CN114559055A

CN114559055A - 3D printing method

Info

Publication number: CN114559055A
Application number: CN202210233756.5A
Authority: CN
Inventors: 韩向阳; 刘普祥; 魏盼
Original assignee: Shenzhen Huayang New Material Technology Co ltd
Current assignee: Shenzhen Huayang New Material Technology Co ltd
Priority date: 2022-03-10
Filing date: 2022-03-10
Publication date: 2022-05-31
Anticipated expiration: 2042-03-10
Also published as: CN114559055B

Abstract

The invention relates to the technical field of metal additive manufacturing, and discloses a 3D printing method for solving the technical problem of large stress of a formed part with large area or large sectional area change, which comprises the steps of defining a laser beam scanning line to be distributed in a serpentine line in a contour area, and scanning line by line; in the core area, laser scanning lines are defined to be arranged in a square shape; scanning the entity outline region once line by line from left to right and from bottom to top with a fixed laser beam diameter, preset power and speed; increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning two disjoint square shapes in the entity core area; and recovering the original diameter of the laser beam, scanning for a preset number of times along the outline of the entity, and performing powder paving action after the scanning is finished. The scanning line shape and the scanning rotation mode are set, the length of the scanning line is reduced, heat concentration is reduced through subarea and sectional scanning, the stress concentration coefficient is reduced, and deformation and cracking are prevented.

Description

3D printing method

Technical Field

The invention relates to the technical field of metal additive manufacturing, in particular to a 3D printing method.

Background

The selective laser melting and forming technology has the technical characteristics of rapid melting and solidification. When a large-area part or a product with large sectional area change is formed, the existing scanning mode is easy to generate high stress. Meanwhile, the scanning time is long, and the forming efficiency is low.

Disclosure of Invention

The invention aims to provide a 3D printing method to solve the technical problem of large stress in the process of forming large-area parts or parts with large sectional area change.

In order to achieve the above purpose, the specific technical scheme of the 3D printing method of the present invention is as follows:

a 3D printing method comprising the steps of:

step S1, importing the file of the target part into the laser selective melting process slicing software;

step S2, defining the A-A type section of the target part as a solid section and defining the B-B type section of the target part as a hollow section;

dividing the solid section into regions, defining a section boundary line as a solid contour, horizontally extending inwards along the solid contour for a preset distance to define a solid contour region, and defining the rest region of the solid contour region as a solid core region;

dividing a hollow section into areas, defining inner and outer boundary lines of the hollow section as an inner contour and an outer contour respectively, extending a preset distance inwards and horizontally along the outer contour to define an outer contour area, extending a preset distance outwards and horizontally along the inner contour to define an inner contour area, and defining the remaining area of the hollow section as a hollow core area;

step S3, defining laser beam scanning lines to be distributed in a serpentine line and scanned line by line in the solid contour area, the inner contour area and the outer contour area; defining the laser scanning lines to be arranged in a square shape in the solid core area and the hollow core area;

step S4, defining the distance between the serpentine lines as D, the length of the square in the X direction as L, the length of the square in the Y direction as H, the distance between the square scanning lines in the X direction as w, the distance between the square scanning lines in the Y direction as H, and the diameter of the laser beam as phi; wherein D is less than phi, L is more than phi, H is more than phi, w is less than phi, H is less than phi, H is more than H, and L is more than w;

step S5, if the current scanning object is a solid cross-section, the laser beam scanning the current layer includes the following steps:

step S51, scanning the entity outline area line by line from left to right and from bottom to top with fixed laser beam diameter, preset power and speed;

step S52, increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning the solid core area to form two disjoint square shapes;

step S53, restoring the original diameter of the laser beam, scanning for a preset number of times along the outline of the entity, and spreading powder by the printer after the scanning is finished;

step S54, scanning the next layer, and executing the step S51 to the step S53 in a circulating way;

if the current scanning object is a hollow section, when the laser beam scans the current layer, the method comprises the following steps:

step S51', scanning the inner contour region and the outer contour region simultaneously one time line by line from left to right, from bottom to top, with a fixed laser beam diameter, predetermined power and speed;

step S52', increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning the hollow core region to form two disjoint square shapes;

step S53', restoring the original diameter of the laser beam, simultaneously scanning for a preset number of times along the inner contour and the outer contour, and after the scanning is finished, the printer spreads the powder;

step S54 ', scan the next layer, and loop through steps S51 ' to S53 '.

The length of the scanning line is reduced by setting partitions, the shape of the scanning line and the scanning rotation mode; through subarea and subsection scanning, heat concentration is reduced, and then the stress concentration coefficient is reduced, and deformation and cracking are prevented.

Further, in step S5, the serpentine scan lines of adjacent layers are at an angle α, 180 ° > α > 1 °.

Further, in step S5, the rectangular scan lines of adjacent layers are rotated by an angle β in the clockwise direction, where β > 91 °, and the rectangular scan lines are moved by a distance δ in the X direction and a distance Ω in the Y direction, where δ > 10 × Φ and Ω > 10 × Φ. By means of scanning rotation, overlapping of scanning lines on the upper side and the lower side is prevented, and metallurgical defects are avoided.

Further, in step S5, in the X direction, the distance between the square shapes is greater than 10(L + w); in the Y direction, the distance between the square shapes is more than 10(H + H).

Further, in step S5, the ratio of the laser beam power to the scanning speed is maintained or increased before the laser beam diameter is changed.

Further, in step S5, after the original diameter of the laser beam is restored, the power of the laser beam is in a range of 35 to 300W, and the power of the scanning speed of the laser beam is in a range of 50 to 900 mm/S.

Further, in step S5, the predetermined amplification factor is in the range of 1.05-2.

Further, in step S5, the predetermined number of scans is in the range of 0 to 4.

The 3D printing method provided by the invention has the following advantages:

by arranging the subareas, different scanning line shapes are arranged in different subareas, and the scanning lines between adjacent layers are provided with the rotation angle, so that the length of the scanning lines can be reduced, the scanning lines are shorter, the reaction speed is accelerated, the heat concentration is low, and the stress concentration is favorably reduced; through subarea and subsection scanning, heat concentration is reduced, so that the stress concentration coefficient is reduced, and deformation and cracking are prevented; the scanning rotation mode can prevent the overlapping of the upper and lower scanning lines, and avoid the occurrence of metallurgical defects. By adopting the scanning line in the form or the shape, the problems of long scanning time and low forming efficiency are solved.

Drawings

FIG. 1 is a schematic view of a hollow box part provided by the present invention;

FIG. 2 is a cross-sectional view of parts A-A and B-B provided by the present invention;

FIG. 3 is a cross-sectional view of a laser scanning pattern A-A provided by the present invention;

FIG. 4 is a partial enlarged view taken at A in FIG. 3;

FIG. 5 is a B-B cross-sectional view of a laser scanning modality provided by the present invention;

FIG. 6 is a partial enlarged view taken at B in FIG. 5;

FIG. 7 is a schematic view of the scanning of the non-contoured region provided by the present invention.

In the figure: 11. a solid outline; 12. a solid core region; 13. a solid outline region; 211. an outer contour; 212. an inner contour; 22. a hollow core region; 231. an outer contour region; 232. an inner contour region.

Detailed Description

In order to make the objects, technical solutions and advantages of the present invention more apparent, the present invention is described in further detail below with reference to the accompanying drawings and embodiments. It should be understood that the specific embodiments described herein are merely illustrative of the invention and are not intended to limit the invention.

The invention provides a 3D printing method, which aims at the problems of large stress and low forming efficiency of large-area parts or products with large sectional area change formed by selective laser melting.

Referring to fig. 1, defining a pre-printed part, typically having either concave or convex portions, the present invention is illustrated by way of example of a hollow box that can represent the underlying structure of the part.

According to the selective laser melting forming principle, the parts are formed in a layer-by-layer stacking mode. And (3) importing a file taking a hollow box body as a target part into laser selective melting process slicing software, wherein the layering thickness of each part is defined as d.

Referring to fig. 2, the sectional area of the box body in the height direction has a sudden change, and the sectional shapes at different positions have a larger difference. And slicing the box part by using slicing software. A profile slice is formed with a layer thickness d. The cross-sectional shape of the sheet is different depending on the height.

A-A type section is defined as a solid section, and a B-B type section is defined as a hollow section. Because the areas of the solid section and the hollow section are different, the stress of the product is effectively reduced, and the forming effect is improved. And defining different scanning strategies in subsequent scanning.

Referring to fig. 3 and 4, the cross-sectional area is divided according to the solid cross-sectional area. The solid cross-sectional boundary line is defined as a solid contour 11. A region having a distance T from the solid outline 11 in the X direction and a distance T from the solid outline in the Y direction is defined as a solid outline region 13. The region other than the solid outline region 13 is defined as a solid core region 12. The values of the dimension T and the dimension T may be the same or different, and may also be defined as a distance along a normal vector of the solid contour 11. Meanwhile, the numerical values of T and T are less than half of the side length of the solid section in the horizontal and vertical directions.

For the solid profile region 13, the laser scan lines are laid out in a serpentine pattern, in a line-by-line scan. For the core area, the laser scanning lines are in the form of a square, a square or multiple enclosure.

The interval of the snake-shaped scanning lines is defined as D, and the length of the square-shaped scanning lines in the X direction is defined as L. The length in the Y direction is H, the distance in the X direction of the scanning lines is w, and the distance in the Y direction is H. The laser beam diameter is defined as phi. Wherein D is less than phi, L is more than phi, H is more than phi, w is less than phi, H is less than phi, H is more than H, and L is more than w.

The laser beam is scanned in the current layer while keeping the diameter phi of the laser beam unchanged. The outer contour region is scanned line by line from left to right and from bottom to top along a snake-shaped scanning line at a specific laser power P and a laser scanning speed V, and the scanning is only performed once. Wherein the scanning power P of the laser beam is 50-300W; the scanning speed V of the laser beam is 50-1000 mm/s.

And then amplifying the diameter phi of the laser beam, wherein the preferable range of the diameter amplification factor K is 1.05-2. The laser beam begins to scan the core region along the chevron scan line. During scanning, the laser beam completes a complete scan of a single square scan line in a random order. Then the random scanning of the next square scan line is started. Two square scanning lines which are continuously scanned are ensured, and line segments in the X direction are not directly connected. At a distance from each other greater than 10(L + w); the Y-direction line segments are also not directly connected with each other, and the distance between the Y-direction line segments is more than 10(H + H). Only once.

When the diameter of the laser beam becomes larger, the laser power is increased, and the laser scanning speed is maintained or appropriately reduced. Or the laser power is unchanged and the laser scanning speed is reduced. The laser power P is 60-300W; the laser scanning speed V is 40-1000 mm/s. In general, the ratio of the laser power P to the laser scanning speed V is ensured to be unchanged or properly increased compared with that before the diameter of the laser beam is changed.

Finally the diameter of the laser beam is adjusted back to the original size phi. A scan is started along the solid contour 11. After the diameter of the laser beam is adjusted, the laser power is reduced, and the laser scanning speed is kept unchanged or properly increased. The laser power P is 35-300W, and the laser scanning speed V is 50-900 mm/s.

The number of profile scans is N, which can be defined as 0, 1, 2, 3, 4.

After the current layer is scanned, the 3D printer finishes powder laying, and the laser beam starts to scan the next layer.

When scanning the next layer, the laser beam first begins to scan the solid contour region 13 along a serpentine scan line, as previously described. The laser power and scanning speed are the same as the previous layer. But at this time, the direction of the snake-shaped scanning line changes, and the snake-shaped scanning line forms a certain included angle alpha with the scanning line of the previous layer, the included angle alpha is more than 180 degrees and is more than 1 degree, and the scanning of the solid outline region 13 is carried out on each subsequent layer according to the mode.

After the solid outline region 13 is scanned, the laser beam starts to scan the solid core region 12 along the scan line in the same manner as described above. But the square scan line direction also changes. In the clockwise direction, the scan line segment of the (N + 1) th layer is rotated by an angle beta compared with the scan line segment of the Nth layer, wherein the angle beta is more than 180 degrees and more than 91 degrees. Meanwhile, the square scanning line moves a certain distance delta along the X direction and moves a certain distance omega along the Y direction. And δ > 10 Φ; omega > 10 phi. Ensure that the scanning lines of the two connected layers are not coincident. Each subsequent layer is scanned in this manner for the core region.

And circularly reciprocating to sequentially complete the scanning of the solid section.

Referring to fig. 5 and 6, for the hollow cross-section, the cross-sectional area thereof is divided according to the cross-sectional area thereof. The cross-sectional inner and outer boundary lines are defined as an outer contour 211 and an inner contour 212, respectively. A region separated from the outer contour 211 by a distance T1 in the X direction and separated from the outer contour 211 by a distance T1 in the Y direction is defined as an outer contour region 231. An area spaced from inner contour 212 by a dimension T3 in the X-direction and by a dimension T3 in the Y-direction is defined as inner contour area 232.

The area of the hollow cross section other than the inner and outer contour areas 231 is defined as a hollow core area 22. The core region has an X-direction dimension T2 and a Y-direction dimension T2.

The values of the dimensions T1 and T3, T1 and T3 may be the same or different, and may also be defined as the distance along the normal vector of the contour. Meanwhile, the numerical values of T1, T3, T1 and T3 are all less than half of the side length of the hollow section in the horizontal and vertical directions.

For the inner contour area and the outer contour area, the laser scanning lines are in a snake-shaped layout and adopt a line-by-line scanning mode. For the core area, the laser scanning lines are in the form of a square, a square or multiple enclosure. The scan lines are equally spaced apart as shown in fig. 4 (only the square is shown for ease of illustration).

Inner contour region 232 and outer contour region 231, the laser beam scan lines are laid out in a serpentine line, scanning line by line. The difference is that the inner contour region 232 and the outer contour region 231 do not need to be sequenced. The serpentine scan line directions of the inner contour region 232 and the outer contour region 231 may be the same or different. If different, in the same section. A certain included angle exists between the two, and the included angle has a value of 0-180 degrees.

For the hollow core region 22, the laser scan lines are laid out in a square, or a multiple enclosure.

The outer 211 and inner 212 profiles for the hollow cross-section are in accordance with the manner described above for scanning the solid profile.

And after the scanning of the current layer is finished, the scanning is carried out according to the mode of scanning the solid section until the scanning of the hollow section area is finished.

Furthermore, in order to improve the appearance quality of the product, referring to fig. 7, when the dimension in the height direction of the box body or in the direction of the normal vector of the contour line is smaller than M. In this case, the height-direction cross section has only the core region and the contour line. The core area of the box body part is scanned in a snake-shaped mode, the specific scanning mode is consistent with the scanning mode, and the box body part is printed in a circulating and reciprocating mode.

In summary, a 3D printing method can be obtained, which includes the following steps:

step S1, importing the file of the target part into special software of the selective laser melting process;

dividing the solid section into regions, defining a section boundary line as a solid outline 11, extending inwards along the solid outline 11 for a preset distance to define a solid outline region 13, and defining the rest region of the solid outline region (13) as a solid core region 12;

dividing the hollow section into areas, defining inner and outer boundary lines of the hollow section as an inner contour 212 and an outer contour 211 respectively, horizontally extending a predetermined distance inwards along the outer contour 211 as an outer contour area 231, horizontally extending a predetermined distance outwards along the inner contour 212 as an inner contour area 232, and defining the remaining area of the hollow section as a hollow core area 22;

step S3, defining laser beam scanning lines to be laid out in a serpentine line and scanned line by line in the solid contour region 13, the inner contour region 232) and the outer contour region 231; in the solid core area 12 and the hollow core area 22, laser scanning lines are defined to be arranged in a square shape;

step S51, scanning the solid contour region 13 line by line from left to right, from bottom to top, once with a fixed laser beam diameter, predetermined power and speed;

step S52, increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning two disjoint square shapes on the solid core area 12;

step S53, restoring the original diameter of the laser beam, scanning for a preset number of times along the entity outline 11, and spreading powder by the printer after the scanning is finished;

step S51', scanning the inner contour region 232 and the outer contour region 231 line by line simultaneously once from left to right, from bottom to top, with a fixed laser beam diameter, predetermined power and speed;

step S52', increasing the diameter of the laser beam by a predetermined magnification factor, randomly scanning the hollow core region 22 for two disjoint square shapes;

step S53', restoring the original diameter of the laser beam, performing scanning along the inner contour 212 and the outer contour 211 for a predetermined number of times, and after the scanning is finished, performing powder spreading operation by the printer;

step S54 ', scan the next layer, and loop through steps S51 ' to S53 '.

According to the 3D printing method provided by the invention, the subareas are arranged, different scanning line shapes are arranged in different subareas, and the scanning lines between adjacent layers are provided with the rotation angle, so that the length of the scanning lines can be reduced, the scanning lines are shorter, the reaction speed is accelerated, the heat concentration is low, and the stress concentration can be reduced; through subarea and subsection scanning, heat concentration is reduced, so that the stress concentration coefficient is reduced, and deformation and cracking are prevented; the scanning rotation mode can prevent the overlapping of the upper and lower scanning lines, and avoid the occurrence of metallurgical defects. By adopting the scanning line in the form or the shape, the problems of long scanning time and low forming efficiency are solved.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents and improvements made within the spirit and principle of the present invention are intended to be included within the scope of the present invention.

Claims

1. A3D printing method is characterized by comprising the following steps:

dividing the solid section into regions, defining a section boundary line as a solid outline (11), horizontally extending inwards along the solid outline (11) for a preset distance to define a solid outline region (13), and defining the rest region of the solid outline region (13) as a solid core region (12);

dividing the hollow section into areas, defining inner and outer boundary lines of the hollow section as an inner contour (212) and an outer contour (211), respectively, horizontally extending inwards along the outer contour (211) for a predetermined distance to define an outer contour area (231), horizontally extending outwards along the inner contour (212) for a predetermined distance to define an inner contour area (232), and defining the remaining area of the hollow section as a hollow core area (22);

step S3, defining laser beam scanning lines to be distributed in a serpentine line and scanned line by line in a solid contour region (13), an inner contour region (232) and an outer contour region (231); defining laser scanning lines to be arranged in a square shape in a solid core area (12) and a hollow core area (22);

step S4, defining the interval of the serpentine line as D, the length of the square in the X direction as L, the length of the square in the Y direction as H, the interval of the square scanning line in the X direction as w, the interval of the square scanning line in the Y direction as H, and the diameter of the laser beam as phi; wherein D is less than phi, L is more than phi, H is more than phi, w is less than phi, H is less than phi, H is more than H, and L is more than w;

step S51, scanning the solid outline region (13) line by line from left to right and from bottom to top with fixed laser beam diameter, preset power and speed;

step S52, increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning two disjoint square shapes on the solid core area (12);

step S53, restoring the original diameter of the laser beam, scanning for a preset number of times along the entity outline (11), and spreading powder by the printer after the scanning is finished;

step S51', scanning the inner contour region (232) and the outer contour region (231) line by line simultaneously from left to right, from bottom to top, with a fixed laser beam diameter, predetermined power and speed;

step S52', increasing the diameter of the laser beam by a preset amplification factor, and randomly scanning the hollow core region (22) for two non-intersecting square shapes;

step S53', restoring the original diameter of the laser beam, simultaneously scanning for a preset number of times along the inner contour (212) and the outer contour (211), and after the scanning is finished, the printer performs powder paving action;

step S54 ', scan the next layer, and loop through steps S51 ' to S53 '.

2. The 3D printing method according to claim 1, wherein in step S5, the serpentine scan lines of adjacent layers are at an included angle α, 180 ° > α > 90 °.

3. The 3D printing method according to claim 2, wherein in step S5, the rectangular scan lines of adjacent layers are rotated by an angle β in a clockwise direction, 180 ° > β > 91 °, and the rectangular scan lines are simultaneously moved by a distance δ in an X direction and by a distance Ω in a Y direction, wherein δ > 10 Φ and Ω > 10 Φ.

4. The 3D printing method according to claim 3, wherein in step S5, the distance between the square shapes in the X direction is greater than 10(L + w); in the Y direction, the distance between the square shapes is more than 10(H + H).

5. The 3D printing method according to claim 4, wherein in step S5, the ratio of laser beam power to scanning speed is maintained or increased before the laser beam diameter changes.

6. The 3D printing method according to claim 5, wherein in step S5, after the original diameter of the laser beam is recovered, the power of the laser beam is in a range of 35W to 300W, and the power of the scanning speed of the laser beam is in a range of 50 mm/S to 900 mm/S.

7. The 3D printing method according to claim 5, wherein in step S5, the predetermined magnification factor is in a range of 1.05-2.

8. The 3D printing method according to claim 7, wherein in the step S5, the predetermined number of scanning times is in a range of 0-4.