CN112364449B - Method for predicting surface roughness of additive manufactured part - Google Patents

Abstract

A method for predicting surface roughness of an additive manufactured part belongs to the technical field of additive manufacturing. The method for predicting the surface roughness of the additive manufactured part comprises the following steps: setting a placement angle and a slice layer thickness to obtain the inclination angles of the upper surface and the lower surface of each inclined area of the part, calculating the theoretical values of the upper surface roughness and the lower surface roughness of each inclined area of the part through a mathematical model of the surface roughness, judging whether the surface roughness of the part meets the design requirement, if so, manufacturing the part according to the current placement angle and slice layer thickness, and if not, adjusting the placement angle or slice layer thickness until the surface roughness of the part meets the design requirement, and manufacturing the part according to the current placement angle and slice layer thickness. The method for predicting the surface roughness of the additive manufactured part can predict the roughness of the part under different placing angles and different slice thicknesses, provides process guidance for SLM forming, reduces the workload and improves the working efficiency.

Description

A method for predicting surface roughness of additively manufactured parts

Technical field

The present invention relates to the field of additive manufacturing technology, and in particular to a method for predicting surface roughness of additively manufactured parts.

Background technique

Additive Manufacturing (AM) is based on the principle of discrete accumulation. It uses layered slicing software to slice the part model in layers. After data processing and CNC system control, the powder is melted, solidified and accumulated layer by layer, and finally completed. Rapid prototyping of parts. Selective laser melting (SLM) technology, as a newly developed additive manufacturing technology, has received widespread attention in recent years because it can directly process powder into components with complex shapes and high precision. As shown in Figure 1, during the selective laser melting process, under the protection of an inert atmosphere, a computer-controlled laser is used to selectively scan the powder bed, thereby selectively melting the powder particles and solidifying them into a solid layer, and then the previously formed solid layer is A layer of powder is spread on top, and the laser selectively scans the powder bed again, cyclically spreading the powder and selectively melting the powder with the laser until the part is processed.

SLM technology can theoretically form any complex metal parts, but in the actual production and processing process, it cannot guarantee the dimensional accuracy of the parts and is prone to problems such as high surface roughness. In order to reduce defects during SLM forming of specimens and improve the forming quality of the specimens, researchers added supports to improve the forming quality of the parts, and then removed the supports after forming. Although adding supports can improve the forming quality of some parts, for more complex specimens, the supports inside the formed specimens are difficult to remove, affecting the surface roughness of the parts and even affecting the assembly of subsequent parts.

For parts without support structures, according to the discrete principle of SLM forming, after slicing processing, the outer surface of the solid model is composed of a series of contour surfaces of slice layers, as shown in Figure 2. When there is a certain distance between the model surface and the part forming direction When the angle is adjusted, a step effect will occur. In the figure, the X axis represents the laser scanning direction, and the Z axis represents the growth direction of additive manufacturing. The longitudinal cross-sectional profile of the part is a circular curve, and the angle between the surface of the part and the forming direction changes continuously. The overhanging surface has a step shape. The step width w can be expressed as w=h cotα, h is the layer thickness, and α is the inclination angle, which is the angle between the inclined surface of the part (the left inclined surface of the part) and the horizontal plane (X-axis). , it can be seen that when the tilt angle is constant, the larger the layer thickness, the more obvious the step effect; when the layer thickness is constant, the smaller α is, the more obvious the step effect is. When α is 90°, the step width is 0, that is, the step effect disappears. . It can be seen from Figure 2 that the width of the step effect is jointly affected by the thickness of the slice layer and the tilt angle. The wider the width, the greater the surface roughness. Surface roughness refers to the unevenness of the tiny peaks and valleys on the surface of the formed sample, which is a microscopic geometric shape error. The flatter the sample surface, the smaller the surface roughness. Since SLM is a layer-by-layer superposition process based on 3D data model slicing processing, it is difficult to avoid the step effect between layers when forming the overhang sample, and the step effect directly affects the surface roughness.

As shown in Figure 3, sticky powder is also one of the main factors affecting surface roughness during the SLM process. When parts are sliced in layers, overhanging portions without solid support will appear. In the SLM process, in order to better form the metallurgical bond between layers, the laser penetration depth needs to be greater than the slice thickness. Therefore, powder sticking will occur on the formed parts, thus affecting the surface roughness. When the thickness of the slice layer is constant, the size of the inclination angle determines the size of the overhanging part without solid support. The smaller the inclination angle α, the smaller the constraint of the entity on the overhanging part. During the SLM forming process, due to the solid-liquid transition of the metal powder, Due to volume expansion and contraction, overhanging parts with a high degree of freedom are more likely to deform. In addition, the larger the overhanging part is, the more laser energy is directly irradiated on the powder bed. Due to the relatively poor thermal conductivity of the powder, the heat in the molten pool cannot be transferred to the surroundings in time, resulting in a longer liquid phase state in the molten pool and easy generation of Overhangs increase the roughness of the lower surface and affect the forming accuracy.

Contents of the invention

In order to solve the technical problems such as the step effect in SLM formed parts existing in the prior art, the present invention provides a method for predicting the surface roughness of additively manufactured parts, which can predict the surface roughness of parts under different placement angles and different slice layer thicknesses. Roughness provides process guidance for SLM forming, reduces workload and improves work efficiency.

In order to achieve the above objects, the technical solution of the present invention is:

A method for predicting surface roughness of additively manufactured parts, including the following steps:

S1. Set the placement angle of the parts for additive manufacturing and set the slice layer thickness;

S2. Obtain the inclination angle of the upper surface and the inclination angle of the lower surface of each inclined area on the part according to the placement angle;

S3. Calculate the theoretical value of the upper surface roughness of each inclined area of the part through the mathematical model of the upper surface roughness. At the same time, calculate the theoretical value of the lower surface roughness of each inclined area of the part through the mathematical model of the lower surface roughness;

The mathematical model of the upper surface roughness is:

In the formula, R _ai1 is the theoretical value of surface roughness on the i-th inclined area of the part, α _i1 is the inclination angle of the upper surface of the i-th inclined area of the part, h is the slice layer thickness, a _i1 is the i-th inclination of the part The width of the melt channel on the upper surface of the area; i is a positive integer greater than or equal to 1;

The mathematical model of the lower surface roughness is:

In the formula, R _ai2 is the theoretical value of surface roughness under the i-th inclined area of the part, α _i2 is the inclination angle of the lower surface of the i-th inclined area of the part, h is the slice layer thickness, a _i2 is the i-th inclination of the part The width of the molten pool bottom on the lower surface of the region;

S4. Determine whether the surface roughness of the part meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, that is, the theoretical value of the upper surface roughness of each inclined area of the part is less than or equal to the standard value of the upper surface roughness, and at the same time, the lower surface roughness of each inclined area of the part is If the theoretical values are respectively less than or equal to the standard value of the lower surface roughness, the parts will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, that is, the theoretical value of the upper surface roughness of one or more inclined areas of the part is greater than the standard value of the upper surface roughness, or the lower surface roughness of one or more inclined areas of the part is rough. If the theoretical value of the roughness is greater than the standard value of the lower surface roughness, then step S5 is executed;

S5. Keep the thickness of the slice layer unchanged, adjust the placement angle of the part, and repeat steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area of the part;

S6. Determine whether the surface roughness of the part obtained in step S5 meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, the part will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, proceed to step S7;

S7. Keep the placement angle of the part unchanged, reduce the thickness of the slice layer, and repeat steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area;

S8. Determine whether the surface roughness of the part obtained in step S7 meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, the part will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, step S5 is repeated until the surface roughness of all inclined areas of the part meets the design requirements, and the part is additively manufactured according to the current placement angle and slice layer thickness.

Further, in step S5, the specific method of adjusting the placement angle of the parts is to increase the angle of the smallest inclination angle among the inclination angle of the upper surface and the inclination angle of the lower surface in each inclined area of the part.

Further, in step S7, when reducing the thickness of the slice layer, the thickness of the slice layer is not less than the minimum particle size of the powder particles.

Beneficial effects of the present invention:

1) The present invention proposes a mathematical model of the upper surface roughness and a mathematical model of the lower surface roughness of SLM additively manufactured parts, which are used to predict the theoretical roughness values of the upper and lower surfaces of the part. The establishment of the mathematical model mainly considers the placement of the part. Three process parameters: angle, melt channel width, and slice layer thickness. Among them, the melt channel width is the diameter of the laser spot;

2) This invention can quickly predict the upper and lower surface roughness of SLM additive manufacturing parts based on the placement angle and slice layer thickness of the parts;

3) The present invention provides guidance for subsequent accuracy measurements, that is, by predicting the surface roughness of the part, it finds the component with the largest roughness value. The part only needs to detect the roughness value of this part, reducing workload, saving manpower and time, and improving work efficiency;

4) Based on the roughness requirements of the workpiece, the present invention estimates the theoretical roughness value through the upper and lower surface roughness mathematical models, and promptly adjusts the part placement angle and slice layer thickness to achieve the expected surface roughness, providing a basis for SLM additive manufacturing. Provide theoretical guidance for process parameter optimization.

Other features and advantages of the present invention will be described in detail in the detailed description below.

Description of the drawings

Figure 1 is a schematic diagram of existing selective laser melting technology;

Figure 2 is a schematic diagram of the step effect produced in the existing SLM forming process;

Figure 3 is a schematic diagram of the phenomenon of powder sticking to parts during the existing SLM forming process;

Figure 4 is a schematic diagram of the mathematical model of surface roughness on the part during the SLM forming process provided by the embodiment of the present invention;

Figure 5 is a schematic diagram of the mathematical model of the lower surface roughness of the part during the SLM forming process provided by the embodiment of the present invention;

Figure 6 is a schematic diagram of the implementation steps of adjusting the placement angle of parts and slice layer thickness provided by an embodiment of the present invention, wherein (a) is a schematic diagram of the initial placement angle of parts and slice layer thickness; (b) is a schematic diagram of parts adjustment Schematic diagram after placing the angle; (c) Schematic diagram after reducing the thickness of the slice layer of the part;

Figure 7 is a schematic diagram of the surface roughness corresponding to different inclination angles of the upper and lower surfaces of the part provided by the embodiment of the present invention;

FIG. 8 is a schematic diagram of the surface roughness corresponding to the area with the smallest inclination angle of the part provided by the embodiment of the present invention.

Detailed ways

The technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some of the embodiments of the present invention, rather than all of the embodiments.

In order to solve the problems existing in the existing technology, as shown in Figures 1 to 8, the present invention provides a method for predicting the surface roughness of additively manufactured parts, which includes the following steps:

S1. Set the placement angle of the additive manufacturing parts and set the slice layer thickness; specifically, according to the particle size range of the metal powder, select the slice layer thickness within the particle size range;

S2. Obtain the inclination angle of the upper surface and the inclination angle of the lower surface of each inclined area of the part according to the placement angle; specifically, by adjusting the placement angle of the part, the inclination angle of the upper surface of each inclined area of the part is changed. The inclination angle of the lower surface of each inclined area of the part;

S3. Calculate the theoretical value of the upper surface roughness of each inclined area of the part through the mathematical model of the upper surface roughness. At the same time, calculate the theoretical value of the lower surface roughness of each inclined area of the part through the mathematical model of the lower surface roughness;

The mathematical model of upper surface roughness is:

In the formula, R _ai1 is the theoretical value of surface roughness on the i-th inclined area of the part, α _i1 is the inclination angle of the upper surface of the i-th inclined area of the part, h is the slice layer thickness, a _i1 is the i-th inclination of the part The width of the melt channel on the upper surface of the area; i is a positive integer greater than or equal to 1;

The mathematical model of the following surface roughness is:

In the formula, R _ai2 is the theoretical value of surface roughness under the i-th inclined area of the part, α _i2 is the inclination angle of the lower surface of the i-th inclined area of the part, h is the slice layer thickness, a _i2 is the i-th inclination of the part The width of the molten pool bottom on the lower surface of the region;

S4. Determine whether the surface roughness of the part meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, that is, the theoretical value of the upper surface roughness of each inclined area of the part is less than or equal to the standard value of the upper surface roughness, and at the same time, the lower surface roughness of each inclined area of the part is If the theoretical values are respectively less than or equal to the standard value of the lower surface roughness, the parts will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, that is, the theoretical value of the upper surface roughness of one or more inclined areas of the part is greater than the standard value of the upper surface roughness, or the lower surface roughness of one or more inclined areas of the part is rough. If the theoretical value of the roughness is greater than the standard value of the lower surface roughness, then step S5 is executed;

S5. Keep the thickness of the slice layer unchanged, adjust the placement angle of the part, and repeat steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area of the part;

S6. Determine whether the surface roughness of the part obtained in step S5 meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, the part will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, proceed to step S7;

S7. Keep the placement angle of the part unchanged, reduce the thickness of the slice layer, and repeat steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area;

S8. Determine whether the surface roughness of the part obtained in step S7 meets the design requirements:

If the surface roughness of all inclined areas of the part meets the design requirements, the part will be additively manufactured according to the current placement angle and slice layer thickness;

If the surface roughness of the part does not meet the design requirements, step S5 is repeated until the surface roughness of all inclined areas of the part meets the design requirements, and the part is additively manufactured according to the current placement angle and slice layer thickness.

In the present invention, the specific way to determine whether the surface roughness of the part meets the design requirements is to compare the theoretical value of the upper surface roughness of each inclined area of the part with the standard value of the upper surface roughness (according to the drawing requirements). At the same time, Compare the theoretical value of the lower surface roughness of each inclined area of the part with the standard value of the lower surface roughness (according to the drawing requirements); if the theoretical value of the upper surface roughness of each inclined area of the part is respectively less than or equal to the upper surface roughness The standard value of the lower surface roughness, and at the same time, the theoretical value of the lower surface roughness of each inclined area of the part is less than or equal to the standard value of the lower surface roughness, that is, the surface roughness of all inclined areas of the part meets the design requirements; if a certain part of the part Or the theoretical value of the upper surface roughness of multiple inclined areas is greater than the standard value of the upper surface roughness, or the theoretical value of the lower surface roughness of one or more inclined areas of the part is greater than the standard value of the lower surface roughness, that is It is said that as long as one of the theoretical values of surface roughness in all inclined areas of the part is greater than the standard value, that is, the surface roughness of the part does not meet the design requirements.

Specifically, in step S5, the specific way to adjust the placement angle of the part is to increase the angle of the smallest inclination angle among the inclination angle of the upper surface and the inclination angle of the lower surface in each inclined area of the part.

Specifically, in step S7, when reducing the slice layer thickness, the slice layer thickness is not less than the minimum particle size of the powder particles. In the SLM forming process, the slice layer thickness is an important parameter to ensure the surface roughness of the part in addition to the tilt angle. According to the mathematical model of the upper and lower surface roughness of the part, it can be seen that when other parameters are determined, the smaller the thickness of the slice layer, the smaller the surface roughness. Therefore, after the inclination angle of the part is determined, the slice layer thickness should be selected as small as possible according to the particle size of the metal powder, which will help reduce the surface roughness of the part after SLM forming. In other words, when selecting the slice layer thickness, The thickness of the slice layer should not be less than the minimum particle size of the powder particles. For example, the particle size range of TC4 powder is 20-53μm, then the thickness of the slice layer should be selected between 20-53μm, and the minimum should be no less than 20μm. However, under the condition of ensuring surface roughness, the slice layer thickness should be as large as possible to increase the processing speed.

The prediction method in the present invention can be executed in additive manufacturing planning software to achieve prediction of surface roughness of additively manufactured parts.

The principle of the present invention is as follows:

As shown in Figure 4, it is a schematic diagram of the mathematical model of surface roughness on the part. Selective laser melting is a process in which adjacent melt channels of the same layer overlap each other, and adjacent layers accumulate each other, ultimately achieving rapid prototyping of the part. Based on the principle of SLM forming and combined with the characteristics of laser energy density distribution, the longitudinal section of each melt channel is simplified into an arc, and the highest point of the melt channel, that is, the highest point in the Z coordinate direction of each arc, is the center point of the laser , the melt channel width a _i1 is the spot diameter, and a mathematical model of the surface roughness on the part is established;

As shown in Figure 5, it is a schematic diagram of the mathematical model of surface roughness under the part. During the layered slicing process of the part, there will be overhanging parts without physical support. During the laser scanning process, powder sticking and edge warping are prone to occur. The situation will affect the lower surface forming angle and surface roughness. Simplify the longitudinal section of the bottom of the molten pool into an arc, and the width a _i2 of the bottom of the molten pool is the spot diameter, and establish a mathematical model of the surface roughness of the part;

As shown in Figure 6, the implementation steps for adjusting the placement angle of parts and slice thickness are:

As shown in Figure 6(a), set the placement angle of the part, obtain the inclination angle of the upper surface of a certain inclined area of the part as β, and set the slice layer thickness as h ₁ ; calculate the part through the mathematical model of the upper surface roughness of the part The theoretical value R _a1 of the upper surface roughness of a certain inclined area. If the theoretical value R _a1 is greater than the standard value Ra, that is, the surface roughness of the part does not meet the design requirements. As shown in Figure 6(b), keep the slice layer thickness as h ₁ remains unchanged, adjust the placement angle of the part to increase the inclination angle of the upper surface of a certain inclined area of the part, and obtain the inclination angle of the upper surface as α, (α﹥β), through the mathematics of the upper surface roughness of the part The model calculates the theoretical value R _a2 of the upper surface roughness of a certain inclined area of the part. If the theoretical value R _a2 is greater than the standard value Ra, that is, the surface roughness of the part does not meet the design requirements, as shown in Figure 6(c), keep the pendulum Keeping the angle constant, that is, keeping the inclination angle α of the upper surface unchanged, reducing the thickness of the slice layer to h ₂ , (h ₂ ﹤h ₁ ), and calculating the upper surface roughness of a certain inclined area of the part through the mathematical model of the upper surface roughness of the part. The theoretical value of surface roughness R _a3 . If the theoretical value R _a3 is less than the standard value Ra, the part will be additively manufactured according to the current placement angle (that is, the inclination angle α) and the slice layer thickness h ₂ .

As shown in Figure 7, it is the corresponding surface roughness at different tilt angles of the upper and lower surfaces of the part. When the thickness of the slice layer is fixed, the corresponding inclination angles of the two points A and B on the upper surface are α ₁ and α ₂ respectively. Compare the surface roughness R _a1 and R _a2 of the two areas (both calculated by the mathematics of the upper surface roughness of the part of the present invention). Calculated from the model), it can be seen that as the tilt angle decreases, the surface roughness increases significantly; the tilt angles corresponding to points C and D on the lower surface are α ₃ and α ₄ respectively. Compare the surface roughness R _a3 and R of the two areas. _a4 (all calculated from the mathematical model of surface roughness under the part of the present invention) shows that the greater the inclination angle, the smaller the surface roughness in this area. In summary, whether it is the upper surface or the lower surface of the part, the smaller the inclination angle, the greater the surface roughness. Combining the schematic diagram and the mathematical model of the upper and lower surface roughness of the part, it can be concluded that when the tilt angle of the sample is closer to 90°, the surface roughness becomes smaller. When the tilt angle reaches 90°, the theoretical surface roughness is zero.

When the process parameters and tilt angle are the same, according to the mathematical model of the upper and lower surface roughness of the part, the roughness of the upper surface will be better than the roughness of the lower surface. For example, when the slice layer thickness is 50 μm, the spot diameter is 100 μm, and the tilt angle is 30°, based on the mathematical model of the upper and lower surface roughness of the part, the roughness of the upper surface is 25 μm and the roughness of the lower surface is 34 μm. Therefore, when forming complex structural parts or internal cavities, in order to ensure the surface roughness of this area, it should be formed as the upper surface.

During the forming process of each sample, the slice thickness is the same. Therefore, the area with the smallest tilt angle in the part corresponds to the largest surface roughness. Therefore, in actual work, after optimizing the tilt angle and slice layer thickness, the surface roughness of the area with the smallest tilt angle can be calculated through the mathematical model of the upper and lower surface roughness of the part to calculate the maximum roughness of the entire part. If this area If the surface roughness meets the requirements, other areas will also meet the requirements. It can be seen that the prediction of surface roughness provides help in guiding subsequent inspection work, reducing workload and improving work efficiency. As shown in Figure 8, the corresponding inclination angle at point A is α. For similar parts, the smaller the angle between the tangent line at each position and the X-axis, the greater the surface roughness here. If the part is at The surface roughness corresponding to the minimum inclination angle can meet the requirements, that is, the surface roughness of the part meets the requirements.

Although the embodiments of the present invention have been shown and described, those of ordinary skill in the art will appreciate that various changes, modifications, substitutions and variations can be made to these embodiments without departing from the principles and purposes of the invention. The scope of the invention is defined by the claims and their equivalents.

Claims (3)

1. The method for predicting the surface roughness of the additive manufactured part is characterized by comprising the following steps of:

s1, setting a placement angle of additive manufacturing of parts and setting a slice thickness;

s2, obtaining the inclination angles of the upper surfaces and the lower surfaces of all inclination areas on the part according to the placement angles;

s3, calculating theoretical values of the upper surface roughness of each inclined area of the part through a mathematical model of the upper surface roughness, and simultaneously calculating theoretical values of the lower surface roughness of each inclined area of the part through a mathematical model of the lower surface roughness;

the mathematical model of the upper surface roughness is as follows:

wherein R is _ai1 Upper table for ith inclined area of partTheoretical value of surface roughness, alpha _i1 The inclination angle of the upper surface of the ith inclination area of the part, h is the slice thickness, a _i1 The width of the melt channel is the upper surface of the ith inclined area of the part; i is a positive integer greater than or equal to 1;

the mathematical model of the lower surface roughness is:

wherein R is _ai2 Is the theoretical value of the lower surface roughness of the ith inclined area of the part, alpha _i2 The inclination angle of the lower surface of the ith inclination area of the part, h is the slice thickness, a _i2 A bottom width of the molten pool for the lower surface of the ith inclined area of the part;

s4, judging whether the surface roughness of the part meets the design requirement or not:

if the surface roughness of all inclined areas of the part meets the design requirement, namely, the theoretical value of the upper surface roughness of each inclined area of the part is respectively smaller than or equal to the standard value of the upper surface roughness, and meanwhile, the theoretical value of the lower surface roughness of each inclined area of the part is respectively smaller than or equal to the standard value of the lower surface roughness, the part is additionally manufactured according to the current placement angle and the slice layer thickness;

if the surface roughness of the part does not meet the design requirement, that is, the theoretical value of the upper surface roughness of one or more inclined areas of the part is greater than the standard value of the upper surface roughness, or the theoretical value of the lower surface roughness of one or more inclined areas of the part is greater than the standard value of the lower surface roughness, executing step S5;

s5, keeping the thickness of the slice layer unchanged, adjusting the placement angle of the part, and repeating the steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area;

s6, judging whether the surface roughness of the part obtained in the step S5 meets the design requirement:

if the surface roughness of all inclined areas of the part meets the design requirement, the part is manufactured in an additive mode according to the current placement angle and the slice layer thickness;

if the surface roughness of the part does not meet the design requirement, executing a step S7;

s7, keeping the placing angle of the part unchanged, reducing the thickness of the slice layer, and repeating the steps S2 and S3 to obtain the theoretical value of the upper surface roughness of each inclined area of the part and the theoretical value of the lower surface roughness of each inclined area;

s8, judging whether the surface roughness of the part obtained in the step S7 meets the design requirement:

if the surface roughness of all inclined areas of the part meets the design requirement, the part is manufactured in an additive mode according to the current placement angle and the slice layer thickness;

if the surface roughness of the part does not meet the design requirement, repeating the step S5 until the surface roughness of all the inclined areas of the part meets the design requirement, and additively manufacturing the part according to the current placement angle and slice layer thickness.

2. The method for predicting the surface roughness of an additive manufactured part according to claim 1, wherein in the step S5, the specific way of adjusting the placement angle of the part is: the angle of the smallest inclination angle among the inclination angles of the upper surfaces and the lower surfaces of the respective inclination areas of the part is increased.

3. The method according to claim 1, wherein in the step S7, the slice layer thickness is not smaller than the minimum particle diameter of the powder particles when the slice layer thickness is reduced.