Head-step deep and long hole semi-fine boring machining method capable of reducing straightness error

Abstract

The invention relates to the technical field of machining metal cutting, in particular to a butt step deep and long hole semi-fine boring machining method capable of reducing straightness errors. Comprising the steps that the feeding speed, the rotating speed, the cutting direction, the vibration displacement, the deformation angle and the total radial cutting force of a boring rod at all moments, the follow rest moving speed, the cutting fluid flow, the cutting fluid temperature and the environment temperature are obtained; through the feeding speed, the rotating speed, the cutting direction, the vibration displacement, the deformation angle, the total radial cutting force and the follow rest moving speed of a boring rod, the initial supporting demand index of each cutting component force at each moment is obtained, and the dynamic follow-up response coefficient of the follow rest at each moment is obtained in combination with the cutting fluid flow, the cutting fluid temperature and the environment temperature and used for regulating and controlling the follow rest. According to the method, the follow rest is regulated and controlled by analyzing multi-dimensional data in machining, so that the attitude fluctuation of the boring rod is inhibited, and the straightness error in the semi-fine boring machining process of the deep and long hole is effectively reduced.

Description

Technical Field

[0001] This invention relates to the field of metal cutting technology in machining, and specifically to a semi-finish boring method for deep, elongated holes with mating steps to reduce straightness errors. Background Technology

[0002] Straightness error is a key shape tolerance in machining geometry, directly affecting the assembly accuracy and service life of precision parts. In actual machining, to achieve high-precision hole diameter dressing, long overhanging boring bars are usually used to perform semi-finish boring. Due to the large machining depth, the boring bar needs to have a long overhang length. However, due to the rigidity of the slender rod, the boring bar is easily affected by radial cutting force, friction, and cutting chatter during the cutting process, resulting in bending deformation. This leads to the offset of the hole axis after machining, thus producing straightness error.

[0003] Existing methods for reducing straightness mainly utilize a movable follow post installed next to the machine tool spindle. When the boring bar is fed, the follow post moves synchronously with the boring bar to reduce straightness error. However, the existing control methods for movable follow posts mostly rely on manual experience settings or simple feedback adjustments based on a single parameter. It is difficult to maintain stable synchronization between its movement speed and the boring bar feed speed, which can easily lead to lag or advance. This causes the support force to fluctuate at different machining stages, making it difficult to effectively reduce straightness error. Summary of the Invention

[0004] To address the problem that existing control methods for movable tool holders, which rely on manual experience or simple feedback adjustment based on a single parameter, are insufficient to effectively reduce straightness errors, this invention aims to provide a semi-finish boring method for deep, elongated holes with aligned steps to reduce straightness errors. The specific technical solution adopted is as follows: The feed rate, rotational speed, cutting direction, vibration displacement, deformation angle, total radial cutting force, follower travel speed, cutting fluid flow rate, cutting fluid temperature, and ambient temperature of the boring bar at each moment are obtained. Based on the difference between the feed rate of the lower boring bar and the travel rate of the follow post at each moment, the synchronization characteristics at each moment are obtained; based on the different cutting directions of the lower boring bar at each moment, the total radial cutting force at each moment is divided into several cutting components at each moment; the abnormal deviations of each cutting component at each moment and its corresponding vibration displacement and deformation angle in three dimensions are analyzed to obtain the degree of instability of each cutting component at each moment; based on the rotational speed, synchronization characteristics and degree of instability of the lower boring bar at each moment, the initial support demand index of each cutting component at each moment is obtained. Based on the cutting fluid flow rate, cutting fluid temperature, and ambient temperature at each time point, the risk index at each time point is obtained. The initial support demand index of each cutting force component at each time point is corrected, and the actual support demand index of each cutting force component at each time point is obtained. Combined with the synchronization characteristics at each time point, the dynamic tracking response coefficient of the tool holder at each time point is obtained.

[0005] Preferably, obtaining the synchronization features at each time point includes: The synchronization characteristics include synchronization rate and synchronization reliability factor; For any given moment, the time interval within a preset local time range is recorded as the local time interval of the given moment. The difference between the average feed rate of the boring bar and the average movement speed of the follow post at all moments within the local time interval of the given moment is analyzed. The difference is then negatively normalized, and the result of the negatively normalized difference is taken as the synchronization rate at the given moment. The synchronization reliability factor at the specified moment is obtained based on the difference between the synchronization rate at that moment and a preset standard synchronization rate sample set.

[0006] Preferably, the step of dividing the total radial cutting force at each moment into several cutting components based on the different cutting directions of the boring bar at each moment includes: At any given time, the cross-section of the boring bar is divided equally into a predetermined number of force component directions. For any force component direction, the angle between the force component direction and the cutting direction of the boring bar at that time is obtained. The total radial cutting force of the boring bar at that time is decomposed at the angle to obtain the cutting force component of the force component direction at that time.

[0007] Preferably, the acquisition of the instability degree of each cutting force component at each moment includes: For any cutting force at any time, the vibration reference weight corresponding to the cutting force at any time is obtained based on the difference between the vibration displacement corresponding to the cutting force at that time and the preset normal vibration displacement. Based on the difference between the deformation angle corresponding to the cutting force at the specified moment and the preset normal deformation angle, the deformation reference weight corresponding to the cutting force at the specified moment is obtained. Based on the cutting force components at each moment and their corresponding vibration displacement and deformation angle, the force load factor, vibration load factor and deformation load factor of each cutting force at each moment are obtained. Based on the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified time, the vibration load factor and deformation load factor of the cutting force at the specified time are weighted and summed to obtain the indirect instability factor of the cutting force at the specified time. The average of the force load factor and the indirect instability factor of the cutting force at the specified moment is taken as the degree of instability of the cutting force at the specified moment.

[0008] Preferably, the step of obtaining the force load factor, vibration load factor, and deformation load factor of each cutting component force at each moment based on each cutting component force at each moment and its corresponding vibration displacement and deformation angle includes: For any cutting force at any time, the ratio between the amplitude of the cutting force at that time and the preset boring bar cutting force limit is used as the force load factor of the cutting force at that time. The ratio between the vibration displacement corresponding to the cutting force at the specified moment and the preset limit value of the boring bar vibration displacement is used as the vibration load factor of the cutting force at the specified moment. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset limit value of the boring bar deformation angle is used as the deformation load factor of the cutting force at the specified moment.

[0009] Preferably, obtaining the vibration reference weight and its deformation reference weight corresponding to the cutting force at the specified moment includes: The ratio between the vibration displacement corresponding to the cutting force at the specified moment and the preset normal vibration displacement is used as the vibration reference factor corresponding to the cutting force at the specified moment. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset normal deformation angle is used as the deformation reference factor corresponding to the cutting force at the specified moment. The sum of the vibration reference factor and the deformation reference factor corresponding to the cutting force at the specified moment is denoted as the total reference factor of the cutting force at the specified moment. The proportions of the vibration reference factor and deformation reference factor corresponding to the cutting force at the specified moment in its total reference factors are used as the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified moment.

[0010] Preferably, the initial support requirement index for obtaining each cutting force component at each moment includes: For any cutting force at any time, the rotational speed of the boring bar at that time is normalized to obtain the rotational speed impact factor at that time; the synchronization rate at that time is negatively normalized to obtain the misalignment impact factor at that time. The synchronization reliability factor at the specified time is positively correlated and normalized to obtain the misalignment weight at the specified time; the synchronization reliability factor is negatively correlated and normalized to obtain the rotational speed weight at the specified time. Based on the misalignment weight and rotational speed weight at the specified time, the misalignment impact factor and rotational speed impact factor at the specified time are weighted and summed to obtain the impact index of the cutting force at the specified time. The product of the impact index of the cutting force at the specified moment and the degree of instability is normalized, and the normalized result is used as the initial support demand index of the cutting force at the specified moment.

[0011] Preferably, for any given time, the risk index at that time is negatively correlated with the cutting fluid flow rate at that time, and the risk index at that time is positively correlated with the cutting fluid temperature and the ambient temperature at that time.

[0012] Preferably, the actual support demand index for obtaining each cutting force component at each moment includes: For any cutting force at any time, the product of the initial support demand index of the cutting force at that time and the normalized risk index at that time is taken as the actual support demand index of the cutting force at that time.

[0013] Preferably, obtaining the dynamic tracking response coefficient of the tool holder at each moment includes: For any given moment, the average of the actual support demand index of all cutting forces at that moment is taken as the support demand intensity at that moment. Based on the support demand intensity and synchronization rate at that moment, the dynamic follow-up response coefficient of the tool holder at that moment is obtained.

[0014] This invention offers the following advantages: By acquiring the feed rate, rotational speed, cutting direction, vibration displacement, deformation angle, and total radial cutting force of the boring bar at various times, and simultaneously acquiring the follower head's traverse speed, cutting fluid flow rate, cutting fluid temperature, and ambient temperature, this invention provides a comprehensive quantitative characterization of the boring bar's motion state, stress state, and machining environment during the semi-finish boring of deep and long holes. Based on this, the synchronization rate is obtained by comparing the difference between the boring bar's feed rate and the follower head's traverse speed, and a synchronization reliability factor is further obtained, ensuring that the evaluation of the follower head's motion state considers both instantaneous consistency and state stability. Simultaneously, the total radial cutting force is decomposed into several cutting components according to the boring bar's cutting direction, and by combining the vibration displacement and deformation angle corresponding to each cutting component, the stress load factor, vibration load factor, and deformation load factor are obtained, thereby determining the degree of instability of each cutting component. This allows for directional and quantitative analysis of boring bar stability changes. Furthermore, by combining the boring bar speed, synchronization rate, and synchronization reliability factor, the initial support demand index for each cutting force is obtained, enabling the follower post support demand to simultaneously reflect the combined effects of cutting impact and follower deviation. In addition, by obtaining a risk index based on cutting fluid flow rate, cutting fluid temperature, and ambient temperature, and correcting the initial support demand index, the actual support demand index for each cutting force is obtained, allowing the support demand assessment to adapt to changes in the machining environment. Finally, by combining the actual support demand index and synchronization rate at the same moment, the dynamic follower post response coefficient is obtained, enabling the follower post to adaptively adjust according to the boring bar stability state and follower consistency at different machining stages. This ensures follower stability while suppressing boring bar attitude fluctuations, effectively reducing straightness errors during deep and long hole semi-finish boring. Attached Figure Description

[0015] To more clearly illustrate the technical solutions and advantages in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0016] Figure 1 A semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, provided as an embodiment of the present invention; Detailed Implementation To further illustrate the technical means and effects adopted by the present invention to achieve its intended purpose, the following, in conjunction with the accompanying drawings and preferred embodiments, details the specific implementation, structure, features, and effects of a semi-finish boring method for reducing straightness error in deep, elongated holes with opposing steps proposed according to the present invention. In the following description, different "one embodiment" or "another embodiment" do not necessarily refer to the same embodiment. Furthermore, specific features, structures, or characteristics in one or more embodiments can be combined in any suitable form.

[0017] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this invention pertains.

[0018] The following describes in detail, with reference to the accompanying drawings, a specific scheme for a semi-finish boring method for reducing straightness error in deep, long, stepped holes provided by the present invention.

[0019] Please see Figure 1 The diagram illustrates a flowchart of a semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, according to an embodiment of the present invention. The method includes: Step S101: Obtain the feed rate, rotational speed, cutting direction, vibration displacement, deformation angle, total radial cutting force, follower travel speed, cutting fluid flow rate, cutting fluid temperature, and ambient temperature of the boring bar at each time point.

[0020] It should be noted that in the semi-finish boring process of deep long holes with a head-mounted step, the straightness error of the hole axis is due to the deflection and offset generated by the boring bar during the cutting process and their cumulative effect over time. It is closely related to the motion state, stress state and machining environment conditions of the boring bar. Therefore, this embodiment collects and analyzes the feed rate, rotational speed, cutting direction, vibration displacement, deformation angle and total radial cutting force of the boring bar at various times, as well as the moving speed of the follow post, cutting fluid flow rate, cutting fluid temperature and ambient temperature, to analyze the stability of the boring bar posture during the machining process, thereby reducing the straightness error in the semi-finish boring process of deep long holes.

[0021] It should be further explained that the feed rate, rotational speed, and cutting direction of the boring bar reflect the changes in its motion conditions at different machining stages. The total radial cutting force reflects the radial load level borne by the boring bar during the cutting process. Vibration displacement and deformation angle are used to represent the dynamic offset and deflection trend of the boring bar under radial load. By analyzing the collected data, the timing and extent of the boring bar's attitude deviation during machining can be identified, thus providing a basis for reducing hole axis offset. At the same time, the travel speed of the follow post is used to characterize its follow-up state with the boring bar's feed process. The cutting fluid flow rate, cutting fluid temperature, and ambient temperature are used to reflect the changes in cooling and lubrication conditions and thermal environment during machining. Since changes in cutting fluid state and ambient temperature indirectly affect the frictional and thermal deformation characteristics during the cutting process, synchronously collecting the above parameters and conducting comprehensive analysis helps to judge the changes in the boring bar's stability under different working conditions, further reducing the straightness error in semi-finish boring of deep and long holes.

[0022] Specifically, in one implementation of this invention, the cutting direction of the boring bar at each moment is obtained. The feed rate of the boring bar at each moment is collected using a grating ruler installed on the machine tool feed system (this embodiment uses 1 second as an example). The rotational speed of the boring bar at each moment is collected using a speed sensor installed on the spindle. High-frequency vibration signals are collected using an acoustic emission sensor built into the machine tool spindle, and load torque fluctuations are collected using a spindle motor current sensor. Combining the boring bar overhang length and material modulus, the vibration displacement and deformation angle of the boring bar end are obtained based on a beam element model. The total radial cutting force of the boring bar at each moment is collected using a pressure sensor integrated on the boring bar head. The follower post moving speed at each moment is collected using an encoder installed on the follower post. The cutting fluid flow rate at each moment is collected using a flow sensor installed in the cutting fluid pipeline. The cutting fluid temperature and ambient temperature at each moment are collected using a temperature sensor installed in the cutting fluid pipeline and a temperature sensor installed in the machine tool's environment, respectively.

[0023] It should be noted that the tool holder integrates a micro actuator (such as a piezoelectric ceramic or hydraulic servo cylinder), which can provide micron-level radial / axial micro-compensation motion or dynamic support force on the basis of macroscopic synchronous feed, in order to actively suppress the vibration of the boring bar.

[0024] Step S102: Based on the difference between the feed rate of the lower boring bar and the moving speed of the follower post at each moment, obtain the synchronization characteristics at each moment; based on the different cutting directions of the lower boring bar at each moment, divide the total radial cutting force at each moment into several cutting components at each moment; analyze the abnormal deviations of each cutting component at each moment and its corresponding vibration displacement and deformation angle in three dimensions to obtain the degree of instability of each cutting component at each moment; based on the rotational speed, synchronization characteristics and degree of instability of the lower boring bar at each moment, obtain the initial support demand index of each cutting component at each moment.

[0025] It should be noted that during the semi-finish boring of deep and long holes, the attitude deviation of the boring bar during feeding and cutting is often related to the consistency of the boring bar's movement and the force distribution in different directions. Therefore, this embodiment analyzes the difference between the feed speed of the boring bar and the moving speed of the follower at each moment to obtain the synchronization characteristics at each moment. This is used to characterize the degree of follower stability of the follower on the boring bar during the machining process, thereby avoiding insufficient or excessive local support caused by the follower's lag or advance. The total radial force is decomposed into several components to identify the dynamic stiffness differences of the machine tool spindle and guide rail at different angles (such as weaker stiffness in the direction of the guide rail mating surface), thereby applying stronger auxiliary support in the direction of weak stiffness.

[0026] In the semi-finish boring process of deep long holes with a head-mounted step, the radial load borne by the boring bar under cutting action has obvious directional characteristics in space. The difference in radial force in different directions will have different effects on the deflection direction and degree of the boring bar, thus affecting the spatial offset trend of the hole axis. Therefore, this embodiment divides the total radial cutting force at each moment into several cutting components, so that the amplitude of each cutting component can reflect its relative contribution to the radial deflection of the boring bar under the current cutting direction. This accurately quantifies the difference in the influence of radial load in different directions on the deflection trend of the boring bar, and provides a basis for subsequent identification of the key force directions that are prone to causing the boring bar attitude offset. This helps to suppress the cumulative effect of the boring bar attitude offset during the machining process and reduce the straightness error in the semi-finish boring of deep long holes.

[0027] It should be further explained that, for each cutting force component, by combining the vibration displacement and deformation angle corresponding to each cutting force component, the force load factor, vibration load factor, and deformation load factor are obtained respectively. These are used to characterize the local load state of the boring bar from two aspects: force amplitude and dynamic response. Based on this, the degree of instability of each cutting force component is obtained to identify boring bar deflection or offset that is prone to occur during machining. Furthermore, by combining the boring bar rotation speed and corresponding synchronization characteristics at each moment, the instability state of different cutting forces is comprehensively evaluated, thereby obtaining the initial support demand index of each cutting force component at each moment. This allows the subsequent support strategy to be adjusted for the stability differences in different directions and at different times, which helps to suppress the cumulative effect of boring bar attitude offset, thereby reducing the straightness error in the semi-finish boring of deep and long holes.

[0028] Step S103: Based on the cutting fluid flow rate, cutting fluid temperature and ambient temperature at each time, obtain the risk index at each time, correct the initial support demand index of each cutting force at each time, obtain the actual support demand index of each cutting force at each time, and combine the synchronization characteristics at each time to obtain the dynamic follow-up response coefficient of the tool holder at each time.

[0029] It should be noted that during the semi-finish boring of deep and long holes, the stability of the boring bar is not only affected by its motion and stress state, but also indirectly affected by changes in the machining environment, especially changes in the cutting fluid state and ambient temperature. These changes can easily cause fluctuations in cutting friction and thermal deformation characteristics, thus affecting the actual load state and attitude stability of the boring bar. Therefore, this embodiment obtains corresponding risk indices based on the cutting fluid flow rate, cutting fluid temperature, and ambient temperature at each moment to characterize the degree of influence of potential unstable factors under different machining environment conditions. Thus, the initial support requirements of each cutting component force at each moment are determined by the risk index. The index is corrected so that the assessment results of support requirements can reflect the stability changes in the actual processing environment, avoiding the judgment of support requirements based solely on ideal or constant working conditions, thereby improving the adaptability and reliability of support requirements assessment. Furthermore, the dynamic following response coefficient of the follower post is obtained by combining the synchronization rate at each moment, so that the following strategy of the follower post can simultaneously consider the changes in the processing environment and its follow-up consistency with the boring bar feed process. This allows for reasonable adjustment of the following behavior of the follower post under different working conditions, which helps to suppress the cumulative effect of boring bar attitude deviation during processing, thereby reducing the straightness error in semi-finish boring of deep and long holes.

[0030] Furthermore, in some implementations of the embodiments of the present invention, the method for obtaining synchronization features at each time point includes: The specific value of the local time period range can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, the local time range is set to 3 seconds as an example. For any time, the time period in the local time range before the time is recorded as the local time period of the time. The average feed rate of the boring bar and the average movement speed of the follower post at all times in the local time period of the time are respectively used as the reference feed rate of the boring bar and the reference movement speed of the follower post at the time. The difference between the reference feed rate of the boring bar and the reference movement speed of the follower post at the time is negatively correlated and normalized. The result of the negative correlation normalization is used as the synchronization rate at the time.

[0031] In one specific implementation of this invention, the method for negative correlation normalization is as follows: 1 is subtracted from the relative percentage difference between the reference feed rate of the boring bar and the reference movement rate of the follower at the given time. Since the relative percentage difference is a well-known prior art, it will not be elaborated upon in this embodiment. The smaller the difference between the reference feed rate of the boring bar and the reference movement rate of the follower, the closer the reference feed rate of the boring bar is to the reference movement rate of the follower, meaning the higher the response matching level of the follower to the boring bar feed behavior within a local time range. Therefore, negative correlation normalization is performed on the difference between the reference feed rate of the boring bar and the reference movement rate of the follower.

[0032] The synchronization reliability factor at the specified moment is obtained based on the difference between the synchronization rate at that moment and a preset standard synchronization rate sample set.

[0033] It should be noted that the synchronization rate at any given moment represents the response matching level of the follower post to the boring bar feed behavior within a local time range. The lower the synchronization rate, the greater the speed deviation between the boring bar and the follower post, which is prone to insufficient or excessive support in local machining stages, thereby increasing the risk of boring bar attitude deviation. The synchronization reliability factor represents the reliability of the synchronization rate relative to the synchronization characteristics under stable machining conditions. That is, if the synchronization rate value is high at a certain moment, but the synchronization state deviates significantly from the preset standard synchronization rate sample set, it may still belong to an occasional or unstable follow-up situation. By simultaneously acquiring the synchronization rate and synchronization reliability factor at each moment, the cooperative state between the follower post and the boring bar can be quantitatively described from two aspects: follow-up consistency level and synchronization state reliability. This helps to accurately identify stable and abnormal follow-up conditions during machining, providing a more reliable synchronization basis for subsequent support requirement assessment and follower post response control, thereby suppressing the cumulative effect of boring bar attitude deviation and reducing straightness error in deep and long hole semi-finish boring.

[0034] It should be noted that, in a specific implementation of this invention, the method for obtaining the preset standard synchronization rate sample set is as follows: a historical range is preset, and the specific value of the historical range can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, the historical range is set to 7 days as an example. The synchronization rate of all moments in the most recent historical range is obtained and recorded as the standard synchronization rate sample set. Furthermore, the standard deviation between the synchronization rate at the stated time and the preset standard synchronization rate sample set is normalized by a maximum and minimum value (the maximum and minimum values ​​can be obtained from historical experiments or prior experience, and the maximum and minimum values ​​can be adjusted, calibrated or optimized, which does not constitute a limitation of the present invention), and the result obtained by subtracting the normalization from 1 is used as the synchronization reliability factor at the stated time. Since the standard deviation is a well-known prior art, it will not be described in detail in this embodiment.

[0035] Furthermore, in some implementations of the present invention, the step of dividing the total radial cutting force at each moment into several cutting components at each moment according to the different cutting directions of the boring bar at each moment includes: For any given moment, a preset number of force components is used. The specific value of the number of force components can be set according to the actual situation. This embodiment does not impose a rigid requirement. In this embodiment, the number of force components is set to 8 as an example. The cross-section of the boring bar is equally divided into the preset number of force component directions. For any force component direction, the angle between the force component direction and the cutting direction of the boring bar at the given moment is obtained. The total radial cutting force of the boring bar at the given moment is decomposed at the included angle to obtain the cutting force component of the force component direction at the given moment. As an example, the specific calculation formula for obtaining the cutting component force in the direction of the component force at the specified moment is as follows: In the formula, The cutting component force represents the direction of the component force at the specified moment; This represents the total radial cutting force of the boring bar at the stated moment; This represents the function that takes the maximum value. The cosine of the angle between the direction of the force component and the cutting direction of the boring bar at the specified moment is given.

[0036] Furthermore, in some implementations of this invention, obtaining the degree of instability of each cutting force component at each moment includes: For any cutting force at any time, the ratio between the amplitude of the cutting force at that time and the preset boring bar cutting force limit is used as the force load factor of the cutting force at that time. The ratio between the vibration displacement corresponding to the cutting force at the specified moment and the preset limit value of the boring bar vibration displacement is used as the vibration load factor of the cutting force at the specified moment. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset limit value of the boring bar deformation angle is used as the deformation load factor of the cutting force at the specified moment.

[0037] It should be noted that the specific values ​​of the preset boring bar cutting force limit, boring bar vibration displacement limit, and boring bar deformation angle limit can be set according to the actual situation. This embodiment does not make a rigid requirement. In this embodiment, the boring bar cutting force limit is set to 1000 Newtons, the boring bar vibration displacement limit is set to 0.05 mm, and the boring bar deformation angle limit is set to 0.03 degrees as an example. The preset boring bar cutting force limit, boring bar vibration displacement limit, and boring bar deformation angle limit represent the upper limit of the cutting force, the upper limit of the vibration displacement, and the upper limit of the deformation angle that the boring bar can withstand, respectively.

[0038] It should be further explained that during the semi-finish boring of deep, elongated holes with a head-mounted step, the attitude deviation of the boring bar under cutting action is usually not caused by a single factor, but is the result of the combined effects of multiple factors such as radial force level, dynamic vibration state, and degree of deflection. Therefore, this embodiment introduces a force load factor, vibration load factor, and deformation load factor for any cutting force at each moment to quantify the influence of the cutting force on the stability of the boring bar under the current working condition from different dimensions. Among them, the force load factor reflects the force in that direction by comparing the amplitude of the cutting force with the preset boring bar cutting force limit. The horizontal level is close to the safe or stable working range; the vibration load factor is used to characterize the dynamic response intensity of the boring bar under the force direction by comparing the corresponding vibration displacement with the preset vibration displacement limit; the deformation load factor is used to characterize the severity of the boring bar deflection under the force direction by comparing the corresponding deformation angle with the preset deformation angle limit. In this way, the local stability of the boring bar is comprehensively evaluated under different force directions and at different times, which provides a basis for subsequent identification of the degree of instability corresponding to the cutting force, helps to suppress the cumulative effect of the boring bar attitude deviation, and reduces the straightness error in the semi-finish boring of deep and long holes.

[0039] In some implementations of the present invention, for any cutting force at any time, the ratio between the vibration displacement corresponding to the cutting force at that time and the preset normal vibration displacement is used as the vibration reference factor corresponding to the cutting force at that time. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset normal deformation angle is used as the deformation reference factor corresponding to the cutting force at the specified moment. It should be noted that the specific method for obtaining the preset normal vibration displacement and the preset normal deformation angle is as follows: the average vibration displacement of all moments in the most recent historical range is taken as the preset normal vibration displacement; the average deformation angle of all moments in the most recent historical range is taken as the preset normal deformation angle.

[0040] Furthermore, based on the vibration reference factor and deformation reference factor corresponding to the cutting force at the specified time, the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified time are obtained respectively. The specific method is as follows: The sum of the vibration reference factor and the deformation reference factor corresponding to the cutting force at the specified moment is denoted as the total reference factor of the cutting force at the specified moment. The proportions of the vibration reference factor and deformation reference factor corresponding to the cutting force at the specified moment in its total reference factors are used as the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified moment.

[0041] Furthermore, based on the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified moment, the vibration load factor and deformation load factor of the cutting force at the specified moment are weighted and summed to obtain the indirect instability factor of the cutting force at the specified moment. The average of the force load factor and the indirect instability factor of the cutting force at the specified moment is taken as the degree of instability of the cutting force at the specified moment.

[0042] It should be noted that during the semi-finish boring of deep and long holes, the instability of the boring bar is closely related to the dynamic vibration response generated during the cutting process and the resulting flexural deformation. Different cutting forces under the same stress level may cause significant differences in vibration displacement and deformation angle. Therefore, this embodiment introduces vibration reference factors and deformation reference factors to quantify the degree of change of the vibration displacement and deformation angle corresponding to the current cutting force relative to the normal reference state, thereby reflecting the potential trend of dynamic instability caused by the cutting force under the current working condition. By converting the proportional relationship between vibration reference factors and deformation reference factors into corresponding reference weights, the influence weights of vibration response and deformation state in instability assessment can be automatically adjusted according to their relative significance, avoiding the insufficient adaptability problem caused by using fixed weights for both. Furthermore, by weighting and fusing vibration load factors and deformation load factors with vibration reference weights and deformation reference weights, an indirect instability factor is obtained, which can represent the instability tendency of cutting force at the dynamic response level. At the same time, the indirect instability factor is fused with the load factor to obtain the degree of instability of cutting force, so that the instability assessment results can simultaneously take into account the stress level and dynamic response characteristics, thereby more accurately reflecting the comprehensive influence of cutting force on the attitude stability of boring bar under different directions and working conditions. This helps to identify and suppress instability conditions that are prone to attitude deviation during machining, and reduce straightness errors in semi-finish boring of deep and long holes.

[0043] Furthermore, in some implementations of this invention, for any cutting force at any time, the rotational speed of the boring bar at that time is normalized (the specific normalization process is: the ratio of the rotational speed of the boring bar at that time to the highest rotational speed of the boring bar), and the result of the normalization is used as the rotational speed impact factor at that time; the synchronization rate at that time is negatively normalized (the specific normalization process is: 1 minus the synchronization rate at that time), and the result of the negative correlation normalization is used as the misalignment impact factor at that time. The synchronization reliability factor at the specified time is positively correlated and normalized to obtain the misalignment weight at the specified time; the synchronization reliability factor is negatively correlated and normalized to obtain the rotational speed weight at the specified time.

[0044] It should be noted that, since the range of the synchronization reliability factor at the specified time is 0 to 1, this embodiment uses the synchronization reliability factor at the specified time as the misalignment weight at the specified time, and uses the difference obtained by subtracting the synchronization reliability factor at the specified time from 1 as the rotation speed weight at the specified time.

[0045] Based on the misalignment weight and rotational speed weight at the specified time, the misalignment impact factor and rotational speed impact factor at the specified time are weighted and summed to obtain the impact index of the cutting force at the specified time. The product of the impact index of the cutting force component at the specified moment and the degree of instability is normalized to a maximum and minimum value (the maximum and minimum values ​​can be obtained from historical experiments or prior experience, and the maximum and minimum values ​​can be adjusted, calibrated or optimized, which does not constitute a limitation of the present invention). The normalized result is used as the initial support demand index of the cutting force component at the specified moment.

[0046] It should be noted that during the semi-finish boring of deep and long holes, the required support strength of the boring bar under different machining conditions is not only related to its instantaneous instability, but also affected by the machining rhythm and the follow-up matching state. Therefore, this embodiment obtains a speed impact factor by normalizing the boring bar speed to characterize the degree of proximity of the current machining rhythm to the extreme working condition, and obtains a misalignment impact factor by negatively normalizing the synchronization rate to reflect the potential impact of the inconsistency between the follow-up of the tool holder and the boring bar stability, thereby comprehensively evaluating the impact impact under different working conditions; at the same time, it obtains a misalignment impact factor by ensuring synchronization reliability. The factors dynamically allocate the weights of the misalignment impact factor and the rotational speed impact factor, enabling the impact assessment results to automatically adjust their emphasis based on the reliability of the current synchronization state: when the follow-up consistency is relatively reliable, the rotational speed factor occupies a larger proportion in the impact assessment; when the follow-up consistency is poor, the influence of the misalignment factor is strengthened accordingly, thereby improving the adaptability of the impact assessment; furthermore, by obtaining the initial support demand index from the impact index and the degree of instability of the cutting force component, the assessment results of the support demand can simultaneously reflect the instability risk of the cutting force component itself as well as the additional impact effects brought about by the processing rhythm and the follow-up state.

[0047] Thus, the initial support demand index for each cutting force component at each moment is obtained.

[0048] In some implementations of the present invention, for any given time, a risk index is obtained based on the cutting fluid flow rate, cutting fluid temperature, and ambient temperature at that time. The risk index at that time is negatively correlated with the cutting fluid flow rate at that time, and positively correlated with the cutting fluid temperature and ambient temperature at that time.

[0049] As an example, the method for obtaining the risk index at the stated time is as follows: In the formula, This indicates the cutting fluid flow risk factor at the stated time. This indicates the cutting fluid temperature risk factor at the stated time. This indicates the environmental temperature risk factor at the stated time. This indicates the cutting fluid flow rate at the stated time. This indicates the temperature of the cutting fluid at the stated moment; This represents the function that takes the maximum value. This indicates the ambient temperature at the stated time. Indicates the preset rated cutting fluid flow rate; This indicates the preset standard cutting fluid temperature; This indicates the preset standard ambient temperature; , , The specific value can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, it is used as... Rise per minute Celsius Let's take Celsius as an example.

[0050] It should be noted that the preset rated cutting fluid flow rate represents the safe lower limit of the cutting fluid flow rate. When the cutting fluid flow rate is less than the preset rated cutting fluid flow rate, the increased cutting friction will affect the stability of the boring bar. When the cutting fluid flow rate is greater than the preset rated cutting fluid flow rate, the cutting friction will be at a safe level. Therefore, the range of the cutting fluid flow rate risk factor is constrained by taking the maximum value function. Similarly, the ranges of the ambient temperature risk factor and the cutting fluid temperature risk factor are constrained.

[0051] Furthermore, the average of the cutting fluid temperature risk factor and the ambient temperature risk factor at the specified time is taken as the temperature risk factor at the specified time; a flow rate risk weight and a temperature risk weight are preset, and the sum of the flow rate risk weight and the temperature risk weight is 1. The specific values ​​of the flow rate risk weight and the temperature risk weight can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, the flow rate risk weight is set to 0.6 and the temperature risk weight is set to 0.4 as an example for description. Based on the flow rate risk weight and temperature risk weight, the cutting fluid flow rate risk factor and temperature risk factor at the specified time are weighted and summed to obtain the risk index at the specified time.

[0052] It should be noted that during the semi-finish boring of deep and long holes, the machining environment affects the stability of the boring bar. In particular, insufficient cutting fluid flow or high cutting fluid temperature and ambient temperature can easily lead to a decrease in cooling and lubrication, thereby increasing cutting friction and causing thermal accumulation. This makes the boring bar more prone to posture fluctuations during cutting, resulting in increased straightness error. Therefore, this embodiment introduces cutting fluid flow risk factors, cutting fluid temperature risk factors, and ambient temperature risk factors to quantify the degree of deviation of the current machining environment from the stable machining state. This yields a risk index, which is used to quantify the stability changes under actual machining environment conditions. This allows subsequent support requirement assessments to anticipate adverse environmental conditions in advance, thereby suppressing their amplified impact on the boring bar's posture stability and reducing straightness error in the semi-finish boring of deep and long holes.

[0053] Furthermore, in some implementations of the present invention, for any cutting force at any time, the product of the initial support demand index of the cutting force at that time and the normalized risk index at that time is used as the actual support demand index of the cutting force at that time.

[0054] The average of the actual support demand index of all cutting force components at the specified moment is taken as the support demand intensity at the specified moment. Based on the support demand intensity and synchronization rate at the specified moment, the dynamic follow-up response coefficient of the tool holder at the specified moment is obtained.

[0055] It should be noted that, since the machining environment affects the stability of the boring bar, this embodiment obtains a risk index based on the cutting fluid flow rate, cutting fluid temperature, and ambient temperature. This risk index is used to correct the initial support requirement index of the cutting force, thereby obtaining the actual support requirement index of the cutting force. This index is used to quantify the support requirement of the cutting force during actual machining. By averaging the actual support requirement indices of all cutting forces at the same moment, the support requirement intensity of the boring bar under overall stable conditions at that moment can be characterized, and the abnormality of a single cutting force can be avoided from having an excessive impact on the follower control. Furthermore, the dynamic follower response coefficient of the follower is obtained by combining the synchronization rate at the aforementioned moment. This dynamic follower response coefficient increases accordingly when the support requirement is high and the synchronization state is good, thereby achieving adaptive adjustment of the follower follow amplitude and response intensity. This helps to maintain the stability of the boring bar posture and reduce straightness error under different machining conditions.

[0056] As an example, the specific formula for calculating the dynamic tracking response coefficient of the tool holder at the stated moment is as follows: In the formula, This represents the dynamic tracking response coefficient of the tool holder at the stated moment; Indicates the synchronization rate at the stated moment; This indicates the intensity of support demand at the stated moment; This represents a function that takes the minimum value. This indicates a preset response coefficient limit, the The specific value can be set according to the actual situation. This embodiment does not make a hard requirement. In this embodiment, it is used as... Taking this example, the purpose is to fine-tune the follow-up speed of the follower post to create a slight phase lead or lag relative to the boring bar, thereby forming a dynamic damping effect to suppress cutting chatter, rather than simply pursuing absolute synchronization of geometric position. The dynamic follow-up response coefficient of the follower post adopts... Constructed in the form of synchronization rate Used to characterize the synchronization state between the follow post and the boring bar, ensuring a stable follow-up relationship is maintained preferentially when the synchronization state is good; when the synchronization state deviates, it is controlled by... Introducing support for demand strength The dominant adjustment component allows the follow post to compensate and adjust the follow response according to the actual support requirements, thereby avoiding the adverse effects of relying solely on geometric synchronization or rigid control. This helps to suppress cutting chatter and maintain the stability of the boring bar posture under different machining conditions.

[0057] Thus, the dynamic tracking response coefficients of the tool holder at each moment are obtained.

[0058] It should be noted that after obtaining the dynamic tracking response coefficient of the tool holder at each moment, the tracking control amount of the tool holder is adjusted according to the dynamic tracking response coefficient of the tool holder at each moment, so that the actual tracking behavior of the tool holder matches the current stability state of the boring bar.

[0059] Specifically, for any given time, a dynamic response reference gain is preset. The specific value of the dynamic response reference gain can be set according to the actual situation. This embodiment does not impose a strict requirement. In this embodiment, the dynamic response reference gain is set to 0.03 mm / s as an example. The product of the dynamic follow-up response coefficient of the follower post at the given time and the dynamic response reference gain is used as the dynamic compensation feed speed at the given time. The dynamic compensation feed speed is superimposed on the follower post moving speed at the given time (the follower post moving speed at the given time is a conventional command speed obtained based on existing technology to keep the follower post and boring bar feeding synchronously) to obtain the follower post correction command speed at the given time. When the dynamic follow-up response coefficient is large, the follower post's follow-up response intensity is increased to enhance the support for the boring bar. When the dynamic follow-up response coefficient is small, the follower post's follow-up response intensity is reduced to avoid excessive support from adversely affecting machining stability.

[0060] It should be noted that by introducing the dynamic follow-up response coefficient of the tool holder, the follow-up process of the tool holder can be adaptively adjusted according to the stress state, stability changes, and synchronization state of the boring bar under different machining stages. This ensures follow-up stability while suppressing boring bar posture fluctuations, which helps to reduce straightness errors in the semi-finish boring process of deep and long holes. In this embodiment, a dynamic compensation feed rate determined by the dynamic follow-up response coefficient is superimposed on the conventional command speed, so that the tool holder can achieve micro-dynamic adjustment of support strength while maintaining macro-synchronous feed. At the same time, in order to avoid the denominator being zero during fractional calculations, this embodiment adds 0.01 to the denominator when the denominator is 0 during fractional calculations.

[0061] It should be further noted that the order of the above embodiments of the present invention is merely for descriptive purposes and does not represent the superiority or inferiority of the embodiments. The processes depicted in the accompanying drawings do not necessarily require a specific or sequential order to achieve the desired result. In some embodiments, multitasking and parallel processing are also possible or may be advantageous.

[0062] The various embodiments in this specification are described in a progressive manner. The same or similar parts between the various embodiments can be referred to each other. Each embodiment focuses on describing the differences from other embodiments.

Claims

1. A method for semi-finish boring of deep, elongated holes with mating steps to reduce straightness error, characterized in that, The method includes: The feed rate, rotational speed, cutting direction, vibration displacement, deformation angle, total radial cutting force, follower travel speed, cutting fluid flow rate, cutting fluid temperature, and ambient temperature of the boring bar at each moment are obtained. Based on the difference between the feed rate of the lower boring bar and the travel rate of the follow post at each moment, the synchronization characteristics at each moment are obtained; based on the different cutting directions of the lower boring bar at each moment, the total radial cutting force at each moment is divided into several cutting components at each moment; the abnormal deviations of each cutting component at each moment and its corresponding vibration displacement and deformation angle in three dimensions are analyzed to obtain the degree of instability of each cutting component at each moment; based on the rotational speed, synchronization characteristics and degree of instability of the lower boring bar at each moment, the initial support demand index of each cutting component at each moment is obtained. Based on the cutting fluid flow rate, cutting fluid temperature, and ambient temperature at each time point, the risk index at each time point is obtained. The initial support demand index of each cutting force component at each time point is corrected, and the actual support demand index of each cutting force component at each time point is obtained. Combined with the synchronization characteristics at each time point, the dynamic tracking response coefficient of the tool holder at each time point is obtained.

2. The semi-finish boring method for reducing straightness error in deep, elongated holes with mating steps according to claim 1, characterized in that, The acquisition of synchronization features at each time point includes: The synchronization characteristics include synchronization rate and synchronization reliability factor; For any given moment, the time interval within a preset local time range is recorded as the local time interval of the given moment. The difference between the average feed rate of the boring bar and the average movement speed of the follow post at all moments within the local time interval of the given moment is analyzed. The difference is then negatively normalized, and the result of the negatively normalized difference is taken as the synchronization rate at the given moment. The synchronization reliability factor at the specified moment is obtained based on the difference between the synchronization rate at that moment and a preset standard synchronization rate sample set.

3. The semi-finish boring method for reducing straightness error in deep, elongated holes with mating steps according to claim 1, characterized in that, The method of dividing the total radial cutting force at each moment into several cutting components based on the different cutting directions of the boring bar at each moment includes: At any given time, the cross-section of the boring bar is divided equally into a predetermined number of force component directions. For any force component direction, the angle between the force component direction and the cutting direction of the boring bar at that time is obtained. The total radial cutting force of the boring bar at that time is decomposed at the angle to obtain the cutting force component of the force component direction at that time.

4. The semi-finish boring method for reducing straightness error in deep, elongated holes with mating steps according to claim 1, characterized in that, The degree of instability of each cutting force component at each moment includes: For any cutting force at any time, the vibration reference weight corresponding to the cutting force at any time is obtained based on the difference between the vibration displacement corresponding to the cutting force at that time and the preset normal vibration displacement. Based on the difference between the deformation angle corresponding to the cutting force at the specified moment and the preset normal deformation angle, the deformation reference weight corresponding to the cutting force at the specified moment is obtained. Based on the cutting force components at each moment and their corresponding vibration displacement and deformation angle, the force load factor, vibration load factor and deformation load factor of each cutting force at each moment are obtained. Based on the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified time, the vibration load factor and deformation load factor of the cutting force at the specified time are weighted and summed to obtain the indirect instability factor of the cutting force at the specified time. The average of the force load factor and the indirect instability factor of the cutting force at the specified moment is taken as the degree of instability of the cutting force at the specified moment.

5. A semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, as described in claim 4, is characterized in that... The process of obtaining the force load factor, vibration load factor, and deformation load factor of each cutting component force at each moment based on each cutting component force at each moment and its corresponding vibration displacement and deformation angle includes: For any cutting force at any time, the ratio between the amplitude of the cutting force at that time and the preset boring bar cutting force limit is used as the force load factor of the cutting force at that time. The ratio between the vibration displacement corresponding to the cutting force at the specified moment and the preset limit value of the boring bar vibration displacement is used as the vibration load factor of the cutting force at the specified moment. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset limit value of the boring bar deformation angle is used as the deformation load factor of the cutting force at the specified moment.

6. A semi-finish boring method for reducing straightness error in deep, elongated holes with mating steps according to claim 5, characterized in that, The process of obtaining the vibration reference weight and its deformation reference weight corresponding to the cutting force at the specified moment includes: The ratio between the vibration displacement corresponding to the cutting force at the specified moment and the preset normal vibration displacement is used as the vibration reference factor corresponding to the cutting force at the specified moment. The ratio between the deformation angle corresponding to the cutting force at the specified moment and the preset normal deformation angle is used as the deformation reference factor corresponding to the cutting force at the specified moment. The sum of the vibration reference factor and the deformation reference factor corresponding to the cutting force at the specified moment is denoted as the total reference factor of the cutting force at the specified moment. The proportions of the vibration reference factor and deformation reference factor corresponding to the cutting force at the specified moment in its total reference factors are used as the vibration reference weight and deformation reference weight corresponding to the cutting force at the specified moment.

7. A semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, as described in claim 2, is characterized in that... The initial support requirement index for obtaining each cutting force component at each moment includes: For any cutting force at any time, the rotational speed of the boring bar at that time is normalized to obtain the rotational speed impact factor at that time; the synchronization rate at that time is negatively normalized to obtain the misalignment impact factor at that time. The synchronization reliability factor at the specified time is positively correlated and normalized to obtain the misalignment weight at the specified time; the synchronization reliability factor is negatively correlated and normalized to obtain the rotational speed weight at the specified time. Based on the misalignment weight and rotational speed weight at the specified time, the misalignment impact factor and rotational speed impact factor at the specified time are weighted and summed to obtain the impact index of the cutting force at the specified time. The product of the impact index of the cutting force at the specified moment and the degree of instability is normalized, and the normalized result is used as the initial support demand index of the cutting force at the specified moment.

8. A semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, as described in claim 1, is characterized in that... At any given time, the risk index at that time is negatively correlated with the cutting fluid flow rate at that time, and the risk index at that time is positively correlated with the cutting fluid temperature and the ambient temperature at that time.

9. A semi-finish boring method for reducing straightness error in deep, elongated holes with a mating step, as described in claim 8, is characterized in that... The actual support demand index for obtaining each cutting force component at each moment includes: For any cutting force at any time, the product of the initial support demand index of the cutting force at that time and the normalized risk index at that time is taken as the actual support demand index of the cutting force at that time.

10. A method for semi-finish boring of deep, elongated holes with opposing steps to reduce straightness error according to claim 2, characterized in that, The acquisition of the dynamic tracking response coefficient of the tool holder at each moment includes: For any given moment, the average of the actual support demand index of all cutting forces at that moment is taken as the support demand intensity at that moment. Based on the support demand intensity and synchronization rate at that moment, the dynamic follow-up response coefficient of the tool holder at that moment is obtained.

Images