Compensation method and system for thermal error of lead screw and machine tool

Abstract

The invention provides a compensation method and system for the thermal error of a lead screw and a machine tool, the lead screw is applied to the machine tool, and the compensation method comprises the steps that the temperature of the lead screw is obtained; when the machine tool is in the machining state and the temperature of the lead screw is gradually increased to the preset temperature from the initial temperature, first thermal error values of the lead screw at the multiple preset temperatures are obtained; when the machine tool is in the machining state and the temperature of the lead screw is gradually reduced to the initial temperature from the preset temperature, second thermal error values of the lead screw at the multiple preset temperatures are obtained; determining thermal error values of the lead screw at different temperatures according to the first thermal error value and the second thermal error value; and compensating the machine tool according to the thermal error values of the screw rod at different temperatures. According to the compensation method for the thermal error of the lead screw, the machining precision of a machine tool can be improved.

Description

Technical Field

[0001] The present invention relates to the technical field of processing equipment, and in particular to a method and system for compensating thermal errors of a screw rod and a machine tool. Background Art

[0002] During the movement of the screw of a CNC machine tool, it will be affected by the frictional heating of the moving pair and the initial temperature change of the machine tool. Thermal deformation will occur in the direction of linear motion, resulting in positioning errors, affecting the consistency of part processing. This error is considered to be the thermal error of the machine tool feed axis.

[0003] The size of the thermal error during the movement of the screw is an important parameter for measuring the performance of the screw. The existing screw performance test method mainly relies on laser interferometer for air cutting test. This method saves time and effort and requires almost no cost, but it also has obvious defects. Due to the influence of the mirror group, coolant cannot be added, and the important heat source of part machining cutting heat is ignored. That is, the test conditions are quite different from the actual machining conditions, resulting in inadequate compensation and affecting the machining accuracy of the machine tool.

[0004] Therefore, how to improve the accuracy of machine tool processing is an urgent problem to be solved. Summary of the invention

[0005] The present invention provides a method and system for compensating thermal errors of a screw rod and a machine tool, which can improve the machining accuracy of the machine tool.

[0006] A first aspect of the present invention provides a method for compensating thermal errors of a screw rod, wherein the screw rod is applied to a machine tool, comprising:

[0007] Obtaining the temperature of the screw rod;

[0008] When the machine tool is in a processing state and the temperature of the screw rod is gradually increased from an initial temperature to a preset temperature, obtaining a first thermal error value of the screw rod at a plurality of preset temperatures;

[0009] When the machine tool is in a processing state and the temperature of the screw rod is gradually reduced from a preset temperature to an initial temperature, obtaining a second thermal error value of the screw rod at a plurality of preset temperatures;

[0010] Determining the thermal error value of the screw rod at different temperatures according to the first thermal error value and the second thermal error value;

[0011] The machine tool is compensated according to the thermal error values ​​of the screw rod at different temperatures.

[0012] In some feasible implementations, the machine tool includes a nut connected to a screw rod, and the screw rod drives the nut to move by rotating; and obtaining the first thermal error value of the screw rod at multiple preset temperatures specifically includes:

[0013] When the machine tool is in a processing state and the temperature of the screw rod is at an initial temperature, obtaining a plurality of initial positioning error values ​​of the screw rod when the nut is at a plurality of preset processing positions;

[0014] Controlling the screw rod to heat up for the first time, when the machine tool is in a processing state and the temperature of the screw rod rises to a first intermediate temperature, obtaining a plurality of first intermediate positioning error values ​​of the screw rod when the nut moves to a plurality of preset processing positions; wherein each of the first intermediate positioning error values ​​is obtained by calculating a theoretical position point and an actual position point of the nut;

[0015] Obtaining a plurality of first thermal error values ​​of the screw rod after the first heating according to a plurality of first intermediate positioning error values ​​and a plurality of initial positioning error values ​​of the screw rod;

[0016] The screw rod is repeatedly controlled to heat up again, and a plurality of first thermal error values ​​after heating up again are recorded until the temperature of the screw rod rises to a preset temperature, thereby obtaining the first thermal error values ​​of the screw rod at a plurality of preset temperatures.

[0017] In some feasible implementations, obtaining the second thermal error value of the screw rod at a plurality of preset temperatures specifically includes:

[0018] When the temperature of the screw rod is at a preset temperature, the screw rod is controlled to be cooled for the first time, and when the machine tool is in a processing state and the temperature of the screw rod is at a second intermediate temperature, a plurality of second intermediate positioning error values ​​of the screw rod when the nut moves to a plurality of preset processing positions are obtained; wherein each of the second intermediate positioning error values ​​is obtained by calculating a theoretical position point and an actual position point of the nut;

[0019] Obtaining a plurality of second thermal error values ​​of the screw rod after the first cooling according to the plurality of second intermediate positioning error values ​​and the plurality of initial positioning error values ​​of the screw rod;

[0020] The screw rod is repeatedly controlled to cool down again, and the second thermal error value after cooling down again is recorded until the temperature of the screw rod is reduced to the initial temperature, thereby obtaining the second thermal error value of the screw rod at multiple preset temperatures.

[0021] In some feasible implementations, obtaining the first thermal error value of the screw rod at a plurality of preset temperatures further includes:

[0022] When the machine tool is in a processing state and the temperature of the screw rod is respectively at an initial temperature, a plurality of intermediate temperatures and a preset temperature, obtaining a front position point and a rear position point of each two adjacent processing positions of the nut;

[0023] Obtaining a first positioning error value of the screw rod corresponding to a front position point and a first positioning error value corresponding to a rear position point;

[0024] Determine a first functional relationship between a first positioning error value between a front position point and a rear position point and a processing position according to the first positioning error values ​​of the front position point and the rear position point;

[0025] A first positioning error value of an unmeasured position point between the front position point and the rear position point is determined according to the first functional relationship.

[0026] In some feasible implementations, obtaining the second thermal error value of the screw rod at a plurality of preset temperatures specifically includes:

[0027] When the machine tool is in a processing state and the temperature of the screw rod is at an intermediate temperature from a preset temperature to an initial temperature, obtaining a front position point and a rear position point of each two adjacent processing positions of the screw nut;

[0028] Obtaining a second positioning error value of the screw rod corresponding to the front position point and a second positioning error value corresponding to the rear position point;

[0029] Determine a second functional relationship between the second positioning error value of the front position point and the rear position point and the processing position according to the second positioning error value of the front position point and the rear position point;

[0030] A second positioning error value of an unmeasured position point between the front position point and the rear position point is determined according to the second functional relationship.

[0031] In some feasible implementations, the obtaining of multiple initial positioning error values ​​of the screw rod when the screw nut is at multiple preset processing positions specifically includes:

[0032] Obtaining a moving stroke of the nut, wherein the moving stroke includes an initial position and an end position;

[0033] When the temperature of the screw rod is at the initial temperature, the nut is controlled to move a certain distance from the initial position and then repeatedly move until the nut moves to the end position, and each time the nut moves a certain distance, the machine tool processes the workpiece once;

[0034] Get the theoretical position point after the nut moves a certain distance;

[0035] According to the size of the corresponding workpiece processed by the machine tool after the nut moves a certain distance, the actual position point of the nut is determined;

[0036] According to the theoretical position point and the actual position point after the nut moves a certain distance each time, the initial positioning error value after the nut moves a certain distance each time is determined to obtain a plurality of initial positioning error values ​​of the screw rod.

[0037] A second aspect of the present invention provides a thermal error compensation system for a screw, wherein the screw is applied to a machine tool, and the compensation system comprises:

[0038] An acquisition module, used for acquiring the temperature of the screw rod;

[0039] A first thermal error value acquisition module, connected to the acquisition module, for acquiring first thermal error values ​​of the screw rod at a plurality of preset temperatures when the machine tool is in a processing state and the temperature of the screw rod is gradually increased from an initial temperature to a preset temperature;

[0040] A second thermal error value acquisition module is connected to the acquisition module, and when the machine tool is in a processing state and the temperature of the screw rod is gradually reduced from the preset temperature to the initial temperature, acquires the second thermal error value of the screw rod at a plurality of preset temperatures;

[0041] A calculation module, connected to the first thermal error value acquisition module and the second thermal error value acquisition module, for determining the thermal error value of the screw rod at different temperatures according to the first thermal error value and the second thermal error value;

[0042] The compensation module is connected to the calculation module and is used to compensate the machine tool according to the thermal error values ​​of the screw rod at different temperatures.

[0043] The third aspect of the present invention provides a machine tool, including a screw rod and a nut, wherein the screw rod is connected to the nut, and also includes a compensation system for the thermal error of the above-mentioned screw rod; the acquisition module includes a temperature measuring component, which cooperates with the screw rod to sense the temperature of the screw rod.

[0044] In some feasible implementations, the machine tool further includes a controller, and the controller is connected to the compensation system;

[0045] The controller is used to obtain the theoretical position point of the nut;

[0046] The acquisition module also includes a measuring piece, which cooperates with the workpiece and is used to determine the actual position point of the nut according to the size of the workpiece processed by the machine tool;

[0047] The input end of the first thermal error value acquisition module and the input end of the second thermal error value acquisition module are both electrically connected to the acquisition module, the output end of the first thermal error value acquisition module and the output end of the second thermal error value acquisition module are both electrically connected to the calculation module, and the calculation module is also electrically connected to the compensation module.

[0048] In some feasible implementations, the machine tool further includes a spindle and a test workpiece, the test workpiece includes a mounting body and a plurality of cylinders disposed on the mounting body and disposed concentrically in sequence, and the machine tool being in a processing state includes the machine tool being in a state of processing or preparing to process the plurality of cylinders on the test workpiece; and / or,

[0049] The machine tool also includes a base, a column, a driving member and a turning tool. The column and the main shaft are installed on the base at intervals. The driving member is installed on the column. The driving member is connected to the screw rod for transmission. The controller is electrically connected to the driving member. The main shaft drives the test workpiece to rotate. The driving member drives the turning tool to move through the screw rod and the nut so as to process the workpiece through the turning tool.

[0050] The above-mentioned method for compensating the thermal error of the screw rod comprises the following steps: when the machine tool is in a processing state and the temperature of the screw rod gradually increases from an initial temperature to a preset temperature, obtaining a first thermal error value of the screw rod at multiple preset temperatures; when the machine tool is in a processing state and the temperature of the screw rod gradually decreases from a preset temperature to an initial temperature, obtaining a second thermal error value of the screw rod at multiple preset temperatures; determining the thermal error values ​​of the screw rod at different temperatures according to the first thermal error value and the second thermal error value; and compensating the machine tool according to the thermal error values ​​of the screw rod at different temperatures.

[0051] The first thermal error value is the thermal error value between any temperature in the process of heating up the screw rod and any position point of the nut in the entire stroke and the first thermal error value. The screw rod is at different temperatures and the nut moves throughout the entire stroke. There will be a corresponding first thermal error value. The second thermal error value is the thermal error value between any temperature in the process of cooling down the screw rod and any position point of the nut in the entire stroke and the second thermal error value. By compensating the machine tool with the first thermal error value and the second thermal error value, the error caused by the thermal expansion of the screw rod and the discrepancy between the actual position and the theoretical position can be eliminated, so that the measured compensation value can be as close as possible to the actual value of the machine tool during actual processing, thereby improving the processing accuracy of the machine tool. BRIEF DESCRIPTION OF THE DRAWINGS

[0052] In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings required for use in the embodiments or the prior art descriptions are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention, and for ordinary technicians in this field, other drawings can be obtained based on the structures shown in these drawings without creative work.

[0053] Figure 1 A schematic diagram of a machine tool provided in accordance with an embodiment of the present invention.

[0054] Figure 2A schematic diagram of a test workpiece of a machine tool provided in accordance with an embodiment of the present invention.

[0055] Figure 3 A flowchart of a method for determining a thermal error of a screw rod according to an embodiment of the present invention.

[0056] Figure 4 A structural block diagram of a method for compensating a thermal error of a screw rod provided in an embodiment of the present invention when the screw rod is in a heated state.

[0057] Figure 5 A structural block diagram of a screw rod in a temperature reduction state in a method for compensating a thermal error of a screw rod provided in an embodiment of the present invention.

[0058] Figure 6 A schematic diagram of moving position points and positioning error values ​​at multiple temperatures during cooling and heating in a method for compensating thermal errors of a screw provided in an embodiment of the present invention.

[0059] Figure 7 A schematic diagram of moving position points and positioning error values ​​at multiple temperatures during cooling in a method for compensating thermal errors of a screw provided by another embodiment of the present invention.

[0060] Component Symbols

[0061] 100, screw rod; 200, nut; 400, controller; 310, acquisition module; 320, first thermal error value acquisition module; 330, second thermal error value acquisition module; 340, calculation module; 350, compensation module; 500, spindle; 600, test workpiece; 610, mounting body; 620, cylinder; 700, base; 800, column; 900, driving member; 1000, turning tool.

[0062] The realization of the purpose, functional features and advantages of the present invention will be further explained in conjunction with embodiments and with reference to the accompanying drawings. DETAILED DESCRIPTION

[0063] In the description of the present invention, it should be understood that the terms "length", "width", "up", "down", "front", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inside", "outside", etc., indicating the orientation or position relationship are based on the orientation or position relationship shown in the drawings, and are only for the convenience of describing the present invention and simplifying the description, rather than indicating or implying that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0064] In addition, the terms "first" and "second" are used for descriptive purposes only and should not be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features. Therefore, the features defined as "first" and "second" may explicitly or implicitly include one or more of the features. In the description of the present invention, the meaning of "plurality" is two or more, unless otherwise clearly and specifically defined.

[0065] In the present invention, unless otherwise clearly specified and limited, the terms "installed", "connected", "connected", "fixed" and the like should be understood in a broad sense, for example, it can be a fixed connection, a detachable connection, or an integral connection; it can be a mechanical connection; it can be directly connected or indirectly connected through an intermediate medium. For ordinary technicians in this field, the specific meanings of the above terms in the present invention can be understood according to specific circumstances.

[0066] In order to make the content of the present invention more clearly and more accurately understood, it will now be described in detail with reference to the accompanying drawings. The accompanying drawings in the specification illustrate examples of embodiments of the present invention, wherein the same reference numerals represent the same elements. It is understood that the scales shown in the accompanying drawings in the specification are not the scales of the actual implementation of the present invention, and are only for the purpose of illustrative description, and are not drawn according to the original size.

[0067] It is understandable that the screw rod will expand when the temperature is increased, so the feed of the screw rod for one rotation after the temperature is increased will be less than the feed of the screw rod for one rotation at the initial temperature. This will cause the error of machine tool processing to increase after the temperature of the screw rod is increased, thereby reducing the accuracy of machine tool processing.

[0068] Please see Figure 1 , 2 And 3. A first aspect of the present invention provides a method for compensating thermal errors of a screw rod, wherein the screw rod is applied to a machine tool, and the compensation method comprises the following steps.

[0069] Step S10: Obtain the temperature of the screw rod; it can be understood that there are three temperature states of the screw rod. The first is the initial temperature, which is the ambient temperature. The ambient temperature will change according to the changes in the environment in which the machine tool is located. The second is a certain temperature during the heating process. When the screw rod is working, friction will occur between it and the nut, and friction will generate heat. The heating process is the process in which the temperature of the screw rod rises from the initial temperature to the preset temperature. The third is a certain temperature during the cooling process. After the temperature of the screw rod rises, if it stops working, the temperature will drop. The cooling process is the process in which the temperature of the screw rod drops from the preset temperature to the initial temperature.

[0070] Step S30: When the machine tool is in a processing state and the temperature of the screw rod is gradually increased from the initial temperature to the preset temperature, a first thermal error value of the screw rod at multiple preset temperatures is obtained; by measuring the first thermal error value of the screw rod at multiple preset temperatures when the machine tool is in a processing state, it is possible to predict the error value of the screw rod at the temperature when the machine tool is installed with the screw rod, so that the first thermal error value is as close to the actual value as possible (see for details). Figure 3 , 5 and 6). Step S30 specifically includes:

[0071] Step S31: When the machine tool is in a processing state and the temperature of the screw rod is at an initial temperature, obtain multiple initial positioning error values ​​of the screw rod when the nut is at multiple preset processing positions; by measuring the initial positioning error value, the positioning error value of the machine tool processing at the initial temperature can be determined.

[0072] Specifically, step S31 specifically includes step S311 to step S319.

[0073] Step S311: Obtain the moving stroke of the nut, wherein the moving stroke includes an initial position and an end position; it can be understood that the moving stroke of the nut is the distance the nut moves from one side of the screw rod to the other side, and the screw rod can be located on the X-axis of the machine tool, can be located on the Y-axis of the machine tool, and can be located on the Z-axis of the machine tool, so the moving stroke can be at least one of the X-axis stroke, Y-axis stroke, and Z-axis stroke.

[0074] Step S313: When the temperature of the screw rod is at the initial temperature, the nut is controlled to move a certain distance from the initial position and then repeatedly move until the nut moves to the end position, and each time the nut moves a certain distance, the machine tool processes the workpiece once; the length of each movement of the nut can be adjusted according to the actual situation, and if you want to be closer to the actual situation, the length of each movement of the nut can be reduced, for example, to 1mm. However, the length can be adjusted according to the actual situation, and is not limited to this.

[0075] Step S315: obtaining the theoretical position point after the nut moves a certain distance; the point can be obtained through the controller of the machine tool, and the controller displays the distance the nut has moved as the theoretical position point after the nut has moved a certain distance.

[0076] Step S317: Determine the actual position of the nut based on the size of the corresponding workpiece processed by the machine tool after the nut moves a certain distance; it can be understood that the nut stops moving after moving a certain distance, the machine tool can be a lathe, the spindle drives the workpiece to rotate around the axis, and the machine tool processes the workpiece, and by measuring the size of the processed workpiece, the actual position of the nut after movement can be obtained based on the relationship between the axis and the positioning origin of the lathe.

[0077] Step S319: Determine the initial positioning error value after the nut moves a certain distance according to the theoretical position point and the actual position point after the nut moves a certain distance, so as to obtain multiple initial positioning error values ​​of the screw rod. For example, the initial positioning error value of the current position can be determined according to the difference between the theoretical position point and the actual position point of the current position after the nut moves a certain distance.

[0078] Step S33: Control the screw rod to heat up for the first time, when the machine tool is in a processing state and the temperature of the screw rod rises to a first intermediate temperature, it can be understood that the first intermediate temperature is any temperature in the process of the temperature of the screw rod rising from the initial temperature to the preset temperature, and obtain multiple first intermediate positioning error values ​​of the screw rod when the nut moves to multiple preset processing positions; wherein each of the first intermediate positioning error values ​​is calculated by the theoretical position point and the actual position point of the nut; it can be understood that the expansion parameters of the screw rod during the heating process are different from the expansion parameters of the screw rod during the cooling process, so the first intermediate positioning error value when the screw rod is heated for the first time is collected, thereby improving the accuracy of the first intermediate positioning error value.

[0079] Step S35: obtaining a plurality of first thermal error values ​​of the screw rod after the first heating according to the plurality of first intermediate positioning error values ​​and the plurality of initial positioning error values ​​of the screw rod; it can be understood that after subtracting the plurality of first intermediate positioning error values ​​and the plurality of initial positioning error values ​​of the screw rod, the plurality of first thermal error values ​​of the screw rod after the first heating can be obtained (see Figure 3 , 4 , 5 and Figure 6 ).

[0080] Step S37: Repeat the control of the screw rod to heat up again, and record multiple first thermal error values ​​after heating up again, until the temperature of the screw rod rises to the preset temperature, thereby obtaining the first thermal error value of the screw rod at multiple preset temperatures. The heating process is repeated many times, for example, starting from the initial temperature, each time the temperature rises by 2-4 degrees. After the screw rod is heated up, the nut moves from one end of the screw rod to the other end, and the machine tool processes the workpiece. The screw rod will have a slight temperature rise, for example, less than 1 degree, which will be lower than the temperature of each heating of the screw rod.

[0081] Since the measurement is for the position point after the nut moves a certain distance, there is no way to measure the first thermal error value between the position before and after the nut moves a certain distance. In order to obtain the first thermal error value between the position before and after the nut moves a certain distance, step S30 also includes:

[0082] Step S32: when the machine tool is in a processing state and the temperature of the screw rod is respectively at an initial temperature, a plurality of intermediate temperatures and a preset temperature, obtaining a front position point and a rear position point of every two adjacent processing positions of the nut;

[0083] Step S34: obtaining a first positioning error value of the screw rod corresponding to the front position point and a first positioning error value corresponding to the rear position point;

[0084] Step S36: determining a first functional relationship between the first positioning error value between the front position point and the rear position point and the processing position according to the first positioning error values ​​of the front position point and the rear position point;

[0085] Step S38: determining a first positioning error value of an unmeasured position point between the front position point and the rear position point according to the first functional relationship.

[0086] Step S50: When the machine tool is in a processing state and the temperature of the screw rod is gradually reduced from the preset temperature to the initial temperature, the second thermal error value of the screw rod at multiple preset temperatures is obtained; it can be understood that the expansion parameters of the screw rod are also different during the cooling process, so it is necessary to measure the second thermal error value during the cooling process. The following specifically describes how to measure the second thermal error value during the cooling process (see Figure 3 , 4 , 5 and Figure 7 ).

[0087] Step S50 specifically includes steps S51 to S55.

[0088] Step S51: When the temperature of the screw rod is at a preset temperature, the screw rod is controlled to cool down for the first time. When the machine tool is in a processing state and the temperature of the screw rod is at a second intermediate temperature, multiple second intermediate positioning error values ​​of the screw rod when the nut moves to multiple preset processing positions are obtained; wherein each of the second intermediate positioning error values ​​is calculated by the theoretical position point and the actual position point of the nut. It can be understood that when measuring the temperature during the cooling process, it is necessary to start from the preset temperature, that is, from the screw rod at the highest temperature, and cool down in sequence. The cooling amplitude can be based on a certain temperature value, such as 2-4 degrees. The cooling amplitude can also be based on a certain time, such as 30-60 seconds.

[0089] Step S53: obtaining multiple second thermal error values ​​of the screw rod after the first cooling according to the multiple second intermediate positioning error values ​​and the multiple initial positioning error values ​​of the screw rod; it can be understood that the multiple second thermal error values ​​of the screw rod after the first cooling are obtained by subtracting the multiple second intermediate positioning error values ​​of the screw rod from the multiple initial positioning error values. Of course, the multiple second thermal error values ​​of the screw rod after the first cooling are obtained by subtracting the multiple initial positioning error values ​​from the multiple second intermediate positioning error values ​​of the screw rod.

[0090] Step S55: Repeat the control of the screw rod to cool down again, and record the second thermal error value after cooling down again, until the temperature of the screw rod drops to the initial temperature, thereby obtaining the second thermal error value of the screw rod at multiple preset temperatures. During the cooling process, multiple second thermal error values ​​are measured during multiple coolings, thereby providing data basis for subsequent compensation.

[0091] Since the measurement is made for the position point after the nut moves a certain distance, the second thermal error value between the position before and after the nut moves a certain distance cannot be measured. In order to obtain the second thermal error value between the position before and after the nut moves a certain distance, thereby improving the comprehensiveness of the second thermal error value data, step S50 also includes steps S52 to S58.

[0092] Step S52: When the machine tool is in the processing state, and the temperature of the screw rod is at an intermediate temperature from the preset temperature to the initial temperature, the front position point and the rear position point of each adjacent processing position of the nut are obtained; it can be understood that the nut only needs to move once within the moving stroke, and the distance the nut moves each time can be equal or unequal. For example, the stroke of the nut is 0-650mm. Since the machine tool often processes the position of 200-400mm, when the nut is between 200-400mm, the distance moved each time can be smaller, which can improve the accuracy of the machine tool's often processed position data. For the nut between 0-200mm and 400-650mm, the distance moved each time can be larger than the nut between 200-400mm, which can reduce the number of data measurements and improve efficiency.

[0093] Step S54: Obtain the second positioning error value corresponding to the front position point of the screw rod and the second positioning error value corresponding to the rear position point; it can be understood that the front position point after each movement of the nut corresponds to a second positioning error value, and the rear position point after each movement of the nut also has a corresponding second positioning error value.

[0094] Step S56: Determine the second functional relationship between the second positioning error values ​​of the front position point and the rear position point and the processing position based on the second positioning error values ​​of the front position point and the rear position point; it can be understood that at this time the second functional relationship can be a direct proportional function, the second positioning error value of the front position point and the front position point can be a point in the two-dimensional coordinates, and the second positioning error value of the rear position point and the rear position point can be another point in the two-dimensional coordinates, and the two points can obtain k and b values ​​according to Y=kX+b, thereby obtaining the second functional relationship.

[0095] Step S58: Determine the second positioning error value of the unmeasured position point between the front position point and the rear position point according to the second functional relationship. With the second functional relationship, after substituting the unmeasured position point between the front position point and the rear position point, the second positioning error value corresponding to the unmeasured position point can be obtained.

[0096] Step S70: Determine the thermal error value of the screw rod at different temperatures according to the first thermal error value and the second thermal error value; a mapping relationship of the thermal error value during the heating process and a mapping relationship of the thermal error value during the cooling process can be formed. For example, the first thermal error value is the thermal error value between any temperature in the heating process of the screw rod, any position point of the nut in the entire stroke and the first thermal error value. The screw rod is at different temperatures and the nut moves throughout the entire stroke. The second thermal error value is the thermal error value between any temperature in the cooling process of the screw rod, any position point of the nut in the entire stroke and the second thermal error value.

[0097] Step S90: Compensate the machine tool according to the thermal error values ​​of the screw rod at different temperatures. It can be understood that when the screw rod is in a heating state, the corresponding first thermal error value is found according to the position point at which the screw nut moves to a certain position in the stroke when the screw rod is at a certain temperature during the heating process, and then the first thermal error value is added or subtracted during actual processing, so that the error caused by the thermal expansion of the screw rod and the discrepancy between the actual position and the theoretical position can be eliminated.

[0098] The above-mentioned method for compensating the thermal error of the screw rod comprises the following steps: when the machine tool is in a processing state and the temperature of the screw rod is gradually increased from an initial temperature to a preset temperature, obtaining a first thermal error value of the screw rod at multiple preset temperatures; when the machine tool is in a processing state and the temperature of the screw rod is gradually reduced from a preset temperature to an initial temperature, obtaining a second thermal error value of the screw rod at multiple preset temperatures; determining the thermal error values ​​of the screw rod at different temperatures according to the first thermal error value and the second thermal error value; and compensating the machine tool according to the thermal error values ​​of the screw rod at different temperatures, so that the measured compensation value can be as close as possible to the actual value of the machine tool during actual processing, thereby improving the processing accuracy of the machine tool.

[0099] Please see Figure 1 According to a second aspect of the present invention, a compensation system for the thermal error of a screw rod is provided. The screw rod 100 is applied to a machine tool. The compensation system includes an acquisition module 310, a first thermal error value acquisition module 320, a second thermal error value acquisition module 330, a calculation module 340 and a compensation module 350.

[0100] The acquisition module 310 is used to obtain the temperature of the screw rod 100. It can be understood that there are three temperature states of the screw rod. The first is the initial temperature, which is the ambient temperature. The ambient temperature will change according to the changes in the environment in which the machine tool is located. The second is a certain temperature during the heating process. When the screw rod is working, friction will occur between it and the nut, and friction will generate heat. The heating process is the process in which the temperature of the screw rod rises from the initial temperature to the preset temperature. The third is a certain temperature during the cooling process. After the temperature of the screw rod rises, if it stops working, the temperature will drop. The cooling process is the process in which the temperature of the screw rod drops from the preset temperature to the initial temperature.

[0101] The first thermal error value acquisition module 320 is connected to the acquisition module 310, and is used to obtain the first thermal error value of the screw rod 100 at multiple preset temperatures when the machine tool is in a processing state and the temperature of the screw rod 100 gradually increases from an initial temperature to a preset temperature; by measuring the first thermal error value of the screw rod at multiple preset temperatures when the machine tool is in a processing state, it is possible to predict the error value of the screw rod at the temperature when the machine tool is installed with the screw rod, so as to make the first thermal error value as close to the actual value as possible.

[0102] The second thermal error value acquisition module 330 is connected to the acquisition module 310. When the machine tool is in a processing state and the temperature of the screw rod 100 is gradually reduced from a preset temperature to an initial temperature, the second thermal error value of the screw rod 100 at multiple preset temperatures is acquired. It can be understood that the expansion parameters of the screw rod are also different during the cooling process, so it is necessary to measure the second thermal error value during the cooling process.

[0103] The operation module 340 is connected to the first thermal error value acquisition module 320 and the second thermal error value acquisition module 330, and is used to determine the thermal error value of the screw rod 100 at different temperatures according to the first thermal error value and the second thermal error value; the thermal error value of the screw rod 100 at different temperatures in the heating state and the cooling state can be determined according to the first thermal error value and the second thermal error value.

[0104] The compensation module 350 is connected to the calculation module 340 and is used to compensate the machine tool according to the thermal error values ​​of the screw rod 100 at different temperatures.

[0105] The above-mentioned thermal error compensation system, through the acquisition module 310, the first thermal error value acquisition module 320, the second thermal error value acquisition module 330, the calculation module 340, and the compensation module 350, when the machine tool is in a processing state and the temperature of the screw rod gradually increases from the initial temperature to the preset temperature, obtains the first thermal error value of the screw rod at multiple preset temperatures; and when the temperature of the screw rod gradually decreases from the preset temperature to the initial temperature, obtains the second thermal error value of the screw rod at multiple preset temperatures; determines the thermal error values ​​of the screw rod at different temperatures according to the first thermal error value and the second thermal error value; and compensates the machine tool according to the thermal error values ​​of the screw rod at different temperatures, so that the measured compensation value can be as close as possible to the actual value of the machine tool during actual processing, thereby improving the processing accuracy of the machine tool.

[0106] It can be understood that, in the absence of conflict, the steps in the aforementioned compensation method can be applied to the compensation system of this embodiment to achieve the purpose of improving the positioning error of the machine tool and enhancing the machining accuracy of the machine tool.

[0107] The third aspect of the present invention provides a machine tool, including a screw rod 100 and a nut 200, wherein the screw rod 100 is connected to the nut 200, and also includes a compensation system for the thermal error of the above-mentioned screw rod; the acquisition module 310 includes a temperature measuring component, which cooperates with the screw rod 100 to sense the temperature of the screw rod 100.

[0108] Since the machine tool of this embodiment includes the aforementioned compensation system, it also has the technical effects of the compensation system, which will not be described in detail here.

[0109] In some feasible implementations, the machine tool further includes a controller 400, and the controller 400 is connected to the compensation system.

[0110] The controller 400 is used to obtain the theoretical position point of the nut 200 .

[0111] The acquisition module 310 also includes a measuring device, which cooperates with the workpiece and is used to determine the actual position point of the nut 200 according to the size of the workpiece processed by the machine tool; in this embodiment, the measuring device can be a three-coordinate measuring machine.

[0112] The input end of the first thermal error value acquisition module 320 and the input end of the second thermal error value acquisition module 330 are both electrically connected to the acquisition module 310, the output end of the first thermal error value acquisition module 320 and the output end of the second thermal error value acquisition module 330 are both electrically connected to the operation module 340, and the operation module 340 is also electrically connected to the compensation module 350.

[0113] In some feasible implementations, the machine tool further includes a spindle 500 and a test workpiece 600, the test workpiece 600 includes a mounting body 610 and a plurality of cylinders 620 disposed concentrically in sequence on the mounting body 610, and the machine tool being in a processing state includes a state in which the machine tool is processing or preparing to process the plurality of cylinders 620 on the test workpiece 600; by providing a plurality of cylinders 620, a plurality of processing position points of the nut within the moving stroke can be set. And / or,

[0114] Please see Figure 1 The machine tool further comprises a base 700, a column 800, a driving member 900 and a turning tool 1000. The column 800 and the spindle 500 are installed on the base 700 at intervals. The driving member 900 is installed on the column 800. The driving member 900 is transmission-connected with the screw rod 100. The controller 400 is electrically connected with the driving member 900. The spindle 500 drives the test workpiece 600 to rotate. The driving member 900 drives the turning tool 1000 to move through the screw rod 100 and the nut 200 to process the workpiece through the turning tool 1000. During the turning process, the X distance moved by the turning tool 1000 is the distance in the moving stroke.

[0115] Obviously, those skilled in the art can make various changes and modifications to the present invention without departing from the spirit and scope of the present invention. Thus, if these modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include these modifications and variations.

[0116] The above examples are only preferred embodiments of the present invention, and certainly cannot be used to limit the scope of the present invention. Therefore, equivalent changes made according to the claims of the present invention still fall within the scope of the present invention.

Claims

1. A method for compensating thermal errors of a screw, wherein the screw is applied to a machine tool, characterized in that: include: Obtaining the temperature of the screw rod; When the machine tool is in a processing state and the temperature of the screw rod is gradually increased from an initial temperature to a preset temperature, obtaining a first thermal error value of the screw rod at a plurality of preset temperatures; When the machine tool is in a processing state and the temperature of the screw rod is gradually reduced from a preset temperature to an initial temperature, obtaining a second thermal error value of the screw rod at a plurality of preset temperatures; Determining the thermal error value of the screw rod at different temperatures according to the first thermal error value and the second thermal error value; The machine tool is compensated according to the thermal error values ​​of the screw rod at different temperatures.

2. The method for compensating the thermal error of the screw rod according to claim 1, characterized in that: The machine tool includes a nut connected to a screw rod, and the screw rod drives the nut to move by rotating; and obtaining a first thermal error value of the screw rod at a plurality of preset temperatures specifically includes: When the machine tool is in a processing state and the temperature of the screw rod is at an initial temperature, obtaining a plurality of initial positioning error values ​​of the screw rod when the nut is at a plurality of preset processing positions; Controlling the screw rod to heat up for the first time, when the machine tool is in a processing state and the temperature of the screw rod rises to a first intermediate temperature, obtaining a plurality of first intermediate positioning error values ​​of the screw rod when the nut moves to a plurality of preset processing positions; wherein each of the first intermediate positioning error values ​​is obtained by calculating a theoretical position point and an actual position point of the nut; Obtaining a plurality of first thermal error values ​​of the screw rod after the first heating according to a plurality of first intermediate positioning error values ​​and a plurality of initial positioning error values ​​of the screw rod; The screw rod is repeatedly controlled to heat up again, and a plurality of first thermal error values ​​after heating up again are recorded until the temperature of the screw rod rises to a preset temperature, thereby obtaining the first thermal error values ​​of the screw rod at a plurality of preset temperatures.

3. The method for compensating the thermal error of the screw rod according to claim 2, characterized in that: The obtaining of the second thermal error value of the screw rod at a plurality of preset temperatures specifically includes: When the temperature of the screw rod is at a preset temperature, the screw rod is controlled to be cooled for the first time, and when the machine tool is in a processing state and the temperature of the screw rod is at a second intermediate temperature, a plurality of second intermediate positioning error values ​​of the screw rod when the nut moves to a plurality of preset processing positions are obtained; wherein each of the second intermediate positioning error values ​​is obtained by calculating a theoretical position point and an actual position point of the nut; Obtaining a plurality of second thermal error values ​​of the screw rod after the first cooling according to the plurality of second intermediate positioning error values ​​and the plurality of initial positioning error values ​​of the screw rod; The screw rod is repeatedly controlled to cool down again, and the second thermal error value after cooling down again is recorded until the temperature of the screw rod is reduced to the initial temperature, thereby obtaining the second thermal error value of the screw rod at multiple preset temperatures.

4. The method for compensating the thermal error of the screw rod according to claim 3, characterized in that: The step of obtaining a first thermal error value of the screw rod at a plurality of preset temperatures further includes: When the machine tool is in a processing state and the temperature of the screw rod is respectively at an initial temperature, a plurality of intermediate temperatures and a preset temperature, obtaining a front position point and a rear position point of each two adjacent processing positions of the nut; Obtaining a first positioning error value of the screw rod corresponding to a front position point and a first positioning error value corresponding to a rear position point; Determine a first functional relationship between a first positioning error value between a front position point and a rear position point and a processing position according to the first positioning error values ​​of the front position point and the rear position point; A first positioning error value of an unmeasured position point between the front position point and the rear position point is determined according to the first functional relationship.

5. The method for compensating the thermal error of a screw rod according to claim 4, characterized in that: Obtaining a second thermal error value of the screw rod at a plurality of preset temperatures specifically includes: When the machine tool is in a processing state and the temperature of the screw rod is at an intermediate temperature from a preset temperature to an initial temperature, obtaining a front position point and a rear position point of each two adjacent processing positions of the screw nut; Obtaining a second positioning error value of the screw rod corresponding to the front position point and a second positioning error value corresponding to the rear position point; Determine a second functional relationship between the second positioning error value of the front position point and the rear position point and the processing position according to the second positioning error value of the front position point and the rear position point; A second positioning error value of an unmeasured position point between the front position point and the rear position point is determined according to the second functional relationship.

6. The method for compensating the thermal error of a screw rod according to any one of claims 2 to 5, characterized in that: The obtaining of a plurality of initial positioning error values ​​of the screw rod when the screw nut is at a plurality of preset processing positions specifically includes: Obtaining a moving stroke of the nut, wherein the moving stroke includes an initial position and an end position; When the temperature of the screw rod is at the initial temperature, the nut is controlled to move a certain distance from the initial position and then repeatedly move until the nut moves to the end position, and each time the nut moves a certain distance, the machine tool processes the workpiece once; Get the theoretical position point after the nut moves a certain distance; According to the size of the corresponding workpiece processed by the machine tool after the nut moves a certain distance, the actual position point of the nut is determined; According to the theoretical position point and the actual position point after the nut moves a certain distance each time, the initial positioning error value after the nut moves a certain distance each time is determined to obtain a plurality of initial positioning error values ​​of the screw rod.

7. A screw rod thermal error compensation system, wherein the screw rod (100) is applied to a machine tool, characterized in that: The compensation system comprises: An acquisition module (310), used for acquiring the temperature of the screw rod (100); A first thermal error value acquisition module (320) is connected to the acquisition module (310) and is used to acquire a first thermal error value of the screw rod (100) at a plurality of preset temperatures when the machine tool is in a processing state and the temperature of the screw rod (100) gradually increases from an initial temperature to a preset temperature; A second thermal error value acquisition module (330) is connected to the acquisition module (310), and when the machine tool is in a processing state and the temperature of the screw rod (100) is gradually reduced from a preset temperature to an initial temperature, acquires a second thermal error value of the screw rod (100) at a plurality of preset temperatures; A calculation module (340) connected to the first thermal error value acquisition module (320) and the second thermal error value acquisition module (330), and used to determine the thermal error value of the screw rod (100) at different temperatures according to the first thermal error value and the second thermal error value; The compensation module (350) is connected to the calculation module (340) and is used to compensate the machine tool according to the thermal error values ​​of the screw rod (100) at different temperatures.

8. A machine tool, comprising a screw rod (100) and a nut (200), wherein the screw rod (100) is connected to the nut (200), characterized in that: It also includes a compensation system for the thermal error of the screw rod as described in claim 7; the acquisition module (310) includes a temperature measuring component, which cooperates with the screw rod (100) to sense the temperature of the screw rod (100).

9. The machine tool according to claim 8, characterized in that The machine tool further comprises a controller (400), wherein the controller (400) is connected to the compensation system; The controller (400) is used to obtain a theoretical position point of the nut (200); The acquisition module (310) also includes a measuring piece, which cooperates with the workpiece and is used to determine the actual position point of the nut (200) according to the size of the workpiece processed by the machine tool; The input end of the first thermal error value acquisition module (320) and the input end of the second thermal error value acquisition module (330) are both electrically connected to the acquisition module (310), the output end of the first thermal error value acquisition module (320) and the output end of the second thermal error value acquisition module (330) are both electrically connected to the operation module (340), and the operation module (340) is also electrically connected to the compensation module (350).

10. The machine tool according to claim 8, characterized in that The machine tool further comprises a spindle (500) and a test workpiece (600), the test workpiece (600) comprising a mounting body (610) and a plurality of cylinders (620) disposed on the mounting body (610) and disposed concentrically in sequence, and the machine tool being in a processing state comprises a state in which the machine tool is processing or preparing to process the plurality of cylinders (620) on the test workpiece (600); and / or, The machine tool further comprises a base (700), a column (800), a driving member (900) and a turning tool (1000); the column (800) and the spindle (500) are installed on the base (700) at intervals; the driving member (900) is installed on the column (800); the driving member (900) is transmission-connected to the screw rod (100); the controller (400) is electrically connected to the driving member (900); the spindle (500) drives the test workpiece (600) to rotate; the driving member (900) drives the turning tool (1000) to move through the screw rod (100) and the nut (200) so as to process the workpiece through the turning tool (1000).

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