Accelerated test method and device for precision retentivity and reliability of numerical control milling head

Abstract

The invention discloses an accelerated test method and device for precision retentivity and reliability of a numerical control milling head, and relates to the technical field of mechanical tests. The test device comprises a numerical control milling head, a vibration loading device installed below the numerical control milling head, a follow-up dynamic / static force loading device installed above the vibration loading device, a lifting supporting device installed on the outer side of the follow-up dynamic / static force loading device, and an operation table installed on one side of the vibration loading device. The method comprises the following steps: installing and positioning the numerical control milling head into the high and low temperature loading device, and adjusting the spatial height of the numerical control milling head to reach a preset position; carrying out stress combined loading tests of temperature, vibration, speed, static / dynamic force and electromagnetism on the tested numerical control milling head; various precision degradation data and fault data of the numerical control milling head are measured and recorded; and the precision retentivity and the reliability level of the numerical control milling head can be quickly obtained in a short time.

Description

Technical Field

[0001] The invention relates to the technical field of mechanical testing, and in particular to a method and a device for accelerating the testing of the precision retention and reliability of a numerically controlled milling head. Background Art

[0002] In the technological development in recent years, domestic CNC milling heads have acquired functions such as high-speed stable rotation and high-precision positioning, and have a high initial accuracy, which is close to the advanced level abroad; however, compared with foreign advanced machine tool companies, there is still a significant gap in the accuracy retention and reliability of domestic CNC milling heads; the traditional on-site tracking test method in a service environment is too inefficient, and the tracking test process can take months or even years.

[0003] Domestic and foreign research has mainly focused on the thermal characteristics and structural design optimization of CNC milling heads, but less research has been conducted on accuracy retention and reliability. The analysis of related test research on CNC milling head accuracy retention and reliability testing found that: (1) Research on related testing technologies such as CNC turntables and CNC tool holders has been carried out, but there is still a lack of CNC milling head accuracy retention test methods and equipment; (2) Existing test methods are all carried out under conventional stress, and temperature, vibration, electromagnetic and other influencing factors are not considered during loading. The cycle for obtaining CNC milling head accuracy degradation data and fault data is relatively long.

[0004] At present, there is still a lack of research and development of accelerated testing methods and devices for the accuracy retention and reliability of CNC milling heads in China. Therefore, it is urgent to invent an accelerated testing method and device for the accuracy retention and reliability of CNC milling heads, so as to quickly obtain the accuracy retention and reliability level of CNC milling heads 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 accelerating the test of the accuracy retention and reliability of a numerically controlled milling head, 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 accelerating the accuracy retention and reliability test of a CNC milling head, comprising the following steps:

[0007] Step 1, install and position the CNC milling head and adjust its spatial height to a preset position;

[0008] Step 2, performing temperature, vibration, speed, static / dynamic force, and electromagnetic multi-stress loading tests on the CNC milling head under test;

[0009] Step 3, measuring and recording various precision degradation data and fault data of the CNC milling head;

[0010] Step 4: Calculate the accuracy retention and reliability levels of the CNC milling head, and make an objective evaluation of the accuracy retention and reliability of the CNC milling head.

[0011] The present invention further illustrates that in step 2, n levels of stress levels are set, n≥3, and the load loading time of each stress level is T, T is preferably 120h, and the loading stress values ​​at each stress level are determined based on the temperature change of the CNC milling head under the service condition, the vibration signal transmitted by the whole machine tool, the maximum feed speed vmax of each rotating feed axis, the maximum spindle speed Vmax, the maximum spindle feed resistance Fmax, and the maximum magnetic field strength that the motor can withstand.

[0012] The present invention further illustrates that, at each stress level in step 2, each pair of CNC milling heads is subjected to a cycle of stress loading, and various precision degradation data of the CNC milling heads and fault data during the loading test are measured and recorded once.

[0013] The present invention further states that each level of stress level includes temperature range, vibration magnitude, feed speed of the rotary feed axis, spindle speed, static / dynamic force amplitude, frequency, and applied magnetic field strength test level;

[0014] The temperature range is recorded as △Ti, i is 1 to n, i represents the corresponding stress level, when i is larger, the difference in the temperature range is larger, △Tn is set to 0 to 40°C, and △Ti is determined within 0 to 40°C.

[0015] The vibration magnitude level and magnetic field strength test level are consistent with the stress level level;

[0016] The feed speed of the rotary feed axis is set to θi·vmax, vmax is the maximum feed speed, θi is the first value coefficient, and the value range of θi is 20%-70%; the spindle speed is set to §i·Vmax, Vmax is the maximum spindle speed, §i is the second value coefficient, and the value range of §i is 10%-50%; the static / dynamic force amplitude is set to βi·Fmax, Fmax is the maximum spindle feed resistance, βi is the third value coefficient, and the value range of βi is 25%-75%; the frequency is set to αi·Vmax / 60Hz, αi is the fourth value coefficient, and the value range of αi is 2.5%-7.5%;

[0017] Among them, θi, §i, βi, and αi will increase as the stress level i increases.

[0018] When N=3, the 3-level stress level is as follows;

[0019] The stress level of level 1 is set as follows: temperature range is △T1, vibration level is set to 50%, feed speed of rotary feed axis is set to 20% vmax, spindle speed is set to 10% Vmax, static / dynamic force amplitude is set to 25% of the maximum spindle feed resistance, frequency is set to 2.5% Vmax / 60Hz, plus level 1 magnetic field strength test level;

[0020] The stress level of level 2 is set as follows: temperature range is △T2, vibration level is set to 75%, feed speed of rotary feed axis is set to 50% vmax, spindle speed is set to 30% Vmax, static / dynamic force amplitude is set to 50% of the maximum feed resistance of spindle, frequency is set to 5% Vmax / 60Hz, plus level 2 magnetic field strength test level;

[0021] The level 3 stress level is set as follows: temperature range is △T3, vibration level is set to 100%, feed speed of rotary feed axis is set to 70% vmax, spindle speed is set to 50% Vmax, static / dynamic force amplitude is set to 75% of the maximum spindle feed resistance, frequency is set to 7.5% Vmax / 60Hz, plus level 3 magnetic field strength test level.

[0022] The present invention further illustrates that the maximum feed speed vmax is preferably 160° / sec, the maximum spindle speed Vmax is preferably 24000rpm, the maximum spindle feed resistance under static state is preferably 2000N, and the maximum spindle feed resistance under dynamic state is preferably 400N; the magnetic field strength that the motor can withstand is 1A / m~10A / m; the temperature range of the three levels of internal stress levels is expanded successively.

[0023] The present invention further illustrates that loading is performed for 120 hours at different stress levels:

[0024] ① Simultaneously apply vibration stress and temperature stress to the CNC milling head; load setting time;

[0025] ② Simultaneously apply temperature stress, speed stress and static force to the CNC milling head; load setting time;

[0026] ③ Simultaneously apply temperature stress and dynamic force to the CNC milling head; load setting time;

[0027] ④ Simultaneously apply speed stress and electromagnetic stress to the CNC milling head; load setting time;

[0028] ⑤ Adjust the high and low temperature loading device so that the CNC milling head reaches 20℃ and is in a balanced state;

[0029] ⑥ Use corresponding instruments and equipment to carry out various precision tests on the CNC milling head to obtain the degradation data of the CNC milling head; record the fault data of the CNC milling head during the loading test, and repair the faulty parts in time;

[0030] ⑦ Repeat steps ① to ⑥ until the current stress level loading test completes the preset cycle, adjust the stress level, and repeat the above loading test steps until the total loading time reaches the specified time.

[0031] The present invention further illustrates that the step 4 specifically includes using the various precision degradation data and fault data of the CNC milling head collected in the above steps to objectively evaluate the precision retention level and reliability level of the CNC milling head through the following formula;

[0032] The accuracy retention is evaluated as follows:

[0033]

[0034] Where t is the degradation time, G(t) is the retention function, f(t) is the accuracy degradation function under normal working conditions, and M is the accuracy failure threshold of the CNC milling head.

[0035] The present invention further illustrates that the reliability evaluation is:

[0036]

[0037] MTBF is the mean time between failures, t all is the total test time, t f is the failure time, n f The number of fault occurrences.

[0038] Compared with the prior art, the beneficial effects achieved by the present invention are as follows: the present invention proposes an accelerated test method for the precision retention and reliability of a CNC milling head, completely explains the test process and the precision retention and reliability evaluation method, and can obtain the long-term degradation precision and fault data of the CNC milling head in a relatively short time, significantly reducing the time cost. BRIEF DESCRIPTION OF THE DRAWINGS

[0039] 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:

[0040] Figure 1 It is a schematic flow chart of the test method of the present invention;

[0041] Figure 2 is a schematic diagram of the test device of the present invention;

[0042] In the figure: 1. CNC milling head; 2. High and low temperature loading device; 3. Vibration loading device; 4. Static / dynamic force loading device; 5. Lifting support device; 6. Operating table; 7. Electromagnetic loading device. DETAILED DESCRIPTION

[0043] 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.

[0044] See also Figure 1-2 , the present invention provides a technical solution: a method for accelerating the accuracy retention and reliability of a CNC milling head, which is implemented based on a device for accelerating the accuracy retention and reliability of a CNC milling head, the device comprising a CNC milling head 1, to which a simulated tool holder is connected;

[0045] A vibration loading device 3 is installed below the CNC milling head 1 to simulate vibrations of different degrees under different conditions, and multiple vibration levels are set;

[0046] A static / dynamic force loading device 4 is installed above the vibration loading device 3, and a static / dynamic combined loading is performed on the CNC milling head 1 to more comprehensively test the performance of the material or structure under different working conditions. The lower end of the simulated tool handle is connected to the operation output end of the static / dynamic force loading device 4, and a force sensor is arranged at the connection for pressure data transmission. In addition, the static / dynamic force loading device 4 is set as a three-axis force loading structure, which is used to apply three-axis static / dynamic force to the CNC milling head, and the three-axis force loading structure adopts a gear rack structure for circular motion;

[0047] A lifting support device 5 is installed on the outer side of the static / dynamic force loading device 4, and the lifting support device 5 is connected to the CNC milling head 1 to adjust the height of the CNC milling head 1;

[0048] The output end of the lifting support device 5 connected to the CNC milling head 1 is equipped with an electromagnetic loading device 7 for providing electromagnetic stress of different levels;

[0049] An operating table 6 is installed on one side of the vibration loading device 3 to realize the control of each device and data reception;

[0050] A high and low temperature loading device 2 is slidably connected to the operating table 6 and is used to test the accuracy retention and reliability of the CNC milling head 1 under different temperature conditions.

[0051] Therefore, the above test method includes the following steps:

[0052] Step 1, installing and positioning the CNC milling head 1 into the high and low temperature loading device 2, and adjusting its spatial height to a preset position;

[0053] Specifically, the CNC milling head 1 is installed inside the high and low temperature loading device 2 and fixed to the lifting support device 5, and the lifting support device 5 is fixed to the table of the vibration loading device 3 by bolts;

[0054] According to the three-dimensional size of the CNC milling head 1, the CNC milling head 1 is driven to move into the working area of ​​the static / dynamic force loading device 4 by the up-and-down movement of the lifting support device 5;

[0055] Step 2, performing temperature, vibration, speed, static / dynamic force, and electromagnetic stress combination loading tests on the CNC milling head 1 under test;

[0056] Specifically, the loadings are: vibration and temperature stress loading; temperature, vibration and static force stress loading; temperature and dynamic force stress loading; speed and electromagnetic stress loading;

[0057] Step 3, measuring and recording various precision degradation data and fault data of the CNC milling head;

[0058] There are three stress levels, and stress loading tests under multiple combinations are performed at the corresponding stress levels; the loading time for each level is 120h;

[0059] Under each stress level, each pair of CNC milling heads is subjected to one cycle of stress loading, and the precision degradation data of the CNC milling heads and the failure data during the loading test are measured and recorded once.

[0060] Step 4: Calculate the accuracy retention and reliability levels of the CNC milling head, and make an objective evaluation of the accuracy retention and reliability of the CNC milling head.

[0061] Further, taking setting level 3 stress as an example;

[0062] The stress level of level 1 is set as follows: the temperature range is 15-25°C, the vibration level is set to level 1, the feed speed of the rotary feed axis is set to 32° / sec, the spindle speed is set to 2400rpm, the static / dynamic force amplitude is set to 500 / 100N, the frequency is set to 10Hz, and the applied magnetic field strength is 1A / m;

[0063] The stress level of level 2 is set as follows: the temperature range is 10-30°C, the vibration level is set to level 2, the feed speed of the rotary feed axis is set to 80° / sec, the spindle speed is set to 7200rpm, the static / dynamic force amplitude is set to 1000 / 200N, the frequency is set to 20Hz, and the applied magnetic field strength is 3A / m;

[0064] The level 3 stress level is set as follows: temperature range is 0-40°C, vibration level is set to level 3, feed speed of the rotary feed axis is set to 112° / sec, spindle speed is set to 12000rpm, static / dynamic force amplitude is set to 1500 / 300N, frequency is set to 30Hz, and external magnetic field strength is 10A / m.

[0065] Loading was performed for 120 h at different stress levels. For example,

[0066] ① Apply vibration stress and temperature stress to the CNC milling head at the same time; the loading time is 4h;

[0067] ② Apply temperature stress, speed stress and static force to the CNC milling head at the same time; the loading time is 6h;

[0068] ③ Apply temperature stress and dynamic force to the CNC milling head at the same time; the loading time is 6h;

[0069] ④ Apply velocity stress and electromagnetic stress to the CNC milling head at the same time; the loading time is 2h;

[0070] ⑤ Adjust the high and low temperature loading device so that the CNC milling head reaches 20℃ and is in a balanced state;

[0071] ⑥ Use laser interferometer, spindle error analyzer and other instruments to carry out various precision tests on the CNC milling head, obtain the degradation data such as the positioning accuracy and repeatability of the rotary feed axis of the CNC milling head, and the spindle rotation accuracy; record the fault type, fault time and other fault data of the CNC milling head during the loading test, and repair the faulty parts in time;

[0072] ⑦ Repeat steps ① to ⑥ until the current stress level loading test completes 5 cycles, adjust the stress level, and repeat the above loading test steps until the total loading time reaches the specified time.

[0073] Step 4 specifically includes using the various precision degradation data and fault data of the CNC milling head collected in the above steps to objectively evaluate the precision retention level and reliability level of the CNC milling head through the following formula;

[0074] The accuracy retention is evaluated as follows:

[0075]

[0076] Where t is the degradation time, G(t) is the retention function, f(t) is the accuracy degradation function under normal working conditions, and M is the accuracy failure threshold of the CNC milling head;

[0077] Reliability evaluation is:

[0078]

[0079] MTBF is the mean time between failures, t all is the total test time, t f is the failure time, n f The number of fault occurrences.

[0080] 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 accelerating the accuracy retention and reliability of a numerically controlled milling head is implemented based on an accelerated testing device for the accuracy retention and reliability of a numerically controlled milling head, wherein the testing device comprises a numerically controlled milling head, a vibration loading device installed below the numerically controlled milling head, a static / dynamic force loading device installed above the vibration loading device, a lifting support device installed outside the static / dynamic force loading device, an operating table installed on one side of the vibration loading device, a high and low temperature loading device slidably connected to the operating table, and an electromagnetic loading device installed at the output end of the lifting support device, wherein a simulated tool handle is connected to the numerically controlled milling head; Features: The method comprises the following steps: Step 1, install and position the CNC milling head into the high and low temperature loading device, and adjust its spatial height to a preset position; Step 2, performing temperature, vibration, speed, static / dynamic force, and electromagnetic stress combined loading tests on the CNC milling head under test; Step 3, measuring and recording various precision degradation data and fault data of the CNC milling head; Step 4, calculate the accuracy retention level and reliability level of the CNC milling head, and make an objective evaluation of the accuracy retention and reliability of the CNC milling head.

2. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 1, characterized in that: In step 2, n stress levels are set, n≥3, and the load loading time of each stress level is T.

3. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 2, characterized in that: Each stress level includes temperature range, vibration level, feed speed of the rotary feed axis, spindle speed, static / dynamic force amplitude, frequency and external magnetic field strength test level.

4. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 3, characterized in that: The temperature range is recorded as △Ti, i ranges from 1 to n, i represents the corresponding stress level, and when i is larger, the difference in the temperature range is larger; Set △Tn to 0~40℃, and determine the temperature range of △Ti within 0~40℃.

5. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 3, characterized in that: The vibration magnitude levels and magnetic field strength test levels are consistent with the stress level levels.

6. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 3, characterized in that: The feed speed of the rotary feed axis is set to θi·vmax, where vmax is the maximum feed speed, θi is the first value coefficient, and the value range of θi is 20%-70%. θi will increase according to the increase of the stress level i.

7. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 3, characterized in that: The spindle speed is set to §i·Vmax, Vmax is the maximum spindle speed, §i is the second value coefficient, the value range of §i is 10%-50%, and §i will increase as the stress level i increases.

8. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 3, characterized in that: The static / dynamic force amplitude is set to βi·Fmax, where Fmax is the maximum feed resistance of the spindle, βi is the third value coefficient, and the value range of βi is 25%-75%. βi will increase as the stress level i increases.

9. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 7, characterized in that: The frequency is set to αi·Vmax / 60 Hz, αi is the fourth value coefficient, the value range of αi is 2.5%-7.5%, and αi will increase as the stress level i increases.

10. The method for accelerating the accuracy retention and reliability test of a CNC milling head according to claim 1, characterized in that: The accuracy retention and reliability evaluation formula in step 4 is as follows: The evaluation formula for accuracy retention is: Where t is the degradation time, G(t) is the retention function, f(t) is the accuracy degradation function under normal working conditions, and M is the accuracy failure threshold of the CNC milling head; The reliability evaluation formula is: MTBF is the mean time between failures, t all is the total test time, t f is the failure time, n f The number of fault occurrences.

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