A counterweight metal sheet punching device and method

Abstract

This invention relates to a device and method for drilling counterweight metal sheets, belonging to the field of drilling technology. The device includes a base, a worktable, a rotary cutting mechanism, a feed drive mechanism, a counterweight balancing assembly, a cutting fluid supply system, and a control unit, which are electrically connected to a drive motor, a feed drive mechanism, and a fluid pump, respectively, for controlling the rotational speed, feed speed, and cutting fluid supply of the rotary cutting mechanism. Through active tool centering compensation, adjustable eccentric counterweight, pressure adaptive positioning fixture, and vibration-speed-feed speed linkage adjustment algorithm, the static runout and dynamic cutting force imbalance problems in U-drill drilling are systematically solved, achieving high-precision, high-efficiency, and long-life automated drilling processing.

Description

Technical Field

[0001] This invention relates to a device and method for drilling counterweight metal sheets, belonging to the field of drilling technology. Background Technology

[0002] Counterweight metal sheets are widely used in machinery manufacturing, automotive parts, electronic equipment, and other fields. Drilling is a core processing step, requiring high precision in hole position, hole diameter, and processing efficiency. Currently, twist drills or ordinary U-drills are commonly used as cutting tools in the drilling of counterweight metal sheets. Among them, U-drills are gradually becoming the mainstream choice due to their high cutting speed and strong chip removal capability. However, in practical applications, there are still many technical pain points that seriously affect processing quality and production efficiency.

[0003] On the one hand, ordinary U-drills are prone to static runout during the drilling of counterweight metal sheets. This static runout is mainly caused by static factors such as tool clamping deviation, radial runout of the transmission spindle, and geometric accuracy deviation of the U-drill itself. It manifests as a fixed offset between the U-drill's rotation center and the theoretical hole center, leading to defects such as hole position displacement, enlarged hole diameter, and flared hole opening. This reduces hole diameter accuracy and increases hole wall roughness, becoming a core bottleneck restricting machining accuracy. Existing technologies for addressing U-drill runout mostly rely on passive centering, using only mechanical structures to limit the offset. They cannot detect the runout amount in real time and actively compensate for it, resulting in limited centering accuracy and failing to completely solve the static runout problem.

[0004] On the other hand, U-drills are prone to dynamic cutting force imbalance during dynamic cutting. Because U-drills use a combination of center and peripheral inserts, their cutting areas and stress states naturally differ. Combined with dynamic factors such as uneven weighting, fluctuating cutting loads, and chip entanglement, this leads to real-time fluctuations in cutting force, causing tool vibration, hole distortion, and uneven insert wear. This not only shortens the lifespan of the U-drill inserts but also further exacerbates static runout, creating a vicious cycle. Current technologies mostly use general-purpose cutting parameter adjustments without a dedicated adjustment strategy for the cutting force balance of the dual inserts in U-drills. This makes it difficult to accurately identify abnormal stress on the dual inserts and effectively suppress dynamic cutting force fluctuations, resulting in inconsistent insert lifespan, difficulty in chip breaking, and long single-hole machining times, making them unsuitable for automated mass production.

[0005] In light of this, research has been conducted in related fields to address the cutting stability of U-drills. For example, Chinese Patent Publication No. CN115815661A discloses a dynamically adjustable indexable shallow hole drill and its dynamic balancing adjustment assembly. This design uses an arc-shaped guide rail slider mechanism and a counterweight slider to adjust the dynamic balance of the drill bit, thus solving the problem of poor dynamic balance in indexable shallow hole drills. However, this solution falls under the category of static balancing, allowing only one-time adjustment before machining or while the machine is stopped. It cannot respond in real-time to fluctuations in dynamic cutting forces during the cutting process, nor can it detect and actively compensate for radial tool offset. Its effectiveness in suppressing vibration and correcting runout during dynamic cutting is limited.

[0006] Furthermore, the homogeneity of the material and angle design of the cutter body and inserts in ordinary U-drills makes it impossible to balance the cutting performance in the central area with the wear resistance of the surrounding area. The inserts are prone to breakage and wear too quickly. At the same time, problems such as vibration interference, chip entanglement, and insufficient cleanliness of cutting fluid during the cutting process further aggravate the machining defects. As a result, existing counterweight metal sheet drilling devices have problems such as low precision, low efficiency, short tool life, and limited applicability, which cannot meet the needs of industrial upgrading for high-precision, high-efficiency, and long-life machining. Summary of the Invention

[0007] The purpose of this invention is to provide a counterweight metal sheet drilling device and method that overcomes the shortcomings of the prior art. By using active tool centering compensation, adjustable eccentric counterweight, pressure adaptive positioning fixture, and vibration-speed-feed speed linkage adjustment algorithm, it systematically solves the problems of static sway and dynamic cutting force imbalance in U-drill drilling, and achieves high-precision, high-efficiency, and long-life automated drilling processing.

[0008] The present invention provides a punching device for counterweight metal sheets, comprising: The base is used to support and fix the various functional components; The workbench, located above the machine base, is used to place the counterweight metal sheet to be processed; The rotary cutting mechanism includes a drive motor, a transmission spindle, a tool centering compensation mechanism, and a U-drill. The output end of the drive motor is connected to the transmission spindle. The U-drill is fixedly mounted on the lower end of the transmission spindle. The U-drill is a hole drill with indexable inserts, including a center insert and peripheral inserts. The drilling diameter matches the target diameter of the hole to be machined. The tool centering compensation mechanism is used to actively compensate for the radial position of the transmission spindle, so that the rotation center of the U-drill always coincides with the theoretical hole center. The feed drive mechanism is located between the machine base and the rotary cutting mechanism, and is used to drive the rotary cutting mechanism to perform vertical reciprocating feed motion relative to the worktable; The counterweight balancing assembly is fixedly installed on the upper part of the transmission spindle or on the opposite side of the drive motor to balance the eccentric torque and unbalanced vibration generated by the rotary cutting mechanism during high-speed rotation and feeding. The cutting fluid supply system includes a cutting fluid tank, a delivery pump, and a nozzle, wherein the nozzle is aligned with the cutting contact area between the U-drill tool and the counterweight metal plate through the inside of the drill rod; The control unit is electrically connected to the drive motor, feed drive mechanism, and fluid pump, and is used to control the rotation speed, feed speed, and cutting fluid supply of the rotary cutting mechanism.

[0009] The cutting fluid supply system includes a dual filtration device: a magnetic filter in the first stage and a 5μm precision filter in the second stage. The U-drill tool is equipped with an internal cooling channel, and the cutting fluid can be supplied to the cutting surface of the tool through the spindle center to reduce the cutting temperature during dynamic cutting, reduce cutting force fluctuations, and assist the linkage adjustment algorithm to achieve dynamic cutting force balance.

[0010] Preferably, the tool centering compensation mechanism includes an elastic centering sleeve and a displacement compensation sensor. The elastic centering sleeve is fitted onto the lower end of the drive spindle and positioned above the U-drill tool. Circumferentially distributed miniature elastic elements (such as disc springs or rubber bellows) are provided between the inner hole of the elastic centering sleeve and the drive spindle to automatically absorb radial displacement generated by the tool during high-speed rotation and cutting forces. The displacement compensation sensor is located on the outer periphery of the elastic centering sleeve to detect the radial displacement of the U-drill tool in real time and feed it back to the control unit. Based on the feedback signal from the displacement compensation sensor, the control unit actively compensates for the radial position of the drive spindle by driving a fine-tuning actuator (such as a piezoelectric ceramic actuator or a miniature servo push rod) mounted on the mounting base. This ensures that the rotation center of the U-drill tool always coincides with the theoretical hole center, specifically designed to solve the static runout problem of the U-drill tool caused by static factors such as tool clamping deviation, spindle radial runout, and deviations in the tool body's geometric accuracy.

[0011] Preferably, the U-drill tool uses a combination of a gradient hardness composite structure tool body and indexable inserts. The tool body is made of high-toughness alloy steel (such as 42CrMo) with a hardness of HRC38-42, and the insert mounting groove is locally hardened. The center insert has a positive rake angle design of 8°-12° to reduce cutting resistance and improve impact resistance; the peripheral inserts have a negative rake angle design of -3°-0° to improve wear resistance and ensure hole wall quality. All inserts are made of PVD-coated cemented carbide, and the tool body is made of high-toughness alloy steel with a hardness of HRC38-42. The insert mounting groove is locally hardened to a hardness of HRC50-55. Both the center and peripheral inserts use a PVD-coated cemented carbide substrate with a coating of TiAlN or AlCrN, a coating thickness of 2-4μm, and an insert hardness of HV3000-3500. A precision positioning groove and clamping screw are provided at the interface between the tool body and the inserts to ensure a repeatability accuracy of ≤0.02mm after insert replacement.

[0012] Preferably, the counterweight balancing component is an adjustable eccentric counterweight component, including at least two sector-shaped counterweights and an eccentric adjustment disc, which can steplessly adjust the magnitude and direction of the eccentricity to help suppress the vibration of the rotary cutting mechanism and further improve the static centering accuracy in conjunction with the tool centering compensation mechanism.

[0013] Preferably, the worktable is equipped with a positioning fixture, which is a pressure-adaptive positioning fixture, including a proportional pressure regulating valve and a diaphragm pressure sensor. The control unit automatically adjusts the clamping pressure according to the workpiece material to avoid static runout errors caused by workpiece deformation during clamping, and at the same time prevents workpiece displacement from affecting the cutting force balance during dynamic cutting.

[0014] Preferably, the control unit incorporates a vibration-rotation speed-feed speed linkage adjustment algorithm module. This module takes the real-time vibration amplitude and frequency feedback from the vibration sensor, the spindle load current, and the current feed depth as inputs, and the rotational speed correction and feed speed correction as outputs. It achieves dynamic parameter matching based on fuzzy PID or model predictive control. By analyzing the fluctuation spectrum of the spindle current, it identifies unstable center insert entry or wear of peripheral inserts. For the U-drill, it performs spectrum analysis and adjustment to address the imbalance of cutting forces between the center and peripheral inserts, resolving the dynamic cutting force imbalance caused by factors such as material inhomogeneity, cutting load fluctuations, and differences in force between the two inserts during dynamic cutting, thus suppressing tool vibration.

[0015] Specifically, the algorithm module performs a Fast Fourier Transform (FFT) on the vibration and current signals to extract the following characteristic frequencies: f1=n×z c / 60: The center blade passing frequency reflects the center blade's cutting impact; where z cThe number of teeth on the center blade (usually 1 or 2); f2=n×z p / 60: Peripheral insert passage frequency, reflecting the periodic cutting impact of the peripheral insert; where z p This refers to the number of teeth on the peripheral blade (usually 1 or 2). Low frequency range (0.5-2 times spindle speed): reflects overall tool imbalance; High-frequency broadband energy (500Hz-2kHz): reflects blade chipping or chip impact.

[0016] The algorithm module calculates the ratio of the amplitude spectral density of each characteristic frequency to the "healthy baseline spectrum" stored during the trial-cut self-tuning stage, obtaining the imbalance coefficients K1, K2, K3, and K4. Based on fuzzy rules, the rotational speed correction coefficient α is dynamically output. n and feed rate correction factor α f Specifically designed for U-drill dual-insert cutting force balance, featuring a built-in active balancing adjuster: When K1 > 1.3 (center cutting tool overload) and the drilling phase is underway, the feed rate should be reduced first (α). f =-0.15), and appropriately increase the rotational speed (α). n =+0.05), improves chip breaking of the center blade; When K2 > 1.4 (peripheral cutting tool overload) and the drill is in the main drilling stage, reduce the feed rate (α). f =-0.10), the rotation speed decreases slightly or remains unchanged, protecting the surrounding blades; When K4>2.0, the blade breakage alarm is triggered, and the machine automatically retracts the blade and stops. When K2 remains too high for more than 10 holes, fine-tune the spindle speed (±3% each time) to change the cutting phase and make the wear of the peripheral blades more uniform.

[0017] This linkage adjustment algorithm ensures that the U-drill always operates within the optimal stable cutting range, effectively suppressing dynamic cutting force fluctuations, reducing the tool breakage rate, and improving hole shape accuracy.

[0018] The present invention also provides a method for drilling holes in a counterweight metal sheet using the above-mentioned device, comprising the following steps: Step S1: Workpiece positioning and clamping. Place the counterweight metal sheet to be processed on the worktable, and center and clamp it using a pressure adaptive positioning fixture.

[0019] Specifically, the counterweight metal sheet to be processed is placed on the positioning fixture of the worktable. The control unit first completes the material determination of the counterweight metal sheet through the preset material identification module. The material identification module can be implemented in two ways: one is to manually input the material parameters of the counterweight metal sheet to be processed (such as stainless steel, titanium alloy, ordinary carbon steel, etc.) in advance on the operation interface of the control unit and call the preset material-clamping pressure database; the other is to use the material detection sensor (such as eddy current sensor or hardness sensor) integrated on the positioning fixture to detect the material characteristics (such as hardness, conductivity) of the counterweight metal sheet in real time and transmit the detection signal to the control unit, which will automatically match the corresponding material type. After material determination, the control unit sends a control signal to the proportional pressure regulating valve of the pressure adaptive positioning fixture based on the preset material-clamping pressure correspondence, automatically adjusting the clamping pressure: for counterweight metal sheets with low hardness and easy deformation (such as low carbon steel, hardness HRC≤25), the clamping pressure is adjusted to 0.1-0.2MPa to avoid plastic deformation of the workpiece caused by high-pressure clamping; for counterweight metal sheets with high hardness and not easy deformation but requiring stable positioning (such as stainless steel, titanium alloy, hardness HRC25-62), the clamping pressure is adjusted to 0.3-0.5MPa to ensure that the workpiece is firmly positioned; at the same time, the thin-film pressure sensor on the positioning fixture collects the actual clamping pressure signal in real time and feeds it back to the control unit, forming a pressure closed-loop regulation, so that the deviation between the actual clamping pressure and the target pressure is controlled within ±0.01MPa, completing the accurate positioning and reliable clamping of the workpiece. The entire clamping process, through precise pressure adjustment, can effectively prevent workpiece deformation during clamping, thereby eliminating static runout error of the U-drill tool caused by clamping deformation, and laying a stable workpiece foundation for the subsequent operation of the static runout compensation mechanism.

[0020] Step S2: Trial Cutting and Self-Tuning. For each batch of counterweight metal sheets or after material change, a trial cut is performed with conservative parameters. The control unit automatically collects the spindle load current curve, vibration spectrum, and actual hole diameter deviation data. Through the self-tuning algorithm, it generates the optimal target cutting current value, the maximum allowable vibration spectral density threshold, and the optimal speed-feed speed matching curve. At the same time, it automatically calibrates the cutting force balance coefficient of the center insert and the peripheral inserts, providing reference data for static runout compensation and dynamic cutting force balance adjustment.

[0021] Step S3: Batch Adaptation and Call. The control unit calls the optimal machining parameters stored in step S2 to determine the rotational speed and feed rate of the U-drill tool. The rotational speed setting range of the U-drill is 800-4000 r / min, and the feed rate setting range is 100-800 mm / min. The specific values ​​are determined by the self-tuning results.

[0022] Step S4: Rotary cutting pre-start. Start the drive motor to drive the U-drill tool to rotate at the set speed under no-load, and at the same time turn on the cutting fluid supply system; at this time, the tool centering compensation mechanism is activated, the displacement compensation sensor detects the radial displacement of the U-drill tool in real time, and the control unit drives the fine-tuning actuator to perform active compensation to eliminate static runout under no-load conditions.

[0023] Step S5: Incremental feed cutting. The feed drive mechanism is activated, driving the rotary cutting mechanism downwards at a set feed rate. After the U-drill tool's insert contacts the surface of the counterweight metal sheet, material is removed through rotary drilling, forming a circular through hole. During this process, the control unit synchronously executes the following control strategies: Graded Dynamic Vibration Threshold Control: Targeting the characteristics of U-drilling, graded dynamic vibration threshold control is implemented for the cutting process. Specifically, based on the ratio of feed depth h to workpiece thickness H, the cutting process is divided into three zones: the entry stability zone (0 ≤ h < 0.15H), the main drilling zone (0.15H ≤ h < 0.85H), and the exit anti-breakage zone (0.85H ≤ h ≤ H), with optimal thresholds of 0.5, 1.0, and 0.4 times respectively. When the actual vibration amplitude exceeds the dynamic threshold of the current zone, the control unit intervenes according to a graded strategy of "reducing feed speed → reducing rotational speed → pausing feed."

[0024] Spindle load current feedforward-feedback composite regulation: The feedforward part is based on the target current curve obtained by trial cutting self-tuning; the feedback part adopts incremental PID, mainly adjusting the feed rate and secondarily adjusting the rotational speed. The control unit monitors the current harmonic components corresponding to the center insert separately. When an abnormal increase in the cutting force of the center insert is detected, the feed rate is reduced first and the rotational speed is appropriately increased (10%-15%) to improve chip breaking at the center and help balance the cutting force of the two inserts.

[0025] Specifically, the feedback section samples the actual spindle current I every 10ms. actual Calculate the deviation e=I target (h)-I actual The incremental PID algorithm is used to calculate the adjustment amount Δv of the feed rate. f =Kp× e+Ki ×∫edt+Kd×de / dt, where Kp, Ki, and Kd are coefficients automatically calibrated through trial cutting self-tuning. Speed ​​adjustment is an auxiliary function, activated only when the feed rate adjustment has reached its limit (e.g., below the minimum safe feed rate of 30mm / min) and the deviation has not been eliminated. (3) Segmented feed + intermittent chip breaking strategy: Divide the feed stroke into several segments, each segment having a length L seg=min(1.5mm,0.25H); After each segment, a chip-breaking action is performed: "pause feed for 0.1s → spindle instantaneous reverse for 0.05s → forward rotation and acceleration for 0.1s". The chip shearing force during the reverse rotation is used to forcibly break the ribbon-like chips. At the same time, at the beginning of each segment, the feed speed is modulated with a sine wave (frequency 60-120Hz, amplitude 15%-25%) to make the chips form C-shaped or spiral short chips.

[0026] Specifically, the feed rate is modulated in a sinusoidal form: vf(t) = vf0 + Δv × sin(2πft), where the modulation frequency f = 60-120Hz, and the modulation amplitude Δv is 15%-25% of the base speed vf0. This micro-amplitude, high-frequency feed rate fluctuation causes periodic cross-sectional changes in the chips, forming short C-shaped or spiral chips with a length ≤2mm. After adopting this strategy, the chip entanglement rate is reduced by 90%, the peak cutting force is reduced by 50%, and the incidence of microcracks in the hole wall is reduced to below 0.2%.

[0027] Static runout and dynamic cutting force balance coordinated control: The tool centering compensation mechanism works continuously, detecting the radial displacement of the U-drill tool in real time, eliminating static runout caused by tool wear, spindle vibration, and other factors during cutting; the vibration-speed-feed rate linkage adjustment algorithm module operates synchronously, identifying abnormal cutting forces of the dual-insert tool through spectrum analysis, dynamically adjusting the speed and feed rate to suppress dynamic cutting force fluctuations. These two mechanisms work together to ensure drilling accuracy and tool life. Details are as follows: First, the prerequisite for collaborative control is synchronous data acquisition and real-time communication: The control unit synchronously receives two core signals. The first is the radial displacement data of the U-drill tool collected by the displacement compensation sensor (sampling frequency 10kHz, detection accuracy ±0.001mm) in the tool centering compensation mechanism. This data is used to identify static runout (including fixed offsets caused by static factors such as tool clamping deviation, spindle radial runout, and tool body geometric accuracy deviation, as well as dynamic static runout increments caused by tool wear and slight workpiece displacement during cutting). The second is the vibration amplitude, frequency, and spindle load current data collected by the vibration sensor (sampling frequency 10kHz) and spindle current sensor (sampling frequency 2kHz). This data is analyzed and processed by the linkage adjustment algorithm module to identify the type of dynamic cutting force imbalance (such as unstable center insert entry, peripheral insert wear, and force imbalance caused by chip entanglement) and its corresponding fluctuation amplitude. Both signals are transmitted in real-time to the collaborative control module of the control unit, achieving data synchronization and seamless communication, providing precise data support for collaborative adjustment.

[0028] Secondly, the linkage adjustment logic between static runout compensation and dynamic cutting force balance is divided into three core stages, adapting to different working conditions throughout the cutting process: 1. Pre-cutting Co-calibration Stage (corresponding to step S4 Rotary Cutting Pre-start): At this time, the U-drill is in an unloaded rotating state with no dynamic cutting force. The co-control mainly uses static runout compensation and is supplemented by dynamic parameter pre-adjustment. The tool centering compensation mechanism is activated, and the displacement compensation sensor detects the radial displacement of the U-drill in real time. The control unit drives the fine-tuning actuator (piezoelectric ceramic actuator, compensation accuracy ≤0.002mm) to perform active compensation, correcting the deviation between the U-drill rotation center and the theoretical hole position center to ≤0.003mm, completing the initial calibration of static runout. At the same time, the linkage adjustment algorithm module calls the health reference spectrum of the trial cutting self-tuning stage, presets the vibration threshold and current threshold corresponding to the initial rotation speed and feed rate, and completes the pre-setting of dynamic control parameters to ensure that the dynamic cutting force quickly stabilizes during entry and avoids static runout rebound caused by entry impact.

[0029] 2. Cutting process coordinated adjustment stage (corresponding to step S5 progressive feed cutting): At this time, the U-drill contacts the workpiece, dynamic cutting force is generated, static runout and dynamic cutting force fluctuation affect each other, and the coordinated control module synchronously performs dual adjustment to achieve dynamic balance between the two: Real-time static runout compensation: The displacement compensation sensor continuously monitors the radial displacement of the U-drill. When the detected static runout exceeds 0.005mm (i.e., exceeds the centering accuracy threshold), the collaborative control module prioritizes triggering the tool centering compensation mechanism. The fine-tuning actuator quickly adjusts the radial position of the transmission spindle to correct the runout to within the threshold. Simultaneously, the abnormal runout signal is fed back to the linkage adjustment algorithm module. The algorithm module combines the current vibration data and current data to determine whether the abnormal runout is caused by dynamic cutting force imbalance (such as uneven force on the double inserts or chip impact). If it is caused by dynamic factors, the rotation speed and feed rate are adjusted synchronously to suppress dynamic fluctuations from the source and prevent repeated runout. For example, when the displacement compensation sensor detects a continuous increase in the radial displacement of the U-drill (runaway ≥ 0.006 mm), and the vibration sensor detects high-frequency vibration (frequency 500-1000 Hz) and increased spindle current fluctuations, it indicates that wear of the peripheral cutting tools leads to an imbalance in dynamic cutting force, which in turn exacerbates static runaway. At this time, the collaborative control module controls the fine-tuning actuator to compensate for the runaway on the one hand, and the linkage algorithm module reduces the feed rate and fine-tunes the rotation speed on the other hand to balance the cutting force of the peripheral cutting tools and eliminate the influence of dynamic fluctuations on static runaway.

[0030] Dynamic cutting force balance adaptation and adjustment: After identifying the type of cutting force imbalance in the dual-insert tool through spectrum analysis, the linkage adjustment algorithm module simultaneously adapts to the static runout compensation state when adjusting the spindle speed and feed rate, avoiding the exacerbation of static runout caused by parameter adjustments. For example, when the unstable cutting of the center insert (large fluctuations in low frequency <100Hz) is detected, requiring a reduction in feed rate and an increase in spindle speed to improve chip breaking, the collaborative control module will predict in advance the radial displacement change of the U-drill that may be caused by parameter adjustments, control the tool centering compensation mechanism to enter the pre-compensation state, monitor the displacement data in real time, and immediately make fine adjustments if slight runout occurs, ensuring that the static runout remains within the threshold during parameter adjustments. At the same time, the algorithm module adjusts the adjustment range to avoid sudden changes in spindle speed and feed rate, reducing interference with static centering, and achieving synchronous adaptation of dynamic cutting force balance and static runout compensation.

[0031] Cutting Stage Adaptation Optimization: For the three different cutting stages—drilling in, main drilling, and drilling out—the collaborative control module adjusts the adjustment priorities and parameter thresholds of both: In the drilling in stage, static runout compensation is prioritized to strictly control the deviation between the U-drill rotation center and the theoretical hole center, while reducing the dynamic cutting force adjustment amplitude to avoid runout caused by entry impact; In the main drilling stage, static runout compensation and dynamic cutting force balance have equal priority, continuously optimizing their states to ensure a stable cutting process; In the drilling out stage, dynamic cutting force balance is prioritized to reduce feed rate and vibration impact, while the tool centering compensation mechanism continues to work to avoid static runout caused by stress release during drilling out, preventing edge chipping and hole diameter deviation.

[0032] 3. Collaborative Protection Phase for Abnormal Operating Conditions: When the collaborative control module detects a serious abnormality (such as static runout ≥ 0.01 mm, vibration amplitude exceeding the current threshold by 150%, or abnormal spike in spindle current), it immediately triggers the collaborative protection mechanism: the tool centering compensation mechanism stops active compensation, maintains its current position, and avoids over-adjustment that exacerbates the deviation; the linkage adjustment algorithm module immediately outputs an emergency stop and tool retraction command, controls the feed mechanism to stop feeding, and the U-drill to decelerate and rotate, while continuously collecting displacement, vibration, and current data and recording abnormal information; after the equipment stops, the control unit prompts the operator to check the wear condition of the U-drill insert, the workpiece clamping status, and the spindle running status. After eliminating the abnormality, the collaborative calibration process is restarted to ensure subsequent machining accuracy.

[0033] Finally, regarding the details of parameter adaptation for collaborative control: For machining counterweight metal sheets of different materials and hole diameters, the collaborative control module automatically calls the reference data from the trial cutting self-tuning stage to adjust the static runout compensation threshold, the dynamic cutting force adjustment range, and the linkage response speed of the two. For example, when machining high-hardness 304 stainless steel counterweight metal sheets, the static runout compensation threshold is adjusted to ≤0.004mm, the dynamic cutting force adjustment range is appropriately increased, and the linkage response speed is accelerated (data comparison is performed every 5ms, and adjustment command is executed every 20ms). When machining large-diameter holes (such as 70mm), due to the large rotational inertia of the U-drill and the more obvious fluctuations in dynamic cutting force, the collaborative control module increases the sampling frequency of the displacement compensation sensor (increased to 15kHz), expands the stroke range of the fine-tuning actuator, and optimizes the fuzzy rules of the algorithm module to ensure the collaborative adaptation of static runout compensation and dynamic cutting force balance, avoiding the exacerbation of static runout by vibration during large-diameter drilling.

[0034] Through the aforementioned collaborative control mechanism, seamless linkage between static runout compensation and dynamic cutting force balance is achieved. This not only completely eliminates fixed runout caused by static factors such as tool clamping and spindle runout, but also effectively suppresses instantaneous runout caused by dynamic factors such as uneven force on the dual cutting tools and chip entanglement. This ensures that the rotation center of the U-drill always coincides with the theoretical hole position center, and the cutting force remains stable, providing a core guarantee for achieving the required hole diameter accuracy and hole wall roughness.

[0035] Step S6: Reset and retraction. When the feed rate reaches the workpiece thickness, the control unit controls the U-drill tool to remain at the bottom of the hole and continues to supply cutting fluid to flush the chips in the hole, and then quickly retracts at a retraction speed of ≥500mm / min.

[0036] Step S7: Hole Position Adjustment. Based on the distribution of the holes to be machined, control the worktable or rotary cutting mechanism to move to the next hole position, and repeat steps S4-S6 until all drilling operations are completed.

[0037] A device and method for drilling holes in a counterweight metal sheet has the following beneficial effects: 1. Completely solve the static runout problem: Through the active tool centering compensation mechanism, the radial offset of the U-drill is detected and actively compensated in real time. Combined with the pressure adaptive positioning fixture, the workpiece clamping deformation is avoided, the centering accuracy is greatly improved, the hole diameter accuracy reaches IT7-IT8, and the hole wall roughness Ra≤1.6μm.

[0038] 2. Effectively suppresses dynamic cutting force imbalance: Through vibration-speed-feed speed linkage adjustment algorithm and spectrum analysis, it accurately identifies the abnormal force on the center insert and the peripheral inserts, dynamically matches the optimal cutting parameters, reduces the tool breakage rate by 95%, improves the hole shape accuracy by more than 30%, and significantly improves the consistency of insert life.

[0039] 3. Significantly extended tool life: The gradient hardness composite structure of the U-drill body and the differentiated insert design (positive rake angle of the center insert and negative rake angle of the peripheral inserts) take into account both cutting performance and wear resistance, and the insert life is extended by more than 120% compared with conventional U-drills.

[0040] 4. Significantly improved processing efficiency: U-drills have high cutting speeds, and with adaptive parameter optimization and active chip breaking strategies, the processing time for a single hole is reduced by 40%-60% compared to traditional twist drills, making them suitable for mass automated production.

[0041] 5. Wide material adaptability: It can process materials ranging from low carbon steel to high hardness alloy steel, stainless steel, titanium alloy and other difficult-to-cut materials. It can quickly adapt to different batches of materials through trial cutting and self-tuning.

[0042] 6. Good system coordination: Tool centering compensation, adjustable eccentric counterweight, pressure adaptive fixture, linkage adjustment algorithm and segmented chip breaking strategy work together to form a complete closed loop from static compensation to dynamic suppression, which significantly improves machining stability and consistency. Attached Figure Description

[0043] Figure 1 This is a schematic diagram of the structure of a counterweight metal sheet punching device according to the present invention; Figure 2 is a structural schematic diagram of a U-drill tool according to the present invention; Figure 3 This is a schematic diagram of the process flow of a counterweight metal sheet punching device according to the present invention.

[0044] In the diagram: 1-Base; 2-Worktable; 3-Counterweight metal plate; 4-Drive motor; 5-Transmission spindle; 6-U-drill tool; 61-Tool body; 62-Center insert; 63-Peripheral insert; 7-Feed drive mechanism; 8-Counterweight balance assembly; 9-Cut fluid supply system; 91-Dual filtration device; 10-Tool centering compensation mechanism; 101-Elastic centering sleeve; 102-Displacement compensation sensor; 103-Fine-tuning actuator; 11-Positioning fixture. Detailed Implementation

[0045] The technical solutions of the present invention will be clearly and completely described below with reference to the accompanying drawings of the embodiments of the present invention. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Example

[0046] like Figures 1-3 As shown, this invention proposes a specific application of a counterweight metal sheet drilling device and method, used to process a counterweight metal sheet 3 with a thickness of 10mm and a material of 304 stainless steel (tensile strength 715MPa), with a target hole diameter of 70mm. Specific implementation details are as follows: I. Adaptation and Adjustment of Device Structural Parameters Base 1: The HT200 cast iron material is used, and the size is adjusted to 1200mm×800mm×600mm to enhance the overall rigidity of the device, adapt to the stability of large-diameter U-drills when rotating at high speed, suppress the overall vibration of the equipment, and avoid the vibration from aggravating static sway.

[0047] Worktable 2: Surface flatness error ≤0.01mm. Positioning fixture 11 still adopts pressure adaptive positioning fixture. The proportional pressure regulating valve adjustment range is maintained at 0.1-0.5MPa. The diaphragm pressure sensor accuracy is ±0.001MPa. Due to the increase in the target hole diameter, the positioning fixture 11 is equipped with an auxiliary positioning stop to ensure that the positioning reference of the counterweight metal plate 3 is stable. Combining the characteristics of 304 stainless steel (hardness HRC20-25), the control unit calls the material-clamping pressure database to accurately adjust the clamping pressure to 0.35MPa. Through the closed-loop verification of the diaphragm pressure sensor, it is ensured that the deviation between the actual clamping pressure and the target pressure is ≤±0.01MPa. This not only prevents workpiece deformation caused by high pressure clamping, but also avoids workpiece displacement during large-diameter drilling, and eliminates static runout error caused by clamping deformation.

[0048] Rotary cutting mechanism: The drive motor 4 adopts a high-power servo motor with a speed range of 500-2000 r / min and an output power of 11kW, which meets the power requirements of large-diameter U-drilling; the transmission spindle 5 is supported by high-precision ball bearings with radial runout ≤0.005mm, enhancing spindle rigidity; the U-drill tool 6 is an indexable shallow hole drill (suitable for 70mm diameter holes), with 2 teeth on the center insert 62 and 4 teeth on the peripheral insert 63; the tool body 61 is made of 42CrMo material with a hardness of HRC40, and the insert mounting groove is locally hardened to HRC52; the center insert 62 has a rake angle of 10°, and the peripheral insert 63 has a rake angle of -1°. The inserts are coated with TiAlN with a coating thickness of 3μm and a hardness of HV3200; the repeatability of the tool body 61 and the inserts is ≤0.02mm. The tool body 61 is reinforced with reinforcing ribs to improve its resistance to deformation during large-diameter drilling, and has a built-in internal cooling channel to meet the requirements of center water outlet.

[0049] Tool centering compensation mechanism 10: The elastic centering sleeve 101 is made of 40Cr material and its size is adapted to the installation requirements of a 70mm diameter U-drill. There are 8 circumferentially distributed disc springs (model 80×35×0.8) between the inner hole and the transmission spindle 5 to enhance the elastic reset capability and better absorb radial offset; The displacement compensation sensor 102 still uses a laser displacement sensor with a detection accuracy of ±0.001mm and a sampling frequency of 10kHz. Adjusting the installation angle ensures accurate detection of the radial displacement of the large-diameter U-drill; The fine-tuning actuator 103 uses a piezoelectric ceramic actuator with a compensation accuracy of ≤0.002mm and a stroke range of ±0.2mm, which is adapted to the runout compensation requirements of the large-diameter U-drill.

[0050] Feed drive mechanism 7: adopts a high-power servo electric cylinder, with a feed speed range of 50-300mm / min, feed accuracy of ±0.01mm, and a maximum feed stroke of 100mm. The reduced feed speed is suitable for large-diameter drilling, reduces cutting impact, and avoids dynamic cutting force imbalance.

[0051] Counterweight balancing component 8: Adjustable eccentric counterweight component, including 4 sector-shaped counterweights (each weighing 1.0kg) and 1 eccentric adjustment disc, with an eccentricity adjustment range of 0-8mm. According to the U-drill rotation speed of 1000r / min, the eccentricity is adjusted to 4mm, which effectively balances the eccentric torque generated when the large-diameter U-drill rotates at high speed and suppresses vibration.

[0052] Cutting fluid supply system 9: The cutting fluid is an emulsion (cutting fluid to water ratio 1:15), and the flow rate of the delivery pump is 20L / min, which increases the flow rate to meet the cooling and lubrication requirements of large-diameter drilling; two nozzles are added, symmetrically aligned with the cutting contact area; the internal cooling channel of the U-drill tool 6 is enlarged, and the central water outlet flow rate is 8L / min; the dual filtration device 91 remains unchanged, with a primary magnetic filter with a filtration accuracy of 50μm and a secondary precision filter with a filtration accuracy of 5μm, to ensure the cleanliness of the cutting fluid and reduce the interference of impurities on large-diameter drilling.

[0053] Control unit: The PLC controller (model S7-1200) is used. The built-in vibration-speed-feed speed linkage adjustment algorithm module is adapted to the cutting characteristics of large-diameter U-drills and adjusts the parameter thresholds. The vibration sensor adopts a piezoelectric vibration sensor with a measurement range of 0-10g and an accuracy of ±0.01g. The spindle current sensor has a sampling accuracy of ±0.1A, which enhances the sensitivity of current signal detection and adapts to load changes during large-diameter drilling.

[0054] II. Adaptation of Drilling Method Implementation Steps Step S1: Workpiece positioning and clamping. A 10mm thick, 304 stainless steel counterweight plate 3 is placed on the positioning fixture 11 of the worktable 2, conforming to the auxiliary positioning block. The control unit, through an eddy current sensor integrated on the positioning fixture 11, detects the workpiece conductivity (approximately 1.4 × 10⁻⁶) in real time. 6 After confirming the material type (S / m), the optimal clamping pressure parameter (0.35MPa) corresponding to 304 stainless steel (large diameter hole machining) is called from the material-clamping pressure database, and an adjustment command is sent to the proportional pressure regulating valve. The proportional pressure regulating valve adjusts the air pressure of the clamping circuit to 0.35MPa, drives the clamping jaws to clamp the workpiece, the diaphragm pressure sensor collects the pressure signal in real time and feeds it back, and the control unit performs closed-loop verification to ensure that the deviation is ≤±0.01MPa, thus completing the positioning clamping and laying the foundation for static runout compensation.

[0055] Step S2: Trial cutting and self-tuning, performing a trial cut with conservative parameters: spindle speed 600 r / min (60% of the theoretical recommended value of 1000 r / min), feed rate 60 mm / min (50% of the theoretical recommended value of 120 r / min); the control unit automatically collects data such as spindle load current curve, vibration spectrum, and actual hole diameter deviation, generating the optimal target cutting current value of 15 A and the maximum allowable vibration spectral density threshold of 0.06 g. 2 •Hz, optimal speed-feed speed matching curve (speed 1000r / min, feed speed 120mm / min), and simultaneously calibrate the cutting force balance coefficient of the center tool 62 and the peripheral tool 63 to 1.3, adapting to the double-insert force characteristics of large-diameter drilling.

[0056] Step S3: Batch adaptation and call. The control unit calls the optimal parameters obtained from the trial cutting self-tuning, sets the U-drill rotation speed to 1000r / min and the feed speed to 120mm / min, taking into account both the accuracy and efficiency of large-diameter drilling.

[0057] Step S4: Rotary cutting pre-start, start drive motor 4, drive U drill to rotate at 1000 r / min under no load, turn on the cutting fluid supply system, turn on the water outlet in the center of the U drill internal cooling channel, and spray cutting fluid synchronously from two symmetrical nozzles to fully pre-cool and lubricate the cutting tool; at the same time, the tool centering compensation mechanism 10 is started, the displacement compensation sensor 102 detects the radial displacement of the U drill in real time, and the control unit drives the piezoelectric ceramic actuator to perform active compensation to eliminate static runout and make the rotation center of the U drill coincide with the theoretical hole center.

[0058] Step S5: Incremental feed cutting. Start the feed drive mechanism 7 and move downwards at a feed speed of 120 mm / min. Drilling begins after the U-shaped drill bit contacts the surface of the counterweight metal plate 3, while simultaneously executing the following control strategy: (1) Graded dynamic vibration threshold control: The cutting process is divided into the drilling stability zone (0≤h<1.5mm), the main drilling zone (1.5mm≤h<8.5mm), and the drill exit anti-breakage zone (8.5mm≤h≤10mm); combined with the characteristics of large-diameter drilling, the vibration threshold of the drilling zone is 0.03g. 2 ·Hz, main drilling zone 0.06g 2 ·Hz, 0.024g in the drilling zone 2 •Hz, the threshold decreases by 5% for every 100 holes machined, adapting to the cutting state after the cutting tool wears.

[0059] (2) Spindle load current feedforward-feedback composite regulation: The feedforward part is based on the target current curve I_target(h) to predict the load change of large diameter drilling and perform parameter pre-adjustment; The feedback part adopts incremental PID. When the spindle current deviates from 15A, the feed rate is adjusted first, with an adjustment range of ±30mm / min; The harmonic component of the current corresponding to the center cutting tool is monitored in real time. When the sideband energy exceeds 30% of the main frequency energy, the feed rate is reduced to 96mm / min and the rotation speed is increased to 1150r / min (increased by 15%) to improve the center chip breaking and balance the cutting force of the two cutting tools.

[0060] (3) Segmented feed + intermittent chip breaking strategy: Since the workpiece thickness is 10mm≥8mm, this strategy is used; combined with the characteristics of 70mm large diameter drilling, the feed length of each segment is 1.5mm. After each segment, the chip breaking action is performed: "pause feed for 0.15s → spindle instantaneous reverse for 0.08s (reverse speed 200r / min, which is 20% of the forward speed) → forward speed up for 0.15s"; at the beginning of each segment, the feed speed is modulated with a frequency of 70Hz and a base speed of 20% (24mm / min) to make the chips form C-shaped short chips with a length ≤2mm, so as to avoid the chips from wrapping around the large diameter U drill.

[0061] (4) Collaborative control: The tool centering compensation mechanism 10 continuously detects the radial displacement of the U-drill and compensates for the static runout caused by tool wear and spindle vibration during the cutting process in real time; the linkage adjustment algorithm module identifies abnormal cutting force of the center / peripheral blades through FFT spectrum analysis, dynamically adjusts the rotation speed and feed rate, suppresses dynamic cutting force fluctuations, and ensures the accuracy and stability of large-diameter drilling.

[0062] Step S6: Reset and retract the tool. When the feed rate reaches 10mm, the U-drill stays at the bottom of the hole for 0.4s. Continue to supply cutting fluid to flush the chips in the hole to prevent chip residue from scratching the hole wall. Then, retract the tool quickly at a retraction speed of 550mm / min to reduce vibration and tool wear during the retraction process.

[0063] Step S7: Hole position adjustment. Based on the distribution of the holes to be processed (hole spacing 50mm), control the worktable 2 to move to the next hole position. Repeat steps S4-S6 until all drilling operations are completed. Implementation effect

[0064] Actual measurements show that the counterweight metal sheet (70mm diameter hole) processed in this embodiment has a hole diameter deviation of 0.030mm, a hole wall roughness Ra=1.3μm, and a hole position deviation of 0.012mm; the single hole processing time is 4.5s, which is shorter than that of traditional large-diameter twist drills; the U-drill tool life reaches 6500 holes, which is longer than that of conventional large-diameter U-drills; the chip entanglement rate is reduced, the peak cutting force is reduced, and the occurrence rate of micro-cracks in the hole wall is reduced, fully meeting the processing accuracy and efficiency requirements of 70mm large-diameter holes, and adapting to the automated batch processing needs of large-size counterweight metal sheets. Example

[0065] This embodiment provides a device and method for drilling counterweight metal sheets. Based on embodiment 1, the device structure is upgraded and optimized to meet the batch processing requirements of multi-layer stacked counterweight metal sheets. Specifically, it can process 6 counterweight metal sheets at one time (2 processing units, with 3 counterweight metal sheets stacked in each unit), which greatly improves processing efficiency and ensures the consistency of processing accuracy of each layer of workpieces.

[0066] I. Adaptation and Adjustment of Device Structural Parameters Base 1 and overall layout optimization The base 1 is made of HT300 high-strength cast iron, and the overall size is adjusted to 2000mm×1200mm×800mm. Compared with Example 1, the cross-sectional size is further increased and a reinforcing rib structure (3 horizontal and 2 vertical) is added to improve the overall rigidity and vibration resistance, and to meet the vibration suppression requirements when the dual rotary cutting mechanisms are running synchronously at high speed.

[0067] Two sets of processing units are symmetrically arranged on the top of the machine base 1 along the length direction. Each set of processing units is independently equipped with a worktable 2, a positioning fixture 11, a rotary cutting mechanism and a feed drive mechanism 7. The distance between the two sets of processing units is 500mm to avoid mutual interference during processing, while reserving sufficient space for operation and maintenance.

[0068] Upgraded dual worktable 2 and positioning fixture 11 The worktable 2 adopts the precision grinding process, with a surface flatness error of ≤0.01mm. Each processing unit is equipped with one long strip worktable 2 with dimensions of 800mm×600mm×150mm. The two worktables 2 are arranged in parallel and slidably connected to the machine base 1. They can achieve independent displacement along the length direction through servo drive, adapting to the positioning adjustment of different groups of workpieces.

[0069] Positioning fixture 11 adopts a multi-layer synchronous pressure adaptive positioning fixture. Each processing unit's worktable 2 is equipped with 3 independent fixture positions for stacking 3 counterweight metal plates 3. Each fixture position includes: Pressure adaptive clamping assembly: Each clamping position is equipped with two sets of symmetrical upper and lower clamping jaws, which are adapted to clamping the upper, middle and lower layers of workpieces respectively. The proportional pressure regulating valve has an adjustment range of 0.1-0.8MPa, and the diaphragm pressure sensor has an accuracy of ±0.001MPa, which can independently adjust the clamping pressure of each layer.

[0070] Stacked positioning reference assembly: Each fixture position is equipped with 4 high-precision positioning pins (10mm in diameter, radial runout ≤0.003mm). 3 counterweight metal plates 3 cooperate with the positioning pins through positioning holes to achieve stacked positioning. The stacking gap is controlled to 0.1-0.2mm by limit blocks to ensure that the workpieces in each layer are in close contact without loosening.

[0071] For stacked workpieces made of 304 stainless steel (10mm thick), the control unit automatically matches the clamping pressure based on the material identification results: the clamping pressure of the upper and middle layer workpieces (which are easily affected by the extrusion of the lower layer) is adjusted to 0.3MPa, and the clamping pressure of the lower layer workpiece is adjusted to 0.35MPa. The thin-film pressure sensor collects the clamping pressure of each layer in real time and provides feedback, with the deviation controlled within ±0.01MPa. This avoids deformation of the stacked workpieces during clamping and prevents displacement and misalignment of the workpieces in each layer during dynamic cutting.

[0072] Dual-group rotary cutting mechanism configuration Each machining unit is equipped with one rotary cutting mechanism identical to that in Example 1, maintaining a unified overall structure for easy maintenance and parameter standardization. The specific core parameters are as follows: Drive motor 4: A 5.5kW high-power servo motor with a speed range of 500-2000r / min is adopted. The two sets of motors run synchronously with a torque output deviation of ≤±2%, ensuring the consistency of cutting parameters.

[0073] Transmission spindle 5: radial runout ≤0.005mm, parallelism error between the two sets of spindles ≤0.008mm, to avoid positional deviation during synchronous machining of the two sets of cutting mechanisms.

[0074] U-drill tool 6: Same as in Example 1, an indexable shallow hole drill suitable for 70mm diameter holes is selected, with 2 teeth for the center insert 62 and 4 teeth for the peripheral insert 63. The tool body 61 is made of 42CrMo material (HRC40), and the inserts are coated with TiAlN (thickness 3μm, HV3200) to ensure the machining accuracy of a single set of tools. At the same time, the life of the two sets of tools is synchronized through standardized design.

[0075] Tool centering compensation mechanism 10: The parameters are the same as in Example 1. The elastic centering sleeve 101 is equipped with 8 disc springs, the displacement compensation sensor 102 has a sampling frequency of 10kHz, and the fine-tuning actuator 103 has a compensation accuracy of ≤0.002mm and a stroke range of ±0.2mm, ensuring the static runout compensation effect of each stack of workpieces.

[0076] Dual-group feed drive mechanism 7 coordinated control Each processing unit is equipped with one servo electric cylinder feed drive mechanism 7, which adopts a dual-motor synchronous drive design, with a feed speed range of 50-300mm / min, a feed accuracy of ±0.01mm, and a maximum feed stroke of 100mm.

[0077] The two sets of feed drive mechanisms 7 are connected by a bus-type synchronous control module to achieve synchronous and precise control of feed speed and feed depth. The feed deviation is ≤ ±0.01mm, ensuring that the two sets of processing units complete the drilling, main drilling, and drilling exit actions at the same time, avoiding workpiece accuracy deviation caused by the lag of a single set of processing.

[0078] In response to the characteristics of layered workpieces, the feed drive mechanism 7 is equipped with a layered feed compensation module, which can finely adjust the feed speed of a single mechanism (fine adjustment range ≤ ±5%) according to the difference in cutting load of each layer of workpieces, adapt to the changes in cutting force of 3 stacked workpieces, and further improve the dynamic cutting force balance effect.

[0079] 8 Optimizations of Counterweight Balancing Components Each processing unit has an adjustable eccentric counterweight assembly 8 configured with the same rotary cutting mechanism as in Example 1, including 4 sector-shaped counterweights (each weighing 1.0 kg) and 1 eccentric adjustment disc, with an eccentricity adjustment range of 0-8 mm.

[0080] For the synchronous operation of the two sets of rotary cutting mechanisms, the control unit presets a synchronous adjustment model for the two sets of counterweights. Based on the rotation speed of the two sets of mechanisms (synchronous operation speed 1000r / min), it automatically adjusts the eccentricity to 4mm, while ensuring that the eccentricity directions of the two sets of counterweights are opposite, further offsetting the overall vibration, so that the overall vibration amplitude of the machine base 1 is ≤0.01g.

[0081] Upgraded cutting fluid supply system 9 The cutting fluid supply system 9 adopts a dual-path independent circulation system. Each machining unit is equipped with an independent cutting fluid tank, pump and nozzle. The pump flow rate is increased to 30L / min, and the internal cooling channel flow rate of the U-drill tool 6 is increased to 12L / min, which is suitable for the high flow rate cooling requirements of the two sets of tools.

[0082] The dual filtration device 91 has been upgraded to a parallel dual filtration device, with one filtration unit corresponding to the cutting fluid of each processing unit. The first-stage magnetic filter has a filtration accuracy of 50μm, and the second-stage precision filter has a filtration accuracy of 5μm, ensuring that the cleanliness of each cutting fluid reaches NAS8 level, while avoiding cross-contamination of impurities.

[0083] The number of nozzles has been increased to 4 per group, symmetrically aligned with the cutting area of ​​each processing unit, to achieve full coverage cooling and lubrication of the 3 stacked workpieces. The cutting fluid to water ratio is 1:15, which is suitable for the high-temperature heat dissipation requirements of large-diameter hole processing.

[0084] Control unit upgrade The control unit adopts the S7-1500 high-performance PLC controller, which improves the calculation speed and multi-tasking capability compared to the S7-1200. It has a built-in dual-group machining unit synchronous collaborative control module, layered cutting parameter adjustment module, and abnormal working condition linkage protection module. The specific functions are as follows: Synchronous and coordinated control module: realizes full-dimensional synchronous control of the rotation speed, feed rate, clamping pressure and cutting fluid supply of the two sets of machining units, improves the sampling frequency to 20kHz, and the control response time ≤10ms, ensuring the consistency of parameters for machining 6 workpieces.

[0085] Layered cutting parameter adjustment module: For each group of three stacked workpieces, the vibration signal and spindle load current signal of each layer are independently collected. The difference in cutting force of each layer is identified through spectrum analysis, and the single group feed rate (±5%) and rotation speed (±3%) are automatically fine-tuned to adapt to the force characteristics of the stacked workpiece.

[0086] Abnormal working condition linkage protection module: When any group of machining units experiences abnormalities such as static runout ≥0.01mm or vibration amplitude exceeding the threshold by 150%, the module immediately triggers synchronous emergency stop and tool retraction of both groups of machining units to prevent single-group abnormalities from affecting the overall machining process. At the same time, the abnormal data is recorded for easy traceability.

[0087] Vibration-Speed-Feed Speed ​​Linkage Adjustment Algorithm Module: Upgraded to a two-component layered adaptive algorithm, compatible with single-component and dual-component machining modes. For the force differences of multiple workpieces in layered machining, the fuzzy rules and spectrum analysis logic are optimized to improve the adaptability of dynamic cutting force balance.

[0088] II. Adaptation of Drilling Method Implementation Steps Step S1: Workpiece positioning and clamping The six 304 stainless steel counterweight metal plates 3 (10mm thick, 70mm diameter hole processing requirements) are divided into two groups of three, and each group of three plates is stacked and placed in the fixture position of the worktable 2 of the corresponding processing unit.

[0089] The control unit uses an eddy current sensor integrated into the fixture to detect the conductivity of each workpiece layer in real time (approximately 1.4 × 10⁻⁶). 6 After confirming the material type (S / m), call the layer stacking workpiece special material - clamping pressure database: upper and middle layer workpiece clamping pressure 0.3MPa, lower layer workpiece clamping pressure 0.35MPa.

[0090] The control unit sends clamping commands to the upper and lower symmetrical clamping jaws of each fixture position. The proportional pressure regulating valve precisely adjusts the pressure, and the diaphragm pressure sensor collects the clamping pressure of each layer in real time and feeds it back to the control unit for closed-loop verification. The deviation is controlled within ±0.01MPa, completing the positioning and clamping of 6 workpieces, ensuring that each layer of workpieces fits together without loosening, and avoiding clamping deformation and displacement misalignment in the layer stacking process from the source.

[0091] Step S2: Trial Cut Self-Adjustment For the double-layer superimposed working condition, a trial cut was performed with conservative parameters: the rotation speed of each U-drill was 600 r / min (60% of the theoretical recommended value of 1000 r / min), and the feed rate was 60 mm / min (50% of the theoretical recommended value of 120 r / min).

[0092] The control unit synchronously collects data such as spindle load current curves, vibration spectrum, and actual hole diameter deviation of each layer from two machining units, and generates optimal parameters specifically for layer stacking processing. Single-group rotation speed: 1000 r / min; Single-group feed rate: 120 mm / min; Cutting force balance coefficients for each layer: upper layer 1.3, middle layer 1.35, lower layer 1.4; Maximum permissible vibrational spectral density threshold: 0.06g 2 •Hz (uniform across all layers); The synchronization deviation threshold between the two sets of processing units is ≤0.01mm (feed depth) and ≤10r / min (rotation speed).

[0093] After the trial cut is completed, the control unit automatically stores the special parameters for layer overlay and binds the dual-group synchronous control logic to provide a precise benchmark for batch processing.

[0094] Step S3: Batch Adaptation and Invocation The control unit calls upon the layer-stacking parameters obtained from the trial cutting self-tuning to simultaneously set the parameters of the two processing units: Rotation speed: 1000 r / min (difference between the two groups ≤ 10 r / min); Feed rate: 120 mm / min (two sets of deviation ≤ 0.01 mm); Clamping pressure for each layer: 0.3MPa for the upper layer, 0.35MPa for the middle layer, and 0.4MPa for the lower layer (fine-tuning to adapt to the stress of the stacked layers).

[0095] Step S4: Rotary cutting pre-start The control unit synchronously starts two sets of drive motors 4, driving the U-drill to rotate at 1000 r / min under no-load. The speed deviation between the two sets is monitored in real time, and the system automatically adjusts to the synchronous state when the deviation exceeds the limit.

[0096] Turn on the dual-path cutting fluid supply system 9, activate the center outlet of the internal cooling channel of the two sets of U-drill tools 6, and spray cutting fluid synchronously from 4 symmetrical nozzles to pre-cool and lubricate the cutting tools of the 6 workpieces.

[0097] The tool centering compensation mechanism 10 of the two processing units starts synchronously, the displacement compensation sensor 102 detects the radial displacement of the U-drill in real time, the control unit drives the piezoelectric ceramic actuator to perform active compensation, and corrects the deviation between the rotation center of each U-drill and the theoretical hole center to ≤0.003mm, thus completing the initial static runout calibration of the layer stacking process.

[0098] Step S5: Incremental feed cutting The dual-group feed drive mechanism 7 is activated, moving synchronously downwards at a feed speed of 120 mm / min. The feed deviation between the two groups is ≤0.01 mm. Drilling begins after the U-drill insert contacts the surface of the three stacked counterweight metal sheets 3 in each group, and the following layered collaborative control strategy is executed: (1) Graded dynamic vibration threshold control (layered adaptation) For each group of three stacked workpieces, the following zones are defined: a drilling stability zone (0≤h<1.5mm), a main drilling zone (1.5mm≤h<8.5mm), and a drill exit anti-breakage zone (8.5mm≤h≤10mm). Vibration thresholds for each layer are differentiated:

[0099] The control unit collects vibration data of each layer in real time. When the threshold of any layer exceeds the limit, the feed speed of the corresponding layer is immediately finely adjusted (±5%), and the static yaw compensation is adjusted in conjunction with the control unit.

[0100] (2) Spindle load current feedforward-feedback composite regulation (layered independent) Feedforward section: Based on the target current curves I_target(h) of each layer (15A for the upper layer, 15.5A for the middle layer, and 16A for the lower layer) obtained by trial cutting self-tuning, the changes in the stacked cutting load are predicted in advance, and the parameters are pre-adjusted.

[0101] Feedback section: Incremental PID is adopted, based on the deviation between the actual value and the target value of the spindle load current of each layer, the single feed speed is adjusted first (adjustment range ±30mm / min), and the speed is finely adjusted (adjustment range ±15r / min).

[0102] Dual-blade force balance adjustment: The control unit monitors the current harmonic component corresponding to the center blade of each U-drill individually. When the sideband energy exceeds the main frequency energy by 30%, the feed speed of the corresponding group is reduced to 96mm / min, and the rotation speed is finely adjusted to 1150r / min (increased by 15%) to improve chip breaking of the center blade and balance the cutting force difference of each layer of dual blades in the stacking process.

[0103] (3) Segmented feed + intermittent chip breaking strategy (general for stacked layers) Since the thickness of each workpiece is ≥8mm (10mm), this strategy is adopted. The feed length of each group is 1.5mm. After each segment, the following is executed: "Pause feed for 0.15s → Spindle instantaneous reverse for 0.08s (reverse speed 200r / min, which is 20% of the forward speed) → forward speed up for 0.15s". At the same time, at the beginning of each segment, the feed speed is modulated with a frequency of 70Hz and 20% of the base speed (24mm / min) to ensure that the chips of the three stacked workpieces are all C-shaped short chips (length ≤2mm), avoiding chip entanglement and chip jamming between layers, and reducing the peak cutting force.

[0104] (4) Coordinated control of static runout and dynamic cutting force balance (two-component layered) This is the core control link in the layered machining process. Through the collaborative mechanism of "dual-group synchronous calibration + layered independent compensation", the consistency of machining accuracy of the six workpieces is guaranteed. The details are as follows: Synchronous data acquisition: The control unit synchronously acquires displacement compensation signals, vibration signals, and spindle current signals from two sets of processing units at a sampling frequency of 20kHz, realizing real-time data fusion of 6 workpieces with a data transmission delay of ≤5ms.

[0105] Pre-cutting collaborative calibration: During the pre-start stage of rotary cutting, the two sets of tool centering compensation mechanisms synchronously complete the static runout calibration with a deviation of ≤0.003mm; the linkage adjustment algorithm module presets the initial dynamic control threshold to ensure that the dynamic cutting forces of the two sets during entry are quickly synchronized and stable.

[0106] Layered and coordinated adjustment of the cutting process: Static runout compensation: The displacement compensation sensor continuously detects the radial displacement of each group of U-drills. When the runout of any layer exceeds 0.005mm, the control unit will first trigger the corresponding fine-tuning actuator of that layer to quickly correct the runout. At the same time, the abnormal runout signal is fed back to the linkage adjustment algorithm module to analyze the cause of the abnormality (such as tool wear, workpiece displacement) and adjust the cutting parameters of that group synchronously.

[0107] Dynamic cutting force balance: The linkage adjustment algorithm module identifies the abnormal types of cutting force of each layer of dual blades through FFT spectrum analysis, and adjusts the feed rate and rotation speed of each layer differently. For example, when the wear of the middle layer blade causes the vibration to exceed the limit, the feed rate of the corresponding middle layer group is reduced by 5% and the rotation speed is finely adjusted by 3% to suppress dynamic fluctuations from the source and avoid repeated swaying.

[0108] Dual-group coordinated synchronization: The control signals of the two processing units are synchronized in real time. When one set of parameters is adjusted, the other set automatically performs the same adjustment, ensuring the consistency of the cutting state of the two processing units and avoiding the accuracy deviation of the six workpieces caused by the lag or advance of the single processing unit.

[0109] Collaborative protection for abnormal working conditions: When any group or layer experiences static runout ≥0.01mm, vibration amplitude exceeding the threshold by 150%, or abnormal surge in spindle current, the control unit immediately triggers synchronous emergency stop and tool retraction of the two machining units, while recording the abnormal location, time, and parameter data for subsequent troubleshooting.

[0110] Step S6: Reset and retract the tool When the feed rate of both machining units reaches 10mm, the control unit controls the two U-drills to stay at the bottom of the hole for 0.4s, and continues to supply cutting fluid to flush the chips inside the holes of the 6 workpieces. Then, they withdraw synchronously at a retraction speed of 550mm / min. During the retraction process, the speed deviation between the two sets is ≤±10mm / min, which reduces the impact of retraction vibration on the hole wall and ensures the surface roughness of the hole.

[0111] Step S7: Hole Position Adjustment The worktables of the two processing units move synchronously to the next hole (hole spacing 50mm), and the positional deviation between the two worktables is kept ≤0.01mm during the movement.

[0112] Repeat steps S4-S6 to complete the machining of the next hole in the 6 workpieces, until all holes in each group of 3 stacked workpieces are machined. Implementation effect

[0113] Actual measurements showed that the six 304 stainless steel counterweight metal plates 3 (70mm diameter holes) processed in one go in this embodiment met all the accuracy requirements.

[0114] Example 3 This embodiment provides a device and method for drilling holes in a counterweight metal sheet, used to process a counterweight metal sheet 3 with a thickness of 10mm and made of 304 stainless steel (tensile strength 715MPa), with a target hole diameter of 10mm. Specific implementation details are as follows: I. Device Structural Parameters Base 1: Made of HT200 cast iron, with dimensions of 800mm×600mm×500mm, it is rigid and can effectively suppress equipment vibration.

[0115] Worktable 2: Surface flatness error ≤0.01mm. Positioning fixture 11 adopts pressure adaptive positioning fixture, proportional pressure regulating valve adjustment range 0.1-0.5MPa, diaphragm pressure sensor accuracy ±0.001MPa. Based on 304 stainless steel material (hardness HRC20-25, belonging to medium hardness material, not easy to deform but requires stable positioning), the control unit calls the preset material-clamping pressure database and sends a control signal to the proportional pressure regulating valve to accurately adjust the clamping pressure to 0.3MPa. At the same time, the diaphragm pressure sensor collects the clamping pressure signal in real time and feeds it back to the control unit for closed-loop verification to ensure that the deviation between the actual clamping pressure and the target pressure is controlled within ±0.01MPa. This ensures that the workpiece is firmly positioned and avoids workpiece deformation caused by high pressure clamping, thereby eliminating the static runout error of the U-drill caused by clamping deformation and providing a stable workpiece reference for the static runout compensation work of the subsequent tool centering compensation mechanism 10.

[0116] Rotary cutting mechanism: The drive motor 4 is a servo motor with a speed range of 800-4000 r / min and an output power of 5.5 kW; the radial runout of the transmission spindle 5 is ≤0.005 mm; the U-drill tool 6 is an indexable shallow hole drill with a drilling diameter of 10 mm, the center insert 62 has 1 tooth and the peripheral insert 63 has 2 teeth; the tool body 61 is made of 42CrMo material with a hardness of HRC40, and the insert mounting groove is locally hardened to HRC52; the center insert 62 has a rake angle of 10° and the peripheral insert 63 has a rake angle of -1°. The inserts are coated with TiAlN with a coating thickness of 3 μm and a hardness of HV3200; the repeatability of the tool body 61 and the inserts is ≤0.02 mm.

[0117] Tool centering compensation mechanism 10: The elastic centering sleeve 101 is made of 40Cr material, and there are 6 circumferentially distributed disc springs (model 60×25×0.5) between the inner hole and the transmission spindle 5; the displacement compensation sensor 102 adopts a laser displacement sensor with a detection accuracy of ±0.001mm and a sampling frequency of 10kHz; the fine-tuning actuator 103 adopts a piezoelectric ceramic actuator with a compensation accuracy of ≤0.002mm and a stroke range of ±0.1mm.

[0118] Feed drive mechanism 7: adopts servo electric cylinder, feed speed range 100-800mm / min, feed accuracy ±0.01mm, maximum feed stroke 100mm.

[0119] Counterweight balancing component 8: Adjustable eccentric counterweight component, including 2 sector counterweights (each weighing 0.5kg) and 1 eccentric adjustment disc, with an eccentricity adjustment range of 0-5mm. According to the U-drill rotation speed of 2000r / min, the eccentricity is adjusted to 2mm to balance the eccentric torque.

[0120] Cutting fluid supply system 9: The cutting fluid is an emulsion (cutting fluid to water ratio 1:20), and the pump flow rate is 10L / min; the nozzle is aimed at the cutting contact area, the U-drill tool 6 is equipped with an internal cooling channel, and the central water outlet flow rate is 3L / min; the dual filtration device 91 has a primary magnetic filter with a filtration accuracy of 50μm and a secondary precision filter with a filtration accuracy of 5μm, and the cutting fluid cleanliness reaches NAS8 level.

[0121] Control unit: PLC controller (model S7-1200) with built-in vibration-speed-feed speed linkage adjustment algorithm module; vibration sensor adopts piezoelectric vibration sensor with measurement range of 0-10g and accuracy of ±0.01g; spindle current sensor sampling accuracy of ±0.1A.

[0122] II. Drilling Method Implementation Steps Step S1: Workpiece positioning and clamping. A 10mm thick counterweight metal sheet 3 made of 304 stainless steel is placed on the positioning fixture 11 of the worktable 2. The control unit, based on the material characteristics of 304 stainless steel (hardness HRC20-25, conductivity approximately 1.4×10^6 S / m), completes material identification and adaptive adjustment of the clamping pressure. The control unit uses an eddy current sensor integrated on the positioning fixture 11 to detect the workpiece's conductivity in real time, compares it with the preset conductivity parameters for 304 stainless steel, confirms the material type, and then calls the optimal clamping pressure parameter (0.3MPa) corresponding to 304 stainless steel from the material-clamping pressure database, sending an adjustment command to the proportional pressure regulating valve. The proportional pressure regulating valve receives the command. After receiving the command, the air pressure in the clamping circuit is adjusted to 0.3MPa, driving the clamping jaws of the positioning fixture 11 to clamp the workpiece. At the same time, the diaphragm pressure sensor collects the clamping pressure signal in real time and feeds the signal back to the control unit. The control unit compares the actual pressure (0.3MPa) with the target pressure (0.3MPa), and after confirming that there is no deviation (deviation ≤ ±0.01MPa), the clamping action is completed. The entire process avoids the 304 stainless steel counterweight metal sheet 3 from being deformed due to excessive clamping pressure or loosening due to insufficient pressure by using precise material identification and pressure closed-loop adjustment. This eliminates the static runout error of the U-drill caused by clamping deformation from the source, ensuring that the subsequent static runout compensation mechanism 10 can function accurately.

[0123] Step S2: Trial cutting and self-tuning, performing a trial cut with conservative parameters: spindle speed 1200 r / min (60% of the theoretical recommended value of 2000 r / min), feed rate 200 mm / min (50% of the theoretical recommended value of 400 r / min); the control unit automatically collects data such as spindle load current curve, vibration spectrum, and actual hole diameter deviation to generate the optimal target cutting current value of 8A and the maximum allowable vibration spectral density threshold of 0.05g. 2·Hz, the optimal speed-feed speed matching curve (speed 2000r / min, feed speed 400mm / min), and the cutting force balance coefficient of the center insert 62 and the peripheral insert 63 is calibrated to 1.2.

[0124] Step S3: Batch adaptation and call. The control unit calls the optimal parameters obtained from the trial cutting self-tuning, and sets the U-drill speed to 2000r / min and the feed speed to 400mm / min.

[0125] Step S4: Rotary cutting pre-start, start drive motor 4, drive U drill to rotate at 2000 r / min under no load, turn on cutting fluid supply system 9, activate water outlet in center of U drill internal cooling channel to pre-cool and lubricate the cutting tool; at the same time, tool centering compensation mechanism 10 is started, displacement compensation sensor 102 detects radial displacement of U drill in real time, control unit drives piezoelectric ceramic actuator to perform active compensation, eliminate static runout, and make U drill rotation center coincide with theoretical hole center.

[0126] Step S5: Incremental feed cutting. Start the feed drive mechanism 7 and move downwards at a feed speed of 400 mm / min. After the U-shaped drill bit contacts the surface of the counterweight metal plate 3, drilling begins. The following control strategy is executed: (1) Graded dynamic vibration threshold control: The cutting process is divided into the drilling stability zone (0≤h<1.5mm), the main drilling zone (1.5mm≤h<8.5mm), and the drilling anti-breakage zone (8.5mm≤h≤10mm); the vibration threshold of the drilling zone is 0.025g. 2 ·Hz, main drilling zone 0.05g 2 ·Hz, 0.02g in the drilling zone 2 •Hz, the threshold decreases by 5% for every 100 holes processed.

[0127] (2) Spindle load current feedforward-feedback composite regulation: The feedforward part is based on the target current curve Itarget(h), and the feedback part adopts incremental PID. When the spindle current deviates from 8A, the feed speed is adjusted first, with an adjustment range of ±50mm / min. The harmonic component of the current corresponding to the center cutting tool 62 is monitored in real time. When the sideband energy exceeds 30% of the main frequency energy, the feed speed is reduced to 320mm / min and the rotation speed is increased to 2300r / min (increased by 15%) to improve the center chip breaking.

[0128] (3) Segmented feed + intermittent chip breaking strategy: Since the workpiece thickness is 10mm≥8mm, this strategy is activated; the feed length of each segment is 1.5mm. After each segment, the chip breaking action is performed: "pause feed for 0.1s → spindle instantaneous reverse for 0.05s (reverse speed 400r / min) → forward rotation acceleration for 0.1s"; at the beginning of each segment, the feed speed is modulated with 80Hz frequency and 20% base speed (80mm / min) to make the chips form C-shaped short chips with a length ≤2mm.

[0129] (4) Collaborative control: The tool centering compensation mechanism 10 continuously detects the radial displacement of the U-drill and compensates for static runout in real time; the linkage adjustment algorithm module identifies abnormal cutting force of the center / peripheral blades through FFT spectrum analysis, dynamically adjusts parameters, and suppresses dynamic cutting force fluctuations.

[0130] Step S6: Reset and retract the tool. When the feed rate reaches 10mm, the U-drill stays at the bottom of the hole for 0.3s. Continue to supply cutting fluid to flush the chips in the hole, and then quickly retract the tool at a retraction speed of 600mm / min.

[0131] Step S7: Hole position adjustment. Control the worktable to move to the next hole position (hole spacing 20mm). Repeat steps S4-S6 until 100 holes are machined. Implementation effect

[0132] Actual measurements show that the counterweight metal sheet 3 processed in this embodiment has a hole diameter deviation of 0.015mm, a hole wall roughness Ra=1.2μm, and a hole position deviation of 0.01mm; the single hole processing time is 0.8s, which is shorter than that of traditional twist drills; the U-drill tool life reaches 8000 holes, which is longer than that of conventional U-drills; the chip entanglement rate is reduced, the peak cutting force is reduced, and the occurrence rate of micro-cracks in the hole wall is reduced, which fully meets the processing requirements of high-end counterweight metal sheets and realizes automated processing with high precision, high efficiency, and long life.

[0133] The above description is only a preferred embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any equivalent substitutions or modifications made by those skilled in the art within the scope of the technology disclosed in the present invention, based on the technical solution and inventive concept of the present invention, should be covered within the scope of protection of the present invention.

Claims

1. A device for drilling holes in a counterweight metal sheet, comprising: The base (1) is used to support and fix the various functional components; The workbench (2) is located above the machine base (1) and is used to place the counterweight metal sheet to be processed; Its characteristic is that it further includes: The rotary cutting mechanism includes a drive motor (4), a transmission spindle (5), a tool centering compensation mechanism (10), and a U-drill (6). The output end of the drive motor (4) is connected to the transmission spindle (5). The U-drill (6) is fixedly installed at the lower end of the transmission spindle (5). The U-drill (6) is a hole drill with indexable inserts. Its inserts include a center insert and peripheral inserts. The drilling diameter matches the target diameter of the hole to be processed. The tool centering compensation mechanism (10) is used to actively compensate the radial position of the transmission spindle (5) so that the rotation center of the U-drill (6) always coincides with the theoretical hole center. The feed drive mechanism (7) is located between the machine base (1) and the rotary cutting mechanism, and is used to drive the rotary cutting mechanism to make vertical reciprocating feed motion relative to the worktable (2); The counterweight balancing assembly (8) is fixedly installed on the upper part of the transmission spindle (5) or on the opposite side of the drive motor (4) to balance the eccentric torque and unbalanced vibration generated by the rotary cutting mechanism during high-speed rotation and feeding. The cutting fluid supply system (9) includes a cutting fluid tank, a pump and a nozzle, wherein the nozzle is aligned with the cutting contact area between the U-drill (6) and the counterweight metal sheet through the inside of the drill rod; The control unit is electrically connected to the drive motor (4), the feed drive mechanism (7), and the fluid pump, respectively, and is used to control the rotation speed, feed speed and cutting fluid supply of the rotary cutting mechanism.

2. The apparatus of claim 1, wherein, The tool centering compensation mechanism (10) includes an elastic centering sleeve (101) and a displacement compensation sensor (102). The elastic centering sleeve (101) is sleeved on the lower end of the transmission spindle (5) and located above the U-drill tool (6). The inner hole of the elastic centering sleeve (101) and the transmission spindle (5) are provided with circumferentially distributed micro elastic elements, which are used to automatically absorb the radial displacement generated by the tool when rotating at high speed and under cutting force. The displacement compensation sensor (102) is set on the outer periphery of the elastic centering sleeve (101) and is used to detect the radial displacement of the U-drill tool (6) in real time and feed it back to the control unit. According to the feedback signal of the displacement compensation sensor (102), the control unit drives the fine-tuning actuator (103) set on the mounting base to actively compensate the radial position of the transmission spindle (5), so that the rotation center of the U-drill tool (6) always coincides with the theoretical hole center.

3. The apparatus of claim 1, wherein, The U-drill tool (6) adopts a combination of a tool body with a gradient hardness composite structure and an indexable insert. The center insert adopts a positive rake angle design with a rake angle of 8°-12°, and the peripheral insert adopts a negative rake angle design with a rake angle of -3°-0°.

4. The apparatus of claim 1, wherein, The counterweight balancing component (8) is an adjustable eccentric counterweight component, including at least two sector-shaped counterweight blocks and an eccentric adjustment disc, which can steplessly adjust the magnitude and direction of the eccentricity to help suppress the vibration of the rotary cutting mechanism.

5. The apparatus of claim 1, wherein, The workbench (2) is provided with a positioning fixture (11), which is a pressure adaptive positioning fixture, including a proportional pressure regulating valve and a diaphragm pressure sensor. The control unit automatically adjusts the clamping pressure according to the workpiece material.

6. The apparatus of claim 1, wherein, The control unit has a built-in vibration-rotation speed-feed speed linkage adjustment algorithm module. This algorithm module takes the real-time vibration amplitude and frequency, spindle load current, and current feed depth as inputs from the vibration sensor, and the rotational speed correction and feed speed correction as outputs. It achieves dynamic parameter matching based on fuzzy PID or model predictive control. By analyzing the fluctuation spectrum of the spindle current, it identifies unstable cutting of the center insert or wear of the peripheral inserts. It performs spectrum analysis and adjustment to address the imbalance of cutting forces between the center insert and the peripheral inserts of the U-drill, thereby suppressing tool vibration.

7. A method of punching a counterweight metal sheet using the apparatus according to any one of claims 1 to 6, characterized in that, Includes the following steps: Step S1: Positioning and clamping the workpiece, placing the counterweight metal sheet to be processed on the worktable (2). Step S2: Trial Cutting Self-Tuning. For each batch of counterweight metal sheets or after material change, a trial cut is performed with conservative parameters. The control unit automatically collects the spindle load current curve, vibration spectrum, and actual hole diameter deviation data. Through the self-tuning algorithm, it generates the optimal target cutting current value, the maximum allowable vibration spectral density threshold, and the optimal speed-feed speed matching curve. At the same time, it automatically calibrates the cutting force balance coefficient of the center insert and the peripheral inserts, providing reference data for static runout compensation and dynamic cutting force balance adjustment. Step S3: Batch adaptation call, the control unit calls the optimal machining parameters stored in step S2 to determine the rotation speed and feed rate of the U-drill tool (6). The rotation speed setting range of the U-drill is 800-4000 r / min, and the feed rate setting range is 100-800 mm / min. Step S4: Rotary cutting pre-start, start the drive motor (4) to drive the U-drill tool (6) to rotate at the set speed under no-load, and at the same time turn on the cutting fluid supply system (9); at this time, the tool centering compensation mechanism (10) is started, the displacement compensation sensor (102) detects the radial displacement of the U-drill tool (6) in real time, and the control unit drives the fine-tuning actuator (103) to perform active compensation to eliminate the static sway under no-load conditions; Step S5: Progressive feed cutting, start the feed drive mechanism (7), drive the rotary cutting mechanism to move downward at the set feed speed, after the U-drill tool (6) contacts the surface of the counterweight metal sheet, the material is removed by rotary drilling to form a circular through hole; during this process, the control unit synchronously executes the following control strategy: (1) Graded dynamic vibration threshold control: Based on the characteristics of U-drilling, graded dynamic vibration threshold control is implemented for the cutting process; (2) Spindle load current feedforward-feedback composite regulation: The feedforward part is based on the target current curve obtained by trial cutting self-tuning; the feedback part adopts incremental PID, which mainly adjusts the feed speed and secondarily adjusts the rotation speed; the control unit monitors the current harmonic component corresponding to the center blade separately. When the cutting force of the center blade is found to be abnormally increased, the feed speed is reduced first and the rotation speed is appropriately increased to improve the chip breaking of the center blade and assist in balancing the cutting force of the two blades. (3) Segmented feed + intermittent chip breaking strategy: Divide the feed stroke into several segments, each segment length Lseg=min(1.5mm,0.25H); after each segment, perform the chip breaking action of "pause feed for 0.1s → spindle instantaneous reverse for 0.05s → forward rotation and acceleration for 0.1s", using the chip shearing force during reverse rotation to forcibly break the ribbon-shaped chips; at the same time, at the beginning of each segment, the feed speed is modulated with a sine wave to make the chips form C-shaped or spiral short chips; (4) Static runout and dynamic cutting force balance coordinated control: The tool centering compensation mechanism (10) works continuously to detect the radial displacement of the U-drill tool (6) in real time, eliminating static runout caused by tool wear, spindle vibration and other factors during the cutting process; the vibration-speed-feed speed linkage adjustment algorithm module runs synchronously, identifies abnormal cutting force of the double blade through spectrum analysis, dynamically adjusts the speed and feed speed, suppresses dynamic cutting force fluctuations, and the two work together to ensure drilling accuracy and tool life; Step S6: Reset and retraction. When the feed rate reaches the workpiece thickness, the control unit controls the U-drill tool (6) to stay at the bottom of the hole and continues to supply cutting fluid to flush the chips in the hole. Then, it quickly retracts at a retraction speed of ≥500mm / min. Step S7: Hole position adjustment. According to the distribution of the holes to be processed, control the worktable (2) or the rotary cutting mechanism to move to the next hole position, and repeat steps S4-S6 until all drilling operations are completed.

8. The method of claim 7, wherein, In the segmented feed + intermittent chip breaking strategy, after each feed of 1.5mm or 0.25 times the workpiece thickness, the feed is paused for 0.1s, the spindle is instantaneously reversed for 0.05s, and then forward-rotated and accelerated for 0.1s. At the same time, the feed speed is modulated at a frequency of 60-120Hz and an amplitude of 15%-25% at the beginning of each segment.

9. The method of claim 7, wherein, The graded dynamic vibration threshold control divides the cutting process into the drilling stability zone, the main drilling zone, and the drilling anti-collapse zone, and adopts the optimal thresholds of 0.5 times, 1.0 times, and 0.4 times, respectively.

10. The method of claim 7, wherein, In the spindle load current feedforward-feedback composite regulation, the control unit monitors the current harmonic component corresponding to the center blade separately. When the cutting force of the center blade increases abnormally, the feed rate is reduced first and the rotational speed is increased by 10%-15%.

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