阅读说明：本技术 基于送粉速度优化的激光增材制造工艺 (Laser additive manufacturing process based on powder feeding speed optimization ) 是由 张国瑜 唱丽丽 蒋士春 周文超 于 2021-10-31 设计创作，主要内容包括：本发明提供一种基于送粉速度优化的激光增材制造工艺,基于送粉增材制造打印的每一层沉积层的厚度的误差判断,并在此基础上选择相邻误差的残差平方和最小的组合,进行速度的修正,使得后续的打印过程中以修正的送粉速度进行送粉打印,减少每一层之间的误差。(The invention provides a laser additive manufacturing process based on powder feeding speed optimization, which is characterized in that the error of the thickness of each settled layer is judged based on the powder feeding additive manufacturing and printing, and on the basis, the combination of the minimum square sum of the residual errors of adjacent errors is selected to correct the speed, so that the powder feeding printing is carried out at the corrected powder feeding speed in the subsequent printing process, and the error between each layer is reduced.)

1. A laser additive manufacturing process based on powder feeding speed optimization is characterized by comprising the following steps:

performing layer-by-layer deposition by adopting a coaxial powder feeding mode according to preset laser additive manufacturing process parameters, wherein the laser additive manufacturing process parameters comprise laser working parameters and powder feeding process parameters, the laser working parameters comprise scanning interval, scanning speed and laser power, and the powder feeding process parameters comprise powder feeding speed and lap joint rate;

after the deposition of each layer is finished, detecting the distance between the processing head and the printing layer through a high-precision distance measuring sensor, and calculating the thickness of each layer of deposition layer based on the initial distance between the substrate and the processing head;

under the same powder feeding speed, the thickness of the deposition layer obtained correspondingly is as follows:

layer 1, thickness T1; layer 2, thickness T2; layer 3, thickness T3; layer 4, thickness T4; …, respectively; the nth layer with thickness Tn;

in which we want each layer to be the same in thickness, but it is difficult to achieve the exact same in the actual printing process, so after each layer is deposited, starting from layer 2, an error estimation is performed:

the sum of squared layer thickness residuals of layer 2 RSS2 ═ T2-T1²I.e. with T2 as the true value of the thickness, andt1 as the desired estimate; t2 is desired to be T1, but in practice it is difficult to achieve;

the sum of squares of the layer thicknesses of layer 3 and RSS3 ═ T3-T2²The real thickness value is T3, and the expected estimated value is T2;

the sum of squares of the layer thicknesses of layer 4 and RSS4 ═ T4-T3²The real thickness value is T4, and the expected estimated value is T3;

the sum of squared layer thickness residuals of the ith layer RSSi ═ Ti-1²Taking Ti as a thickness true value and taking Ti-1 as a desired estimated value;

taking a set window N as a reference, wherein N is more than or equal to 3, K is more than or equal to 10 in the results of the former K layers of settled layers, estimating and summing the square sum of the residual errors of the layer thicknesses, taking the output with the minimum summed result, selecting the minimum layer combination, calculating the average thickness value T 'of the minimum layer combination and the average thickness value T' of all settled layers up to the minimum layer combination, and then correcting the powder feeding speed according to the average thickness value T 'and T':

the corrected powder feeding speed is as follows: powder feeding speed (T '/T')

Then, during the printing process of each layer next to the minimum layer combination, the printing is performed at the corrected powder feeding speed, and the difference between the printing thicknesses of each layer is expected to be small enough, so that the thickness error of each layer is minimum, even 0, and the optimization of the whole printing process is realized.

Technical Field

The invention relates to the technical field of additive manufacturing, in particular to an additive manufacturing printing technology of metal materials such as titanium alloy and aluminum alloy, and particularly relates to a laser additive manufacturing process based on powder feeding speed optimization.

Background

The laser additive manufacturing is an advanced manufacturing technology which is widely researched and applied in recent years, metal materials are conveyed in a powder feeding mode or a powder feeding mode on the surface of a base material, a laser beam with high energy density is utilized to form a molten pool together with a thin layer on the surface of the base material, a metallurgically bonded cladding layer is formed, the manufacturing process of three-dimensional parts is converted into a two-dimensional stacking process in a layer-by-layer growth and deposition mode, the problems of difficulty and processing precision of the existing casting system on parts with complex structures can be solved, and the laser additive manufacturing has important application prospects in the fields of metal material forming, high polymer material forming and composite material forming.

At present, the outstanding problem restricting the large-scale popularization of laser cladding additive manufacturing is cladding efficiency and cladding layer quality, and therefore, in the prior art, a lot of researches are carried out on efficiency and quality, such as a broadband laser cladding technology, a double-beam/multi-beam cladding technology, a processing head height correction technology and the like.

In the related art, although powder is fed in a precise manner and cladding processing is performed with a laser processing head controllable with high precision, it is difficult to achieve very good uniformity in the height and quality of the obtained cladding layer, and thus, for example, CN111360367A proposes a highly automatic following arc additive manufacturing printing method, which detects the distance from the printed layer by a distance measuring sensor after single-layer printing is completed, determines torch height correction data according to the difference between the detected value of the distance and a set value, controls a multi-axis robot to adjust the printing height of a welding torch based on the torch height correction data, and controls the robot to perform motion program jumping in which the robot controls the welding torch to perform multi-axis printing on the last layer after printing is completed based on accumulated correction data. Accumulating the welding gun height correction data printed on each layer in the printing sequence, and controlling the robot to execute movement program jumping when the accumulated welding gun height correction data reaches a set threshold value; and interrupting the accumulation of the welding gun height correction data in response to the robot executing the movement program jump, and re-accumulating the welding gun height correction data from the jump target program to the first layer printing after the printing sequence is recovered.

The method aims to realize interruption of a planning printing program through the accumulated error of the height correction, perform one-time correction, insert a new layer of printing to eliminate the accumulated error, recover the height correction to the original state and avoid the continuation of the accumulated error. However, in the practical process of process application, the effect of interrupting the program can obtain better result verification in smaller parts (10-20 layers of deposited layers are required to be accumulated), but the effect cannot be determined in the process of processing large complex parts, such as 30 layers or more than 30 layers of deposited layers.

Drawings

Fig. 1-2 is a schematic diagram of estimation summation with a sliding window of 3 RSS settings.

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 this disclosure, aspects of the present invention are described with reference to the accompanying drawings, in which a number of illustrative embodiments are shown. Embodiments of the present disclosure 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.

The embodiment of the invention provides a laser additive manufacturing process based on powder feeding speed optimization, which comprises the following steps:

performing layer-by-layer deposition by adopting a coaxial powder feeding mode according to preset laser additive manufacturing process parameters, wherein the laser additive manufacturing process parameters comprise laser working parameters and powder feeding process parameters, the laser working parameters comprise scanning interval, scanning speed and laser power, and the powder feeding process parameters comprise powder feeding speed and lap joint rate;

after the deposition of each layer is finished, detecting the distance between the processing head and the printing layer through a high-precision distance measuring sensor, and calculating the thickness of each layer of deposition layer based on the initial distance between the substrate and the processing head;

under the same powder feeding speed, the thickness of the deposition layer obtained correspondingly is as follows:

layer 1, thickness T1; layer 2, thickness T2; layer 3, thickness T3; layer 4, thickness T4; …, respectively; the nth layer with thickness Tn;

in which we want each layer to be the same in thickness, but it is difficult to achieve the exact same in the actual printing process, so after each layer is deposited, starting from layer 2, an error estimation is performed:

the sum of squared layer thickness residuals of layer 2 RSS2 ═ T2-T1²The real thickness value is T2, and the expected estimated value is T1; t2 is desired to be T1, but in practice it is difficult to achieve;

the sum of squares of the layer thicknesses of layer 3 and RSS3 ═ T3-T2²The real thickness value is T3, and the expected estimated value is T2;

the sum of squares of the layer thicknesses of layer 4 and RSS4 ═ T4-T3²The real thickness value is T4, and the expected estimated value is T3;

the sum of squared layer thickness residuals of the ith layer RSSi ═ Ti-1²Taking Ti as a thickness true value and taking Ti-1 as a desired estimated value;

taking a set window N as a reference, wherein N is more than or equal to 3, K is more than or equal to 10 in the results of the former K layers of settled layers, estimating and summing the square sum of the residual errors of the layer thicknesses, taking the output with the minimum summed result, selecting the minimum layer combination, calculating the average thickness value T 'of the minimum layer combination and the average thickness value T' of all settled layers up to the minimum layer combination, and then correcting the powder feeding speed according to the average thickness value T 'and T':

the corrected powder feeding speed is as follows: powder feeding speed (T '/T')

Then, during the printing process of each layer next to the minimum layer combination, the printing is performed at the corrected powder feeding speed, and the difference between the printing thicknesses of each layer is expected to be small enough, so that the thickness error of each layer is minimum, even 0, and the optimization of the whole printing process is realized.

Taking titanium alloy as an example, in a better specific example and microstructure characterization, a printing result is compared with an existing printing result, and therefore the titanium alloy formed part obtained by the optimized printing method has better internal structure and high printing quality.

Although the present invention has been described with reference to the preferred embodiments, it is not intended to be limited thereto. Those skilled in the art can make various changes and modifications 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.