Simultaneous machining simulator and machine tools

Abstract

To provide a simultaneous machining simulator capable of estimating the relative displacement occurring between a tool and a workpiece based on certain set cutting conditions when simultaneous machining is performed, and predicting in advance the finishing accuracy of the workpiece by the tool. [Solution] A simultaneous machining simulator 100 that simulates a state in which a first workpiece W1 and a second workpiece W2 are simultaneously machined by a first tool T1 and a second tool T2, respectively, includes a model storage unit 1 that stores a vibration transmission model that receives as input the frequency of vibration generated between the first workpiece W1 and the first tool T1 and outputs the relative displacement between the second workpiece W2 and the second tool T2, and a relative displacement output unit 2 that outputs the relative displacement between the second workpiece W2 and the second tool T2 that corresponds to the frequency of vibration generated between the first workpiece W1 and the first tool T1 based on the vibration transmission model.

Description

[Technical Field]

[0001] The present invention relates to a simultaneous machining simulator that estimates the state when machining is performed simultaneously at multiple points using tools held by each tool holder in a machine tool equipped with multiple tool holders. [Background technology]

[0002] Standby power accounts for a large portion of the energy consumed by machine tools. One method for reducing such unnecessary power consumption is to simultaneously machine multiple workpieces on a single machine tool to shorten cycle time. For example, Patent Document 1 discloses a machine tool equipped with two workpiece spindles that rotatably hold workpieces and two turrets, which are tool holders, corresponding to the workpieces. Using this machine tool, a workpiece held by a first workpiece spindle is subjected to rough machining, which involves a large amount of cutting and vibration, while a workpiece held by a second workpiece spindle is simultaneously subjected to finish machining, which involves a small amount of cutting and vibration. To prevent vibrations generated by the first workpiece spindle from propagating to the second workpiece spindle and reducing the accuracy of the finish machining, a method has been proposed in which a sensor detects the amplitude of vibrations generated by the first workpiece spindle and then vibrates the second workpiece spindle in the opposite phase based on the detected value, thereby preventing a decrease in finishing accuracy even when simultaneous machining is performed.

[0003] However, the above-mentioned method requires the installation of a special sensor or vibrator on the machine tool, and there is a possibility that the expected finishing accuracy may not be maintained depending on the responsiveness of the sensor or vibrator.Furthermore, the reason why the above-mentioned configuration has been proposed is that there is no method for clearly determining what cutting conditions should be selected in simultaneous machining in order to maintain high finishing accuracy while maintaining machining efficiency. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 11-114774 Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention has been made in consideration of the above-mentioned problems, and aims to provide a simultaneous machining simulator that can estimate the relative displacement that occurs between a tool and a workpiece based on certain set cutting conditions when simultaneous machining is performed, and can predict in advance the finishing accuracy of the workpiece with that tool, and a machine tool that uses the same. [Means for solving the problem]

[0006] That is, the simultaneous machining simulator of the present invention is a simultaneous machining simulator that simulates a state in which a first workpiece and a second workpiece are simultaneously machined by the first tool and the second tool, respectively, in a machine tool having a first tool holding unit that holds a first tool for machining a first workpiece and a second tool holding unit that holds a second tool for machining a second workpiece, and is characterized by comprising: a model memory unit that stores a vibration transmission model that receives as input the frequency of vibration generated between the first workpiece and the first tool and outputs the relative displacement between the second workpiece and the second tool; and a relative displacement output unit that outputs, based on the vibration transmission model, the relative displacement between the second workpiece and the second tool that corresponds to the frequency of vibration generated between the first workpiece and the first tool.

[0007] With this configuration, it is possible to evaluate the relative displacement between the second workpiece and the second tool caused by the propagation of vibrations generated between the first workpiece and the first tool according to the frequency of the vibrations. Therefore, when simultaneous machining is performed, if the frequency of vibration is set high to increase the machining efficiency between the first workpiece and the first tool, it is possible to predict in advance how much the machining accuracy of the second workpiece will deteriorate, and it becomes easy to set machining conditions that achieve both machining efficiency and finishing accuracy.

[0008] To make it easier for the operator to determine which frequency within a specified frequency band to select for the vibration between the first workpiece and the first tool will reduce the relative displacement between the second workpiece and the second tool, thereby improving machining accuracy and enabling highly efficient simultaneous machining, the device may further include a frequency response display unit that displays a graph showing the frequency response of the relative displacement between the second workpiece and the second tool to the frequency of the vibration occurring between the first workpiece and the first tool, based on the output of the relative displacement output unit.

[0009] If the frequency of vibration occurring between the first workpiece and the first tool is a value calculated based on the rotation speed set for the first workpiece or the first tool, it becomes easier to set major machining parameters such as the rotation speed of the tool spindle or workpiece spindle.

[0010] In order to easily obtain a frequency or frequency band that can achieve the required machining accuracy for the second workpiece from the simulation results, it is sufficient to further include an allowable value receiving unit that receives an allowable value of the relative displacement between the second workpiece and the second tool, and an appropriate frequency output unit that outputs the frequency corresponding to the relative displacement that satisfies the allowable value based on the output of the relative displacement output unit.

[0011] In order to obtain machining parameters that can achieve both machining efficiency and finishing accuracy in simultaneous machining, it is sufficient that the appropriate frequency output unit outputs the highest frequency among the frequencies that is equal to or higher than the minimum frequency and equal to or lower than the safe allowable frequency.

[0012] A machine tool equipped with the simultaneous machining simulator according to the present invention makes it easy to set appropriate machining parameters for each machining operation in the machine tool when simultaneous machining is performed. [Effects of the Invention]

[0013] In this way, the simultaneous machining simulator according to the present invention makes it easy to select machining parameters that can achieve both machining efficiency and finishing accuracy in simultaneous machining. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram of a machine tool that is a simulation target of a simultaneous machining simulator according to a first embodiment of the present invention. [Figure 2] FIG. 1 is a functional block diagram showing the configuration of a simultaneous machining simulator according to a first embodiment. [Figure 3] An example of a simulation result of the simultaneous machining simulator according to the first embodiment [Figure 4] FIG. 10 is a schematic diagram of a machine tool that is a simulation target of a simultaneous machining simulator according to a second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0015] A simultaneous machining simulator 100 according to a first embodiment of the present invention will be described below with reference to the drawings.

[0016] The simultaneous machining simulator 100 of the first embodiment simulates the state of simultaneous machining in a machine tool MT equipped with two tool holders as shown in Fig. 1. Here, simultaneous machining refers to machining in which at least two tools act simultaneously on a common workpiece or on separate workpieces. Note that in the first embodiment, turning is performed on each of the two workpieces, but one of the two workpieces may be a different machining such as cutting or grinding.

[0017] The machine tool MT to be simulated includes, for example, a first workpiece holder WH1, which is a workpiece spindle that rotatably holds a first workpiece W1; a second workpiece holder WH2, which is an opposing workpiece spindle that faces the first tool holder TH1 and rotatably holds a second workpiece W2; a first tool holder TH1, which is a turret that holds a first tool T1 for machining the first workpiece W1; and a second tool holder T2, which is a turret that holds a second tool T2 for machining the second workpiece W2. The first workpiece holder WH1, the second workpiece holder WH2, the first tool holder TH1, and the second tool holder T2 are supported directly or indirectly by the bed, and vibrations generated in each part interact with each other. In other words, vibrations generated when machining the first workpiece W1 with the first tool T1 not only affect the first workpiece W1 but also affect the second workpiece W2 and the second tool T2, such as by relative displacement, via the vibration propagation path via the bed, etc. In this machine tool MT, a first workpiece W1 is rough-machined with a first tool T1, and a second workpiece W2 is finish-machined with a second tool T2. The second workpiece W2 is the first workpiece W1 after machining, and is transferred between the first workpiece holder WH1 and the second workpiece holder WH2.

[0018] The simultaneous machining simulator 100 of the first embodiment is configured to simulate the magnitude of relative displacement between the second workpiece W2 and the second tool T2 caused by vibrations occurring in the first workpiece W1 on which at least rough machining is performed.

[0019] The simultaneous machining simulator 100 is a so-called computer equipped with, for example, a CPU, memory, various input / output devices, etc., in which a program stored in the memory is executed and its functions are realized by the cooperation of various devices. Note that the computer may be a dedicated computer, or its functions may be realized on the cloud, or may be realized by the computational resources of the machine tool MT. More specifically, the simultaneous machining simulator 100 includes at least a model storage unit 1, a relative displacement output unit 2, a frequency response display unit 3, a tolerance acceptance unit 4, and an appropriate frequency output unit 5, as shown in the functional block diagram of FIG. 2.

[0020] Each part will be described in detail. The model storage unit 1 stores a vibration transmission model that takes the frequency of vibration occurring between the first workpiece W1 and the first tool T1 as an input and the relative displacement between the second workpiece W2 and the second tool T2 as an output. This vibration transmission model is created based on, for example, a finite element model of the machine tool MT that is the object of the simulation. More specifically, the respective displacement vectors of the first tool T1, first workpiece W1, second tool T2, and second workpiece W2 during simultaneous machining are represented by U. T1 , U W1 , U T2 , U W2 and the force vectors representing the forces acting on each of them are F T1 , F W1 , F T2 , F W2 The first tool T1, the first workpiece W1, the second tool T2, and the second workpiece W2 interact with each other, so for example, the displacement U T1 can be defined as follows: U T1 =[G T1,T1 G T1,W1 G T1,T2 G T1,W2 ] [F T1 F W1 F T2 F W2 ] THere, Gi,j is the transfer function between i and j. The relationship between the displacement vectors and force vectors in the first workpiece W1, the second tool T2, and the second workpiece W2 can be defined in a similar way. Therefore, it can be summarized using a matrix as U=GF. Here, U is a column vector in which the displacement vectors are arranged, G is a transfer function matrix, and F is a column vector in which the force vectors are arranged. Furthermore, in this embodiment, the force vectors are defined separately for each frequency, so that it is possible to calculate what kind of relative displacement occurs at each machining point when vibration of a certain frequency is occurring.

[0021] Based on the vibration transmission model described above, the relative displacement output unit 2 outputs the relative displacement between the second workpiece W2 and the second tool T2 corresponding to at least the frequency of vibration occurring between the first workpiece W1 and the first tool T1. That is, based on the vibration transmission model, the relative displacement output unit 2 calculates and outputs the vibration amplitude that will be generated in the second workpiece W2 being finish-machined due to vibration caused by rough machining of the first workpiece W1. Note that the relative displacement output unit 2 may also calculate the relative displacement between the first workpiece W1 and the first tool T1 corresponding to the frequency of vibration occurring between the second workpiece W2 and the second tool T2.

[0022] Based on the output of the relative displacement output unit 2, the frequency response display unit 3 displays a graph showing the frequency response of the relative displacement between the second workpiece W2 and the second tool T2 to the frequency of vibration occurring at least between the first workpiece W1 and the first tool T1. For example, as shown in Figure 3, a frequency response graph is displayed with frequency on the horizontal axis and absolute value of relative displacement on the vertical axis. Here, the frequency of vibration occurring between the first workpiece W1 and the first tool T1 is a value calculated based on the rotation speed set for the first workpiece holder WH1 that holds the first workpiece W1. Note that if the first tool T1 is a rotating tool rather than a fixed tool, the frequency is calculated based on the rotation speed set for the first tool. Note that Figure 3 is an example of a simulation of the effect on the relative displacement between the second workpiece W2 and the second tool T2 from a machining point consisting of the first workpiece W1 and the first tool T1 during rough machining. This shows that because the vibration transmission rate from one machining point to another varies depending on the frequency, simply lowering the rotational speed of the first tool T1 performing rough machining and relaxing the cutting conditions does not necessarily result in a smaller vibration amplitude in the second workpiece W2 performing finish machining.In other words, by referring to a frequency response graph like the one in Figure 3, the operator can select conditions that increase the rotational speed of the first workpiece W1, maintain high cutting efficiency, and minimize the impact of vibration on the second workpiece W2 performing finish machining.

[0023] The tolerance receiving unit 4 receives a tolerance for the relative displacement between the second workpiece W2 and the second tool T2 from, for example, an operator.

[0024] The optimum frequency output unit 5 presents a frequency recommended for machining the first workpiece W1. Based on the output of the relative displacement output unit 2, the optimum frequency output unit 5 outputs a frequency corresponding to a relative displacement that satisfies the accepted tolerance or a corresponding rotational speed to be set for the first workpiece W1. More specifically, the optimum frequency output unit 5 is configured to output the highest frequency corresponding to the rotational speed to be set for the first workpiece W1 that is equal to or greater than the minimum wave number and equal to or less than the safe permissible frequency. The minimum frequency is a value that is preset, for example, from the perspective of machining efficiency or based on the minimum rotational speed of the first workpiece W1 required to achieve a cutting speed that allows cutting. A frequency lower than this is not permitted to be output from the optimum frequency output unit 5. The safe permissible frequency is preset based, for example, on the upper limit frequency that can prevent breakage of the first tool T1 or breakdown of each device, or the upper limit frequency that can prevent the first workpiece W1 itself from being dislodged from the first workpiece holder WH1 due to centrifugal force, etc.

[0025] The simultaneous machining simulator 100 of the first embodiment configured as described above can evaluate the effect of rough machining on the machining point of the second workpiece W2, where finish machining is performed, from the machining point of the first workpiece W1. Also, since it is possible to obtain a change in the relative displacement between the second workpiece W2 and the second tool T2 according to the frequency of vibrations generated in the first workpiece W1, it is possible to minimize the effect of vibrations generated in the second workpiece W2 during rough machining while setting the rotation speed of the first tool T1 in a high range, and ensure the finishing accuracy of the second workpiece W2.

[0026] A simultaneous machining simulator 100 according to a second embodiment of the present invention will be described with reference to FIG. 4. Components corresponding to those described in the first embodiment are designated by the same reference numerals. The simultaneous machining simulator 100 of the second embodiment differs in the configuration of the machine tool MT to be simulated. Specifically, the first tool T1 is a rotating tool rather than a fixed tool, and the first tool holder TH1 serves as the tool spindle. Even when the configuration of the machine tool MT differs in this way, the simultaneous machining simulator 100, which has a configuration similar to that shown in FIG. 2, can appropriately evaluate the effect of vibrations generated between the first tool T1 and the first workpiece W1 on the second workpiece W2, and determine the rotation speed to be set for the first tool T1 that satisfies both machining efficiency and finishing accuracy of the second workpiece W2.

[0027] Other embodiments will be described. In each embodiment, the simultaneous machining simulator simulates simultaneous machining of a first workpiece and a second workpiece, but it may also be configured to similarly simulate simultaneous machining of three or more workpieces. The simultaneous machining simulator of the present invention may be provided in the machine tool itself. Alternatively, only the simulation results may be provided to the machine tool's control panel via the cloud or other means. This facilitates determining machining conditions, such as the appropriate workpiece or tool rotation speeds for simultaneous machining, while the operator is operating the machine tool. The machine tool to be simulated is not limited to a turning center with multiple spindles, but may also be a multi-tasking machine or other type of machine tool configured to enable simultaneous machining. Machine tools configured such that vibrations generated at each machining point may affect other machining points may also be targeted.

[0028] In addition, various modifications of the embodiments and combinations of parts of the embodiments may be made as long as they do not go against the spirit of the present invention. [Explanation of symbols]

[0029] 100 simultaneous machining simulator, 1 model memory unit, 2 relative displacement output unit, 3 frequency response display, 4 tolerance acceptance unit, 5 optimum frequency output unit

Claims

1. A simultaneous machining simulator for a machine tool including a first tool holding unit that holds a first tool for machining a first workpiece and a second tool holding unit that holds a second tool for machining a second workpiece, the simultaneous machining simulator simulating a state in which the first workpiece and the second workpiece are simultaneously machined by the first tool and the second tool, respectively, comprising: a model storage unit that stores a vibration transmission model in which a frequency of vibration generated between the first workpiece and the first tool is input and a relative displacement between the second workpiece and the second tool is output; A simultaneous machining simulator comprising: a relative displacement output unit that outputs a relative displacement between the second workpiece and the second tool corresponding to a frequency of vibration occurring between the first workpiece and the first tool based on the vibration transmission model.

2. 2. The simultaneous machining simulator according to claim 1, further comprising a frequency response display unit that displays a graph showing the frequency response of the relative displacement between the second workpiece and the second tool to the frequency of vibration occurring between the first workpiece and the first tool based on the output of the relative displacement output unit.

3. 2. A simultaneous machining simulator according to claim 1, wherein the frequency of vibration occurring between the first workpiece and the first tool is a value calculated based on the rotation speed set for the first workpiece or the first tool.

4. a tolerance receiving unit that receives a tolerance of a relative displacement between the second workpiece and the second tool; 2. The simultaneous machining simulator according to claim 1, further comprising an appropriate frequency output section that outputs the frequency corresponding to the relative displacement that satisfies the allowable value based on the output of the relative displacement output section.

5. 5. A simultaneous machining simulator according to claim 4, wherein the appropriate frequency output unit outputs the highest frequency among the frequencies that is equal to or higher than the minimum frequency and equal to or lower than a safe allowable frequency.

6. A machine tool equipped with the simultaneous machining simulator according to any one of claims 1 to 5.

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