A path planning method for additive manufacturing of cross-shaped workpieces

Abstract

The present invention discloses an additive manufacturing path planning method for cross-shaped workpieces, which belongs to the field of additive manufacturing technology and includes the steps of obtaining a slice polygon, determining a polygon centerline, identifying bifurcation area features, generating a cross path, etc. The method is mainly used for additive manufacturing path planning of cross-shaped workpieces such as cross-shaped cross-shaped workpieces and T-shaped cross-shaped workpieces. Additive manufacturing is performed on the path planned by the method, which avoids frequent start and stop of the feeding mechanism at the intersection, and does not cause excessive accumulation of additive manufacturing materials in the intersection area, thereby improving the efficiency of additive manufacturing, reducing the failure rate and production cost of the feeding mechanism, and increasing the life of the feeding mechanism.

Description

Technical Field

[0001] The invention relates to an additive manufacturing path planning method for a cross-type workpiece, and belongs to the technical field of additive manufacturing. Background Art

[0002] Currently, two methods are usually used for the additive manufacturing path planning method of cross-shaped workpieces (such as cross-shaped workpieces and T-shaped workpieces): one method is to start and stop the feeding mechanism frequently at the intersection to avoid excessive accumulation of materials at the intersection path, but frequent starts and stops at the intersection will affect the efficiency of additive manufacturing and affect the life and failure rate of the feeding mechanism; the other method is to repeatedly accumulate additive manufacturing materials directly at the intersection, which can avoid frequent starts and stops, but will cause a certain degree of excessive accumulation of additive manufacturing materials at the intersection. Summary of the invention

[0003] The technical problem to be solved by the present invention is to overcome the defects of the prior art and provide an additive manufacturing path planning method for cross-type workpieces, so as to avoid frequent starting and stopping of the feeding mechanism at the intersection and avoid excessive accumulation of additive manufacturing materials at the intersection.

[0004] In order to solve the above technical problems, the technical solution adopted by the present invention is as follows:

[0005] A method for additive manufacturing path planning for a cross-shaped workpiece comprises the following steps:

[0006] Step 1, obtain the slicing polygon Q of the cross-shaped workpiece, and determine the center line S of the polygon;

[0007] Step 2: Determine the intersection area and non-intersection area of ​​the polygon based on the center line;

[0008] 21) Determine the shortest distance d = min(dist(a,q)) from point a on the center line to polygon Q, and a∈S, q∈Q. The point q on polygon Q at the shortest distance is the support point of a.

[0009] 22) For any point on the centerline, if the number of centerline segments connected at the point n>2, then let the point be the bifurcation point b, if n=2, then the point is the ordinary center point on the centerline, if n=1, then the point is the endpoint;

[0010] 23) The area formed by connecting the supporting points corresponding to the bifurcation point b of the center line in sequence is the intersection area; the other areas of the polygon except the intersection area are the non-intersection area; the intersection point of the intersection area polygon and the center line is the division point of the center line;

[0011] Step 3: determine the printing order of the non-intersection area, and print the non-intersection area in the determined order; and when passing through the intersection area during the printing of the non-intersection area, print the intersection area according to the generated center line of the intersection area as the filling path;

[0012] For the non-intersecting areas of adjacent upper and lower layers, the angle between the center line dividing point of the area in the same layer and the line connecting the bifurcation point b is the area angle; i+1 represents the upper layer, and i represents the lower layer;

[0013] 31) First, in the lower layer, select one of the regions with the largest angle as the starting region. The mth area with the smallest angle with the starting area is selected as the next printing area Where m is the region sequence number, m≥1;

[0014] 32) Then select the mth printing area The corresponding upper layer mth printing area For the next printing area;

[0015] 33) If there is an unprinted area in the lower layer, select the area in the lower layer that is the same as the mth printed area. The unprinted area with the largest area angle is the next (m+1) printing area. At the same time, m+1 is regarded as m, and then the process goes to step 32) until there is no unprinted area in the lower layer;

[0016] If there is no unprinted area in the lower layer, select the area in the upper layer area Prints the last print area.

[0017] Furthermore, when printing in a non-intersection area or an intersection area, if 2d≤w, d is the shortest distance from a point on the center line to a polygon, and w is the fill width, then the fill path of the printing area is a single-pass path, otherwise the fill path is a multi-pass path.

[0018] Furthermore, for a single path, filling is performed with the center line as the filling path and 2d as the actual filling width.

[0019] Furthermore, for multiple paths, a straight line segment perpendicular to the center line is generated along the center line direction, and the straight line segment is used as the filling path and filled with a filling width w.

[0020] Furthermore, in step 3, the steps of generating the center line of the intersection area are:

[0021] For the upper layer mth printing area The dividing point p of the center line i+1 Move along the center line into the non-intersecting area by a filling width w to form a new segmentation point The corresponding lower layer mth printing area The dividing point p of the center line i A new segmentation point is formed by shrinking 1 / 2 of the filling width w along the center line into the non-intersecting area. The two new split points are connected into a line segment As the center line connecting the upper and lower layers, then connect this line segment with the m+1th printing area of ​​the lower layer. The split point Connect and finally form the center line of the upper and lower intersection areas

[0022] Further, the filling width w ranges between a minimum filling width and a maximum filling width permitted by the filling process.

[0023] Furthermore, the number of straight line segments is N=L / w, L is the length of the center line of the printing area, and w is the filling width; the length of the straight line segment l=2d-w; if the starting and ending points of the filling path are on the same side of the center line, N is selected as an even number, otherwise N is an odd number.

[0024] Furthermore, in step 3, when transitioning to the next printing area after printing one printing area, the connection path formed between the filling paths of the two printing areas is the transition path, and the transition path is constructed to make the filling paths in different areas continuous.

[0025] Furthermore, the specific method for determining the transition path is as follows:

[0026] For the mth and m+1th printing areas in the two adjacent printing orders of the two connections in the lower layer To find the transition path between the two paths, first establish two rays r1 and r2 at the end and starting points of the two paths respectively. Among them, s i is the bifurcation point of the lower crossover region, There are two printing areas in the lower layer. The corresponding fill path, Fill paths separately The starting point and end point of Fill paths separately The starting point and end point of are the segmentation points of the m+1th and mth regions of the lower layer, respectively, with proportional coefficients t1, t2∈[0,∞), and then the intersection point of the two rays is calculated u=r1∩r2, then the line segment and line segments For the transition path.

[0027] Further, for the upper layer mth printing area Go to the m+1th printing area on the lower layer The transition path is s i+0.5 =(s i +s i+1 )*0.5 is the interlayer bifurcation point in the intersection area between the lower layer and the upper layer, s i is the bifurcation point of the lower crossover region, s i+1 is the bifurcation point of the upper cross region, and the transition point of the interlayer region is calculated as the intersection point v = r3 ∩ r4 of the two rays r3 and r4. in, There are two printing areas, upper and lower. The corresponding fill path, To fill the path The end point, To fill the path The starting point, is the segmentation point of the m+1th region in the lower layer, is the segmentation point of the mth region in the upper layer, and the proportional coefficients t3, t4∈[0,∞), then the line segment and line segments It forms a transition path between the two areas.

[0028] The beneficial effects achieved by the present invention are:

[0029] The present invention discloses an additive manufacturing path planning method for intersecting workpieces, which is mainly used for additive manufacturing path planning for intersecting workpieces such as cross-shaped intersecting workpieces and T-shaped intersecting workpieces. Additive manufacturing is performed on the path planned by the method, which avoids frequent starting and stopping of a feeding mechanism at the intersection, and does not cause excessive accumulation of additive manufacturing materials in the intersection area, thereby improving the efficiency of additive manufacturing, reducing the failure rate and production cost of the feeding mechanism, and increasing the life of the feeding mechanism. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] Figure 1 is a flow chart of the additive manufacturing path planning method of Example 1;

[0031] Figure 2 It is a schematic diagram of the characteristic points in the intersection area;

[0032] Figure 3 It is a schematic diagram of the inter-layer connection of a T-shaped cross single-lane path;

[0033] Figure 4 It is a schematic diagram of the inter-layer connection of a cross-shaped single-channel path;

[0034] Figure 5 It is a schematic diagram of a T-shaped intersection with multiple paths;

[0035] Figure 6 It is a schematic diagram of a cross-shaped multi-path. DETAILED DESCRIPTION

[0036] The present invention will be further described below in conjunction with the accompanying drawings. The following embodiments are only used to more clearly illustrate the technical solution of the present invention, and cannot be used to limit the protection scope of the present invention.

[0037] Example 1

[0038] This embodiment provides a method for additive manufacturing path planning for a cross-shaped workpiece, such as Figure 1 As shown, the specific steps include:

[0039] 1. Obtain the slicing polygon Q of the workpiece. Taking a cross-shaped workpiece as an example, the slicing polygon Q is a cross, such as Figure 2 As shown, and determine the center line S of the polygon.

[0040] 2. Determine the intersection area of ​​the polygon based on the center line.

[0041] 21) Determine the shortest distance d = min(dist(a,q)) from point a on the center line to polygon Q, and a∈S,q∈Q. Then point q on polygon Q at the shortest distance is the support point of a, Figure 2 For example, there are 4 supporting points, namely q1, q2, q3, and q4.

[0042] 22) For any point on the centerline, if the number of centerline segments connected at this point n>2, then the point is set as the bifurcation point b, that is, if n=3, it is a T-shaped cross bifurcation point, and if n=4, it is a cross-shaped cross bifurcation point. If n=2, then the point is a normal center point on the centerline, and if n=1, then the point is the endpoints s and e.

[0043] 23) The area formed by connecting the supporting points corresponding to the bifurcation point b of the center line in sequence is the intersection area, that is, Figure 2 The filled area in the polygon is the non-intersecting area. For example, the non-intersecting area is represented by m is the sequence number of the area in the lower layer i, m ≥ 1. The intersection point of the polygonal contour line and the center line of the intersection area is the dividing point p of the center line. Figure 2 For example, there are 4 split points, namely p1, p2, p3, and p4.

[0044] 3. Determine the printing order of the non-intersection area, and print the non-intersection area in the determined order; and when passing through the intersection area during the printing of the non-intersection area, print the intersection area according to the generated center line of the intersection area as the filling path;

[0045] For non-intersecting areas of adjacent upper and lower layers, if the projections of the lower and upper layers overlap (when the projections overlap, the polygonal contours of the lower and upper layers are completely consistent, or one of the regions completely surrounds the other), they are determined to be corresponding areas. i+1 represents the upper layer, and i represents the lower layer.

[0046] The angle between the dividing point and the bifurcation point b between the regions on the same layer is the region angle Where j, k are the region numbers.

[0047] The printing order of non-intersecting areas is:

[0048] 31) First, in the lower layer, select one of the regions with the largest angle as the starting region. The area with the smallest angle with the starting area is selected as the next printing area Where m is the area sequence number, m ≥ 1. After printing, mark the two areas as printed areas.

[0049] 32) Then select the mth printing area in the lower layer The corresponding upper layer mth printing area It is the next printing area and is marked as the printed area after printing.

[0050] 33) If there is an unprinted area in the lower layer, select the area in the lower layer that is the same as the mth printed area. The unprinted area with the largest angle is the next (m+1) printing area. After printing, it is marked as a printed area. At the same time, m+1 is regarded as m, and then the process goes to step 32) until there is no unprinted area in the lower layer.

[0051] If there is no unprinted area in the lower layer, select the area in the upper layer area The last print area.

[0052] The specific steps for generating the center line of the intersection area are:

[0053] For the upper layer mth printing area The dividing point p of the center line i+1 Move along the center line into the non-intersecting area by a filling width w to form a new segmentation point The corresponding lower layer mth printing area The dividing point p of the center line i A new segmentation point is formed by shrinking 1 / 2 of the filling width w along the center line into the non-intersecting area. The two new split points are connected into a line segment As the center line connecting the upper and lower layers, then connect this line segment with the m+1th printing area of ​​the lower layer. Path split point Connect and finally form the cross center line of the upper and lower layers where w min ≤w≤w max , and w min 、w max They are respectively the minimum and maximum filling widths allowed by the filling process.

[0054] The upper intersection center line is the center line of the upper intersection area and the line connecting the two dividing points.

[0055] The specific steps for determining the fill path when printing in the area are:

[0056] If 2d≤w, d is the shortest distance from a point on the center line to the polygon, and w is the filling width, then the filling path of the polygon area is a single-pass path, otherwise it is a multi-pass path.

[0057] For a single path, such as Figure 3 , Figure 4 As shown, the center line is used as the filling path and 2d is used as the actual filling width. Taking the lower layer area as an example, the mth and m+1th printing areas in the adjacent printing order are Fill path The corresponding end point and starting point is the endpoint with the shortest distance to the center line, then the corresponding starting point and end point The other end point of the center line, that is, the print area Fill Path Starting point end Print Area Fill Path Starting point end The same applies to the upper area.

[0058] For multiple paths, such as Figure 5 , Figure 6 As shown in the figure, a straight line segment l perpendicular to the center line is generated along the center line direction, and the straight line segment is used as the path for filling. Taking the lower layer area as an example, the mth and m+1th printing areas in the adjacent printing order are Fill path The corresponding end point and starting point is the closest endpoint of the straight line segment between the two regions, then the corresponding starting point and end point Any endpoint of the straight line segment at the other end of the center line. The same applies to the upper area.

[0059] Assume that the number of straight line segments is N = L / w, where Nmin ≤N≤N max , N min =L / w max , N max =L / w min , L is the length of the center line segment. Then the length of the straight line segment l = 2d-w. If the start and end points of the filling path are on the same side of the center line, select N as an even number, otherwise N is an odd number. For the start and end points of the specified path, select an appropriate N value to determine the filling width w, so that the generated straight line segments are connected from beginning to end to form a continuous reciprocating straight line path.

[0060] When printing one area and then transitioning to the next printing area, the connection path formed between the filling paths of the two areas is called the transition path. The transition path is not inside the area. Constructing the transition path can make the filling paths in different areas continuous. The specific method for determining the transition path is:

[0061] Printing area for two connected adjacent printing orders of the lower layer To find the transition path between the two paths, first establish two rays r1 and r2 at the end and starting points of the two paths respectively. in, There are two printing areas in the lower layer. The corresponding fill path, Fill paths separately The starting point and end point of Fill paths separately The starting and ending points, s i is the bifurcation point of the lower cross region, are the segmentation points of the m+1th and mth regions of the lower layer, respectively, the proportional coefficients t1, t2∈[0,∞), and then calculate the intersection point u=r1∩r2 of the two rays, and finally take the line segment and line segments For the transition path.

[0062] For the upper print area To the lower printing area The transition path is s i+0.5 =(s i +s i+1 )*0.5 is the interlayer bifurcation point of the lower layer i and the upper layer i+ crossover area, s i+1 is the bifurcation point of the upper cross region. Similarly, the transition point of the interlayer region is calculated as the intersection point of the two rays r3 and r4, v = r3 ∩ r4, where in, To fill the path The end point, To fill the path The starting point, is the segmentation point of the m+1th region in the lower layer, is the segmentation point of the mth region in the upper layer, and the proportional coefficients are t3, t4∈[0,∞). Then the line segment and line segments It forms a transition path between the two areas.

[0063] If it is a T-shaped intersection area, there is no transition path between the two areas of the lower layer, and there is a transition path between the two printing areas of the upper layer and the lower layer as a line segment. and line segments Connection, that is, the transition path is If it is a cross-shaped intersection area, the transition path between the two printing areas in the lower layer is a line segment. and line segments Connection, that is, the transition path is a line segment The transition path between the upper and lower printing areas is a line segment. and line segments Connection, that is, the transition path is

[0064] The above is only a preferred embodiment of the present invention. It should be pointed out that for ordinary technicians in this technical field, several improvements and modifications can be made without departing from the technical principles of the present invention. These improvements and modifications should also be regarded as the scope of protection of the present invention.

Claims

1. A method for additive manufacturing path planning for a cross-type workpiece, characterized in that: The following steps are involved: Step 1, obtain the slicing polygon Q of the cross-shaped workpiece, and determine the center line S of the polygon; Step 2: Determine the intersection area and non-intersection area of ​​the polygon based on the center line; 21) Determine the shortest distance d = min(dist(a,q)) from point a on the center line to polygon Q, and a∈S, q∈Q. The point q on polygon Q at the shortest distance is the support point of a. 22) For any point on the centerline, if the number of centerline segments connected at the point n>2, then let the point be the bifurcation point b, if n=2, then the point is the ordinary center point on the centerline, if n=1, then the point is the endpoint; 23) The area formed by connecting the supporting points corresponding to the bifurcation point b of the center line in sequence is the intersection area; the other areas of the polygon except the intersection area are non-intersection areas; the intersection point of the intersection area polygon and the center line is the division point of the center line; Step 3: determine the printing order of the non-intersection area, and print the non-intersection area in the determined order; and when passing through the intersection area during the printing of the non-intersection area, print the intersection area according to the generated center line of the intersection area as the filling path; For the non-intersecting areas of adjacent upper and lower layers, the angle between the center line dividing point of the area in the same layer and the line connecting the bifurcation point b is the area angle; i+1 represents the upper layer, and i represents the lower layer; 31) First, in the lower layer, select one of the regions with the largest angle as the starting region. The mth area with the smallest angle with the starting area is selected as the next printing area Where m is the region sequence number, m≥1; 32) Then select the mth printing area The corresponding upper layer mth printing area For the next printing area; 33) If there is an unprinted area in the lower layer, select the area in the lower layer that is the same as the mth printed area. The unprinted area with the largest area angle is the next (m+1) printing area. At the same time, m+1 is regarded as m, and then the process goes to step 32) until there is no unprinted area in the lower layer; If there is no unprinted area in the lower layer, select the area in the upper layer area Prints the last print area.

2. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 1, characterized in that: When printing in a non-intersection area or an intersection area, if 2d≤w, d is the shortest distance from a point on the center line to the polygon, and w is the fill width, the fill path of the printing area is a single-pass path, otherwise the fill path is a multi-pass path.

3. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 2, characterized in that: For a single path, fill with the center line as the filling path and 2d as the actual filling width.

4. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 2, characterized in that: For multiple paths, a straight line segment perpendicular to the center line is generated along the center line direction, and the straight line segment is used as the filling path and filled with a filling width w.

5. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 1, characterized in that: In step 3, the steps to generate the center line of the intersection area are: For the upper layer mth printing area The dividing point p of the center line i+1 Move along the center line into the non-intersecting area by a filling width w to form a new segmentation point The corresponding lower layer mth printing area The dividing point p of the center line i A new segmentation point is formed by shrinking 1 / 2 of the filling width w along the center line into the non-intersecting area. The two new split points are connected into a line segment As the center line connecting the upper and lower layers, then connect this line segment with the m+1th printing area of ​​the lower layer. The split point Connect and finally form the center line of the upper and lower intersection areas 6. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 5, characterized in that: The filling width w ranges between the minimum filling width and the maximum filling width allowed by the filling process.

7. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 4, characterized in that: The number of straight line segments is N=L / w, where L is the length of the center line of the printing area and w is the filling width; the length of the straight line segment l=2d-w; if the starting and ending points of the filling path are on the same side of the center line, N is selected as an even number, otherwise N is an odd number.

8. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 1, characterized in that: In step 3, when transitioning to the next printing area after printing one printing area, the connection path formed between the filling paths of the two printing areas is the transition path, and the transition path is constructed to make the filling paths in different areas continuous.

9. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 8, characterized in that the transition The specific method for determining the path is: For the mth and m+1th printing areas in the two adjacent printing orders of the two connections in the lower layer To find the transition path between the two paths, first establish two rays r1 and r2 at the end and starting points of the two paths respectively. Among them, s i is the bifurcation point of the lower cross region, There are two printing areas in the lower layer. The corresponding fill path, Fill paths separately The starting point and end point of Fill paths separately The starting point and end point of are the segmentation points of the m+1th and mth regions of the lower layer, respectively, with proportional coefficients t1, t2∈[0,∞), and then the intersection point of the two rays is calculated u=r1∩r2, then the line segment and line segments For the transition path.

10. The additive manufacturing path planning method for a cross-shaped workpiece according to claim 8, characterized in that: For the upper layer mth printing area Go to the m+1th printing area on the lower layer The transition path is s i+0.5 =(s i +s i+1 )*0.5 for the lower layer 、 The interlayer bifurcation point in the upper crossover region, s i is the bifurcation point of the lower crossover region, s i+1 is the bifurcation point of the upper cross region, and the transition point of the interlayer region is calculated as the intersection point v = r3 ∩ r4 of the two rays r3 and r4. in, There are two printing areas, upper and lower. The corresponding fill path, To fill the path The end point, To fill the path The starting point, is the segmentation point of the m+1th region in the lower layer, is the segmentation point of the mth region in the upper layer, and the proportional coefficients t3, t4∈[0,∞), then the line segment and line segments It forms a transition path between the two areas.

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