阅读说明：本技术 一种自动生成fdm零件最优成形方向的方法 (Method for automatically generating optimal forming direction of FDM (frequency division multiplexing) part ) 是由 黄美发 郑楠 张晗 于 2021-07-13 设计创作，主要内容包括：本发明提供了一种自动生成FDM零件最优成形方向的方法,这个方法包括两个步骤：首先,应用现有的基于面片聚类的方法,自动生成熔融沉积成型零件的不同备选成形方向；然后,运用多目标决策方法从有限个备选成形方向中选出最优成形方向,其中考虑了支撑体积、体积误差、表面粗糙度、成形时间和成形成本。本方法利用面片聚类和多目标决策方法,自动生成FDM零件最优成形方向的方法。(The invention provides a method for automatically generating an optimal forming direction of an FDM part, which comprises the following two steps of: firstly, automatically generating different alternative forming directions of fused deposition forming parts by applying the existing method based on surface patch clustering; then, an optimal forming direction is selected from a limited number of alternative forming directions by using a multi-objective decision-making method, wherein the supporting volume, the volume error, the surface roughness, the forming time and the forming cost are considered. The method utilizes a patch clustering and multi-target decision method to automatically generate the optimal forming direction of the FDM part.)

1. A method for automatically generating the optimal forming direction of an FDM part is characterized in that the optimal forming direction is automatically generated by using a two-step method, and comprises the following steps:

step 1, generating a small number of selectable forming directions from infinite possible directions;

and 2, selecting the optimal forming direction from the directions generated in the step 1.

2. A method for automatically generating an optimal forming direction for an FDM part of claim 1 wherein existing patch-based clustering methods are used to automatically generate different alternative forming directions for fused deposition modeling parts, generating a small number of alternative forming directions from an infinite number of possible directions.

3. The method for automatically generating the optimal forming direction of an FDM part of claim 1 wherein the optimal direction is selected from the generated solution and the selection is made by a multi-objective decision making process and an automatic selection method based on multi-objective decision making is developed.

4. A method for automatically generating an optimal forming direction for an FDM part in claim 3 wherein the multi-objective decision making process scheme first uses several estimation models of the part orientation factors considered to estimate the values of the factors in each alternative direction.

5. A method for automatically generating an optimal forming direction for an FDM part of claim 3 wherein the generation scheme uses a weighted sum model to calculate a summary of factors considered in each alternative direction.

6. The method for automatically generating an optimal forming direction for an FDM part of claim 3 wherein the generating scheme selects an optimal direction based on a calculated direction factor summary.

Technical Field

The invention relates to a fused deposition modeling technology in the field of additive manufacturing, in particular to a method for automatically generating an optimal forming direction of an FDM part.

Background

Additive manufacturing, commonly known as three-dimensional printing, refers to a set of processes for manufacturing three-dimensional parts by using three-dimensional model data as input and stacking special materials layer by layer in the manners of photocuring, jetting, sintering, melting, extruding, depositing, laminating and the like under the control of a computer.

Different from traditional 'material reduction' and 'material equal' manufacturing, additive manufacturing can directly manufacture parts through a material adding method based on a data model. Compared with the traditional manufacturing method, the additive manufacturing technology has higher efficiency, can manufacture complex parts which are difficult to process at low cost, can also be used for manufacturing products with heterogeneous materials, various colors and customized characteristics, and has wide application prospect in the aspects of aerospace, automobiles and biomedical treatment.

According to different working principles, the existing additive manufacturing process can be divided into seven categories, namely three-dimensional light curing, material spraying, adhesive spraying, powder bed melting, material extrusion, directional energy deposition and thin material lamination. Fused Deposition Modelling (FDM), one of the material extrusion processes, was developed successfully by Scott Crump in 1988 by american scholars. The material is typically a thermoplastic material such as wax, ABS, nylon, etc., supplied in filament form. The material is heated and melted in the spray head, the spray head moves along the section outline and the filling track of the part, meanwhile, the melted material is extruded out, and the material is rapidly solidified and is coagulated with the surrounding material.

Advantages of FDM in additive manufacturing:

1. the hot melt extrusion head system is simple in construction principle and operation, low in maintenance cost and safe in system operation;

2. the forming speed is low, and the product produced by the fused deposition method does not need a procedure of reprocessing of a scraper in SLA;

3. the wax-molded part prototype can be directly used for investment casting;

4. parts with any complexity can be molded, and the method is commonly used for molding parts with complex inner cavities, holes and the like;

5. the raw materials have no chemical change in the molding process, and the warping deformation of the finished piece is small;

6. the utilization rate of raw materials is high, and the service life of the materials is long.

Disclosure of Invention

The invention aims to provide a method for automatically generating the optimal forming direction of an FDM part, which is based on a patch clustering method and a multi-target decision method, uses a patch clustering algorithm to generate a small number of selectable forming directions from infinite possible directions, and then uses the multi-target decision method to select the optimal forming direction from generated alternative directions.

In order to achieve the above purpose, the method for automatically generating the optimal forming direction of the FDM part provided by the invention comprises the following steps.

Step 1, automatically generating different directions of fused deposition modeling parts by applying the existing method based on patch clustering, and generating a small number of selectable forming directions from infinite possible directions.

According to the step 1, further, dividing the surfaces of the STL model into different groups by using a hierarchical clustering algorithm, wherein the surfaces of the same group have similar normal vectors, calculating the alternative forming directions of each cluster, and merging and refining the calculated alternative forming directions of all clusters to obtain a certain number of meaningful alternative forming directions of parts.

Step 2, the method uses the free software processed by the Autodesk Meshmixer triangular grid, and inputs the geometric shape of the part STL model to estimate the supporting volume.

Step 3, estimating a volume error by using an estimation model, wherein the volume error is used for eliminating the total volume error of the FDM part in a given forming direction; the volume error cannot be eliminated, but its influence can be reduced by making appropriate forming directions and layer thicknesses.

According to the step 3, further, firstly, estimating the volume error of each surface in the STL model of the FDM part in the forming direction through geometric analysis; then, the total volume error of the part in the molding direction is obtained by calculating the sum of the volume errors of all the surfaces.

And 4, establishing an estimation model of the average surface roughness of the FDM part, wherein the model is used for predicting the average surface roughness of the FDM part in the given forming direction.

According to the step 4, further, firstly, estimating the roughness of each surface in the STL model of the FDM part in the forming direction by utilizing a linear regression function; then, the unit area roughness was calculated and taken as the average of the working surface roughness.

And 5, estimating the construction cost by using a universal estimation model.

According to step 5, further, according to the model, the construction cost includes a direct cost and an indirect cost, wherein the direct cost includes a material cost and an energy cost, that is, in a given construction direction, the total construction cost of an FDM part is the sum of the material cost, the energy cost and the indirect cost of the part in the molding direction.

And 6, calculating and selecting the optimal forming direction by using a weighting model.

According to step 6, further, first, each estimation factor value of the part is converted into a number from zero to one; then, normalizing the converted result; then determining the weight of the considered factor, wherein the weight of the considered factor is used for measuring the relative importance of the considered factor so as to determine the optimal forming direction; and finally, calculating the sum of the factors in each optional direction, wherein the highest sum is the optimal forming direction of the generated part.

It should be understood that all combinations of the foregoing concepts, as well as additional concepts described in greater detail below, may be considered as part of the inventive subject matter, provided that such concepts do not contradict each other; additionally, all combinations of claimed subject matter are considered a part of the present subject matter.

The foregoing and other aspects, embodiments and features of the present teachings can be more fully understood from the following description taken in conjunction with the accompanying drawings. Additional aspects of the present invention, such as features and/or advantages of exemplary embodiments, will be apparent from the description which follows, or may be learned by practice of specific embodiments in accordance with the teachings of the present invention.

Drawings

The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component that is illustrated in various figures may be represented by a like numeral. For purposes of clarity, not every component may be labeled in every drawing. Embodiments of various aspects of the present invention will now be described by way of example and with reference to the accompanying drawings, in which:

fig. 1 is a flowchart of the method for automatically generating the optimal forming direction of the FDM part of the present invention.

Fig. 2 shows an FDM machine of an additive manufacturing process to which the method of the present invention is applied.

Fig. 3 is a diagram of a limited number of alternative forming directions generated by the method of the present invention.

Detailed Description

In order to better understand the technical content of the present invention, specific embodiments are described below with reference to the accompanying drawings.

In the present invention, aspects of the present invention are described with reference to the attached drawings, in which a number of illustrated embodiments are shown, and which are not necessarily intended to include all aspects of the invention. It should be appreciated that the various concepts and embodiments described above, as well as those described in greater detail below, may be implemented in any of numerous ways, as the disclosed concepts and embodiments are not limited to any one implementation. In addition, some aspects of the present disclosure may be used alone, or in any suitable combination with other aspects of the present disclosure.

Referring to fig. 1, the exemplary embodiment of the present invention provides a method for automatically generating an optimal forming direction of an FDM part, including the following steps: step 1, automatically generating different directions of fused deposition molding parts by applying the existing method based on surface patch clustering, and generating a small number of selectable molding directions from infinite possible directions; step 2, using free software processed by a triangular grid of the Autodesk Meshmixer, and inputting the geometric shape of the part STL model to estimate the supporting volume; step 3, estimating the volume error by using an estimation model, wherein the estimation model is used for eliminating the total volume error of the FDM part in a given forming direction; step 4, establishing an estimation model of the average surface roughness of the FDM part, wherein the estimation model is used for predicting the average surface roughness of the FDM part in the given forming direction; step 5, estimating construction cost by using a general estimation model; and 6, calculating and selecting the optimal forming direction by using a weighting model.

Referring to figure 2, material is melted at high temperature by a thermal nozzle 3 through a supply of material 4 and extruded, the product 5 is printed layer by layer, the part of the print support structure 1 depending from the product 5 serves as a support, and a building platform and elevator 2 controls the lifting of the product on the platform to facilitate the printing layer by layer.

The embodiment is combined with fig. 3 to show a certain number of alternative forming directions generated by an STL model after the patch clustering method of step 1. Different directions of the fused deposition modeling part are automatically generated by applying the existing method based on patch clustering, a small number of optional forming directions are generated from infinite possible directions, and the method generates meaningful alternative forming directions by STL model input. And dividing the surfaces of the STL model into different groups by using a hierarchical clustering algorithm, wherein the surfaces of the same group have similar normal vectors, calculating the alternative forming directions of each cluster, and merging and refining the calculated alternative forming directions of all the clusters to obtain a certain number of meaningful alternative forming directions of the parts.

Although the present invention has been described with reference to preferred embodiments, it is not intended to be limited thereto. Those skilled in the art to which the invention relates will readily appreciate that various modifications and adaptations can be made without departing from the spirit and scope of the invention. Therefore, the protection scope of the present invention should be determined by the appended claims.