Crack Prevention in 3D Printed Parts

3D printing method for automotive thin-walled parts with improved print quality and reduced risk of defects in complex shapes. The method involves dynamically adjusting the filling strategy based on the slope of the part contour. It calculates the slope of the contour lines and divides the part into areas with large and small slope changes. In areas with large slope, vertical filling is used, while in areas with small slope, parallel filling is used. This smooth transition avoids stress concentration points and reduces cracks and deformations.

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3D printing thin-walled parts with reduced internal stress and warpage using a support structure with thermal conductivity. The method involves printing thin-walled parts with a thermally conductive member like columns or ribs adjacent to the walls. This provides a path for heat to dissipate during printing, reducing internal stress and warpage compared to just printing the thin walls alone. The thermally conductive member connects to the walls using a cellular rib structure for stability. The thermally conductive member can also connect to hollow supports for additional heat dissipation.

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Endothermic inkjet 3D printing of parts using dynamic polymers that can self-heal after damage. The process involves printing with dynamic polymer powders and inks that contain reversible bonds. After printing, the parts are heated to promote further bonding and fill any voids, improving mechanical properties. The dynamic bonds also provide self-healing capability when the parts are damaged. This allows repairing cracks and extending part life. The dynamic polymers also enable shape memory functionality.

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Reducing residual stress in additive manufacturing by modifying the substrate design to weaken mechanical constraints during the printing process. The method involves creating slots or movable blocks perpendicular to the printing direction on the substrate. This allows local sliding of the blocks during printing instead of full material contraction, converting some plastic deformation into elastic deformation. This reduces plastic strain accumulation and suppresses residual stress formation compared to conventional printing on solid substrates.

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Ultrasonic additive manufacturing system for joining and repairing metal structures using a contoured sonotrode that rotates and translates to reduce defects when welding metal foils. The contoured welding surface profile prevents cracks and weak spots in the welds when joining or repairing metal parts. The contour eliminates interfaces normal to the weld direction, reducing defects compared to flat weld surfaces. The system involves positioning metal structures adjacent to each other, creating a contoured channel along the interface, and filling it with metal foils using the rotating and translating sonotrode for welding. This reduces cracking and weak points compared to conventional ultrasonic welding.

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3D printing metal objects without warping or cracking by using a tacky polymer substrate. The process involves spreading a layer of metal particles over a polymer substrate with low thermal conductivity and melting the unmasked metal with pulsed light to form each layer of the object. The polymer substrate reduces lateral heat transfer during melting, preventing warping and cracking.

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A method to homogenize the microstructure of additive manufacturing components to mitigate thermal accumulation effects during 3D printing. The method involves using multi-physics coupling to simulate and control the temperature, stress, and microstructure evolution in the printing process. It allows predicting and preventing defects like porosity, cracks, and impurities by optimizing printing parameters based on the simulation results. This helps improve the microstructure and mechanical properties of 3D printed parts compared to experimental methods.

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This method reduces microcracking in additively manufacturing superalloys like nickel-based alloys by using a mixture of high-melt and low-melt superalloy powders. The low-melt powder has a lower solidus temperature than the high-melt powder. When combined in the right ratios, this powder mixture reduces cracking during additive manufacturing compared to using only the high-melt powder.

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A nickel-based superalloy composition for use in selective laser melting (SLM) to enable crack-free processing of Ni-based superalloys with high gamma prime content. The alloy composition contains a minimum of 1.2 wt % Hafnium and has a Hf/C atomic ratio >1.55.

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Ultrasonic additive manufacturing system using a contoured sonotrode to minimize cracking and weak areas when joining and repairing metal structures. The system has a rotating sonotrode with a welding surface that is contoured, such as V-shaped or curved. The contoured profile allows the sonotrode to eliminate interfaces normal to the weld direction, reducing defects. When joining or repairing metal structures, channels with matching contoured profiles are created. Metal foils are then welded into the channels using the sonotrode. This reduces cracking and weak areas compared to conventional flat sonotrodes.

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Laser additive manufacturing methods for high-strength aluminum alloys that suppress residual stress cracking. The methods involve modifying laser scanning parameters like speed, power, and scan path to reduce solidification strain during additive manufacturing.

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3D printing method for large section parts using selective laser melting (SLM) technology that prevents warping and cracking of printed parts with large cross-sections. The method involves scanning large planes by filling and scanning after first scanning a grid pattern. The grid pattern is scanned with a thinner frame than the final part size. This allows heat to conduct more quickly between the grid frames during filling and scanning, preventing excessive heat accumulation. It also balances the shrinkage stresses during cooling and solidification. By scanning the grid first and filling in between, it improves dimensional accuracy and reduces warping and cracking in large section 3D printed parts.

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Additive manufacturing of gas turbine components with internal tunable auxetic structures to mitigate cracking. The internal structures are made from a repeating pattern of interconnected 3D auxetic unit cells. The unit cell is made from intersecting dimpled sheets that exhibit negative Poisson's ratio behavior. This enables the internal structure to contract instead of expand when heated, reducing stresses that can cause cracking. The auxetic structure can be additively manufactured with the component to avoid stress concentrations from separate supports.

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A 3D printing method that reduces porosity and improves the strength of printed parts by using nozzles with non-circular cross-sections. The method involves optimizing the shape of the nozzle holes using computer modeling and simulations to minimize porosity and maximize strength compared to circular nozzles. The optimized nozzles have shapes like trapezoids and inverted trapezoids that extrude filament in a way that reduces voids and improves mechanical properties in the printed parts.

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Method for 3D printing ceramics using photocurable precursors to overcome cracking issues. The method involves controlling crack generation and repair to prevent excessive cracking during printing and make repairs useful. The steps include: 1. Optimizing precursor composition and printing conditions to reduce crack width and number. 2. Printing smaller samples to find the minimum size that only probabilistically generates cracks. 3. Scaling up printing to the required size while maintaining the same crack probability. 4. Repairing cracks using a method that avoids adding new material, such as polishing or bonding the cracked surfaces. 5. Enhancing crack repair by lightening internal regions to reduce feature size and make repairs more effective.

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Additive manufacturing of continuous fiber unidirectional prepreg tapes using a method that addresses issues with existing techniques for 3D printing continuous fiber composite materials. The method involves continuously feeding a thermoplastic matrix material and a continuous fiber reinforcement material through a co-extrusion die to create a unidirectional prepreg tape with a rectangular cross-section. This tape is then 3D printed using a modified FFF (Fused Filament Fabrication) process with a rectangular nozzle. The rectangular cross-section prevents gaps and allows better control of thickness compared to circular tapes. After printing, the part is cured at high pressure to fully consolidate the composite. This avoids cracking issues from the high thermal gradients during curing.

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A method for 3D printing near-zero expansion lattice structures using alternating deposition of aluminum droplets and titanium alloy rods. The method involves 3D printing near-zero expansion lattice structures by selectively embedding titanium alloy rods inside an aluminum matrix formed by droplet jetting. This allows forming near-zero expansion lattices with aluminum and titanium, which have large differences in thermal properties, without direct molten state deposition. The titanium rods are embedded into the aluminum matrix during printing to avoid issues like cracking and voids that can occur when directly printing dissimilar materials.

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A conformal drying method for 3D printed ceramic parts that reduces deformation and improves mechanical properties compared to conventional drying methods. The conformal drying involves printing the ceramic green bodies on hydrophobic films and then drying them at specific humidity levels. The drying is done in steps at decreasing humidity levels. This controlled drying process allows the ceramic parts to shrink uniformly without cracking, warping, or deformation. The resulting dried ceramic parts have better dimensional accuracy, yield, and mechanical properties compared to conventionally dried 3D printed ceramics.

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Optimizing the mechanical properties of additive manufacturing substrates to improve their durability and prevent cracking during the printing process. The method involves a multi-scale optimization approach to analyze and modify the substrate's structure at different length scales. The optimization involves: (1) analyzing the substrate's microstructure to identify regions with high stress concentration, (2) modifying the microstructure in those regions to redistribute stress, (3) analyzing the macrostructure to identify areas with high stress, (4) modifying the macrostructure in those areas to redistribute stress, and (5) repeating steps 1-4 at progressively larger scales until the entire substrate is optimized. This iterative optimization process aims to distribute stress more evenly throughout the substrate at all length scales to prevent localized cracking.

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3D printing technology-based processing apparatus and method to improve strength of 3D printed products. The method involves using a 3D printer to print a 3D model with blind holes or passageways along the vertical direction. Then, a micro injection molding machine fills the holes with a material to form a framework inside the 3D printed object. This disperses forces through the internal structure, preventing concentration and improving strength. The apparatus also has a magnetic field control system to attract the printed material to the platform for better adhesion. This reduces warping and allows printing cantilever structures without supports.

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