JP2006007363A - Nc program correcting device and nc program generating device including it - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an NC program correcting device, correcting the feed speed to the proper speed to obtain the machined surface with proper accuracy from the beginning in consideration of vibration caused by acceleration and deceleration of a feed shaft. <P>SOLUTION: This NC program correcting device includes: an NC program storage part 5 for storing an NC program; a vibration characteristic storage part 8 for storing data related to the vibration characteristics of an NC machine tool used in machining; and an NC program correction processing part 9 for setting the data related to the limit acceleration change rate for preventing excessive vibration of the NC machine tool concerning the feed speed of the tool on the basis of the vibration characteristic data stored in the vibration characteristic storage part 8, analyzing the NC program stored in the NC program storage part 5 to calculate the change rate related to the cutting feed acceleration of the tool and determine whether or not the calculated change rate exceeds the limit acceleration change rate, and correcting the concerned cutting feed speed to be below the limit acceleration change rate when it exceeds the limit acceleration change rate. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention is an NC program used for control of an NC machine tool, and includes a plurality of command blocks, and the feed speed of the NC program including at least data relating to a tool movement path and its feed speed is set to an appropriate speed. The present invention relates to an NC program correcting device that corrects to NC and an NC program generating device equipped with the NC program correcting device.

  As an apparatus that automatically generates an NC program using design data of a workpiece (hereinafter referred to as a workpiece) created by CAD (Computer Aided Design), an NC using a CAM (Computer Aided Manufacturing) method has been conventionally used. A program generator is known.

  Design data created by CAD (hereinafter referred to as CAD data) includes shape data indicating the final shape and dimensions of a workpiece after machining, for example, data such as coordinate data and mathematical data, and data relating to dimension lines. After extracting only the workpiece shape data from such CAD data, the NC program generating device can determine whether the workpiece shape is circular, rectangular, cylindrical, prismatic, convex, or concave. Data necessary for generating NC programs, such as workpiece shape characteristics such as curved surfaces, data related to machining methods such as tools used and cutting conditions, etc. are received and inputted by an operator using an input device as appropriate. An NC program is generated based on the acquired data and the shape data extracted from the CAD data.

  However, in such an NC program generation device, as described above, the operator inputs data related to the feature of the workpiece shape and data related to the machining method, which are data necessary for generating the NC program. Therefore, there is a problem that it takes a long time to input data and, therefore, it takes a long time to process the workpiece, and it is difficult to completely prevent human error in the data input. Becomes a defective product, or the tool is damaged.

  Also, when machining using the generated NC program, if the expected result cannot be obtained due to tool chatter or overload, etc., it is necessary to investigate the cause that requires a long time and correct the NC program. In order to perform such correction work, it is necessary to return to the initial stage of processing in the NC program generation device, and it takes a long time to re-output the corrected NC program. There is also a problem that the machine tool must be stopped.

  Therefore, the present applicant has already proposed an NC program generation device (tool path data generation device) disclosed in Japanese Patent Application Laid-Open No. 2001-75624 in order to solve such a problem. According to this NC program generating device, since the feature data extraction processing unit and the processing method setting processing unit are provided, the data related to the feature shape of the workpiece, the data related to the processing method such as the tool to be used, and the cutting conditions, etc. The NC program can be generated quickly, and human input errors cannot occur. Therefore, the input error can cause the workpiece to become defective or damage the tool. There will be no problems.

  If the processing method set by the processing method setting processing unit and the processing related information generated by the processing related information generation processing unit are output to the outside as a processing scenario from the processing scenario output processing unit, actual processing In this case, even if the tool chatter phenomenon occurs or the expected result is not obtained due to overload, etc., it is possible to quickly find the cause by referring to the output machining scenario. .

JP 2001-75624 A

  By the way, the NC machine tool is not composed of a complete rigid body, but easily vibrates by the movement of a structure constituting the NC machine tool, such as a spindle or a table. This is because the vibration component is included in the acceleration when the structure moves.

  When this vibration has a frequency close to the natural frequency of the NC machine tool, the NC machine tool is in a resonance state, and is larger than the amplitude of the input vibration (vibration caused by acceleration of the moving structure). Vibrates with large amplitude. In particular, when a resonance state is reached during cutting, this affects the machined surface, and the surface accuracy deteriorates.

For example, as shown in FIG. 6A, when the tool moves so that the trajectory draws an arc from a straight line on the XY plane, the feed speed of the tool in arc machining is usually set as a constant value. Therefore, in terms of machine control, each feed axis is controlled such that a feed speed F obtained by combining the feed speed FX of the _X axis and the feed speed F _{Y of the} Y axis becomes a set value. That is, the feed rates F _X and F _Y of the X axis and the Y axis are accelerated and decelerated every moment according to the moving position of the tool. Therefore, when the acceleration / deceleration includes a vibration component close to the natural frequency of the NC machine tool, the NC machine tool is in a resonance state as described above, and the surface accuracy of the machining surface is deteriorated. become.

  However, the conventional NC program generation device represented by the above-mentioned Japanese Patent Application Laid-Open No. 2001-75624 employs a feed speed generally set based on the shape of the tool, its material, and the material of the workpiece, etc. A program is generated, and the vibration associated with the acceleration / deceleration is not considered at all.

  For this reason, even if machining is performed using the automatically generated NC program as it is, it may not be possible to obtain a machined surface with a predetermined accuracy. Eventually, trial machining is performed using the NC program. After verifying the results, for those parts with poor surface accuracy, the NC program had to be modified to achieve an appropriate feed rate (vibration was appropriate and the fastest feed rate) after trial and error. .

  The present invention has been made in view of the above circumstances, and considering the vibration associated with acceleration / deceleration of the feed shaft, the feed speed is corrected to an appropriate speed so that a machining surface with appropriate accuracy can be obtained from the beginning. An object of the present invention is to provide an NC program correcting device and an NC program generating device having the NC program correcting device.

The present invention for achieving the above object is an NC program used for controlling an NC machine tool, comprising an NC program comprising a plurality of command blocks and including at least data relating to a tool movement path and its feed speed. An NC program storage unit for storing;
A vibration characteristic storage unit for storing data relating to vibration characteristics of the NC machine tool used for machining;
Based on data relating to the vibration characteristics of the NC machine tool used for the machining stored in the vibration characteristic storage unit, the limit acceleration for preventing excessive vibration of the NC machine tool with respect to the feed rate of the tool While setting data related to the variation rate, the NC program stored in the NC program storage unit is analyzed to calculate a variation rate related to the cutting feed acceleration of the tool, and the calculated variation rate is the critical acceleration variation rate NC program correction configured by providing an NC program correction processing unit that corrects the corresponding cutting feed rate so that the rate of change is below the limit acceleration fluctuation rate. Related to the device.

  According to the NC program correcting device according to the present invention, first, an appropriately created NC program is stored in the NC program storage unit.

  Next, in the NC program correction processing unit, the limit acceleration fluctuation for preventing excessive vibration of the NC machine tool with respect to the feed rate of the tool based on the data relating to the vibration characteristic stored in the vibration characteristic storage unit Processing to set the rate is performed.

  As an example of the vibration characteristic data, data representing the correlation between the vibration frequency and the vibration amplitude can be cited as an example. The moving body (table, etc.) of the machine tool is moved at an appropriate speed. This is obtained by detecting the vibration at the time and analyzing the frequency, or by applying an appropriate impact to the machine tool and detecting the vibration caused by the impact and analyzing the frequency. The vibration characteristic data acquired as described above is stored in the vibration characteristic storage unit in advance.

  Next, in the NC program correction processing unit, the NC program stored in the NC program storage unit is sequentially analyzed to calculate the variation rate related to the cutting feed acceleration of the tool, and the calculated variation rate is the critical acceleration variation rate. Is determined, and when the limit acceleration fluctuation rate is exceeded, the corresponding cutting feed speed is corrected so as to be equal to or less than the limit acceleration fluctuation rate.

  The variation rate of the cutting feed acceleration is obtained by differentiating the cutting feed acceleration calculated by differentiating the cutting feed rate data included in the NC program and then further differentiating the calculated cutting feed acceleration. As for the limit acceleration fluctuation rate, the acceleration fluctuation rate in the vicinity where the surface accuracy of the machined surface exceeds the allowable value due to the vibration of the NC machine tool can be applied, or a predetermined ratio can be obtained from this acceleration fluctuation rate. A value obtained by subtracting (for example, 10%) can be applied.

  The limit acceleration fluctuation rate is not calculated from the vibration characteristics of the NC machine tool each time, but is calculated in advance from the vibration characteristics and appropriately stored in a storage unit (limit acceleration fluctuation rate storage unit). You may do it. In this case, the NC program correction processing unit determines whether or not the calculated variation rate exceeds the limit acceleration variation rate stored in the limit acceleration variation rate storage unit. The corresponding cutting feed rate is corrected so as to be equal to or less than the limit acceleration fluctuation rate.

  Further, when it is determined that the acceleration fluctuation rate of the cutting feed rate between the two command blocks exceeds the limit acceleration fluctuation rate, the NC program correction processing unit determines that at least one of the two command blocks is a plurality of The command block is divided into command blocks, and the cutting feed speed of a new command block corresponding to the two command blocks is set to a cutting feed speed at which the acceleration fluctuation rate between the blocks is equal to or less than the limit acceleration fluctuation rate. May be.

  Further, when it is determined that the acceleration fluctuation rate of the cutting feed speed between the two command blocks exceeds the limit acceleration fluctuation rate, the NC program correction processing unit determines the cutting feed in at least one of the two command blocks. It may be configured to define the velocity as a non-stationary rational spline function.

  In addition, the NC program correction device described above, a shape data storage unit that stores shape data related to the three-dimensional shape of the workpiece, information related to the cutting speed and cutting amount according to the material material, and tool information are stored. An NC program is generated based on the tool / machining information storage unit, the three-dimensional shape data of the workpiece stored in the shape data storage unit, and the information stored in the tool / machining information storage unit. The NC program generation device includes an NC program generation processing unit that stores the NC program stored in the NC program storage unit, and the NC program cutting feed rate automatically generated by the NC program generation processing unit is corrected to the NC program. You may make it correct so that it may become an appropriate feed rate with an apparatus.

  As described above in detail, according to the present invention, the limit acceleration fluctuation rate is set, the NC program is sequentially analyzed, the change in the cutting feed speed of the tool is detected, and the cutting acceleration fluctuation rate associated with this speed change is detected. When the calculated cutting feed acceleration fluctuation rate exceeds the limit acceleration fluctuation rate, the corresponding cutting feed speed is corrected to be less than this, so that the NC machine tool is used during actual machining. Can be obtained without going through trial and error such as trial machining, and the NC program can be continuously generated from the generation of the NC program. A series of operations up to processing can be performed efficiently in a short time.

  Hereinafter, specific embodiments of the present invention will be described with reference to the accompanying drawings. FIG. 1 is a block diagram showing a schematic configuration of the NC program generating device according to the present embodiment.

  As shown in the figure, the NC program generation device 1 of this example includes an NC program generation processing unit 6 and an NC program correction processing unit 9 connected to each other via a bus line 2, and shape data storage. 3, tool / machining information storage unit 4, NC program storage unit 5 and vibration characteristic data storage unit 8, input / output interface 10, input device 11 and output device connected to input / output interface 10 The NC program storage unit 5, the vibration characteristic data storage unit 8 and the NC program correction processing unit 9 constitute an NC program correction device 7. Details of each part will be described below.

  The shape data storage unit 3 is a functional unit that stores three-dimensional shape data of a workpiece (hereinafter referred to as “work”), and is input from the input device 11 online or via an appropriate portable recording medium. Shape data is stored. For this shape data, for example, data unnecessary for NC program generation such as data related to dimension lines is removed from workpiece design data created using CAD, and only data necessary for generation of the NC program is obtained. Is obtained by extracting.

  The tool / machining information storage unit 4 is a functional unit that stores tool information and machining information. Specifically, a machining mode (contour line machining, scanning line machining, linear interpolation, circular interpolation, Air cut avoidance processing type), tool information such as tool type (model, material, etc.) and tool diameter, cutting speed set for each tool type according to material material, cutting amount per turn, machining allowance, etc. The data about is stored.

  The NC program generation processing unit 6 performs feature data extraction processing, machining method based on the three-dimensional shape data of the workpiece stored in the shape data storage unit 3 and information stored in the tool / machining information storage unit 4. The setting process and the NC program generation process are sequentially executed to generate an NC program, and the generated NC program is stored in the NC program storage unit 5.

  The feature data extraction processing is based on the shape data stored in the shape data storage unit 3, and after recognizing the region to be processed from the regions set by the shape data, This is a process for extracting features related to the three-dimensional shape of a workpiece, and a simple shape extraction process for extracting a relatively simple shape element in the region directly extracted from the shape data, for example, a shape element such as a cylindrical shape or a prism shape, In addition, a free-form surface extraction process for extracting a feature shape in the region for a free-form surface that cannot be directly extracted from the shape data is included.

  The machining method setting process searches the tool / machining information storage unit 4 based on the feature data extracted by the feature data extraction process, and for each machining area, an optimum machining mode, the type of tool used, The content of the cutting is to set cutting conditions, etc.When performing repeated machining with a predetermined machining cycle, the feed pitch is set based on the finished surface roughness, etc., and a common tool is used in multiple machining areas. When used, the processing order of each processing region is determined in consideration of processing efficiency, such as processing the processing regions as continuously as possible. This processing method setting process is easy if the processing method is divided into a plurality of regions according to the feature shape and then the processing method is set for each of the divided processing regions. And it can be done quickly.

  The NC program generation process is based on the machining method set by the machining method setting process, and sequentially includes the contents of the tool movement path, rotation speed, movement speed, etc. for each machining area in accordance with the set machining order. The generated NC programs are sequentially stored in the NC program storage unit 5.

The vibration characteristic data storage unit 8 is a functional unit that stores data related to vibration characteristics unique to an NC machine tool that may be used for machining. In this embodiment, as the vibration characteristic data, the data representing the correlation between the magnitude of the vibration frequency omega _n the vibration amplitude level W _L as shown in FIG. 2 (a), acceleration as shown in FIG. 2 (b) Stored is data (relational expression) representing the correlation between the vibration frequency ω _n corresponding to the magnitude of the fluctuation rate and the vibration acceleration level M _α .

Correlation data between the vibration frequency omega _n the vibration amplitude level W _L detects vibrations when moving a moving body NC machine tool (table etc.) at an appropriate rate, or frequency analysis this, or 2 is obtained by applying a suitable shock to the NC machine tool, detecting the vibration caused by the shock, and analyzing the frequency thereof, and the data as shown in FIG. It is stored in the vibration characteristic data storage unit 8. The correlation data between the oscillation frequency omega _n the vibration amplitude level W _L is is not necessary that for all frequencies, the value of the oscillation frequency omega _n corresponding thereto and the peak value of the vibration amplitude level W _L data You may make it memorize | store in the format of a table.

  Further, as described above, when an external force is applied to an object and the object is moved at a predetermined speed, if the acceleration applied to the moving object fluctuates, the fluctuation includes a predetermined vibration component. As a result, the structure including the moving object vibrates. This vibration component (vibration acceleration level and vibration frequency) is determined according to the magnitude (acceleration fluctuation rate) of the fluctuation of the acceleration, and can be obtained as follows.

For example, as shown in FIG. 3A, if the object is moved so that the acceleration fluctuation rate shows a constant value for a certain time, in other words, the acceleration fluctuation rate shows a rectangular wave, the acceleration is the acceleration While the fluctuation rate has a constant value, the acceleration increases in a linear line, and thereafter becomes a constant value. Then, as shown in FIG. 3B, when the acceleration magnitude in the steady state is made constant and the rectangular wave time (time during which the acceleration rises) is lengthened, the acceleration fluctuation rate becomes smaller.
From the above, the following relationship is derived.
(Rectangular wave time) × (acceleration fluctuation rate magnitude) = constant In other words, the area of the rectangular wave is constant.

Therefore, if the time width of the rectangular wave (that is, the acceleration rising time) is appropriately changed while the magnitude of acceleration in the steady state is constant, each time width and the acceleration fluctuation rate corresponding to the time width (the height of the rectangular wave). ), That is, rectangular waves having different time widths and heights. Each obtained rectangular wave includes a vibration component corresponding to the magnitude of the acceleration fluctuation rate. Therefore, the included vibration components (vibration acceleration level and vibration frequency) can be analyzed by performing FFT (Fast Fourier Transform) analysis on each rectangular wave. FIG. 4 shows the relationship between the vibration acceleration level M _α and the vibration frequency ω _n for each rectangular wave having a different time width analyzed in this way.

Thus, from the above analysis results, the method according to the magnitude of the acceleration fluctuation rate (for example, acceleration fluctuation rates A, B, C...) As shown in FIG. About) calculated the vibration acceleration level M _alpha approximate expression representing the relationship between vibration frequency omega _n (the equation), resulting relational expression is being stored in the vibration characteristic data storage unit 8 as described above.

  The NC program correction processing unit 9 is data stored in the vibration characteristic data storage unit 8 and relates to the feed rate of the tool based on the data related to the vibration characteristics of the NC machine tool used for the machining, A process of setting a limit acceleration fluctuation rate for preventing excessive vibration of the NC machine tool, and an analysis of the NC program generated by the NC program generation processing unit 6 and stored in the NC program storage unit 5, Calculate acceleration fluctuation rate related to cutting feed, determine whether the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate, and if it exceeds the limit acceleration fluctuation rate, fall under the limit acceleration fluctuation rate A process of correcting the cutting feed rate by increasing / decreasing and updating the NC program stored in the NC program storage unit 5 with the corrected NC program. Nau.

Specifically, NC program correction processor 9, for example, as shown in FIG. 2 (a), when the vibration frequency omega ₁ and omega _2, the vibration amplitude level _{W L} peak value 0.01 and 0. when indicating the 005, the correlation between the vibration frequency omega _n corresponding to the magnitude of the acceleration shown in FIG. 2 (b) and the vibration acceleration level M _alpha, the vibration acceleration level M _alpha in the oscillation frequency omega ₁ and omega ₂ The calculation is made for each feed acceleration fluctuation rate A, B, and C, and the vibration level L of the NC machine tool caused by the feed acceleration fluctuation is calculated for each feed acceleration fluctuation rate A, B, and C based on the following equation. calculate.

Vibration level L = Σ ((vibration amplitude level _{W L} of omega _n) × (vibration acceleration level M _alpha of omega _n))

In the example shown in FIG. 2, the vibration level LA when the feed acceleration fluctuation rate is _A is
L _A = 0.01 × 1.0 + 0.005 × 0.84 = 0.142
And
The vibration level L _B when the feed acceleration fluctuation rate is _B is
L _B = 0.01 × 0.96 + 0.005 × 0.61 = 0.01265
And
Vibration level L _C when feeding the acceleration variation rate of C is
L _C = 0.01 × 0.76 + 0.005 × 0.40 = 0.0096
It becomes.

  Then, after calculating the vibration level L corresponding to the fluctuation of the feed acceleration in this way, the NC program modification processing unit 9 determines the limit based on the limit vibration level set in advance for the NC machine tool. The feed acceleration fluctuation rate is calculated. Specifically, for example, when the limit vibration level is 0.01280, the feed acceleration fluctuation rate B having a smaller value and the largest value is set as the limit feed acceleration fluctuation rate. The limit vibration level is set empirically.

  Next, the NC program correction processing unit 9 sequentially analyzes the NC program stored in the NC program storage unit 5, detects a change in the cutting feed speed of the tool, and calculates an acceleration fluctuation rate associated with this speed change. Then, it is determined whether or not the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate. If the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate, the corresponding cutting feed rate is increased or decreased so as to be equal to or less than the limit acceleration fluctuation rate. Correct this.

For example, when the tool moves to perform arc cutting as shown in FIG. 6A, the cutting feed speed of the tool included in the NC program is set to a constant value as described above, but the NC program is modified. After detecting the data related to the cutting feed rate of the tool, the processing unit 9 calculates the cutting feed rate (F _X , F _Y ) for each feed axis (FIG. 6 (b)), and then differentially processes this. Then, the cutting feed acceleration (α _X , α _Y ) for each feed axis is calculated (FIG. 6C), and the calculated cutting feed acceleration (α _X , α _Y ) is further differentiated to obtain an acceleration fluctuation rate ( J _X , J _Y ) is calculated (FIG. 6D), and it is determined whether or not the calculated acceleration fluctuation rate (J _X , J _Y ) exceeds the limit acceleration fluctuation rate.

  According to the NC program generating device 1 of the present example having the above configuration, first, based on the shape data stored in the shape data storage unit 3 and the data stored in the tool / machining information storage unit 4, the tool The NC program including the contents of the movement path, the number of revolutions, the feed speed, and the like is generated by the NC program generation processing unit 6 and the generated NC program is stored in the NC program storage unit 5.

  Next, the NC program correction processing unit 9 sets a limit acceleration fluctuation rate for preventing excessive vibration of the NC machine tool with respect to the tool feed speed based on the data stored in the vibration characteristic data storage unit 8. At the same time, the NC program stored in the NC program storage unit 5 is analyzed to calculate the acceleration fluctuation rate related to the cutting feed of the tool, and it is determined whether or not the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate. When the critical acceleration fluctuation rate is exceeded, the corresponding cutting feed speed is corrected so as to be equal to or less than the critical acceleration fluctuation rate, and the NC program stored in the NC program storage unit 5 with the corrected NC program is stored. Is updated.

  Thus, according to the NC program generation device 1 of this example, the limit acceleration fluctuation rate is set, the NC program is sequentially analyzed, and the change in the cutting feed speed of the tool is detected, and the acceleration accompanying this speed change is detected. The fluctuation rate is calculated, and when the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate, the corresponding cutting feed speed is corrected so as to be less than this. Can be generated from the beginning without trial and error such as trial machining, and this can be achieved from the generation of the NC program. A series of operations up to the used continuous processing can be performed in a short time and efficiently.

  As mentioned above, although embodiment of this invention was described, it cannot be overemphasized that the specific aspect which this invention can take is not limited to the thing of an upper example at all.

For example, in the above example, a relational expression between the vibration acceleration level M _α and the vibration frequency ω _n corresponding to the magnitude of the acceleration fluctuation rate is calculated, and the calculated relational expression is stored in the vibration characteristic data storage unit 8. However, the present invention is not limited to this. As shown in FIG. 5, the relationship between the vibration acceleration level M _α and the vibration frequency ω _n for each magnitude of each acceleration fluctuation rate is created as a data table. It may be stored in the vibration characteristic data storage unit 8 and the above-mentioned limit feed acceleration fluctuation rate may be set based on this data table.

  Further, the limit acceleration fluctuation rate is not calculated from the vibration characteristics of the NC machine tool each time, but is calculated in advance from the vibration characteristics, and this is calculated as shown in FIG. It may be stored in the data storage unit 13. In this case, the NC program correction processing unit 9 ′ determines whether or not the calculated acceleration fluctuation rate exceeds the limit acceleration fluctuation rate stored in the limit acceleration fluctuation rate data storage unit 13, and exceeds the limit acceleration fluctuation rate. Is corrected by increasing / decreasing the corresponding cutting feed rate so as to be equal to or less than the limit acceleration fluctuation rate. In this case, the NC program storage unit 5, the vibration characteristic data storage unit 13 and the NC program correction processing unit 9 'constitute an NC program correction device 7'.

  Further, the method of correcting the cutting feed rate when the acceleration fluctuation rate exceeds the limit acceleration fluctuation rate is not limited to the method of simply increasing or decreasing the corresponding cutting feed rate as in the above example.

For example, as shown in FIG. 8 (a) and (b), the block A commands the feedrate moves from the position _{P 1} in 1.0 mm / min to _{P 2,} following this instruction block A, There is a block B that commands to move from the position P ₂ to P ₃ at a feed speed of 0.4 mm / min, and the acceleration fluctuation rate between the command blocks A and B exceeds the limit acceleration fluctuation rate. as shown in FIG. 8 (c) and (d), the command block a, 'and block _{a 1} to commanded to move to the position _{P 2'} from the position _{P 1 P 2} to move from the _{P 2} The block is divided into the block A ₂ to be commanded, and the block B ₁ that commands the command block B to move from the position P ₂ to P ₃ ′ and the block that commands to move from the position P ₃ ′ to P ₃ Tomo and divided into a B ₂ , Instruction block _A 1 _consecutive, A _2, B 1, as the feed rate of _{B 2} decreases successively in stages, for example, the feed speed F in the command block _{A 1} 1.0 mm / min, instruction block _{A 2} The feed speed of each command block is 0.8 mm / min, the feed speed F in the command block B ₁ is 0.6 mm / min, and the feed speed F in the command block B ₂ is 0.4 mm / min. May be set.

  Further, in the above case, the feed speed in at least one of the command blocks A and B is defined by an unsteady rational spline function (NURBS function), and the feed speed in the block is gradually changed. Also good.

  The NURBS function can define a free curve by specifying some control point data and data such as “weight”, “knot”, etc., and the NURBS of the kth floor ((k−1) th order). The general formula of the function is shown in the following formula (1).

  As shown in Equation 1, the NURBS function is a function having a parameter t as a variable, and is represented by a vector C (t). The basis function N is expressed by the following formulas 2 and 3.

Here, “C _i ” is a control point vector (0 ≦ i ≦ n), “w _i ” is a weight (0 ≦ i ≦ n), and “x _i ] is a knot (x _i ≦ x _{i + 1} ). , [X ₀ , x ₁ ,... X _m ] (m = n + k) are knot vectors.

Thus, from this general formula, the velocity vector (F (t)) relating to the feed rate is defined by the following formula 4, and the control point vector (C _Fi ) related to each NURBS function, as well as the “weight” (w _i ) And by specifying data relating to “knots” (x _i ).

For example, when the feed speed in the command block A shown in FIGS. 8A and 8B is defined by the NURBS function, as shown in FIG. 9, four control points C _F0 , C _F1 , C _F2 , and each X-axis coordinate value of the _{C F3 (X 0, ..,} X 3) and feed values _{(F 0, .., F 3} ) and are identified by a predetermined "weight" and "knots" data, which Is expressed as an NC program, the feed rate in the block can be gradually changed.

  As described above, the NC program correcting device according to the present invention and the NC program generating device including the NC program correcting device are suitable as devices for optimizing the NC program used for controlling the NC machine tool.

It is the block diagram which showed schematic structure of the NC program generation apparatus which concerns on one Embodiment of this invention. It is explanatory drawing for demonstrating the setting process of the limit acceleration fluctuation rate which concerns on this embodiment. It is explanatory drawing for demonstrating the correlation with an acceleration fluctuation rate, a vibration frequency, and a vibration acceleration level. It is explanatory drawing for demonstrating the correlation with an acceleration fluctuation rate, a vibration frequency, and a vibration acceleration level. It is explanatory drawing which showed the data table as another example of the correlation data of an acceleration fluctuation rate, a vibration frequency, and a vibration acceleration level. It is explanatory drawing for demonstrating a feed acceleration and a feed acceleration fluctuation rate. It is the block diagram which showed schematic structure of the NC program generation apparatus which concerns on the other form of this invention. It is explanatory drawing for demonstrating the NC program correction method which concerns on the other form of this invention. It is explanatory drawing for demonstrating the NC program correction method which concerns on the other form of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 NC program production | generation apparatus 3 Shape data memory | storage part 4 Tool and process information memory | storage part 5 NC program memory | storage part 6 NC program production | generation processing part 7 NC program correction apparatus 8 Vibration characteristic data storage part 9 NC program correction | amendment processing part

Claims (5)

NC program used for controlling an NC machine tool, comprising a plurality of command blocks, and an NC program storage unit for storing an NC program including at least data relating to a tool movement path and its feed speed;
A vibration characteristic storage unit for storing data relating to vibration characteristics of the NC machine tool used for machining;
Based on data relating to the vibration characteristics of the NC machine tool used for the machining stored in the vibration characteristic storage unit, the limit acceleration for preventing excessive vibration of the NC machine tool with respect to the feed rate of the tool While setting data related to the variation rate, the NC program stored in the NC program storage unit is analyzed to calculate a variation rate related to the cutting feed acceleration of the tool, and the calculated variation rate is the critical acceleration variation rate And an NC program correction processing unit that corrects the corresponding cutting feed rate so as to be equal to or less than the limit acceleration fluctuation rate when the limit acceleration fluctuation rate is exceeded. NC program modification device. NC program used for controlling an NC machine tool, comprising a plurality of command blocks, and an NC program storage unit for storing an NC program including at least data relating to a tool movement path and its feed speed;
Limit acceleration for storing data relating to the rate of change of limit acceleration for preventing excessive vibration of the NC machine tool, which is set according to the vibration characteristics of the NC machine tool used for machining, with respect to the feed rate of the tool A fluctuation rate storage unit;
The NC program stored in the NC program storage unit is analyzed to calculate a variation rate related to the cutting feed acceleration of the tool, and the calculated variation rate is a limit acceleration variation rate stored in the limit acceleration variation rate storage unit. And an NC program correction processing unit that corrects the corresponding cutting feed rate so as to be equal to or less than the limit acceleration fluctuation rate when the limit acceleration fluctuation rate is exceeded. NC program modification device.   When it is determined that the acceleration fluctuation rate of the cutting feed rate between the two command blocks exceeds the limit acceleration fluctuation rate, the NC program correction processing unit determines that at least one of the two command blocks is a plurality of command blocks. And the cutting feed speed of the new command block corresponding to the two command blocks is set to a cutting feed speed at which the acceleration fluctuation rate between the blocks is equal to or less than the limit acceleration fluctuation rate. The NC program correcting device according to claim 1, wherein:   When it is determined that the acceleration fluctuation rate of the cutting feed speed between the two command blocks exceeds the limit acceleration fluctuation rate, the NC program correction processing unit calculates the cutting feed speed in at least one of the two command blocks. 3. The NC program correcting device according to claim 1, wherein the NC program correcting device is defined as a non-stationary rational spline function. The NC program correcting device according to any one of claims 1 to 4,
A shape data storage unit for storing shape data relating to the three-dimensional shape of the workpiece;
Information related to the cutting speed and cutting amount according to the material material, as well as a tool / machining information storage unit storing tool information;
An NC program is generated based on the three-dimensional shape data of the workpiece stored in the shape data storage unit and information stored in the tool / machining information storage unit, and the generated NC program is stored in the NC program storage An NC program generation apparatus comprising an NC program generation processing unit stored in the unit.

Images