A liquid nitrogen cooled machine tool drilling process

Abstract

The present application relates to the field of low-temperature drilling, and particularly relates to a liquid nitrogen cooling machining tool drilling process, comprising the following steps: determining an initial cutting speed and an initial feed speed according to a required hole machining depth and a required hole machining diameter of a target workpiece; detecting a tearing reference value of a target workpiece when the machining of the target workpiece is completed, and determining a machining adjustment mode according to the tearing reference value; determining whether to adopt a pre-drilling hole machining mode according to a quality reference value; in the pre-drilling hole machining mode, determining an initial pre-drilling depth and an initial pre-drilling frequency according to the quality reference value of a single batch of target workpieces; and determining the adjustment of the liquid nitrogen flow corresponding to the burr frequent area according to the preset burr distribution state in which the burr distribution state is located, or adjusting the pre-drilling diameter, the present application improves the setting accuracy of the drilling parameters of the drilling process, and further improves the drilling efficiency of the drilling work.

Description

Technical Field

[0001] This invention relates to the field of cryogenic drilling, and more particularly to a drilling process for machining tools cooled by liquid nitrogen. Background Technology

[0002] With the rapid development of high-end equipment manufacturing, the demand for processing quality of metal materials is also increasing. Some metal materials have characteristics such as low thermal conductivity and high coefficient of friction. Their cutting process generates a lot of cutting heat, which leads to local high temperature on the rake face of the tool, resulting in processing defects such as burrs or tears. Therefore, technicians invented ultra-low temperature cooling processing technology to achieve cooling during the processing to improve processing quality. Currently, there is liquid cooling ultra-low temperature cooling processing technology, which provides a solution to the problem of insufficient cooling efficiency in conventional cooling processing technology. However, in actual production, it is often impossible to adjust the processing parameters according to the actual processing effect, resulting in the processing parameters not being able to accurately meet the actual production needs, leading to low processing efficiency.

[0003] Chinese Patent Publication No. CN104260143A discloses a low-temperature drilling apparatus and method for resin-based fiber-reinforced composite materials. The apparatus consists of a low-temperature cooling device, a temperature control device, a cutting force measuring device, and a processing unit. This invention reduces defects such as delamination and burrs in the drilling of resin-based fiber-reinforced composite laminates under low-temperature conditions, improving the surface quality of the drilled laminates. Optimal low-temperature drilling parameters are adjusted by measuring and evaluating the cutting force. However, this method has the following problems: it cannot analyze and judge defects in a batch of processed parts, it does not consider adjusting parameters based on the distribution of burrs, and it cannot meet actual working requirements. Summary of the Invention

[0004] Therefore, the present invention provides a drilling process for machining tools cooled by liquid nitrogen, which overcomes the problems of poor machining efficiency caused by the inability to analyze and judge the defects of a batch of machined parts and the inability to adjust the machining parameters according to the different states of defects in the prior art.

[0005] To achieve the above objectives, the present invention provides a drilling process for machining tools cooled by liquid nitrogen, comprising:

[0006] Determine the initial cutting speed and initial feed rate based on the required hole machining depth and diameter of the target workpiece.

[0007] When the machining of a single target workpiece is completed, the tear reference value of the target workpiece is detected, and the machining adjustment method is determined based on the tear reference value. The machining adjustment method includes adjusting the cutting speed or adjusting the feed rate.

[0008] Periodically check the quality reference value for each batch of target processed parts, and determine whether to use the pre-drilling hole-making processing method based on the quality reference value;

[0009] In the pre-drilling hole-forming machining method, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch.

[0010] When both pre-drilling and single-drilling of a single target workpiece are completed, the residual thermal state of the target workpiece is detected to adjust the pre-drilling depth, or the burr distribution of the target workpiece is analyzed.

[0011] In the analysis of burr distribution, the liquid nitrogen flow rate corresponding to the area with frequent burrs is adjusted according to the preset burr distribution state, or the pre-drilling diameter is adjusted.

[0012] Furthermore, the initial cutting speed and initial feed rate are determined based on the required hole machining depth and diameter of the target workpiece.

[0013] The initial cutting speed and the initial feed speed are negatively correlated with the required hole machining depth of the target workpiece.

[0014] The initial cutting speed and the initial feed rate are positively correlated with the required hole diameter of the target workpiece.

[0015] Furthermore, when the processing of a single target workpiece is completed, the tear reference value of the target workpiece is detected, and the processing adjustment method is determined based on the tear reference value;

[0016] If the tear reference value is within the first preset tear reference value range, the cutting speed will be reduced.

[0017] If the tear reference value is within the second preset tear reference value range, the feed rate will be reduced.

[0018] Furthermore, quality reference values ​​are periodically tested for each batch of target processed parts, and the pre-drilling hole-forming processing method is determined based on the quality reference values.

[0019] If the quality reference value is within the first preset quality reference value range, pre-drilling is performed on the target workpiece to create a hole.

[0020] If the mass reference value is within the second preset mass reference value range, adjust the liquid nitrogen flow rate.

[0021] Furthermore, the formula for calculating the quality reference value is as follows:

[0022]

[0023] in, Ci is the number of drilling burrs in the i-th target workpiece, C0 is the average number of burrs, i = 1, 2, 3, ..., n, and n is the total number of target workpieces in a single batch.

[0024] Furthermore, in the pre-drilling hole-forming machining method, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch;

[0025] The initial pre-drilling depth and the initial number of pre-drilling operations are positively correlated with the quality reference value;

[0026] In the pre-drilling process, for a single target workpiece, a drill bit with a diameter half the required hole diameter is used to drill the target workpiece. The number of drilling operations is set to the initial pre-drilling operations, and the depth of each drilling operation is the same. When the total drilling depth reaches the initial pre-drilling depth, a drill bit with the required hole diameter is used to drill a hole in the target workpiece in a single operation. During the single drilling operation, the center axis of the drill bit coincides with the center axis of the drill bit in the pre-drilling process.

[0027] Furthermore, the residual thermal state of the target workpiece is detected during both pre-drilling and single-drilling operations for a single workpiece.

[0028] If the residual heat state is in the first preset residual heat state, the pre-drilling depth is increased.

[0029] If the residual heat state is in the second preset residual heat state, the burr distribution state of the target workpiece is analyzed.

[0030] Furthermore, the burr distribution of target parts processed by the pre-drilling hole-forming method in a single batch is periodically analyzed.

[0031] If the burr distribution is in the first preset burr distribution state, the liquid nitrogen flow rate corresponding to the burr frequent area is increased and adjusted.

[0032] If the burr distribution is in the second preset burr distribution state, adjust the pre-drilling diameter.

[0033] Furthermore, the first preset burr distribution state is that there is a drilling area where the proportion of the maximum height burrs is greater than the preset proportion. The liquid nitrogen flow rate is increased for the areas with frequent burrs, and the increase in liquid nitrogen flow rate is positively correlated with the proportion of the maximum height burrs.

[0034] Furthermore, the second preset burr distribution state is that the proportion of the maximum height burrs corresponding to the non-drilling area is greater than the preset proportion, and the pre-drilling diameter is increased accordingly.

[0035] The increase in pre-drilling diameter is positively correlated with the maximum burr height corresponding to the maximum height burr.

[0036] Compared with the prior art, the beneficial effects of the present invention are as follows: The technical solution of the present invention determines the initial cutting speed and initial feed rate based on the required hole machining depth and diameter of the target workpiece, ensuring that the initial cutting speed and initial feed rate meet the actual workpiece requirements. It periodically performs quality reference value checks on a single batch of target workpieces and determines whether to adopt a pre-drilling machining method based on the quality reference value. The quality reference value reflects whether the drilling quality meets the standards and also reflects the stability of burr defect generation during the drilling process of multiple parts. This makes the corresponding selected pre-drilling machining method, or the adjustment of liquid nitrogen flow rate, more consistent with the actual working scenario. The initial pre-drilling depth and initial pre-drilling count are determined based on the quality reference value of a single batch of target workpieces, making the pre-drilling machining parameters more accurate and avoiding efficiency reduction caused by redundant processes. The burr distribution status of the target workpieces processed by the pre-drilling machining method in a single batch is periodically statistically analyzed, making the adjustment of liquid nitrogen flow rate, or the adjustment of pre-drilling diameter, more consistent with the actual scenario. The present invention improves the accuracy of drilling parameter settings in the drilling process, thereby improving drilling efficiency. Attached Figure Description

[0037] Figure 1 This is a schematic diagram of the drilling process for machining tools using a liquid nitrogen cooling machine, according to an embodiment of the present invention.

[0038] Figure 2 This is a flowchart illustrating how the processing adjustment method is determined based on tear reference values, as described in an embodiment of the present invention.

[0039] Figure 3 This is a flowchart illustrating how to determine whether to use a pre-drilling hole-forming process based on a quality reference value, according to an embodiment of the present invention. Detailed Implementation

[0040] To make the objectives and advantages of the present invention clearer, the present invention will be further described below with reference to embodiments; it should be understood that the specific embodiments described herein are merely for explaining the present invention and are not intended to limit the present invention.

[0041] Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. Those skilled in the art should understand that these embodiments are merely illustrative of the technical principles of the present invention and are not intended to limit the scope of protection of the present invention.

[0042] It should be noted that in the description of this invention, the terms "upper", "lower", "left", "right", "inner", "outer", etc., which indicate directions or positional relationships, are based on the directions or positional relationships shown in the accompanying drawings. This is only for the convenience of description and is not intended to indicate or imply that the device or element must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, it should not be construed as a limitation of this invention.

[0043] Furthermore, it should be noted that, in the description of this invention, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "linking" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a mechanical connection or an electrical connection; they can refer to a direct connection or an indirect connection through an intermediate medium; and they can refer to the internal connection of two components. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0044] Please see Figures 1 to 3 As shown, the present invention provides a drilling process for machining tools cooled by liquid nitrogen, comprising:

[0045] Determine the initial cutting speed and initial feed rate based on the required hole machining depth and diameter of the target workpiece.

[0046] When the machining of a single target workpiece is completed, the tear reference value of the target workpiece is detected, and the machining adjustment method is determined based on the tear reference value. The machining adjustment method includes adjusting the cutting speed or adjusting the feed rate.

[0047] Periodically check the quality reference value for each batch of target processed parts, and determine whether to use the pre-drilling hole-making processing method based on the quality reference value;

[0048] In the pre-drilling hole-forming machining method, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch.

[0049] When both pre-drilling and single-drilling of a single target workpiece are completed, the residual thermal state of the target workpiece is detected to adjust the pre-drilling depth, or the burr distribution of the target workpiece is analyzed.

[0050] In the analysis of burr distribution, the liquid nitrogen flow rate corresponding to the area with frequent burrs is adjusted according to the preset burr distribution state, or the pre-drilling diameter is adjusted.

[0051] Specifically, the initial cutting speed and initial feed rate are determined based on the required hole machining depth and the required hole machining diameter of the target workpiece.

[0052] The initial cutting speed and the initial feed speed are negatively correlated with the required hole machining depth of the target workpiece.

[0053] The initial cutting speed and the initial feed rate are positively correlated with the required hole diameter of the target workpiece.

[0054] The drill bit described in this invention is an internally sprayed liquid nitrogen tool, which is connected to a liquid nitrogen supply device to cool the drill bit and the borehole during the working process.

[0055] Specifically, because a larger machining depth increases cutting resistance and heat accumulation, excessively high cutting speeds can lead to excessive heat buildup and accelerated tool wear. Therefore, for larger machining depths, the initial cutting speed should be relatively low. Larger machining depths require more cutting time, so a lower feed rate ensures the tool fully cuts the material, reducing the risk of overload and tool wear. For larger hole diameters, the tool needs to move a longer distance per unit time, so a higher cutting speed can improve machining efficiency. A higher feed rate can also improve machining efficiency. Given a maximum and minimum allowable cutting speed, as well as a maximum and minimum allowable feed rate, the cutting speed should be less than the maximum allowable cutting speed and greater than the minimum allowable cutting speed, and the feed rate should be less than the maximum feed rate and greater than the minimum allowable feed rate. The cutting speed is the rotational speed of the drill bit, and the feed rate is the displacement of the drill bit per unit time during operation.

[0056] Specifically, when the processing of a single target workpiece is completed, the tear reference value of the target workpiece is detected, and the processing adjustment method is determined based on the tear reference value;

[0057] If the tear reference value is within the first preset tear reference value range, the cutting speed will be reduced.

[0058] If the tear reference value is within the second preset tear reference value range, the feed rate will be reduced.

[0059] Specifically, the method for confirming the tear reference value is as follows: using a super depth-of-field three-dimensional microscope to detect the number of cracks at the inlet and outlet of the processed target part. The tear reference value is the total number of cracks at the inlet and outlet. Values ​​within the first preset tear reference value range are all greater than the preset tear reference value, and values ​​within the second preset tear reference value range are all less than or equal to the preset tear reference value. The user can set the preset tear reference value according to the preparation requirements. The higher the user's requirements for drilling quality, the smaller the preset tear reference value. One preset tear reference value is provided, with a value of 5. If the tear reference value = 0, there is no need to select the processing adjustment method.

[0060] Specifically, quality reference values ​​are periodically tested for each batch of target workpieces, and the pre-drilling hole-forming process is used based on the quality reference values.

[0061] If the quality reference value is within the first preset quality reference value range, pre-drilling is performed on the target workpiece to create a hole.

[0062] If the mass reference value is within the second preset mass reference value range, the liquid nitrogen flow rate will be increased.

[0063] Specifically, after each batch of target processed parts is completed by drilling, a quality reference value test is performed on the target processed parts of that batch. The number of workpieces in a single batch of target processed parts is 10.

[0064] Specifically, the formula for calculating the quality reference value is as follows:

[0065]

[0066] in, Ci is the number of drilling burrs in the i-th target workpiece, C0 is the average number of burrs, i = 1, 2, 3, ..., n, and n is the total number of target workpieces in a single batch.

[0067] Specifically, the values ​​within the first preset quality reference range are all greater than 3, and the values ​​within the second preset quality reference range are all less than or equal to 3 and greater than 0. If C0 = 0, then the drilling quality is qualified.

[0068] Specifically, in the pre-drilling hole-forming process, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch.

[0069] The initial pre-drilling depth and the initial number of pre-drilling operations are positively correlated with the quality reference value;

[0070] In the pre-drilling process, for a single target workpiece, a drill bit with a diameter half the required hole diameter is used to drill the workpiece. The number of drill passes is set to the initial pre-drilling pass. Each drill pass reaches the same depth. When the total drilling depth reaches the initial pre-drilling depth, a single-pass drilling operation is performed on the target workpiece using a drill bit of the required hole diameter. During this single-pass drilling operation, the centerline of the drill bit coincides with the centerline of the drill bit used in the pre-drilling process. The number of drill passes refers to the number of drill passes performed in the pre-drilling process for a single hole.

[0071] Specifically, the number of burrs can be detected by inputting images or videos of the drill hole into a computer and using image processing and analysis methods to detect and quantify the number of burrs in the drill hole. Any existing computer vision technology, image processing algorithm, and pattern recognition method can be used for automatic detection and counting of burrs, which is understandable to those skilled in the art and will not be elaborated here.

[0072] Specifically, the residual thermal state of the target workpiece is detected during both pre-drilling and single-drilling operations on a single workpiece.

[0073] If the residual heat state is in the first preset residual heat state, the pre-drilling depth is increased.

[0074] If the residual heat state is in the second preset residual heat state, the burr distribution state of the target workpiece is analyzed.

[0075] Specifically, by using an infrared thermal imaging camera to scan the hole area, temperature anomalies caused by residual heat can be detected. The maximum detected temperature is recorded as the residual heat of the corresponding target workpiece. If the residual heat is greater than the preset residual heat, the residual heat state is determined to be in the first preset residual heat state. If the residual heat is less than the preset residual heat, the residual heat state is determined to be in the second preset residual heat state. The preset residual heat is 180℃.

[0076] Specifically, the burr distribution of target parts processed by the pre-drilling hole-forming method in a single batch is periodically analyzed.

[0077] If the burr distribution is in the first preset burr distribution state, the liquid nitrogen flow rate corresponding to the burr frequent area is increased and adjusted.

[0078] If the burr distribution is in the second preset burr distribution state, adjust the pre-drilling diameter.

[0079] Specifically, the target workpiece processed by the pre-drilling hole-forming method is the workpiece whose total drilling depth reaches the initial pre-drilling depth and is completed by a single drilling operation using a drill bit with the required hole diameter. The burr height can be detected by, but is not limited to, a line laser displacement sensor. The burr height refers to the vertical height of the burr inside the hole relative to the reference surface, which is the tangent at the connection point between the burr and the hole.

[0080] Specifically, the first preset burr distribution state is that the proportion of the maximum height burrs in a drilling area is greater than the preset proportion. The liquid nitrogen flow rate is increased for the areas with frequent burrs, and the increase in liquid nitrogen flow rate is positively correlated with the proportion of the maximum height burrs.

[0081] Specifically, the inner surface of the borehole is divided into three drilling zones from the direction of the drill bit entry. Each drilling zone has the same inner surface area. The drilling zone with the percentage of the maximum height burrs exceeding a preset percentage is designated as a burr-frequent zone. The liquid nitrogen flow rate of the burr-frequent zone during a single drilling process is increased and adjusted. The preset percentage is 60%. The percentage of the maximum height burrs is determined by detecting the area where the maximum height burrs are located for each target workpiece. The percentage of the maximum height burrs = the number of maximum height burrs in a single drilling zone / the total number of target workpieces processed by the pre-drilling method in a single batch.

[0082] Specifically, the second preset burr distribution state is that the proportion of the maximum height burrs corresponding to the non-drilling area is greater than the preset proportion, and the pre-drilling diameter is increased accordingly.

[0083] The increase in pre-drilling diameter is positively correlated with the maximum burr height corresponding to the maximum height burr.

[0084] The technical solution of the present invention has been described above with reference to the preferred embodiments shown in the accompanying drawings. However, it will be readily understood by those skilled in the art that the scope of protection of the present invention is obviously not limited to these specific embodiments. Without departing from the principles of the present invention, those skilled in the art can make equivalent changes or substitutions to the relevant technical features, and the technical solutions after these changes or substitutions will all fall within the scope of protection of the present invention.

[0085] The above description is merely a preferred embodiment of the present invention and is not intended to limit the invention. Various modifications and variations can be made to the present invention by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

Claims

1. A drilling process for machining tools cooled by liquid nitrogen, characterized in that, Determine the initial cutting speed and initial feed rate based on the required hole machining depth and diameter of the target workpiece. The initial cutting speed and the initial feed speed are negatively correlated with the required hole machining depth of the target workpiece. The initial cutting speed and the initial feed rate are positively correlated with the required hole diameter of the target workpiece. When the machining of a single target workpiece is completed, the tear reference value of the target workpiece is detected, and the machining adjustment method is determined based on the tear reference value. The machining adjustment method includes adjusting the cutting speed or adjusting the feed rate. If the tear reference value is within the first preset tear reference value range, the cutting speed will be reduced. If the tear reference value is within the range of the second preset tear reference value, the feed rate will be reduced. Periodically check the quality reference value for each batch of target processed parts, and determine whether to use the pre-drilling hole-making processing method based on the quality reference value; If the quality reference value is within the first preset quality reference value range, pre-drilling is performed on the target workpiece to create a hole. If the mass reference value is within the second preset mass reference value range, adjust the liquid nitrogen flow rate; In the pre-drilling hole-forming machining method, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch. When both pre-drilling and single-drilling of a single target workpiece are completed, the residual thermal state of the target workpiece is detected to adjust the pre-drilling depth, or the burr distribution of the target workpiece is analyzed. In the analysis of burr distribution, the liquid nitrogen flow rate corresponding to the area with frequent burrs is adjusted according to the preset burr distribution state, or the pre-drilling diameter is adjusted.

2. The drilling process for liquid nitrogen-cooled machining tools according to claim 1, characterized in that, The formula for calculating the quality reference value is: in, Ci is the number of drilling burrs in the i-th target workpiece, C0 is the average number of burrs, i = 1, 2, 3, ..., n, and n is the total number of target workpieces in a single batch.

3. The drilling process for liquid nitrogen-cooled machining tools according to claim 2, characterized in that, In the pre-drilling hole-forming machining method, the initial pre-drilling depth and the initial number of pre-drilling operations are determined based on the quality reference value of the target workpiece in a single batch. The initial pre-drilling depth and the initial number of pre-drilling operations are positively correlated with the quality reference value; In the pre-drilling process, for a single target workpiece, a drill bit with a diameter half the required hole diameter is used to drill the target workpiece. The number of drilling operations is set to the initial pre-drilling operations. The depth of each drilling operation is the same. When the total drilling depth reaches the initial pre-drilling depth, a drill bit with the required hole diameter is used to drill a hole in the target workpiece in a single operation. During the single drilling operation, the center axis of the drill bit coincides with the center axis of the drill bit in the pre-drilling process.

4. The drilling process for liquid nitrogen-cooled machining tools according to claim 3, characterized in that, For each target workpiece, the residual thermal state is detected during pre-drilling and single-drilling operations. If the residual heat state is in the first preset residual heat state, the pre-drilling depth is increased. If the residual heat state is in the second preset residual heat state, the burr distribution state of the target workpiece is analyzed.

5. The drilling process for liquid nitrogen-cooled machining tools according to claim 4, characterized in that, Periodically analyze the burr distribution of target parts processed by the pre-drilling hole-forming method in a single batch. If the burr distribution is in the first preset burr distribution state, the liquid nitrogen flow rate corresponding to the burr frequent area is increased and adjusted. If the burr distribution is in the second preset burr distribution state, adjust the pre-drilling diameter.

6. The drilling process for liquid nitrogen-cooled machining tools according to claim 5, characterized in that, The first preset burr distribution state is that there is a drilling area where the proportion of the maximum height burrs is greater than the preset proportion. The liquid nitrogen flow rate is increased for the areas with frequent burrs, and the increase in liquid nitrogen flow rate is positively correlated with the proportion of the maximum height burrs.

7. The drilling process for liquid nitrogen-cooled machining tools according to claim 6, characterized in that, The second preset burr distribution state is that the percentage of the maximum height burrs in the non-drilling area is greater than the preset percentage, and the pre-drilling diameter is increased accordingly. The increase in pre-drilling diameter is positively correlated with the maximum burr height corresponding to the maximum height burr.

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