Dynamic eccentricity compensation type inclined hole machining process for heavy workpieces

Abstract

The application discloses a dynamic eccentricity compensation type inclined hole machining process for heavy workpieces, which comprises the following steps: S1, workpiece clamping and posture calibration; S2, material touching interval machining; S3, half material entering interval machining; S4, drill completely drilling into switching process; S5, subsequent drilling processing. Different machining intervals are divided according to the real-time cutting depth of the drill, the cutting amount is only reduced in the drill material touching and half material entering stages, and corresponding compensation algorithms are configured, the lateral impact load is weakened from the cutting source, the feedforward fuzzy PID composite compensation and the adaptive torque vector decoupling compensation are matched for two different vibration conditions of instantaneous impact and continuous overturning deflection, the eccentric offset generated in different stages can be accurately offset, the spindle vibration and the inclined hole entrance eccentric error are greatly reduced, secondary defects such as hole wall vibration marks caused by sudden change of the compensation amount are avoided, and the controller algorithm loss and additional trajectory deviation caused by continuous compensation in the stable cutting stage are eliminated, so that the machining quality of the inclined hole is effectively guaranteed.

Description

Technical Field

[0001] The invention belongs to the technical field of drilling processing, and particularly relates to a dynamic eccentricity compensation inclined hole processing process for heavy-duty workpieces. Background Art

[0002] Large heavy-duty workpieces have large dimensions and weights, leading to extremely high costs for overturning and secondary clamping positioning. The industry generally adopts the method of tilting the spindle to directly process inclined assembly holes. When the tilted drill bit contacts the workpiece, cutting load is concentrated on one side during the material touching and semi-feeding stages, generating lateral cutting force and overturning moment, which causes processing defects such as tool bar deflection, spindle radial vibration, eccentricity at the inclined hole entrance, and vibration marks on the hole wall; after the drill bit completely drills into the workpiece, the cutting edge fits the workpiece in the entire area and is uniformly stressed, so vibration and eccentric deformation are greatly reduced.

[0003] All existing processing compensation schemes perform eccentricity compensation continuously throughout the whole process. However, during drilling processing, the vibrations generated by the tilted drill bit in the initial contact state, semi-feeding state and complete drilling state with the workpiece are completely different. A single compensation algorithm cannot simultaneously suppress instantaneous impact and continuous overturning deformation. Either the entrance impact eccentricity cannot be suppressed, or the continuous deflection vibration marks on the hole body are serious, making it difficult to guarantee processing accuracy. Summary of the Invention

[0004] Aiming at the problems in the prior art, the invention proposes the following technical scheme: In the dynamic eccentricity compensation inclined hole processing process for heavy-duty workpieces, based on the real-time cutting depth h of the drill bit and the diameter D of the drill bit, the processing intervals are divided into: idle traveling interval h≤0, material touching interval 0<h≤0.5D, semi-feeding interval 0.5D<h≤1.2D, and complete drilling interval h>1.2D, and the process includes the following steps: S1: Workpiece clamping and posture calibration: after the heavy-duty workpiece is rigidly pressed and fixed on the ground at multiple points, complete spindle inclination angle calibration and wiring debugging of various sensors, and the machine tool operates at the original rotation speed n in the idle traveling interval (h≤0) origin , original feed rate f origin ; S2: Processing in the material touching interval: before the drill bit contacts the workpiece, that is, in the material touching interval (0<h≤0.5D), vibration reduction cutting parameters are automatically switched, impact pre-compensation control is activated synchronously, and the drill bit then starts inclined hole processing; S3: Processing in the semi-feeding interval: after the center point of the drill bit is flush with the workpiece surface, that is, in the semi-feeding interval (0.5D<h≤1.2D), the vibration reduction parameters are maintained, and the processing is performed by switching to the steady-state torque compensation control mode; S4: Process switching after the drill bit completely drills in: after the drill bit completely enters the workpiece, that is, in the complete drilling interval (h>1.2D), perform 20ms smooth zeroing of compensation, cut off force feedback, restore the original rotation speed and original feed rate and put the compensation control into sleep; S5: Subsequent drilling process: Using the existing standard machining process of the machine tool, deep hole continuous cutting, hole position online detection, finished product error measurement, and compensation parameter storage are performed in sequence until the entire inclined hole is machined.

[0005] As a preferred embodiment of the above technical solution, in step S2, the vibration reduction cutting parameter is: instantaneous spindle speed n temp =0.7n origin Instantaneous feed f temp =0.6f origin .

[0006] As a preferred embodiment of the above technical solution, step S1 includes the following: S1.1 After the heavy-duty workpiece is fixed, the laser tool setter calibrates the axis of the inclined hole and the spindle tilt angle θ, and the static deformation data of the workpiece is stored in the CNC controller. S1.2, the tilt sensor and radial displacement sensor collect the no-load tool holder deflection and the spindle's inherent eccentricity as compensation references; S1.3, piezoelectric force sensors are installed on the spindle and workpiece base to collect the cutting force F with a period of 1ms. x F y F z The feed encoder outputs the cutting depth h in real time as the criterion for interval switching.

[0007] As a preferred embodiment of the above technical solution, in step S2, the impact pre-compensation control adopts a feedforward pre-compensation + fuzzy PID composite algorithm as follows: ; PID output: ; The X and Y bidirectional eccentricity correction displacement δ is calculated based on the control quantity. x δ y ; will δ x δ y The data is transmitted to the eccentricity compensation actuator for eccentricity correction.

[0008] As a preferred embodiment of the above technical solution, in step S3, the steady-state torque compensation control mode adopts a torque vector decoupling algorithm as follows: The first step is to calculate the resultant force of the oblique lateral cutting in real time: , The second step is to calculate the overturning moment by combining the real-time cutting depth: ; The third step is to calculate the torque compensation coefficient that adapts to the cutting depth: ; Fourth step: Use the bidirectional eccentricity correction displacement equations to calculate the eccentricity correction displacements along the X and Y axes respectively: ; The above formula yields the eccentricity correction displacement δ. x δ y This is converted into a hydraulic valve flow signal or a machine tool coordinate axis offset superposition output to achieve compensation.

[0009] As a preferred embodiment of the above technical solution, in step S4, the 20ms smooth zeroing process uses a linear decay formula: .

[0010] As a preferred embodiment of the above technical solution, the eccentric compensation actuator is a hydraulic counterweight slider symmetrically arranged on both sides of the spindle box; for a five-axis gantry machine tool without hydraulic counterweight, it relies on the superposition of δ values ​​on the XY coordinate axes. x δ y Complete vector eccentricity compensation.

[0011] As a preferred embodiment of the above technical solution, the CNC compensation controller has five built-in subroutines: stage judgment, feedforward pre-compensation, fuzzy PID correction, torque decoupling, and smooth exit. Each subroutine runs only in the corresponding machining stage.

[0012] The beneficial effects of this invention are as follows: Based on the real-time cutting depth of the drill bit, different processing intervals are divided. Cutting parameters are reduced and corresponding compensation algorithms are configured only during the drill bit contact and half-entry stages. This weakens the lateral impact load from the cutting source. For two different vibration conditions, instantaneous impact and continuous overturning deflection, feedforward fuzzy PID composite compensation and adaptive torque vector decoupling compensation are matched respectively. This can accurately offset the eccentric offset generated at different stages, significantly reducing spindle vibration and eccentric error at the entrance of the inclined hole. When the drill bit is fully drilled into the workpiece and the cutting force tends to stabilize, the compensation is gradually withdrawn and the standard processing parameters are restored through linear decay. This avoids secondary defects such as hole wall vibration caused by sudden changes in compensation amount, and also eliminates the controller computing power loss and additional trajectory deviation caused by continuous compensation during the stable cutting stage, thereby effectively ensuring the processing quality of the inclined hole. Attached Figure Description

[0013] Figure 1 The diagram shown is a process flow chart of an embodiment. Detailed Implementation

[0014] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions of the present invention will be clearly and completely described below in conjunction with the embodiments and the accompanying drawings.

[0015] Figure 1In the present invention, a dynamic eccentricity compensation oblique hole processing process for heavy-duty workpieces divides processing intervals into an idling interval h≤0, a material contacting interval 0<h≤0.5D, a semi-feeding interval 0.5D<h≤1.2D and a complete drilling interval h>1.2D based on the real-time cutting depth h of a drill bit and the diameter D of the drill bit, and comprises the following steps: S1: Workpiece clamping and posture calibration: After a heavy-duty workpiece is rigidly pressed on the ground at multiple points, spindle inclination calibration and wiring debugging of various sensors are completed, and a machine tool operates at an original rotation speed n in the idling interval (h≤0) origin and an original feed rate f origin ; The step S1 comprises the following contents: S1.1: After the heavy-duty workpiece is fixed, a laser tool setter calibrates an oblique hole axis and a spindle inclination θ, and static deformation data of the workpiece is stored in a CNC controller; S1.2: An inclination sensor and a radial displacement sensor collect no-load tool bar deflection and inherent eccentricity of a spindle to serve as a compensation reference; S1.3: Piezoelectric three-component force sensors are arranged on a spindle and a workpiece base, and cutting component forces F are collected at a period of 1 ms x , F y and F z ; a feed encoder outputs the cutting depth h in real time as a criterion for interval switching.

[0016] A dozens-of-ton heavy-duty workpiece is pressed by multiple pressing plates after being placed on the ground, so that workpiece displacement in a processing process is avoided, and posture adjustment through overturning is not needed; calibration of a spindle inclination angle and wiring debugging of a cutting force sensor and a depth encoder are completed. A theoretical processing axis of an oblique hole and an inclination angle of the spindle are calibrated through laser, static deformation generated by self weight of the workpiece and clamping extrusion is collected and stored in the controller; a sensor collects inherent eccentricity of the spindle and a tool bar in a no-load state to serve as a basis for compensation calculation; a piezoelectric sensor collects three-axis cutting force at a high frequency, and a feed encoder feeds back drilling depth in real time to provide a data basis for automatic interval switching. A compensation program keeps dormant in the idling interval, the machine tool adopts factory preset standard original rotation speed and original feed rate for idling, and no tool eccentricity correction action is performed.

[0017] S2: Processing in the material contacting interval: Before the drill bit contacts the workpiece, that is, in the material contacting interval (0<h≤0.5D), vibration reduction cutting parameters are automatically switched, impact pre-compensation control is started synchronously, and the drill bit starts oblique hole processing immediately; In the step S2, the vibration reduction cutting parameters are: instantaneous spindle rotation speed n temp =0.7n origin , instantaneous feed f temp =0.6f origin .

[0018] In the step S2, the impact pre-compensation control adopts a feedforward pre-compensation + fuzzy PID composite algorithm which is as follows: ; , the PID outputs: ; calculating the X and Y bidirectional eccentricity correction displacements δ based on the control quantity x and δ y ; transmitting δ x and δ y to an eccentricity compensation actuator for eccentricity correction, wherein the eccentricity compensation actuator is a hydraulic counterweight slider symmetrically arranged on both sides of a headstock; for a five-axis gantry machine tool without hydraulic counterweight, vector eccentricity compensation is completed by superimposing δ x and δ y on the X and Y coordinate axes.

[0019] The CNC compensation controller has five built-in subroutines: stage judgment, feedforward pre-compensation, fuzzy PID correction, torque decoupling, and smooth exit, and each subroutine only runs in the corresponding processing stage.

[0020] When the drill tip just contacts the workpiece surface, only a very small part of the cutting edge participates in cutting, resulting in extremely large unilateral impact load, which easily causes tool tip jitter and instantaneous eccentricity. In this step, the spindle speed and feed rate are automatically reduced to reduce cutting impact, and the entire compensation control system is awakened at the same time to start the feedforward + fuzzy PID composite compensation algorithm; the algorithm calculates the impact pre-compensation amount in advance by combining the inclination angle, cooperates with the fuzzy adaptive PID to correct the tool tip offset in real time, calculates the X and Y bidirectional correction displacements, offsets the eccentricity error caused by the instantaneous impact through reverse offset of the hydraulic counterweight or the machine tool coordinate axes, and controls the maximum compensation offset range to prevent the machine tool from overtraveling.

[0021] S3: Processing in the half-feeding interval: after the center point of the drill is flush with the workpiece surface, that is, in the half-feeding interval (0.5D<h≤1.2D), the vibration reduction parameters are maintained, and the steady-state torque compensation control mode is switched for processing; In step S3, the torque vector decoupling algorithm adopted by the steady-state torque compensation control mode is as follows: First step, calculating the oblique lateral resultant cutting force in real time: , Second step, calculating the cutting overturning moment by combining the real-time cutting depth: ; Third step, calculating the torque compensation coefficient adaptively changing with the cutting depth: ; Fourth step, obtaining the eccentric correction displacements of the X axis and Y axis respectively by adopting bidirectional eccentric correction displacement equation sets: ; In the formula, λ is the correction coefficient for the Y-axis component force; The above formula yields the eccentricity correction displacement δ. x δ y The compensation is achieved by converting the output into a hydraulic valve flow signal or a superimposed offset of the machine tool coordinate axis. The bidirectional eccentricity correction displacement equation set adopts a force-torque decoupling modeling approach, calculating the two types of eccentric disturbances—overturning moment and independent cutting force in the Y direction—separately, ensuring they do not interfere with each other. The X-axis compensation is determined solely by the overturning moment in real time and adaptively amplifies with drilling depth to match the gradually increasing deflection of the tool holder; the Y-axis compensation is corrected only for the cutting load on one side in the Y direction. The two sets of correction displacements are output synchronously to the compensation actuator, simultaneously canceling the drill bit eccentricity offset from two orthogonal directions and suppressing continuous low-frequency vibration in the half-feeding section. The negative sign in the equation set indicates that the direction of the compensation displacement is opposite to the direction of the eccentricity offset caused by the cutting force, achieving reverse cancellation correction.

[0022] The drill bit's cutting edge penetrates half to most of the workpiece without instantaneous impact. However, the continuous lateral cutting force generates an overturning moment as the drilling depth increases, causing the tool holder to continuously deflect and induce low-frequency chatter. This step maintains the low-speed vibration reduction parameters unchanged, disables the feedforward impact compensation module, and switches to the torque vector decoupling algorithm. The algorithm calculates the lateral resultant force and overturning moment in real time, with the compensation coefficient increasing linearly with the drilling depth to match the continuously increasing tool holder bending. It decouples and calculates bidirectional corrections from both the overturning moment and the Y-axis cutting force component, continuously balancing the steady-state eccentric load.

[0023] S4: Drill bit fully penetrates the workpiece and switches to the next step: After the drill bit has fully penetrated the workpiece, i.e., the full penetration range (h>1.2D), perform a 20ms compensation smooth zeroing, cut-off force feedback, restore the original speed and original feed rate, and then perform sleep compensation control. In step S4, the 20ms smooth zeroing uses a linear decay formula: .

[0024] With all cutting edges of the drill bit fully embedded in the workpiece and the surrounding material evenly supporting the drill bit, lateral forces and vibrations are significantly eliminated, eliminating the need for continuous compensation. To prevent secondary impact vibrations caused by the instantaneous zeroing of the compensation value, a 20-millisecond linear smooth decay program is set to gradually reduce the compensation output to zero; simultaneously, the cutting force sensor feedback loop is disconnected, the compensation program goes into hibernation, the machine tool resumes its standard original machining speed and feed rate, and the hydraulic counterweight locks off.

[0025] Based on the real-time cutting depth of the drill bit, different processing intervals are divided. Cutting parameters are reduced and corresponding compensation algorithms are configured only during the drill bit contact and half-entry stages. This weakens the lateral impact load from the cutting source. For two different vibration conditions, instantaneous impact and continuous overturning deflection, feedforward fuzzy PID composite compensation and adaptive torque vector decoupling compensation are matched respectively. This can accurately offset the eccentric offset generated at different stages, significantly reducing spindle vibration and eccentric error at the entrance of the inclined hole. When the drill bit is fully drilled into the workpiece and the cutting force tends to stabilize, the compensation is gradually withdrawn and the standard processing parameters are restored through linear decay. This avoids secondary defects such as hole wall vibration caused by sudden changes in compensation amount, and also eliminates the controller computing power loss and additional trajectory deviation caused by continuous compensation during the stable cutting stage, thereby effectively ensuring the processing quality of the inclined hole.

[0026] S5: Subsequent drilling process: Using the existing standard machining process of the machine tool, deep hole continuous cutting, hole position online detection, finished product error measurement, and compensation parameter storage are performed in sequence until the entire inclined hole is machined.

[0027] Once the drill bit is fully inserted, no eccentricity compensation program is activated again. The machine tool's existing mature standard processing flow is used for continuous deep hole feeding. During processing, the machine is stopped in stages to detect the hole axis deviation using laser. After processing, the hole position and eccentricity error are measured using a coordinate measuring machine and an inner diameter gauge. The optimized compensation algorithm coefficients and control parameters of this processing are stored in the controller database. The entire process can be directly called up for the next processing of the same specification workpiece until the overall processing of the inclined hole is completed.

[0028] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it.

Claims

1. A dynamic eccentricity compensation inclined hole machining process for heavy-load workpieces, which divides machining intervals into an idling interval h≤0, a material contacting interval 0<h≤0.5D, a half feeding interval 0.5D<h≤1.2D, and a full drilling interval h>1.2D based on real-time cutting depth h of a drill bit and diameter D of the drill bit, characterized in that, It comprises the following steps: S1: Workpiece clamping and attitude calibration: After rigidly clamping the heavy-duty workpiece at multiple points, complete the spindle tilt angle calibration and wiring and debugging of various sensors. The machine tool operates at its original speed n during the idle travel range (h≤0). origin Original feed rate f origin run; S2: Processing in the contact interval: before the drill bit contacts the workpiece, that is, in the contact interval (0<h≤0.5D), the vibration-damping cutting parameters are automatically switched, and the impact pre-compensation control is activated synchronously, and the drill bit starts inclined hole processing immediately; S3: Processing in the half-feeding interval: after the center point of the drill bit is flush with the surface of the workpiece, that is, in the half-feeding interval (0.5D<h≤1.2D), the vibration-damping parameters are maintained, and the steady-state torque compensation control mode is switched for processing; S4: Process switching after the drill bit is completely drilled in: after the drill bit completely enters the workpiece, that is, in the complete drilling interval (h>1.2D), 20ms compensation smooth zeroing is performed, the force feedback is cut off, the original rotation speed and original feed rate are restored, and the compensation control is put into sleep; S5: Subsequent drilling processing: follow the original standard processing technology of the machine tool, sequentially perform continuous cutting of deep holes, online detection of hole positions, measurement of finished product errors, and storage of compensation parameters until the processing of the entire inclined hole is completed.

2. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 1, characterized in that, In step S2, the vibration reduction cutting parameters are: instantaneous spindle speed n temp =0.7n origin Instantaneous feed f temp =0.6f origin .

3. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 1, characterized in that, The step S1 includes the following contents: S1.1, after the heavy-duty workpiece is fixed, the laser tool setter calibrates the inclined hole axis and the spindle inclination θ, and the static deformation data of the workpiece is stored in the CNC controller; S1.2, the inclination sensor and radial displacement sensor collect the deflection of the unloaded tool bar and the inherent eccentricity of the spindle as compensation benchmarks; S1.3, piezoelectric force sensors are installed on the spindle and workpiece base to collect the cutting force F with a period of 1ms. x F y F z The feed encoder outputs the cutting depth h in real time as the criterion for interval switching.

4. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 1, characterized in that, In step S2, the impact pre-compensation control adopts a feedforward pre-compensation + fuzzy PID composite algorithm as follows: ； PID output: ； The X and Y bidirectional eccentricity correction displacement δ is calculated based on the control quantity. x δ y ; will δ x δ y The data is transmitted to the eccentricity compensation actuator for eccentricity correction.

5. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 4, characterized in that, In step S3, the steady-state torque compensation control mode adopts a torque vector decoupling algorithm as follows: The first step is to calculate the oblique lateral resultant cutting force in real time: ， The second step is to calculate the cutting overturning moment by combining the real-time cutting depth: ； The third step is to calculate the torque compensation coefficient that adaptively changes with the cutting depth: ； The fourth step is to use the bidirectional eccentricity correction displacement equations to solve the eccentric correction displacements of the X-axis and Y-axis respectively: ； The above formula yields the eccentricity correction displacement δ. x δ y This is converted into a hydraulic valve flow signal or a machine tool coordinate axis offset superposition output to achieve compensation.

6. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 5, characterized in that, In step S4, the 20ms smooth zeroing adopts a linear attenuation formula as follows: 。 7. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 5, characterized in that, The eccentric compensation actuator is a hydraulic counterweight slider symmetrically arranged on both sides of the spindle box; for a five-axis gantry machine tool without hydraulic counterweight, it relies on the superposition of δ values ​​along the XY coordinate axes. x δ y Complete vector eccentricity compensation.

8. The dynamic eccentric compensation type inclined hole machining process for heavy-duty workpieces according to claim 1, characterized in that: The CNC compensation controller has five built-in subroutines: stage judgment, feedforward pre-compensation, fuzzy PID correction, torque decoupling, and smooth exit, and each subroutine only runs in the corresponding processing stage.

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