Method and device for rapidly testing precision and rigidity retentivity of machine tool

Abstract

The invention discloses a machine tool precision and rigidity retentivity rapid test method and device, and relates to the technical field of numerical control machine tool performance test.The test method comprises the steps that a static and dynamic force loading test is conducted on a tested machine tool; measuring degradation data of each precision and rigidity of the machine tool; converting the accelerated degradation data to a conventional working condition; and calculating each precision and rigidity retention degree of the machine tool. The testing device comprises a lower platform, an electric cylinder, an electric cylinder fixing tool, a hooke joint, an upper platform, a cutter handle clamp and a simulation cutter handle, and is used for synchronously loading static and dynamic forces in X, Y and Z directions of a tested machine tool. Based on simulation and acceleration of actual service conditions of the vertical machining center, the method and the device can realize on-machine, synchronous and rapid testing of precision and rigidity retentivity of the vertical machining center, and provide test technical support for improvement of performance retention capability of domestic machine tools.

Description

Technical Field

[0001] The invention relates to the technical field of numerical control machine tool performance testing, and in particular to a method and a device for quickly testing the accuracy and rigidity retention of a machine tool. Background Art

[0002] Precision and rigidity are two key performances of machine tools. Precision determines the level of machining accuracy of machine tools, and rigidity determines the strength of machine tool machining capabilities. At present, preliminary explorations have been carried out at home and abroad on the test methods for the precision retention of machine tool functional components, but few people have mentioned the test of machine tool rigidity retention. Patent CN104020716A discloses a detection device for the precision retention of a CNC turntable, which realizes the detection of the precision retention of a CNC turntable by simulating the actual cutting load on the test bench. Patent CN108972149A discloses a CNC tool holder machining accuracy and rotation accuracy retention test device and detection method, which are used to accurately simulate the actual cutting force of the CNC tool holder to test the machining accuracy and rotation accuracy retention. Patent CN109406143A discloses a ball screw pair precision retention test device and method based on real working conditions, which are used to test the degradation of the accuracy of the ball screw pair of a machine tool under real load conditions. Patent CN116804591A discloses a precision retention test bench for multiple parallel linear guide pairs under variable loads, which is used to simultaneously accelerate the precision degradation process of multiple linear guide pairs.

[0003] After years of development, the initial manufacturing accuracy and rigidity of domestic high-end machine tool products have gradually approached the advanced level of foreign countries. However, compared with foreign high-end products, the ability of domestic machine tools to maintain their initial manufacturing level during service (i.e., the retention of accuracy and rigidity) is still relatively weak. During service, the decline of machine tool accuracy and rigidity shows long-term slow change and nonlinear characteristics. The traditional on-site tracking test method is too inefficient and the test time is as long as several months to several years.

[0004] Through the analysis of the existing research on the accuracy and stiffness retention test of machine tools, it is found that: (1) the current application of relevant testing technologies is limited to functional components such as CNC turntables, CNC tool holders, ball screws and rolling guides, and there is a lack of relevant testing technology research at the level of machine tools; (2) the existing testing methods are all carried out on the test bench, and there is a lack of loading devices that can simulate cutting loads on the machine; (3) there is still a lack of research on the test methods for machine tool stiffness retention, and no one has mentioned the simultaneous test methods for accuracy and stiffness retention. At present, there is still a lack of rapid testing methods and devices for the accuracy and stiffness retention of machine tools in China. Therefore, it is urgent to invent a rapid testing method and device for machine tool accuracy and stiffness retention to achieve the rapid acquisition of the accuracy and stiffness retention level of the machine tool in a short period of time. Summary of the invention

[0005] The purpose of the present invention is to provide a method and device for quickly testing the accuracy and rigidity retention of a machine tool, so as to solve the problems raised in the above-mentioned background technology.

[0006] In order to solve the above technical problems, the present invention provides the following technical solutions: a method for rapid testing of machine tool accuracy and rigidity retention, which realizes synchronous and rapid testing of the accuracy and rigidity retention of the whole machine tool, comprising the following steps:

[0007] Step 1: Perform static and dynamic force loading tests on the machine tool under test;

[0008] Step 2: measuring the degradation data of various precision and stiffness of the machine tool;

[0009] Step 3, converting the accelerated degradation data to normal working conditions;

[0010] Step 4: Calculate the accuracy and rigidity retention of the tool.

[0011] The present invention further describes that according to the maximum feed speed v of each axis of the machine tool max , Maximum feed resistance F max and the maximum spindle speed V max , set 3 loading levels, load the machine tool in turn according to the 3 loading levels, and set the loading time of each load level to H;

[0012] Among them, the three loading levels are S1, S2, and S3, and H is 40h.

[0013] The present invention further illustrates that equal time interval measurements are performed, the measurement interval is set to T, loading is stopped after each loading T time, and instruments are used to measure and record the positioning accuracy of the X, Y, and Z axes of the machine tool, the straightness of the X-axis in the Y direction, the straightness of the X-axis in the Z direction, the straightness of the Y-axis in the X direction, the straightness of the Y-axis in the Z direction, the straightness of the Z-axis in the X direction, the straightness of the Z-axis in the Y direction, and the degradation data of the static stiffness of the X, Y, and Z axes;

[0014] T is set to 8h, and measurements are taken 5 times under each load level. After the data measurement is completed, loading continues, and loading and measurement are repeated until the total loading time reaches the set 120h, and the test is terminated.

[0015] The present invention further illustrates that the specific method of step three is:

[0016] Power law function Fit the degradation trajectories of various precision and stiffness to obtain the degradation functions of various precision and stiffness over time at various accelerated stress levels;

[0017] Based on the three-stress acceleration model, the relationship between the degradation trajectory parameters a, b and the stress level is obtained, and the values ​​of the parameters a, b of the accuracy and stiffness degradation trajectory equations of the machine tool under conventional working conditions are solved to realize the conversion of accelerated degradation data to conventional degradation data.

[0018] The present invention further illustrates that the three-stress acceleration model is:

[0019] lnη(α0,α1,α2,α3,α4,α5)=lnα0-α1ζ1-α2ζ2-α3ζ3-α4ζ1ζ2-α5ζ1ζ3

[0020] Among them, η is the degradation trajectory parameter, ζ1, ζ2, and ζ3 represent the stress levels of feed speed, static force, and dynamic force, respectively, and α0, α1, α2, α3, α4, and α5 are unknown parameters, which are solved according to the degradation data at each stress level.

[0021] The present invention further illustrates that the step 4 uses the following formula to calculate the accuracy and rigidity retention of the tool:

[0022]

[0023] In the formula, To maintain the degree function; is the degradation function under normal working conditions; is the failure threshold of each accuracy and stiffness.

[0024] A rapid testing device for machine tool accuracy and rigidity retention comprises a lower platform, an electric cylinder, an electric cylinder fixing fixture, a Hooker reamer, an upper platform, a tool holder fixture, and a simulated tool holder, and is used to realize synchronous loading of static and dynamic forces in three directions, X, Y, and Z, of a machine tool under test.

[0025] The present invention further illustrates that the tool handle fixture includes a three-dimensional force sensor, a locking nut, a bearing seat, a tool handle sleeve, a tool handle end cover, and a bearing;

[0026] Among them, the three-dimensional force sensor is fixed to the upper platform by bolts, the bearing seat is connected to the three-dimensional force sensor by bolts, the tool handle sleeve and the bearing seat are connected by a bearing, and the bearing is fixed by the locking nut, the tool handle sleeve is threadedly connected to the simulated tool handle, and the simulated tool handle is further fixed by the tool handle end cover.

[0027] Compared with the prior art, the beneficial effects achieved by the present invention are:

[0028] 1) The present invention proposes a full-process method for rapid testing of various precision and rigidity retention of machine tools based on static and dynamic load loading, which covers test methods, data processing methods and evaluation methods, and can realize synchronous and rapid testing of the precision and rigidity retention of the whole machine tool, greatly reducing time cost and material consumption;

[0029] 2) Based on the above test method, the present invention designs a rapid test device for the accuracy and rigidity retention of a vertical machining center from the perspective of simulating actual cutting loads, which can realize on-machine synchronous loading of static and dynamic forces in the three directions of X, Y, and Z of the machine tool under test. BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The accompanying drawings are used to provide a further understanding of the present invention and constitute a part of the specification. Together with the embodiments of the present invention, they are used to explain the present invention and do not constitute a limitation of the present invention. In the accompanying drawings:

[0031] Figure 1 It is a flow chart of the rapid testing method of machine tool accuracy and rigidity retention;

[0032] Figure 2 It is a schematic diagram of the overall structure of a rapid testing device for machine tool accuracy and rigidity retention;

[0033] Figure 3 This is a schematic diagram of the tool holder fixture structure of a rapid testing device for machine tool accuracy and rigidity retention;

[0034] In the figure: 1. Lower platform; 2. Electric cylinder; 3. Electric cylinder fixing tool; 4. Hook reamer; 5. Upper platform; 6. Tool holder fixture; 7. Simulated tool holder; 8. Three-dimensional force sensor; 9. Locking nut; 10. Bearing seat; 11. Tool holder sleeve; 12. Tool holder end cover; 13. Bearing. DETAILED DESCRIPTION

[0035] The following is a further non-limiting detailed description of the technical solution of the present invention in conjunction with the preferred embodiments and the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, not all of the embodiments. Based on the embodiments of the present invention, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of the present invention.

[0036] Taking the rapid test of various precision and rigidity retention of a three-axis vertical machining center as an example, the implementation mode of the present invention is described in detail.

[0037] See also Figure 1 The present invention provides a technical solution: a method for quickly testing the accuracy and rigidity retention of a machine tool, comprising the following steps:

[0038] Step 1: Perform static and dynamic force loading tests at multiple loading levels on the machine tool under test according to the maximum operating parameters of the machine tool;

[0039] Step 2, measuring the degradation data of various precision and rigidity of the machine tool at a set time;

[0040] Step 3: Use function fitting to calculate the degradation trajectory and convert the accelerated degradation data to normal working conditions;

[0041] Step 4: Calculate the accuracy and stiffness retention of the tool according to the degradation data.

[0042] See also Figure 2 The test device used to implement the above test method includes a lower platform 1, an electric cylinder 2, an electric cylinder fixing fixture 3, a Hooker reamer 4, an upper platform 5, a tool holder fixture 6, and a simulated tool holder 7, which can realize the synchronous loading of the static and dynamic forces in the three directions of X, Y, and Z of the tested machine tool, and meet the rapid test requirements of the accuracy and rigidity retention of the above machine tools;

[0043] See also Figure 3 The tool handle fixture 6 includes a three-dimensional force sensor 8, a locking nut 9, a bearing seat 10, a tool handle jacket 11, a tool handle end cover 12, and a bearing 13;

[0044] The three-dimensional force sensor 8 is fixed to the upper platform 5 by bolts, and the bearing seat 10 is connected to the three-dimensional force sensor 8 by bolts; the tool handle sleeve 11 and the bearing seat 10 are connected by a bearing 13, and the bearing 13 is fixed by a locking nut 9; the tool handle sleeve 11 is connected to the simulated tool handle 7 by threads, and the simulated tool handle 7 is further fixed by the tool handle end cover 12;

[0045] Furthermore, when the test device is in use, the lower platform 1 is fixed on the workbench of the machine tool, the simulated tool handle 7 is connected to the main shaft of the machine tool, and the Hooker hinge 4 is driven by three electric cylinders 2 to drive the upper platform 5 and the simulated tool handle 7 to synchronously apply static and dynamic loads in the three directions of X, Y, and Z to the machine tool, thereby completing the installation of the test device.

[0046] Specifically, the specific method for performing static and dynamic force loading tests on the machine tool under test in step 1 is:

[0047] The test device in this scheme is installed on a three-axis vertical machining center, and the specific contents of the installation of the test device are referred to above.

[0048] According to the operating parameters of the maximum feed speed, maximum feed resistance and maximum spindle speed of the machine tool X, Y and Z axes, three loading load level levels are set, namely S1, S2 and S3. Table 1 shows the method for selecting the loading load level values;

[0049] Table 1 Method for selecting loading load level values

[0050]

[0051] Preferably, v max Set the maximum feed speed of each axis of X, Y, and Z to 36m / min. max Set the maximum feed resistance of X, Y, and Z axes to 3000N, 3000N, and 2000N respectively. max Set the maximum spindle speed to 6000rpm;

[0052] Specifically, in S1, the X, Y, and Z axis feed speeds were set to 9, 9, and 9 m / min, respectively; the X, Y, and Z axis static forces were set to 750, 750, and 500 N, respectively; the X, Y, and Z axis dynamic force amplitudes were set to 150, 150, and 100 N, respectively; and the X, Y, and Z axis dynamic force frequencies were set to 10, 10, and 10 Hz, respectively;

[0053] In S2, the feed speeds of X, Y, and Z axes are set to 18, 18, and 18 m / min, respectively; the static forces of X, Y, and Z axes are set to 1500, 1500, and 1000 N, respectively; the amplitudes of dynamic forces of X, Y, and Z axes are set to 300, 300, and 200 N, respectively; and the frequencies of dynamic forces of X, Y, and Z axes are set to 20, 20, and 20 Hz, respectively;

[0054] In S3, the feed speeds of X, Y, and Z axes are set to 27, 27, and 27 m / min, respectively; the static forces of X, Y, and Z axes are set to 2250, 2250, and 1500 N, respectively; the amplitudes of dynamic forces of X, Y, and Z axes are set to 450, 450, and 300 N, respectively; and the dynamic force frequencies of X, Y, and Z axes are set to 30, 30, and 30 Hz, respectively;

[0055] The machine tool is loaded in sequence according to three loading levels, and the loading time of each load level is set to H, preferably H is 40h.

[0056] The specific method for measuring the degradation data of various precision and stiffness of the machine tool in step 2 is:

[0057] Carry out equal time interval measurement, set the measurement interval time to T, stop loading after each loading time T, use laser interferometer, static stiffness tester and other instruments and equipment to measure and record the degradation data of various precision and stiffness of the machine tool, including the positioning accuracy of each axis of X, Y, and Z, the straightness of the X-axis in the Y direction, the straightness of the X-axis in the Z direction, the straightness of the Y-axis in the X direction, the straightness of the Y-axis in the Z direction, the straightness of the Z-axis in the X direction, the straightness of the Z-axis in the Y direction, and the degradation data of the static stiffness of each axis of X, Y, and Z;

[0058] For example, if T is set to 8h, and each load level is loaded for 40h, measurements are taken 5 times under each load level. After the data measurement is completed, loading is continued, and loading and measurement are repeated until the total loading time reaches the set 120h, and the test is terminated.

[0059] The specific method for converting the accelerated degradation data to normal working conditions in step 3 is:

[0060] According to the degradation data measured in step 2, a power law function is used to fit the degradation trajectory of each accuracy and stiffness to obtain the degradation function of each accuracy and stiffness over time under each accelerated stress level. In the formula, a and b are unknown parameters, which are solved according to the degradation data;

[0061] Using the three stress acceleration model:

[0062] lnη(α0,α1,α2,α3,α4,α5)=lnα0-α1ζ1-α2ζ2-α3ζ3-α4ζ1ζ2-α5ζ1ζ3

[0063] The relationship between the degradation trajectory parameters a, b and the stress level is obtained, and the values ​​of the parameters a and b of the degradation trajectory equations of various precision and stiffness of the machine tool under conventional working conditions are solved to realize the conversion of accelerated degradation data to conventional working condition degradation data; where η is the degradation trajectory parameter; ζ1, ζ2, ζ3 represent the stress levels of feed speed, static force, and dynamic force, respectively; α0, α1, α2, α3, α4, α5 are unknown parameters, which are solved according to the degradation data under each stress level.

[0064] The specific method for calculating the accuracy and rigidity retention of the tool machine in step 4 is:

[0065] According to the degradation trajectory equations of various machine tool precision and stiffness under normal working conditions obtained in step 3, the following formula is used to calculate the machine tool precision and stiffness retention:

[0066]

[0067] In the formula, To maintain the degree function; is the degradation function under normal working conditions; is the failure threshold of each accuracy and stiffness.

[0068] Finally, it should be pointed out that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them. Although the present invention has been described in detail with reference to the above embodiments, a person skilled in the art should understand that the technical solutions described in the above embodiments can still be modified, or some of the technical features can be replaced by equivalents, and these modifications or replacements do not deviate the essence of the corresponding technical solutions from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A method for rapid testing of machine tool accuracy and rigidity retention, characterized in that: The following steps are involved: Step 1: Perform static and dynamic force loading tests on the machine tool under test; Step 2: measuring the degradation data of various precision and stiffness of the machine tool; Step 3, converting the accelerated degradation data to normal working conditions; Step 4: Calculate the accuracy and rigidity retention of the tool.

2. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 1, characterized in that: The specific method of step one is: According to the operating parameters of the maximum feed speed of each axis of the machine tool, the maximum feed resistance and the maximum spindle speed, three loading load levels are set, and the machine tool is loaded in turn according to the three loading load levels. The loading time of each load level is set to H.

3. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 2, characterized in that: The specific method of step 2 is: Carry out equal time interval measurement, set the measurement interval time to T, stop loading after each loading time T, use instruments and equipment to measure and record the degradation data of various precision and stiffness of the machine tool; After the data measurement is completed, continue loading, and repeat the loading and measurement until the total loading time reaches the set value of 3H, and the test is ended.

4. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 1 or 3, characterized in that: The degradation data include the positioning accuracy of each axis, the straightness of each axis in the other two directions, and the static stiffness of each axis.

5. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 1, characterized in that: The specific method of step three is: Power law function Fit the degradation trajectories of various precision and stiffness to obtain the degradation functions of various precision and stiffness over time at various accelerated stress levels; Based on the three-stress acceleration model, the relationship between the degradation trajectory parameters a, b and the stress level is obtained, and the values ​​of the parameters a, b of the accuracy and stiffness degradation trajectory equations of the machine tool under conventional working conditions are solved to realize the conversion of accelerated degradation data to conventional degradation data.

6. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 5, characterized in that: The three-stress acceleration model is: lnη(α0,α1,α2,α3,α4,α5)=lnα0-α1ζ1-α2ζ2-α3ζ3-α4ζ1ζ2-α5ζ1ζ3 Among them, η is the degradation trajectory parameter, ζ1, ζ2, and ζ3 represent the stress levels of feed speed, static force, and dynamic force, respectively, and α0, α1, α2, α3, α4, and α5 are unknown parameters, which are solved according to the degradation data at each stress level.

7. A method for rapid testing of machine tool accuracy and rigidity retention according to claim 6, characterized in that: The fourth step uses the following formula to calculate the accuracy and rigidity of the tool: In the formula, To maintain the degree function; is the degradation function under normal working conditions; is the failure threshold of each accuracy and stiffness.

8. A rapid testing device for machine tool accuracy and rigidity retention, suitable for the testing method according to any one of claims 1 to 7, characterized in that: The invention comprises a lower platform (1), an electric cylinder (2), an electric cylinder fixing fixture (3), a Hooke's reamer (4), an upper platform (5), a tool holder fixture (6), and a simulated tool holder (7), and is used for realizing synchronous loading of static and dynamic forces in three directions, X, Y, and Z, of a machine tool to be tested.

9. A rapid testing device for machine tool accuracy and rigidity retention according to claim 8, characterized in that: The tool handle fixture (6) comprises a three-dimensional force sensor (8), a locking nut (9), a bearing seat (10), a tool handle sleeve (11), a tool handle end cover (12), and a bearing (13); The three-dimensional force sensor (8) is fixed to the upper platform (5) by bolts, the bearing seat (10) is connected to the three-dimensional force sensor (8) by bolts, the tool handle sleeve (11) and the bearing seat (10) are connected by a bearing (13), and the bearing (13) is fixed by the locking nut (9), the tool handle sleeve (11) is connected to the simulated tool handle (7) by threads, and the simulated tool handle (7) is further fixed by the tool handle end cover (12).

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