A machine tool machining parameter self-adaptive optimization method based on spindle load capacity

Abstract

The application discloses a machine tool machining parameter self-adaptive optimization method based on spindle load capacity, collects a machine tool spindle current signal, calculates the current accompanying time accumulation degree of the machine tool spindle per unit time according to the machine tool spindle current signal, and evaluates and identifies the actual overload rate of the machine tool spindle according to the current accompanying time accumulation degree; the actual overload rate of the machine tool spindle is compared with the safe load rate, and the spindle speed and spindle related axis feed rate are self-adaptively adjusted through the comparison result; the application takes the current accompanying time accumulation degree of the spindle as an index, establishes a mapping relationship model existing between the current accompanying time accumulation degree and the spindle load through polynomial fitting, constructs a warning and automatic control mechanism based on the load rate of the spindle current, realizes self-adaptive adjustment of the spindle speed and the feed axis feed rate, reduces the load of the spindle, and effectively guarantees the health state of the spindle.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of numerical control machining, and relates to a machine tool machining parameter adaptive optimization method based on spindle load capacity. BACKGROUND

[0002] Numerical control machine tools are widely used in the field of mechanical machining, wherein the spindle is a core component responsible for controlling the cutting tool to cut parts. Due to various factors such as cutting parameters, cutting tools, and blank material properties during the cutting process, the load and vibration frequency of the spindle are in a process of continuous change. Especially when performing some large-stock-removal cutting or thin-walled part machining, the spindle is in a high-load state for a long time, causing the service life of the spindle to be shortened. The replacement and repair of the spindle are costly, and due to unreasonable machining parameter selection in the machining process of the numerical control machine tool, the spindle is in a high-load state for a long time, causing the spindle to be worn and the service life of the spindle to be shortened. However, there is a lack of a method for directly detecting the spindle and adaptively regulating the working parameters of the spindle in the prior art. SUMMARY

[0003] The purpose of the present application is to provide a machine tool machining parameter adaptive optimization method based on spindle load capacity, taking the cumulative degree of current accompanying time as an index, establishing a mapping relationship model between the cumulative degree of current accompanying time and the spindle load through polynomial fitting, constructing a warning and automatic regulation mechanism based on the load rate of the spindle current, and realizing adaptive adjustment of the spindle speed and the feed rate of the feed axis, thereby reducing the load of the spindle and effectively protecting the health of the spindle.

[0004] The present application is realized by the following technical scheme:

[0005] A machine tool machining parameter adaptive optimization method based on spindle load capacity, which collects the spindle current signal of the machine tool, calculates the cumulative degree of current accompanying time of the machine tool spindle per unit time according to the spindle current signal of the machine tool, and evaluates and identifies the actual overload rate of the machine tool spindle according to the cumulative degree of current accompanying time; compares the actual overload rate of the machine tool spindle with the safe load rate, and adaptively adjusts the spindle speed and the spindle-related axis feed rate according to the comparison result.

[0006] In order to better realize the present application, further, the following steps are specifically included:

[0007] Step 1: collect the spindle current signal of the machine tool at a fixed collection frequency, establish a current accompanying time accumulation function, and calculate the cumulative degree of current accompanying time through the current accompanying time accumulation function;

[0008] Step 2, establish a polynomial load fitting function of the actual overload rate of the machine tool spindle with respect to the cumulative degree of current accompanying time, calculate the actual load degree of the machine tool spindle based on the polynomial load fitting function;

[0009] Step 3, establish an overload rate function of the machine tool spindle according to the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle, and calculate the actual overload rate of the machine tool spindle based on the overload rate function;

[0010] Step 4, compare the actual overload rate of the machine tool spindle with the safety load rate, and adaptively adjust the spindle speed and spindle related axis feed rate according to the comparison result.

[0011] In order to better realize the present application, further, the polynomial load fitting function in the step 2 is:

[0012] M(I L )=AI L 3 +BI L 2 +CI L +D I

[0013] Wherein: A represents the third order coefficient of the polynomial load fitting function; B represents the second order coefficient of the polynomial load fitting function; C represents the first order coefficient of the polynomial load fitting function; D represents the constant residual term of the polynomial load fitting function; I L represents the cumulative degree of current accompanying time; M(I L ) represents the actual load degree of the machine tool spindle.

[0014] In order to better realize the present application, further, the current accompanying time accumulation function is:

[0015]

[0016] Wherein: I L represents the cumulative degree of current accompanying time; T a represents the unit collection time; I(t) represents the machine tool spindle current signal.

[0017] In order to better realize the present application, further, the overload rate function is:

[0018]

[0019] Wherein: η represents the actual overload rate of the machine tool spindle; M(I L ) represents the actual load degree of the machine tool spindle; K represents the rated load degree of the machine tool spindle.

[0020] In order to better realize the present application, further, the constructing polynomial load fitting function comprises the following steps:

[0021] Step A, extracting the current signal characteristic value of the machine tool spindle, the current signal characteristic value is the integral average value greater than the rated current value of the machine tool spindle in unit collection time;

[0022] Step B, based on the current signal characteristic value, the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle are iteratively trained to minimize the difference of the polynomial load fitting function, and the coefficients of the polynomial load fitting function are determined;

[0023] Step C, the reliability test of the polynomial load fitting function is carried out, the test signal is input, and whether the test result meets the accuracy requirement is detected.

[0024] In order to better realize the present application, further, the safety load rate comprises a safety lower limit value and a safety upper limit value, when the actual overload rate of the machine tool spindle is less than or equal to the safety lower limit value, the current spindle speed and spindle related axis feed rate are maintained; when the actual overload rate of the machine tool spindle is between the safety lower limit value and the safety upper limit value, the spindle speed and the spindle related axis feed rate are adjusted to 1-η times of the original; when the actual overload rate of the machine tool spindle is greater than or equal to the safety upper limit value, the spindle speed and the spindle related axis feed rate are adjusted to 0.

[0025] Compared with the prior art, the present application has the following advantages and beneficial effects:

[0026] (1) The present application collects the machine tool spindle current signal, calculates the current accompanying time accumulation degree of the machine tool spindle in unit time according to the machine tool spindle current signal, and evaluates and identifies the actual overload rate of the machine tool spindle through the current accompanying time accumulation degree, which can directly and accurately reflect the overload condition of the spindle relying on the numerical control machine tool control system itself without additional detection equipment;

[0027] (2) The present application compares the actual overload rate of the machine tool spindle with the safety load rate, and adjusts the spindle speed and the spindle related axis feed rate through the comparison result, reduces the load borne by the spindle, and realizes the effect of protecting the spindle. BRIEF DESCRIPTION OF DRAWINGS

[0028] Figure 1 It is a flowchart of the machine tool machining parameter self-adaptive optimization method;

[0029] Figure 2 It is a fitting diagram of the actual load degree;

[0030] Figure 3 It is a fitting diagram of the actual overload rate. DETAILED DESCRIPTION

[0031] The following detailed description is merely exemplary in nature and is not intended to limit the present application or the application and uses of the present application. Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which the application pertains.

[0032] It is to be noted that the terminology used herein is for purposes of describing the particular embodiments only and is not intended to be limiting of the inventive examples of the present application. As used in this specification, the singular forms "a", "an" and "the" include plural referents unless the content clearly dictates otherwise. Thus, for example, reference to "a component" includes a combination of two or more components, and the like.

[0033] For the convenience of description, if the terms "upper", "lower", "left", "right" appear in the present application, they only mean the same direction as the upper, lower, left and right directions of the drawings themselves, and do not limit the structure, but only for the convenience of describing the present application and simplifying the description, and therefore cannot be understood as limiting the present application, which indicates or implies that the device or element referred to must have a specific orientation, structure and operation, therefore cannot be understood as limiting the present application.

[0034] The terms "mounting", "connecting", "connecting", "fixing" and the like in the present application should be understood broadly, for example, it can be fixed connection, or detachable connection, or one body; it can be mechanical connection, or electrical connection, it can be direct connection, or indirect connection through intermediate medium, it can be internal connection of two elements, or interaction relationship between two elements, for those skilled in the art, the specific meaning of the above terms in the present application can be understood according to the specific circumstances.

[0035] Embodiment 1:

[0036] A machine tool machining parameter self-adaptive optimization method based on spindle load capacity of the embodiment, as shown in Figure 1 The current signal of the machine tool spindle is collected, the cumulative degree of the current accompanying time of the machine tool spindle per unit time is calculated according to the current signal of the machine tool spindle, and the actual overload rate of the machine tool spindle is evaluated and identified according to the cumulative degree of the current accompanying time; the actual overload rate of the machine tool spindle is compared with the safe load rate, and the spindle speed and spindle related axis feed ratio are self-adaptively adjusted through the comparison result.

[0037] Specifically, the following steps are included:

[0038] Step 1, collect the current signal of the machine tool spindle at a fixed collection frequency, establish the cumulative function of the current accompanying time, and calculate the cumulative degree of the current accompanying time through the cumulative function of the current accompanying time;

[0039] Step 2, establish a polynomial load fitting function of the actual overload rate of the machine tool spindle with respect to the cumulative degree of current accompanying time, and calculate the actual load degree of the machine tool spindle based on the polynomial load fitting function;

[0040] Step 3, establish an overload rate function of the machine tool spindle according to the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle, and calculate the actual overload rate of the machine tool spindle based on the overload rate function;

[0041] Step 4, compare the actual overload rate of the machine tool spindle with the safety load rate, and adaptively adjust the spindle speed and spindle related axis feed rate according to the comparison result.

[0042] The polynomial load fitting function in step 2 is:

[0043] M(I L )=AI L 3 +BI L 2 +CI L +D

[0044] Wherein: A represents the third order coefficient of the polynomial load fitting function; B represents the second order coefficient of the polynomial load fitting function; C represents the first order coefficient of the polynomial load fitting function; D represents the constant residual term of the polynomial load fitting function; I L represents the cumulative degree of current accompanying time; M(I L ) represents the actual load degree of the machine tool spindle.

[0045] The cumulative function of current accompanying time is:

[0046]

[0047] Wherein: I L represents the cumulative degree of current accompanying time; t a represents the unit collection time; I(t) represents the machine tool spindle current signal.

[0048] The overload rate function is:

[0049]

[0050] Wherein: η represents the actual overload rate of the machine tool spindle; M(I L ) represents the actual load degree of the machine tool spindle; K represents the rated load degree of the machine tool spindle.

[0051] The construction of the polynomial load fitting function includes the following steps:

[0052] Step A, extracting a current signal characteristic value of the machine tool spindle, wherein the current signal characteristic value is an integrated average value greater than a rated current value of the machine tool spindle within a unit acquisition time;

[0053] Step B: Based on the characteristic value of the current signal, the polynomial load fitting function is iteratively trained with the goal of minimizing the difference between the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle, and the coefficients of the polynomial load fitting function are determined;

[0054] Step C: Perform reliability test on the polynomial load fitting function, input a test signal, and detect whether the test result meets the accuracy requirement.

[0055] The safe load rate includes a safe lower limit value and a safe upper limit value. When the actual overload rate of the machine tool spindle is less than or equal to the safe lower limit value, the current spindle speed and the feed rate of the spindle-related axes are maintained; when the actual overload rate of the machine tool spindle is between the safe lower limit value and the safe upper limit value, the spindle speed and the feed rate of the spindle-related axes are adjusted to 1-η times the original; when the actual overload rate of the machine tool spindle is greater than or equal to the safe upper limit value, the spindle speed and the feed rate of the spindle-related axes are adjusted to 0.

[0056] Example 2:

[0057] The present embodiment provides an adaptive optimization method for machine tool processing parameters based on spindle load capacity. This method is improved on the basis of the first embodiment. Taking the 840D-SL system as an example, the adaptive optimization method for machine tool processing parameters is implemented on the CNC machine tool of the 840D-SL system. The real-time current signal I(t) of the machine tool spindle is collected through the system parameter instruction $AA_CURR[spindle number] at a frequency of 500Hz. The data with a current greater than the rated current of 5A is filtered out, and the cumulative degree of current with time within the acquisition unit time of 6s is calculated. L , see Table 1 below:

[0058] Table 1. Current accumulation value table with time

[0059]

[0060] like Figure 2 As shown, the data of the cumulative degree of the above current with time is substituted into the polynomial load fitting function to obtain the polynomial load fitting function:

[0061] M(I L )=丨0.6I L 3 +0.01I L 2 +48.9I L +1.4丨

[0062] Further, the actual load degree of the machine tool spindle is obtained, as shown in Table 2 below:

[0063] Table 2, numerical table of actual load degree of machine tool spindle

[0064]

[0065] As Figure 3 shown, the calculated actual load degree of the machine tool spindle is substituted into the overload rate function, and the rated load degree K of the machine tool is set to 1000, and the overload rate of the machine tool spindle in the time period is obtained as shown in Table 3 below:

[0066] Table 3, comparison table of actual overload rate of machine tool spindle

[0067]

[0068] In the synchronous action function of the numerical control system, the operation program and the control program are written, first, the PROG_EVENT file under the NC standard cycle is called, Bit3 and Bit5 of MD20108 under the channel parameter are set to 1, so that the machine tool calls the file after power-on and during execution of the machining program, and ensures that the program takes effect in real time. By calling the CYCPE_MA file under the CYCPE_MA file in the machine tool, the program control instructions are written in the CYCPE_MA file. The polynomial load fitting function uses the FCTDEF polynomial instruction, and the NC program control is as follows:

[0069] FCTDEF(1,0,135,D,C,B,A)

[0070] Where FCTDEF is a polynomial instruction of the numerical control system, 1 in the parentheses represents the serial number of the polynomial, 0 is the minimum value of the spindle load degree, and 135 is the maximum value of the spindle load degree.

[0071] A represents the third order coefficient of the polynomial load fitting function; B represents the second order coefficient of the polynomial load fitting function; C represents the first order coefficient of the polynomial load fitting function; D represents the constant term of the polynomial load fitting function.

[0072] IDS=1DOSYNFCT(1,M(I L ),I L )

[0073] Where IDS=1 is the program segment number, IDS=1, which means this is the first segment of the program, DO indicates the execution instruction SYNFCT instruction, 1 is the polynomial serial number of the above-mentioned polynomial, and the cumulative degree of current time is used as the polynomial input value, and the polynomial load fitting function result is used as the calculation result, that is, the actual load degree of the machine tool spindle is used as the result. The overload rate is calculated by the actual load degree and the rated load degree, and the NC programming example is as follows:

[0074] IDS=2 WHEHEVER M(I L ) > K $AC_OVR = (M(I L ) - K) / K

[0075] IDS=2 WHEHEVER M(I L ) > K $AC_OVR = (M(I L ) - K) / K

[0076] IDS=3 WHEHEVER 0.2 < ABS(η) < 0.8 DO $AC_OVR = (1 - η)

[0077] IDS=3 WHEHEVER 0.2 < ABS(η) < 0.8 DO $AC_OVR = (1 - η)

[0078] IDS=4 WHEHEVER 0.8 ≤ ABS(η) DO $AC_OVR = 0

[0079] IDS=4 WHEHEVER 0.8 ≤ ABS(η) DO $AC_OVR = 0

[0080] IDS=4 WHEHEVER 0.8 ≤ ABS(η) DO $AC_OVR = 0

[0081] The above is only a preferred embodiment of the present application, and does not limit the present application in any form. Any simple modification or equivalent change of the above embodiment according to the technical essence of the present application falls within the protection scope of the present application.

Claims

1. A method for adaptive optimization of machine tool processing parameters based on spindle load capacity, characterized in that: The machine tool spindle current signal is collected, and the accumulation of the current and time of the machine tool spindle per unit time is calculated based on the machine tool spindle current signal. The actual overload rate of the machine tool spindle is evaluated and identified based on the accumulation of the current and time. The actual overload rate of the machine tool spindle is compared with the safe load rate, and the spindle speed and the feed rate of the spindle-related axes are adaptively adjusted based on the comparison results. The specific steps include: Step 1: Collect the spindle current signal of the machine tool at a fixed acquisition frequency, establish a cumulative function of the current accompanying time, and calculate the cumulative degree of the current accompanying time through the cumulative function of the current accompanying time; Step 2: Using the cumulative degree of current over time as an independent variable, a polynomial load fitting function is established to represent the actual overload rate of the machine tool spindle with respect to the cumulative degree of current over time, and the actual load degree of the machine tool spindle is calculated based on the polynomial load fitting function; Step 3: establishing an overload rate function of the machine tool spindle according to the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle, and calculating the actual overload rate of the machine tool spindle based on the overload rate function; Step 4: Compare the actual overload rate of the machine tool spindle with the safe load rate, and adaptively adjust the spindle speed and the feed rate of the spindle-related axes based on the comparison results; The polynomial load fitting function in step 2 is: M(I L ) = |AI L 3 + BI L 2 + CI L + D|; Where: A represents the third-order coefficient of the polynomial load fitting function; B represents the second-order coefficient of the polynomial load fitting function; C represents the first-order coefficient of the polynomial load fitting function; D represents the constant remainder of the polynomial load fitting function; I L Indicates the accumulation of current over time; M(I L ) indicates the actual load degree of the machine tool spindle; The cumulative function of the current over time is: Where: I L Indicates the accumulation of current over time; T a Indicates the unit acquisition time; I(t) indicates the current signal of the machine tool spindle; The overload rate function is: Where: η represents the actual overload rate of the machine tool spindle; M(I L ) represents the actual load of the machine tool spindle; K represents the rated load of the machine tool spindle.

2. The method for adaptively optimizing machine tool processing parameters based on spindle load capacity according to claim 1, characterized in that: Constructing a polynomial load fitting function involves the following steps: Step A, extracting a current signal characteristic value of the machine tool spindle, wherein the current signal characteristic value is an integrated average value greater than a rated current value of the machine tool spindle within a unit acquisition time; Step B: Based on the characteristic value of the current signal, the polynomial load fitting function is iteratively trained with the goal of minimizing the difference between the actual load degree of the machine tool spindle and the rated load degree of the machine tool spindle, and the coefficients of the polynomial load fitting function are determined; Step C: Perform reliability test on the polynomial load fitting function, input a test signal, and detect whether the test result meets the accuracy requirement.

3. The method for adaptively optimizing machine tool processing parameters based on spindle load capacity according to claim 2, characterized in that: The safe load rate includes a safe lower limit value and a safe upper limit value. When the actual overload rate of the machine tool spindle is less than or equal to the safe lower limit value, the current spindle speed and the feed rate of the spindle-related axes are maintained; when the actual overload rate of the machine tool spindle is between the safe lower limit value and the safe upper limit value, the spindle speed and the feed rate of the spindle-related axes are adjusted to 1-η times the original; when the actual overload rate of the machine tool spindle is greater than or equal to the safe upper limit value, the spindle speed and the feed rate of the spindle-related axes are adjusted to 0.

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