Closed spline curve CNC machining tool path algorithm

Abstract

The invention discloses a closed spline CNC machining tool path algorithm, and aims to provide a tool path algorithm which can be suitable for tool path calculation of any plane figure, and a corresponding machining path can be automatically generated by inputting a profile curve of a workpiece, a cutting depth and a tool radius. According to the closed spline CNC machining tool path algorithm, a closed spline graph machining tool path can be rapidly and conveniently adjusted on an industrial site. The method comprises the following specific steps: S1, defining a data structure; s2, calculating vectors of adjacent points; s3, unit vector normalization is carried out; s4, calculating a new target point; and S5, traversing the contour to generate a new curve. The method is applied to the technical field of turning machining.

Description

Technical Field

[0001] The present invention is applied to the technical field of turning machining, and particularly relates to a closed spline curve CNC machining tool path algorithm. Background Art

[0002] In the field of numerical control turning machining, the planning and editing of the turning tool path of a workpiece are key steps to ensure the precise machining of the part. In the past, it was usually technical personnel with professional knowledge who edited the G-code tool path on the machine tool to achieve the machining of the workpiece. In recent years, thanks to the rapid development of computers, some CAM software has emerged to assist in editing and generating the turning path of the workpiece. However, these software still require technical personnel with corresponding knowledge to edit and operate, and still cannot be widely promoted and applied on a large scale. Currently, the main planning and editing of the turning tool path of the workpiece need to use professional tool software to edit and produce the tool path file, such as AutoCAD, CAM software, etc., and have high requirements for the professional skills of the operator. This method is difficult to quickly and effectively compensate for the tool radius. Every time the tool radius changes, it is necessary to use professional tool software to recalculate and edit the tool path file again. If a tool path calculation that can be applied to any planar graph can be designed, and the contour curve of the workpiece, the cutting depth, and the tool radius are input, the corresponding machining path can be automatically generated, and the closed spline curve CNC machining tool path algorithm for quickly and conveniently adjusting the closed spline curve graph machining tool path at the industrial site can solve the above problems. Summary of the Invention

[0003] The technical problem to be solved by the present invention is to overcome the deficiencies of the prior art, and provide a closed spline curve CNC machining tool path algorithm that can be applied to the tool path calculation of any planar graph. By inputting the contour curve of the workpiece, the cutting depth, and the tool radius, the corresponding machining path can be automatically generated, and the closed spline curve graph machining tool path can be quickly and conveniently adjusted at the industrial site.

[0004] The technical solution adopted by the present invention is as follows: The present invention includes the following specific steps: Step S1, data structure definition; Step S2, adjacent point vector calculation; Step S3, unit vector normalization; Step S4, calculate the new target point; Step S5, traverse the contour to generate a new curve; For the inshrinkage or outexpansion of the planar graph in Step S4, the distance between two adjacent sides is the same distance dis, where the cutting depth is h and the tool radius is r. Therefore, the distance dis between adjacent sides = h + r; At this time, take the included angle θ between vector D and PP1, and calculate the distance v of vector D on the PP1 vector according to θ, that is: cosθ = Dunit * D1 / |Dunit| * |D1|; The distance v of vector D on the PP1 vector = dis * cosθ; Then calculate the scaling ratio k, and the scaling ratio satisfies k * v = dis, that is: k = dis / v; The final offset direction vector is d = k * Dunit, and the new point outward expansion compensation coordinate set L1 and the inward contraction compensation coordinate set L2 are: L1 = Pi + d; L2 = Pi - d.

[0005] Furthermore, in step S1, an ordered point set C = {P0, P1,..., Pn−1} is input according to the workpiece contour to form a contour curve. When the contour curve is a closed polygon, Pn = P0.

[0006] Furthermore, in step S2, the current point P is selected from the ordered point set C in step S1. The left and right adjacent points P1 and P2 of P form two vectors with point P, and the unit vectors D1 and D2 of the P1 vector and the P2 vector are taken.

[0007] Furthermore, in step S3, the vector magnitudes of the unit vector D1 and the unit vector D2 are both 1. Add the D1 and D2 vectors to find the unit vector D of the vector for inward contraction or outward expansion, that is: D = D1 + D2.

[0008] Furthermore, if the contour is clockwise, D points to the inside; if it is counterclockwise, it needs to be negated; if |D| ≠ 0, the final direction unit vector is: Dunit = D / |D|.

[0009] Furthermore, when the adjacent sides are collinear, |D| = 0, and directly offset along the normal direction.

[0010] Furthermore, in step S5, two actual target points L1 and L2 are obtained according to the two vectors, the cutting depth, and the tool radius, and they are connected to form a new contour.

[0011] Furthermore, insert an arc transition in the high curvature area to avoid sudden changes in the tool path.

[0012] The beneficial effects of the present invention are: This application is a real-time input interface. Only three parameters, namely the contour point set, the cutting depth h, and the tool radius r, are required to generate the machining tool path online. There is no need for cumbersome operations. The offset distance is dynamically adjusted through the formula dis = h + r. There is no need to regenerate the underlying geometric data. Only the parameters need to be updated and the point set needs to be traversed again. It can be applied to the tool path calculation of any planar graph. By inputting the contour curve of the workpiece, the cutting depth, and the tool radius, the corresponding machining path can be automatically generated, and the machining tool path of the closed spline curve graph can be quickly and conveniently adjusted in the industrial field. Description of the Drawings

[0013] Figure 1 is a schematic diagram for generating the machining profile of the workpiece; Figure 2 is a schematic diagram of the unit vector in the present invention; Figure 3 is a schematic diagram of the contracted unit vector in the present invention; Figure 4 is a schematic diagram of the contracted and expanded points in the present invention. Detailed Description of the Invention

[0014] As Figures 1 to 4 shown, in this embodiment, the present invention includes the following specific steps: Step S1, data structure definition; Step S2, calculation of adjacent point vectors; Step S3, normalization of the unit vector; Step S4, calculation of the new target point; Step S5, traversing the profile to generate a new curve; In step S4, for the contraction or expansion of the planar figure, the distances between two adjacent sides are the same distance dis, where the cutting depth is h and the tool radius is r. Therefore, the distance dis between adjacent sides = h + r; At this time, take the angle θ between the vector D and PP1, and calculate the distance v of the vector D on the PP1 vector according to θ, that is: cosθ = Dunit * D1 / |Dunit| * |D1|; The distance v of the vector D on the PP1 vector = dis * cosθ; Then calculate the scaling ratio k, and the scaling ratio satisfies k * v = dis, that is: k = dis / v; Finally, the offset direction vector is d = k * Dunit, and the new point outward expansion compensation coordinate set L1 and the inward contraction compensation coordinate set L2 are: L1 = Pi + d; L2 = Pi - d.

[0015] As Figure 1 and Figure 2 shown, in this embodiment, in step S1, an ordered point set C = {P0, P1,..., Pn−1} is input according to the workpiece profile to form a profile curve. When the profile curve is a closed polygon, Pn = P0.

[0016] As Figure 2 shown, in this embodiment, in step S2, the current point P is selected from the ordered point set C in step S1. The left and right adjacent points P1 and P2 of P form two vectors with point P, and the unit vectors D1 and D2 of the P1 vector and the P2 vector are taken.

[0017] As Figure 2, as shown, in this embodiment, the vector magnitudes (norms) of the unit vectors D1 and D2 in step S3 are both 1. Add the vectors D1 and D2 to find the unit vector D of the vector for inward or outward contraction, that is: D = D1 + D2.

[0018] As Figure 3 shown, in this embodiment, if the contour is clockwise, D points inward; if it is counterclockwise, it needs to be inverted; if |D| ≠ 0, the final direction unit vector is: Dunit = D / |D|. Thus, it can be seen that it is inverted or judged by the cross product symbol.

[0019] As Figure 3 shown, in this embodiment, when adjacent sides are collinear, |D| = 0, and it is directly offset along the normal direction.

[0020] As Figure 1 and Figure 4 shown, in this embodiment, in step S5, two actual target points L1 and L2 are calculated according to two vectors, the cutting depth, and the tool radius, and they are connected to form a new contour.

[0021] As Figure 1 and Figure 4 shown, in this embodiment, an arc transition is inserted into the high-curvature region to avoid sudden changes in the tool path. Thus, it can be seen that an arc transition is inserted into the high-curvature region (such as an angle < 90°) to avoid sudden changes in the tool path.

[0022] The working principle of the present invention: Step S1, data structure definition; Step S2, adjacent point vector calculation; Step S3, unit vector normalization; Step S4, calculation of new target points; Step S5, traversing the contour to generate a new curve.

[0023] Although the embodiments of the present invention are described with actual solutions, they do not constitute a limitation to the meaning of the present invention. For those skilled in the art, modifications to its implementation solutions according to this specification and combinations with other solutions are obvious.

Claims

1. A CNC machining tool path algorithm for closed spline curves, characterized in that: It includes the following specific steps: Step S1, data structure definition; Step S2, adjacent point vector calculation; Step S3, unit vector normalization; Step S4, calculate the new target point; Step S5, traverse the contour to generate a new curve; In step S4, for the inward or outward expansion of the planar figure, the distances between two adjacent sides are the same distance dis, where the cutting depth is h and the tool radius is r. Therefore, the distance between adjacent sides dis = h + r; At this time, take the angle θ between vector D and PP1, and calculate the distance v of vector D on the PP1 vector according to θ, that is: cosθ = Dunit * D1 / |Dunit| * |D1|; The distance v of vector D on the PP1 vector is v = dis * cosθ; Then calculate the scaling ratio k, and the scaling ratio satisfies k * v = dis, that is: k = dis / v; Finally, the offset direction vector is d = k * Dunit, and the new point outward expansion compensation coordinate set L1 and inward contraction compensation coordinate set L2 are: L1 = Pi + d; L2 = Pi - d.

2. The CNC machining tool path algorithm for a closed spline curve according to claim 1, wherein: In step S1, an ordered point set C = {P0, P1,..., Pn−1} is input according to the workpiece contour to form a contour curve. When the contour curve is a closed polygon, Pn = P0.

3. The CNC machining tool path algorithm for a closed spline curve according to claim 2, characterized in that: In step S2, select the current point P in the ordered point set C in step S1. The left and right adjacent points P1 and P2 of P form two vectors with point P, and the unit vectors D1 and D2 of the P1 vector and the P2 vector are taken.

4. The CNC machining tool path algorithm for a closed spline curve according to claim 3, wherein: In step S3, the vector magnitudes of the unit vector D1 and the unit vector D2 are both 1. Add the D1 and D2 vectors to find the unit vector D of the vector in the inward or outward expansion direction, that is: D = D1 + D2.

5. The CNC machining tool path algorithm for a closed spline curve according to claim 4, characterized in that: If the contour is clockwise, D points to the inside; if it is counterclockwise, it needs to be negated; if |D| ≠ 0, the final direction unit vector is: Dunit = D / |D|.

6. The CNC machining tool path algorithm for a closed spline curve according to claim 5, characterized in that: When the adjacent sides are collinear, |D| = 0, and directly offset along the normal direction.

7. The CNC machining tool path algorithm for a closed spline curve according to claim 5, characterized in that: Step S5 calculates two actual target points L1 and L2 based on two vectors, the cutting depth, and the tool radius, and connects them into a new contour 。 8. A CNC machining tool path algorithm for a closed spline curve according to claim 7, characterized in that: Insert an arc transition in the high curvature area to avoid sudden changes in the tool path.

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