CN110605392A - A metal solid printing method with alternating outer wall surfacing and inner filling - Google Patents

Abstract

The invention discloses a metal entity printing method for alternately performing outer wall surfacing and inner filling, and belongs to the technical field of additive manufacturing. The invention avoids the problem of sagging and collapse when vertically printing certain inclined positions by changing the attitude of the area where the workpiece is prone to sagging, and ensures the stability of the forming; Using traditional three-axis additive instead of changing attitude processing can better avoid interference and reduce the complexity of path planning. In order to avoid the interference between the welding torch and the printed outer wall hanging area when the workpiece is printing other areas to be printed, a strategy of alternately printing the outer wall hanging area and other areas every 8mm is adopted to ensure the sustainability of the surfacing process. By using the printing method of the present invention, the problem of hanging currents at certain positions of the workpiece in the traditional three-axis additive material is solved.

Description

A metal solid printing method with alternating outer wall surfacing and inner filling

technical field

The invention belongs to the technical field of additive manufacturing, and in particular relates to a metal solid printing method for alternately performing outer wall surfacing and inner filling.

Background technique

Additive manufacturing technology, commonly known as 3D printing, is a digital manufacturing technology that finally obtains the desired workpiece by adding and stacking materials layer by layer. In recent years, with the rapid development of metal additive manufacturing technology, many metal parts that are difficult to process or expensive by traditional methods can be quickly realized by metal additive manufacturing process. At present, metal additive manufacturing technology has been applied in many fields. Among them, arc additive manufacturing has many advantages, such as high deposition rate, short manufacturing cycle, high wire utilization, and low cost. In addition, the formed parts have high density, uniform chemical composition and excellent mechanical properties.

For example, a Chinese patent document with publication number CN207642290U discloses a single-metal arc type 3D printing device, including an X-axis linkage mechanism, a Y-axis linkage mechanism, a Z-axis linkage mechanism, and a mechanism for controlling the X-axis linkage, Y-axis linkage and A control system in which the Z-axis linkage mechanism performs three-axis linkage, the X-axis linkage mechanism is provided with a welding torch for printing workpieces, and the X-axis linkage mechanism is installed on the Z-axis linkage mechanism to drive the welding torch to realize the X direction and the Z axis. The Y-axis linkage mechanism is provided with a workpiece substrate that can move in the Y direction with it, and the workpiece substrate is located below the welding torch.

However, in the process of arc additive manufacturing, the wire becomes a high temperature melting state. If the traditional three-degree-of-freedom printing mode is used, serious slump collapse will occur when some inclined structures are formed by surfacing. Therefore, a multi-degree-of-freedom robotic arm is generally used for metal surfacing forming.

However, when printing metal solids, the entire surfacing process is printed with multiple degrees of freedom and variable attitude, sometimes there will be more interference, and the path planning will be more complicated. The combination of degree-changing pose printing in metal solid printing will greatly improve the processing efficiency and ensure the stability of forming. However, a method combining the two printing forms has not yet been used for metal forming.

SUMMARY OF THE INVENTION

The invention provides a metal solid printing method in which outer wall surfacing and inner filling are alternately performed, and solves the problem of drape at certain positions of the workpiece in the traditional three-axis additive material.

The technical scheme of the present invention is as follows:

A metal solid printing method for alternately performing outer wall surfacing and inner filling, characterized in that it includes the following steps:

(1) Obtain the STL model of the workpiece to be processed, and set the printing parameters, the printing parameters include the layer height of the additive process, the wire feeding speed, the printing speed and the bead spacing;

(2) Horizontally slice the entire model according to the set layer height of the additive process to obtain the set A of slice outlines, and fill the interior of the slice outlines to obtain the set S of internal path segments;

(3) Analyze the STL model of the workpiece to obtain the flow-hanging area on the outer wall of the model and the non-flow-hanging area on the outer wall, and obtain the model height H;

(4) For the slice contour line segments in the set A that fall in the hanging area, delete all other contour line segments except the lowest contour line segment, and select the lowest contour line segment as the baseline, and carry out the process with the additive layer height on the outer wall surface. Continuous equidistant offset to obtain offset contour segment set B;

(5) Sort the line segments in the set A, B, and S to plan the additive path that constitutes the model;

(6) Construction planes z1=h and z2=0, where the value of h is less than the dry elongation of the welding wire;

(7) Select the line segment between the planes z1 and z2 in the set B and the set A∪S in turn to form an additive printing sequence;

(8) Judging the relationship between z1 and H, if z1<H, update the values of z1 and z2, z1=z1+h, z2=z2+h and return to step (7), otherwise, execute step (9);

(9) According to the above-obtained additive printing sequence, a model additive path is generated, wherein the line segment in the set B is printed with a variable attitude, and the line segment in the set A∪S is printed with a traditional fixed attitude; and the robot motion code is generated;

(10) On the additive manufacturing platform, alternately perform the printing process of surfacing welding of the outer wall of the variable posture and filling of the interior of the fixed posture.

The invention uses the variable attitude to print the outer wall hanging area of the workpiece to ensure the stability of forming, and at the same time, the non-flow hanging area of the outer wall and the interior of the solid still use traditional three-axis additive instead of multi-degree-of-freedom variable attitude processing, which can be better to avoid interference.

In step (3), the division criteria of the outer wall hanging area and the outer wall non-hanging area are: dividing all positions where the normal vector on the outer wall of the workpiece is located under the space XY plane into the outer wall hanging area, and removing the outer wall of the workpiece. The set of all positions outside the hanging area is divided into the non-hanging area of the outer wall.

In step (6), since the dry elongation of the welding wire is generally about 12 mm, in order to print the contour line segment of the non-current hanging area of the outer wall and the internal filling in a fixed attitude, it can be ensured that the welding torch does not interfere with the printed outer wall hanging area. , the value of h is preferably 8 to 10 mm. Further, the value of h is 8mm.

In step (7), in the vertical height interval h of the planes z1 to z2, first print the outline segment of the outer wall of the hanging area in the height interval, and then print other areas of the outer wall layer by layer and complete the internal filling, forming an increase in the height interval. material printing sequence.

In step (9), the printing direction D of the variable posture is obtained by the cross-multiplication N×T of the normal direction N of the workpiece surface at this point and the tangential direction T of the baseline or offset line at this point; the printing direction of the traditional fixed posture is: Vertical Z direction.

Compared with the prior art, the present invention has the following beneficial effects:

The metal solid printing method of the present invention, which alternately performs outer wall surfacing welding and inner filling, avoids the problem of sagging and collapse when vertically printing certain inclined positions, and ensures the formation stability. At the same time, alternately print the outer wall hanging area and other positions to avoid interference and ensure the continuity of surfacing.

Description of drawings

FIG. 1 is a schematic flow chart of a metal solid printing method for alternately performing outer wall surfacing and inner filling according to the present invention;

2 is a schematic diagram of a workpiece model selected in an embodiment of the present invention;

3 is a schematic diagram of horizontal slicing of the workpiece model according to the height of the additive layer according to the embodiment of the present invention, obtaining a slicing contour line segment and completing filling to obtain an internal path line segment;

4 is a schematic diagram of an offset contour line segment obtained by continuously equidistantly offsetting an external wall hanging flow area according to an embodiment of the present invention;

5 is a schematic diagram of a plane z1=8mm and a plane z2=0mm constructed in an embodiment of the present invention;

FIG. 6 is a schematic diagram of no interference between the welding torch and the flow-hanging area of the outer wall when the alternating height is set to 8 mm according to the embodiment of the present invention.

Detailed ways

The present invention will be further described in detail below with reference to the accompanying drawings and embodiments. It should be pointed out that the following embodiments are intended to facilitate the understanding of the present invention, but do not have any limiting effect on it.

As shown in Figure 1, a metal solid printing method for alternately performing outer wall surfacing and inner filling, including the following steps:

Step 1, obtain the STL model of the workpiece to be processed, as shown in Figure 2, set the layer height of the additive process to 2.0mm, the build-up welding speed to be 0.011m/s, the wire feeding speed to be 5.0m/min, and the welding bead to be 5.0m/min. The pitch is 4.0mm.

The printing material selected in this embodiment is ER5356 stainless steel welding wire with a diameter of 1.2 mm. The protective gas is a mixture of 2% oxygen and 98% argon. The protective air flow was set to 20L/min.

In step 2, the entire model is sliced horizontally according to the additive layer height, as shown in Figure 3, to obtain the slice outline segment set A and complete the filling to obtain the internal path line segment set S.

Step 3, analyze the STL model, obtain the flow-hanging area and the non-flow-hanging area on the outer wall of the model, and obtain the model height H=50mm.

The definition of the flow area on the outer wall is the set of all positions where the normal vector on the outer wall of the workpiece is located under the space XY plane, that is, the area c in Figure 2. The definition of the non-hanging area of the outer wall is the set of all positions on the outer wall of the workpiece except the hanging area, namely the area a, the area b, the area d and the area f in FIG. 4 .

Step 4, as shown in Figure 4, for the slice contour segments in each hanging area in set A, delete all other contour segments except the lowest contour segment, and select the lowest contour segment as the baseline, on the outer wall surface. Offset contour line segment set B is obtained by continuous equidistant offset with the additive layer height.

Step 5: Sort and plan the line segments in the set A, B, and S to form a model additive path.

Step 6, construct planes z1=8mm and z2=0mm, as shown in FIG. 5 .

Step 7: Select the line segments between the planes z1 and z2 in the set B and A∪S in turn to form an additive printing sequence.

Within the vertical height variation range of 8mm, first print the outline of the outer wall of the hanging area within this height range, then print other areas of the outer wall layer by layer and complete the internal filling to form an additive printing sequence within this height range. The vertical height variation range is set to 8mm, because the dry elongation of the welding torch is generally set to 12mm, as shown in Figure 6, so when printing the contour line segment of the non-hanging area of the outer wall and the internal filling in a fixed position, the welding torch can be ensured. Interferes with the part of the outer wall hanging area that has been printed.

Step 8, determine the relationship between z1 and H, if z1<H, then z1=z1+8, z2=z2+8 and return to step 7, otherwise, go to step 9.

Step 9, according to the above planning, generate a model additive path, wherein the line segments in the set B are printed with a variable attitude, and the line segments in the set A∪S are printed with a traditional fixed attitude; and the robot motion code is generated. The printing direction D of the variable attitude is obtained by the cross-multiplication N×T of the normal direction N of the workpiece surface at this point and the tangential direction T of the baseline or offset line at this point, as shown in FIG. 4 . The traditional fixed attitude is the vertical Z direction.

Step 10: Alternately perform a printing process of surfacing of the outer wall with a variable attitude and filling of the interior with a fixed attitude on the additive manufacturing platform.

The printing method of the present invention solves the problem that the traditional three-axis additive material will generate sagging at certain positions of the workpiece. Using the variable attitude to print the flow area on the outer wall of the workpiece ensures the stability of the forming. At the same time, traditional three-axis additive materials are still used in the non-hanging area of the outer wall and the interior of the solid body instead of multi-degree-of-freedom variable attitude processing, which can better avoid interference. In order to avoid the interference between the welding torch and the printed outer wall hanging area when printing other areas to be printed, a strategy of alternately printing the outer wall hanging area and other areas every 8mm is adopted to ensure the sustainability of the surfacing process.

The above-mentioned embodiments describe the technical solutions and beneficial effects of the present invention in detail. It should be understood that the above-mentioned embodiments are only specific embodiments of the present invention, and are not intended to limit the present invention. Any modifications, additions and equivalent replacements made shall be included within the protection scope of the present invention.

Claims (6)

1. A metal solid printing method for alternately performing outer wall surfacing and inner filling, characterized in that it comprises the following steps: (1) Obtain the STL model of the workpiece to be processed, and set the printing parameters, the printing parameters include the layer height of the additive process, the wire feeding speed, the printing speed and the bead spacing; (2) Horizontally slice the entire model according to the set layer height of the additive process to obtain the set A of slice outlines, and fill the interior of the slice outlines to obtain the set S of internal path segments; (3) Analyze the STL model of the workpiece to obtain the flow-hanging area on the outer wall of the model and the non-flow-hanging area on the outer wall, and obtain the model height H; (4) For the slice contour line segments in the set A that fall in the hanging area, delete all other contour line segments except the lowest contour line segment, and select the lowest contour line segment as the baseline, and carry out the process with the additive layer height on the outer wall surface. Continuous equidistant offset to obtain offset contour segment set B; (5) Sort the line segments in the set A, B, and S to plan the additive path that constitutes the model; (6) Construction planes z1=h and z2=0, where the value of h is less than the dry elongation of the welding wire; (7) Select the line segment between the planes z1 and z2 in the set B and the set A∪S in turn to form an additive printing sequence; (8) Judging the relationship between z1 and H, if z1<H, update the values of z1 and z2, z1=z1+h, z2=z2+h and return to step (7), otherwise, execute step (9); (9) According to the above-obtained additive printing sequence, a model additive path is generated, wherein the line segment in the set B is printed with a variable attitude, and the line segment in the set A∪S is printed with a traditional fixed attitude; and the robot motion code is generated; (10) On the additive manufacturing platform, alternately perform the printing process of surfacing welding of the outer wall of the variable posture and filling of the interior of the fixed posture. 2 . The metal solid printing method for alternately performing outer wall surfacing and inner filling according to claim 1 , wherein, in step (3), the division criteria of the outer wall hanging area and the outer wall non-hanging area are: 2 . The set of all positions on the outer wall of the workpiece where the normal vector is located under the space XY plane is divided into the outer wall hanging area, and the set of all positions on the outer wall of the workpiece except the hanging area is divided into the outer wall non-hanging area. 3 . The metal solid printing method for alternately performing outer wall surfacing and inner filling according to claim 1 , wherein, in step (6), the value of h is 8-10 mm. 4 . 4 . The metal solid printing method for alternately performing outer wall surfacing and inner filling according to claim 1 , wherein, in step (6), the value of h is 8 mm. 5 . 5 . The metal solid printing method for alternately performing outer wall surfacing and inner filling according to claim 1 , wherein in step (7), in the vertical height interval h of the plane z1 to z2 , the height interval is first printed. 6 . The contour line segment of the outer wall of the inner hanging area is then printed layer by layer in other areas of the outer wall and the internal filling is completed to form an additive printing sequence within this height range. 6 . The metal solid printing method for alternately performing outer wall surfacing and inner filling according to claim 1 , wherein in step (9), the printing direction D of the variable posture is determined by the normal direction N and the normal direction of the workpiece surface at the point. 7 . The cross-multiplication N×T of the tangential T of the baseline or offset line at this point is obtained; the printing direction of the traditional fixed posture is the vertical Z direction.