JP5197640B2 - Machining simulation apparatus and numerical control apparatus - Google Patents

Description

  The present invention relates to a machining simulation device and a numerical control device, and more particularly to a machining simulation device that simulates a machining shape by a machine tool.

  In machining using an NC machining program created by a CAM system or the like, machining defects that may result in a finish different from the intention of the machining designer may occur. Factors that cause machining failures include, for example, a problem with the prepared machining program itself, or a case where the machine tool does not follow the instructions of the machining program due to inappropriate machining conditions or adjustment of the machine tool. is there. In the case of cutting, particularly when there is a problem with the machining program, it is said that machining defects often appear as uncut or overcut. In order to avoid such machining defects, a CAM system that prepares a machining program is usually equipped with a function for verifying the program by simulation.

  As for program verification by simulation, a technique of manually confirming a simulation result shape (hereinafter referred to as “target shape” as appropriate) to be verified can be adopted for an obvious defect. For more detailed verification, there is a case where a method of graphically displaying a comparison result between a reference shape and a target shape based on CAD model data used for creating a program may be employed. In the case of cutting, the size of uncut or excessively cut is represented by, for example, grayscale display or color-coded display. The amount of uncut or overcut is represented by, for example, the degree of deviation of the target shape from the reference shape, using the distance between the surfaces of the two shapes as an index. Here, since the calculation load increases when the distance between the entire surface of the target shape and the reference shape is measured one by one, a technique for enabling simple verification has been proposed. For example, Patent Document 1 proposes a method of expanding shape data related to verification of a machining program in the direction of the observation axis and discriminating uncut or overcut according to the distance in the direction of the observation axis. By making verification possible by comparing the distances in the axial direction, the calculation load for verification is reduced.

JP-A-7-129221

  The distance between the reference shape and the target shape in the observation axis direction changes depending on the angle formed by the processed surface and the observation axis. In this case, the difference in distance varies depending on the inclination of the processed surface even when the uncut portion is left unfinished or excessively cut, making quantitative shape comparison difficult. Another problem is that the method using the deviation distance from the reference shape as an index only covers specific forms of various machining defects to be verified. In particular, when machining a highly designed part that uses a large number of curved surfaces, such as mold processing, it is important to have a smooth finished surface. If it is not always necessary to treat as a machining defect if there are uncut or overcut evenly over a certain range of the finished surface, the discrimination based on the separation distance hinders verification, which is a serious defect. For example, there is a problem that a processing flaw or processing unevenness may be overlooked.

  The present invention has been made in view of the above, and an object of the present invention is to obtain a machining simulation device and a numerical control device that are capable of discriminating machining defects and easily estimating the cause of machining defects.

  In order to solve the above-described problems and achieve the object, the present invention relates to the shape of the workpiece expressed by the distance field model based on the tool movement data generated under predetermined simulation conditions of the cutting process. A cutting simulation unit that simulates by updating a field model, and a reference standard shape is designated from a simulation result in the cutting simulation unit, and is based on the tool movement data generated under the simulation conditions different from the reference standard shape A comparison target selection unit that selects a comparison target shape from a simulation result; a shape drawing processing unit that executes a rendering process for graphically displaying the simulation result selected as the comparison target shape by the comparison target selection unit; Cutting simulation section A simulation execution control unit that controls the comparison target selection unit and the shape drawing processing unit, and the shape drawing processing unit includes a projection plane on which pixels are arranged in the rendering process, and a projection on the projection plane. The intersection position of the comparison target shape and the light beam is calculated on the assumption of a light beam along a projection direction that is a direction perpendicular to the projection plane from each of the pixels, and a sign for the reference standard shape is calculated at the intersection position. The luminance value of the pixel is determined based on a distance value and a difference between secondary geometric feature amounts derivable from a distance field.

  According to the present invention, it is possible to determine a machining defect and easily estimate the cause of the machining defect.

FIG. 1 is a block diagram illustrating a configuration of a machining simulation apparatus according to the first embodiment. FIG. 2 is a diagram for explaining the process of calculating the intersection position, the calculation of the signed distance value, and the calculation of the distance gradient vector in the rendering process. FIG. 3 is a diagram for explaining a process of determining a new projection direction in the shape drawing processing unit. FIG. 4 is a block diagram showing the configuration of the numerical control apparatus according to the third embodiment.

  Embodiments of a machining simulation apparatus and a numerical control apparatus according to the present invention will be described below in detail with reference to the drawings.

Embodiment 1 FIG.
FIG. 1 is a block diagram showing a configuration of a machining simulation apparatus 1 according to Embodiment 1 of the present invention. The machining simulation apparatus 1 includes a simulation execution control unit 2, a cutting simulation unit 3, a comparison target selection unit 4, a shape drawing processing unit 5, and a shape data storage unit 6.

  The simulation execution control unit 2 controls the cutting simulation unit 3, the comparison target selection unit 4, and the shape drawing processing unit 5. The cutting simulation unit 3 simulates the shape of the workpiece expressed by the distance field model. The comparison target selection unit 4 selects a comparison target shape from the simulation result in the cutting simulation unit 3. The shape drawing processing unit 5 executes a rendering process for graphically displaying the simulation result. The shape data storage unit 6 stores shape data of a processing object expressed by a distance field model. The shape data storage unit 6 stores at least two shape data.

  Here, the distance field model will be described. The distance field (or distance field) is a kind of scalar field formed by the space where the target shape is placed, and the field value is given by the distance from any point of interest to the shape surface. Point to. Normally, the Euclidean shortest distance from the point of interest to the shape surface is used as the distance value, and the sign of the distance value is changed so that it is possible to identify whether the point of interest is inside or outside the shape.

  The distance field can be mathematically regarded as a monovalent function d = f (P) in a broad sense from the spatial coordinate point P to the signed distance d, and is called a distance function. In addition, the gradient (gradient) of the distance function grad. A vector obtained by taking f (P) is called a distance gradient vector, and coincides with a vector perpendicular to an isosurface passing through the point P (an isoline in the case of a two-dimensional space), that is, a normal vector. In particular, if the point P is located on or near the shape surface, the distance gradient vector can be a normal vector of the shape surface or an approximation thereof.

  In this embodiment, as a distance field model handled by the cutting simulation unit 3, “Adaptively Sampled Distance Fields: A General Representation of Shape for Computer Graphics” by Frisken et al., Proc. SIGGRAPH 2000, pp. The adaptive sample distance field described in 249-254,2000 is employed.

  The adaptive sample distance field samples the distance field on grid points managed by hierarchical tree management by quad division or oct division according to the dimension of the space, and the value of the distance field at any spatial coordinate point including the sampling point , Referred to as a distance value or a signed distance value) can be restored and calculated by a method such as interpolation.

  In the most typical implementation method of the adaptive sample distance field, a square area or a cubic area by quad division or oct division is set as a cell, and a distance value sampled at a corner point of the cell is associated with the cell to represent data. The distance value at an arbitrary coordinate point inside the cell boundary or inside is approximately restored and calculated by linearly interpolating the distance value sampled at the corner point. In addition, the distance gradient vector is approximated by reconstructing the linear interpolation equation for the distance value using the partial differential coefficient for each coordinate. The distance value and distance gradient vector thus restored include approximation errors, but in the adaptive sample distance field, data is used so that the approximation error falls within a predetermined tolerance by recursive quad division or oct division. Adaptively rebuild the structure.

  Next, a schematic operation of each part constituting the machining simulation apparatus 1 will be described. The tool movement data 9 prepared outside the machining simulation apparatus 1 describes tool position data and tool movement type data generated from a machining program based on designated simulation conditions. Here, the simulation conditions are the machining condition parameters described in the machining program such as the tool feed rate, the machining condition parameters that are directly specified to the machine tool, such as the acceleration / deceleration constant, and the machining program to the machine tool. This refers to the difference in the processing level inside the numerical control device in the process of generating the command to. The simulation execution control unit 2 instructs the cutting simulation unit 3 to perform a cutting simulation based on the tool position data and the tool movement type data described in the tool movement data 9.

  The cutting simulation unit 3 reads out the current shape data of the workpiece expressed by the adaptive sample distance field from the shape data storage unit 6. The cutting simulation unit 3 updates the read shape data based on the tool position data and the tool movement type data instructed from the simulation execution control unit 2, and writes the updated shape data back to the shape data storage unit 6. The cutting simulation unit 3 repeats such processing.

  This cutting simulation is executed at least twice with different simulation conditions. The simulation results obtained by changing the simulation conditions are stored in different areas of the shape data storage unit 6, respectively.

  Next, the simulation execution control unit 2 instructs the comparison target selection unit 4 to specify the reference standard shape and select the comparison target shape. The comparison target selection unit 4 designates one of a plurality of simulation results stored in the shape data storage unit 6 as a reference standard shape (data) 7 and one of simulation results based on simulation conditions different from the reference standard shape. Is selected as the comparison target shape (data) 8.

  In addition, the simulation execution control unit 2 instructs the shape drawing processing unit 5 to perform drawing processing on the simulation result selected as the comparison target shape. The shape drawing processing unit 5 reads the reference standard shape 7 and the comparison target shape 8 from the shape data storage unit 6, and executes a rendering process on the comparison target shape 7 by, for example, the raycast method. The display device 10 graphically displays the simulation result shape as the comparison target shape 8 based on the data that has undergone the rendering processing in the shape drawing processing unit 5.

  Next, details of the rendering process in the shape drawing processing unit 5 will be described. Assuming a projection surface on which pixels are arranged, the shape drawing processing unit 5 assumes that a direction perpendicular to the projection surface is a projection direction, and irradiates a virtual ray along the projection direction from each pixel on the projection surface. The intersection position between the light beam and the surface of the comparison target shape 8 is calculated. Next, the shape drawing processing unit 5 calculates a signed distance value for the reference standard shape 7 at the intersection position. The calculated signed distance value represents the distance from the comparison target shape 8 to the reference standard shape 7 at the intersection position, as will be described later. Further, the shape drawing processing unit 5 calculates the distance gradient vector at the intersection position for each of the reference standard shape 7 and the comparison target shape 8, and calculates the angle formed by both vectors.

  FIG. 2 is a diagram for explaining the process of calculating the intersection position, the calculation of the signed distance value, and the calculation of the distance gradient vector in the rendering process. In the figure, (a) schematically represents a partial cross section including a target portion in the comparison target shape 8. The projection plane 21 is assumed to be a plane perpendicular to the cross section. An intersection position 25 between the light beam 23 irradiated along a projection direction from a certain pixel 22 arranged on the projection surface 21 and the surface 24 of the comparison target shape 8 is a distance function of the comparison target shape 8 and is a distance value. Is calculated by simultaneously solving an equation with a zero and a linear equation representing the direction of the light beam 23.

  (B) schematically represents a partial cross-section including a point of interest similar to (a) in the reference standard shape 7. A signed distance value 27 between the intersection position 25 and the surface 26 of the reference standard shape 7 is calculated by evaluating the distance function of the reference standard shape 7 at the intersection position 25. Since the intersection position 25 is located on the surface 24 of the comparison target shape 8, the calculated signed distance value 27 represents the difference between the comparison target shape 8 and the reference standard shape 7 at the point of interest.

  (C) represents the distance gradient vector 28 of the comparison target shape 8 at the intersection position 25 and the distance gradient vector 29 of the reference standard shape 7 at the intersection position 25. The distance gradient vectors 28 and 29 are calculated as secondary geometric features that can be derived from the distance field. The distance gradient vectors 28 and 29 are calculated by evaluating the gradients for the distance functions of the comparison target shape 8 and the reference standard shape 7 at the intersection position 25. The distance gradient vector 28 of the comparison target shape 8 is the normal vector itself of the surface 24 of the comparison target shape 8. The distance gradient vector 29 of the reference standard shape 7 corresponds to an approximation of the normal vector of the surface 26 of the reference standard shape 7. Further, the shape drawing processing unit 5 calculates an angle formed by the distance gradient vector 28 of the comparison target shape 8 and the distance gradient vector 29 of the reference standard shape 7 as a difference in the secondary geometric feature amount.

  After calculating the angle formed by the signed distance value 27 and the distance gradient vectors 28 and 29, the shape drawing processing unit 5 determines the corresponding pixel 22 based on the angle formed by the signed distance value 27 and the distance gradient vectors 28 and 29. Is determined, and an image to be displayed on the display device 10 is created. The projection direction set during the rendering process corresponds to the direction in which the processed shape is viewed in the displayed image.

  For example, when a color image is displayed on the display device 10, a component when the signed distance value 27 is positive, a component when the signed distance value 27 is negative, a distance gradient vector 28, and the like for three primary colors of RGB The luminance value of each pixel is determined by assigning an angle component between 29 and the like. The method of creating an image is not limited to this, for example, setting the upper and lower limits for distance values and angles, narrowing down the object of interest by clamping, and grasping the entire shape by reflecting the light and darkness taking into account lighting conditions You may employ | adopt the method of making it easy.

  In general, the shape in the case where a processing defect such as a processing flaw occurs is compared with the shape in the case where the processing defect does not occur. Various aspects such as cases. According to the present embodiment, it is possible to visualize the geometric characteristics of the machining failure location by using the distance between the reference standard shape 7 and the comparison target shape 8 and the difference between the normal vectors. As a result, it becomes possible to discriminate machining defects and easily estimate the cause of machining defects. By applying the adaptive sample distance field model as the distance field model handled by the cutting simulation unit 3, the distance between the reference standard shape 7 and the comparison target shape 8 at the machining defect location and the calculation of the secondary geometric feature amount can be performed. It can be done relatively easily.

  The rendering process in the shape drawing processing unit 5 is not limited to the case where the angle between the distance gradient vectors 28 and 29 is used to determine the luminance value, and other secondary geometric features that can be derived from the distance field are used. Also good. For example, the curvature of the distance field may be used as the secondary geometric feature quantity, and the difference between the curvature of the reference standard shape 7 and the curvature of the comparison target shape 8 may be calculated. The curvature of the distance field can be derived, for example, from the second order partial differential coefficient of the distance function. When applying the adaptive sample distance field, an approximate calculation is possible with the second-order partial differential coefficient for each coordinate of the linear interpolation formula for the distance value.

Embodiment 2. FIG.
The processing simulation apparatus according to the second embodiment of the present invention presents a new projection direction on the condition that the angle formed by the distance gradient vector of the comparison target shape or the reference standard shape and the light ray is included in a predetermined range. It is characterized by. Since the schematic configuration of the machining simulation apparatus is the same as that of the first embodiment, the configuration shown in FIG. 1 is used for the description, and the description of parts other than the features of the present embodiment is omitted.

  In the rendering process, the shape drawing processing unit 5 calculates an angle formed by the light beam 23 and the distance gradient vector 28 of the comparison target shape 8 or the distance gradient vector 29 of the reference standard shape 7 at the intersection position 25. When the calculated angle is included in a predetermined range including 90 degrees, the shape drawing processing unit 5 determines a new projection direction for drawing and presents it to the simulation execution control unit 2.

  The simulation execution control unit 2 notifies the operator of a plurality of projection directions presented from the shape drawing processing unit 5. The shape drawing processing unit 5 executes drawing processing based on the new projection direction selected by the operator.

  FIG. 3 is a diagram illustrating a process of determining a new projection direction in the shape drawing processing unit 5. The shape drawing processing unit 5, along with the distance gradient vectors 28 and 29 of the comparison target shape 8 and the reference standard shape 7, the distance gradient vector 28 of the comparison target shape 8 or the distance gradient vector 29 of the reference standard shape 7 and the direction vector of the light beam 23. Calculate the angle between the two. The illustrated distance gradient vectors 31 and 35 are the distance gradient vector 28 of the comparison target shape 8 or the distance gradient vector 29 of the reference standard shape 7.

  (A) in the drawing represents a case where the angle 33 formed by the distance gradient vector 31 and the light beam 32 is close to 90 degrees. In this case, the shape drawing processing unit 5 determines a direction parallel to the distance gradient vector 31 as a new projection direction of drawing and presents it to the simulation execution control unit 2. In addition to the direction parallel to the distance gradient vector 31, as shown in (b), the direction of the distance gradient vector 35 in a direction different from the distance gradient vector 31 for the light ray 34 from another pixel is also a new projection direction. Can be determined as In this case, a plurality of projection directions are presented to the simulation execution control unit 2 for the shape including the point of interest.

  The simulation execution control unit 2 notifies the operator of a plurality of projection directions presented by the shape drawing processing unit 5 in the form of a menu list or the like, and controls the shape drawing processing unit 5 based on the projection direction selected by the operator. . The shape drawing processing unit 5 re-executes the drawing process according to the projection direction according to the control of the simulation execution control unit 2.

  When the angle formed by the distance gradient vector and the direction vector of the light ray is close to 90 degrees, a state in which the machining shape is viewed from the side is drawn. Such a location may be difficult to discriminate even when a machining defect has occurred, and the machining defect may be overlooked. According to the present embodiment, a display of a state in which the machining shape is viewed from a different angle by presenting a new projection direction that makes it easy to discriminate the location where it may be difficult to discriminate machining defects. Is possible.

  By making it possible to select a projection direction suitable for display for each processing shape, it is possible to accurately check a processing defect location for the entire processing target. The predetermined range of the angle formed by the distance gradient vector and the ray direction vector, which is a condition for presenting a new projection direction in the present embodiment, is an angle range including at least 90 degrees, and the shape is discriminated. It can be set as appropriate according to the degree of difficulty.

  The new projection direction presented by the shape drawing processing unit 5 is set according to the angle formed by the distance gradient vector at the intersection position where the ray from the pixel on the projection plane and the surface of the shape first intersect. Not limited to. The new projection direction is the position of the next intersection where the ray passes through the surface of the shape, for example, the portion hidden on the outer surface when the light ray penetrates from the inside to the outside of the shape or behind a certain part It is good also as setting according to the angle which a light ray and a distance gradient vector make in the position of the intersection on the surface. Thereby, it is possible to present a desirable projection direction for a portion on the back surface or the hidden surface when viewed in the current projection direction.

  The shape drawing processing unit 5 is not limited to the case where the direction of the distance gradient vector is set as a new projection direction. For example, the direction vector may be grouped into a plurality of sections based on latitude, longitude, etc., and a representative direction for each group may be set as the projection direction. In this case, the number of new projection directions notified to the operator is reduced, and the processing for notifying the projection direction and the operation for selecting the projection direction can be simplified.

Embodiment 3 FIG.
FIG. 4 is a block diagram showing a configuration of the numerical controller 41 according to Embodiment 3 of the present invention. The numerical control device 41 numerically controls the machine tool 47 in accordance with the NC machining program 46. The numerical control device 41 includes the numerical control unit 42 and the machining simulation device 1 according to the first or second embodiment.

  The numerical control unit 42 includes a machining program analysis unit 43, a tool path interpolation processing unit 44, and a motion control unit 45. The machining program analysis unit 43 reads the NC machining program 46 and analyzes a tool movement command described in the program. Further, the machining program analysis unit 43 generates tool movement data in command units subjected to corrections such as tool length correction and tool radius correction.

  The tool path interpolation processing unit 44 interpolates the tool movement path in units of control cycles according to the command unit tool movement data, the tool feed speed, the acceleration / deceleration parameters, and the like, and generates tool movement data. The motion control unit 45 controls the machine tool 47 via a servo unit or the like. In the process of control by the motion control unit 45, the relative position of the tool with respect to the workpiece is acquired by indirect or direct feedback. The numerical controller 41 generates or acquires tool movement data or data that can be reduced to the tool movement data for different processing stages (processing levels) in the numerical controller 42.

  Examples of processing steps in the numerical control unit 42 include an analysis step by the machining program analysis unit 43, an interpolation processing step by the tool path interpolation processing unit 44, and a control processing step by the motion control unit 45. In the analysis by the machining program analysis unit 43, tool movement data in command units is generated. In the interpolation processing by the tool path interpolation processing unit 44, tool movement data in units of control cycles is generated. In the control process by the motion control unit 45, feedback data from the servo amplifier and sensing data of the machine tool 47 are acquired as data that can be reduced to the tool movement data.

  Next, two operation examples will be described with respect to the machining failure simulation in the numerical controller 41 according to the present embodiment. In the first operation example, the machining simulation device 1 performs machining simulation on the same NC machining program 46 under different machining conditions. For example, the tool movement data generated by the tool path interpolation processing unit 44 may be different depending on the machining conditions such as the tool feed speed and acceleration / deceleration parameters, thereby affecting the machining result shape.

  The numerical controller 41 uses the tool movement data generated under different machining conditions to perform a cutting simulation by the machining simulation device 1 and to compare and visualize the simulation result shapes. As a result, it is possible to obtain a clue for estimating what processing conditions have caused the processing failure.

  In the second operation example, the machining simulation device 1 performs machining simulation on the same NC machining program 46 based on tool movement data generated or acquired at different processing levels inside the numerical control unit 42. Originally, it is ideal that the machine tool 47 operates in accordance with a command from the numerical control device 41, but a deviation from the command may occur in an actual operation due to a response delay of the machine or the like. If the operation of the machine tool 47 is different from the command, the machining result shape may be affected.

  The numerical control device 41 uses the tool movement data generated or acquired at different processing levels inside the numerical control unit 42 to perform a cutting simulation by the processing simulation device 1 and to compare and visualize the simulation result shapes. This makes it possible to obtain a clue for estimating which stage of control processing or machine operation has caused a machining defect.

  According to the present embodiment, based on the tool movement data generated or acquired by the numerical control device 41, the machining simulation device 1 performs the cutting simulation and compares the resulting shapes to isolate the cause of the machining failure. Can be verified. As a result, it is possible to greatly reduce repetitive work that eliminates processing defects by trial and error trial cutting, shortening the processing lead time and suppressing wasteful use of materials.

  As described above, the machining simulation device and the numerical control device according to the present invention are suitable for cutting simulation.

DESCRIPTION OF SYMBOLS 1 Processing simulation apparatus 2 Simulation execution control part 3 Cutting simulation part 4 Comparison object selection part 5 Shape drawing process part 6 Shape data storage part 7 Reference reference | standard shape (data)
8 Shape to be compared (data)
DESCRIPTION OF SYMBOLS 9 Tool movement data 10 Display apparatus 21 Projection surface 22 Pixel 23, 32, 34 Light beam 25 Intersection position 27 Signed distance value 28, 29, 31, 35 Distance gradient vector 41 Numerical control apparatus 47 Machine tool

Claims (9)

A cutting simulation unit for simulating the shape of the workpiece expressed by the distance field model by updating the distance field model based on the tool movement data generated under the predetermined simulation conditions of the cutting process;
A reference object shape is designated from a simulation result in the cutting simulation part, and a comparison object selecting part for selecting a comparison object shape from a simulation result based on the tool movement data generated under the simulation conditions different from the reference standard shape; ,
A shape drawing processing unit that executes a rendering process for graphically displaying the simulation result selected as the comparison target shape by the comparison target selection unit;
A simulation execution control unit for controlling the cutting simulation unit, the comparison target selection unit, and the shape drawing processing unit,
In the rendering process, the shape rendering processing unit assumes the projection plane in which pixels are arranged and the light beam along a projection direction that is a direction perpendicular to the projection plane from each pixel on the projection plane. Calculate the intersection point of the target shape and the ray,
A processing simulation for determining a luminance value of the pixel based on a signed distance value with respect to the reference standard shape and a difference between secondary geometric feature quantities derivable from a distance field at the intersection position apparatus.   The machining simulation apparatus according to claim 1, wherein the distance field model is an adaptive sample distance field.   The machining simulation apparatus according to claim 1, wherein the secondary geometric feature amount is a distance gradient vector of the distance field.   The difference between the secondary geometric feature amounts is an angle formed by the distance gradient vector for the comparison target shape and the distance gradient vector for the reference standard shape. Machining simulation equipment.   The machining simulation apparatus according to claim 1, wherein the secondary geometric feature amount is a curvature of the distance field.   The shape drawing processing unit sets a new projection direction for the graphic display on the condition that an angle formed by a distance gradient vector and the light ray with respect to the comparison target shape or the reference standard shape is included in a predetermined range. The machining simulation apparatus according to claim 1, wherein the machining simulation apparatus is presented.   The simulation execution control unit controls the shape drawing processing unit based on a projection direction selected from the new projection directions presented by the shape drawing processing unit. Processing simulation device. A numerical control unit for numerically controlling the machine tool;
A machining simulation device according to any one of claims 1 to 7,
The numerical control device, wherein the machining simulation device performs a simulation based on tool movement data generated for different machining conditions in the machine tool. A numerical control unit for numerically controlling the machine tool;
A machining simulation device according to any one of claims 1 to 7,
The numerical simulation device, wherein the machining simulation device executes a simulation based on tool movement data generated or acquired for different processing stages in the numerical control unit.

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