JP2007200037A - Numerical control device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a numerical control device for improving working efficiency by shortening the moving time of a pick feed without damaging the quality level of a working surface. <P>SOLUTION: This numerical control device includes a pick feed section judging device 11 for extracting a pick feed part connecting a cut path and the other cut path from a working program; a cut path block dividing device 12 for dividing the pre-and-post cut path blocks of the pick feed section into a real cut path section block for making a tool actually cut a workpiece, a saving path section block for making the tool save from the workpiece after passing the workpiece and an approach path section block for making the tool approach the next real cut path; and a pick feed section curving device 13 for replacing a series of paths configured of the saving path section, the pick feed section and the approach path section with a high-order NURBS curve whose curvature continues at an arbitrary point on a curve. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a numerical control apparatus that controls movement of each feed axis of a machine tool, and more particularly to a numerical control apparatus that controls movement of a feed axis by a machining program having a pick feed.

  In machine tools that process dies and the like, the process of connecting the cutting path, which is the trajectory of the tool that cuts the workpiece, by pick feed (the movement path of the tool at the cutting completion part not involved in cutting of the workpiece) Including machining program in general.

  FIG. 3 shows an example of machining by a machining program constituted by a cutting path and a pick feed. The X-axis direction is a cutting path for reciprocating the tool, and the Y-axis direction is a pick feed. As shown in this figure, the operation of the machine tool during machining includes the actual cutting operation in which the tool is on the workpiece and the workpiece is actually cut along the cutting path, and the tool passes through the workpiece and performs cutting. Air cut retreat operation that retracts the tool from the workpiece along the path, pick feed that transfers to the next cutting path, and air cut approach operation that causes the tool to approach the work along the changed cutting path The actual cutting operation of cutting the workpiece along the cutting path again is continuously performed. At this time, since the starting point and the ending point are corners in the pick feed, the operation speed of the tool is greatly reduced in this portion even though it is a non-cutting region, which causes a reduction in machining efficiency.

  An example of the prior art for solving this problem is shown in FIG. 4 (for example, Patent Document 1). In the drawing, there is shown an example in which there is a cutting path in the X-axis direction and this is connected by pick feed in the Y-axis direction. In this example, the air movement between the pick-feed operation in the Y-axis direction, the retraction operation in the X-axis direction, and the close-up operation is not performed instead of the axial operation in the order of “retraction operation → pick feed → close operation” shown in FIG. Done in parallel. In the Y-axis direction, which is the pick-feed direction, acceleration starts from speed 0 when the actual cutting operation is completed, and deceleration is completed when the point reaches the point where the actual cutting operation of the next cutting path is started. 0. In the X-axis direction, the speed is made to follow the acceleration / deceleration in the Y-axis direction so that the movement time in the Y-axis direction is as short as possible. Thereby, the time required for the pick-feed operation can be reduced as compared with the case where each operation is performed one block at a time in the order of “retraction operation → pick feed → contact operation”.

JP 2000-89814 A

  When actually processing a workpiece, it is important to shorten the processing time in order to increase the processing efficiency, but it is also important to maintain and improve the quality of the processed surface of the workpiece. For this reason, it is necessary to feed the shaft so as not to cause mechanical vibration during machining.

  In order to perform machining so as not to generate mechanical vibration, it is necessary that the tool movement path is always connected smoothly so that the tangent direction and curvature do not change suddenly at any point on the movement path. However, in the above prior art, attention is focused on speed control when shortening the time required for the pick feed portion, and there is a possibility that degradation of the machined surface quality becomes a problem when actually processing a workpiece.

  In the above prior art, acceleration starts in the direction of the pick feed when the tool passes over the work piece. As the direction of the pick feed, a direction perpendicular to or close to the direction of the cutting path is assumed. ing. However, in general, as shown in FIG. 5, the direction of the pick feed depends on the shape of the target workpiece, so there is no guarantee that the direction is perpendicular to the cutting path. For this reason, it is difficult to apply the above-described conventional technique to a general shape of a workpiece.

  In the above prior art, acceleration starts in the direction of pick feed when the tool passes on the cutting path. For this purpose, it is necessary to accurately grasp the position where the tool passes on the workpiece.

  In order to realize this, whether the block is a retraction operation block, a pick feed block, or a close-up operation block in the axis movement command block specified in the machining program input to the numerical controller. It is necessary to attach an identifier indicating The process of attaching an identifier indicating that this is an axis movement command block of the pick feed needs to be performed in a CAM (Computer Aided Manufacturing) process for generating a machining program. The prior art cannot be applied. In addition, it is essential to use a CAM system that can perform the process of attaching an identifier.

  In order to solve the above-described problems, the present invention reads a machining program in which a cutting path of a tool for cutting a workpiece is composed of a plurality of line segment data in numerical control for controlling the movement of each feed axis of a machine tool. An analysis means for extracting line segment data of the cutting path portion connecting the cutting paths to each other and cutting path portions respectively connected to both ends thereof from the machining program; and a pick feed portion extracted by the analysis means Dividing means for dividing the line segment data of each cutting path portion connected to both ends of the workpiece into an actual cutting path portion where the tool cuts the workpiece by a dividing point and an air cut portion where the tool is separated from the workpiece; A slip that has a dividing point as a starting point and a tangent direction, and the tangential direction and curvature substantially coincide with the tangential direction and curvature of the actual cutting path portion at each dividing point and gradually change between the starting point and the ending point on the curve. Seeking a curve, to provide a numerical control apparatus characterized by having a curved means to replace the curve of the pick-feed unit and the air-cut portion.

  In order to solve the above-described problem, the present invention provides the numerical control apparatus, wherein the curving means uses the division points as start and end points, and a tangential direction and a curvature at the division points. A high-order NURBS curve that substantially matches the tangential direction and curvature of the actual cutting path portion and gradually changes between the start and end points on the curve is obtained, and the pick feed portion and the air cut portion are replaced with the curve. A numerical control device is provided.

  In order to solve the above-mentioned problem, the present invention provides the numerical control apparatus, wherein the curving means includes a path deviation amount that is a distance between a curve to be obtained and a line segment of the air cut part and the pick feed part. Provides a numerical control device characterized by obtaining a curve that falls within a preset allowable value.

  The pick feed moving time can be shortened and the processing efficiency can be improved without impairing the processing surface quality.

  Further, the above-described effect can be obtained even if conventional NC (Numerical Control) data that is not designated as a retraction operation block, a pick feed block, or a close-up operation block is used for the axis movement command block in the machining program.

  A first embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a block diagram showing a first embodiment of the present invention, and FIG. 6 is a diagram showing a curving state of a pick feed block in the embodiment of the present invention.

  In FIG. 1, a program input device 1 inputs and analyzes a machining program and outputs feed axis movement command block data C.

  The pick-feed unit determination device 11 inputs feed axis movement command block data C, and this feed axis movement command block data C is a cutting path block that is an axis feed command block on a cutting path for cutting a workpiece. Pick feed portion determination condition data stored in the pick feed portion determination condition data storage device 21 indicates whether it is data or data of a pick feed block that is a pick feed portion that connects a cutting path and another cutting path. Determine based on Dp. When it is determined that the feed axis movement command block data C is data of the cutting path block, the pick feed unit determination device 11 outputs the feed axis movement command block data C as the cutting path block data Bc. If the feed block is determined to be a feed block, the feed axis movement command block data C is output as pick feed block data Bp.

  As the determination processing performed by the apparatus 11, for example, the line segment length of the target feed axis movement command block data C is within a preset length, and the line segments indicated by the block data before and after the block data C are When the parallel condition is satisfied, the target feed axis movement command block data C is determined to be pick feed block data.

  For example, as shown in FIG. 6A, when the continuous coordinate points specified by the feed axis movement command block data C are P0, P1, P2, and P3, and the preset set length is Lp. The line segment length L12 of the line segment P1-P2 is within the preset set length Lp, and P0-P1 and P2-P3 which are line segments before and after this line segment are parallel to each other. If it is, the feed axis movement command block data C indicated by the line segment P1-P2 is determined to be pick feed block data.

  For example, as shown in FIG. 7A, the continuous coordinate points specified by the feed axis movement command block data are P0c, P0b, P0a, P1, P2, P3a, P3b, P3c,. When the line segment length of each line segment is relatively short and block data approximating a free-form surface is assumed, the blocks before and after the pick feed portion are parallel or approximately parallel as shown in FIG. This makes it difficult to make a determination. In this case, for example, a method of changing the conditions as follows can be used.

  In the line segments P0a-P1 and P2-P3a, a series of blocks that are continuous from the respective line segments by a preset number of continuous blocks Nc are considered. For example, when Nc = 3, the continuous series of line segments are P0c-P0b, P0b-P0a, P0a-P1, and P2-P3a, P3a-P3b, P3b-P3c. Here, with respect to the continuous series of blocks, an angle formed by two connecting line segments is not less than a preset angle α, and a line segment connecting the start point and the end point of the continuous series of blocks, When the angle formed by the line segment connecting the start point and the end point of the continuous block after P1-P2 is less than the preset angle β (FIG. 7B), the line segment P1-P2 indicates It is determined that the feed axis movement command block C is pick feed block data.

  Of course, the determination condition is not limited to the above condition, and can be set as needed.

  In the cutting path block dividing device 12, the cutting path block data Bc is block data of cutting paths before and after the pick feed based on the cutting path block dividing condition data Dv stored in the cutting path block dividing condition data storage device 22. If the tool is on the workpiece, the actual cutting path is the part where the cutting is actually performed, and after the tool passes over the workpiece, it is retracted from the workpiece and moved to the pick feed starting point by air cut. Is divided into a retraction path section and an approach path section in which the tool moves toward the next actual cutting path section from the end point of the pick feed by air-cutting, and the block data of the retraction path section and the close-up path section are retreated respectively. The path block data Be and the approach path block data Ba are used, and the remaining actual cutting path part is a new cutting path block. And outputs it as over data Bc. If the cutting path block data Bc is not block data of the cutting path before and after the pick feed, the cutting path block data Bc is output as it is as the cutting path block data Bc.

  As the determination processing performed by the apparatus 12, for example, the line length defined by the cutting path block division condition data Dv from the intersection with the pick feed among the line segments defined by the cutting path block, The approaching path part is used, and the remaining part is the actual cutting path part.

  For example, as shown in FIG. 6B, when the block length defined as the cutting path block division condition data is Ld, a line segment P0-P1 is separated from the pick feed starting point P1 by a point Pd1. The line segment P2-P3 is divided by a point Pd2 that is separated from the pick feed end point P2 by Ld, and the block corresponding to the line segment Pd1-P1 is saved as a retreat path part, and the block corresponding to the line segment Pd2-P2 is approached path Blocks corresponding to the line segments P0-Pd1 and Pd2-P3, which are the remaining portions, are defined as actual cutting path portions.

  Further, for example, as the cutting path block division condition data, a boundary plane Pd that is a plane that divides a cutting path area and a non-cutting path area is assumed. For example, as shown in FIG. 8, when the boundary plane Pd defined as the cutting path block division condition data is used, the intersections of the line segments P0-P1 and the boundary plane Pd are Pd1, P2-P3, and the boundary plane Pd. As shown in FIG. 6B, the line segment is divided by Pd1 and Pd2.

  Of course, the determination condition is not limited to the above condition, and can be set as needed.

  In the pick feed section curving device 13, the block data immediately before the save path block data Be among the pick feed block data Bp, the save path block data Be, the approach path block data Ba, and the cutting path block data, and The block data Bc immediately after the approach path block data Ba is input, and a path specified by a series of block data of the retract path block data Be, the cutting path block data Bc, and the approach path block data Ba is indicated on the curve. It is replaced with a higher-order NURBS curve (Non-Uniform Rational B-Spline curve) that satisfies the condition that there is no sudden change in tangent direction and curvature at any point, and this replaced curve data is curved pick feed block data Br Output as.

  An example of an embodiment of the curving process performed by the apparatus 13 is shown below. In this example, as the NURBS curve to be replaced, a third-order NURBS curve that mathematically guarantees that there is no sudden change in the direction of the tangent and the curvature at any point on the curve is used. Using this tertiary NURBS curve as the starting point of the evacuation route, the start point and end point of the pick feed, and the end point of the close route as the control points of the tertiary NURBS curve, the tertiary NURBS curve passes through the start point of the save route and the end point of the close route. The determination is made under the condition that the tangent direction and the curvature coincide at the start point of the retreat route and the end point of the approaching route.

  For example, as shown in FIG. 6 (c), the line segments Pd1-P1, P1-P2 and P2-Pd2 have NURBS curve control points Pd1, P1, P2, Pd2, and the NURBS curve has Pd1, Pd2. As described above, the tangential direction and the curvature at Pd1 and Pd2 are replaced with a cubic NURBS curve that satisfies the condition that the tangential direction and the curvature at the division points Pd1 and Pd2 before being replaced with the curve are the same, and this curved line portion is replaced. The specified block is a curvilinear pick feed block.

  The curving process is an example of the embodiment, and is not limited to the above processing contents under the condition that it is guaranteed that there is no sudden change in the tangential direction and the curvature at an arbitrary point on the curve. , And can be set as necessary.

  In the above embodiment, the pick feed unit determination condition data storage device 21 stores pick feed unit determination condition data Dp, which is a condition for the determination process in the pick feed unit determination device 11.

  Further, the cutting path block division condition data storage device 22 stores cutting path block division condition data Dv, which is a condition at the time of block division processing by the cutting path block division apparatus 12.

  In the function generator 2, a function is generated based on the cutting path block data Bc output from the cutting path block dividing apparatus 12 and the curvilinear pick feed block data Br output from the pick feed section curving apparatus 13. Interpolated position data P, which is position data for each feed axis, is output.

  The feed axis driving device 3 controls the movement of each feed axis of the machine based on the interpolation position data P.

  In the above embodiment, the feed axis movement command block in the machining program is automatically determined as to whether it is a retreat path block, a pick feed block, or a close path block, and this series Is replaced with a curved pick feed block, but in the axis movement command block specified in the machining program, is that block a retract path block, a pick feed block or a close path block? By adding an apparatus that determines the identifier and determines the determined blocks as a save route block, a pick feed block, and a close-up route block, respectively, in the above embodiment. For machining programs with specified identifiers Invention can be readily applied.

  A second embodiment of the present invention will be described based on FIG. FIG. 2 is a block diagram showing a second embodiment of the present invention. In the present embodiment, the pick feed path of the curving pick feed block to be replaced and the original retreat path block Be, the pick feed block Bp, and the close path block Ba are used for the curving performed by the pick feed section curving device 13. In this embodiment, a curve is formed so that a path deviation amount that is a distance deviated from each path falls within an allowable error amount specified in advance.

  A replacement curve is determined in a process of replacing a path defined by a series of blocks constituted by a continuous path block, a pick-feed block, and an approach path block, which is performed in the pick-feed unit curving device 13, with a curve. As a condition to perform the curve, add the condition that the path deviation amount, which is the distance from the series of blocks to be replaced to the replacement curve, is within the allowable error amount specified in advance. To do.

  The permissible replacement error data storage device 23 stores permissible replacement error data Dt corresponding to the permissible replacement error.

  An example of an embodiment in which the path deviation amount, which is a deviated distance from the series of paths to be curved to the replacement curve, is performed within the allowable error amount specified in advance in the apparatus will be described below.

  First, a replacement curve is created by the same method as that described with reference to FIG. 6C (FIG. 9A). This curve is Nr (t). t is a parameter. Next, an area within which the perpendicular extending from the series of line segments Pd1-P1-P2-Pd2 before replacement is within the replacement error allowable value ε set as the replacement error allowable value data Dt is replaced with a replacement error allowable area. (FIG. 9B). Next, it is confirmed whether the curved replacement curve is within the replacement error allowable area (FIG. 9C). This is to determine the distance between an arbitrary point on the curve Nr (t) and Pd1-P1, P1-P2, P2-Pd2, and easily determine whether the minimum value is within the replacement error allowable value ε. I can do it. At this time, if the minimum value of the distance is within the replacement error allowable value ε, the curve Nr (t) is determined as a curvilinear pick feed block. If there is a portion where the minimum value of the distance exceeds the replacement error allowable value ε (FIG. 9D), the curve Nr (t) is recalculated so as to be within the replacement error allowable value ε.

  As a recalculation method, for example, there is a method of increasing a weight value which is one of the coefficients of the NURBS curve. Since the weight value has a mathematical feature that the NURBS curve approaches the control point as the value increases, the weight value is calculated using this feature so that the NURBS curve falls within the replacement error allowable area ( FIG. 9 (e)), the curve Nr (t) at this time is determined as a curvilinear pick feed block.

  Other parts similar to those in the first embodiment are denoted by the same reference numerals, and description thereof is omitted.

The block diagram showing the 1st Embodiment of this invention. The block diagram showing the 2nd Embodiment of this invention. The figure which shows the example of a process by the process program which connected the cutting path | route with the pick feed. The figure which shows the example of speeding-up of the pick feed by a prior art. The figure which shows the example of a general pick feed. The figure which shows the mode of curving of the pick feed block by this invention. The figure which shows the mode of the other curve-ization by this invention. The figure which shows an example of the division | segmentation means by this invention. The figure which shows a mode that the path | route deviation | shift amount is stored in tolerance within the curving by this invention.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 Program input device, 2 Function generator, 3 Feed axis drive device, 11 Pick feed part determination device, 12 Cutting path block dividing device, 13 Pick feed part curving device, 21 Pick feed part judgment condition data storage device, 22 Cutting Path block division condition data storage device, 23 Replacement error tolerance data storage device.

Claims (3)

In numerical control that controls the movement of each feed axis of a machine tool,
A cutting path of a tool for cutting a workpiece is read by a machining program consisting of a plurality of line segment data, and a pick feed section for connecting the cutting paths to each other and a line segment of a cutting path section connected to both ends of the pick feed section. Analyzing means for extracting data from the machining program;
Line segment data of each cutting path portion connected to both ends of the pick feed portion extracted by the analyzing means, an actual cutting path portion where the tool cuts the workpiece by the dividing point, and an air cut portion where the tool leaves the workpiece Dividing means to divide into
A smooth curve having each division point as a start and end point, and the tangential direction and curvature substantially coincide with the tangential direction and curvature of the actual cutting path portion at each division point and gradually change between the start and end points on the curve. And a curving unit that replaces the pick-feed unit and the air-cut unit with the curve. The numerical control apparatus according to claim 1,
The curving means uses the division points as start and end points, and the direction and curvature of the tangent line substantially match the direction and curvature of the tangent line of the actual cutting path portion at the division points, and between the start and end points on the curve. A numerical control apparatus characterized by obtaining a gradually changing high-order NURBS curve and replacing the pick feed part and the air cut part with the curve. In the numerical control device according to claim 1 or 2,
The curving means obtains a curve in which a path deviation amount, which is a distance between a curve to be obtained and a line segment of an air cut part and a pick feed part, falls within a preset allowable value. apparatus.

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