Postprocessor device, machine program production process, CNC machining system and program for machine program production

Abstract

Postprocessor device (22) outputting a machining program for controlling a CNC machine tool (30), comprising: a characteristic shape recognition unit (222) for reading information about a characteristic shape to be machined from CL data (Cutter Location data) containing information about a characteristic shape, a section setting unit (223) for setting one or more set sections on a toolpath in response to the information about the characteristic shape, and a motion generation unit (224, 225) for generating a machining program containing a command to change at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set section and inside the set section, wherein the information about a characteristic shape to be machined is inserted into the CL data as comments in the form of tagged text.

Description

BACKGROUND OF THE INVENTIONField of the InventionThe present invention relates to a postprocessor apparatus, a machine program generation method, a CNC machining system, and a program for machine program generation.Prior ArtAccurate machining of a characteristic shape such as an edge or smooth surface is important during machining and particularly during punching. Here, a desired machining system needs to perform a machining process corresponding to a characteristic shape such as an edge or a smooth surface by integrating information on this characteristic shape into, for example, CL data (cutter location data) or NC data (numerical control data). However, a conventional G code in a machining program does difficult to determine from a tool path whether a workpiece is a smooth surface or an edge.For example, Patent Documents 1 and 2 disclose machining program generators that generate a machining program in consideration of the shape of a workpiece. Patent Document 1 describes a curve extractor and an NC programming system with which complicated work such as reading drawing information, calculating coordinates, inputting a numerical value during generation of an NC program does not need to be performed, and errors are reduced. Specifically, the curve extractor extracts curve data (closed loop data, open loop data, hole group data, groove center shape data, etc.) from drawing data generated by, for example, a CAD system. The NC programming system includes a CAM device that generates an NC program by inputting drawing data generated by, for example, the CAD system into the curve extractor and receiving the curve data generated by the curve extractor.Patent Document 2 describes a machining control device that allows machining even by an operator with little experience and prevents repetition of like errors. Specifically, the machining control device allows machining under a corresponding machining condition by searching for a machining case in response to a characteristic of a shape to be machined and setting a machining condition based on the searched machining case.Patent Document 1: JP H04-76 606 APatent Document 2: JP 2004-284 002 ASUMMARY OF THE INVENTIONThe curve extractor and the NC programming system of Patent Document 1 obtain machining area shape data by graphically displaying the drawing data generated by the CAD system, for example, causing an operator to indicate an edge in the drawing, and extracting a closed loop, an open loop, a hole group, or the shape of a groove center using the specified edge. Thus, according to Patent Document 1, no machining process is performed in response to a characteristic shape such as an edge or a smooth surface by integrating this characteristic shape into, for example, CL data or NC data. The machining control device described in Patent Document 2 searches for a machining case from the past in response to a characteristic of a shape to be machined, and sets a machining condition based on the searched machining case. Thus, according to Patent Document 2, no machining process is performed in response to a characteristic shape such as an edge or a smooth surface by integrating this characteristic shape into, for example, CL data or NC data.The present invention aims to provide a postprocessor apparatus, a machining program generation method, a CNC machining system, and a machining program generation program for reading information on a characteristic shape such as an edge or a smooth surface into, for example, CL data for generating a machining program suitable for a machining process for the characteristic shape by integrating the information on the characteristic shape into the CL data.(1) A postprocessor device according to the present invention (for example, postprocessor 22 described below) outputs a machining program for controlling a CNC machine tool (for example, the CNC generation machine described below). The postprocessor device includes: a characteristic shape recognition unit (for example, characteristic shape recognition unit 222) to read information on a characteristic shape to be processed from CL data (cutter location data) including information on a characteristic shape; a section setting unit (for example, section setting unit 223 described below) to set one or more set sections on a tool path in response to the information on the characteristic shape; and a motion generation unit (for example, the below-described inside-section motion generation unit 224 and the below-described outside-section motion generation unit 225) for generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set section and inside the set section.(2) The postprocessor device of (1) may further include: a data reading unit (for example, the data reading unit 221 described below) for reading the CL data including the information on the characteristic shape; and a machining program output unit (for example, the machining program output unit 226 described below) for outputting the machining program.(3) In the postprocessor device of (1) or (2), the parameter may include at least one of the following parameter sets (A), (B), and (C): (A) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration / deceleration control for a feed axis; (B) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration / deceleration control for a spindle; and (C) an allowable error amount between a commanded path and an actual path.(4) In the postprocessor device of (1) to (3), the characteristic shape information may include at least one of the following information sets (a) and (b): (a) information on a portion where a tool contacts an edge of a workpiece on a tool path, and (b) information on a portion where a tool path is a smooth curve on the tool path.(5) In the postprocessor device of (1) to (4), the parameter may include a feed speed of a feed axis and a spindle speed, and the motion generation unit may generate the machining program including a command for changing the spindle speed in synchronization with a change in the feed speed of the feed axis.(6) In the postprocessor apparatus of (1) to (5), the CL data may be a general-purpose command that is independent of a machine and includes information on the geometry of a workpiece or a tool path and information on the machining content, the information being described in a format corresponding to a data model having a hierarchical structure.(7) A CNC machining system according to the present invention includes the postprocessor device (for example, postprocessor 22 described below) of (1) to (6) and a CNC machine tool (for example, CNC machine tool 30 described below) for CNC machining on a workpiece based on a machining program generated by the postprocessor device.(8) A machining program generation method according to the present invention is implemented by a postprocessor device (for example, postprocessor 22 described below) that outputs a machining program for controlling a CNC machine tool (for example, the CNC machine tool described below), and includes: a step of reading information on a characteristic shape to be machined from CL data (cutter location data) including information on a characteristic shape; a step of setting one or more set portions on a tool path in response to the information on the characteristic shape; and a step of generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set portion and inside the set portion.(9) A program for machining program generation according to the present invention causes a computer to function as a postprocessor device (for example, postprocessor 22 described below) that outputs a machining program for controlling a CNC machine tool (for example, CNC machine tool 30 described below) to perform: a process of reading information on a machined characteristic shape from CL data (cutter location data) including information on a characteristic shape; a process of setting one or more set portions on a tool path in response to the information on the characteristic shape; and a process for generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set portion and inside the set portion.The present invention provides a postprocessor device, a machining program generation method, a CNC machining system, and a storage medium having computer readable information for reading information on a characteristic shape such as an edge or a smooth surface into, for example, CL data for generating a machining program suitable for a machining process of the characteristic shape by integrating the information on the characteristic shape into the CL data.BRIEF DESCRIPTION OF THE DRAWINGSFIG. 1 is a block diagram showing an exemplary configuration of a CNC machining system according to an embodiment of the present invention. Fig. 2 is a block diagram showing the configuration of a computer with respect to a postprocessor. Figure 3 is a block diagram showing the operation of the postprocessor. FIG. 4 is a configuration view showing an example of a data model based on ISO 14649. FIG. 5 is an explanatory view showing an example of using information on an edge portion as characteristic portion information. FIG. 6 shows characteristics of a relationship between a commanded speed and an actual speed determined by changing a feed speed. FIG. 7 shows a path radius r and a path error Δr. FIG. 8 is an explanatory view showing an example of using information on a smoothing section as characteristic section information. Fig. 9 shows the density of cutting tracks at a constant feed speed and a constant spindle speed. Fig. 10 shows the density of cutting tracks with a lower feed speed and a constant spindle speed. Fig. 11 shows the density of cutting tracks with changes in the feed speed and the spindle speed. Figure 12 is a flow chart showing the movement of the postprocessor.DETAILED DESCRIPTION OF THE INVENTIONHereinafter, an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an exemplary configuration of a CNC machining system according to the embodiment of the present invention. As shown in FIG. 1, the computerized numerical control (CNC) machining system includes a CAD (computer aided design) device 10, a CAM (computer aided manufacturing) device 20, and a CNC machine tool 30.The CAD device 10 executes CAD software for designing on a screen of a computer using a CPU. A outline of a workpiece (workpiece) is drawn using a two-dimensional CAD or a three-dimensional CAD. When a two-dimensional CAD is used, the CAD device 10 draws a front view, a top view, a side view, etc. of the workpiece in an XY plane. When a three-dimensional CAD is used, the CAD device 10 draws a three-dimensional image of the workpiece in an XYZ three-dimensional space.The CAM device 20 includes a main processor 21 and a post processor 22, and the CAM device 20 executes CAM software for generating a machining program (NC data) based on the shape of the workpiece generated by the CAD device 10 using the CPU of the computer. The CAM software is configured using main processor software that causes the CAM device 20 to operate as the main processor 21 and post processor software that causes the CAM device 20 to operate as the post processor 22. The main processor software and the post processor software are run on the same computer or on different computers. The main processor 21 sets the movement of a tool or a machine tool to obtain a geometry based on CAD data, and converts the set movement to CL data (cutter location data). The postprocessor 22 generates a machining program (NC data) based on the CL data generated by the main processor 21. The configuration of the postprocessor 22 will be explained in detail below.The CNC machine tool 30 includes a numerical controller 310, a servo controller 320, a spindle motor 330, and a feed axis motor 340. The CNC machine tool 30 is, for example, a 3-axis machine tool. In FIG. 1, only the spindle motor 330 and the feed axis motor 340 are shown as units of the 3-axis machine tool responsible for machining. The spindle motor 330 rotates a tool such as a ball mill. The feed axis motor 340 includes three motors: an X-axis direction motor, a Y-axis direction motor, and a Z-axis direction motor. The X-axis direction motor and the Y-axis direction motor linearly move a table in the X-axis direction and the Y-axis direction, respectively, by a ball screw, for example, with a substrate for forming a workpiece placed on the table. The motor for the Z-axis direction linearly moves the tool or the table in the Z-axis direction. However, the configuration of the 3-axis machine tool is not limited to that described herein. The 3-axis machine tool may also be configured to move the table linearly in the X-axis direction, the Y-axis direction, and the Z-axis direction while the tool is fixed, or may be configured to move the tool linearly in the X-axis direction, the Y-axis direction, and the Z-axis direction while the table is fixed. The CNC machine tool 30 is not limited to a 3-axis machine tool, and may also be, for example, a 5-axis machine tool.The numerical controller 310 includes a command output unit 311 and a program analysis unit 312. The program analysis unit 312 sequentially reads blocks each including respective movement commands for the spindle, the X-axis, the Y-axis, and the Z-axis and a rotation command for the spindle from the machining program (NC data) generated by the post processor 22 of the CAM 20, analyzes the read blocks, generates command data including respective movement commands for the spindle, the X-axis, the Y-axis, and the Z-axis and the rotation command for the spindle, and outputs the generated command data to the command output unit 311.The command output unit 311 calculates a speed for each axis based on the command data output from the program analysis unit 312, and outputs data based on a calculation result to a spindle motor servo control unit 321 in the servo controller 320 and three feed axis motor servo control units 322 for the X axis, the Y axis, and the Z axis in the servo controller 320.The spindle motor servo control unit 321 controls the spindle motor 330 based on the output from the command output unit 311. The three feed axis motor servo control units 322 for the X axis, the Y axis, and the Z axis control corresponding ones of the three feed axis motors 340 for the X axis, the Y axis, and the Z axis based on the output from the command output unit 311. The spindle motor servo control unit 321 and the three feed axis motor servo control units 322 each include a position control unit and a speed control unit for forming a position locked loop and a speed locked loop, a motor drive amplifier for driving a spindle motor or a feed axis motor based on a torque command value, an operation panel for accepting an operation from a user, etc.The spindle motor servo control unit 321 calculates a backlash compensation value using a position feedback signal from a position detector such as an encoder connected to the spindle motor 330 and a position command output from the numerical controller 310, and compensates the position command. The three feed axis motor servo control units 322 each calculate a backlash compensation value using a position feedback signal from a position detector such as an encoder coupled to a corresponding one of the three feed axis motors 340 and a position command output from the numerical controller 310, and compensates the position command. The internal configuration of the spindle motor servo control unit 321 and the three feed axis motor servo control units 322 are well known to those skilled in the art, so they will not be described in detail here and will not be shown in detail in the drawings.In the above-described CNC machining system, the CAD device 10 and the CAM device 20 may be integrated and configured in a computer. Alternatively, the CAD device 10 and the CAM device 20 may be integrated with the numerical controller 310. Further, the servo controller 320 may be integrated in the numerical controller 310.< Processor 22>Next, the postprocessor 22 will be described. Fig. 2 shows the configuration of a computer 23 operated as the postprocessor 22. As shown in FIG. 2, the computer 23 constituting the post processor 22 includes at least a CPU 231, an input / output unit 232, a first storage unit 233, a second storage unit 234, and a display unit 235. The CPU 231, the input / output unit 232, the first storage unit 233, the second storage unit 234, and the display unit 235 are connected to each other via a bus.The CPU 231 is configured using, for example, a microprocessor including a CPU, a RAM, a ROM, an I / O interface, etc. The CPU 231 executes a program read from the first storage unit 233 such as a hard disk drive or a ROM. For the execution of the program, the CPU 231 receives, for example, CL data via the input / output unit 232, reads information from the first storage unit 233 or the second storage unit 234, such as a RAM, and writes information resulting from the operation into the first storage unit 233 or the second storage unit 234. The CPU 231 sends and receives signals to and from the display unit 235 and the input / output unit 232, and displays the content of the processing on the display unit 235, for example.Specifically, the CPU 231 executes programs of postprocessor software (these programs are also collectively referred to as "postprocessor application") for causing the computer 23 to function as the postprocessor 22. The CPU 231 executes a program for causing the computer 23 to follow predetermined procedures (hereinafter collectively referred to as "machining program generation procedure").A function associated with the CPU 231 will be described below from the perspective of the postprocessor 22. A function belonging to the CPU 231 from the perspective of the machining program generation procedure (method) to be followed by the postprocessor 22 will not be described herein because it can be understood by replacing a "unit" with a "procedure".Figure 3 is a block diagram showing the operation of the postprocessor 22 according to the present invention. As shown in FIG. 3, the postprocessor 22 includes a data reading unit 221, a characteristic shape recognition unit 222, a section setting unit 223, an inside-section motion generation unit 224, an outside-section motion generation unit 225, and a machining program output unit 226. Before a description is given below of the functional units of the postprocessor 22, CL data to be input to the postprocessor 22 will be described.<CL Data>For example, CL data to be input to the postprocessor 22 is configured to include information on a characteristic shape such as an edge or a smooth surface. Specifically, the CL data may include pieces of information from information Inf 1 to information Inf 5 as follows:(Inf1) information on a tool path,(Inf2) information on a characteristic shape on a tool path,(Inf3) information on a tool used for machining,(Inf4) information on a machining condition, and(Inf5) Information on the order of processing.The information Inf 1 (=displays on a tool path) includes information on a tool path, etc. (the CL data itself) resulting from, for example, offsetting a tool shape corresponding to the contour shape of a workpiece. The information Inf 2 (=displays on a characteristic shape on a tool path) includes characteristic portion information that describes a characteristic in a specific portion of a tool path. The characteristic portion information includes, for example, information on an edge portion in which a tool contacts an edge of a workpiece on a tool path or information on a smoothing portion in which a tool path is a smooth curve on the tool path. The information Inf 3 (=displays of a tool used for machining) includes, for example, information on the type, dimension, etc. of a tool. The information Inf 4 (=formity of a machining condition) includes, for example, information on a feed speed on a tool path, a spindle speed on the tool path, or use of a cutting fluid. The information Inf 5 (=work order information) includes information on the order in which work steps are performed. The information Inf2 and the information Inf4 are particularly important for the processing by the postprocessor 22.A data model for the CL data with the above-mentioned pieces of information has a hierarchical structure such as that according to ISO 14649. As long as the hierarchical structure of the data model for the CL data has a format allowing a corresponding description of required information, another structure may be used as the ISO 14649. FIG. 4 is a configuration view showing the hierarchical structure of a data model based on ISO 14649. The information Inf2 (=identifies about a characteristic shape on a tool path) is not included in the hierarchical structure of the data model based on ISO 14649, so that it is preliminarily set as a "characteristic shape" corresponding to structure data subordinate to a "tool path" in this hierarchical structure of the data model. With reference to the hierarchical structure of the data model shown in FIG. 4, the information Inf1 (= information on a tool path) may be described in "geometry" and "tool path", the information Inf2 (= information on a characteristic shape on a tool path) may be described in "characteristic shape", the information Inf3 (= information on a tool used for machining) may be described in "tool used", the information Inf4 (= information on a machining condition) may be described in "machining condition", and the information Inf5 (= information on the order of machining) may be described in "step list", for example. In this way, the CL data including the pieces of information from the information Inf 1 to the information Inf 5 can be described as information having a structure defined based on the data model. For example, the pieces of information from the information Inf 1 to the information Inf 5 may be inserted into the CL data as annotations in the form of information in tagged text (e.g., XML). The information contained in the CL data and to be inserted into the postprocessor 22 is constituted as described above. The functional units of the postprocessor 22 will be described below.The data reading unit 221 reads CL data generated by the main processor 21 and includes, for example, the information Inf 1 (= information on a tool path), the information Inf 2 (= information on a characteristic shape on a tool path), the information Inf 3 (= information on a tool used for machining), the information Inf 4 (= information on a machining condition), and / or the information Inf 5 (= information on the order of machining).The characteristic shape recognition unit 222 acquires all information Inf 2 (=displaying a characteristic shape on a tool path) included in the CL data in each machining step. For example, when the characteristic shape recognition unit 222 recognizes that the information Inf 2 is an edge portion, the characteristic shape recognition unit 222 obtains a start point of the edge portion and an end point of the edge portion, and obtains information on a machining condition for the information Inf 4 such as a feed speed on a tool path including this edge portion or a spindle speed on the tool path. For example, when the characteristic shape recognition unit 222 recognizes that the information Inf 2 on a smoothing portion in which the tool path is a smooth curve is on a tool path, the characteristic shape recognition unit 222 acquires information on a tool path given as a continuous straight line and information on a smoothing portion in which a shape is smoothed on the tool path. The smoothing portion information may include information on a start point and an end point of the smoothing portion, and a change rate of a tool direction (indicating the change degree of a movement direction of a tool while the tool is moving over a constant distance) allowable in the smoothing portion.The section setting unit 223 sets a constant section on a tool path for each information Inf 2 (=displaying the characteristic shape on a tool path) acquired by the characteristic shape recognition unit 222 based on characteristic shape information in the information Inf 2.Specifically, when the information acquired by the characteristic shape recognition unit 222 is Inf 2 about an edge portion in which a tool contacts an edge of a workpiece on a tool path, the portion setting unit 223 automatically sets a low-speed portion on the tool path including the edge portion. For example, as shown in FIG. 5, a start point and an end point of the low-speed portion are set such that the low-speed portion becomes larger than the edge portion. The range of the low-speed portion may be previously determined or may be calculated in response to a machining condition. The processing for setting the low speed section will be described in detail later.When the section setting unit 223 recognizes that the information Inf 2 acquired by the characteristic shape recognition unit 222 is a smoothing section, the section setting unit 223 sets a smoothing section on a tool path based on the smoothing section information. Specifically, the section setting unit 223 sets a smoothing section on a tool path based on the given smoothing section information. The smoothing section set by the section setting unit 223 is a section set on a tool path based on the previous smoothing section information. For example, a start point and an end point shown in FIG. 8 match corresponding points described in the smoothing section information. The section setting unit 223 generates a new tool path closest to a tool path represented by a broken line while setting a change rate of a tool direction to a value not higher than a tolerance in the smoothing section. The section setting unit 223 may generate a tool path having a higher-order continuity (generally referred to as a continuity G 2 or a continuity G 3) by further setting a tolerance for a change rate of a moving direction.The section setting unit 223 can increase smoothness of a curve by setting a speed or a maximum acceleration in a smoothing section. Many CNC machine tools generally have a function of selecting a movement mode for a tool between a first machining mode faithfully executing a command and a second machining mode giving priority to smoothness. The first machining mode is a machining mode in which, when a tool path in an NC command is represented by a broken line, the processing proceeds to follow the broken line tru. The second machining mode is a machining mode in which, when a tool path in an NC command is given by a broken line, the tool path is smoothed and machining smoothly proceeds. There is also a CNC machine tool that can select the first machining mode or the second machining mode in stages depending on the degree of smoothing of a tool path. A maximum allowable acceleration / deceleration of a motor is different in the first machining mode and the second machining mode. A machine is operated at a higher allowable acceleration / deceleration for the command. The first machining mode or the second machining mode is generally selected before machining. When information on a smoothing section is described in the information Inf 2 (=displays on a characteristic shape on a tool path), the information on the smoothing section may be specified such that a mode is automatically changed between the inside and the outside of the smoothing section, for example, such that the machining in the first machining mode proceeds tru to a command outside the smoothing section and the machining in the second machining mode that gives priority to the smoothness proceeds in the smoothing section. In this case, as for a parameter for a machining program (NC data) to be generated by the postprocessor 22, a maximum allowable acceleration deceleration for a motor is changed between inside and outside the smoothing section. The information on the smoothing section may also be specified such that the first machining mode or the second machining mode corresponding to the degree of smoothing is selected in the smoothing section. The processing for setting the smoothing section will be described in detail later.The in-section motion generation unit 224 generates a part of a machining program (NC data) to be generated by the postprocessor 22 and to be used for controlling a motion in a constant section on a tool path set by the section setting unit 223. The section setting unit 223 sets the constant section on the tool path based on the characteristic shape information in all the information Inf 2 (=displays on the characteristic shape on a tool path) in the CL data. The processing for generating the part of the machining program (NC data) to be used for controlling the movement in the section will be described later.The out-of-section motion generation unit 225 generates a part of the machining program to be used for controlling the motion outside the set section. For example, when the set portion is an edge portion, the out-of-portion motion generation unit 225 calculates a speed command in the machining program (NC data) for setting a feed speed again to a feed speed F 1 out of the portion after passing through a low-speed portion. The out-of-section motion generation unit 225 may be omitted, and the in-section motion generation unit 224 may calculate a speed command in the machining program (NC data) for setting a feed speed again to the feed speed F 1 after passing through the low-speed section. For example, when the set portion is a smoothing portion, the out-of-portion motion generation unit 225 may be omitted, and the in-portion motion generation unit 224 may calculate a speed command in the machining program (NC data) for making a change to the previous first machining mode after passing through the smoothing portion.The inside-section motion generation unit 224 and the outside-section motion generation unit 225 each generate a parameter for a part of a machining program (NC data) to be used for controlling a motion in a constant section on a tool path and a parameter for a part of the machining program (NC data) to be used for controlling a motion outside the section. The generated parameters are, for example, parameters in one, two or more of the following parameter sets (1), (2), and (3): (1) a speed command, an allowable acceleration, an allowable jerk, and an acceleration / deceleration control-related time constant for a feed axis, (2) a speed command, an allowable acceleration, an allowable jerk, and an acceleration / deceleration control-related time constant for a spindle, and (3) an error amount allowable between a commanded path and an actual path.The machining program output unit 226 generates a machining program (NC data) by combining two parts including the part of the machining program (NC data) to be used for controlling the movement in the section generated by the inside-section movement generation unit 224 and the part of the machining program (NC data) to be used for controlling the movement outside the section used by the outside-section movement generation unit 225, and outputs the generated machining program (NC data). The machining program (NC data) thus generated is input to the CND machine tool 30 (numerical controller 310). The CNC machine tool 30 (the numerical controller 310) may perform a machining process in an edge portion and / or a smoothing portion based on the NC data, for example.[First Example of Using Characteristic Portion Information: Information on Edge Portion]Hereinafter, an example of characteristic portion information will be explained by describing processing related to an edge portion by the portion setting unit 223 and the inside-of-portion motion generation unit 224 in detail with reference to FIG. 5. In this use example, the CL data includes the information Inf 2 describing information on an edge portion and the information Inf 4 describing information on machining conditions such as a feed speed on a tool path including the edge portion and a spindle speed on the tool path, etc.The section setting unit 223 automatically sets a low-speed section on the tool path including the edge section. As shown in FIG. 5, a start point and an end point of the low-speed portion are set such that the low-speed portion becomes larger than the edge portion. The range of the low-speed portion may be determined in advance or may be calculated in response to the machining conditions.The reason why the low-speed portion is set larger than the edge portion will be explained below. In a machine tool, when a speed command changes steeply, a load generally acts on a motor, causing the motor to rattle. Therefore, in the machine tool, a change in a speed command in a machining program (NC data) is controlled such that the actual feed speed changes smoother (smoother) than the speed in the speed command. That is, the speed command is calculated such that a feed speed F 2 suitable for edge processing in the edge portion is set by starting a speed reduction just before the edge portion to finish deceleration before entering the edge portion and starting acceleration after passing through the edge portion.FIG. 6 shows exemplary characteristics of a relationship determined by switching a commanded speed in a speed command between the change in the commanded speed described in a machining program (NC data) and an actual speed change controlled to be smoother (smoother) than the change in the commanded speed in a machine tool. The solid line represents the change in the commanded speed described in the machining program (NC data). The broken line indicates the actual speed change controlled to be smoother (smoother) than the change in the commanded speed in the machine tool. In this example, when it is assumed that T is a time constant, for example, an actual speed of a tool at a given time t corresponds to the average of a commanded speed at the time (t-time constant T) and a commanded speed at the time (t+time constant T) as shown in FIG. 6. By giving a command immediately before a start point of an edge portion for setting a feed rate in the edge portion in F 2, the tool is made to enter the edge portion while the deceleration of the tool is not yet completed. As for an end point of the edge portion, by giving a command for starting acceleration at the end point of the edge portion, the tool is actually accelerated before the tool exits from the edge portion. In order to avoid the occurrence of such a situation, the section setting unit 223 sets a point before the start point of the edge section, which is separated from the start point of the edge section by a distance corresponding to the time constant T (almost F 2×T), as a start point of a low-speed section. Further, the section setting unit 223 sets a point before the end point of the edge section, which is spaced from the end point of the edge section by F 2×T, as an end point of the low-speed section. In order to calculate the feed speed F 2 in the edge portion on a demand basis, the portion setting unit 223 calculates a value F 2×T also on a demand basis. When the feed speed F 2 in the edge portion is a predetermined value, F 2×T may be given beforehand in the information Inf 4 (= information on a machining condition).The in-section motion generation unit 224 compares the commanded feed speed F 1 on a tool path with the feed speed F 2 suitable for edge processing. When the feed speed F 1 is higher than the feed speed F 2, the in-section movement generation unit 224 describes a speed command in a machining program (NC data) such that the feed speed F 3 does not exceed in the low-speed section F 2. The feed speed F 2 may have a predetermined value or a value calculated based on a tool diameter or an edge angle.FIG. 7 shows a path radius r and a path error Δr. The path radius r coincides with a tool diameter. The path error (a difference between a commanded path and an actual path) Δr is the dimension of corner descent allowed for an edge. An acceleration / deceleration time constant T of an engine is a value depending on the setting of the engine. As a curve in a tool path becomes steeper and the allowable error becomes smaller, the feed speed needs to be lower. The feed speed F 2 at which corner lowering does not exceed a tolerance is determined by, for example, calculating a value satisfying the relationship of Equation 1. As is apparent from Equation 1, the feed speed F2 must be lower with a smaller tool diameter and a smaller permissible corner drop. The feed speed F 2 may be registered in advance by determining it based on a tool having the smallest expected diameter and the smallest tolerance for corner lowering during machining by a machine using this tool. r Path radius Δr Acceleration / deceleration time constant of the machineAs described above, the out-of-section motion generation unit 225 describes a speed command in a machining program for setting a feed speed again to the feed speed F 1 after passing through a low-speed section. The out-of-section motion generation unit 225 may be omitted, and the in-section motion generation unit 224 may describe a speed command in the machining program for setting a feed speed again to the feed speed F 1 after passing through the low-speed section.As described above, information on a characteristic shape such as an edge portion is integrated into the information Inf 2 (=displays on a characteristic shape on a tool path) in CL data to be input to the postprocessor 22, and information on a machining condition such as a feed speed on a tool path including this edge portion or a spindle speed on the tool path is integrated into the information Inf 4 (=displays on a machining condition) in the CL data. In this way, the postprocessor 22 can generate a machining program (NC data) used for performing a machining process in the edge portion in accordance with the information Inf 2 (=identifies about a characteristic shape on a tool path) and the information Inf 4 (=identifies about a machining condition). This achieves processing of a mold that cannot be easily processed using a conventional G code.[Second Example of Using Characteristic Portion Information: Information on Smoothing Portion]Hereinafter, an example of characteristic portion information will be explained by describing processing related to a smoothing portion by the portion setting unit 223 and the in-portion motion generating unit 224 in detail with reference to FIG. 8. In this use example, the CL data includes the information Inf 2 describing information on a smoothing section.The section setting section 223 sets a smoothing section on a tool path based on given smoothing section information. As described above, the smoothing section information is information described in CL data including information on a start point and an end point in the smoothing section, and an allowable change rate of a tool direction (indicating the change degree of a moving direction of a tool while the tool moves over a constant distance). The section setting unit 223 sets the smoothing section as a section set on a tool path based on the smoothing section information. The start point and the end point shown in FIG. 8 match corresponding points described in the smoothing section information. The section setting unit 223 generates a new tool path closest to a tool path represented by a broken line while setting a change rate of a tool direction to a value not exceeding a tolerance in the smoothing direction. The section setting unit 223 may generate a tool path having a high-order continuity (generally referred to as G2 continuity or G3 continuity) by further setting a tolerance for a change rate of a moving direction.The in-section motion generation unit 224 replaces an input tool path with a tool path along which line segments are smoothly connected in the smoothing section such that the change dimension in the moving direction for a moving distance of a tool set by the section setting unit 223 does not exceed a tolerance. The tolerance may be set in advance or may be described in the smoothing section information, for example. As described above, the out-of-section motion generation unit 225 is not used in this use example. The in-section motion generation unit 224 generates a machining program using the tool path replacing the path in the smoothing section. As described above, the smoothing section information is integrated into the information Inf 2 (=display of a characteristic shape on a tool path) in CL data to be input to the postprocessor 22. In this way, the postprocessor 22 can generate a machining program (NC data) used for performing a machining process in the smoothing section in accordance with the information Inf 2 (=identifies about a characteristic shape on a tool path). This achieves machining of a mold that cannot be easily machined by a conventional G code.[Third Example of Use in Control of Spindle Speed in Synchronization with Feed Speed]An example of use in controlling the spindle speed in synchronization with a feed rate will be described below. This use example can be further applied to the foregoing first use example and the second use example. When the in-section motion generation unit 224 changes a feed speed, the in-section motion generation unit 224 preferably changes a spindle rotation speed together with the feed speed. For example, as shown in FIG. 9, when a feed speed and a spindle speed have constant values, cutting tracks having a constant density are left. A cutting track is understood here to mean a path of a tool blade left on a machining surface. On the other hand, when the feed speed becomes lower while the spindle speed is maintained at the constant value, the density of the cutting tracks changes as shown in Fig. 10 to change the characteristics and appearance of the machining surface. In order to change the feed speed to F 2 (<F 1) in preparation for a process such as a process in an edge portion on a tool path along which the feed speed F 1 and the spindle speed S 1 are specified, the in-portion movement generation unit 224 preferably changes the spindle rotation speed to a speed S 2 (<S 1) different from the speed S 1 where necessary. In this case, when the in-section motion generation unit 224 sets the spindle speed S 2 such that S 2=S 1×(F 2 / F 1) is satisfied, the density of the cutting tracks can be maintained at a constant value to achieve a uniform machining area as shown in FIG. 11.The configuration of the postprocessor 22 has been described above. The movement of the postprocessor 22 will be described below. Figure 12 is a flow chart showing the movement of the postprocessor 22.In step S 101, the data reading unit 221 reads CL data generated by, for example, the main processor 21 and includes characteristic shape information. In step S 102, the characteristic shape recognition unit 222 determines whether the CL data includes characteristic shape information. For example, the characteristic shape recognition unit 222 determines the presence of the characteristic shape information with reference to the processing path of FIG. 4. If the CL data does not contain characteristic shape information, the flow proceeds to step S106. In step S 103, the characteristic shape recognition unit 222 recognizes the characteristic shape information in the CL data. In step S 104, the section setting unit 223 sets a constant section on a tool path based on the characteristic shape information recognized by the characteristic shape recognition unit 222 in step S 103. In step S 105, the in-section motion generation unit 224 generates a part of a machining program (NC data) to be used for controlling a motion in a set section. The out-of-section motion generation unit 225 generates a part of the machining program to be used for controlling motion outside the set section. The inside-section motion generation unit 224 and the outside-section motion generation unit 225 generate corresponding parameters for the machining program. The generated parameters are, for example, parameters in one, two, or more of the following parameter sets (1), (2), and (3): (1) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration deceleration control for a feed axis; (2) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration / deceleration control for a spindle; and (3) an allowable error amount between a commanded path and an actual path.In step S 105, the machining program output unit 226 further combines two parts, namely, the part generated by the inside-section motion generation unit 224 to be used for controlling the motion in the set section and the part generated by the outside-section motion generation unit 225 to be used for controlling the motion outside the set section. Then, the flow goes to step S102. When it is determined in step S 102 that the CL data does not include new characteristic shape information, the flow proceeds to step S 106. In step S 106, the machining program output unit 226 generates and outputs a machining program (NC data).In the above-described embodiment of the present invention, the function of the postprocessor 22 can be fully or partially realized by software. However, the function of the postprocessor 22 can also be realized by hardware or by a combination of software and hardware. A realization by software is understood to mean a reading out and execution of a program by a computer. The postprocessor 22 can be configured by hardware by configuring the data reading unit 221, the characteristic shape recognition unit 222, the section setting unit 223, the inside-section motion generation unit 224, the outside-section motion generation unit 225, and / or the machining program output unit 226 of the postprocessor 22 using, for example, an integrated circuit (IC) such as a highly integrated circuit (LSI), an application specific integrated circuit (ASIC), a gate array, or a field programmable gate array (FPGA).To configure the postprocessor 22 by software, a postprocessor application that describes a motion such as that shown in FIG. 12 for an operation of the postprocessor 22 is stored in the first storage unit such as a hard disk drive or a ROM. The CPU stores information necessary for operation in the second storage unit such as a RAM, and performs processing by following the postprocessor application, thereby realizing movement of the postprocessor 22 according to a program. The postprocessor application can be read from a computer readable information storage medium storing the program into the first storage unit such as a hard disk. The computer readable information storage medium includes various types of tangible storage media. The computer readable information storage medium is a non-transitory computer readable information storage medium. Examples of the computer readable information storage medium include a magnetic storage medium (for example, a flexible disk or a hard disk drive), a magneto-optical storage medium (for example, a magneto-optical disk), a CD-ROM (CD-ROM), CD-R, CD-R / W, and a semiconductor memory (for example, a mask ROM, a programmable ROM (PROM), an erasable PROM (EPROM), a flash ROM, or a random access memory (RAM)).LIST OF REFERENCE NUMERALS10 CAD device 20 CAM device 21 main processor 22 post processor 30 CNC machine tool 310 numerical control device 320 servo control device 330 spindle motor 340 feed axis motor

Claims

A postprocessor device (22) that outputs a machining program for controlling a CNC machine tool (30), comprising: a characteristic shape recognition unit (222) for reading information on a characteristic shape to be machined from CL (Cutter Location) data including information on a characteristic shape; a section setting unit (223) for setting one or more set sections on a tool path in response to the information on the characteristic shape; and a motion generation unit (224, 225) for generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set section and inside the set section, wherein the information on a characteristic form to be edited is inserted into the CL data as comments in the form of tagged text.The postprocessor apparatus according to claim 1, further comprising: a data reading unit (221) for reading the CL data including the information on the characteristic shape; and a machining program output unit (226) for outputting the machining program.The postprocessor apparatus according to claim 1 or 2, wherein the parameter includes at least one of the following parameter sets (A), (B), and (C): (A) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration / deceleration control for a feed axis, (B) a speed command, an allowable acceleration, an allowable jerk, and a time constant related to acceleration / deceleration control for a spindle, and (C) an allowable error amount between a commanded path and an actual path.The postprocessor apparatus according to any one of claims 1 to 3, wherein the characteristic shape information includes at least one of the following information sets (a) and (b): (a) information on a portion where a tool contacts an edge of a workpiece on a tool path, and (b) information on a portion where a tool path is a smooth curve on the tool path.The postprocessor apparatus according to any one of claims 1 to 4, wherein the parameter includes a feed speed of a feed axis and a spindle speed, and the motion generation unit generates the machining program including a command for changing the spindle speed in synchronization with a change in the feed speed of the feed axis.The postprocessor apparatus according to any one of claims 1 to 5, wherein the CL data includes information on the geometry of a workpiece or a tool path and information on the machining content, the information being described in a format corresponding to a data model having a hierarchical structure.A CNC machining system comprising the postprocessor device (22) according to any one of claims 1 to 6, and a CNC machine tool (30) for CNC machining on a workpiece based on a machining program generated by the postprocessor device.A machining program generation method implemented by a postprocessor device (22) that outputs a machining program for controlling a CNC machine tool (30), and includes: a step of reading information on a characteristic shape to be machined from CL (cutter location) data including information on a characteristic shape; a step of setting one or more set portions on a tool path in response to the information on the characteristic shape; and a step of generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set portion and inside the set portion, wherein the information on a characteristic form to be edited is inserted into the CL data as comments in the form of tagged text.A program for machining program generation that causes a computer to function as a postprocessor device (22) that outputs a machining program for controlling a CNC machine tool (30) to perform: a process of reading information on a machining characteristic shape from CL data (cutter location data) including information on a characteristic shape, a process of setting one or more set portions on a tool path in response to the information on the characteristic shape, and a process of generating a machining program including a command for changing at least one parameter to be used for controlling at least one axis of the CNC machine tool outside the set portion and inside the set portion, wherein the information on a characteristic form to be edited is inserted into the CL datat as comments in the form of tagged text.

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