Diagnostic device

Abstract

The invention provides a diagnostic device which does not need to collect machine tool data which is a main cause of a machining error during machining and can easily and reliably diagnose the cause of the machining error even by an experienced operator. The diagnostic device is provided with: an error transition recording unit (2) in which a plurality of types of displacement data (A-F) are recorded; an error transition input unit (3) that selects one piece of displacement data from among the plurality of types of displacement data (A-F); an error cause recording unit (9) in which a plurality of causes are recorded in association with each of the displacement data (A-F); a cause diagnosis unit (6) that refers to the error cause recording unit (9) and specifies a cause on the basis of the displacement data selected by the error transition input unit (3); and a display unit (7) that displays the cause specified by the cause diagnosis unit (6).

Description

Technical Field

[0001] The present invention relates to a diagnostic device for diagnosing the cause of a machining error in a workpiece machined by a machine tool such as a numerical control device. Background Art

[0002] When using a measuring instrument to check the size and shape of a workpiece processed by a machine tool, if the processing error is large, it is necessary to investigate the cause and take countermeasures. As the cause of such processing errors, multiple reasons are considered, such as poor machine tool accuracy, thermal displacement, tool wear, measurement error of the processing origin, and measurement error of the tool offset correction value. Therefore, as a general investigation, the operator of the machine tool first confirms the processing origin, the measurement error of the tool offset correction value, tool wear, etc. And, if there is no problem with them, the manufacturer checks the positioning accuracy of the machine tool by checking the laser length meter, or measures the reversal protrusion in the double ball bar device, etc., to implement the accuracy inspection of the machine tool. Therefore, the investigation of the cause of the processing error is mostly time-consuming.

[0003] Therefore, in order to diagnose the cause of the machining error in a short time, in the diagnosis device described in Patent Document 1, the cause of the machining error is classified into multiple types in the form of tool causes including tool wear, machine tool causes including poor machine tool accuracy, and fixture causes including poor fixation of the workpiece, and the feature quantity of the machine tool data and the measurement data of the workpiece is extracted and stored for each cause. In addition, when the detected amount of the machine tool data and the measurement data of the workpiece detected during machining is close to the pre-stored feature quantity, it is determined that the cause corresponding to the feature quantity is the cause of the machining error, thereby enabling the cause of the machining error to be diagnosed in a short time. In addition, in the diagnosis device described in Patent Document 2, the thermal displacement caused by the internal heat source of the machine tool and the thermal displacement caused by the change in ambient temperature are respectively calculated, and the tool offset correction value, temperature, and timing of the thermal displacement correction amount related to each thermal displacement are displayed in a graph. In addition, by confirming the graphical display, the operator can easily know whether the actual thermal displacement and tool wear are consistent with the operator's empirical feeling.

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2019-206056

[0007] Patent Document 2: Japanese Patent No. 6001211 Summary of the invention

[0008] Problems to be solved by the invention

[0009] However, in the diagnostic devices described in Patent Documents 1 and 2, it is necessary to collect the data of the machine tool during processing, so the overall scale of the device becomes large, which can be said to have a problem in terms of cost. In addition, in particular, in the diagnostic device described in Patent Document 2, it can be said that information related to the current processing is displayed, and sufficient experience is required to diagnose the cause of the processing error based on this display, so there is also a problem that it is difficult for operators with little experience to diagnose the cause.

[0010] Therefore, the present invention is completed in view of the above-mentioned problems, and its purpose is to provide a diagnostic device that does not need to collect machine tool data that is the main cause of machining errors during machining, and even an inexperienced operator can easily and reliably diagnose the cause of machining errors.

[0011] Means for solving problems

[0012] In order to achieve the above-mentioned purpose, the invention described in technical solution 1 of the present invention is a diagnostic device, which is used to diagnose the cause of processing errors generated each time each workpiece of the same shape is processed, wherein the diagnostic device is provided with: an error shift recording unit, which records a plurality of error shift information with different timing shifts of the processing errors accompanying repeated processing; an error shift input unit, which selects one or more error shift information from the plurality of error shift information; an error cause recording unit, in which a plurality of causes are recorded corresponding to the error shift information respectively; a cause diagnosis unit, which refers to the error cause recording unit and determines the cause based on the error shift information selected by the error shift input unit; and a display unit, which displays the cause determined by the cause diagnosis unit.

[0013] The invention described in Technical Solution 2 is the invention described in Technical Solution 1, wherein the diagnostic device is provided with: a processing part input unit, which inputs processing part information, which is information related to the determination of the processing error in the workpiece; and a processing condition input unit, which inputs processing condition information, which is information related to the processing of the workpiece, and the cause also corresponds to the processing part information and the processing condition information, and the cause diagnosis unit refers to the error cause recording unit, and determines the cause based on the error shift information selected by the error shift input unit, the processing part information input by the processing part input unit, and the processing condition information input by the processing condition input unit.

[0014] The invention described in Technical Solution 3 is the invention described in Technical Solution 2, wherein the diagnostic device is connected to a numerical control device, and at least either one of the processing location information and the processing condition information can be selected and input from data recorded in the numerical control device.

[0015] The invention described in technical solution 4 is the invention described in any one of technical solutions 1 to 3, wherein the error shift input unit can input the measured value of the timing shift of the processing error, and the error shift input unit calculates the processing error of the initially processed workpiece from the target value, i.e., the first-piece processing error Δa, the absolute value Δb of the displacement amplitude of the processing error generated between the initially processed workpiece and the last processed workpiece, the maximum value Δc of the difference between the processing error in the previous processing and the processing error in this processing, the error Δd from the straight line approximation, and at least one of the error Δe from the first-order lag approximation, as feature quantities related to the selection of the error shift information, and selects the error shift information based on the calculated feature quantities.

[0016] In addition, the timing shift of the machining error accompanying repeated machining in the present invention is not limited to the shift that associates the machining error generated by each machining with the machining time, but also includes the shift that associates the machining error generated by each machining with the number of machining times, and the shift that associates the machining error generated by each machining with the number of machinings. In addition, the machining error in the invention described in claim 1 includes, in addition to the error generated in the workpiece, for example, the error of the tool length deviation measured by the tool sensor, the error of the machining origin of the workpiece measured by the probe, etc.

[0017] Effects of the Invention

[0018] According to the present invention, an error transition recording unit is provided, which records a plurality of error transition information with different timing transitions of machining errors accompanying repeated machining; an error transition input unit selects one or more error transition information from the plurality of error transition information; an error cause recording unit, in which a plurality of causes are recorded in correspondence with the error transition information; a cause diagnosis unit refers to the error cause recording unit and determines the cause based on the error transition information selected by the error transition input unit; and a display unit displays the cause determined by the cause diagnosis unit, so that the operator can grasp the cause of the machining error by only selecting the error transition information similar to the current machining status. Therefore, even an operator with little experience can easily and reliably diagnose the cause of the machining error. In addition, it is not necessary to collect machine tool data that is the main cause of the machining error during machining, so that the diagnostic device can be made low-cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0019] Figure 1 It is a block diagram showing the structure of the diagnostic device.

[0020] Figure 2 This is an explanatory diagram showing the shape of a workpiece.

[0021] Figure 3 It is an explanatory diagram showing the timing transition of various machining errors recorded in the error transition recording unit.

[0022] Figure 4 It is an explanatory diagram showing a display mode on a display unit of a diagnostic device.

[0023] Figure 5 It is an explanatory diagram showing an example of a change in the display mode in the display unit.

[0024] Figure 6 This is an explanatory diagram showing a method of processing a workpiece.

[0025] Figure 7 This table associates the causes of machining errors with the machining locations, tool types, and displacement data.

[0026] Figure 8 It is an explanatory diagram showing the timing transition of machining errors obtained in actual machining.

[0027] Description of Reference Numerals

[0028] 1··Diagnostic device, 2··Error shift recording unit, 3··Error shift input unit, 4··Processing part input unit, 5··Processing condition input unit, 6··Cause diagnosis unit, 7··Display unit, 8··CNC device, 9··Error cause recording unit, 11··Workpiece. DETAILED DESCRIPTION

[0029] Hereinafter, a diagnostic device as one embodiment of the present invention will be described in detail based on the drawings.

[0030] Figure 1 It is a block diagram showing the structure of the diagnostic device 1. Figure 2 It is an explanatory diagram showing a shape diagram of the workpiece 11 . Figure 3 It is an explanatory diagram showing the timing transition of various types of machining errors recorded in the error transition recording unit 2 . Figure 4 It is an explanatory diagram showing a display mode on the display unit 7 of the diagnostic device 1 . Figure 5 It is an explanatory diagram showing an example of a change in the display mode on the display unit 7. Figure 6 It is an explanatory diagram showing a method of processing the workpiece 11. Figure 7 This table associates the causes of machining errors with the machining locations, tool types, and displacement data. Figure 8 It is an explanatory diagram showing the timing transition of machining errors obtained in actual machining.

[0031] First, assume that the workpiece in this embodiment is Figure 2 The workpiece 11 shown. In addition, the machining error in this embodiment is the error relative to the target value Yo when the target value of the distance L between the holes 12 and 13 in the Y-axis direction is Yo for the holes 12 and 13 penetrating the upper surface of the workpiece 11. In addition, Figure 2 The X-axis direction is the left-right direction, the Y-axis direction is the front-back direction, and the Z-axis direction is the up-down direction.

[0032] In addition, the hole 12 and the hole 13 are processed as follows. First, the drill 31 provided in the numerical control (NC: Numeric Control) device 8 is moved to the coordinates of the X-axis and the Y-axis corresponding to the hole 12 and positioned. Then, the drill 31 is fed in the Z-axis direction to cut the hole 12. Next, the drill 31 is moved to the coordinates of the X-axis and the Y-axis corresponding to the hole 13 and positioned, and then fed in the Z-axis direction to cut the hole 13. Then, when the processing of the hole 12 and the hole 13 of one workpiece 11 is completed, a new workpiece 11 is replaced and the same processing is repeated.

[0033] If the above-mentioned processing of setting the holes 12 and 13 in the workpiece 11 is repeated, a processing error will naturally occur in each processing. And the timing of the processing error accompanying such repeated processing, that is, the displacement data becomes, for example, Figure 3 The graphs shown in (A) to (F) are shown. The dotted line in the center of each graph represents the target value Yo of the distance L. In addition, δ in each graph represents the machining error of the initially processed workpiece 11 (hereinafter referred to as the first piece) relative to the target value Yo. Furthermore, ΔY in each graph represents the displacement amplitude of the machining error generated from the first piece to the last processed workpiece 11 (hereinafter referred to as the final piece), that is, the difference between the minimum machining error and the maximum machining error. Based on Figure 3 The information in the graphs shown in (A) to (F) (hereinafter, referred to as displacement data A to F) is the error transition information in the present embodiment.

[0034] Here, the characteristics of the timing transition of the machining error of the workpiece 11 will be described.

[0035] The displacement data of the timing of machining error is as follows Figure 3 There are various forms as shown in (A) to (F). Displacement data A is a form in which the processing error δ of the first piece is large and the displacement amplitude ΔY is small. In addition, displacement data B, C, D, and E are forms in which the processing error δ of the first piece is small but the displacement amplitude ΔY is large. Furthermore, displacement data F is a form in which the processing error δ of the first piece is small and the displacement amplitude ΔY is also small, that is, a form in which the overall processing error is small.

[0036] In addition, displacement data B, C, D, and E can be classified according to the characteristics related to the timing of each processing error and the shift of the displacement amplitude ΔY. Displacement data B is a form in which each processing error changes irregularly in a short period of time. Displacement data C is a form in which the displacement amplitude ΔY changes over time, and here it is an increasing form. Displacement data D is a form in which after the displacement amplitude ΔY changes greatly during the initial processing, each processing error is stable in the changed state, and then the displacement amplitude ΔY is also stable. Displacement data E is not a form of short-term change like displacement data B, but a form in which each processing error continues to change unstably from the beginning to the end of processing.

[0037] Furthermore, a method of selecting similar displacement data from displacement data obtained by actual processing will be described.

[0038] As a result of repeatedly continuing the above-mentioned processing of setting the holes 12 and 13 in the workpiece 11, Figure 8 In the case of the displacement data shown, displacement data B is selected as the displacement data that represents the closest feature among the displacement data A to F. That is, displacement data B can be selected as a form in which the machining error δa of the first piece is small, but the displacement amplitude ΔYa from the first piece to the final piece is large, and each machining error changes irregularly in a short time as time passes.

[0039] To explain in more detail, the displacement data is selected by classification based on the error transition of the following characteristic quantity. In the present disclosure, the first-piece machining error δ (first-piece machining error Δa), the absolute value Δb of the displacement width ΔY, the maximum value Δc of the difference between the machining error in the previous machining and the machining error in the current machining, the error Δd from the linear approximation, and the error Δe from the first-order lag approximation are used as characteristic quantities. If the first-piece machining error Δa exceeds a predetermined judgment value J1 (first error transition), the displacement data A is selected. In addition, if the absolute value Δb of the displacement width ΔY exceeds a predetermined judgment value J2 and the maximum value Δc of the difference between the previous and current machining errors also exceeds a predetermined judgment value J3 (third error transition), the displacement data B is selected. In addition, if the absolute value Δb of the displacement width ΔY exceeds the judgment value J2 but the error Δd from the linear approximation is less than a predetermined judgment value J4 (fourth error transition), the displacement data C is selected. In addition, if the absolute value Δb of the displacement amplitude ΔY exceeds the determination value J2 but the error Δe from the first-order lag formula approximation value is less than the predetermined determination value J5 (fifth error transition), the displacement data D is selected. In addition, if the absolute value Δb of the displacement amplitude ΔY exceeds the determination value but the maximum value Δc of the difference between the previous and current machining errors is less than the determination value J3, and the error Δd from the straight line approximation value and the error Δe from the first-order lag formula approximation value are greater than the determination values ​​J4 and J5, respectively (sixth error transition), the displacement data E is selected. In addition, if the first-piece machining error Δa and the absolute value Δb of the displacement amplitude ΔY are both smaller than the respective determination values ​​J1 and J2 (second error transition), the displacement data F is selected.

[0040] So, for example, when we get Figure 8 In the case of the displacement data shown, it is assumed that the absolute value Δb of the displacement width ΔY exceeds the judgment value J2, and the maximum value Δc of the difference between the previous and current machining errors also exceeds the judgment value J3. In this case, as described above, Figure 8 The displacement data shown is classified as the third error shift, and therefore the displacement data B is selected.

[0041] In addition, in this embodiment, as described later, the operator selects similar displacement data. However, as described as a modified example, the diagnosis device may also be configured to automatically select similar displacement data.

[0042] Based on the above, the diagnosis of the cause of the machining error by the diagnosis device 1 will be described.

[0043] The diagnostic device 1 includes an error shift recording unit 2 for recording displacement data A to F, and a display unit 7 for displaying the displacement data A to F. In addition, the diagnostic device 1 includes an error shift input unit 3 for selecting displacement data to be displayed on the display unit 7, and a processing location input unit 4 for selecting a processing location corresponding to the shape of the workpiece 11. Figure 1The processing condition input unit 5 is used to input the processing position; and the processing condition input unit 5 is used to input the processing conditions such as the spindle speed, the spindle feed speed and the type of tool used in the processing. In addition, the diagnostic device 1 is provided with an error cause recording unit 9 for recording the cause of the processing error. In the error cause recording unit 9, if Figure 7 As shown in the table, various causes previously assumed as causes of machining errors are recorded in correspondence with machining locations, types of tools, and displacement data. In addition, the diagnostic device 1 is provided with a cause diagnosis unit 6, which diagnoses the cause of the machining error based on the information input by the error shift input unit 3, the machining location input unit 4, and the machining condition input unit 5 and the information recorded in the error cause recording unit 9.

[0044] In addition, in the display unit 7, the displacement data and the like are displayed in the form of Figure 4 The display unit 7 is provided with: an error position display unit 22 for displaying the shape diagram of the workpiece 11 and the processing position and the error position where the processing error occurs; an error shift display unit 23 for displaying the displacement data A to F recorded in the error shift recording unit 2; and a processing condition display unit 24 for displaying the processing conditions including the type of tool, etc. In addition, the display unit 7 is provided with: a diagnosis start button 25 for starting the diagnosis of the cause of the processing error after the processing position and processing conditions are input and the displacement data are selected; and an error cause display unit 26 for displaying the diagnosis result of the cause diagnosis unit 6, that is, the cause of the processing error determined by the cause diagnosis unit 6.

[0045] And, it shows that in the current processing Figure 8 In the specific example of the cause diagnosis of the machining error of the above-mentioned diagnostic device 1 in the case of the displacement data shown, first, the operator inputs the shape diagram of the workpiece 11 through the machining part input unit 4, and selects the hole 12 and the hole 13. Then, the distance in the X-axis direction and the distance in the Y-axis direction are displayed on the error part display unit 22 as the distance between the holes 12 and 13 that have caused the machining error. Therefore, the operator inputs through the machining part input unit 4 that the machining error that the operator wants to diagnose the cause of this time is the machining error related to the distance L in the Y-axis direction. In addition, the diagnostic device 1 can also be connected to the numerical control device 8, and the input of the shape diagram of the workpiece 11 can be selected from the shape diagram of the workpiece stored in the numerical control device 8 in advance.

[0046] Next, the operator selects a feature and a displacement data A to F displayed on the error transition display unit 23 through the error transition input unit 3. Figure 8The displacement data B closest to the displacement data shown in FIG. 1 is selected. Furthermore, the operator inputs the spindle speed, the spindle feed speed, and the type of tool used in the machining through the machining condition input unit 5. The machining conditions input at this time are displayed on the machining condition display unit 24. In addition, the machining conditions can also be input by connecting the diagnostic device 1 and the numerical control device 8 to select from the machining program information pre-stored in the numerical control device 8.

[0047] When the above input is completed, the operator presses the diagnosis start button 25 on the display unit 7. Then, the cause diagnosis unit 6 refers to Figure 7 In the table shown in FIG. 1 , the error cause is determined to be "vibration of the tool" based on the information input from the processing part input unit 4, the displacement data selected from the error transition input unit 3, and the information input from the processing condition input unit 5, and is displayed as "vibration of the tool" in the error cause display unit 26 as a result of the error diagnosis. Therefore, the operator can determine that the cause of the processing error is "vibration of the tool" by referring to the error cause display unit 26.

[0048] According to the diagnostic device 1 having the above structure, there are provided: an error shift recording unit 2 recording a plurality of displacement data A to F; an error shift input unit 3 selecting a displacement data from the plurality of displacement data A to F; an error cause recording unit 9 recording a plurality of causes corresponding to the displacement data A to F; a cause diagnosis unit 6 determining the cause based on the displacement data selected by the error shift input unit 3 with reference to the error cause recording unit 9; and a display unit 7 displaying the cause determined by the cause diagnosis unit 6, so that the operator can grasp the cause of the machining error only by selecting the displacement data similar to the current machining condition. Therefore, even an operator with little experience can easily and reliably diagnose the cause of the machining error. In addition, since it is not necessary to collect the machine tool data that is the main cause of the machining error during machining, the diagnostic device 1 can be made at a low cost.

[0049] In addition, the diagnostic device 1 is provided with: a processing part input unit 4 for inputting processing part information, the processing part information including the shape diagram of the workpiece 11 and the processing part, etc., the processing part information is information related to the determination of the processing error; and a processing condition input unit 5 for inputting processing condition information, the processing condition information including the spindle speed during processing, the spindle feed speed, and the type of tool used in processing, etc., the processing condition information is information related to the processing of the workpiece 11, and the cause of the processing error also corresponds to the processing part and the type of tool, and the cause diagnosis unit 6 refers to the error cause recording unit 9, and determines the cause based on the information input by the processing part input unit 4, the displacement data selected by the error shift input unit 3, and the information input by the processing condition input unit 5. Therefore, the cause of the processing error can be diagnosed more accurately.

[0050] Furthermore, the diagnostic device is connected to the numerical control device 8, and the input of the shape diagram of the workpiece 11 can also be selected from the shape diagram of the workpiece pre-stored in the numerical control device 8, and the input of the processing conditions can also be selected from the information of the processing program pre-stored in the numerical control device 8. By connecting to the numerical control device 8 in this way, the cause of the processing error can be diagnosed more easily.

[0051] The diagnostic device of the present invention is not limited to the above-mentioned embodiments, and the overall structure of the diagnostic device and the structure for diagnosing the cause of the processing error can be appropriately changed as needed without departing from the gist of the present invention.

[0052] For example, in the above-mentioned embodiment, the error transition display unit 23 for displaying the displacement data A to F is provided in the display unit 7, and the operator selects similar displacement data. However, it is also possible to provide a display unit 23 instead of the error transition display unit 23. Figure 5 The dimension error shift display unit 27 and the measured value data display unit 28 shown in the figure are such that when the operator inputs the dimension error, the displacement data of the processing error generated this time is displayed in the measured value data display unit 28, and similar displacement data is automatically selected in the diagnostic device 1, and the cause of the processing error is displayed in the error cause display unit 26.

[0053] exist Figure 5 In the modified example shown, after inputting the processing part input unit 4, the operator measures the dimension of the workpiece 11 actually processed through the error shift input unit 3, and inputs the processing time and dimension or processing error. The input value is displayed on the dimension error shift display unit 27. In addition, the displacement data of the processing error corresponding to the input value, that is, the displacement data of the processing error generated this time, is displayed in the actual measurement value data display unit 28. Then, when the operator operates the diagnosis start button 25, the error shift input unit 3 calculates the processing error δ of the first workpiece, the absolute value of the displacement amplitude ΔY, the maximum value of the difference between the processing error in the previous processing and the processing error in the current processing, the error with the straight line approximation, and the error with the first-order lag approximation as feature values ​​based on the input value. In addition, based on the calculated feature value, similar displacement data is selected from the displacement data A to F recorded in the error cause recording unit 9 by the method described as the method of selecting displacement data in the above embodiment, that is, by selecting displacement data by classification into the first to sixth error shifts based on the feature value. Then, the cause diagnosis unit 6 determines the error cause based on the selected displacement data and the information input through the processing part input unit 4 and the processing condition input unit 5 , and displays the determined error cause in the error cause display unit 26 .

[0054] In the diagnostic device of the modification example having the above-mentioned structure, similarly to the diagnostic device 1 of the above-mentioned embodiment, it is not necessary to collect the machine tool data that is the main cause of the machining error during machining, so that the diagnostic device can be made low-cost. In addition, the actual measured value of the timing shift of the machining error can be input through the error shift input unit 3, and the error shift input unit 3 calculates the characteristic quantities related to the selection of displacement data, namely, the machining error δ of the first piece, the absolute value of the displacement amplitude ΔY, the maximum value of the difference between the machining error in the previous machining and the machining error in the current machining, the error from the straight line approximation, and the error from the first-order lag approximation, and automatically selects the displacement data based on the calculated characteristic quantities, so that even an inexperienced operator can easily and reliably diagnose the cause of the machining error.

[0055] In addition, as another modification, for example, in the above-mentioned embodiment and modification, one displacement data is selected, but it is also possible to select a plurality of displacement data and display the causes of a plurality of machining errors corresponding to each displacement data on the display unit. In addition, it is also possible to change how the timing shift of the machining error is specifically matched with the cause of the machining error in the error cause recording unit, and there is no problem even if a plurality of causes of machining errors are matched with one displacement data.

[0056] Furthermore, in the above-mentioned embodiments and modification examples, a processing part input unit and a processing condition input unit are provided, but only one of them may be provided, or neither of them may be provided. That is, it may be configured so that the causes of various processing errors are displayed in correspondence with each processing part information, or in correspondence with each processing condition information, by selecting the timing of the processing error. In addition, how to display the causes of processing errors, processing parts, processing conditions, etc. in the display unit, and its display form and layout, of course, can be changed in design.

[0057] In addition, the timing shift of the machining error accompanying repeated machining in the present invention is not limited to the shift that associates the machining error generated by each machining with the machining time, but also includes the shift that associates the machining error generated by each machining with the number of machining times, and the shift that associates the machining error generated by each machining with the number of machinings. In addition, the machining error in the present invention includes, for example, the error of tool length deviation measured by a tool sensor, and the error of the machining origin of the workpiece measured by a probe, in addition to the error generated by the workpiece in the above-mentioned embodiment.

Claims

1. A diagnostic device for diagnosing the cause of machining errors generated each time a plurality of workpieces of the same shape are machined, characterized in that: The diagnostic device is provided with: an error transition recording unit for recording a plurality of error transition information with different timings of the machining error accompanying repeated machining; an error shift input unit for selecting one or more error shift information from the plurality of error shift information; an error cause recording unit in which a plurality of causes are recorded in correspondence with the error transition information; a cause diagnosis section that refers to the error cause recording section and determines the cause based on the error transition information selected by the error transition input section; and A display unit displays the cause determined by the cause diagnosis unit.

2. The diagnostic device according to claim 1, characterized in that The diagnostic device is provided with: a processing part input unit that inputs processing part information, the processing part information being information related to determination of the processing error in the workpiece; and a processing condition input unit for inputting processing condition information, the processing condition information being information related to processing of the workpiece, and The reason also corresponds to the processing part information and the processing condition information. The cause diagnosis unit refers to the error cause recording unit and determines the cause based on the error transition information selected by the error transition input unit, the processing location information input by the processing location input unit, and the processing condition information input by the processing condition input unit.

3. The diagnostic device according to claim 2, characterized in that The diagnostic device is connected to the numerical control device. At least one of the processing location information and the processing condition information can be selected and input from data recorded in the numerical control device.

4. The diagnostic device according to any one of claims 1 to 3, characterized in that: The error shift input unit can input a measured value of the timing shift of the machining error, and The error shift input unit calculates, based on the input measured value of the timing shift, the machining error of the initially processed workpiece from the target value, i.e., the first-piece machining error Δa, the absolute value Δb of the displacement amplitude of the machining error generated between the initially processed workpiece and the last processed workpiece, the maximum value Δc of the difference between the machining error in the previous machining and the machining error in this machining, the error Δd from the straight line approximation, and at least one of the error Δe from the first-order lag approximation as feature quantities related to the selection of the error shift information, and selects the error shift information based on the calculated feature quantities.

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