JP4969484B2 - Numerical controller - Google Patents

Description

  The present invention relates to a numerical control apparatus that is applied to industrial machines such as machine tools and smoothly interpolates numerical commands.

  A machine tool controlled by a numerical control device (NC device) operates according to a command code called an NC program, and this NC program is created by a CAD / CAM system in die machining or the like.

  In the CAD / CAM system, an NC program is created based on the CAD data. As shown in FIG. 6, while the CAD data a is curved surface data, the generally created NC program b is a small linear command. Is created as an approximation command that is a collection of (generally called a point cloud program). Since the NC program b created in this way is an approximate command that is a collection of minute linear commands, the command trajectory necessarily includes some errors with respect to the CAD data a that is curved surface data.

  Also, when creating NC program b with a CAD / CAM system, tolerance c (allowable error amount from CAD data a) is set due to computational problems, and the straight line command in NC program b is within that allowable error amount. It is created so that the trajectory of can enter.

  The NC program created by the CAD / CAM system contains a command error at the tolerance setting amount level. Therefore, when machining according to the NC program in die machining, etc., as shown in FIG. As shown in FIG. 8, an ideal machining surface is obtained because the machining path is not evenly arranged due to the occurrence of biting due to NC program disturbance (error) e as shown in FIG. It cannot be obtained and the machined surface accuracy deteriorates.

  As a countermeasure against this, as shown in FIG. 9, a process for correcting / correcting the movement command trajectory is performed inside the numerical control device to suppress the deterioration of the machining surface accuracy. That is, a quadratic curve or cubic curve is approximated by the least square method from 7 to 9 points in the vicinity of the command point to be processed, and the command point is corrected and corrected on the curve of the approximated quadratic curve or cubic curve f. (Refer to part g1 in the figure) This process is repeated to correct and correct the command points of the entire NC program.

  The correction / correction processing described above generally creates a quadratic curve or cubic curve f approximated from the NC program b, and corrects / corrects the command trajectory based on the approximated quadratic curve or cubic curve f. As shown in FIG. 10, when correction is performed at the shape part having a sharp angle or the boundary part of the curved surface, on the contrary, it is far from the desired shape such as a rounded corner of the workpiece, and the machining surface accuracy is (Refer to part g2 in the figure).

Therefore, various threshold values are set so as not to perform unnecessary correction processing, but in general,
(1) As shown in FIG. 11, when the inter-block angle θ of the NC program b is smaller than the threshold value (θ <θp (parameter setting value)), the correction process (smoothing process) is invalidated.
(2) As shown in FIG. 12, when the block length L of the NC program b is larger than the threshold (L> Lp (parameter setting value)), the correction process (smoothing process) is invalidated.
(3) As shown in FIG. 13, the distance δ between the approximated quadratic curve or the corrected command point on the cubic curve f and the original command point is larger than the threshold (δ> δp (smoothing tolerance: parameter setting value)) ), The correction process (smoothing process) is invalidated (see g3 in the figure), or the correction / correction process is executed within the threshold as shown in FIG. 14 (see g4 in the figure: Patent Documents) 1),
Thus, an erroneous command locus is not created by unnecessary correction processing.

JP 2004-127099 A

  By the way, by the processing as described above, the correction processing (smoothing processing) in the shape portion with a sharp shape angle becomes almost ideally invalid, but the curved surface boundary portion where the curved surface is in contact cannot be normally recognized. Correction / correction processing may be performed by mistake.

  For example, as shown in FIG. 15, this tendency is particularly noticeable when the quadratic curve fa is used as the approximate curve, and the approximate curve shape is the original CAD / CAM curved surface at the curved boundary portion (inflection point) h. This greatly deviates from the data, resulting in deterioration of the machining shape (see part g5 in the figure). That is, since the part (curved boundary part (inflection point) h) that is originally a high-order curve is approximated by the quadratic curve fa, a command trajectory that is different from the original CAD / CAM curved surface data is created by mistake. It ends up.

  Further, as shown in FIG. 16, when the cubic curve fb is used as the approximate curve, the displacement is not as great as the quadratic curve fa (see FIG. 15) (see g6 in the figure), but the approximate curve is Depending on the command point i of the NC program b, the command point i is different for each machining path, so the approximate curve shape is inevitably different. As a result, the position of the curved boundary portion (inflection point) h may be shifted for each machining pass, resulting in deterioration of the machining shape.

  The present invention has been made in view of the above-described situation, and by smoothly canceling the smoothing process at the curved boundary portion where the curved surface contacts, a smooth command locus is created without destroying the curved surface shape in the original CAD data. An object of the present invention is to provide a numerical control device that can perform the above-described operation.

A numerical control device according to the present invention for achieving such an object,
In a numerical control apparatus for performing a smoothing process at least under an operation restriction by a smoothing tolerance so that a movement command by an NC program follows an approximate curve in a curved surface region,
It has means for recognizing the boundary part of the curved surface, and has an operation restriction processing function for once canceling the smoothing process at the boundary part of the curved surface,
The means for recognizing the boundary portion of the curved surface calculates acceleration at each command point from a plurality of NC program paths , and a portion where the direction of the acceleration vector changes due to a three-dimensional change of the acceleration vector , that is, a Gaussian curvature. There are those that recognize a site 0 as a boundary portion of the curved surface,
It is characterized by that.

  According to the numerical control device of the present invention, if the smoothing process is performed at the boundary portion of the curved surface, a command trajectory different from the curved surface shape in the original CAD data is created and the shape deteriorates. However, by canceling the smoothing process once at the boundary of the curved surface (no correction or correction of the command point is performed), it is possible to create a smooth command trajectory without destroying the curved surface shape in the original CAD data. it can. In addition, the difference in the smoothing operation due to the machining path can be eliminated, and the reciprocal step related to the smoothing process can be suppressed.

  DESCRIPTION OF EMBODIMENTS Hereinafter, a numerical controller according to the present invention will be described in detail with reference to the drawings by way of examples.

  FIG. 1 is an explanatory diagram of operation restriction of smoothing processing by curved surface boundary recognition according to the first embodiment of the present invention, FIG. 2 is an explanatory diagram of operation restriction of smoothing processing by curved surface boundary recognition, and FIG. 3 is a block diagram of the entire apparatus. FIG. 4 is an explanatory diagram of a criterion for determining a curved boundary.

  As shown in FIG. 3, an NC program created based on CAD data (curved surface data) by a CAD / CAM system (not shown) is analyzed by an NC program analysis processing unit 10, and a movement command for each block obtained there is obtained. In general, the movement command for each sampling is sent to the X-axis servo motor 12, the Y-axis servo motor 13 and the Z-axis servo motor 14 via the movement command axis distribution processing unit 11. .

  In this embodiment, the movement command of each block obtained by the NC program analysis processing unit 10 is temporarily stored in the movement amount storage buffer 16 of each block in the smoothing processing unit (operation restriction processing function) 15.

  The smoothing processing unit 15 creates a command trajectory corrected by the corrected command trajectory creation unit 17 based on the movement amount of each block in the movement amount storage buffer 16 of each block. Specifically, after the approximate curve in each curved surface area is created, the command point (end point) of each block is corrected and the command trajectory between the blocks is corrected to create the command trajectory in each curved surface area. This corrected command trajectory is sent to each axis distribution processing unit 11 of the movement command described above.

  At the same time, based on the movement amount of each block in the movement amount storage buffer 16 of each block, an acceleration vector (curvature radius vector) calculation processing unit 18 calculates an acceleration vector (curvature radius vector). Based on the calculation result, When the curved boundary recognition part 19 recognizes the curved boundary part (inflection point) (means for recognizing the curved boundary part), the correction is made by the corrected command trajectory creation part 17 described above. The command trajectory is canceled and the movement command of each block from the movement amount storage buffer 16 of each block described above is sent as it is to each axis distribution processing unit 11 of the movement command described above.

  That is, as shown in FIG. 1 and FIG. 2, after calculating an acceleration vector (curvature radius vector) at each command point of the NC program b, if a portion where the direction of the acceleration vector (curvature radius vector) changes is recognized, This part is determined as a boundary part (inflection point) of the curved surface, and the smoothing process is temporarily canceled, and the command point correction / correction process is not performed (see the region NG in which the smoothing process is temporarily turned off in the figure).

  Then, approximate curves fc and fd are created in each region at the boundary portion (inflection point) of the curved surface, and smoothing processing (command point correction / correction processing) is performed (smoothing processing execution region S1 in the figure). , S2). On the other hand, the boundary portion (inflection point) of the curved surface, that is, the region NG where the smoothing process is temporarily turned off, executes a command based on the command point of the NC program b.

Moreover, as a method of recognizing the boundary part (inflection point) of the curved surface described above, for example, it can be determined by the following equation.

  That is, as shown in FIG. 4, if the inner product of two acceleration vectors is negative, the angle between the two acceleration vectors is 90 degrees or more, so that it can be recognized as an inflection point. There are other methods for recognizing the inflection point, and the method is not limited to the above formula.

  In this way, in the present embodiment, the boundary portion (inflection point) h of the curved surface is recognized, the smoothing process is temporarily turned off, and the command point correction / correction processing is not performed (the NC program b at the curved boundary portion h). Therefore, it is possible to suppress deterioration of the machining shape due to the malfunction of the smoothing process at the boundary portion h of the curved surface, and the smooth command trajectory without destroying the curved surface shape in the original CAD data. Can be created.

  In addition, the difference in the smoothing operation due to the machining path can be eliminated, and the reciprocal step related to the smoothing process can be suppressed.

  FIG. 5 is an explanatory diagram for recognizing a curved boundary due to a change in acceleration in a three-dimensional space, showing Embodiment 2 of the present invention.

  This is because the acceleration (curvature radius) at each command point is calculated from the NC program b, for example, as shown in FIG. 5, the acceleration (curvature radius) is calculated for 7 points × 5 command points, and the acceleration vector 3 A part where the direction of the acceleration vector changes due to a dimensional change (a part where the Gaussian curvature is mathematically 0) is recognized as a boundary part h of the curved surface, and smoothing processing (command point correction / correction processing) is performed at this part. ) Is not performed. In the figure, j is a changing curved surface of an acceleration vector (curvature radius vector). Other configurations are the same as those of the first embodiment, and therefore, a duplicate description is omitted with reference to FIG.

  According to the present embodiment, in addition to the same operations and effects as in the first embodiment, since a plurality of machining paths are used for recognizing the curved boundary portion h, the recognition accuracy of the curved boundary portion h is improved. Benefits are gained.

  The present invention is not limited to the above-described embodiments, and various modifications such as creation of an NC program by CG (Computer Graphics) or a copying apparatus instead of a CAD / CAM system can be made without departing from the gist of the present invention. It goes without saying that it is possible.

It is explanatory drawing of the operation | movement restriction | limiting of the smoothing process by curved surface boundary recognition which shows Example 1 of this invention. It is action explanatory drawing of the operation | movement restriction | limiting of the smoothing process by curved surface boundary recognition. It is a block diagram of the whole apparatus. It is explanatory drawing of the criteria of a curved-surface boundary. It is explanatory drawing of the recognition of the curved surface boundary by the acceleration change in the three-dimensional space which shows Example 2 of this invention. It is explanatory drawing of the NC program created with the CAD / CAM system. It is explanatory drawing of the example in which the joint line of NC program appears on a processing surface. It is explanatory drawing of the example in which disorder of NC program appears on a processing surface. It is explanatory drawing of the correction / correction process of NC program (movement command locus). It is explanatory drawing of the example of malfunction of a smoothing process. It is explanatory drawing of the operation | movement restriction | limiting (inter-block angle) of the smoothing process by a threshold value. It is explanatory drawing of the operation | movement restriction | limiting (block length) of the smoothing process by a threshold value. It is explanatory drawing of the operation | movement restriction | limiting (smoothing tolerance) of the smoothing process by a threshold value. It is explanatory drawing of the operation | movement restriction | limiting (smoothing tolerance) of the smoothing process by a threshold value. It is explanatory drawing of the malfunctioning (in the case of quadratic curve approximation) of the smoothing process in a curved-surface boundary part. It is explanatory drawing of the malfunctioning (in the case of cubic curve approximation) of the smoothing process in a curved-surface boundary part.

Explanation of symbols

a CAD data (curved surface data)
b NC program (point cloud program)
c Tolerance (allowable error from CAD data a)
d NC program joint e NC program disturbance f Approximate quadratic curve or cubic curve fc Approximate quadratic curve or cubic curve in smoothing process execution area S1 fd Approximate quadratic curve or 3 in smoothing process execution area S2 Quadratic curve fa quadratic curve fb cubic curve h curved surface boundary (inflection point)
θ Inter-block angle L Block length δ Distance between correction command point and original command point S1 Smoothing process execution area S2 Smoothing process execution area NG Area where smoothing process is temporarily turned off 10 NC program analysis processing part 11 Distribution of each axis of movement command Processing unit 12 X-axis servo motor 13 Y-axis servo motor 14 Z-axis servo motor 15 Smoothing processing unit 16 Movement amount storage buffer of each block 17 Modified command trajectory creation unit 18 Acceleration vector calculation processing unit 19 Curve boundary boundary Recognition processing unit

Claims (1)

In a numerical control apparatus for performing a smoothing process at least under an operation restriction by a smoothing tolerance so that a movement command by an NC program follows an approximate curve in a curved surface region,
It has means for recognizing the boundary part of the curved surface, and has an operation restriction processing function for once canceling the smoothing process at the boundary part of the curved surface,
The means for recognizing the boundary portion of the curved surface calculates acceleration at each command point from a plurality of NC program paths , and a portion where the direction of the acceleration vector changes due to a three-dimensional change of the acceleration vector , that is, a Gaussian curvature. There are those that recognize a site 0 as a boundary portion of the curved surface,
A numerical controller characterized by that.

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