JP7012229B2 - Numerical control programming device, numerical control work system and numerical control work program - Google Patents

Description

The present invention relates to a numerical control programming device, a numerical control machine tool, and a numerical control machine tool, and in particular, controls a numerical control machine tool that performs machining along a target curve by moving a work piece and a tool relative to each other. The present invention relates to a numerical control program creation device, a numerical control work system, and a numerical control work program for creating a program for instructing a numerical control device.

The main function of a numerically controlled machine tool is high-speed, high-precision machining in which a workpiece (geographical object, workpiece) is machined within the desired accuracy in the shortest possible time. Further, an important function of the numerical control program creation device (Computer Aided Manufacturing: CAM) is to create a program (numerical control program) for performing high-speed and high-precision machining and instruct the numerical control device.

When the machined shape is a curve, the numerical control program creating device creates a program for curve processing. When performing curve processing, it is usual to create a program with minute line segments that are approximated so that the maximum distance from the target curve is the set chord error (allowable chord error).

The file converter device disclosed in Patent Document 1 is known as a prior art for creating the above-mentioned minute line segment program. In the file converter device disclosed in Patent Document 1, the target curve is a NURBS (Non Uniform Rational B-Spline) curve, and the distance is less than the chord error (ε) set for the NURBS curve and as close to ε as possible. A minute line segment is created, and a linear interpolation program is created by G01 (linear interpolation command).

For high-precision machining, it is desirable to reduce the string error and create a program for smaller minute line segments. However, it takes a certain amount of time (hereinafter, "block processing time") for the numerical control device to read and analyze one block of the program. Therefore, if an excessively small minute line segment program that requires reading and analyzing one block faster than the block processing time is commanded, the machining speed will not be as high as the command speed, or the machining speed will be reduced. Problems such as wobbling and roughening of the machined surface occur. Therefore, the string error to be set cannot be made excessively small. To solve this problem, it is possible to set a large string error with a certain margin in mind, but in this case, the intended processing accuracy may not be achieved.

As a prior art related to the block processing time, the feed rate clamping method disclosed in Patent Document 2 is known. In the feed rate clamping method disclosed in Patent Document 2, the command speed is clamped based on the block processing time. However, the feed rate clamping method disclosed in Patent Document 2 clamps to a desired original command speed, which is not desirable from the viewpoint of high-speed machining.

International Publication No. WO99 / 61962 Japanese Unexamined Patent Publication No. 6-95727

The present invention has been made in view of the above background, and it is possible to create a numerical control program that realizes higher speed and higher precision machining in a numerical control machine tool. It is an object of the present invention to provide a programming device, a numerical control work system, and a numerical control work program.

In order to achieve the above-mentioned object, the numerical control program creating device according to claim 1 provides a numerical control program indicating a command to a numerical control device for controlling a numerical control machine tool that performs machining along a target curve. It is a numerical control program creation device to be created, and has a block processing time indicating the processing time of the numerical control device, a command speed for designating a processing speed of the numerical control device, a radius of curvature in the target curve, and the target curve. Based on the storage means for storing the relationship between the plurality of parameters of the string error for line segment approximation and the condition of the string error for the numerical control device to control the numerical control machine, the plurality of. It includes a calculation means for calculating a target chord error using the relationship between parameters, and a program creation means for creating an approximate line segment with respect to the target curve based on the target chord error.

Further, in the invention of claim 2, in the invention of claim 1, the relationship between the plurality of parameters is the relationship between the block processing time, the command speed, the radius of curvature, and the string error. It is the chord error curved surface shown.

The invention according to claim 3 is the invention according to claim 2, wherein the string error condition is a condition for designating a point on the string error curved surface.

The invention according to claim 4 is the invention according to claim 2, wherein the string error condition specifies a point in the vicinity of the string error curved surface.

Further, in the invention according to claim 5, in the invention according to claim 4, the calculation means corrects any one of the block processing time, the command speed, the radius of curvature, and the string error by more than 1. The target string error is calculated by multiplying by a coefficient.

Further, in the invention of claim 6, in the invention of claim 1, the relationship between the plurality of parameters is a function of the chord error with the command speed and the radius of curvature as variables. The calculation means calculates the maximum value of the chord error with respect to the combination of the command speed and the radius of curvature in the target curve by using the function of the chord error, and uses the maximum value of the chord error to calculate the target chord error. It is to calculate.

Further, in the invention of claim 7, in the invention of claim 1, the relationship between the plurality of parameters is a function of the chord error with the command speed and the radius of curvature as variables. The calculation means calculates the maximum value of the command speed and the minimum value of the radius of curvature in the target curve, and uses the maximum value of the command speed and the minimum value of the radius of curvature to use the target based on the function of the chord error. It calculates the string error.

Further, in the invention of claim 8, in the invention of claim 7, the chord error function is a function of the normal acceleration represented by the command speed and the radius of curvature, and the calculation means is , The maximum value of the normal acceleration in the target curve is calculated, and the target chord error is calculated based on the function of the normal acceleration using the maximum value of the normal acceleration.

Further, the invention according to claim 9 is the invention according to any one of claims 1 to 8, wherein the calculation means sets a minimum value for the target string error and calculates the target string. When the error is less than the minimum value, the minimum value is calculated as the target chord error.

In order to achieve the above-mentioned object, the numerical control machine tool system according to claim 10 is the numerical control program creation device according to any one of claims 1 to 9, and machining along a target curve. It includes a numerically controlled machine tool that controls the numerically controlled machine tool and a numerically controlled machine tool that controls the numerically controlled machine tool based on a program created by the numerically controlled program creating device.

In order to achieve the above-mentioned object, the numerical control work program according to claim 11 creates a numerical control program indicating a command to a numerical control device that controls a numerical control machine that performs machining along a target curve. A numerical control work program for operating a numerical control program creation device, wherein a computer has a block processing time indicating the processing time of the numerical control device, a command speed for designating a processing speed of the numerical control device, and the target. A storage means for storing the relationship between the radius of curvature in a curve and a plurality of parameters of chord error for linear approximation of the target curve, and the numerical control device for controlling the numerical control machine. A calculation means for calculating the target string error using the relationship between the plurality of parameters based on the condition of the string error, and a program creation means for creating an approximate line segment with respect to the target curve based on the target string error. It is intended to function as.

According to the present invention, in a numerical control machine tool, a numerical control program creation device, a numerical control work system, and a numerical value capable of creating a numerical control program that realizes higher speed and higher precision machining. It becomes possible to provide a controlled work program.

It is a block diagram which shows an example of the structure of the numerical control work system which includes the numerical control program creating apparatus which concerns on 1st Embodiment, 2nd Embodiment, and 3rd Embodiment. It is a figure explaining the program which obtains a block processing time (Tb). It is a graph which shows an example of the relationship between the command speed F and the actual speed Vm. It is a figure which shows the chord error curved surface which shows the relationship between the command speed F, the radius of curvature r, and the chord error Ce. It is a figure explaining the example which obtains the radius of curvature in the target curve P (s). It is a figure explaining the relationship of the radius of curvature r, the line segment length Lb of a chord, the chord error Ce, and the angle θ. It is a flowchart which shows the process flow of the numerical control work program with respect to the target curve P (s). It is a figure explaining the creation of the numerical control program with respect to the target curve P (s). It is a graph which shows the result of the Example of this invention. It is a figure which shows the error and the velocity waveform in the result of the Example of this invention. It is a figure explaining the relationship between the direction change angle and deceleration in the corner of a command line segment. It is a block diagram which shows an example of the structure of the numerical control program creation apparatus which concerns on 4th Embodiment and 5th Embodiment. It is a figure explaining the command speed and the radius of curvature in 4th Embodiment.

Hereinafter, embodiments for carrying out the present invention will be described in detail with reference to the drawings. The following embodiments do not limit the invention according to the claims. Also, not all combinations of features described in the embodiments are essential to the means of solving the invention.

[First Embodiment]
A numerical control program creating device, a numerical control work system, and a numerical control work program according to the present embodiment will be described with reference to FIGS. 1 to 11.

As shown in FIG. 1, the numerical control program creating device 10 according to the present embodiment includes a string error curved surface creating means 12, a program string error creating means 14, and a program creating means 16. The numerical control program creation device 10 is connected to the numerical control machine tool 20 via the numerical control device, and the numerical control program creation device 10, the numerical control device, and the numerical control machine tool 20 are used in the present embodiment. The numerical control work system 1 is configured. For simplification, the numerical control device is included in the numerical control machine tool 20 in FIG. 1 and is integrally configured.

As shown in FIG. 1, the numerical control program creating device 10 inputs a command speed F, a target curve P (s), and a block processing time Tb, and outputs a numerical control program. Then, the output numerical control program is sent to the numerical control device (numerical control machine tool 20) as a command. That is, the numerical control program creation device 10 according to the present embodiment is configured as a so-called CAM.

The command speed F is the feed speed (relative speed) of the tool with respect to the workpiece. When the target curve P (s) is given, the command speed F is set for the numerical control program creation device 10 by a conventionally known method. Alternatively, the operator or the like of the numerical control work system 1 may input the command speed F. Alternatively, the numerical control program creation device 10 (CAM) has a function of outputting an appropriate command speed F (feed speed) when various conditions such as the material and hardness of the workpiece, the diameter of the tool and the number of blades are input. I have something to have. In that case, the command speed F in FIG. 1 is created in the numerical control program creation device 10 (CAM). The command speed F may be acquired by such a function, or an appropriate command speed F may be input by a programmer, an operator, or the like. As described above, the command speed F for the target curve P (s) is commanded.

The target curve P (s) is given (determined) corresponding to the work content when the work content for the work is determined. Alternatively, the target curve P (s) is created from the target machined shape in the numerical control program creating device 10 (CAM). Here, s is a distance on the curve, and the function P (s) shows a processing curve with respect to the distance s. Further, the target curve P (s) is a three-dimensional vector, and is expressed as P (s) = (Px (s), Py (s), Pz (s)). The number of hours of the target curve P (s) is not limited to three dimensions, and may be four or more high dimensions. Further, the variable expressing the target curve P as a function is not limited to the distance s, and may be a function by another variable such as time t.

The block processing time Tb is the time for the numerical control device to read out and analyze one block. In this embodiment, as will be described later, this block processing time Tb is measured in advance.

The chord error curved surface creating means 12 creates a chord error curved surface Sc, which will be described later, using the command speed F, the block processing time Tb, and the radius of curvature r obtained from the target curve P (s). The created string error curved surface Sc may be stored in a storage means such as a ROM (not shown) included in the numerical control program creating device 10. The program string error creating means 14 calculates the program string error Cep (corresponding to the “target string error” according to the present invention) using the command speed F, the radius of curvature r, and the string error curved surface Sc. The program creating means 16 creates a numerical control program using the program string error Cep and the target curve P (s). The numerical control program in the program creating means 16 may be created by a conventionally known method. In the following description, the general string error is represented by the symbol Ce, and the program string error is represented by the symbol Ce to distinguish them.

Next, a method of acquiring the block processing time Tb will be described. As an example of the method of acquiring the block processing time Tb, for example, a method using a timer interrupt is known (for example, Patent Document 2). However, in the method using timer interrupt, it is necessary to change the software of the numerical control device. Therefore, in the present embodiment, a simpler method is used, in which the minute linear movement command is repeated, the time between them is measured, and the block processing time Tb is obtained from the actual speed.

FIG. 2 shows an example of a program for calculating the block processing time Tb (hereinafter, “block processing time calculation program”). As shown in FIG. 2, the block processing time calculation program includes a main program (MAIN-PROG) and a subprogram SUB-PROG (999). In the example of FIG. 2, the main program calls the subprogram 50 times.

The command by the subprogram is a command to move 10 mm by executing a block having a movement amount of 0.1 mm 100 times. Therefore, the main program is a program that commands the movement of 500 mm at the command speed "F **" (arbitrary value) (10 mm x 50 times = 500 mm). The main program measures the time Tm (min: minutes) during that time by the macro variable "# 3001". From the above, the actual speed is obtained at 500 / Tm (mm / min).

"G53" in the main program is a command to temporarily stop reading the program in order to read the macro variable "# 3001" after the movement is completed. If the command speed F is sufficiently small, the main program is executed at a speed almost equal to the command speed F. However, when the command speed F becomes large, the block processing time Tb cannot be met in time, and the actual speed reaches a plateau.
The block processing time Tb (msec: millisecond) can be obtained from the limit.

FIG. 3 shows an example of the relationship between the command speed F and the actual speed Vm obtained as described above. That is, FIG. 3 is a graph showing changes in the actual speed Vm with respect to some command speeds F. From FIG. 3, it can be seen that the actual speed Vm is limited to 1500 mm / min. When the block processing time Tb is calculated by the following (Equation 1) using the actual speed of this limit of 1500 mm / min, Tb = 4 msec.

In this example, the movement block of 0.1 mm was commanded 5000 times and the time between them was measured with a macro variable to obtain the actual speed Vm, but the minute movement command is not limited to 0.1 mm and an appropriate value is used. You may choose. Further, when counting the machining time, the time may be measured by, for example, a stopwatch without using the macro variable. Further, the block processing time Tb will be described by way of example in the case of Tb = 4 msec in the present embodiment, but the block processing time Tb differs depending on the numerical control device, and strictly speaking, the command content (number of axes, linear command). It depends on whether it is an arc command, whether there is tool diameter correction, etc.). However, when a minute linear command with a fixed number of axes is issued in a predetermined numerical control device, the block processing time Tb is considered to be constant. Therefore, in the present embodiment, the block processing time Tb is treated as a constant.

Next, the string error curved surface creating means 12 will be described. The chord error curved surface creating means 12 is a portion for creating a chord error curved surface Sc showing the relationship between the radius of curvature r, the command speed F, and the block processing time Tb and the chord error Ce. As described above, in a certain numerical control device, the block processing time Tb for the minute line segment command may be considered to be constant. Therefore, the chord error curved surface Sc according to the present embodiment shows the relationship between the radius of curvature r, the command speed F, and the chord error Ce when the block processing time Tb is fixed to a certain value. The relationship between the radius of curvature r, the command speed F, and the chord error Ce when the block processing time Tb is fixed is represented by a predetermined curved surface as described later.

Hereinafter, a method of creating the string error curved surface Sc will be described. First, the string error will be described with reference to FIG. FIG. 6 shows an approximation method when the target curve P is approximated by a line segment. In FIG. 6, when the angle corresponding to the chord when the chord with the line segment length Lb is created with respect to the curve of the radius of curvature r approximated by the arc is θ, the chord error Ce (mm) is as shown in FIG. Defined. At that time, the command speed F (mm / min) is limited by the block processing time Tb (msec), which means that the actual speed does not increase even if the command is raised further (Equation 2).

（式３）は不等式であるが、これを（式４）のように等式としたものは曲面を表し、この曲面を弦誤差曲面Ｓｃとよぶ。

つまり、本実施の形態に係る弦誤差曲面Ｓｃは、あるブロック処理時間Ｔｂが与えられた場合の、曲率半径ｒ、指令速度Ｆ、弦誤差Ｃｅの複数のパラメータの間の関係を示している。図示しない記憶手段はこの複数のパラメータの間の関係を記憶する。記憶手段がこのような複数のパラメータの間の関係を記憶することについては、後述の実施の形態でも同様である。 Eliminating θ from (Equation 2) gives (Equation 3) as shown below.

(Equation 3) is an inequality, but an equation like (Equation 4) represents a curved surface, and this curved surface is called a string error curved surface Sc.

That is, the chord error curved surface Sc according to the present embodiment shows the relationship between a plurality of parameters of the radius of curvature r, the command speed F, and the chord error Ce when a certain block processing time Tb is given. A storage means (not shown) stores the relationship between these plurality of parameters. The same applies to the embodiments described later in that the storage means stores the relationship between such a plurality of parameters.

FIG. 4 shows an example of the string error curved surface Sc created by the string error curved surface creating means 12 based on (Equation 4). In FIG. 4, the block processing time Tb is Tb = 4 msec.
Further, in FIG. 4, the X-axis is the command speed F (mm / min), the Y-axis is the radius of curvature r (mm), and the Z-axis is the chord error Ce (mm). The inequality represented by (Equation 3) indicates that the string error Ce needs to exist in the region above the Z-axis direction of the string error curved surface Sc.

Next, a method of obtaining a local radius of curvature r from the target curve P (s) will be described with reference to FIG. Now, it is assumed that the target curve P (s) with the distance s as a variable is given as shown in FIG. The target curve P (s) is a three-dimensional vector P (s) = (Px (s), Py (s), Pz (s)) as described above. In this case, the radius of curvature r is between a certain position P (s0) on the curve and a position P (s1) (s1 = s0 + Δs) separated by a minute curve distance Δs (hereinafter, “small distance Δs”). It is obtained from the radius of curvature. Here, Δs is a minute distance such that the radius of curvature r can be obtained, and may be variable according to the radius of curvature or the like. Specifically, P (sm) is P (s0) and P. The midpoint with (s1), that is, P (sm) = P ((s0 + s1) / 2). At this time, the arc approximation is performed using the three points P (s0), P (sm), and P (s1). The radius of curvature r is obtained by performing the above procedure, and the radius of curvature r is obtained from the above procedure. However, the method for obtaining the radius of curvature r is not limited to the above, and any known method may be used.

Next, the operation of the program string error creating means 14 will be described. The program string error Cep according to the present embodiment means a string error used when creating a program in the numerical control program creating device 10. That is, the program string error creating means 14 is as small as possible or sufficiently small to satisfy (Equation 3) with respect to the radius of curvature r calculated by the above method, the preset command speed F, and the preset block processing time Tb. Calculate the chord error Ce. The calculated string error Ce is used as the program string error Ce. In the present embodiment, the means for calculating the string error Ce and using it as the program string error Ce is the calculation means for calculating the target string error.

Next, the program creating means 16 creates a program (command) for controlling the numerical control device using the program string error Cep obtained above. Since a specific method for creating a program is created by a conventionally known method, detailed description thereof will be omitted (see, for example, Patent Document 1).

Next, with reference to FIGS. 7 and 8, the numerical control program creation process executed by the string error curved surface creating means 12, the program string error creating means 14, and the program creating means 16 will be described. 7 and 8 are flowcharts showing the flow of a numerical control program creation program (hereinafter, “numerical control work program”) according to the present embodiment. The numerical control work program is stored in a storage means such as a ROM (not shown) of the numerical control program creating device 10, read by a CPU, expanded to a storage means such as a RAM, and executed. In FIGS. 7 and 8, a case where a program from the position P (ss) to P (se) is created in the target curve P (s) shown in FIG. 8 will be illustrated and described.

In step S101, first, as a minute distance Δs, a substantially fan shape is formed so that a local radius of curvature r can be obtained on P (s) (that is, a part of the target curve P (s) is an arc. ) Set the length. That is, the minute distance Δs is set sufficiently small with respect to the length between the distances ss and se. Set the final flag to 0. Let P (ss) be the first program command point. Let s0 = ss and s1 = s0 + Δs.

In the next step S102, the string error curved surface Sc is obtained using the equation (4) expressing the relationship between the block processing time Tb, the radius of curvature r, the command speed F, and the string error Ce. The process in step 102 is the process in the string error curved surface creating means 12.

In the next S103, the radius of curvature r between P (s0) and P (s1) is obtained, for example, by the method described above. Next, a string error Ce that is as small as possible or sufficiently small that satisfies (Equation 3) with respect to the radius of curvature r and the command speed F is obtained and used as the program string error Ce. The process in step 103 is the process in the program string error creating means 14. Here, the string error Ce that is as small as possible is, for example, a Ce that satisfies the equation (4), and in the present embodiment, the string error Ce that satisfies this equation (4) is referred to as a program string error Ce. This is the condition of the string error in this embodiment. On the other hand, the sufficiently small string error Ce is a string error Ce located in the vicinity of the + Z direction with respect to the equation (4), and a specific example will be described later.

In the next step S104, as shown in FIG. 8, the program command points P (s01), P (s02), ... , P (s0n) is obtained and added to the program to be created. The process in step S104 is the process in the program creating means 16. Since the processing in the program creating means 16 includes the creation of a program according to the prior art, the processing in step S104 is a part of the processing in the program creating means 16.

In the next S105, it is determined whether or not the final flag is 1. If the determination is negative, the process proceeds to step S106, and if the determination is positive, the numerical control work program is terminated.

In the next step S106, the next sections P (s0) and P (s1) are prepared as s0n → s0 and s0 + Δs → s1.

In the next step S107, it is determined whether or not s1> se. If the determination is negative, the process returns to step S102, and if the determination is positive, the process proceeds to step S108.

In the next step S108, the next time will be the final section, so after setting se → s1 and the final flag = 1, the process returns to step S102.

Next, an example of the embodiment will be described with reference to FIGS. 9 and 10. In the embodiment shown in FIGS. 9 and 10, the target curve P (s) is the entire circumference of a circle having a radius of 50 mm, the command speed F is F = 10000 mm / min, and the block processing time Tb is Tb = 4 msec. Further, from the viewpoint of easy understanding, in this embodiment, the radius of curvature r is fixed to a certain value on the chord error curved surface Sc (FIG. 4) which is a three-dimensional curved surface, and the command speed on the chord error curved surface Sc shown in FIG. 4 is fixed. Consider a two-dimensional graph showing the relationship between F and the chord error Ce. FIG. 9 shows the relationship between the command speed F and the chord error Ce when the radius of the target curve P (s) is 50 mm. That is, FIG. 9 shows a cross section in FIG. 4 when the radius of curvature r is r = 50 mm. The curve shown as the "string error curved surface" in FIG. 9 shows this cross section.

Further, in this embodiment, the maximum error Emax (mm) and the actual speed Vm (mm / min) were measured when the numerically controlled machine tool 20 was operated using the program created under the above conditions. Here, the maximum error Emax in the present embodiment is the maximum error between the target curve P (s) and the actual locus, and the actual velocity Vm is the average velocity in the actual motion. The maximum error Emax and the actual velocity Vm were acquired by capturing the actual locus into a personal computer with a cross grid encoder and analyzing the data. In FIG. 9, the horizontal axis is the command speed F and the actual speed Vm, and the vertical axis is the string error Ce and the maximum error Emax. That is, in FIG. 9, the coordinate systems of (F, Ce) and (Vm, Emax) are superimposed and displayed.

In this embodiment, the processing conditions of Case 1 which is a comparative example to which the present embodiment is not applied and Case 2 to which the present embodiment is applied are set, and both are compared. The string error Cep for programming was 0.01 mm in case 1 and 0.00111 mm in case 2. The processing conditions for each case are summarized below.
<Case 1>
Program string error Cep = 0.01 mm (about 157 square), command speed F = 10000 mm / min, radius of curvature r = 50 mm, block processing time Tb = 4 msec
<Case 2>
Program string error Cep = 0.00111 mm (about 471 square), command speed F = 10000 mm / min, radius of curvature r = 50 mm, block processing time Tb = 4 msec

Here, the program string error Cep of 0.01 mm in Case 1 is a numerical value often set in conventional processing. In FIG. 9, this point is indicated by a white circle labeled “Case 1 Directive”. On the other hand, the programming string error of 0.00111 mm in Case 2 is indicated by a white circle labeled "Case 2 Command". That is, the program string error Cep in Case 1 satisfies (Equation 3) but is separated from the string error curved surface Sc. That is, the string error Cep for the program allows a considerable margin from the viewpoint of the limitation due to the block processing time (the inequality of (Equation 3)). On the other hand, the program string error Cep in Case 2 is a point on the string error curved surface Sc (that is, it satisfies (Equation 4)). That is, the string error Cep for the program is as small as possible while satisfying (Equation 3).

Here, the relationship between the string error Cep for programming and the circle having a radius of 50 mm, which is the target curve P (s), will be described. When the program string error Cep and the radius of the target curve P (s) are determined, the actual processing locus is determined as a polygon. Specifically, when the program string error Cep is Cep = 0.01 mm, this polygon becomes approximately 157 squares, and when the program string error Cep is Cep = 0.00111 mm, this polygon is approximately 471. It becomes a polygon. That is, it is assumed that the processing accuracy of the case 2 is higher than that of the case 1.

Under the above conditions, the numerically controlled machine tool 20 was operated for each case. In FIG. 9, the black square described as "Case 1 result" indicates the result of processing by Case 1, and the black square described as "Case 2 result" indicates the result of processing by Case 2. The results are summarized below from FIG.
<Case 1>
Actual velocity Vm = 7847mm / min, maximum error Emax = 0.0168mm
<Case 2>
Actual velocity Vm = 9369mm / min, maximum error Emax = 0.0119mm

That is, in the result of case 2, the actual velocity Vm is faster than the result of case 1, and the maximum error Emax is smaller. The actual speed is higher, from the actual speed Vm = 7847 mm / min of the case 1 to the actual speed Vm = 9369 mm / min of the case 2. That is, by setting the program string error Cep = 0.01 mm in Case 1 to the program string error Cep = 0.00111 mm in Case 2, higher speed and higher accuracy were achieved.

Next, the results of this embodiment will be described in more detail with reference to FIG. FIG. 10A shows the result of Case 1, and FIG. 10B shows the result of Case 2. Further, in each of FIGS. 10A and 10B, the figure shown by <1> shows the trajectory of the error, and <2> shows the waveform of the actual speed Vm (denoted as “composite speed” in FIG. 10). There is. In <1>, the outer circle shows the target curve P (s), and the inner curve shows the enlarged error in the actual locus.

From the comparison between <1> in FIG. 10 (a) and <1> in FIG. 10 (b), it can be seen that the error in case 2 is smaller than the error in case 1. Further, from FIG. 10A <2>, the command speed F = 10000 mm / min has not been reached in the speed waveform of Case 1. This is because the direction change angle at the corners of the polygonal lines is large, so that deceleration occurs at each corner. That is, the command speed F = 10000 mm / min is not reached because the deceleration acceleration is repeated to the extent that it does not appear in the speed waveform of FIG. 10 (a) <2>. On the other hand, as shown in FIG. 10B <2>, in the case 2, since the direction change angle is small, the speed is not reduced so much, and the command speed F = 10000 mm / min is reached. As a result, the actual speed of Case 2 is faster than the actual speed of Case 1. It should be noted that the reason why the speed is increased at four points in FIG. 10A and <2> is that when the moving direction is 45 degrees (or 135 degrees), the speed is accelerated as the combined speed of the two axes. It is what happened.

The relationship between the direction change angle and the actual speed will be described with reference to FIG. FIG. 11 shows a state in which a direction change occurs at the corner Lc of the command line segment when the command line segment is created by the program string error Cep with respect to the target curve P. As shown in FIG. 11, when the direction change angle at the corner Lc of the command line segment is large, the numerical control device decelerates so as to reduce the error generated at the corner. On the other hand, if the direction change angle is small, the deceleration is not so much. This causes a difference in actual speed depending on the direction change angle.

As described in detail above, according to the numerical control program creation device, the numerical control work system, and the numerical control work program according to the present embodiment, the numerical control program that realizes higher speed and higher precision machining. Can be created. The reasons for higher speed and higher accuracy by making the chord error Cep for programming as small as possible based on the chord error curved surface Sc are summarized below.
(1) By reducing the chord error Cep for programming, the direction change angle at the corner of the line segment becomes smaller and the deceleration becomes smaller, so that the speed becomes higher.
(2) By reducing the chord error Cep for programming, the error from the target curve becomes smaller, and the accuracy becomes higher.
Further, in the present embodiment, when the string error Cep for the program is reduced as described above, the relationship represented by the equation (4) is taken into consideration, so that the block processing time cannot be met while improving the high speed and high accuracy. Not even. That is, the decrease in processing speed due to the block processing time not being in time is also suppressed. In this embodiment, the results are shown under specific conditions, but even in the examples performed under various other conditions, the string error Cep for programming is made as small as possible based on the string error curved surface Sc, and the result is similarly higher. We have confirmed that the speed and accuracy are high.

[Second Embodiment]
In the above embodiment, in step S103 shown in FIG. 7, the string error Ce corresponding to the radius of curvature r and the command speed F and satisfying (Equation 3) is as small as possible, that is, the string error Ce satisfying (Equation 4) is referred to as the program string error Ce. did. However, since the program string error Cep satisfying (Equation 4) is at the boundary of whether or not the block processing time Tb is in time, it is assumed that the block processing time Tb may not be in time in some cases. In that case, there is a possibility that the blocks that have been read and analyzed are insufficient and a sudden deceleration occurs.

ここで、ｋｆはｋｆ＞１．０で、１．０に近い値とする。(式５）に従うことは、図７に示すステップＳ１０３において、曲率半径ｒ、指令速度Ｆに対応し（式３）を満たす十分小さい弦誤差Ｃｅをプログラム用弦誤差Ｃｅｐとすることに相当する。 Therefore, in this embodiment, the following (Equation 5) is used instead of the above (Equation 4). (Equation 5) is obtained by multiplying the command speed F in (Equation 4) by the coefficient kf.

Here, kf is kf> 1.0, which is a value close to 1.0. Following (Equation 5) corresponds to setting a sufficiently small string error Ce corresponding to the radius of curvature r and the command speed F and satisfying (Equation 3) as the program string error Cep in step S103 shown in FIG.

上記αを用いて、（式５）は以下に示す（式７）のように簡略化される。

弦誤差Ｃｅは小さいので（式７）を解いた２根のうち小さい方をＣｅとすると、以下に示す（式８）となる。

ここで、弦誤差Ｃｅは実数であるため、ｒ^２－α×Ｆ^２≧０である。なお、ｋｆ＝１．０、Ｔｂ＝４ｍｓｅｃとした場合の（式８）における曲率半径ｒ、指令速度Ｆに対する弦誤差Ｃｅが図４に示す弦誤差曲面Ｓｃである。 Here, α is defined as shown in (Equation 6) below.

Using the above α, (Equation 5) is simplified as shown in (Equation 7) below.

Since the string error Ce is small, if the smaller of the two roots solved in (Equation 7) is Ce, the result is (Equation 8) shown below.

Here, since the string error Ce is a real number, r ² -α × F ² ≧ 0. The chord error Ce with respect to the radius of curvature r and the command speed F in (Equation 8) when kf = 1.0 and Tb = 4 msec is the chord error curved surface Sc shown in FIG.

むろん、求められる弦誤差曲面の精度等を勘案して第３項以降を採用してもよいが、ここでは簡便のため第２項までとしている。（式９）の近似式を用いても、プログラム用弦誤差Ｃｅｐを弦誤差曲面Ｓｃ上、あるいは弦誤差曲面Ｓｃ近傍とすることができる。 Here, if the square root portion is expanded into a polynomial in (Equation 8) and the second term is adopted, it can be approximated as in (Equation 9).

Of course, the third and subsequent terms may be adopted in consideration of the required accuracy of the chord error curved surface, etc., but here, for the sake of simplicity, the second term is used. Even if the approximate expression of (Equation 9) is used, the string error Cep for programming can be set on the string error curved surface Sc or in the vicinity of the string error curved surface Sc.

Here, in (Equation 8), for example, setting kf = 1.1 corresponds to F = 11000 mm / min even if the command speed F is F = 10000 mm / min (Equation 4). The string error Ce will be the program string error Ce. Alternatively, the string error Ce obtained in (Equation 4) may be multiplied by a coefficient kce to obtain the program string error Cep = kce × Ce. For example, if kce = 1.05, the string error Ce for programming is adopted with a value slightly larger than the string error Ce obtained from (Equation 4). Alternatively, r may be multiplied by a coefficient, or Tb may be multiplied by a coefficient. Further, parameters multiplied by a coefficient may be combined. In this embodiment, the string error Cep for the program is calculated in this way. The calculation means is a calculation means for calculating the target string error.

In other words, in the present embodiment, the string error Ce in the vicinity of the curved surface represented by (Equation 4) is set as the program string error Ce. In the present embodiment, it is a condition of the string error that the string error Ce in the vicinity of the string error curved surface is set as the program string error Ce. As a result, it is possible to prevent abrupt deceleration from occurring due to the block processing time Tb not being in time. Since the processing after determining the string error Cep for the program is the same as that of the above embodiment, detailed description thereof will be omitted.

[Third Embodiment]
In the above embodiment, the chord error Cep for programming was obtained using the block processing time Tb, the radius of curvature r, and the command speed F. On the other hand, the string error creating means 14 for programming according to the present embodiment has a string error Ce for a combination of the radius of curvature r and the command speed F in the target curve P (s) in a numerical control device having a certain block processing time Tb. The maximum value of is Cemax, and the string error Cep for programming is Cep = Cemax. That is, Cemax is calculated from the following (Equation 10) for the combination of the radius of curvature r and the command speed F in the target curve P (s). Here, in a numerical control device having a block processing time Tb, the relationship of the chord error Ce with respect to the combination of the radius of curvature r and the command speed F in the target curve P (s), that is, (Equation 8) is in the present embodiment. It is a function of the relationship between multiple parameters and the string error. The means for calculating Cemax by performing the max calculation on (Equation 8) is the calculation means for calculating the target string error in the present embodiment.

By setting Cemax shown in (Equation 10) as Cep, the block processing time Tb will not be in time for any radius of curvature r and any command speed F on the target curve P (s) as much as possible. The chord error Ce can be small or sufficiently small. That is, the chord error Ce represented by (Equation 8) is a chord error Ce that is as small as possible or sufficiently small with respect to an arbitrary radius of curvature r and a command speed F. On the other hand, by using Cemax, which is the maximum Ce corresponding to the combination of the radius of curvature r and the command speed F in the target curve P (s), the block processing time Tb cannot be met anywhere in the target curve P (s). A chord error Ce that is as small as possible or small enough is obtained.

Here, in the above embodiment, the Cep that changes according to the radius of curvature r and the command speed F in the target curve is obtained, but in the present embodiment, the Cep obtained for the target curve P (s) is obtained. It is one numerical value. In that sense, the present embodiment is simpler than the above embodiment.

The string error curved surface creating means 12 and the program string error creating means 14 according to the present embodiment may be incorporated in the numerical control program creating device 10 (CAM). Alternatively, the data output from the numerical control program creating device 10 may be incorporated into a post processor (not shown) that is a program tailored to each numerical control device. Further, it may be created outside the numerical control program creation device 10 or the post processor. When incorporated in the post processor or created outside the numerical control program creating device 10 or the post processor, the program creating means 16 shown in FIG. 1 can be an existing numerical control program creating device. That is, the obtained program string error Cep may be set or input as the setting value or input value of the string error for the existing numerical control program creation device (CAM).

Further, the calculation of the string error Cep for the program using (Equation 10) may be performed by checking the target curve P (s) before creating the program, or once the program is created by the existing CAM as before. The result may be checked to calculate the program string error Cep, and the program may be created again using the calculated program string error Cep.

[Fourth Embodiment]
A numerical control program creation device, a numerical control work system, and a numerical control work program according to the present embodiment will be described with reference to FIG. 12. FIG. 12 shows the numerical control program creating device 10A according to the present embodiment. In FIG. 12, the numerical control device and the numerical control machine tool 20 are not shown.

As shown in FIG. 12, the numerical control program creating device 10A includes a program string error creating means 14 and a program creating means 16. That is, the numerical control program creating device 10A is in a form excluding the string error curved surface creating means 12 in the numerical control program creating device 10. In the numerical control program creating device 10A, instead of using the chord error curved surface creating means 12, the chord error Cep for programming is calculated using the target curve index Ig representing the characteristics of the target curve P (s) and the block processing time Tb. Then, a program is created using the calculated chord error Cep for the program.

In the present embodiment, the target curve index Ig is the minimum radius of curvature rmin and the maximum command speed Fmax in the target curve P (s). With reference to FIG. 13, the minimum radius of curvature rmin and the maximum command speed Fmax will be described. The broken line shown in FIG. 13 indicates the target curve P (s) on the workpiece W. In FIG. 13, the smallest radius of curvature is rmin. On the other hand, the maximum command speed Fmax is Fmax = Max (F1, F2) when the command speed changes as F1, F2, F3, ... Depending on the location of the target curve P (s) as shown in FIG. , F3, ...). If the command speed is only F1, then Fmax = Max (F1) = F1.

Here, based on (Equation 8), the following (Equation 11) and (Equation 12) are obtained.

本実施の形態では、以上のようにして求められた最大弦誤差Ｃｅｍａｘをプログラム用弦誤差Ｃｅｐとしている。 From (Equation 11), it can be seen that the string error Ce increases as the radius of curvature r decreases. Further, it can be seen from (Equation 12) that the string error Ce increases as F increases. Therefore, assuming that the minimum radius of curvature on the target curve P (s) is rmin and the maximum command speed is Fmax, the maximum string error Cemax, which is the maximum possible string error Ce, is calculated from the following (Equation 13). Can be done. Here, as in the third embodiment, (Equation 8) is a function of the relationship between the plurality of parameters and the string error in the present embodiment. The means for calculating Cemax by applying rmin and Fmax to (Equation 8) is the calculation means for calculating the target string error in the present embodiment.

In the present embodiment, the maximum string error Cemax obtained as described above is defined as the program string error Cep.

According to the present embodiment having the above configuration, the block processing is performed for any radius of curvature r and any command speed F on the target curve P (s) as in the third embodiment. It is possible to obtain a program chord error Cep that is as small as possible or sufficiently small so that the time Tb is not missed. This point is the same as that of the third embodiment, but in the present embodiment, the string error Cep for the program can be obtained more easily than in the third embodiment.

In the present embodiment, the chord error Cep for the program is obtained from the already acquired block processing time Tb, the minimum radius of curvature rm in the target curve P (s), and the maximum command speed Fmax. Therefore, in the present embodiment, it is not necessary to obtain the string error curved surface Sc as in the above embodiment, and from this point as well, the present embodiment is a simpler form than the above embodiment.

For example, if the block processing time Tb is Tb = 4 msec, the minimum radius of curvature rmin is rmin = 25 mm, the maximum command speed Fmax is Fmax = 10000 mm / min, and the coefficient kf is kf = 1.1, it is for programming. The string error Cep is Cep = Cemax = 0.00269 mm.

In the numerical control program creation device 10A shown in FIG. 12, the portion surrounded by the broken line is a substantial input and an operation portion that receives the input. In the present embodiment, the operation portion is used to create a numerical control program. It is in the form of being incorporated in a device (CAM). However, the present invention is not limited to this, and as described in the third embodiment, it may be incorporated in the post processor, or may be created outside the numerical control programming device or the post processor. When incorporated in the post processor, or when the program is created outside the numerical control program creation device or the post processor, the program creation means of FIG. 12 can be an existing numerical control program creation device (CAM). That is, a form in which the obtained chord error Cep for programming is set or input as a setting value or input value of the chord error for the existing numerical control program creation device (CAM) (a configuration in which the program creation means 16 may be a CAM). It is also possible to.

Further, the method of obtaining the minimum radius of curvature rmin and the maximum command speed Fmax may be visually determined from the shape of the target curve P (s) and the drawing. Alternatively, once a program according to the conventional example is created by the existing numerical control program creation device, the created program is checked and obtained, and the program is created again by the program string error Cep obtained by (Equation 13). May be good. The minimum radius of curvature rmin may be obtained by the method described in the description with respect to FIG. Since the specific procedure for obtaining the above is conventionally known, detailed description thereof will be omitted.

[Fifth Embodiment]
Since the configuration of the numerical control program creation device according to the present embodiment is the same as that of the numerical control program creation device 10A according to the fourth embodiment, FIG. 12 will be referred to in detail if necessary. The explanation is omitted. The numerical control program creation device according to the present embodiment also obtains a program chord error Cep using the block processing time Tb and the target curve index Ig representing the characteristics of the target curve, and creates a program. However, in the present embodiment, instead of the radius of curvature r and the command velocity F in the target curve P (s), the normal acceleration An = F ² / r described by these parameters is focused on, and the maximum value Anmax thereof is focused on. Is the target curve index Ig that represents the characteristics of the target curve.

That is, if An = F ² / r in (Equation 9), it becomes (Equation 14) shown below. This is a function of the string error in this embodiment.

Therefore, assuming that the maximum value of the normal acceleration An on the target curve P (s) is the maximum normal acceleration Anmax, Cemax, which is the maximum possible Ce, can be expressed by the following (Equation 15). In this embodiment, this Cemax is referred to as a program string error Cep. In the present embodiment, the means for calculating Cemax from (Equation 15) is the calculation means for calculating the target string error.

Even if the maximum chord error Cemax calculated by using (Equation 15) is used, what method is calculated from the radius of curvature r and the command speed F in the target curve P (s) as in the fourth embodiment. Even for the linear acceleration An, it is possible to suppress that the block processing time Tb is not in time, and to obtain a chord error Ce that is as small as possible or sufficiently small, that is, a chord error Ce for programming. Since the processing after obtaining the program string error Cep is the same as that of the fourth embodiment, detailed description thereof will be omitted.

In the fourth embodiment, the minimum radius of curvature rm and the maximum command speed Fmax in the target curve P (s) are set as the target curve index Ig, and in the present embodiment, the radius of curvature r and the command in the target curve P (s). The maximum value Anmax of the normal acceleration An = F ² / r calculated from the velocity F was used as the target curve index Ig, but the target curve index is not limited to this, and if there is another index representing the characteristics of the target curve P (s), the target curve index Ig is used. The index may be the target curve index Ig.

[Sixth Embodiment]
In each of the above embodiments, a program string error Cep was calculated, and a numerical control program was created using the calculated program string error Cep. However, when a numerical control program is created using the program string error Cep as in each of the above embodiments, for example, the numerical control program length becomes longer, and the calculation time in program creation becomes longer than expected. Such phenomena may occur.

Therefore, in the present embodiment, it is decided to set the string error lower limit value Cemin in the string error Cep for the program. This prevents the string error Cep for the program from becoming excessively small, and as a result, suppresses the calculation time in program creation from becoming unexpectedly long.

For example, under the conditions of the embodiment of the first embodiment, assuming a radius of curvature r = 200 mm, the program string error is Cep = 0.00028 mm, but the value of this program string error Cep is unnecessary. It is considered to be a small value. Therefore, in the present embodiment, the lower limit value Cemin of the string error is set in the string error Cep for the program, and when Cep <Cemin, the string error Cep for the program is set to Cep = Cemin. In the present embodiment, the means for performing such calculation is the calculation means for calculating the target string error. As a specific value of the string error lower limit value Cemin, for example, Cemin = 0.001 mm can be set. As a result, it is possible to prevent the numerical control program from becoming unnecessarily long and the calculation time for creating the program from becoming long. Since the processing after obtaining the string error Cep for the program is the same as that of each of the above-described embodiments, detailed description thereof will be omitted.

As described in detail above, in the present invention, a chord error Cep for programming suitable for high speed and high precision machining is obtained based on the command speed F, the block processing time Tb, and the radius of curvature r of the target curve P (s). , The program of the minute line segment is created by the obtained chord error Cep for the program. At this time, the string error Cep for programming may be a point on the string error curved surface Sc, or may be a point near the string error curved surface Sc obtained by a predetermined procedure. As a result, in curve machining using a numerical control machine tool, it has become possible to create a numerical control program suitable for higher speed and higher precision machining than in the prior art and instruct the numerical control device. As a result, the numerical control machining system according to the present invention can perform higher speed and higher precision machining as compared with the prior art. Therefore, the numerical control work system according to the present invention can improve the processing efficiency and contribute to energy saving.

1 Numerical control machine system 10, 10A Numerical control program creation device 12 String error curved surface creation means 14 Program string error creation means 16 Program creation means 20 Numerical control machine Ce String error Cep Program string error Cemax Maximum string error Cemin string Error lower limit F Command speed Ig Target curve index Tb Block processing time rmin Minimum radius of curvature Fmax Maximum command speed r Curved radius P (s) Target curve Sc String error Curved surface An Normal acceleration Anmax Maximum normal acceleration s Distance Δs Small distance W Workpiece

Claims (11)

Numerical control that performs machining along a target curve A numerical control program creation device that creates a numerical control program that indicates commands to a numerical control device that controls a machine tool.
A plurality of parameters of a block processing time indicating the processing time of the numerical control device, a command speed for specifying the processing speed of the numerical control device, a radius of curvature in the target curve, and a chord error for approximating the target curve by a line segment. A storage means to memorize the relationship between
A calculation means for calculating a target string error using the relationship between the plurality of parameters based on the condition of the string error in controlling the numerical control machine tool by the numerical control device.
A program creation means for creating an approximate line segment for the target curve based on the target string error, and
Numerical control programming device including. The numerical control program creating device according to claim 1, wherein the relationship between the plurality of parameters is a chord error curved surface showing the relationship between the block processing time, the command speed, the radius of curvature, and the chord error. The numerical control program creating device according to claim 2, wherein the string error condition is a condition for designating a point on the string error curved surface. The numerical control program creating device according to claim 2, wherein the string error condition is a condition for designating a point in the vicinity of the string error curved surface. The numerical control according to claim 4, wherein the calculation means calculates the target string error by multiplying any of the block processing time, the command speed, the radius of curvature, and the string error by a correction coefficient larger than 1. Program creation device. The relationship between the plurality of parameters is a function of the string error with the command speed and the radius of curvature as variables.
The calculation means calculates the maximum value of the string error with respect to the combination of the command speed and the radius of curvature in the target curve by using the function of the string error, and uses the maximum value of the string error to calculate the target string error. The numerical control program creating device according to claim 1. The relationship between the plurality of parameters is a function of the string error with the command speed and the radius of curvature as variables.
The calculation means calculates the maximum value of the command speed and the minimum value of the radius of curvature in the target curve, and uses the maximum value of the command speed and the minimum value of the radius of curvature based on the function of the chord error. The numerical control program creating device according to claim 1, wherein the target string error is calculated. The function of the string error is a function of the normal acceleration represented by the command speed and the radius of curvature.
The calculation means calculates the maximum value of the normal acceleration in the target curve, and calculates the target chord error based on the function of the normal acceleration using the maximum value of the normal acceleration. The described numerical control program creation device. The calculation means sets a minimum value for the target string error, and when the calculated target string error is less than the minimum value, the minimum value is calculated as the target string error. The numerical control program creation device according to any one of 8. The numerical control program creating device according to any one of claims 1 to 9.
Numerical control machine tools that perform machining along the target curve,
A numerical control machine tool including a numerical control device for controlling the numerical control machine tool based on a program created by the numerical control program creation device. Numerical control that performs machining along a target curve Creates a numerical control program that indicates commands to a numerical control device that controls a machine tool. Numerical control program creation program for operating a numerical control machine tool.
Computer,
A plurality of parameters of the block processing time indicating the processing time of the numerical control device, the command speed for specifying the processing speed of the numerical control device, the radius of curvature in the target curve, and the chord error for approximating the target curve by a line segment. A storage means to memorize the relationship between
A calculation means for calculating a target string error using the relationship between the plurality of parameters based on the condition of the string error in controlling the numerical control machine tool by the numerical control device.
A program creation means for creating an approximate line segment for the target curve based on the target string error, and
Numerical control work program to function as.

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