JP2008036804A - Rapid feed control method of machine tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To improve machining efficiency of work by speeding up a rapid feed speed without lowering machining accuracy of finish cutting at the time of working on the work accompanied by finish cutting in a machine tool with a plurality of tool rests, the movement of which is controlled separately. <P>SOLUTION: Two pairs of set values on the high-speed side and the low-speed side are set in an NC device as the rapid feed speed of the cutting rests and the time constant at the time of acceleration/deceleration. When any of the tool rests is in the process of finish cutting, the rapid feed of other tool rests is executed based on the set value on the low-speed side. When no tool rest is in the process of finish cutting, the rapid feed of the tool rests is executed base on the set value on the high-speed side. A decision whether the tool rests are in the process of finish cutting or in the process of rapid feed can be given by putting up a flag in each of the tool rests when those operations are commanded, or by detecting the feeding speed of each tool rest. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a turret in a machine tool provided with a plurality of turrets (including what is called a tool head) and a head stock (hereinafter referred to as “the turret”) that can be moved by cutting or fast-forwarding. The present invention relates to a fast-forward control method.

  A machine tool processes a workpiece by moving the tool relative to the workpiece. Therefore, during machining of the workpiece, the tool post holding the tool, the tool head, the spindle holding the workpiece, or the table moves on the frame of the machine tool. These mechanical units have a very large mass.

  The feed rate of the tool during workpiece machining is determined by the type of machining, the material of the workpiece and the tool edge, the required surface accuracy after machining, and the like. Even when machining the same workpiece, in rough machining where machining surface accuracy is not required, the tool feed rate is high, and in finishing cutting where high machining surface accuracy is required, the tool feed rate is slow. In the NC machine tool, the control device controls the speed of the feed motor that moves the tool post and the like so that the tool feed speed described in the NC program is realized.

  A tool post or the like of a machine tool performs a movement for positioning and a return to a home position before and after cutting feed. Since the time required for this movement is a loss time during which machining on the workpiece is not performed, these movements are performed at high speed (generally referred to as “fast-forward”) to reduce the machining time. The time constant that defines the rapid feed rate and the acceleration of the tool post at the start and end of fast feed is registered in the NC unit for each tool post.

  In a machine tool provided with a plurality of turrets, each is normally operated individually according to a machining program prepared for each turret (when a plurality of turrets are operated synchronously, a synchronous operation is commanded. Put a wait command before the block to synchronize.) For example, in a two-spindle opposed lathe equipped with three tool rests 4a, 4b, 4c shown in FIG. 6, NC programs 11a, 11b, 11c for controlling each of the three tool rests 4a, 4b, 4c; The NC program 11d for controlling the moving-side head stock 5b is registered in the NC device 1, and the respective tool rests 4a, 4b, 4c and the moving-side head stock 5b operate individually according to the respective programs. Therefore, each turret cannot recognize what operation the other turrets are performing.

  In FIG. 6, reference numeral 5 denotes a fixed-side main spindle base, 5b denotes a moving-side main spindle base, 6a and 6b denote chucks attached to opposite ends of the main spindles supported by the main spindle bases 5a and 5b, and 7a and 7b denote The workpieces 3a, 3b, 3c and 3d held by the respective chucks are feed motors of the respective tool rests 4a, 4b and 4c and the moving side headstock 5b, and the tool rests 4a, 4b and 4c have a plurality of feed motors. Although provided, only the feed motor in the Z-axis direction (spindle axis direction) is shown in the figure.

  The two-spindle counter lathe shown in the figure is a turret turret having tool turrets 8a and 8b arranged on the left and right turrets 4a and 4b arranged below the spindle axis A, and the left turret 4a machining the left workpiece 7a. Then, the right tool post 4b processes the right workpiece 7b. The tool post 4c disposed above the spindle axis is a tool post provided with a rotary tool shaft 9 that can be swiveled around the Y axis (axis perpendicular to the drawing in the drawing), and the left and right workpieces 7a, 7b as required. Is moved to a position opposite to the center of the workpiece, and a drill or a milling cutter mounted on the rotary tool shaft 9 is used to perform drilling or flattening of the workpiece peripheral surface.

  In the machine tool as shown in FIG. 6, two workpieces 7a and 7b are processed in parallel on the same machine. Since the operation of each tool post or the like is individually controlled, for example, when finishing cutting of the right workpiece 7b with the lower right tool post 4b, the other tool post 4a, 4c, 5b It happens that fast-forwarding works. Since the tool post or the like has a large mass, when the rapid feed speed is increased, a large inertia force acts during the fast feed operation of the tool post or the like, particularly during acceleration / deceleration thereof, and this vibrates the machine frame. And the vibration of this machine frame brings about the fall of the surface precision of the finish cutting by the tool post 4b. Therefore, when finishing cutting of a workpiece with any turret, etc., the rapid feed speed and acceleration / deceleration time constant of the turret when machining the workpiece are determined by the vibration of the machine frame that occurs during rapid feed. It was necessary to set the value so as not to adversely affect the accuracy of finish cutting.

  In order to shorten the loss time of the machine tool during workpiece machining and increase the machining efficiency, it is preferable to increase the rapid feed speed of the tool post and shorten the time constant during acceleration / deceleration. However, if the rapid feed speed is increased or the acceleration / deceleration time is shortened, the vibration of the machine frame accompanying the rapid feed increases and the surface accuracy of the finish cutting is reduced.

  Setting values such as the rapid feed speed of the turret and the time constant during acceleration / deceleration can be changed. When machining a workpiece for which finish cutting is performed, it is possible to reduce the rapid feed speed setting value, but it is troublesome to change the rapid feed speed setting value according to the workpiece. The problem that the machining efficiency of the workpiece to be performed is not solved.

  The present invention has been made to solve the above-described problem. In a machine tool including a plurality of tool rests whose movements are individually controlled, the finish cutting is performed when a workpiece with finish cutting is processed. It is an object of the present invention to provide a technical means for improving the machining efficiency of a workpiece by increasing the rapid feed speed without reducing the machining accuracy.

  In the present invention, two sets of high speed side and low speed side set values are set in the NC device as the fast feed speed of the turret and the acceleration / deceleration time constant, and one of the turrets is finishing cutting. In some cases, fast feed of other turrets is executed based on the set value on the low speed side, and when none of the turrets are finishing, the fast feed of the turret etc. is set to the set value on the high speed side. By performing based on the above, the above-described problems are solved.

  That is, the fast-forward control method for a machine tool having a plurality of tool rests according to the invention of claim 1 of the present application is a fast-feed control method for a tool rest of a machine tool having a plurality of tool rests controlled by an NC program. Two types of parameters for fast-forwarding operation, a parameter for fast-forwarding operation with a large speed or acceleration during acceleration and a parameter for fast-forwarding operation with a small acceleration during acceleration or deceleration, are registered in the NC device. When it is detected that the other turret or headstock is finishing cutting when starting the rapid traverse operation on the platform or headstock, the one turret or headstock is moved at a low speed or acceleration. If none of the other turrets and headstocks are in the finish cutting process, the one turret or headstock is caused to execute a fast feed operation with a large speed or acceleration, If it is detected that the other turret or headstock is in fast-forward operation with high speed or acceleration when the headstock starts the finishing cutting operation, it waits until the rapid-feeding operation is finished and then finishes the finishing. The cutting operation is started.

  A fast-forward control method according to claim 2 of the present application is the fast-feed control method for a machine tool having a plurality of tool rests according to claim 1, wherein a finish-cutting flag is set when a finish-cut operation is started. Turn on to turn off the flag when the cutting operation ends, turn on the fast-forwarding flag to start a fast-forward operation with high speed or acceleration during acceleration / deceleration, and turn on the fast-forward operation when the fast-forward operation ends. When the intermediate flag is turned off and a fast-feed operation with a high speed or acceleration at the time of acceleration / deceleration is executed on condition that the finish-cutting flag is off when rapid feed is commanded, and the finish-cutting flag is on Executes a rapid traverse operation with low acceleration during acceleration or deceleration, and when finishing cutting is commanded, the finish is performed on condition that the rapid traverse flag is off. It is characterized in performing a cutting.

  The fast feed (positioning) operation and finish cutting operation of the tool post and the like are instructed by the NC program G code. The feed rate of the tool post or the like at the time of cutting is specified by the F function of the G code that specifies it. A tool used for machining is specified by the T function. Finish cutting is performed at a slower feed rate than roughing with a tool suitable for it. Therefore, by determining the threshold value of the tool to be used and the feed rate, when the NC device reads the block of the NC program, the machining operation commanded by the block is determined by the tool type and the feed rate threshold value. It can be automatically determined by the NC device whether it corresponds to the finished cutting performed. In addition, since the positioning of the tool post or the like by fast-forwarding is assigned to a specific G code (usually G00), when the NC device reads a block of the NC program, the next operation is an operation involving fast-forwarding. It can be automatically determined by the NC device.

  When the read NC program block is accompanied by a fast-forward operation, the NC device automatically determines whether other turrets are finishing cutting (during finishing cutting, the NC device memory is finishing cutting) A flag indicating that the speed is given from the NC device to the feed motor of each tool post, etc., is compared with a set threshold, and the F function or T of the G code executed by each tool post, etc. The value specified by the function is stored in the memory of the NC device and can be automatically determined by comparing the value with the set threshold value.) If any of the turrets are finished cut If medium, the fast-forward operation is executed using the set value on the low speed side. As a result, it is possible to prevent a reduction in the accuracy of finish cutting performed by another tool post or the like by a rapid feed operation of the tool post or the like.

  In addition, when the read block is a command for finishing cutting operation, it is automatically determined by the NC device whether another tool post or the like is in fast-forwarding operation (during fast-forwarding operation, fast-forwarding operation is in progress in the NC device memory) It can be automatically determined by setting a flag indicating that it is present, referring to the speed command given to the feed motor of each tool post, etc.) Waits until the fast-forward operation is completed, and then starts the finishing cutting operation. Thereby, it is possible to avoid the finish cutting and the rapid feed operation on the high speed side being performed in parallel.

  In general machine tools, the headstock is fixed at a fixed position and the workpiece is machined by feed in the Z and X directions of the tool rest. However, in a machine tool in which the head stock can move in the Z direction, The workpiece may be processed by X-direction feed and Z-direction feed of the headstock. In such a machine tool, there is a case where finish cutting is performed by movement of the headstock.

  By the above-described method of the present invention, the rapid feed operation of another turret or the like when one of the turrets or the like is performing finish cutting is always performed based on the set value on the low speed side. Therefore, if the set value of the low-speed side fast-forwarding operation is set to a value that does not cause vibration that may reduce the accuracy of finish cutting on the machine frame, the fast-forwarding operation of other turrets, etc. As a result, it is possible to avoid a reduction in finishing cutting accuracy.

  In the method of the present invention, since the finish cutting is not started until the rapid feed of the other tool post or the like is finished, it is considered that this standby time decreases the machining efficiency, but the fast feed operation is finished in a short time, so The decrease in machining efficiency due to time is much smaller than in the conventional method in which all the rapid feed speeds during workpiece machining are reduced.

  When there is a large number of tool rests etc., the fast feed of the next tool rest etc. starts before the rapid feed of one tool rest etc. is completed, and there is a possibility that the waiting time for finishing cutting may become longer. If, after a finish cutting command is given to a tool post or the like, a flag indicating that the finish cutting is in progress is set to stand by, all the fast feed commands issued thereafter will be fast feeds on the low speed side. Finishing cutting can be started when the fast-forwarding is completed.

  According to the method of the present invention, in a machine tool provided with a plurality of tool rests, finishing caused by machine vibration accompanying fast-forwarding operation when fast-forwarding operation and finishing cutting operation of a certain tool post or the like are performed in parallel. A reduction in cutting accuracy can be avoided.

  Also, the feed rate of the turret etc. is performed on the low speed side only when other turrets are performing finish cutting.In other cases, fast feed is performed based on the set value on the high speed side. As a result, the reduction in machining efficiency due to rapid feed at low speed can be minimized.

  Furthermore, depending on whether finishing cutting is included in the workpiece processing, it is not necessary to change the setting value of the rapid feed speed. Forgetting this changing operation reduces the machining efficiency and decreases the finishing cutting accuracy. There is no fear.

  Next, an embodiment of the present invention will be described with reference to the drawings. FIGS. 1 and 2 are a control block diagram and a control flowchart illustrating the first embodiment, and are diagrams illustrating an example in which control is performed with reference to a command value output from an NC apparatus to a feed motor such as each tool post. is there. In the block diagram of FIG. 1, 1 is an NC device, 2 (2a, 2b, 2c) is a servo amplifier, 3 (3a, 3b, 3c) is a feed motor, and subscripts a, b, c are for example 6 indicates that the three tool rests 4a, 4b, and 4c shown in FIG. Each tool post 4a, 4b, 4c is provided with a plurality of servo amplifiers and feed motors, but only one of them is shown here as in FIG.

  The NC apparatus 1 has a number of NC program data 11 (11a, 11b, 11c) corresponding to the number of tool posts and the like. The NC device 1 reads NC program data block by block, interprets the syntax by the NC sentence interpretation unit 12, and outputs the result to the command processing unit 13 (13a, 13b, 13c) of the corresponding tool post. Each command processing unit 13a, 13b, 13c sends a command signal to the corresponding servo amplifier 2a, 2b, 2c based on the received data, and controls feed motors 3a, 3b, 3c such as each tool post.

  For example, when the tool post 4a is fast-forwarding, a speed command corresponding to the fast-forwarding speed is output from the command processing unit 13a that controls the feed motor 3a. Further, when the tool post 4b is performing finish cutting, a speed command corresponding to the feed speed for finishing cutting is output from the command processing unit 13b that controls the feed motor 3b.

  The NC device 1 is provided with a threshold value setting unit 14 for registering a threshold value of a feed rate that is a criterion for finishing cutting. Further, the NC device 1 is provided with a parameter change processing unit 15 and a parameter setting unit 16 for low-speed fast-forwarding for registering a low-speed side fast-forwarding speed and a time constant during acceleration / deceleration. For fast feed on the high speed side, parameters for fast feed at the normal speed (high speed) set in the command processing units 13a, 13b, and 13c are used.

  When the command processing units 13a, 13b, and 13c that control a tool post receive new data from the NC sentence interpretation unit 12, the parameter change processing unit 15 receives the fast-forward command or the finish cutting command data. Check if it is. And when it is the data of a rapid feed command or a finish cutting command, the speed command output from the command processing part of another tool post is referred. When the received data is fast-forwarding data and there is a speed command value that is lower than the value set in the threshold setting unit 14 in the referenced speed command, the parameter for the fast-forwarding operation is set as the parameter for low-speed fast-forwarding. The parameter is changed to a parameter registered in the setting unit 16. Also, if the received data is finish cutting data and there is a speed command value that is higher than the rapid feed speed set in the low speed rapid feed parameter setting section in the referenced speed command, the speed command value The finish cutting is made to wait until the operation is completed.

  The control procedure of the NC device corresponding to the block diagram of FIG. 1 is shown in FIG. When one block of data is read from the NC program, it is determined whether or not it is a fast-forward command. If it is a fast-forward command, the parameter change processing unit 15 is sent at a speed slower than the feed speed set in the threshold setting unit 14. If there is a tool post that is in use, change the fast-forward command parameter to the value set in the low-speed fast-forward parameter setting unit 16 and execute the fast-forward. Restore the command parameters. Further, when the read data of one block is a cutting command and the feed speed is smaller than the threshold set in the threshold setting unit 14, it is determined that it is a finishing cutting command and is set in the low speed rapid feed parameter setting unit 16. It is checked whether there is a tool post moving at a speed exceeding the fast-forwarding speed, and if there is, the commanded processing is executed after waiting for the end. When it is neither a rapid feed command nor a finish cutting command, another operation commanded in the block is executed.

  3 and 4 are views showing a second embodiment of the present invention, FIG. 3 is a control block diagram, and FIG. 4 is a control flowchart. In this embodiment, one block of data read from the NC programs 11a, 11b, and 11c is interpreted by the NC sentence interpretation unit 12, and the G code number, F function, and T function data are passed to the parameter change processing unit 15. When the data is a fast feed command or a finish cutting command, the parameter change processing unit 15 determines a finish feed or fast feed state by setting a necessary flag.

  In the second embodiment, as shown in FIG. 5, when the G00 code for instructing the fast-forward operation is read, the codes displayed as M * 1 and M * 2 before and after the internal function of the NC device. Processing to add. Here, M * 1 changes the parameter of the rapid feed command to the parameter set in the low speed rapid feed parameter setting unit 16 when the finish cutting flag of another tool post is on (turned on), Otherwise, it is an M code whose processing content is to set a fast-forwarding flag, and M * 2 is an M code whose content is to return processing to the original with M * 1. When the cutting feed command commanded in G01 is read, the M function indicated as M * 3 is added. M * 3, when the feed speed commanded by the F function is equal to or less than the feed speed set in the threshold setting unit 14, raises a flag during finishing cutting and checks whether the fast feed flag is set. When the flag is set, the M code waits for execution of the commanded cutting until the flag returns. M * 4 is an M code for returning the flag set in M * 3 to the original state.

  FIG. 4 shows a control flowchart of the second embodiment. When one block read from the NC program is M * 1, the finishing cutting flag of another tool post is checked, and the finishing cutting flag is set. If so, the rapid feed speed and time constant parameters are changed to the set values of the low speed rapid feed parameter setting unit 16, and if no finish cutting flag is set on any turret, the fast feed flag is set. When the read block is M * 2, the fast-forwarding flag is turned off, and the fast-forward speed and time constant parameters are restored. When the read block is M * 3, the finishing cutting flag is turned on, the fast-forwarding flag of another turret is checked, and if there is a turret with the fast-forwarding flag on, the flag is turned off. Wait until. If M * 4, the finishing cutting flag is turned off. If the read block is a block other than M * 1, M * 2, M * 3, and M * 4, the commanded process is executed and the next block is read. If the program ends, the machining operation ends.

  In the second embodiment, the fast feed parameter changing process and the finish cutting standby process are performed with reference to the flag indicating the state of each tool post, so it is possible to freely select under what conditions the flag is set. More flexible and accurate control is possible.

Control block diagram of the first embodiment Control flowchart of the first embodiment Control block diagram of the second embodiment Control flowchart of the second embodiment The figure which shows the principal part of the program list of 2nd Embodiment. The schematic diagram which shows an example of the machine tool with which the method of this invention is implemented

Explanation of symbols

1 NC device
3a, 3b, 3c feed motor
4a, 4b, 4c Turret
7a, 7b Workpiece
14 Threshold setting unit
16 Low-speed rapid feed parameter setting section

Claims (2)

  In a rapid feed control method for a tool post of a machine tool having a plurality of tool rests controlled by an NC program, the NC device includes a parameter for fast feed operation with a large speed or acceleration during acceleration / deceleration and a parameter for fast feed operation with a small speed. When parameters for two types of rapid traverse operations are registered and when one turret or headstock starts a rapid traverse operation, when it is detected that the other turret or headstock is in the finish cutting, When a fast-forward operation with a low speed or acceleration is executed on the tool post or headstock, and no other tool post or headstock is being finished, fast-forwarding with a high speed or acceleration is made to the one tool post or headstock. When one of the turrets or headstock starts the finishing cutting operation, it is detected that the other turret or headstock is in fast-forward operation with high speed or acceleration. Been time is characterized in that the rapid-traverse operation starts after the finishing cutting operation waits until the end of the machine tool of fast-forward control method having a plurality of tool rests.   Turn on the finish cutting flag when starting the finish cutting operation, turn the flag off when the cutting operation ends, and set the fast feed flag when starting the fast feed operation with a high speed or acceleration during acceleration / deceleration. Turn on and turn off the fast-forwarding flag when the fast-forwarding operation is complete, and perform fast-forwarding operations with high speed or acceleration during acceleration / deceleration on condition that the finishing cutting flag is off when fast-forwarding is commanded. If there is a finish cutting flag that is on, a fast-forward operation with a low speed or acceleration during acceleration / deceleration is executed, and when finishing cutting is commanded, the finish is performed on condition that the fast-feed flag is off. The fast-forward control method according to claim 1, wherein cutting is performed.

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