Additive and subtractive manufacturing methods for porosity and narrow gap features

Abstract

The present invention belongs to the field of 3D printing technology and relates to a method for additive and subtractive manufacturing of features containing pores and narrow gaps, comprising: 1) obtaining a slice of a three-dimensional model and dividing the slice contour of the three-dimensional model slice into an outer contour and an inner hole; 2) identifying pore and narrow gap features in the outer contour and inner hole obtained in step 1); 3) generating a subtractive path for ultrafast laser subtractive operations based on the identified pore and narrow gap features; 4) combining the subtractive path obtained in step 3) and the additive path for laser additive operations obtained from the slice contour to obtain a printing path for the three-dimensional model slice; 5) executing the printing path to complete the additive and subtractive manufacturing of features containing pores and narrow gaps. The present invention provides a method for additive and subtractive manufacturing of features containing pores and narrow gaps that ensures the geometric accuracy and molding quality of 3D printing.

Description

Technical Field

[0001] The present invention belongs to the field of 3D printing technology and relates to an additive and subtractive forming printing method, and in particular to an additive and subtractive manufacturing method targeting pores and narrow gap features. Background Art

[0002] Selective laser melting (SLM) is an advanced manufacturing technology that uses lasers as a heat source and involves slicing three-dimensional models, followed by a bottom-up, layer-by-layer buildup process driven by fill paths. The sliced contours created by slicing the 3D model can contain numerous pores and narrow gaps. These features are likely to adhere to each other during printing, failing to achieve the desired geometric accuracy. This complicates post-processing of the finished part and affects the final quality.

[0003] For example, the invention application with application number 2021100033700.6 discloses a laser additive and subtractive manufacturing method for a large-scale sandwich straight groove annular component, establishes a three-dimensional model of a large-scale sandwich straight groove annular component suitable for laser melting deposition forming and laser cutting subtractive manufacturing; sets the laser melting deposition forming process parameters and laser cutting subtractive manufacturing process parameters in the slicing software platform; determines the growth direction, arranges the three-dimensional model of the large-scale sandwich straight groove annular component, and imports it into the set slicing software platform for slicing; performs additive and subtractive manufacturing under the protection of inert gas; after forming is completed, recovers the powder in the cabin, and anneals the unseparated annular component and substrate; uses wire cutting to separate the substrate and the annular part; and performs a final heat treatment on the annular component. The large-scale sandwich straight groove annular component obtained by the present invention has high performance, low surface roughness, and high forming accuracy, providing a new method for the final manufacturing of large-scale sandwich straight groove annular components. For another example, the invention application with application number 201910712621.5 discloses a near-net-shape forming method for composite manufacturing of fine workpieces based on laser additive and subtractive processes. Software is used to generate the structural parameters of a three-dimensional digital model layer by layer, and laser additive processing is performed. During the laser additive processing, ultrafast pulse laser subtractive processing is alternately performed to form a three-dimensional solid. The device includes a computer control device, a sealed forming chamber, an optical path selection system, and an inert gas shielding gas source. During additive processing, the computer control device controls the optical path selection system to select the laser from the additive laser emitter for laser additive processing. During subtractive processing, the optical path selection system controls the optical path selection system to select the ultrafast pulse laser emitted by the subtractive laser for ultrafast pulse laser subtractive processing.

[0004] However, ultrafast lasers have the characteristics of extremely short pulse width, extremely high peak power and extremely wide frequency range. They have many excellent properties in micromachining that traditional processes do not have. Using ultrafast lasers for fine processing of certain special structures in SLM technology will help to improve the overall forming accuracy of components. Summary of the Invention

[0005] In order to solve the above technical problems existing in the background technology, the present invention provides an additive and subtractive manufacturing method for pores and narrow gap features to ensure the geometric accuracy and forming quality of 3D printing.

[0006] In order to achieve the above object, the present invention adopts the following technical solutions:

[0007] A method for additive and subtractive manufacturing of pores and narrow gap features, characterized in that the method comprises the following steps:

[0008] 1) Obtaining a 3D model slice, and dividing the slice contour of the 3D model slice into an outer contour and an inner hole;

[0009] 2) Recognizing pore and narrow gap features in the outer contour and inner hole obtained in step 1);

[0010] 3) Generate a subtractive path for ultrafast laser subtractive operations based on the identified pore and narrow gap features;

[0011] 4) combining the subtractive path obtained in step 3) and the additive path for laser additive operation obtained from the slice profile to obtain a printing path for the 3D model slice;

[0012] 5) Execute the printing path to complete the additive and subtractive manufacturing of features containing pores and narrow gaps.

[0013] The above step 1) is specifically as follows: reading the binary STL model, performing equal thickness slicing operations, extracting the slice contours of each layer separately to obtain the slice contours of different layers, dividing the slice contours of each layer into multiple single-connected areas, and dividing the contour of each single-connected area into an outer contour and an inner hole.

[0014] The above step 2) is specifically:

[0015] 2.1) performing an inward bias operation on the inner hole according to the offset distance d, where the offset distance is the laser spot radius;

[0016] 2.2) Determine the result after biasing. If the biasing result is empty, the inner hole is a pore or narrow gap feature. If the biasing result is not empty, execute step 2.3).

[0017] 2.3) The biased result is reverse-biased by a distance of d + μ to obtain a similar original contour; determine whether the original contours of the inner hole are all within the similar original contour. If the original contours of the inner hole are all within the similar original contour, the current hole is a non-pore or narrow gap feature; if the original contours of the inner hole are not within the similar original contour, execute step 2.4);

[0018] 2.4) Perform a Boolean difference operation on the original contour of the inner hole and the quasi-original contour, and the resulting contour is the pore or narrow gap feature.

[0019] The above step 3) specifically includes: biasing the pore or narrow gap feature identified in step 2) outward according to the length of the ultrafast laser spot radius as a subtractive path.

[0020] In the above step 4), the scanning direction of the subtractive path is opposite to the scanning direction of the additive path.

[0021] The scanning mode of the printing path in the above step 4) is a raster scanning path, a reciprocating straight line path or a compound path.

[0022] The above step 5) is specifically: using laser to execute additive path to perform additive manufacturing, after completing additive manufacturing, using ultrafast laser to execute subtractive path to perform subtractive manufacturing, and completing additive and subtractive manufacturing of features containing pores and narrow gaps.

[0023] The advantages of the present invention are:

[0024] In order to eliminate the influence of pores and narrow gaps on the forming quality, the present invention proposes an additive and subtractive collaborative printing method that uses ultrafast laser to assist in correcting special contour features. First, the pore and narrow gap identification method proposed in this method can be used to obtain all the special structures of a slice contour. After obtaining these special structures, not only can they be used to generate subtractive paths, but the additive paths can also be corrected. After the subtractive path is obtained by this method, after the current layer additive process is completed, the ultrafast laser is used to perform subtractive operations on these features, which can improve the forming accuracy and forming quality of parts in pores and narrow gaps, saving production time and labor costs. The present invention can complete the preparation of complex and fine-structured parts with high precision and integration, overcoming the technical difficulties of traditional laser additive manufacturing such as low forming accuracy, high roughness, and the inability to prepare fine and complex cavities. DETAILED DESCRIPTION

[0025] The present invention mainly achieves the expected geometric accuracy and forming quality by identifying the pores and narrow gap features in the slice contour and performing subtraction through ultrafast laser. First, the slice contour of each layer is obtained through the three-dimensional model equal thickness layering algorithm, and the slice contour of each layer is divided into multiple single-connected areas. The contour of each single-connected area is divided into an outer contour and an inner hole. Then, the pores and narrow gap features are identified on the inner hole and saved in a specific data structure. The identified pores and narrow gap features are converted into a subtractive path according to the scanning order of the outer contour path counterclockwise or the inner hole clockwise. Then, the slice contour is planned for additive path, and the processing path for ultrafast laser subtraction and the printing path required for laser additive are obtained respectively. In the actual additive process, the laser is first used to perform the additive process of the current layer, and then the ultrafast laser is used to perform the subtractive process. Finally, post-processing is used to achieve the final forming quality.

[0026] The detailed implementation process of this method is as follows:

[0027] 1. 3D model slicing: First, read the binary STL model, perform equal thickness slicing according to the slice height input on the interface, and extract the slice contours of each layer for processing. Each slice contour is divided into multiple single-connected areas, and each connected area contour is divided into an outer contour and an inner hole, preparing data for the next step of pore and narrow gap identification processing.

[0028] 2. Pore and narrow gap identification:

[0029] 2.1) The inner hole is biased inward according to the offset distance d, where the offset distance d is the laser spot radius;

[0030] 2.2) Determine the result after biasing. If the biasing result is empty, the inner hole is a pore or narrow gap feature. If the biasing result is not empty, execute step 2.3).

[0031] 2.3) The offset result is reverse-biased by a distance of d + μ to obtain a similar original contour; determine whether the original contours of the inner hole are all within the similar original contour. If the original contours of the inner hole are all within the similar original contour, the current hole is a non-pore or narrow gap feature; if the original contour of the inner hole is not within the similar original contour, execute step 2.4); where μ is the error value considered to be determined;

[0032] 2.4) Perform a Boolean difference operation on the original contour of the inner hole and the quasi-original contour, and the resulting contour is the pore or narrow gap feature.

[0033] 3. Generate a subtractive path based on the identified pore or narrow gap features: The pore or narrow gap features identified in step 2) are offset outward according to the length of the ultrafast laser spot radius to serve as the subtractive path.

[0034] 4. Print path generation: Path planning is performed on the slice contour obtained by slicing. The path planning method mainly uses three methods: raster scanning path, reciprocating straight line path and compound path. After identifying the pores and narrow gaps, they are converted into subtractive paths. For example, the pores and narrow gap features on the inner contour are output as subtractive paths in a clockwise direction.

[0035] 5. Additive and subtractive implementation order: After obtaining all the data, first perform the additive process for the current layer, and then perform the subtractive process.

Claims

1. A method for additive and subtractive manufacturing of pores and narrow gap features, characterized by: The additive and subtractive manufacturing method for pore and narrow gap features includes the following steps: 1) Obtaining a 3D model slice, and dividing the slice contour of the 3D model slice into an outer contour and an inner hole; 2) Identify pores and narrow gap features in the inner pores obtained in step 1); specifically: 2.1) biasing the inner hole inwards by an offset distance d, where the offset distance d is the laser spot radius; 2.2) Determine the result after biasing. If the biasing result is empty, the inner hole is a pore or narrow gap feature. If the biasing result is not empty, execute step 2.3). 2.3) The offset result is reverse-biased by a distance of d + μ to obtain a quasi-original contour; μ is a determined error value; determine whether the original contours of the inner hole are all within the quasi-original contour; if the original contours of the inner hole are all within the quasi-original contour, then the current hole is not the pore or narrow gap feature; if the original contour of the inner hole is not within the quasi-original contour, execute step 2.4); 2.4) Performing a Boolean difference operation on the original contour of the inner hole and the quasi-original contour, the resulting contour is the pore or narrow gap feature; 3) Generate a subtractive path for ultrafast laser subtractive operations based on the identified pore and narrow gap features; 4) combining the subtractive path obtained in step 3) and the additive path for laser additive operation obtained from the slice profile to obtain a printing path for the 3D model slice; 5) Execute the printing path to complete additive and subtractive manufacturing.

2. The additive and subtractive manufacturing method for pore and narrow gap features according to claim 1, characterized in that: The step 1) specifically includes: reading the binary STL model, performing equal thickness slicing operations, extracting the slice contours of each layer separately to obtain slice contours of different layers, dividing the slice contours of each layer into multiple single-connected areas, and dividing the contour of each single-connected area into an outer contour and an inner hole.

3. The additive and subtractive manufacturing method for pore and narrow gap features according to claim 1, characterized in that: The step 3) specifically includes: biasing the pore or narrow gap feature identified in step 2) outward according to the length of the ultrafast laser spot radius as a subtractive path.

4. The additive and subtractive manufacturing method for pores and narrow gap features according to any one of claims 1 to 3, characterized in that: In step 4), the scanning direction of the subtractive path is opposite to the scanning direction of the additive path.

5. The additive and subtractive manufacturing method for pore and narrow gap features according to claim 4, characterized in that: The scanning mode of the printing path in step 4) is a raster scanning path, a reciprocating straight line path or a compound path.

6. The additive and subtractive manufacturing method for pore and narrow gap features according to claim 5, characterized in that: The step 5) specifically includes: using a laser to execute an additive path for additive manufacturing, and after completing the additive manufacturing, using an ultrafast laser to execute a subtractive path for subtractive manufacturing to complete the additive and subtractive manufacturing of features containing pores and narrow gaps.