Machine tool control device

Abstract

In the control device of the machine tool performing oscillating cutting, the load on the machine tool can be reduced universally regardless of the structure of the machine tool. The control device (1) of the machine tool that performs oscillating cutting by oscillating the tool (T) relative to the workpiece (W) includes: an approach angle acquisition unit (12) that acquires the approach angle (θ1) of the tool (T); an oscillation amplitude calculation unit (13) that calculates the oscillation amplitude required to break the chip in any oscillation direction based on the approach angle (θ1) of the tool (T); an oscillation direction determination unit (14) that determines the oscillation direction based on the calculation result of the oscillation amplitude calculation unit (13); and an oscillation action control unit (15) that controls the oscillation action in the oscillation direction determined by the oscillation direction determination unit (14) based on the machining conditions.

Description

Technical Field

[0001] This disclosure relates to control devices for machine tools. Background Technology

[0002] Previously, it was known that during machining of a workpiece using a cutting tool, continuously generated chips would become entangled in the cutting tool, leading to poor machining and machine tool malfunctions. To address this, a method called oscillating cutting was proposed, which involves cutting while simultaneously oscillating the cutting tool and workpiece relative to each other to break up the chips. Typically, in oscillating cutting, the cutting tool and workpiece oscillate relative to each other along the machining path.

[0003] For example, when the workpiece has a conical or arc-shaped form, the feed axes for feeding the cutting tool or workpiece in the direction along the machining path are multiple axes (e.g., Z-axis and X-axis). In this case, the load on the machine tool increases because multiple axes oscillate simultaneously. Therefore, a technique has been proposed that, in the conical portion of the workpiece, etc., by changing the oscillation direction from the direction along the machining path to a different direction, it is possible to reduce the load on the machine tool while achieving chip breaking (e.g., see Patent Document 1).

[0004] Figure 7 This diagram illustrates an example of conventional oscillating cutting. In this example, it shows a cutting process performed by moving the tool T along the feed direction of the generatrix of the outer circumferential surface of the workpiece W, which rotates through the spindle S, via the feed axis. Figure 7 As shown, when cutting the tapered portion W1 of workpiece W using tool T, the oscillation direction of the current path changes from the direction along the machining path to a different direction relative to the previous path. For example, from... Figure 7 The oscillation direction along the machining path, indicated by the black arrow, changes to the direction indicated by the white arrow, which is different from this direction. That is, the oscillation component in the Z-axis direction increases while the vibration component in the X-axis direction decreases.

[0005] Existing technical documents

[0006] Patent documents

[0007] Patent Document 1: Japanese Patent No. 6763917 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] However, in Figure 7In the example shown, the oscillation component in the Z-axis direction increases due to the change in oscillation direction, while the oscillation component in the X-axis direction decreases. The situation where the load on the machine tool can be sufficiently reduced is when the inertia of the machine tool in the X-axis direction is much larger than that in the Z-axis direction. That is, in the aforementioned conventional oscillating cutting, the effect of reducing the load on the machine tool depends on the structure of the machine tool.

[0010] Therefore, in the control device of a machine tool that performs oscillating cutting, it is desirable to have a technology that can universally reduce the load on the machine tool, regardless of the machine tool's structure.

[0011] Methods for solving problems

[0012] One aspect of this disclosure is a control device for a machine tool that performs oscillating cutting by oscillating a tool relative to a workpiece. The device includes: an approach angle acquisition unit that acquires the approach angle of the tool; an oscillation amplitude calculation unit that calculates the oscillation amplitude required for chip breaking in any oscillation direction based on the approach angle of the tool; an oscillation direction determination unit that determines the oscillation direction based on the calculation result of the oscillation amplitude calculation unit; and an oscillation action control unit that controls the oscillation action in the oscillation direction determined by the oscillation direction determination unit according to processing conditions.

[0013] Invention Effects

[0014] According to this disclosure, in the control device of a machine tool performing oscillating cutting, the load on the machine tool can be reduced universally regardless of the machine tool's structure. Attached Figure Description

[0015] Figure 1 This is a diagram illustrating the control device of a machine tool according to an embodiment of the present disclosure.

[0016] Figure 2 It is a diagram representing the angle of entry of the tool.

[0017] Figure 3 This is a diagram illustrating the method for calculating the amplitude of oscillation.

[0018] Figure 4 This is a diagram illustrating the first example of oscillating cutting in this embodiment.

[0019] Figure 5 This is a diagram illustrating a second example of the oscillating cutting method of this embodiment.

[0020] Figure 6 This is a diagram illustrating a third example of oscillating cutting in this embodiment.

[0021] Figure 7 This diagram illustrates an example of conventional oscillating cutting. Detailed Implementation

[0022] Hereinafter, embodiments of the present disclosure will be described in detail with reference to the accompanying drawings.

[0023] Figure 1 This diagram illustrates the control device 1 of the machine tool according to this embodiment. The control device 1 of the machine tool in this embodiment performs cutting machining on a workpiece using a tool by operating at least one spindle and at least one feed axis. The at least one spindle rotates the cutting tool (hereinafter referred to as the tool) relative to the workpiece, and the at least one feed axis moves the tool relative to the workpiece. Furthermore, in... Figure 1 For simplicity, only the motor 3 driving one feed axis is shown in the image.

[0024] The machine tool control device 1 of this embodiment performs oscillating cutting by moving the spindle and feed axis. That is, the machine tool control device 1 rotates the tool relative to the workpiece and oscillates the tool relative to the workpiece to perform cutting. The tool path, which is the trajectory of the tool, is set such that the current path partially overlaps with the previous path, and the portion already processed in the previous path is included in the current path. Therefore, by generating an air cut (air cut) in which the tool tip leaves the surface of the workpiece, the chips continuously generated by the cutting process can be reliably shredded.

[0025] The machine tool control unit 1 is configured, for example, using a computer equipped with memory such as ROM (read-only memory) and RAM (random access memory), a CPU (control processing unit), and a communication control unit interconnected via a bus. Figure 1 As shown, the machine tool control device 1 includes a first storage unit 11, a cutting angle acquisition unit 12, a swing amplitude calculation unit 13, a swing direction determination unit 14, a swing motion control unit 15, and a second storage unit 16. The functions and actions of these units can be realized through the cooperation of the CPU, memory, and control program stored in the memory of the computer.

[0026] In addition, a host computer (not shown) such as a CNC (Computer Numerical Controller) or a PLC (Programmable Logic Controller) is connected to the machine tool's control device 1. Besides inputting machining programs from these host computers to the machine tool's control device 1, machining conditions such as rotational speed and feed rate, and oscillation conditions such as oscillation frequency, are also input.

[0027] The angle of entry for the storage device in the first storage unit 11. Here, Figure 2This is a diagram representing the angle θ1 of tool T. Furthermore, from this... Figure 2 To be discussed later Figure 6 These examples illustrate cutting operations performed by moving the tool T along the feed direction of the generatrix of the outer circumferential surface of the workpiece W, which rotates via the spindle S, via the feed axis. However, this embodiment is not limited to such outer diameter machining and can also be applied to inner diameter machining. Furthermore, this embodiment can also be applied to structures where the tool T rotates about the central axis of the workpiece W and the workpiece W moves relative to the tool T in the feed direction. Moreover, in... Figures 2-7 In this process, the central axis of workpiece W is set as the Z-axis, and the direction orthogonal to the Z-axis is set as the X-axis.

[0028] like Figure 2 As shown, the approach angle θ1 of tool T refers to the angle from the Z-axis direction (which is the central axis of workpiece W) to the flank face T1 of tool T. Furthermore, the flank face T1 of tool T refers to the face of tool T on the workpiece W side of the tool tip, and the machining direction (see reference). Figure 2 The face on the side of the black arrow in the diagram. The approach angle θ1 is preset to the desired angle for each of the plurality of tools T, regardless of the taper angle of the machined surface. More specifically, the approach angle θ1 preset for each tool T is stored in a first storage unit in correspondence with each tool T.

[0029] The approach angle acquisition unit 12 acquires the approach angle θ1 of the tool T. Specifically, the approach angle acquisition unit 12 reads and acquires the approach angle θ1 corresponding to the tool from the first storage unit 11 based on the tool data obtained from the machining program input to the machine tool control device 1. The acquired approach angle θ1 of the tool T is output to the oscillation amplitude calculation unit 13, which will be described later.

[0030] The oscillation amplitude calculation unit 13 calculates the oscillation amplitude required for chip crushing in any oscillation direction based on the entry angle θ1 of the tool T obtained by the entry angle acquisition unit 12. The calculated oscillation amplitude for each oscillation direction is output to the oscillation direction determination unit 14 and the oscillation action control unit 15, which will be described later. Furthermore, the oscillation amplitude in this embodiment includes not only the oscillation amplitude itself, but also the oscillation amplitude multiplier.

[0031] Figure 3 This is a diagram illustrating the method for calculating the oscillation amplitude in the oscillation amplitude calculation unit 13. Figure 3 For ease of explanation, the previous swinging direction along the machining path will be referred to as "before the change," and the swinging direction in any direction different from the machining path will be referred to as "after the change." Figures 4-7 (The same applies). For example... Figure 3As shown, using the swing amplitude A required for chip breaking in the swing direction along the machining path before the change, the displacement angle θ of the swing direction before and after the change, the cutting angle θ1 of the tool T, and the angle θ2 formed by the swing direction along the machining path before the change and the Z-axis direction, the swing amplitude A' required for chip breaking in the swing direction after the change is calculated by the following formula (1).

[0032] [Mathematical Expression 1]

[0033] A'=AX(cosθ-sinθ / tan(θ+θ1-θ2)...Equation (1)

[0034] Furthermore, in this embodiment, the swing amplitude refers to the combined swing amplitude of the swing amplitude components in the Z-axis direction and the X-axis direction. That is, the swing amplitude in this embodiment is the combined swing amplitude calculated by the following formula (2).

[0035] The combined oscillation amplitude = ((Z-axis amplitude)) 2 +(X-axis amplitude) 2 ) 1 / 2 ...Equation (2)

[0036] return Figure 1 The swing direction determination unit 14 determines the swing direction based on the swing amplitude calculated by the swing amplitude calculation unit 13. Preferably, the swing direction determination unit 14 determines a swing direction with a swing amplitude A' smaller than the swing amplitude A of the swing motion along the machining path, within the range of swing directions capable of cutting chips. This allows for a general reduction in the load on the machine tool caused by the swing motion.

[0037] More specifically, such as Figure 3 As shown, the swing direction determination unit 14 determines the direction in which the combined swing amplitude of the swing amplitude component in the Z-axis direction and the swing amplitude component in the X-axis direction becomes smaller as the swing direction.

[0038] More preferably, the swing direction determining unit 14 determines the swing direction as the direction perpendicular to the back face T1 of the tool T. In this case, the swing amplitude is set to the minimum that can break the chips, so as to minimize the load on the machine tool while breaking the chips.

[0039] The second storage unit 16 stores machining conditions for the workpiece W. These machining conditions include the relative rotational speed of the workpiece W and the tool T around the central axis of the workpiece W, the relative feed rate between the tool T and the workpiece W, and position commands for the feed axis. The second storage unit 16 stores the machining program executed by the machine tool. The CPU within the machine tool's control unit 1 reads the rotational speed and feed rate from this machining program as machining conditions and outputs them to the oscillating motion control unit 15. Furthermore, the second storage unit 16 and the position command generation unit within the oscillating motion control unit 15 (described later) may also be provided in the aforementioned host computer.

[0040] The oscillating motion control unit 15 controls the oscillating motion in the oscillating direction determined by the oscillating direction determination unit 14 according to the processing conditions. In order to control the oscillating motion, the oscillating motion control unit 15 is equipped with various functional units (not shown), such as a position command generation unit, an oscillating command generation unit, an overlap command generation unit, a learning control unit, and a position speed control unit.

[0041] The position command generation unit reads the machining conditions stored in the second storage unit 16 and generates position commands as movement commands for the motor 3 based on these machining conditions. Specifically, the position command generation unit generates position commands (movement commands) for each feed axis based on the relative rotational speed of the workpiece W and the tool T about the central axis of the workpiece W and the relative feed speed of the tool T and the workpiece W.

[0042] The swing command generation unit generates swing commands. The swing command generation unit can generate swing commands based on swing conditions and processing conditions, such as swing amplitude ratio and swing frequency ratio, or based on swing conditions such as swing amplitude and swing frequency. Specifically, the swing command generation unit generates swing commands based on the swing amplitude calculated by the swing amplitude calculation unit 13, and swing conditions such as the swing frequency, which is input from a host computer and stored in a second storage unit.

[0043] The overlap command generation unit calculates the difference between the position feedback detected by the encoder of the feed axis motor 3 and the position command, i.e., the position deviation. It then overlaps the calculated position deviation with the swing command generated by the swing command generation unit, thereby generating the overlap command. Alternatively, the swing command can be overlapped onto the position command instead of the position deviation.

[0044] The learning control unit calculates the correction amount for the overlap command based on the overlap command, adds the calculated correction amount to the overlap command, and thereby corrects the overlap command. The learning control unit has a memory that stores the oscillation phase and correction amount in association within one or more oscillation cycles. At a timing that compensates for the phase delay of the oscillation action corresponding to the responsiveness of the motor 3, the overlap command stored in the memory is read out and output as the correction amount. Even if there is no oscillation phase in the memory that can output the correction amount, the correction amount to be output can be calculated based on a correction amount close to the oscillation phase. Generally, the higher the oscillation frequency, the greater the positional deviation relative to the oscillation command; therefore, by performing correction through this learning control unit, the tracking accuracy for periodic oscillation commands can be improved.

[0045] The position and speed control unit generates a torque command for the motor 3 driving the feed axis based on the overlapping command after the correction amounts are added, and controls the motor 3 by means of the generated torque command. As a result, machining is performed while the tool T oscillates relative to the workpiece W.

[0046] Next, specific examples will be given to explain in more detail the oscillating cutting performed by the control device 1 of the machine tool in this embodiment.

[0047] Figure 4 This diagram illustrates a first example of oscillating cutting according to this embodiment. This first example is an instance where, within the range of oscillating directions capable of cutting chips, the oscillating direction is determined to be a oscillating amplitude A' smaller than the oscillating amplitude A of the oscillating motion along the machining path. From Figure 4 It can be seen that the swing amplitude A' of the changed swing direction, which can cut the chips, is smaller than the swing amplitude A of the swing motion along the machining path, thus reducing the load on the machine tool.

[0048] Figure 5 This diagram illustrates a second example of oscillating cutting in this embodiment. This second example demonstrates an oscillating direction determined by the direction perpendicular to the flank face T1 of the tool T, within the range of oscillating directions capable of cutting chips. From Figure 5 It can be seen that when the direction perpendicular to the back face T1 of tool T is taken as the swing direction, the swing amplitude A' that can cut the chips is much smaller than the swing amplitude A of the swing action along the direction of the machining path, which can minimize the load on the machine tool.

[0049] in addition, Figure 6 This diagram illustrates a third example of oscillating cutting according to this embodiment. This third example uses a cylindrical or cylindrical workpiece as the workpiece W, and within the range of oscillation directions capable of cutting chips, the oscillation direction is determined to be perpendicular to the flank face T1 of the tool T. According to... Figure 6It can be seen that even if the workpiece W does not have a tapered or arc-shaped portion, the feed axis is a specific axis (in Figure 6 When the Z-axis is used as the center, the oscillation amplitude A' that can cut the chips is much smaller when the direction perpendicular to the back face T1 of the tool T is set as the oscillation direction, which can minimize the load on the machine tool.

[0050] Thus, in the oscillating cutting of this embodiment, the shape of the workpiece W is not limited. That is, it can be applied whether the workpiece W has a tapered or arc-shaped portion on the machining surface and requires multiple feed axes (Z-axis and X-axis), or whether the workpiece W is cylindrical or cylindrical and a single feed axis (Z-axis) is sufficient. Therefore, the oscillating motion control unit 15 of this embodiment is configured to change the oscillating motion that oscillates multiple feed axes or only oscillates a single axis among the multiple feed axes to an oscillating motion with a oscillating direction determined by the oscillating direction determination unit 14.

[0051] According to this embodiment, the following effects are achieved.

[0052] In this embodiment, the control device 1 of the machine tool is configured to include: an approach angle acquisition unit 12, which acquires the approach angle of the tool T; an oscillation amplitude calculation unit 13, which calculates the oscillation amplitude required for chip breaking in any oscillation direction based on the approach angle of the tool T; an oscillation direction determination unit 14, which determines the oscillation direction based on the calculation result of the oscillation amplitude calculation unit 13; and an oscillation action control unit 15, which controls the oscillation action of the oscillation direction determined by the oscillation direction determination unit 14 based on the processing conditions.

[0053] In conventional oscillating cutting, after determining the oscillation direction, the oscillation amplitude capable of cutting chips is calculated. In contrast, in this embodiment, the oscillation direction is determined based on the calculated oscillation amplitude after calculating the oscillation amplitude capable of cutting chips in any number of oscillation directions. This represents a significant difference between the two methods. Therefore, according to this embodiment, it is possible to select and determine an oscillation direction with an amplitude smaller than that of the oscillation motion along the machining path, thereby reducing the load on the machine tool. Furthermore, according to this embodiment, the load on the machine tool can be reduced universally regardless of the machine tool's structure.

[0054] Furthermore, in this embodiment, the oscillation is configured such that, within the range of oscillation directions capable of cutting chips, the oscillation amplitude is smaller than that of an oscillation motion along the machining path. Therefore, compared to conventional oscillation motions along the machining path, chips can be cut more efficiently, and the load on the machine tool is reduced more reliably.

[0055] Furthermore, in this embodiment, the tool is configured to oscillate in a direction perpendicular to the flank face T1 of the tool T. This allows for chip reduction compared to conventional oscillation along the machining path, and further reliably reduces the load on the machine tool, minimizing the overall load.

[0056] Furthermore, in this embodiment, the oscillation motion control unit 15 is configured to change the oscillation motion from oscillating only one specific axis among multiple feed axes to oscillation motion with a oscillation direction determined by the oscillation direction determination unit 14. Thus, according to this embodiment, it can be applied not only when multiple feed axes (Z-axis and X-axis) are required because the workpiece W has a tapered or arc-shaped portion on the machining surface, but also when the workpiece W is cylindrical or cylindrical and a single feed axis (Z-axis) is sufficient, achieving the aforementioned effects.

[0057] Furthermore, this disclosure is not limited to the above-described manner, and variations and improvements within the scope of achieving the purpose of this disclosure are included in this disclosure.

[0058] Symbol Explanation

[0059] 1. Machine tool control device

[0060] 11 First Storage Section

[0061] 12-angle entry point

[0062] 13 Oscillation Amplitude Calculation Section

[0063] 14. Swing Direction Determination Unit

[0064] 15 Swing motion control unit

[0065] 16 Second Storage Section

[0066] 3 electric motors

[0067] S-spindle

[0068] T tools

[0069] W workpiece

[0070] W1 conical section

[0071] θ1 is the angle of entry.

Claims

1. A control device for a machine tool, which causes the tool and workpiece to oscillate relative to each other to perform oscillating cutting, characterized in that, The control device includes: The angle-of-entry unit acquires the angle of entry of the tool. The oscillation amplitude calculation unit calculates the oscillation amplitude required to cut chips in any oscillation direction based on the cutting angle of the tool. The swing direction determination unit determines the swing direction based on the swing amplitude calculated in the swing amplitude calculation unit; and The swing motion control unit controls the swing motion in the swing direction determined by the swing direction determination unit based on processing conditions. The swing direction determining unit determines a swing direction whose swing amplitude is smaller than that of a swing motion along the processing path, within the range of swing directions capable of cutting chips.

2. A control device for a machine tool, which causes the tool and workpiece to oscillate relative to each other to perform oscillating cutting, characterized in that, The control device includes: The angle-of-entry unit acquires the angle of entry of the tool. The oscillation amplitude calculation unit calculates the oscillation amplitude required to cut chips in any oscillation direction based on the cutting angle of the tool. The swing direction determination unit determines the swing direction based on the swing amplitude calculated in the swing amplitude calculation unit; and The swing motion control unit controls the swing motion in the swing direction determined by the swing direction determination unit based on processing conditions. The swing direction determining unit determines the swing direction as the direction perpendicular to the back face of the tool, wherein the back face of the tool is the workpiece side of the tool tip and the machining direction side.

3. The machine tool control device according to claim 1 or 2, characterized in that, The swing motion control unit changes the swing motion from swinging only one specific axis among multiple feed axes to swinging in the direction determined by the swing direction determination unit.

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