WO2021004185A1

WO2021004185A1 - Method for gradient regulation and control of technological parameter in additive manufacturing process

Info

Publication number: WO2021004185A1
Application number: PCT/CN2020/092988
Authority: WO
Inventors: 周文超; 唱丽丽; 邢飞; 王文博; 吴江陵
Original assignee: 南京中科煜宸激光技术有限公司
Priority date: 2019-07-09
Filing date: 2020-05-28
Publication date: 2021-01-14
Also published as: CN110340358A; CN110340358B

Abstract

Provided is a method for gradient regulation and control of a technological parameter in an additive manufacturing process. The method comprises the following steps: slicing a model and layering same, filling a laser scanning path of each layer, and completing additive manufacturing of a first layer of the model at a power P1 to obtain the temperature T1 of a point A1; completing additive manufacturing of a second layer of the model at a power P2, wherein P2 = P1, and the temperature T2 of a point A2 is obtained; determining the temperature value between the two adjacent layers, wherein if T2 ≠ T1, the laser power is adjusted to enable P3 = P2-(T2-T1)*△P, and then carrying out a printing procedure of a next layer at a power P3, wherein △P is an interlayer laser power increment; and repeating the above-mentioned steps until T(n) = T(n-1), and obtaining a stable laser power parameter Pn at that moment, wherein Pn = P(n-1)-(T(n-1)-T(n-2))*△P, and Pn is used as the final laser processing parameter to complete workpiece printing. The method provided can solve the problem of unstable formation brought about by the cumulative effect of heat in a layer-by-layer printing process in the existing laser additive manufacturing technology.

Description

Method for gradient control of technological parameters in additive manufacturing process

Technical field

The invention relates to the technical field of additive manufacturing, in particular to a method for gradient control of process parameters in an additive manufacturing process.

Background technique

Metal additive manufacturing technology is mainly realized by laser metal deposition, which is different from the traditional subtractive manufacturing-metal turning and iso-material manufacturing-casting technology. Metal additive manufacturing uses laser or electron beam as the heat source, in the base material At the same time, the powder material is directly delivered to the laser molten pool through the powder feeding system, and the metal powder is melted by laser energy. With the movement of the laser spot, the molten powder enters the molten pool and solidifies and forms metallurgy with the base material. Combine, build 3D model part entities through layer upon layer accumulation.

This layer-by-layer manufacturing method can theoretically produce workpieces of any shape. It can automatically, quickly, directly and accurately convert the three-dimensional design in the computer into a physical model, and even directly manufacture parts or molds, thus effectively To shorten the product development cycle is a true digital and intelligent forming method.

However, with this layer-by-layer additive manufacturing technology, as the height of the printing layer increases, the heat accumulation effect occurs, and the temperature of the formed area will increase layer by layer. The process personnel need to change the processing parameters layer by layer to reduce the laser energy input to make The temperature change of the molten pool caused by the heat accumulation effect reaches a dynamic equilibrium. At present, the adjustment of the process parameters of this additive manufacturing process is mostly based on the experience of the process personnel, and it is difficult to achieve the layer-by-layer gradient control of the parameters of different material parts.

Summary of the invention

The purpose of the present invention is to provide a method for gradient control of process parameters of an additive manufacturing process, which can overcome the problem of laser forming instability caused by the thermal accumulation effect of the layer-by-layer printing process in the existing laser additive manufacturing technology.

In order to achieve the above-mentioned objective, the method for gradient control of process parameters in the additive manufacturing process adopted by the present invention includes:

Step 1: Slice the model into layers and fill in the laser scanning path of each layer, complete the additive manufacturing of the first layer of the model with power P1, and use the three-dimensional finite element method to determine the heat conduction equation at the starting point A1 of the first layer of the model to obtain point A1 The temperature T1;

Step 2: Complete the additive manufacturing of the second layer of the model with the power P2, where P2=P1, use the three-dimensional finite element method to determine the heat conduction equation at the starting point A2 of the second layer of the model, and obtain the temperature T2 of the A2 point;

Step 3: Determine the temperature between two adjacent layers. If T2≠T1, adjust the laser power so that P3=P2-(T2-T1)*△P, and use the laser power P3 to print the next layer, where △ P is the increment of laser power between layers. Use the three-dimensional finite element method to determine the heat conduction equation at point A3 at the starting point of the third layer of the model, and obtain the temperature T3 at point A3;

Step 4: Repeat steps 2 and 3 until T(n)=T(n-1), at this time a stable laser power parameter Pn is obtained, Pn=P(n-1)-(T(n-1)- T(n-2))*△P, and use Pn as the final laser processing parameter to complete the workpiece printing.

Further, in the first step, when the temperature of the point An of the model is calculated by the three-dimensional finite element method, the thickness of the model is n layers.

Further, in the first step, after the model slices are layered and the laser scanning path of each layer is filled, the laser processing time t(n) of each layer is calculated. When the temperature of the model An point is calculated by the three-dimensional finite element method, the model heating time is n-layer cumulative heating time.

Further, the horizontal position An of the starting point of the printing procedure of each layer is the same position.

Further, the position of the horizontal position An of the starting point of the printing procedure of each layer is randomly selected.

Further, the horizontal position An of the starting point of each layer of the printing program relative to the coordinate position of the model is readable.

Further, this method is suitable for additive manufacturing process, the material layer used for processing does not involve the change of material composition between layers, and other processing parameters except power should remain unchanged;

Further, the range of the laser power increment ΔP between layers is 0-P1.

The beneficial effect of the present invention is that the method adopted by the present invention can calculate the layer-by-layer temperature of the forming part through three-dimensional finite element simulation calculation, and compensate the parameters of each printing layer through the simulation calculation, and finally obtain stable laser processing. Parameters, so as to realize the gradient control of the process parameters of the additive manufacturing process, and solve the problem of laser forming instability caused by the thermal accumulation effect of the layer-by-layer printing process in the existing laser additive manufacturing technology.

It should be understood that all combinations of the aforementioned concepts and the additional concepts described in more detail below can be regarded as part of the inventive subject matter of the present disclosure as long as such concepts are not mutually contradictory. In addition, all combinations of the claimed subject matter are regarded as part of the inventive subject matter of the present disclosure.

The foregoing and other aspects, embodiments and features of the teachings of the present invention can be more fully understood from the following description with reference to the accompanying drawings. Other additional aspects of the present invention, such as the features and beneficial effects of the exemplary embodiments, will be apparent in the following description, or learned from the practice of the specific embodiments taught by the present invention.

Description of the drawings

The drawings are not intended to be drawn to scale. In the drawings, each identical or nearly identical component shown in each figure may be represented by the same reference numeral. For clarity, not every component is labeled in every figure. Now, embodiments of various aspects of the present invention will be described by way of examples and with reference to the accompanying drawings, in which:

Fig. 1 is a schematic flow chart of the method for gradient control of process parameters in an additive manufacturing process of the present invention.

Fig. 2 is a schematic diagram of a part sample prepared by a method of gradient control of process parameters of an additive manufacturing process.

Figure 3 is a metallographic analysis photo of the part A in the part sample shown in Figure 2.

Fig. 4 is a metallographic analysis photo at B in the part sample block shown in Fig. 2.

Detailed ways

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

In this disclosure, various aspects of the present invention are described with reference to the accompanying drawings, in which many illustrated embodiments are shown. The embodiments of the present disclosure are not necessarily intended to include all aspects of the present invention. It should be understood that the various concepts and embodiments introduced above, as well as those described in more detail below, can be implemented in any of many ways, because the concepts and embodiments disclosed in the present invention are not Limited to any implementation. In addition, some aspects disclosed in the present invention can be used alone or in any appropriate combination with other aspects disclosed in the present invention.

As shown in FIG. 1, the implementation process of the method for gradient control of process parameters in an additive manufacturing process according to a preferred embodiment of the present invention includes:

Step 1: Slice the model into layers and fill the laser scanning path of each layer, and complete the additive manufacturing of the first layer of the model with power P1. Use the three-dimensional finite element method to calculate the heat conduction equation at the starting point A1 of the model S1 to obtain the temperature of A1 point T1;

Step 2: Complete the additive manufacturing of the second layer of the model with the power P2=P1, use the three-dimensional finite element method to calculate the heat conduction equation at the starting point A2 of the model S2, and obtain the temperature T2 at the point A2;

Step 3: Determine the temperature between two adjacent layers. If T2≠T1, adjust the laser power P3=P2-(T2-T1)△P, and use the laser power P3 to print the next layer;

In combination with the above exemplary implementation of the present invention, the method of the present invention aims to continuously determine the temperature of the starting point by establishing a thermodynamic heat conduction equation in the initial stage of additive manufacturing printing, and adjust the laser power based on whether the temperature is stable or changing, so as to solve the problem. The problem of unstable laser forming caused by the heat accumulation effect of the layer printing process.

Wherein, in the first step, the thickness of the model when calculating the temperature of the point An of the model by using the three-dimensional finite element method is n layers.

In this embodiment, after the model slice is layered and the laser scanning path of each layer is filled, the laser processing time t(n) of each layer can be calculated. When using the three-dimensional finite element method to calculate the temperature of the model An point, the model heating time is n-layer cumulative heating time.

In this embodiment, the horizontal position An of the starting point of the printing procedure for each layer can be the same position or randomly selected, and its coordinate position relative to the model is readable, because the starting point of the printing procedure for each layer is not It is fixed, and as the height increases, the model structure may change. Therefore, the selection of the An point of each layer of the model can be set to the same position or a random position relative to the model according to the different starting points of the program of each layer.

In this embodiment, the method is suitable for the additive manufacturing process, the material layer used for processing does not involve changes in material composition between the layers, and other processing parameters other than power should remain unchanged, so that the purpose is to control Material properties and other processing parameters remain unchanged, achieving the purpose of controlling a single variable and making power control more precise.

In this embodiment, the value range of the interlayer laser power increment ΔP can be between 0 and P1.

Fig. 2 is a schematic diagram of a part printed by the process parameter adjustment method of the present invention, and Figs. 3-4 are schematic diagrams of partial metallographic analysis photos. In this embodiment, the sample is prepared along the printing direction, using the additive manufacturing process parameter gradient control method to adjust the power layer by layer. The laser power is 700W in the A region of the starting layer, and the laser power is increased layer by layer to 1100W in the B region. , To obtain a stable bath temperature. Observation of the metallographic structure of the prepared sample block shows that when the laser power is low, the laser energy input is low, and there are many pore defects inside the sample block. As the laser energy increases layer by layer, the number of defects changes from area A 61 voids are visible to the naked eye above 10μm, and the voids are basically disappeared in the B area, and the void defects are significantly reduced until they disappear completely. The effect of the gradient control of process parameters is significant.

Although the present invention has been disclosed as above in preferred embodiments, it is not intended to limit the present invention. Those with ordinary knowledge in the technical field of the present invention can make various changes and modifications without departing from the spirit and scope of the present invention. Therefore, the protection scope of the present invention shall be subject to what is defined in the claims.

Claims

A method for gradient control of process parameters in an additive manufacturing process is characterized in that it comprises the following steps:

Step 1: Slice the model into layers and fill in the laser scanning path of each layer, complete the additive manufacturing of the first layer of the model with power P1, and use the three-dimensional finite element method to determine the heat conduction equation at the starting point A1 of the first layer of the model to obtain point A1 The temperature T1;

Step 2: Complete the additive manufacturing of the second layer of the model with the power P2, where P2=P1, use the three-dimensional finite element method to determine the heat conduction equation at the starting point A2 of the second layer of the model, and obtain the temperature T2 of the A2 point;

Step 3: Determine the temperature between two adjacent layers. If T2≠T1, adjust the laser power P, and use the laser power P3 to print the next layer, where P3=P2-(T2-T1)*△P, △P is the increment of laser power between layers, where △P ranges from 0 to P1; use the three-dimensional finite element method to determine the heat conduction equation at the starting point A3 of the third layer of the model, and obtain the temperature T3 at A3;

Step 4: Repeat steps 2 and 3 until T(n)=T(n-1), at this time a stable laser power parameter Pn is obtained, Pn=P(n-1)-(T(n-1)- T(n-2))*△P, and use Pn as the final laser processing parameter to complete the workpiece printing.
The method for controlling the gradient of process parameters of the additive manufacturing process according to claim 1, wherein in the step 1, when the temperature of the point An of the model is calculated by the three-dimensional finite element method, the thickness of the model is n layer height.
The method of claim 1, wherein the process parameter gradient control method of the additive manufacturing process is characterized in that, in the step one, after the model is sliced into layers and the laser scanning path of each layer is filled, the laser processing time t(n ), when using the three-dimensional finite element method to calculate the temperature at point An of the model, the model heating time is the cumulative heating time of n layers.
The method for gradient control of process parameters in an additive manufacturing process according to claim 1, wherein the horizontal position An of the starting point of the printing procedure of each layer is the same position.
The method for gradient control of process parameters in an additive manufacturing process according to claim 1, wherein the position of the horizontal position An of the starting point of each layer of the printing program is randomly selected.
The method for gradient control of process parameters in an additive manufacturing process according to claim 4 or 5, wherein the horizontal position An of the starting point of each layer of the printing program is readable relative to the coordinate position of the model.
The method for gradient control of process parameters in an additive manufacturing process according to claim 1, characterized in that the method is suitable for the additive manufacturing process, and the material layer used for processing does not involve changes in material composition between layers, and except for power Other processing parameters should remain unchanged.