Machine tool control device

Abstract

To determine a cutting-in amount and a feeding speed for effectively suppressing chatter vibrations.SOLUTION: A control device 10 of a lathe comprises: an input part 4 to which information concerning a tool is inputted; a regenerative width calculating part 5 that calculates a relation among a regenerative width that is a cutting region that overlaps with a processed surface not yet rotated once during cutting processing, a cutting-in amount of the tool into a work-piece and a feeding speed of the tool, using the information inputted to the input part 4; and an instability calculating part 6 that calculates instability with respect to chatter vibrations, on the basis of the regenerative width determined by the regenerative width calculating part 5 and specific cutting resistance.SELECTED DRAWING: Figure 4

Description

[Technical field]

[0001] The present disclosure relates to a control device that is provided in a machine tool and controls cutting processing. [Background technology]

[0002] Some machine tools are equipped with a load monitor function that displays the load on the spindle motor and feed axis motor on the display. The load monitor function allows the operator to check the load on the machine during processing, so that by adjusting the cutting depth, feed speed, and rotation speed, heat generation and machine stoppage due to overload can be avoided. Also, some machines are equipped with an optimum rotation speed display function that analyzes the frequency of chatter vibration measured by a vibration sensor, and calculates the rotation speed at which chatter vibration is unlikely to occur using the frequency and rotation speed information, and displays it on the display unit (see Patent Document 1, for example). The optimum rotation speed display function allows even an inexperienced operator to know the optimum rotation speed for chatter vibration, so that chatter vibration can be easily suppressed by adjusting the rotation speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2012-91249 A Summary of the Invention [Problem to be solved by the invention]

[0004] The optimum rotation speed display function can obtain the optimum rotation speed for reducing chatter vibration, but cannot obtain the optimum cutting depth and feed rate for reducing chatter vibration. Furthermore, because chatter vibration is not necessarily more likely to occur as the machining load increases, the load value displayed by the load monitor function cannot be used as a reference when adjusting the cutting depth and feed speed to suppress chatter vibration.

[0005] Therefore, an object of the present disclosure is to provide a control device for a machine tool that can determine the cutting depth and feed rate for effectively suppressing chatter vibration. [Means for solving the problem]

[0006] In order to achieve the above object, the present disclosure provides a control device for a machine tool that cuts a workpiece while rotating a tool or a workpiece and feeding the tool in a predetermined feed direction, comprising: At least material information of the workpiece and shape information of the tool An input unit for inputting; The input to the input section The shape information Using When the cutting depth of the tool into the workpiece and the feed speed of the tool are changed, a regeneration width calculation unit that calculates a regeneration width, which is a width in the feed direction in a cutting area that overlaps with a machining surface one rotation before during cutting; The reproduction width calculated by the reproduction width calculation unit; , determined by the material of the workpiece and the cutting depth and the feed speed when the regeneration width is calculated and an instability calculation unit that calculates the instability with respect to chatter vibration based on the specific cutting resistance. Another aspect of the present disclosure is characterized in that, in the above configuration, the instability calculation unit calculates the instability by the product or sum of the regeneration width and the specific cutting resistance. Another aspect of the present disclosure is characterized in that, in the above configuration, a display unit is provided that displays the degree of instability together with a relationship with the cutting depth and the feed speed. Another aspect of the present disclosure is characterized in that, in the above configuration, the display unit also displays at least one of a theoretical roughness of the machined surface calculated from shape information of the tool and the feed speed, and a cutting cross-sectional area calculated from the cutting depth and the feed speed. Another aspect of the present disclosure is characterized in that, in the above configuration, the display unit displays the instability corresponding to the cutting depth and the feed rate, the theoretical roughness, and the cutting cross-sectional area in graphs, and when a specified position on the graph is selected, the cutting depth and the feed rate corresponding to that position are reflected in the machining program. Another aspect of the present disclosure is characterized in that, in the above configuration, when at least one of the cutting cross-sectional area and the machined surface roughness is input to the input section as input information, the cutting depth and the feed rate are automatically reflected in the machining program so as to be equal to or less than a predetermined instability value and in accordance with the input information. Effect of the Invention

[0007] According to the present disclosure, the degree of instability with respect to chatter vibration is calculated from the cutting depth and feed speed of the tool, so that the cutting depth and feed speed for effectively suppressing chatter vibration can be selected based on the obtained degree of instability. In particular, according to another embodiment in which the instability is calculated by the product or sum of the regeneration width and the specific cutting resistance, the instability can be easily obtained. According to another aspect having a display unit that displays the degree of instability together with the relationship between the depth of cut and the feed rate, in addition to the above effects, the operator can easily adjust the depth of cut and the feed rate, which have low instability, to optimal values, and can easily suppress chatter vibration. According to another aspect in which the display unit displays the theoretical roughness of the machined surface calculated from the tool shape information and the feed rate, and the cutting cross-sectional area calculated from the cutting depth and the feed rate, in addition to the above effects, the theoretical roughness and the cutting cross-sectional area after changing the cutting depth and the feed rate can be easily understood, which makes it easier to maintain and improve quality and processing efficiency. According to another aspect in which the display unit displays the instability, theoretical roughness, and cutting cross-sectional area corresponding to the cutting depth and feed rate in a graph, and when a specific position on the graph is selected, the cutting depth and feed rate corresponding to that position are reflected in the machining program, in addition to the above effects, it is possible to easily select the cutting depth and feed rate that are less likely to cause chatter vibration. According to another aspect in which, when at least one of the cutting cross-sectional area and the machined surface roughness is input to the input section as input information, a cutting depth and feed rate that are equal to or less than a predetermined instability value and correspond to the input information are automatically reflected in the machining program, in addition to the above effects, cutting is automatically performed with a cutting depth and feed rate that are unlikely to cause chatter vibration, improving machining efficiency and reducing the input work of the operator. [Brief description of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic diagram of peripheral cutting on a lathe. [Diagram 2] FIG. 1 is a schematic diagram showing the relationship between the specific cutting resistance in the thrust force direction, the cutting depth, and the feed rate. [Diagram 3] FIG. 4 is a schematic diagram showing the relationship between the reproducing width, the cutting depth, and the feed speed. [Figure 4] FIG. 2 is a block diagram of a control device. [Diagram 5] 10 is a schematic diagram showing the instability of chatter vibration calculated by an instability calculation unit. FIG. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0009] Hereinafter, an embodiment of the present disclosure will be described with reference to the drawings. Fig. 1 is a schematic diagram of peripheral cutting in a lathe M, which is an example of a machine tool. This shows how, with a well-known machine configuration, a tool 2 cuts into a rotating workpiece 1 in the radial direction of the spindle and feeds it in the spindle direction to machine the outer diameter of the workpiece 1 into a cylindrical shape. In Fig. 1, a is the cutting depth, f is the feed rate, R is the nose of tool 2, b is the cutting width, b d is the regeneration width (the cutting area overlapping with the machining surface from one rotation before). As shown in Fig. 1, the regeneration width b d can be calculated geometrically using the cutting depth a, feed rate f, and nose R. Figure 2 shows the specific cutting resistance K r 2 is a schematic diagram showing the relationship between the cutting force a and the feed rate f. rbecomes larger as the cutting depth a becomes smaller and as the feed rate f becomes smaller. Figure 3 shows the playback width b d FIG. 3 is a schematic diagram showing the relationship between the cutting width a, the feed rate f, and the feed rate f. Note that the nose R is one of the parameters of the tool 2, and is known when the operator adjusts the processing conditions, so it is not considered a variable here. As shown in FIG. 3, the regeneration width b d becomes larger as the cutting depth a becomes larger and as the feed rate f becomes smaller.

[0010] 4 shows an example of the configuration of the control device 10 of the present disclosure. The control device 10 here is configured in an NC device of a lathe M. The control device 10 includes a storage unit 3, an input unit 4, a playback width calculation unit 5, an instability calculation unit 6, and a display unit 7. The memory unit 3 stores information on the material of the workpiece 1 input by the operator from the input unit 4, information on the tool shape such as the nose R, and the specific cutting resistance K r The relationship between the cutting depth a and the feed rate f is stored. The reproduction width calculation unit 5 reads the information stored in the memory unit 3 and calculates the reproduction width b based on the tool shape. d The calculation is performed to obtain the playback width b d The relationship between the cutting depth a and the feed rate f is calculated. The instability calculation unit 6 calculates the specific cutting resistance K r and the reproduction width b calculated by the reproduction width calculation unit 5. d The instability with respect to chatter vibration is calculated by multiplying this by

[0011] FIG. 5 is a schematic diagram showing the instability of chatter vibration calculated by the instability calculation unit 6. The horizontal axis shows the cutting depth a, the first vertical axis shows the feed rate f, and the second vertical axis shows the theoretical roughness of the machined surface calculated from the nose R and the feed rate f. The specific cutting resistance K r and playback width b dThe product of these is shown in a color map as the instability. Also, the cutting cross-sectional area calculated from the cutting depth a and the feed rate f is shown using contour lines. The color map of instability increases as the color gets darker, indicating that the upper limit is maximum and the lower limit is 0. The display unit 7 displays a graph as shown in Figure 5. Therefore, the operator inputs an appropriate cutting depth a and feed rate f from the input unit 4 by selecting a position on the graph or by directly inputting numerical values ​​based on the instability displayed on the display unit 7. Then, the control device 10 reflects the input cutting depth a and feed rate f in the machining program and performs machining.

[0012] As described above, the control device 10 of the lathe M of the above embodiment uses the input unit 4 for inputting information related to the tool 2 and the information input to the input unit 4 to determine the regeneration width b d A regeneration width calculation unit 5 calculates the relationship between the cutting depth a of the tool 2 into the workpiece 1 and the feed speed f of the tool 2, and the regeneration width b calculated by the regeneration width calculation unit 5. d and specific cutting resistance K r and an instability calculation unit 6 that calculates the instability with respect to chatter vibration based on the above. According to this configuration, the degree of instability with respect to chatter vibration is calculated from the cutting depth a and feed rate f of the tool 2, so that the cutting depth a and feed rate f for effectively suppressing chatter vibration can be selected based on the obtained degree of instability.

[0013] In particular, since the display unit 7 displays the degree of instability along with the relationship between the cutting depth a and the feed speed f, the operator can easily adjust the cutting depth a and feed speed f to optimal values ​​that have low instability (are less likely to cause chatter vibration), and can easily suppress chatter vibration. In addition, the display unit 7 displays the theoretical roughness of the machined surface calculated from the shape information of the tool 2 and the feed rate f, and the cutting cross-sectional area calculated from the cutting depth a and the feed rate f, so that the theoretical roughness and cutting cross-sectional area after changing the cutting depth a and the feed rate f can be easily seen. This makes it easier to maintain and improve quality and processing efficiency. Furthermore, the display unit 7 displays the instability, theoretical roughness, and cutting cross-sectional area corresponding to the cutting depth a and feed rate f in a graph. When a specific position on the graph is selected, the cutting depth a and feed rate f corresponding to that position are reflected in the machining program, making it easy to select the cutting depth a and feed rate f that are less likely to cause chatter vibration.

[0014] Modifications of the present disclosure will be described below. In the above embodiment, the instability is the product of the reclaimed width and the specific cutting resistance, but the sum of the reclaimed width and the specific cutting resistance may be used as the instability. In this way, the instability can be easily obtained by calculating the product or sum of the reclaimed width and the specific cutting resistance. However, the instability may be calculated by another calculation formula including the reclaimed width and the specific cutting resistance. In the above embodiment, both the theoretical roughness and the cutting cross-sectional area of ​​the machined surface are displayed on the display unit, but only one of them or neither may be displayed. The instability may be displayed alone without being displayed together with the cutting depth and the feed rate. In the graph display on the display unit, the range of the color map (upper and lower limits) can be set arbitrarily. The color is not limited to a stepped display using squares, and can be changed continuously like a gradation. Of course, graph formats other than the above can also be used.

[0015] In the above embodiment, the cutting depth and feed rate are selected by the operator on the graph displayed on the display unit, and are reflected in the machining program, but it is not limited to being triggered by the operator's setting, and when at least one of the cutting cross-sectional area determined by the machining load and the required machined surface roughness is input into the input unit, the cutting depth and feed rate that are equal to or less than a predetermined instability value and correspond to the input information may be automatically determined and reflected in the machining program. In this way, cutting is automatically performed with the cutting depth and feed rate that are unlikely to cause chatter vibration, improving machining efficiency and reducing the input work of the operator. The present invention is also applicable to machine tools other than lathes. [Explanation of symbols]

[0016] 1 workpiece, 2 tool, 3 memory section, 4 input section, 5 playback width calculation section, 6 instability calculation section, 7 display section, M lathe, a cutting depth, f feed rate, R nose, b cutting width, b d ·Play width, K r ·Specific cutting force.

Claims

1. A control device for a machine tool that cuts a workpiece while rotating a tool or a workpiece and feeding the tool in a predetermined feed direction, comprising: An input unit that inputs at least material information of the workpiece and shape information related to the tool; a reproduction width calculation unit that calculates a reproduction width, which is a width in the feed direction in a cutting area that overlaps with a machining surface one rotation before during cutting processing, when a cutting amount of the tool into the workpiece and a feed speed of the tool are changed, using the shape information input to the input unit; An instability calculation unit that calculates an instability against chatter vibration based on the regeneration width calculated by the regeneration width calculation unit, the material of the workpiece, and a specific cutting resistance determined by the cutting depth and the feed rate when the regeneration width is calculated; A control device for a machine tool comprising:

2. 2. The control device for a machine tool according to claim 1, wherein the instability calculation unit calculates the instability by a product or sum of the regeneration width and the specific cutting resistance.

3. 3. The control device for a machine tool according to claim 1, further comprising a display unit that displays the degree of instability together with a relationship between the cutting depth and the feed rate.

4. The control device for a machine tool according to claim 3, characterized in that the display unit also displays at least one of a theoretical roughness of the machined surface calculated from the shape information of the tool and the feed rate, and a cutting cross-sectional area calculated from the cutting depth and the feed rate.

5. The control device for a machine tool according to claim 4, characterized in that the display unit displays the instability corresponding to the cutting depth and the feed rate, the theoretical roughness, and the cutting cross-sectional area in a graph, and when a specified position on the graph is selected, the cutting depth and the feed rate corresponding to that position are reflected in the machining program.

6. A control device for a machine tool as described in claim 1 or 2, characterized in that when at least one of a cutting cross-sectional area and a machined surface roughness is input to the input section as input information, the cutting depth and the feed rate are automatically reflected in the machining program so as to be equal to or less than a predetermined instability value and in accordance with the input information.

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