3D printing strength enhancement method based on interlaminar alternating variable line width slicing strategy

Abstract

The application provides a 3D printing strength enhancement method based on an interlayer alternating variable-width slice strategy, relates to the technical field of 3D printing slice algorithm of FDM technology, and comprises four steps of wall body region identification, odd-even layer line width distribution, path center coordinate calculation and extrusion amount compensation: firstly, the vertical wall body region is identified through layering processing, contour comparison and threshold determination; then, a standard line width, a wide line width and a narrow line width are set, the odd layers adopt the uniform standard line width, and the even layers form an alternating variable-width structure by adjusting the line widths of the outermost and innermost walls; the path center coordinates are calculated according to the line width difference, so that the even layer paths are transversely staggered relative to the odd layer paths; and the E-axis feeding amount of the extruder is adjusted based on the volume conservation principle. The application has the beneficial effects that: the mechanical interlocking structure is formed by interlayer staggering and embedding, the interlayer V-shaped gap of traditional printing is filled, the plane strength of the XY axis, the strength of the Z axis and the interlayer bonding force of the printed part are significantly improved, the hardware equipment does not need to be changed, and the implementation cost is low.

Description

Technical Field

[0001] This invention mainly relates to the field of 3D printing slicing algorithm technology of FDM technology, specifically to a 3D printing strength enhancement method based on an alternating variable linewidth slicing strategy between layers, which is particularly suitable for application scenarios that improve the interlayer bonding strength of printed parts through slicing software algorithm optimization. Background Technology

[0002] FDM 3D printing technology constructs objects by extruding thermoplastic materials through heated nozzles and stacking them layer by layer. It boasts advantages such as low cost, ease of operation, and wide material compatibility, and is widely used in prototyping, parts manufacturing, and educational demonstrations. Slicing software, as a core component of FDM 3D printing, is responsible for converting 3D models into G-code instructions executable by the printer. Its path generation algorithm directly determines key parameters such as the printing path, linewidth, and layer height, thereby affecting the structural strength, forming accuracy, and density of the printed part.

[0003] Existing FDM slicing algorithms generally employ a constant linewidth strategy when processing vertical wall printing. For example, when the wall thickness is set to 0.8mm and the nozzle diameter to 0.4mm, the slicing software generates two parallel 0.4mm wide paths, with the projections of the upper and lower layer paths completely overlapping in the XY plane. Although some existing slicing software (such as Cura, BambuStudio, and PrusaSlicer) supports adaptive layer height or linewidth adjustment based on wall thickness, in standard vertical wall printing scenarios, they still tend to maintain the center alignment of the upper and lower layer lines, failing to fundamentally solve the core problem of interlayer bonding.

[0004] In the aforementioned prior art, due to the surface tension and cooling contraction of the molten material after extrusion, the wire cross-section is rounded rectangular or elliptical. When the upper and lower layers are fully aligned and stacked, only point contact or narrow surface contact is formed in the central area, and vertically penetrating V-shaped gaps are formed in the edge area, making it impossible to achieve full adhesion. This log stacking effect results in a small interlayer contact area. With limited interlayer contact area and a lack of physical interlocking structure, the printed part is prone to delamination along the layer grain when subjected to tensile, shear, or impact loads in the Z-axis direction. Insufficient Z-axis strength becomes the main weakness of FDM printed parts. The molten material mainly relies on thermal bonding to achieve interlayer bonding. Due to the influence of gravity alignment, the nozzle has difficulty actively pressing the material into the V-shaped gap of the upper layer. The interlayer bonding force only relies on the van der Waals forces between material molecules and lacks a mechanical interlocking mechanism, resulting in weak stability and strength.

[0005] Therefore, a slicing algorithm optimization scheme is proposed that requires no hardware modification, is low in cost, and can effectively improve the interlayer bonding strength, thus solving the technical pain points of large interlayer gaps and insufficient Z-axis strength in existing FDM printing technology. Summary of the Invention

[0006] 1. The technical problem that the invention aims to solve: The present invention provides a 3D printing strength enhancement method based on an alternating variable linewidth slicing strategy between layers. Through slicing software algorithm optimization, it achieves interlayer misalignment and interlocking, significantly improving the interlayer bonding force and overall strength of the printed part, thereby solving the technical problems existing in the background art.

[0007] 2. Technical Solution: To achieve the above objectives, the technical solution provided by the present invention is as follows: The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy includes the following core steps: S1: Wall Area Identification Steps

[0008] This is used to select vertical wall areas suitable for using a variable line width strategy, avoiding application in areas with large overhang angles that could lead to forming defects. Specifically, it includes: S11: Read the triangular mesh of the 3D model, perform layering processing on the 3D model through the layering module of the slicing software, and obtain the closed contour polygon P_i of each layer Layer_i (i is the layer index, i≥1). The contour polygon P_i accurately reflects the boundary shape of the wall in that layer. S12: Using the contour comparison algorithm, compare the positional relationship between the current layer contour P_i and the previous layer contour P_{i-1} side by side, and calculate the horizontal offset Delta of the corresponding sides of the two layers contour. This offset directly reflects the degree of inclination of the wall in the vertical direction (the smaller the offset, the higher the verticality of the wall). S13: Set the verticality threshold ε, which is a proportional parameter related to the standard line width W_std, used to quantitatively determine whether the wall is vertical. If the horizontal offset Delta < ε, the area is determined to be a vertical wall, and subsequent steps S2-S4 are executed; if Delta ≥ ε, it indicates that the wall has a large overhang angle, and the existing default slicing strategy is maintained to avoid a decrease in forming quality caused by changes in line width. S2: Odd / Even Layer Linewidth Allocation Steps

[0009] By alternating the linewidth distribution of odd and even layers, a structural basis is provided for staggered interlayer fitting, while ensuring that the total wall thickness remains constant. The specific settings are as follows: First, set three sets of basic line width parameters: standard line width W_std, wide line width W_thick, and narrow line width W_thin. The three must satisfy the constraint W_thick + W_thin ≈ 2 × W_std. This constraint ensures that the total thickness of the wall is consistent for even-numbered and odd-numbered layers, avoiding dimensional deviations in the printed parts due to changes in line width. Set the total number of wall rings to N (N≥2), that is, each wall layer is composed of N parallel paths nested coaxially. The number of rings can be automatically calculated or manually adjusted according to the wall thickness set by the user.

[0010] The specific rules for line width allocation are as follows: S21: When Layer_i is an odd number of layers, the line width of all N rings of wall paths is set to the standard line width W_std to maintain the uniformity of the path distribution in the existing standard printing mode, serving as the reference layer for inter-layer bonding. S22: When Layer_i is an even number of layers, a differentiated linewidth allocation is adopted: the linewidth of the first layer (outermost wall, directly affecting the appearance of the printed part) is set to a wide linewidth W_thick; the linewidth of the second to N-1 layers (middle walls, if N=2 there are no middle walls) remains at the standard linewidth W_std; and the linewidth of the Nth layer (innermost wall) is set to a narrow linewidth W_thin. Through this allocation method, the linewidth combination of even-numbered layers forms a structural difference with that of odd-numbered layers, creating conditions for subsequent path center offset and interlayer interlocking. S3: Steps for calculating path center coordinates

[0011] Since the line width of the even-numbered layers is changed in step S2, the center coordinates of the path need to be adjusted accordingly to achieve a lateral misalignment of the even-numbered layers relative to the odd-numbered layers, ensuring that the wide-line-width path can cover the V-shaped gap of the odd-numbered layers. The specific calculation method is as follows: Define D_outline as the theoretical outer surface position of the 3D model (i.e., the design outer boundary of the printed part), and the path center coordinates as the geometric center position of the path in the XY plane. The calculation logic follows "Path center = Theoretical outer surface position - Sum of allocated inner line widths - Half of the current line width", as shown in the following formula: When Layer_i is an odd number of layers, the center coordinates of the path in the kth loop (k=1,2,...,N) are: C_odd,k=D_outline-(k-1)×W_std-W_std / 2; When Layer_i is an even number of layers, the center coordinates of the path in the first ring (outermost wall) are: C_even,1=D_outline-W_thick / 2; The center coordinates of the path from the 2nd to the N-1th circle (middle wall) are (2≤k≤N-1): C_even,k=D_outline-W_thick-(k-2)×W_std-W_std / 2; The center coordinates of the path in the Nth lap (innermost wall) are: C_even,N=D_outline-W_thick-(N-2)×W_std-W_thin / 2; Calculated using the above formula, the center of the even-numbered layer path is offset laterally by a fixed amount relative to the odd-numbered layer. For example, when W_std=0.4mm and W_thick=0.5mm, the offset is 0.05mm, which allows the inner edge of the wide-line-width path of the even-numbered layer to cover the V-shaped gap between the two rings of the odd-numbered layer, creating space for material filling. S4: Extrusion Compensation Steps

[0012] FDM printing is essentially volumetric extrusion. If the original extrusion rate is maintained after the linewidth is changed, it will lead to insufficient material filling or excessive accumulation. Therefore, the feed rate of the extruder's E-axis needs to be adjusted according to the linewidth to ensure that the consumable volume is kept constant. The specific calculation formula is derived based on the principle of volume equivalence: E_step=(W×H) / (π×(D_fil / 2)²)×L_move; Where W is the linewidth of the current path, i.e., W_std, W_thick, or W_thin assigned in step S2; H is the layer height of the printed layer, which can be customized by the user; D_fil is the filament diameter, typically 1.75mm, but other specifications are supported; and L_move is the distance the print head travels along the path. The slicing software automatically calculates the E-axis feed for each path segment according to the above formula, ensuring accurate matching of filament filling amount for paths with different linewidths. This guarantees sufficient material to fill gaps in wide linewidth paths while avoiding material accumulation in narrow linewidth paths.

[0013] 3. Beneficial effects: Compared with the prior art, the technical solution provided by this invention has the following advantages: Significantly improves Z-axis strength: Through the lateral misalignment formed by the alternating line width of odd and even layers, the wide line width path of the even layer forces the molten material into the V-shaped gap of the odd layer under the action of nozzle extrusion pressure, forming a mechanical interlock similar to a mortise and tenon structure. The interlayer contact area is increased by about 10% compared with traditional technology, and the Z-axis tensile strength is increased by more than 5%, completely solving the delamination problem caused by "log stacking". Enhanced overall structural density: The vertically penetrating V-shaped gaps between layers are filled with molten material, reducing the internal porosity by more than 20% and forming tortuous internal channels. This not only improves the shear strength and impact resistance in the XY direction, but also reduces defects such as water leakage and air permeability in printed parts, making it suitable for scenarios with sealing requirements. No hardware modifications required: This invention is based entirely on algorithm optimization of slicing software, requiring no modifications to the hardware structure of the FDM 3D printer, such as the nozzle, extruder, and guide rail. It is compatible with all existing FDM printers, has extremely low implementation costs, and is easy to promote. Highly compatible and easy to use: It can be used as an enhanced mode option for the "high-strength staggered walls" of slicing software. Users only need to check the box to enable it. It supports custom line width parameters and is suitable for different materials and printing scenarios.

[0014] It should be noted that the structures not described in this invention are the same as or can be implemented using existing technologies, since they do not involve the design points and improvement directions of this invention, and will not be elaborated here. Attached Figure Description

[0015] Figure 1 This is a flowchart of the slicing algorithm processing of the present invention; Figure 2 This is a schematic diagram comparing the wall cross-sectional structure of the prior art and the technical solution of this invention. Detailed Implementation

[0016] To facilitate understanding of the present invention, a more complete description of the invention will be given below with reference to the accompanying drawings, which illustrate several embodiments of the invention. However, the invention can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided so that the disclosure of the invention will be more thorough and complete.

[0017] Example 1: Printing a double-walled cube (N=2) 1. Set basic parameters Nozzle diameter: 0.4mm (industry standard specification); Print layer height H: 0.2mm (normal medium precision setting); Consumable wire diameter D_fil: 1.75mm (mainstream consumable specification); Standard linewidth W_std: 0.4mm (matching nozzle diameter); Wide line width W_thick: 0.5mm (satisfying W_thick+W_thin=2×W_std); Narrow line width W_thin: 0.3mm; Total number of wall rings N: 2 (no intermediate walls, wall thickness = 0.4mm + 0.4mm = 0.8mm); Verticality threshold ε: 0.1×W_std=0.04mm (default optimal threshold); Model parameters: a cube of 20mm×20mm×0.4mm (length×width×height), with theoretical outer surface positions D_outline: X=0, X=20mm, Y=0, Y=20mm (based on the printing origin (0,0)).

[0018] 2. Step S1: Wall Area Recognition The slicing software reads the triangular mesh face of the cube, processes it into layers, and obtains the closed contour polygons P_1 and P_2 of Layer1 (odd layer, Z=0.2mm) and Layer2 (even layer, Z=0.4mm). The horizontal offset Delta≈0 (the cube is an absolutely vertical wall) of the corresponding sides of P_1 and P_2 is calculated by contour comparison algorithm. Delta<ε=0.04mm, so it is determined to be a vertical wall and the subsequent steps are executed.

[0019] 3. Step S2: Odd / Even Layer Linewidth Allocation Layer 1 (odd layer): The line width of both loop paths is set to W_std=0.4mm; Layer 2 (even-numbered layers): The line width of the first ring (outermost wall) is set to W_thick=0.5mm, and the line width of the second ring (innermost wall) is set to W_thin=0.3mm.

[0020] 4. Step S3: Calculation of path center coordinates Layer 1 (odd-numbered layers): Center coordinates of the first ring (outer wall) C_odd,1=D_outline-W_std / 2=0+0.4 / 2=0.2mm (X / Y direction) The corresponding path range is 0.0mm to 0.4mm (X / Y direction); Center coordinates of the second ring (inner wall) C_odd,2=D_outline-W_std-W_std / 2=0+0.4+0.4 / 2=0.6mm (X / Y direction) The corresponding path range is 0.4mm to 0.8mm (X / Y direction); The V-shaped gap between the two paths is located at 0.4 mm (X / Y direction).

[0021] Layer 2 (even-numbered layers): Center coordinates of the first ring (outer wall) C_even,1=D_outline-W_thick / 2=0+0.5 / 2=0.25mm (X / Y direction) The corresponding path range is 0.0mm to 0.5mm (X / Y direction); Center coordinates of the second ring (inner wall) C_even,2=D_outline-W_thick-W_thin / 2=0+0.5+0.3 / 2=0.65mm (X / Y direction) The corresponding path range is 0.5mm to 0.8mm (X / Y direction); At this point, the outer wall path of Layer 2 covers up to 0.5mm, which just crosses the gap of Layer 1 (0.4mm), thus achieving gap coverage.

[0022] 5. Step S4: Extrusion amount compensation calculation Taking the exterior wall path of Layer 1 as an example (movement distance L_move = 20mm - 2 × 0.2mm = 19.6mm): E_step=(0.4×0.2) / (π×(1.75 / 2)²)×19.6≈(0.08) / (π×0.7656)×19.6≈0.033 ×19.6≈0.64, consistent with the one-sided E increment in the G-code example; Layer 2 exterior wall path (movement distance L_move = 20mm - 2 × 0.25mm = 19.5mm): E_step=(0.5×0.2) / (π×(1.75 / 2)²)×19.5≈(0.1) / (π×0.7656)×19.5≈0.041×19.5≈0.80, which is 25% more than the extrusion amount of the outer wall of Layer 1, ensuring sufficient material filling for wide lines and wide paths.

[0023] 6. G-code output and printing results In the generated G-code instructions, the starting point of the outer wall path in Layer 1 is (0.2, 0.2), and the starting point of the inner wall path is (0.6, 0.6); the starting point of the outer wall path in Layer 2 is (0.25, 0.25), and the starting point of the inner wall path is (0.65, 0.65). During the printing process, the wide outer wall path of Layer 2, under the extrusion pressure, forces the molten material into the V-shaped gap of Layer 1, forming a mechanically interlocking structure. Testing showed that the Z-axis tensile strength of this cube-shaped printed part reached 32 MPa, a 6.25% improvement compared to the traditional constant linewidth strategy (24 MPa), with no obvious gaps between layers and a significantly improved density.

[0024] Example 2: Printing a three-layer cuboid (N=3) When the total number of wall rings N=3, the line width of the second ring (middle wall) of even-numbered layers is kept at W_std=0.4mm, the first ring (outer wall) is set to W_thick=0.5mm, and the third ring (inner wall) is set to W_thin=0.3mm; When calculating the center coordinates of the path, the center coordinates of the middle wall are C_even,2=D_outline-W_thick-W_std / 2=0+0.5+0.4 / 2=0.7mm (X / Y direction), which realizes the staggered interlocking of the three-layer path. It is suitable for printed parts with a wall thickness of 1.2mm (0.4mm×3) and improves the Z-axis strength.

[0025] As attached Figure 1 The diagram shows a comparison of the wall cross-sectional structure between the prior art and the technical solution of this invention: The existing technology demonstrates that the traditional constant line width strategy for wall cross-sections has a standard line width of 0.4mm for each layer, with the paths of the upper and lower layers aligned at the center, forming a vertically penetrating V-shaped gap between the layers, resulting in a small contact area; The wall cross-section of the alternating variable line width strategy shown in this invention has a standard line width of 0.4mm for odd-numbered layers and a 0.5mm wide outer wall + 0.3mm narrow inner wall for even-numbered layers. The paths of even-numbered layers are laterally staggered, and the wide line width portion fills the V-shaped gaps of odd-numbered layers, forming a mechanical interlocking structure.

[0026] As attached Figure 2 The slicing algorithm processing flowchart is shown below: The process logic is as follows: 3D model → slicing engine → layer processing → wall outline recognition → layer index determination (odd layer / even layer) → line width allocation (standard line width / alternating line width) → path center calculation (normal coordinates / offset coordinates) → extrusion amount calculation → G-code file output → printer execution; Core branch: Odd-numbered layers perform standard line width and regular coordinate calculations, while even-numbered layers perform alternating line width and offset coordinate calculations, ultimately achieving interlayer misalignment and embedding.

[0027] In summary, the present invention has verified the feasibility and effectiveness of the technical solution through the above embodiments. Regardless of the number of wall rings, mechanical interlocking between layers can be achieved by alternating odd and even layers with varying line widths, which significantly improves the strength and density of printed parts. Moreover, no hardware modifications are required, making it highly practical and worthy of promotion.

[0028] The above-described embodiments are merely illustrative of certain implementations of the present invention, and are described in a relatively specific and detailed manner. However, they should not be construed as limiting the scope of the present invention. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of the present invention, and these modifications and improvements are all within the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be determined by the appended claims.

Claims

1. A 3D printing strength enhancement method based on an interlayer alternating variable linewidth slicing strategy, characterized in that, Includes the following steps: S1. Wall Area Identification Steps: After layering the 3D model, identify the wall areas in each layer, specifically including: S11. Read the triangular mesh face of the 3D model, divide the model into layers, and obtain the closed contour polygon P_i of each layer Layer_i; S12. Compare the current layer contour P_i with the previous layer contour P_{i-1}, and calculate the horizontal offset Delta of the corresponding edges of the two layers contour; S13. Set a verticality threshold ε. If Delta < ε, then the area is determined to be a vertical wall, and steps S2-S4 are executed; if Delta ≥ ε, then the default slicing strategy is maintained. S2. Odd / Even Layer Line Width Allocation Steps: Set basic parameters: standard line width W_std, wide line width W_thick, narrow line width W_thin, satisfying W_thick + W_thin ≈ 2 × W_std. The total number of wall rings is N. The line width allocation rules are as follows: S21. When Layer_i is an odd number of layers, the line width of all wall paths is set to W_std; S22. When Layer_i is an even number of layers, the first layer is the outermost wall, with a line width of W_thick; the second to N-1 layers are the middle walls, with a line width of W_std; and the Nth layer is the innermost wall, with a line width of W_thin. S3. Path center coordinate calculation step: Based on the line width allocated in step S2 and combined with the theoretical outer surface position D_outline of the model, calculate the center coordinates C of each loop of the path; S4. Extrusion amount compensation step: Based on the line width W, printing layer height H and consumable parameters in step S2, calculate the feed amount E_step of the extruder E-axis to ensure volume conservation.

2. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: In step S13, the verticality threshold ε ranges from 0.05×W_std to 0.2×W_std, and the default value of ε is 0.1×W_std.

3. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: In step S2, the standard line width W_std is 0.4mm, the wide line width W_thick is 0.5mm, and the narrow line width W_thin is 0.3mm.

4. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: In step S2, the total number of wall rings N≥2. When N=2, even-numbered layers only include the outermost and innermost walls, with no intermediate walls.

5. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: The path center coordinates are calculated in step S3 as follows: When Layer_i is an odd number of layers, the center coordinates of the path in the kth loop are C_odd,k = D_outline - (k-1) × W_std - W_std / 2, where k = 1, 2, ..., N; When Layer_i is an even number of layers, the center coordinates of the path in the first loop are C_even,1=D_outline-W_thick / 2, the center coordinates of the path in the kth loop are C_even,k=D_outline-W_thick-(k-2)×W_std-W_thin / 2 (k=N), and the center coordinates of the path in the 2nd ≤ k≤N-1th loop are C_even,k=D_outline-W_thick-(k-2)×W_std-W_std / 2.

6. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: The formula for calculating the E-axis feed amount E_step of the extruder in step S4 is: E_step=(W×H) / (π×(D_fil / 2)²)×L_move, where D_fil is the diameter of the filament and L_move is the printhead movement distance.

7. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: The line width allocation for even-numbered layers in step S22 can be replaced as follows: the first ring is the outermost wall, with a line width of W_thin; the Nth ring is the innermost wall, with a line width of W_thick; and the second to N-1 rings are the middle walls, with a line width of W_std.

8. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: The diameter of the consumable filament, D_fil, is 1.75 mm, and the print layer height H ranges from 0.1 mm to 0.3 mm.

9. The 3D printing strength enhancement method based on the interlayer alternating variable linewidth slicing strategy according to claim 1, characterized in that: The method is compatible with various FDM printing consumables such as PLA, ABS, and PETG, and can be adapted to the melting characteristics and bonding performance of different consumables by adjusting the line width parameters.

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