pastes in the front layer printed on the first surface of the substrate. It can completely cover all printed areas of the front layer that have electrical, temperature measurement and insulation functions, ensuring that no coverage boundary is missed.

[0033] After data acquisition, the production equipment simultaneously performs accuracy verification, comparing the acquired actual coordinate data with the theoretical design coordinates generated based on the global positioning benchmark, and controlling the overall deviation within ≤±0.02mm. This accuracy threshold is set by combining the resolution of the visual positioning system with the minimum safe avoidance distance of the printing area, ensuring that the recognition error of the printed graphic boundary is completely within a controllable range. This not only avoids missed or misjudged functional area boundaries but also provides an extremely reliable coordinate basis for the accurate division of subsequent supplementary areas.

[0034] S23 Complementary Region Establishment and Boundary Consolidation After the acquisition and verification of the joint printing coordinates are completed, the production equipment then uses the verified joint printing coordinates as the absolute boundary to establish the unprinted exposed area on the substrate outside the corresponding joint printing coordinates as the supplementary area.

[0035] Figure 2 The physical boundary between the "pre-layer joint printing functional area" on the first surface of the substrate and the surrounding unprinted "supplement area" is defined, and a supplement margin of ≥4.5mm in width and a cross-shaped global positioning reference are specially marked. That is, this application has reserved an absolutely sufficient safety margin for subsequent high-temperature support tooling from the early spatial division.

[0036] The production equipment precisely controls the minimum width of the supplementary area to ≥4.5mm. This width threshold ensures that there is sufficient physical space in the area to accommodate the geometric dimensions of the support structure in subsequent processes, adapts to the minimum installation size of the support structure, and avoids stress concentration or even breakage of the substrate under high temperature conditions. On the other hand, it also takes into account the size of the support structure to fully cover the amount of thermal expansion at high temperatures and the necessary safety clearance distance, thus defining a clear boundary between the printed functional area and the non-functional support area from the root.

[0037] After the supplementary area is established, the production equipment uses a vision positioning system to bind and solidify the boundary coordinates of the supplementary area with the global positioning reference established in S13. This ensures that the boundary of this area maintains a unique and stable coordinate mapping relationship throughout the entire process. Not only will the reference shift not occur due to process flow, but it also provides a clear boundary basis for the positioning of the support tooling in the subsequent sintering process.

[0038] S3 Pre-layer First Sintering and Non-Contact Process Control S31 High Temperature Resistant Support Fixture Configuration and Coordinate Mapping The production equipment first establishes and completes the boundary solidification of the supplementary collection area based on S23, and then configures a suitable high-temperature resistant support fixture. The support fixture is made of alumina ceramic of the same material as the substrate, with a temperature resistance of ≥1000℃, and its thermal expansion coefficient is completely matched with that of the substrate. This can avoid relative displacement caused by thermal expansion differences during high-temperature sintering, and it is also fully compatible with the full-temperature range operation requirements of the sintering furnace.

[0039] The support fixture is equipped with an array of support bosses. The coordinates of the bosses are perfectly mapped to the contour coordinates of the supplementary area, and are simultaneously bound and calibrated with the global positioning reference established in S13. The flatness of the top surface of the bosses is controlled to ≤0.01mm / 100mm, and the contact area of ​​a single boss is ≥4mm². This parameter design avoids stress concentration on the substrate caused by an excessively small contact area of ​​a single boss, and does not occupy too much reserved space in the supplementary area, thus ensuring both the stability and uniform stress distribution of the substrate support.

[0040] S32 Spatial Position Verification and Substrate Loading After configuring and mapping the support fixture, the production equipment uses the high-precision vision positioning system configured in S13 to perform spatial position verification before substrate loading. During the verification process, the production equipment checks the force points of all bosses on the support fixture one by one, ensuring that they fall completely within the projection range of the corresponding supplementary area on the second surface of the substrate, and that the minimum clearance distance between the edge of the boss and the corresponding projected joint printing coordinate must be ≥1.5mm. Although the substrate and the support fixture are both made of alumina ceramic and have matching coefficients of thermal expansion, slight transient temperature differences and relative thermal slip deformation are still inevitable during the dynamic process of sintering heating and cooling due to the slight differences in their volume and heated surfaces. At the same time, the printing paste also exhibits a certain degree of edge flow when softening at high temperatures. The 1.5mm clearance distance, combined with the minimum width of the supplementary area of ​​≥4.5mm, provides an extremely sufficient safety margin to absorb such dynamic thermal deformation and mechanical assembly errors.

[0041] After the verification is passed, the production equipment then performs the substrate loading operation, placing the first surface of the substrate face up on the top surface of the support boss. At this time, the contact point between the bottom support boss and the second surface of the substrate falls completely within the projection range of the supplementary area.

[0042] Figure 3 The assembly state of the first sintering process was deeply restored from a cross-sectional perspective: the boss of the bottom support fixture was precisely applied to the projection range of the "complementary area" on the second surface of the substrate, so that the front layer that carries the heat-generating core was completely "suspended" (avoidance distance ≥1.5mm). This confirms the non-destructive manufacturing mechanism of this process to avoid interference from local cold ends or mechanical top cutting of the softened glass layer. Finally, it was confirmed that there was no warping or offset after the substrate was placed.

[0043] S33 First Sintering Process Parameter Control and Execution After substrate loading is completed, the production equipment then feeds the loaded substrate into a mesh belt sintering furnace to perform the first sintering process. This involves high-temperature sintering to solidify the pre-glass layer, achieving densification. The production equipment sets the peak sintering temperature to 850℃, which is the optimal co-firing temperature for the silver-palladium conductive paste, ruthenium-based resistive paste, thermistor paste, and crystalline borosilicate glass paste. At this temperature, the conductive paste, resistive paste, and thermistor paste can respectively form a stable conductive network, uniform heating characteristics, and precise temperature sensing characteristics. Simultaneously, the crystalline borosilicate glass paste precipitates a microcrystalline phase during densification sintering, significantly increasing its secondary softening point and forming excellent interfacial adhesion with the alumina ceramic substrate, preventing interlayer delamination defects.

[0044] The production equipment controls the total sintering time to between 45 and 60 minutes, with strictly matched parameters for the heating, holding, and cooling stages. Crucially, throughout the holding sintering process, the equipment maintains a sufficient air supply to the furnace to sustain the oxidizing sintering atmosphere. This not only promotes the complete combustion and removal of the organic carrier in the slurry but is also an absolutely essential condition for ensuring the stable molding of the metal oxides in the ruthenium-based resistor slurry and thermistor slurry, guaranteeing reliable electrical properties. This completely avoids severe electrical degradation under oxygen-deficient reducing conditions, ensuring the long-term stability of its heating and temperature-sensing performance.

[0045] S34 Full-Process Non-Contact Constraint and Sintering Status Control Throughout the first sintering process, the production equipment continuously locks the force points of the support fixture. Since the bottom support bosses only act on the projection range of the corresponding supplementary area on the second surface of the substrate, the substrate area directly below the pre-layer is completely suspended within the sintering furnace. This bottom suspension avoidance mechanism is crucial; it prevents the large heat capacity of the support fixture from contacting the bottom of the heating zone during sintering, thus avoiding the formation of localized cold ends and ensuring that the positive heating element layer can form an extremely uniform conductive network during densification.

[0046] At the same time, this non-contact constraint, combined with the sintering posture with the first surface facing upwards, avoids the risk of sagging distortion of the softened glass layer due to gravity, ensuring uniform macroscopic flatness of the surface after the pre-layer is sintered, and a thermal resistance distribution consistency deviation of ≤±2%. This control effect directly solves the problem of local hot and cold spots caused by microscopic thermal resistance distortion due to macroscopic physical interference from the root of physical manufacturing.

[0047] S4 substrate thermal stress release and physical avoidance reference latch S41 Process Access Control and Cooling Environment Construction After the first sintering of the pre-layer and subsequent cooling to below 100°C in the furnace, the production equipment immediately blocks the printing process of the second surface layer of the substrate, preventing substrates that have not completed stress release from directly entering the subsequent printing stages. Simultaneously, the production equipment cuts off all external forced cooling sources, including the supporting air-cooling and water-cooling devices, and then smoothly transfers the substrate to a dust-free, temperature-controlled environment, establishing a natural cooling environment without external thermal intervention. The production equipment stably controls the ambient temperature at 25°C ± 2°C and the ambient wind speed at ≤0.2 m / s. This wind speed threshold avoids uneven convective heat transfer on the substrate surface, prevents excessive temperature difference between the substrate edge and center from generating new internal stress, and the gentle cooling environment also prevents micro-cracks from appearing at the interface between the pre-layer and the substrate due to rapid cooling, ensuring the bonding stability of the multilayer structure.

[0048] S42 Real-time Temperature Monitoring and Thermal Stress Relief Control During the natural cooling process, the production equipment continuously monitors the overall real-time temperature of the substrate using a high-precision infrared thermometer at a frequency of ≥1Hz, fully recording the entire cooling curve of the substrate. As the substrate slowly cools, it gradually releases the thermal stress accumulated during the first sintering process due to high-temperature expansion and low-temperature contraction. The production equipment's preset room temperature threshold is 25℃±2℃, consistent with the cooling environment temperature. At this temperature, the substrate's thermal expansion and contraction deformation is fully recovered, with dimensional and positional tolerance fluctuations ≤0.005mm, providing a stable dimensional and positional reference for subsequent processes.

[0049] When the real-time temperature of the substrate drops to within the room temperature threshold range and the temperature fluctuation within 5 minutes is ≤ ±0.5℃, the production equipment determines that the thermal stress release of the substrate is complete. At this time, the residual thermal stress inside the substrate is fully released, which can effectively prevent the substrate from warping and deformation in subsequent processes, and ensure the positioning accuracy of subsequent printing and sintering. The production equipment simultaneously unlocks the process permission for printing the second surface post-layer of the substrate.

[0050] S43 Relative Coordinate Acquisition and Physical Avoidance Reference Latching After the substrate has naturally cooled to the preset room temperature threshold and the thermal stress has been released, the production equipment uses the high-precision visual positioning system configured in S13 to re-acquire the relative spatial coordinates of the supplementary area and the printed functional area of ​​the front layer on the first surface of the substrate, with the global positioning reference as the coordinate origin. The acquisition accuracy is controlled within ≤±0.01mm. Since the dimensions and geometric tolerances of the substrate are completely stable at this time, the relative spatial coordinates acquired in this stage can truly reflect the actual static structural distribution of the first surface of the substrate, avoiding coordinate deviations that may be caused by dynamic deformation during sintering and cooling.

[0051] The production equipment locks the collected and verified relative spatial coordinates as the physical avoidance benchmark. This benchmark will serve as the sole basis for the spatial positioning of all supporting structures in subsequent processes, ensuring the accuracy and consistency of spatial avoidance from the source, preventing accidental physical damage to the precision structure that has already been formed in the previous layer, and providing a precise positioning basis for spatial avoidance in subsequent reverse processes.

[0052] S5 Post-Layer Printing and Second Sintering Cross-Surface Avoidance Control S51 Process Access Unlocking and Post-Layer Layer Printing and Drying After the production equipment completes the latching of the physical avoidance reference in S43, it first flips the substrate so that the second surface of the substrate faces upward, and then immediately performs the printing operation of the rear layer on the second surface of the substrate. The second surface of the substrate is a non-fixing working surface opposite to the first surface. The production equipment then uses the global positioning reference established in S13 as the origin of the mirror coordinates to sequentially print the second conductor layer, the anti-heating element layer, the rear temperature sensing layer, and the rear glass layer on the second surface of the substrate, ensuring that the center projections of the printing areas on both sides are completely coincident. Among them, the second conductor layer uses the same 300-325 mesh screen and silver-palladium conductive paste as the first conductor layer, and the printing thickness is controlled between 8μm and 12μm to construct a stable power supply circuit for the rear heating element.

[0053] The reverse heating element layer, as the rear heating element, uses a 250-300 mesh screen and ruthenium-based resistive paste that are exactly the same as the positive heating element layer. Its printing thickness is strictly controlled within the range of 10μm to 15μm, so that the sheet resistance and heating characteristics of the heating elements on both sides can achieve a high degree of physical matching.

[0054] Next, the production equipment uses thermistor paste to print a thick-film thermistor without protrusions as a back-end temperature sensing layer for subsequent dynamic temperature measurement. Finally, the back-end glass layer uses 180-200 mesh screen printing and borosilicate glass paste, with the printing thickness controlled at 30μm to 40μm, completely covering all the underlying layers. This continuous and dense coating of over 30μm effectively provides sufficient structural support for the subsequent heat insulation and temperature locking effects. After each layer is printed, the production equipment immediately sends it into a hot air drying oven for drying.

[0055] S52 Physical Avoidance Baseline Mapping and 3D Spatial Avoidance Boundary Construction After the printing and drying of the finishing layer, the production equipment extracts the physical avoidance reference locked by S43, and uses the global positioning reference as the origin of spatial transformation to accurately map the front planar coordinate reference into a three-dimensional spatial avoidance boundary for the auxiliary mechanism.

[0056] The production equipment uses the joint printing coordinate contour of the pre-layer as the XY plane no-entry boundary in the physical avoidance benchmark, and the maximum thickness of the pre-layer after sintering and curing as the height constraint on the Z axis, to construct a complete closed no-entry space region, clearly defining that all components of the auxiliary mechanism must not enter this region. The construction of this three-dimensional boundary breaks through the limitation of only planar avoidance in traditional processes, and can simultaneously cover the form and position tolerance fluctuations in the planar direction of the substrate and the structural protrusions in the thickness direction. This means that the auxiliary mechanism can only move within the supplementary area, thereby completely avoiding the risk of physical contact and damage to the precision structure of the pre-layer already formed during the reverse sintering process from a spatial dimension.

[0057] S53 Auxiliary Support Mechanism Configuration and Positioning Verification Loading After constructing the three-dimensional spatial avoidance boundary, the production equipment then configures a suitable auxiliary support mechanism based on this boundary. The auxiliary mechanism is also made of alumina ceramic, the same material as the substrate, and its thermal expansion coefficient perfectly matches that of the substrate. The auxiliary mechanism is simultaneously configured with an edge stepped limiting structure and an array of support pins. The production equipment sets the tip diameter of the support pins to ≥2.5mm to ensure that the contact area of ​​a single pin is ≥4.9mm², avoiding localized stress concentration due to an insufficient contact area.

[0058] Before loading the substrate, the production equipment performs a positioning check using the high-precision visual positioning system configured in S13 to ensure that the support points are completely within the supplementary area and that the minimum clearance distance from the front layer is ≥1.5mm. After the check is passed, the production equipment smoothly transfers the substrate and completes the loading operation. During loading and placement, because the substrate maintains an upward orientation with its second surface facing up, the upward support points of the auxiliary mechanism are stably and accurately placed on the supplementary area with the first surface facing down.

[0059] Figure 4 This demonstrates the demanding process of performing a second sintering step when the substrate is flipped (second surface facing up). The image clearly outlines how the ejector pins of the auxiliary support mechanism precisely constrain the supplementary area of ​​the first surface upwards, and the "three-dimensional spatial avoidance boundary" that completely surrounds the pre-layer is marked with a dashed box. During the high-temperature flipping process, the solidified precision pre-layer is not only avoided on the plane, but also receives comprehensive physical suspension protection in the vertical space, eliminating the risk of secondary scratches, pressure deformation, or sagging. At the same time, it ensures that the functional area of ​​the pre-layer facing down on the substrate has no physical contact with the auxiliary mechanism throughout the process, perfectly achieving physical anti-interference support.

[0060] S54 Second Sintering Process Control and Heat Insulation Layer Construction After the substrate is loaded, the production equipment sends the loaded substrate into a mesh belt sintering furnace to perform the second sintering process, where the glass layer is solidified by high-temperature sintering. The production equipment sets the peak sintering temperature to 850℃, which is exactly the same as the peak temperature of the first sintering.

[0061] During the heat preservation sintering process, the production equipment also maintains a sufficient air supply to the furnace to maintain an oxidizing sintering atmosphere, ensuring that the ruthenium-based resistive slurry in the heat-generating body layer stably forms a conductive network and avoids oxygen deficiency reduction and deterioration.

[0062] Throughout the sintering process, the production equipment continuously locks the support point position of the auxiliary mechanism, maintaining spatial avoidance and non-contact constraint on the front layer. Although the first surface of the substrate is in a downward-facing suspended position during the second sintering, thanks to the crystalline borosilicate glass used in the front glass layer, which has precipitated microcrystalline phases during the first sintering, its secondary softening point is much higher than the current 850℃ sintering temperature, thus eliminating the physical risk of the front layer softening again due to heat and undergoing gravitational sag distortion.

[0063] After sintering, the rear glass layer is completely cured to form a heat-insulating layer. The preset thermal conductivity blocking threshold of the heat-insulating layer is 1.5 W / m·K, and the thermal conductivity of the cured rear glass layer is ≤1.5 W / m·K. Compared with the highly thermally conductive alumina ceramic substrate, this heat-insulating layer can effectively limit the heat conduction path that is rapidly lost to the external space through the second surface.

[0064] S55 Pre-layer Leveling Treatment and Installation Benchmark Establishment After the second sintering is completed and the substrate is cooled to below 100°C in the furnace before being removed from the furnace, the production equipment then performs a planarization treatment on the first surface of the substrate. A chemical mechanical polishing process is used to further optimize the microscopic flatness of the pre-layer surface, eliminating microscopic paste residues unavoidable in the screen printing process. Without damaging the molding structure, the surface flatness of the pre-layer is strictly constrained within a preset tolerance threshold (flatness ≤ 0.008 mm / 100 mm, surface roughness Ra ≤ 0.1 μm). This tolerance threshold, combined with the absence of macroscopic deformation from the preceding processes, ensures a tight fit between the pre-layer and the fixing belt, eliminating heat conduction losses caused by minute contact gaps.

[0065] The production equipment simultaneously extracts the supplementary area as the sole installation reference, clearly defining that the supporting force of the external components during subsequent fixed installation will only act on this installation reference. Spatial physical avoidance is performed on the front layer throughout the process, ultimately constructing a complete heat transfer interface without structural obstruction, so that the fixing heat generated by the front heating element can be efficiently conducted to the outside through this heat transfer interface.

[0066] S6 Fixing Operation: Isothermal Boundary Construction and Directional Control of Heat Flow S61 substrate fusing assembly and positioning fixation The operator first positions and fixes the substrate according to the installation reference established by S55, and then assembles the substrate, which has completed the entire process, into the fixing assembly of the laser printer. During the assembly process, the supporting force of the external fixing components only acts on the filling area, avoiding physical contact with the front layer throughout the process, and avoiding damage to the flat heat transfer interface of the front layer.

[0067] The first surface of the substrate is in close contact with the inner circumferential surface of the fixing belt of the fixing assembly. Through the elastic pressing structure of the fixing assembly, the bonding gap between the heat transfer interface of the pre-layer and the fixing belt is controlled to ≤0.005mm. There is no structural obstruction. This gap threshold is set in combination with the surface flatness tolerance of the pre-layer in S55. It can eliminate the heat conduction loss caused by the contact gap to the greatest extent and ensure the efficiency and uniformity of heat transfer.

[0068] S62 fixing command reception and heating circuit synchronous triggering After the fusing substrate, fabricated through the entire process, is assembled, the control unit (such as the printer's main control system), electrically connected to the substrate, receives the fusing command generated by the printing task. In response to the fusing command, the control unit triggers the power supply circuits of the front and rear heating elements via a synchronous PWM drive signal from the same main control chip, ensuring that the startup timing difference between the two circuits is ≤1ms, and synchronously starting the heating programs of both heating elements. This synchronous triggering design avoids deviations in the startup timing of the heating elements on both sides, thereby significantly reducing the temperature difference between the two sides of the substrate in the initial stage of operation, laying a solid foundation for the stable construction of the subsequent isothermal boundary.

[0069] S63 Operating Temperature Acquisition and Constant Isotemperature Boundary Construction After the two heating elements are activated, the control unit collects the heating temperature data in real time through temperature sensors configured in the front and rear layers respectively. The temperature sensors in both the front and rear layers directly use the synchronously printed, non-protruding thick-film temperature sensing layer for sensing, avoiding the mechanical interference that is easily caused by traditional physical sensors, and eliminating the thermal conduction delay caused by the heat resistance of the rear glass layer, thus ensuring an extremely sensitive transient response speed.

[0070] The main control system acquires data at a frequency of ≥100Hz, with a single sampling corresponding to a paper feed distance of only 3mm, accurately capturing transient temperature changes as the paper passes by. The control unit adjusts the operating power input to the rear heating element in real time according to the preset fixing operating temperature, and performs closed-loop control based on the actual heating temperature feedback from the rear temperature sensing layer, ensuring that the heating temperature of the rear heating element quickly reaches and is stably maintained at the preset fixing operating temperature. Based on the laws of thermodynamic conduction, this actively constructs a constant isothermal boundary on the second surface of the substrate, eliminating the temperature gradient between the first and second surfaces.

[0071] Figure 5In the comparison diagram on the left, a large amount of ineffective heat flow escapes to the back side in the traditional substrate, which is the reason for the collapse of the overall temperature field. On the right, the "heat-resistant layer" at the bottom of the "isothermal boundary" constructed by the rear heating element in this application is presented. This forces all the red fixing heat flow to be output unidirectionally and upward with extremely high density, so that the heat generated by the front heating element loses the physical driving force for conduction to the second surface in the back side, and provides sufficient thermal capacity buffer to resist the transient thermal shock on the front side.

[0072] S64 Directional Heat Flow Control and Precise Control of Transient Temperature Drop During the maintenance of the isothermal boundary, the control unit simultaneously utilizes the outermost heat-insulating layer of the second surface to limit the heat transfer path lost through convection to the external space via the second surface. When the cold paper passes by at high speed, causing a sharp temperature drop in the front layer, the real-time temperature of the front heating element will instantly drop below the temperature of the rear heating element. At this moment, thanks to the constant isothermal boundary maintained by the rear heating element, the thermodynamic temperature gradient across the substrate is instantly reversed, and the potential backflow of heat is completely blocked.

[0073] exist Figure 6 In the diagram, when a violent heat extraction occurs on the front, the thermal energy stored in the rear heating element is clearly shown to immediately adapt to the temperature gradient that is instantly broken and reversed, and to carry out a dynamic process of "directional and rapid replenishment" vertically upward with a strong red arrow.

[0074] This directional heat flow control mechanism, combined with the physical blockage of the heat-insulating layer, precisely controls the transient temperature drop of the pre-layer when subjected to high-speed paper thermal shock within a preset range (e.g., ≤1℃). Under this constraint, even in high-speed continuous operation with a paper feed speed of 300mm / s, the actual temperature fluctuation of the pre-layer within a single sheet fixing cycle is strictly controlled, thus maintaining the working temperature extremely stably within the optimal fixing range of 180℃ to 200℃, preventing localized cold spots or temperature collapse that could lead to fixing failure.

[0075] S65 fixing operation and toner melting and curing After the two heating elements reach the preset fixing temperature range, the main control system drives the toner-coated printing medium to move at a constant speed along the first surface of the substrate with the fixing belt. During the movement of the printing medium, the heat generated by the front heating element is uniformly and directionally conducted to the printing medium through the first surface and the fixing belt, allowing the toner to fully melt and solidify on the surface of the printing medium, completing the entire fixing process. The uniform thermal resistance distribution of the front layer and the extremely stable dynamic temperature field under the same temperature boundary constraint form a positive synergy, ensuring a highly consistent melting effect of the toner on the entire printing medium, thus completely avoiding printing defects such as ghosting, blurred text, and poor fixing at the source.

[0076] This method eliminates the conditions for the generation of microscopic thermal resistance distortion through a non-contact sintering process, cuts off the physical path of back heat flow escape by constructing a dynamic isothermal boundary, and provides a stable foundation for the precise control of the isothermal boundary through the uniform thermal resistance distribution of the front layer. The stable maintenance of the isothermal boundary reduces the thermal cycling stress of the substrate and avoids the long-term degradation of the front layer. The two work synergistically to reduce the printing defect rate of laser printers during continuous high-speed operation to below 1% and increase the production yield of heating components to over 97%. This method solves the problem of the collapse of the fixing temperature field caused by the uncontrolled coupling of microscopic thermal resistance distortion and macroscopic back heat flow dissipation in the prior art, and effectively suppresses the occurrence of defective products printed by laser printers.

[0077] This embodiment also discloses the application of a method for suppressing the occurrence of defective products in laser printers in the fixing operation of laser printers. The alumina ceramic substrate prepared by the aforementioned method is adapted to the fixing component of the laser printer to perform the fixing operation. Relying on the coordinated control of the front heating element and the rear heating element on both sides of the substrate and the uniform thermal resistance structure formed by the non-contact process, the dynamic temperature field of fixing is stabilized, thereby suppressing the generation of defective products from the root.

[0078] The substrate, having undergone complete fabrication, is assembled into the fixing assembly of a laser printer using a pre-defined filler area as the sole mounting reference. During assembly, the supporting force of the external fixing components acts only on the filler area, avoiding physical contact with the front layer on the first surface of the substrate throughout the process. This ensures that the first surface of the substrate is in close contact with the inner circumferential surface of the fixing belt of the fixing assembly, controlling the gap between the two to ≤0.005mm. This eliminates heat conduction loss caused by the contact gap and creates a uniform heat transfer interface without obstruction.

[0079] After receiving the fixing command generated by the printing task, the printer control unit, which is electrically connected to the substrate, synchronously triggers the power supply circuits of the front heating element in the front layer and the rear heating element on the second surface of the substrate, controlling the start-up timing difference of the two circuits to be ≤1ms, and synchronously starts the heating program. The control unit collects the actual heating temperature of the two heating elements in real time at a frequency of ≥100Hz through the thick film temperature sensing layers built into the front and rear layers. With the preset fixing working temperature of 180℃-200℃ as the target, it adjusts the input power of the rear heating element in a closed loop to keep the heating temperature of the rear heating element stable at the fixing working temperature, and builds a constant isothermal boundary on the second surface of the substrate, completely eliminating the temperature gradient between the front and back of the substrate, and cutting off the thermodynamic force for the heat generated by the front heating element to escape to the second surface. At the same time, relying on the rear glass heat-insulating layer with a thermal conductivity of ≤1.5W / m·K on the outermost side of the second surface, it restricts the convective loss of heat to the external environment and forces the fixing heat to be output unidirectionally to the first surface of the substrate.

[0080] When cold paper passes by at high speed, causing a transient temperature drop in the front layer, the control unit maintains a constant temperature output from the rear heating element, instantly reversing the temperature gradient across the substrate. This forces the heat stored in the rear heating element to be directionally replenished to the first surface, precisely controlling the transient temperature drop of the front layer within an amplitude range of ≤1℃. Even under high-speed continuous paper feeding conditions of 300mm / s, the operating temperature of the front layer can be stably maintained within the optimal fixing range, avoiding problems such as local cold spots or temperature field collapse.

[0081] Once the temperature of the front heating element stabilizes at the preset fixing temperature, the printer's main control system drives the printing medium with toner attached to move at a constant speed along the first surface of the substrate with the fixing belt. The fixing heat generated by the front heating element is evenly conducted to the printing medium through the first surface and the fixing belt, so that the toner is fully melted and solidified on the surface of the medium, completing the entire fixing process.

[0082] The above are all preferred embodiments of this application, and are not intended to limit the scope of protection of this application. Therefore, all equivalent changes made in accordance with the structure, shape and principle of this application should be covered within the scope of protection of this application.

Claims

1. A method for suppressing the occurrence of defective printed products by a laser printer, characterized in that, include: A front layer containing a front heating element is printed on the first surface of the substrate. The printing coordinates of the front layer are extracted, and the area on the first surface of the substrate corresponding to the area outside the printing coordinates is established as the complement area. Configure a support fixture and perform a first sintering on the front layer, controlling the force point of the support fixture to act only on the projection range of the supplementary area on the second surface of the substrate; After the first sintering, the substrate is controlled to cool down to release thermal stress; A rear layer containing a rear heating element is printed on the second surface of the substrate. An auxiliary mechanism is configured and a second sintering is performed on the rear layer. The auxiliary mechanism is controlled to avoid the front layer and its support point is constrained to the supplementary area on the first surface. A control unit is configured to connect to the front heating element and the rear heating element. The control unit is configured to control the front heating element to heat up to a preset fixing working temperature in response to a fixing command, and simultaneously control the rear heating element to heat up, so as to construct a temperature boundary matching the fixing working temperature on the second surface, eliminate the temperature gradient between the first surface and the second surface, and block the escape conduction of heat from the first surface to the second surface.

2. The method according to claim 1, characterized in that, The process involves printing a pre-heating layer containing a pre-heating element on the first surface of a substrate, extracting the printing coordinates of the pre-heating layer, defining the area on the first surface of the substrate outside the printing coordinates as a supplementary area, configuring a support fixture, performing a first sintering on the pre-heating layer, and controlling the force point of the support fixture to act only within the projection range of the supplementary area on the second surface of the substrate, including: A first conductor layer, a positive heating element layer serving as the front heating element, a temperature measuring layer, and a front glass layer are sequentially printed on the first surface to construct the front layer; Extract the joint printed coordinates of the first conductor layer, the positive heating element layer, the temperature measuring layer and the front glass layer, and establish the area on the first surface of the substrate that corresponds to the area outside the joint printed coordinates as the complement region; During the first sintering of the front layer to solidify the front glass layer, the force point of the support fixture is controlled to be locked within the projection range of the supplementary area on the second surface of the substrate, maintaining spatial avoidance and non-contact constraint for the joint printing coordinates.

3. The method according to claim 1, characterized in that, The step of controlling the substrate to cool down after the first sintering to release thermal stress includes: After the first sintering of the front layer is completed, the step of printing the back layer on the second surface is blocked. Allow the substrate to cool down naturally; In response to the temperature of the substrate dropping to a preset room temperature threshold, the step of printing the back layer on the second surface is unlocked.

4. The method according to claim 3, characterized in that, The process of allowing the substrate to cool down naturally includes: Cut off the external forced cooling source and maintain a cooling environment without external thermal intervention; The thermal stress accumulated on the substrate due to the first sintering is released in the cooling environment; After releasing the thermal stress, the relative spatial coordinates of the front layer and the supplementary area are locked, and the locked relative spatial coordinates are extracted as a physical avoidance reference, so that the support point of the auxiliary mechanism can be constrained to the supplementary area on the first surface by using the physical avoidance reference during the second sintering.

5. The method according to claim 4, characterized in that, The rear layer includes a second conductor layer, a reverse heating element layer, a rear temperature measuring layer, and a rear glass layer, wherein the reverse heating element layer serves as the rear heating element; The step of printing a rear layer containing a rear heating element on the second surface of the substrate, configuring an auxiliary mechanism and performing a second sintering on the rear layer, controlling the auxiliary mechanism to avoid the front layer, and constraining its support points to the supplementary area on the first surface includes: The second conductor layer, the heat-conducting element layer, the rear temperature sensing layer, and the rear glass layer are sequentially printed on the second surface of the substrate; Extract the physical avoidance benchmark and map it as a three-dimensional spatial avoidance boundary for the auxiliary mechanism; During the second sintering process, the auxiliary mechanism is used to avoid boundary constraints in the three-dimensional space, positioning its support point in the supplementary area on the first surface and avoiding physical contact with the pre-layer, so as to solidify the post-glass layer.

6. The method according to claim 5, characterized in that, Eliminating the temperature gradient between the first surface and the second surface includes: The rear glass layer, which is solidified on the outermost side of the second surface, is configured as a heat-insulating layer with a thermal conductivity less than a preset blocking threshold. The heat-insulating layer is used to limit the heat transfer path lost to the external space via the second surface; The same temperature boundary and the heat-insulating layer work together to suppress the physical channels through which heat is lost from the second surface, and force the heat generated by the front heating element to be output unidirectionally to the first surface side.

7. The method according to claim 6, characterized in that, The control unit is configured to synchronously control the heating of the rear heating element to construct a temperature boundary on the second surface that matches the fixing operating temperature, including: The control unit is configured to acquire the actual heating temperatures of the front heating element and the rear heating element, respectively. The control unit is configured to adjust the operating power input to the rear heating element according to the preset fixing working temperature, and perform closed-loop feedback based on the actual heating temperature of the rear heating element to control the heating temperature of the rear heating element to be stable at the fixing working temperature. By utilizing the stabilized heating temperature, a constant isothermal boundary is constructed on the second surface, which, together with the heat-insulating layer, continuously eliminates the temperature gradient and blocks the backflow of heat.

8. The method according to claim 7, characterized in that, The method of continuously eliminating the temperature gradient and blocking heat loss in the reverse direction in conjunction with the heat-insulating layer includes: When the front layer experiences a transient temperature drop due to the high-speed passing of the paper, the rear heating element maintains a stable heating temperature to preserve the same temperature boundary on the second surface. The same temperature boundary is used to reverse the temperature gradient across the substrate, weakening and blocking the thermal conduction force transferred to the second surface; The heat-insulating layer works together to suppress heat loss to the external environment, forces the heat stored in the rear heating element to be directionally replenished to the first surface, and clamps the transient temperature drop of the front layer within a preset amplitude range.

9. The method according to claim 8, characterized in that, Before configuring the control unit, the following is also included: A planarization process is performed on the first surface of the substrate to optimize the microscopic flatness of the surface of the front layer, and the surface flatness of the front layer is constrained within a preset tolerance threshold. The supplementary area is extracted as the mounting reference, and when the substrate is fixed, the supporting force of the external components is constrained to act only on the mounting reference; Using the installation reference, the front layer is spatially physically avoided, and the front layer, which reaches the preset tolerance threshold, is constructed to form a heat transfer interface without structural obstruction, so that the fixing heat generated by the front heating element can be conducted to the outside through the heat transfer interface.

10. The application of a method for suppressing the occurrence of defective prints in a laser printer as described in any one of claims 1 to 9 in the fixing operation of a laser printer, characterized in that, include: The substrate prepared by the method is assembled into the fixing assembly, such that the first surface of the substrate abuts against the fixing belt of the fixing assembly. The fixing command is input to the control unit to trigger the heating of the front heating element and the rear heating element, thereby constructing the same temperature boundary and eliminating the temperature gradient between the first surface and the second surface; After the heating temperature reaches the preset fixing working temperature, the printing medium with toner attached is driven to move along the first surface with the fixing belt. The heat generated by the preheating element is conducted to the printing medium via the first surface and the fixing belt, causing the toner to melt and solidify on the surface of the printing medium.

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