CN111596612A - Numerical control machine tool thermal error compensation method and system based on workpiece dimension data - Google Patents
Numerical control machine tool thermal error compensation method and system based on workpiece dimension data Download PDFInfo
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Abstract
A numerical control machine tool thermal error compensation method and system based on workpiece size data are disclosed, wherein key temperature points are obtained by analyzing actually measured temperature data of cutting work through process capability index (Cpk) analysis based on a machining procedure; according to the critical temperature points and the size data of the workpiece processed under the machine tool load condition, a numerical control machine tool thermal error model based on workpiece size detection data is constructed through a multilayer perceptron neural network (MLP), so that the motion compensation quantity of the motion axis corresponding to the workpiece size characteristic under the actual processing condition is obtained, and thermal error compensation is realized through the external coordinate zero offset function of the numerical control machine tool. The invention takes the thermal deformation of the machine tool and the workpiece caused by the machining process into consideration, and effectively compensates the thermal error of the machine tool under the actual machining condition.
Description
Technical Field
The invention relates to a technology in the field of machining, in particular to a numerical control machine tool thermal error compensation method and system based on workpiece size data.
Background
The error is a main index for evaluating the precision of the machine tool, and the machine tool error can be generally divided into geometric error, thermal error, error caused by cutting force and the like. Wherein the thermal error accounts for 40-70% of the total error. Therefore, effective control of thermal errors is critical to improving workpiece accuracy. However, the existing numerically controlled machine tool thermal error model is usually established based on test data under the machine tool no-load condition, and thermal deformation caused by a machining process and thermal deformation of a workpiece are not considered, so that the accuracy of the established model is reduced and the compensation effect is not good in practical industrial application.
Disclosure of Invention
Aiming at the defects in the prior art, the invention provides a numerical control machine tool thermal error compensation method and system based on workpiece dimension data, a numerical control machine tool thermal error model is constructed in a multilayer perceptron neural network (MLP) mode, the motion amount of each motion axis of a machine tool is compensated based on the external coordinate zero offset function of the numerical control machine tool, and the workpiece measurement data on a production line is directly utilized, so that the machine tool thermal deformation and the workpiece thermal deformation caused by the machining process are considered, and the machine tool thermal error under the actual machining condition is effectively compensated.
The invention is realized by the following technical scheme:
the invention relates to a numerical control machine tool thermal error compensation method based on workpiece size data, which is characterized in that a key temperature point is obtained by analyzing actually measured temperature data of cutting work through process capability index (Cpk) analysis based on a machining procedure; according to the critical temperature points and the size data of the workpiece processed under the machine tool load condition, a numerical control machine tool thermal error model based on workpiece size detection data is constructed through a multilayer perceptron neural network (MLP), so that the motion compensation quantity of the motion axis corresponding to the workpiece size characteristic under the actual processing condition is obtained, and thermal error compensation is realized through the external coordinate zero offset function of the numerical control machine tool.
The cutting operation is preferably the cutting operation of various shaft and hole parts such as drilling, turning, boring and the like.
The cutting work actual measurement temperature data, through will waiting to cut the work piece level set up on the workstation of digit control machine tool, arrange temperature sensor at corresponding temperature sensitive point department, accomplish the actual cutting work of carrying out big batch work piece after the tool setting work, clear and definite the standard central value and the tolerance value of cutting the work piece size characteristic, gather the temperature data of corresponding position in real time through temperature sensor to record each temperature sensor's data this moment through temperature acquisition module.
The dimension data of the workpiece processed under the loading condition of the machine tool is obtained by cutting one workpiece every time, taking the workpiece down, horizontally arranging the workpiece on a workbench of a three-coordinate measuring machine, measuring the dimension characteristics of the workpiece according to the measurement standard of the three-coordinate measuring machine and recording the workpiece sequence.
The process capability index analysis refers to: modeling by using data of all temperature measuring points and workpiece size data in a multiple linear regression mode to obtain a full-temperature workpiece size prediction model; then measuring the single temperature point T one by oneiSubstituting the data into a full-temperature workpiece size prediction model to obtain a workpiece size prediction value D (T) under the influence of single temperaturei) And the corresponding Cpk value, denoted Cpk (△ T)i) Cpk at any temperature measurement (△ T)i) Less than the Cpk minimum requirement, this point is the critical temperature point.
The Cpk minimum requirement is preferably 1.33.
The numerical control machine tool thermal error model based on the workpiece size detection data is as follows: according to key temperature point temperature data obtained by process capability index analysis and size detection data obtained by online/offline detection of a workpiece actually machined under the condition of machine tool load, a mathematical mapping relation between the temperature data and the workpiece size data is constructed through a multilayer perceptron neural network (MLP) according to a time corresponding principle to serve as a thermal error model of a numerical control machine tool.
The multilayer perceptron neural network is realized by adopting the technology recorded in but not limited to intelligent classification algorithm based on the multilayer perceptron neural network (Lixinyu; Lixianhao; Lishiwei; Lidong snow, < communication power supply technology >2020-03-10 journal).
The numerical control machine tool thermal error model is different from a numerical control machine tool thermal error model which is constructed based on temperature data, position change errors between a cutting point of a machine tool cutter and a workpiece in the traditional method, and size detection data of the workpiece actually machined on a production line are directly utilized, so that the thermal deformation of the machine tool and the thermal deformation of the workpiece caused by a machining process are included.
The invention relates to a compensation system for realizing the method, which comprises the following steps: temperature sensor, temperature acquisition module, three coordinate measuring machine and error compensation module, wherein: the temperature sensors are respectively arranged in the air, on a surface shell of a lubricating oil tank, on a surface shell of a hydraulic oil tank, on a main shaft shell where a front bearing of a main shaft is located, at the bottom of cooling liquid, at a screw nut of a Z shaft, on a main shaft shell where a rear bearing of the main shaft is located and on a machine tool shell, and output temperature data information to the temperature acquisition module, the temperature acquisition module is connected with the error compensation module and transmits the temperature information, the three-coordinate measuring machine measures workpiece dimension data and outputs the workpiece dimension data to the error compensation module, the error compensation module establishes a thermal error model according to the temperature information and the workpiece dimension data, and then the compensation quantity of a motion shaft corresponding to the workpiece dimension characteristic is obtained through calculation and transmitted to the numerical control.
The temperature acquisition module and the error compensation module are preferably arranged in an electric control cabinet of the numerical control machine tool.
Technical effects
The invention integrally solves the problem of thermal deformation of the machine tool caused by the machining process; the invention establishes a numerical control machine tool thermal error model considering the thermal deformation condition of the workpiece by utilizing the dimension data of the workpiece actually processed on the production line, and effectively compensates the machine tool thermal error under the actual processing condition.
Drawings
FIG. 1 is a schematic diagram of the system of the present invention;
FIG. 2 is a schematic diagram showing the temperature difference between the measured temperature of each sensor and the room temperature;
FIG. 3 is a schematic representation of workpiece dimensional measurement data;
FIG. 4 is a schematic diagram illustrating a key temperature point identification process;
FIG. 5 is a diagram illustrating the fitting results of a thermal error model;
FIG. 6 is a schematic diagram of the working principle of the compensation system;
FIG. 7 is a schematic diagram of predicted data of the inner diameter of the workpiece before compensation and actual measured data of the inner diameter of the workpiece after compensation;
in the figure: the device comprises a temperature sensor 1, a temperature sensor 2, a temperature sensor 3, a temperature sensor 4, a temperature sensor 5, a temperature sensor 6, a temperature sensor 7, a temperature sensor 8, a temperature acquisition module 9, a numerical control machine tool 10, a workpiece to be cut 11, a three-coordinate measuring machine 12 and an error compensation module 13.
Detailed Description
As shown in fig. 1, the present embodiment relates to a measuring device for measuring a thermal error of a numerically controlled machine tool and a specific application scenario thereof, including: the temperature measurement device comprises a temperature sensor 1 for measuring room temperature, a temperature sensor 2 for lubricating oil temperature, a temperature sensor 3 for hydraulic oil temperature, a temperature sensor 4 for spindle front bearing temperature, a temperature sensor 5 for cooling liquid temperature, a temperature sensor 6 for Z-axis lead screw temperature, a temperature sensor 7 for spindle rear bearing temperature, a temperature sensor 8 for machine tool bed temperature, a temperature acquisition module 9 with real-time temperature acquisition and data storage functions, a numerical control machine tool 10 for performing cutting tasks, a workpiece 11 for cutting, a three-coordinate measuring machine 12 for measuring workpiece dimension characteristics, and an error compensation module 13 for interacting with the numerical control system and writing motion axis compensation output by a thermal error model into the numerical control system.
In this embodiment, for the drilling and cutting operation, preferably, the method for compensating the thermal error of the numerical control machine tool based on the workpiece size data by acquiring temperature data through eight temperature sensors includes the following specific steps:
1) a workpiece to be cut is horizontally arranged on a workbench of the numerical control machine tool, and the temperature sensors are respectively arranged in the air and numbered as T1The number of the surface shell of the lubricating oil tank is T2The number of the surface shell of the hydraulic oil tank is T3The main shaft shell at the position of the main shaft front bearing is numbered as T4And the bottom of the cooling liquid is numbered as T5And the Z-axis lead screw nut is numbered as T6The main shaft shell at the position of the main shaft rear bearing is numbered as T7And the number on the machine tool shell is T8And then, clamping and setting the workpiece, and writing a machining code of the numerical control machine.
2) The mass actual drilling and cutting work of 152 workpieces is carried out, the center value of the aperture specification of the cut workpiece is 45.600mm, the tolerance is +/-10 mu m, namely the upper limit of the aperture specification is 45.610mm, and the lower limit of the specification is 45.590 mm.
In the middle, normal shutdown is carried out for 3 times according to actual production conditions, the temperature sensors acquire temperature data in real time, the data of each temperature sensor when each workpiece is processed is recorded through the temperature acquisition module, in order to better represent the change value of the temperature, the temperature difference of the temperature of each point relative to the room temperature is recorded in the following table corresponding to each workpiece, and the corresponding relation curve of the temperature difference and the serial number of the workpiece is shown in figure 2.
3) After each workpiece is cut, the workpiece is taken down and horizontally arranged on a worktable of the three-coordinate measuring machine, the inner diameter of the hole characteristic is measured according to the measurement standard of the three-coordinate measuring machine, the data is recorded according to the workpiece serial number as shown in the following table, and the corresponding relation between the workpiece size and the workpiece serial number is shown in fig. 3.
| Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/mm | Serial number | Inner diameter/ |
| 1 | 45.607 | 20 | 45.594 | 39 | 45.604 | 58 | 45.595 | 77 | 45.591 | 96 | 45.590 | 115 | 45.592 | 134 | 45.596 |
| 2 | 45.606 | 21 | 45.595 | 40 | 45.602 | 59 | 45.594 | 78 | 45.591 | 97 | 45.590 | 116 | 45.591 | 135 | 45.595 |
| 3 | 45.604 | 22 | 45.594 | 41 | 45.604 | 60 | 45.593 | 79 | 45.590 | 98 | 45.589 | 117 | 45.591 | 136 | 45.595 |
| 4 | 45.602 | 23 | 45.593 | 42 | 45.603 | 61 | 45.595 | 80 | 45.590 | 99 | 45.599 | 118 | 45.589 | 137 | 45.595 |
| 5 | 45.600 | 24 | 45.594 | 43 | 45.603 | 62 | 45.594 | 81 | 45.589 | 100 | 45.598 | 119 | 45.590 | 138 | 45.595 |
| 6 | 45.601 | 25 | 45.595 | 44 | 45.601 | 63 | 45.593 | 82 | 45.591 | 101 | 45.597 | 120 | 45.590 | 139 | 45.594 |
| 7 | 45.601 | 26 | 45.594 | 45 | 45.600 | 64 | 45.595 | 83 | 45.590 | 102 | 45.595 | 121 | 45.589 | 140 | 45.594 |
| 8 | 45.600 | 27 | 45.593 | 46 | 45.600 | 65 | 45.594 | 84 | 45.590 | 103 | 45.597 | 122 | 45.589 | 141 | 45.593 |
| 9 | 45.599 | 28 | 45.593 | 47 | 45.599 | 66 | 45.593 | 85 | 45.591 | 104 | 45.595 | 123 | 45.590 | 142 | 45.595 |
| 10 | 45.599 | 29 | 45.592 | 48 | 45.599 | 67 | 45.593 | 86 | 45.589 | 105 | 45.595 | 124 | 45.590 | 143 | 45.594 |
| 11 | 45.598 | 30 | 45.593 | 49 | 45.598 | 68 | 45.592 | 87 | 45.590 | 106 | 45.593 | 125 | 45.588 | 144 | 45.594 |
| 12 | 45.598 | 31 | 45.593 | 50 | 45.598 | 69 | 45.593 | 88 | 45.589 | 107 | 45.594 | 126 | 45.590 | 145 | 45.593 |
| 13 | 45.597 | 32 | 45.592 | 51 | 45.599 | 70 | 45.592 | 89 | 45.588 | 108 | 45.594 | 127 | 45.600 | 146 | 45.592 |
| 14 | 45.596 | 33 | 45.594 | 52 | 45.597 | 71 | 45.592 | 90 | 45.591 | 109 | 45.593 | 128 | 45.601 | 147 | 45.591 |
| 15 | 45.596 | 34 | 45.594 | 53 | 45.596 | 72 | 45.591 | 91 | 45.589 | 110 | 45.592 | 129 | 45.599 | 148 | 45.592 |
| 16 | 45.595 | 35 | 45.593 | 54 | 45.597 | 73 | 45.592 | 92 | 45.590 | 111 | 45.594 | 130 | 45.599 | 149 | 45.591 |
| 17 | 45.596 | 36 | 45.592 | 55 | 45.595 | 74 | 45.591 | 93 | 45.589 | 112 | 45.593 | 131 | 45.599 | 150 | 45.592 |
| 18 | 45.596 | 37 | 45.595 | 56 | 45.595 | 75 | 45.591 | 94 | 45.590 | 113 | 45.592 | 132 | 45.598 | 151 | 45.591 |
| 19 | 45.594 | 38 | 45.593 | 57 | 45.595 | 76 | 45.590 | 95 | 45.590 | 114 | 45.591 | 133 | 45.599 | 152 | 45.590 |
4) After the whole large-batch cutting task is completed, the Cpk-based analysis is carried out on each continuously acquired temperature data and the inner diameter of the workpiece, and a key temperature point is identified, wherein the process is shown in FIG. 4:
4.1) modeling by using data of all temperature measuring points and workpiece inner diameter data in a multiple linear regression mode to construct and obtain a full-temperature workpiece size prediction model D (T) ═ 0.005 delta T2+0.003ΔT3+0.001ΔT4-0.006ΔT5+0.021ΔT6-0.008ΔT7-0.014ΔT8+45.587；
4.2) bringing the individual temperatures one by oneMeasuring point TiSubstituting the data into a full-temperature prediction model expression to obtain a predicted value D (T) of the size of the workpiece under the influence of single temperaturei) And the corresponding Cpk value, denoted Cpk (△ T)i). The Cpk calculation here is centered on the sample mean with no change in the upper and lower tolerances.
By T2For example, D (T)2) The calculation formula of (2): d (T)2)＝-0.005ΔT2+45.587. Based on D (T)2) Cpk value obtained by data calculation is Cpk (△ T)2)。
4.3) comparison of Cpk (△ T)i) The minimum requirement of Cpk is 1.33, the minimum required Cpk at any temperature (△ T)i) Less than 1.33, this point is the critical temperature point. Based on the above Cpk Effect analysis, T2，T6And T7Cpk (△ T) for each temperature selected as the key temperature pointi) The values are reported in the table below.
| △Ti | △T2 | △T3 | △T4 | △T5 | △T6 | △T7 | △T8 |
| Cpk(△Ti) | 1.29 | 1.74 | 6.13 | 2.35 | 0.32 | 0.26 | 2.79 |
5) Based on the identified key temperature points, under the condition that the thermal error of the translation shaft is compensated, the inner diameter of the workpiece is mainly related to the radial thermal error of the main shaft. It is therefore believed that the change in the dimension of the inner diameter of the workpiece directly reflects the change in the radial thermal error of the spindle. The main shaft radial thermal error R (T) can be represented by the difference value between the inner diameter of the workpiece and the standard central value, a main shaft radial thermal error model is constructed in a multilayer perceptron neural network (MLP) mode, corresponding thermal error results corresponding to each workpiece are calculated through the model and are recorded in the following table, and a corresponding relation result curve of the thermal errors and the workpiece serial numbers is shown in FIG. 5.
| Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/μm | Serial number | R(T)/ |
| 1 | 4.688 | 20 | -6.007 | 39 | 1.033 | 58 | -5.952 | 77 | -7.692 | 96 | -9.602 | 115 | -8.916 | 134 | -4.397 |
| 2 | 4.238 | 21 | -5.232 | 40 | -0.527 | 59 | -4.172 | 78 | -7.608 | 97 | -9.869 | 116 | -8.251 | 135 | -4.114 |
| 3 | 2.377 | 22 | -6.027 | 41 | -0.437 | 60 | -5.531 | 79 | -7.966 | 98 | -10.519 | 117 | -9.900 | 136 | -3.678 |
| 4 | 2.079 | 23 | -6.185 | 42 | -0.887 | 61 | -5.798 | 80 | -8.198 | 99 | -6.084 | 118 | -9.970 | 137 | -5.164 |
| 5 | 1.699 | 24 | -6.641 | 43 | -1.281 | 62 | -6.835 | 81 | -7.926 | 100 | -5.324 | 119 | -9.939 | 138 | -5.455 |
| 6 | 1.900 | 25 | -6.494 | 44 | -1.273 | 63 | -7.791 | 82 | -7.975 | 101 | -5.393 | 120 | -9.712 | 139 | -6.177 |
| 7 | 0.553 | 26 | -5.041 | 45 | -0.848 | 64 | -8.289 | 83 | -8.151 | 102 | -5.989 | 121 | -10.509 | 140 | -6.013 |
| 8 | -0.016 | 27 | -6.470 | 46 | -1.987 | 65 | -8.334 | 84 | -8.189 | 103 | -6.703 | 122 | -10.325 | 141 | -5.681 |
| 9 | -1.598 | 28 | -5.631 | 47 | -1.914 | 66 | -7.382 | 85 | -8.877 | 104 | -7.290 | 123 | -10.104 | 142 | -4.346 |
| 10 | -2.073 | 29 | -5.268 | 48 | -1.809 | 67 | -8.319 | 86 | -8.716 | 105 | -7.716 | 124 | -11.042 | 143 | -5.470 |
| 11 | 0044 | 30 | -5424 | 49 | -1931 | 68 | -8804 | 87 | -8064 | 106 | -8451 | 125 | -10695 | 144 | -5806 |
| 12 | -1.457 | 31 | -5.493 | 50 | -1.765 | 69 | -9.066 | 88 | -8.078 | 107 | -7.372 | 126 | -11.212 | 145 | -5.882 |
| 13 | -3641 | 32 | -5264 | 51 | -3691 | 70 | -9300 | 89 | -8504 | 108 | -8169 | 127 | 1963 | 146 | -6170 |
| 14 | -4.753 | 33 | -6.929 | 52 | -2.618 | 71 | -9.746 | 90 | -8.301 | 109 | -7.346 | 128 | 1.275 | 147 | -6.164 |
| 15 | -4.095 | 34 | -6.218 | 53 | -3.162 | 72 | -8.918 | 91 | -8.558 | 110 | -7.754 | 129 | -0.667 | 148 | -5.815 |
| 16 | -5.613 | 35 | -6.101 | 54 | -3.108 | 73 | -8.797 | 92 | -8.768 | 111 | -8.458 | 130 | -2.364 | 149 | -5.892 |
| 17 | -5.758 | 36 | -6.205 | 55 | -5.417 | 74 | -6.955 | 93 | -9.851 | 112 | -7.996 | 131 | -4.072 | 150 | -7.089 |
| 18 | -5.454 | 37 | -5.868 | 56 | -4.687 | 75 | -7.568 | 94 | -9.022 | 113 | -7.669 | 132 | -3.886 | 151 | -6.148 |
| 19 | -5.727 | 38 | -0.550 | 57 | -3.582 | 76 | -7.543 | 95 | -8.797 | 114 | -8.899 | 133 | -4.279 | 152 | -6.483 |
6) According to the working principle of the compensation system in the figure 6, the interaction between the error compensation module and the numerical control system is realized based on the FOCAS function library of the Ethernet and the FANUC numerical control system, and the motion compensation quantity value of the motion axis corresponding to the workpiece dimension characteristic calculated by the thermal error model is output to the numerical control system based on the zero offset function of the external coordinate of the numerical control machine, so that the error compensation is completed.
In this embodiment, the error compensation module is connected to the numerical control system through an ethernet interface, performs data interaction with the numerical control system in combination with the FOCAS function library of the FANUC numerical control system, embeds a software platform developed based on the labv virtual instrument therein, and integrates the MATLAB function to perform modeling of the thermal error of the numerical control machine and calculation and output of the compensation value of the machine motion axis.
7) After compensation, 135 workpieces are continuously machined on the numerical control machine tool, the inner diameter data of each workpiece before compensation is predicted, and the result is recorded in the following table.
The compensated inner diameter data of each workpiece is measured by using a three-coordinate measuring machine, and the result is recorded in the following table, and the corresponding relation curve of the predicted inner diameter data of the workpiece before compensation, the actually measured inner diameter data of the workpiece after compensation and the serial number of the workpiece is shown in fig. 7.
The 135 workpieces were compared and analyzed for inner diameter error data before and after compensation, the maximum inner diameter error before compensation was 12.8 μm, which exceeded the tolerance range, and Cpk was 0.76. After compensation, the variation range of the inner diameter of the workpiece is between 45.596mm and 45.606mm, the maximum error of the inner diameter is 6 mu m, the maximum error is within the tolerance range, and the Cpk is 1.48, thereby meeting the production requirement. Therefore, the compensation effect of the established thermal error model is obvious.
Compared with the method for establishing a thermal error model of the numerical control machine tool based on temperature data and position change errors between a cutting point of a tool of the machine tool and a workpiece in the prior art, the method directly utilizes the size detection data of the workpiece actually machined on a production line to carry out analysis modeling, and the whole method is obtained by analysis based on the actually-measured workpiece size data on the production line, so that the thermal errors of the machine tool and the workpiece caused by the machining process are included. And (3) analyzing a heat source influencing the thermal error of the machine tool, implementing the temperature distribution in advance, and identifying a key temperature point based on Cpk analysis. In a large-batch workpiece cutting task, a three-coordinate measuring machine is used for measuring the dimension characteristics of each cut workpiece and recording measurement data. The error compensation module is used for constructing a thermal error model of the numerical control machine tool through an MLP (multi-level linear programming) method based on temperature data of key temperature points and size data of a large number of workpieces processed under the condition of machine tool load, interacting with a numerical control system of the machine tool through the error compensation module, outputting compensation quantity of a motion axis corresponding to the size characteristic of the workpieces to complete compensation based on an external coordinate zero offset function, and realizing effective compensation on the thermal error of the machine tool under the actual processing condition by directly utilizing the size data of the workpieces actually processed on a production line, thereby considering the thermal deformation of the machine tool and the thermal deformation of the workpieces caused by the processing process.
The foregoing embodiments may be modified in many different ways by those skilled in the art without departing from the spirit and scope of the invention, which is defined by the appended claims and all changes that come within the meaning and range of equivalency of the claims are therefore intended to be embraced therein.
Claims (4)
1. A numerical control machine tool thermal error compensation method based on workpiece size data is characterized in that key temperature points are obtained by analyzing actually measured temperature data of cutting work through process capability index analysis based on machining procedures; according to the key temperature point and the size data of the workpiece processed under the machine tool load condition, a numerical control machine tool thermal error model based on workpiece size detection data is established through a multilayer perceptron neural network, so that the motion compensation quantity of a motion axis corresponding to the workpiece size characteristic under the actual processing condition is obtained, and thermal error compensation is realized through the external coordinate zero offset function of the numerical control machine tool;
the process capability index analysis refers to: modeling by using data of all temperature measuring points and workpiece size data in a multiple linear regression mode to obtain a full-temperature workpiece size prediction model; then measuring the single temperature point T one by oneiSubstituting the data into a full-temperature workpiece size prediction model to obtain a workpiece size prediction value D (T) under the influence of single temperaturei) And the corresponding Cpk value, denoted Cpk (△ T)i) Cpk at any temperature measurement (△ T)i) If the minimum Cpk requirement is less than the minimum Cpk requirement, the point is a key temperature point;
the numerical control machine tool thermal error model based on the workpiece size detection data is as follows: according to key temperature point temperature data obtained by process capability index analysis and size detection data obtained by online/offline detection of a workpiece actually machined under the condition of machine tool load, a mathematical mapping relation between the temperature data and the workpiece size data is established through a multilayer perceptron neural network according to a time corresponding principle and is used as a numerical control machine tool thermal error model.
2. The numerical control machine tool thermal error compensation method based on the workpiece dimension data according to claim 1, characterized in that the actually measured cutting temperature data of the cutting work is obtained by horizontally arranging the workpiece to be cut on a workbench of the numerical control machine tool, arranging temperature sensors at corresponding temperature sensitive points, performing actual cutting work on a large number of workpieces after the tool setting work is completed, determining a standard central value and a tolerance value of the dimension characteristics of the cut workpiece, acquiring the temperature data of corresponding positions in real time through the temperature sensors, and recording the data of each temperature sensor at the moment through a temperature acquisition module.
3. The method for compensating thermal error of numerical control machine tool based on workpiece dimension data according to claim 1, wherein the workpiece dimension data processed under the machine tool load condition is directly derived from the on-line/off-line detection of the actual processing process, the off-line detection is obtained by cutting each workpiece, removing the workpiece, horizontally arranging the workpiece on the worktable of the coordinate measuring machine, measuring the workpiece dimension characteristics according to the measurement standard of the coordinate measuring machine, and recording the workpiece sequence, and the on-line detection adopts a proper sensing detection method to obtain the workpiece dimension data, including but not limited to a laser displacement sensor, a contact micro displacement sensor, an eddy current sensor detection method and the like.
4. A compensation system for implementing the method of any of claims 1 to 3, comprising: temperature sensor, temperature acquisition module, three coordinate measuring machine and error compensation module, wherein: the temperature sensors are respectively arranged in the air, on a surface shell of a lubricating oil tank, on a surface shell of a hydraulic oil tank, on a main shaft shell where a front bearing of a main shaft is located, at the bottom of cooling liquid, at a screw nut of a Z shaft, on a main shaft shell where a rear bearing of the main shaft is located and on a machine tool shell, and output temperature data information to the temperature acquisition module, the temperature acquisition module is connected with the error compensation module and transmits the temperature information, the three-coordinate measuring machine measures workpiece dimension data and outputs the workpiece dimension data to the error compensation module, the error compensation module establishes a thermal error model according to the temperature information and the workpiece dimension data, and then the compensation quantity of a motion shaft corresponding to the workpiece dimension characteristic is obtained through calculation and transmitted to the numerical control.
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