Segmented drilling method for wire needle jig

Abstract

The application discloses a segmented drilling method for a wire needle jig, and relates to the field of precision machining. The segmented drilling method for the wire needle jig is used for micro-hole drilling of a PCB with a large depth-diameter ratio. According to the drilling characteristics of different depths, a segmented operation scheme is designed, and the scheme sequentially includes a positioning stage, an efficient chip removal stage and an outlet finishing stage. Different drilling strategies are executed in different stages, and the rotational speed, the feed rate and the single feed depth are accurately controlled. In this way, an accurate guide hole can be formed on the plate material in the initial stage, continuous and smooth drilling can be realized on the plate material in the middle stage, and the edge collapse of the hole outlet can be effectively avoided in the final stage. In the machining process, the machining parameters are dynamically adjusted by monitoring the load. Compared with the fixed machining strategy, the machining efficiency can be effectively improved, the plate material failure rate can be reduced, and the service life of the drill bit can be prolonged.

Description

Technical Field

[0001] This invention relates to the field of precision machining technology, specifically to a method for segmented drilling using a needle-and-thread fixture. Background Technology

[0002] In the manufacturing of online needle fixtures, it is necessary to drill a large number of microholes with extremely high depth-to-diameter ratios (e.g., a diameter of 0.05 mm, a depth of 0.8 mm, and a depth-to-diameter ratio of 16:1). To prevent the micro-drill bit (drill tip) from breaking, to ensure chip removal, and to guarantee hole position accuracy, the industry generally adopts the "equal-parameter fully segmented drilling" technology. The specific solution of this existing technology is to use a constant and very conservative single drilling depth (e.g., 0.01 mm), rotation speed, and feed rate for the entire drilling depth (Z-axis). For example, drilling a hole 0.8 mm deep requires repeating the "drill down-retract chip removal" cycle 80 times.

[0003] Because the most conservative parameters were used at all depths, the number of cycles in the entire drilling process was too high, resulting in excessively long processing time per hole and severely limiting production efficiency; as the background information states, only 10 holes could be processed per minute.

[0004] The dynamic changes in the drilling process are not considered: This technology treats the drilling process as a static process and ignores the significant changes in the mechanical state of the drill bit (such as rigidity, chip removal resistance, and heat dissipation conditions) at different drilling depths. When the drilling depth is shallow, the drill bit has sufficient rigidity and the chip removal path is short. More aggressive parameters could be used, but the existing technology fails to take advantage of this optimization space.

[0005] Uneven drill bit wear: Constant parameters may cause the drill bit to work under certain unsuitable conditions, resulting in abnormal wear, which may actually affect the life of the drill bit.

[0006] Based on the above-mentioned shortcomings, this application proposes a segmented drilling method for a needle-and-thread jig, which intelligently and dynamically allocates drilling parameters according to the dynamic mechanical characteristics of the drilling process, thereby significantly improving processing efficiency while ensuring the quality of micro-hole processing. Summary of the Invention

[0007] To address the shortcomings of existing technologies, this invention provides a segmented drilling method using a needle-and-thread fixture, which solves the problems mentioned in the background technology, such as failure to consider dynamic changes in the drilling process, uneven drill wear, and slow processing speed.

[0008] To achieve the above objectives, the present invention provides a method for segmented drilling using a thread needle fixture, comprising the following steps:

[0009] S1. Establish a "parameter-material-pore size" mapping database;

[0010] S2. Select the drilling scheme with the corresponding number of segments based on the depth-to-diameter ratio of the drilled hole;

[0011] S3. Call the mapping database to configure the feed parameters to execute the drilling plan;

[0012] S4. Real-time monitoring of drill bit load, and dynamic adjustment of feed parameters based on load threshold;

[0013] S5. Establish an early warning and protection mechanism to perform rollback and shutdown protection when overload abnormalities occur;

[0014] in;

[0015] In step S2, the drilling scheme adopts a segmented drilling execution strategy, wherein the segments are L1, L2, ... Ln, and the value of n is proportional to the depth-to-diameter ratio of the hole. L1 adopts a slow feed strategy to ensure that the drill bit can feed steadily and form a preset hole on the surface of the plate. L2 to Ln-1 adopt a fast feed strategy based on the dynamic adjustment in S4 to ensure that the hole depth is advanced quickly. Ln adopts a low feed strategy to avoid edge chipping at the end of the hole.

[0016] Preferably, in the "parameter-material-aperture" mapping database, the parameters include rotational speed Vr, feed rate Vh, and single-pass depth of cut Ho; the material represents the plate material M; and the aperture includes hole depth H and diameter D. By establishing the corresponding rotational speed Vr, feed rate Vh, and single-pass depth of cut Ho mapping data table according to the hole depth and diameter relationship corresponding to different plate materials, in use, by inputting material and aperture data, the corresponding execution parameters are automatically exported to execute the drilling scheme in step S3.

[0017] Preferably, in the drilling scheme, L1 is the positioning stage, and the minimum extension of the drill bit in the positioning stage is Smin, so that the torsional resistance Tn of the drill bit reaches the maximum value; L1 adopts a high rotation speed and low feed rate strategy, and the single feed depth is ≤0.1mm, so that a precise guide hole is formed on the plate.

[0018] L2 to Ln-1 is the high-efficiency chip removal stage. The high-efficiency chip removal stage adopts a single feed depth scheme that is higher than that of the positioning stage, and at the same time adopts a low speed and fast feed scheme to form a continuous and smooth drilling.

[0019] Ln represents the exit finishing stage, which employs a low drilling speed and low feed rate strategy, with a single feed depth ≤ 0.1 mm.

[0020] Preferably, in step S3, the load current change of the drill bit spindle is monitored in real time by a spindle load current sensor, the drilling resistance of the drill bit is determined based on the load current change, and corresponding load thresholds Imax and Imin are designed, and differentiated dynamic adjustment schemes are executed according to different drilling stages.

[0021] Preferably, the dynamic adjustment scheme includes:

[0022] During the positioning stage, if the load current is detected to be greater than Imax, it indicates that the hardness of the plate material is greater than that of the preset plate material. At this time, the rotation speed can be increased while the feed speed is reduced.

[0023] If the load current is detected to be greater than Imax during the high-efficiency chip removal stage and the exit finishing stage, it indicates that chip blockage has occurred inside the borehole. At this time, the drill bit is controlled to retract to remove the chips.

[0024] If the load current is less than 1 min during the entire drilling process, it indicates that the drill bit is worn and needs to be replaced.

[0025] Preferably, in the high-efficiency chip removal stage, when the monitored load current ∈ [Imin, Imax], from L2 to Ln-1, the drill bit speed gradually increases with the increase of feed depth, while the single feed amount decreases; the feed rate decreases.

[0026] Preferably, the number of stages n in the drilling scheme is greater than or equal to 2. By establishing a maximum threshold Dmax for diameter D in the mapping database, if the diameter of the currently drilled hole is greater than Dmax, the drill bit diameter is large, and n=2. A two-stage drilling method is adopted, in which the high-efficiency chip removal stage L2 and the exit finishing stage are combined to form a high-efficiency drilling stage, and the same dynamic adjustment scheme as the high-efficiency chip removal stage L2 is adopted in the high-efficiency drilling stage.

[0027] Preferably, in step S3, the drill bit load monitoring also includes temperature monitoring. When dealing with different drilling materials and corresponding drill bit materials, the temperature at the drill bit hole is captured in real time by an infrared temperature sensor. By setting corresponding temperature thresholds Tmax for drill bits of different materials, when the temperature at the drill hole reaches Tmax, the drill bit speed and feed rate are actively reduced. At the same time, for heat-sensitive plates, the machine is shut down for protection when the temperature reaches Tmax.

[0028] Preferably, during the finishing stage at the exit, by reserving an exit protection section, when the distance H between the drilling depth and the bottom of the plate is ≤1mm, a "pecking drill" method is adopted, and the drill is immediately retracted after each advance, with the single advance amount being greater than the retraction amount by 0.1mm, thereby achieving downward advancement at a rate of 0.1mm.

[0029] Preferably, the "parameter-material-aperture" mapping database stores historical drilling data and drilling results by establishing a "cloud database," and periodically analyzes the drilling data and results in the "cloud database" by designing a data analysis model, and then updates the mapping database based on the analysis results.

[0030] This invention discloses a segmented drilling method for a needle-and-thread fixture, which has the following beneficial effects:

[0031] 1. This segmented drilling method using a wire needle fixture is designed for micro-hole drilling on PCBs with large aspect ratios. Based on the characteristics of drilling at different depths, a segmented operation plan is designed, including a positioning stage, a high-efficiency chip removal stage, and an exit finishing stage. Different drilling strategies are implemented at different stages, with precise control over the rotation speed, feed rate, and single-pass depth. This allows for the formation of accurate guide holes on the board in the initial stage; continuous and smooth drilling in the middle stage; and effective prevention of edge chipping at the hole exit in the final stage. Compared with a fixed processing strategy, this method effectively improves processing efficiency, reduces board defect rate, and extends drill bit lifespan.

[0032] 2. This segmented drilling method using a wire needle fixture, during PCB drilling, is based on an initial segmented drilling strategy and simultaneously proposes to monitor the drill bit load. At different drilling stages, load changes reflect potential drilling problems. Then, based on load changes, the drilling parameters such as rotation speed, feed rate, and single feed amount are finely adjusted to avoid damage to the board or drill bit due to specific processing environment and material conditions.

[0033] 3. This segmented drilling method using a needle-and-thread jig establishes a "parameter-material-hole diameter" mapping database during the actual drilling process. During processing, the database is directly accessed to configure processing parameters based on the plate type and the hole parameters to be processed. Furthermore, the entire mapping database stores historical drilling data and drilling results through a "cloud database." A data analysis model is designed to periodically analyze the data and update the mapping database based on the analysis results. This facilitates parameter setting during processing, and the processing parameters are automatically updated during continuous use, further improving processing accuracy and efficiency. Attached Figure Description

[0034] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0035] Figure 1 This is a flowchart of the segmented drilling method of the present invention;

[0036] Figure 2 This is a schematic diagram of the mapping database project of the present invention. Detailed Implementation

[0037] To make the objectives, technical solutions, and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention are described clearly and completely. Obviously, the described embodiments are only some embodiments of the present invention, not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0038] This application provides a segmented drilling method using a needle-and-thread fixture, which solves the problems mentioned in the background art, such as failure to consider dynamic changes in the drilling process, uneven drill wear, and slow processing speed.

[0039] To better understand the above technical solutions, the following will provide a detailed explanation of the technical solutions in conjunction with the accompanying drawings and specific implementation methods.

[0040] This invention discloses a method for segmented drilling using a needle-and-thread jig.

[0041] Example 1, according to the appendix Figures 1 to 2 As shown, it includes the following steps:

[0042] S1. Establish a "parameter-material-pore size" mapping database;

[0043] S2. Select the drilling scheme with the corresponding number of segments based on the depth-to-diameter ratio of the drilled hole;

[0044] S3. Call the mapping database to configure the feed parameters to execute the drilling plan;

[0045] S4. Real-time monitoring of drill bit load, and dynamic adjustment of feed parameters based on load threshold;

[0046] S5. Establish an early warning and protection mechanism to perform rollback and shutdown protection when overload abnormalities occur;

[0047] in;

[0048] In step S2, the drilling scheme adopts a segmented drilling execution strategy, wherein the segments are L1, L2, ... Ln, and the value of n is proportional to the depth-to-diameter ratio of the drilling. L1 adopts a slow feed strategy to ensure that the drill bit can feed steadily and form a preset hole on the surface of the plate. L2 to Ln-1 adopt a fast feed strategy based on the dynamic adjustment in S4 to ensure that the hole depth is advanced quickly. Ln adopts a low feed strategy to avoid edge chipping at the end of the hole.

[0049] In the "Parameter-Material-Diameter" mapping database, parameters include rotational speed Vr, feed rate Vh, and single depth of cut Ho; material represents the plate material M; and hole diameter includes hole depth H and diameter D. By establishing the corresponding rotational speed Vr, feed rate Vh, and single depth of cut Ho mapping data tables based on the relationship between hole depth and diameter for different plate materials, when in use, by inputting material and hole diameter data, the corresponding execution parameters are automatically exported to execute the drilling scheme in step S3.

[0050] In the drilling scheme, L1 is the positioning stage. During the positioning stage, the minimum extension of the drill bit is Smin, so that the torsional resistance Tn of the drill bit reaches the maximum value. L1 adopts a high speed and low feed rate strategy, and the single feed depth is ≤0.1mm, so that a precise guide hole is formed on the plate.

[0051] L2 to Ln-1 is the high-efficiency chip removal stage. The high-efficiency chip removal stage adopts a single feed depth scheme that is higher than that of the positioning stage, and at the same time adopts a low speed and fast feed scheme to form a continuous and smooth drilling.

[0052] Ln represents the finishing stage at the exit point. During this stage, a low drilling speed and low feed rate strategy is employed, with a single feed depth ≤ 0.1 mm.

[0053] In step S3, the load current of the drill bit spindle is monitored in real time by the spindle load current sensor. The drilling resistance of the drill bit is determined based on the load current change, and corresponding load thresholds Imax and Imin are designed. Differentiated dynamic adjustment schemes are implemented according to different drilling stages.

[0054] The dynamic adjustment plan includes:

[0055] During the positioning phase, if the load current is detected to be greater than Imax, it indicates that the hardness of the plate material is greater than that of the preset plate material. At this time, the rotation speed can be increased while the feed speed is reduced.

[0056] If the load current is detected to be greater than Imax during the high-efficiency chip removal stage and the exit finishing stage, it indicates that chip blockage has occurred inside the borehole. At this time, the drill bit should be retracted to remove the chips.

[0057] If the load current is less than 1 min during the entire drilling process, it indicates that the drill bit is worn and needs to be replaced.

[0058] During the high-efficiency chip removal stage, when the monitored load current ∈ [Imin, Imax], from L2 to Ln-1, the drill bit speed gradually increases with the increase of feed depth, while the single feed amount decreases; the feed rate decreases.

[0059] During the finishing stage of the export, by reserving an export protection section, when the distance H between the drilling depth and the bottom of the plate is ≤1mm, the "pecking drill" method is adopted. After each entry, the drill immediately retracts, and the single entry amount is greater than the retraction amount by 0.1mm, thereby achieving downward advancement at a rate of 0.1mm.

[0060] In step S3, the drill bit load monitoring also includes temperature monitoring. For different drilling materials and corresponding drill bit materials, the temperature at the drill bit hole is captured in real time by an infrared temperature sensor. By setting corresponding temperature thresholds Tmax for drill bits of different materials, when the temperature at the drill hole reaches Tmax, the drill bit speed and feed rate are actively reduced. At the same time, for heat-sensitive plates, the machine is shut down for protection when the temperature reaches Tmax.

[0061] The "parameter-material-aperture" mapping database stores historical drilling data and drilling results by establishing a "cloud database". It also designs a data analysis model to periodically analyze the drilling data and results in the "cloud database" and then updates the mapping database based on the analysis results.

[0062] Working principle; In this embodiment, the following will be described in detail using actual drilling scheme data, wherein;

[0063] The substrate is FR-4 epoxy resin fiberglass cloth copper clad board with a thickness of 2.0mm, a board hardness of HB120-130, a resin content of 45%, and a fiberglass cloth model of 7628. This material is the mainstream substrate for PCB and wire needle fixtures, and has the characteristics of good insulation and high mechanical strength. However, problems such as resin sticking to the drill and fiberglass pulling are prone to occur during the drilling process.

[0064] Drill bit selection: A carbide ultra-micro twist drill with a diameter D=0.2mm, total length 12mm, working section length 3mm, core thickness 0.08mm, helix angle 30°, and a blunted cutting edge with a radius of 0.002mm is adopted. The torsional strength of this drill bit is 1200MPa, the torsional torque T is 0.08N·m, and it is suitable for micro-hole machining with a depth-to-diameter ratio ≤12:1.

[0065] Processing equipment: High-precision CNC micro-hole drilling machine with a maximum spindle speed of 300,000 r / min. It is equipped with a spindle load current sensor (measurement accuracy ±0.01A), vacuum adsorption fixture (adsorption force adjustable range 0.1-0.5MPa), and real-time vibration monitoring module, supporting millisecond-level dynamic adjustment of feed parameters.

[0066] Based on the processing characteristics of FR-4 sheet metal and the processing requirements of 0.2mm hole diameter and 2mm hole depth, this embodiment builds a localized mapping database and synchronizes it to the cloud database. The core fields and mapping relationships of the database are shown below.

[0067]

[0068] In this embodiment, the depth-to-diameter ratio = 2.0 / 0.2 = 10. According to the technical solution of the present invention, the value of the number of segments n is proportional to the depth-to-diameter ratio. Combining the processing difficulty of FR-4 plate and the performance parameters of 0.2mm drill bit, the number of segments in this embodiment is determined to be n = 4, that is, divided into three core stages: positioning stage (L1), high-efficiency chip removal stage (L2, L3), and exit finishing stage (L4), with a total of 4 processing segments. The processing objectives of each segment are clear.

[0069] L1 section: forms a precise guide hole on the surface of the plate to prevent drill bit deviation and ensure hole position accuracy;

[0070] L2-L3 section: rapidly advances hole depth while achieving efficient chip removal and reducing drilling resistance;

[0071] L4 section; fine-tune the hole outlet to avoid edge chipping defects in the fiberglass substrate;

[0072] Based on the machining requirements, input the material type = FR-4, hole diameter D = 0.2mm, and hole depth H = 2.0mm into the control system of the CNC drilling machine. The system will automatically call the parameters in the mapping database to complete the initial feed parameter configuration, as follows;

[0073] Parameter configuration in the positioning stage: Set the rotational speed to 250000 r / min, the feed rate to 5 mm / min, the single feed depth to 0.05 mm, and accumulate the feed to a hole depth of 0.1 mm. At the same time, set the drill bit extension to 0.2 mm. At this time, the torsional resistance of the drill bit reaches the maximum value of 0.08 N·m, reducing the risk of tool breakage in the positioning stage from the root cause. When the monitored load current I > Imax = 0.5 A, it is determined that the hardness of the plate is relatively high. The control system automatically increases the rotational speed to 280000 (a 12% increase), and at the same time reduces the feed rate to 3 mm / min (a 40% reduction), increasing the drilling force of the drill bit and reducing the frictional resistance between the drill bit and the plate. When the monitored load current < Imin = 0.24, it is determined that the drill bit is worn. The system immediately issues a tool change reminder to avoid the deviation of the guide hole caused by the dulling of the drill bit edge. In the actual trial processing, the actual load current in the L1 stage is stable at 0.35 - 0.45 A, and no parameter adjustment is triggered. The position accuracy of the guide hole reaches ±0.005 mm, meeting the processing requirements of the wire needle fixture;

[0074] Parameter configuration in the efficient chip removal stage: The initial rotational speed in the L2 segment is 180000 r / min, the feed rate is 20 mm / min, and the single feed depth is 0.2 mm; the initial rotational speed in the L3 segment is 220000 r / min, the feed rate is 12 mm / min, and the single feed depth is 0.1 mm. The load current thresholds for both segments are set to Imin = 0.3 A and Imax = 0.8 A, and the extension is adjusted to 0.3 mm to balance the processing efficiency and torsional resistance performance. When the monitored load current I > Imar = 0.8 A, it is determined that there is chip blockage in the hole. The control system immediately controls the drill bit to retract 0.5 mm and perform a chip removal operation. After the chip removal is completed, reduce the single feed depth (such as from 0.2 mm to 0.15 mm in the L2 segment), and at the same time increase the rotational speed by 5000 - 10000 r / min to enhance the fracture and discharge ability of drilling. When the monitored load current I ∈ [Imin, Ima], implement a gradient adjustment strategy; from the L2 segment to the L3 segment, as the hole depth increases, the rotational speed gradually increases from 180000 r / min to 240000 r / min, the feed rate gradually decreases from 20 mm / min to 8 mm / min, and the single feed depth gradually decreases from 0.2 mm to 0.08 mm. The principle of this strategy is that as the hole depth increases, the chip removal difficulty increases. By increasing the rotational speed, the centrifugal chip removal ability is enhanced, and at the same time, the feed rate and single feed depth are reduced to reduce the drilling resistance. In this trial processing, the actual load current in the L2 - L3 stage is stable at 0.4 - 0.6 A, no chip blockage occurs, the drilling is in a continuous spiral shape, and the chip removal is smooth with the hole wall roughness Ra ≤ 0.8 μm;

[0075] Parameter configuration for the exit finishing stage; set the rotational speed to 100,000 r / min, the feed rate to 3 mm / min, adopt the peck drilling method, with a single feed amount of 0.05 mm, a retraction amount of 0.04 mm, the feed amount is 0.1 mm greater than the retraction amount, and advance to a hole depth of 2.0 mm at an equivalent progress of 0.01 mm. When the monitored load current I > Imax = 0.6 A, it is determined that there is stress concentration in the exit area, and the system immediately switches to the "micro peck drilling" mode, reducing the single feed amount to 0.03 mm while keeping the retraction amount at 0.04 mm, releasing stress through high-frequency small retractions to avoid edge chipping at the exit; when the monitored load current I < Imin = 0.25 A, it is determined that the drill bit is about to penetrate the plate, and the system reduces the feed rate to 2 mm / min to complete the final finishing process. In this trial processing, the edge chipping size at the exit of the processed hole in the L4 stage is ≤ 0.01 mm, far lower than the edge chipping requirement of ≤ 0.05 mm for the wire needle fixture.

[0076] The final processing result is;

[0077] Hole position accuracy; ±0.008 mm, better than ±0.02 mm of the traditional drilling process;

[0078] Hole wall roughness; Ra = 0.6 - 0.8 um, meeting the assembly requirements of the wire needle fixture;

[0079] Exit edge chipping; ≤0.01 mm, far lower than ≤0.05 mm of the industry standard;

[0080] Drill bit life; a single drill bit can process 1200 holes, a 50% improvement compared to the traditional process.

[0081] In summary, the segmented drilling method of this wire needle fixture realizes different processing strategies for different stages of the plate by implementing a segmented strategy; at the same time, during the entire processing process, by monitoring the change in the drill bit load, reflecting the current processing situation based on the load change, and then implementing a dynamic parameter adjustment strategy, dynamically adjusting parameters such as drill speed and feed according to the actual situation, avoiding damage to the plate and drill bit, and by establishing an early warning protection mechanism, in case of emergencies, it can brake and retract the tool urgently to avoid serious production accidents.

[0082] Example 2. According to the appendix Figures 1 to 2 As shown, it includes the following steps:

[0083] S1. Establish a "parameter - material - hole diameter" mapping database;

[0084] S2. Select a drilling plan with the corresponding number of segments based on the depth - diameter ratio of the drilled hole;

[0085] S3. Call the mapping database to configure the feed parameters to execute the drilling plan;

[0086] S4. Real-time monitoring of drill bit load, and dynamic adjustment of feed parameters based on load threshold;

[0087] S5. Establish an early warning and protection mechanism to perform rollback and shutdown protection when overload abnormalities occur;

[0088] in;

[0089] In step S2, the drilling scheme adopts a segmented drilling execution strategy, wherein the segments are L1, L2, ... Ln, and the value of n is proportional to the depth-to-diameter ratio of the drilling. L1 adopts a slow feed strategy to ensure that the drill bit can feed steadily and form a preset hole on the surface of the plate. L2 to Ln-1 adopt a fast feed strategy based on the dynamic adjustment in S4 to ensure that the hole depth is advanced quickly. Ln adopts a low feed strategy to avoid edge chipping at the end of the hole.

[0090] In the "Parameter-Material-Diameter" mapping database, parameters include rotational speed Vr, feed rate Vh, and single depth of cut Ho; material represents the plate material M; and hole diameter includes hole depth H and diameter D. By establishing the corresponding rotational speed Vr, feed rate Vh, and single depth of cut Ho mapping data tables based on the relationship between hole depth and diameter for different plate materials, when in use, by inputting material and hole diameter data, the corresponding execution parameters are automatically exported to execute the drilling scheme in step S3.

[0091] In the drilling scheme, L1 is the positioning stage. During the positioning stage, the minimum extension of the drill bit is Smin, so that the torsional resistance Tn of the drill bit reaches the maximum value. L1 adopts a high speed and low feed rate strategy, and the single feed depth is ≤0.1mm, so that a precise guide hole is formed on the plate.

[0092] L2 to Ln-1 is the high-efficiency chip removal stage. The high-efficiency chip removal stage adopts a single feed depth scheme that is higher than that of the positioning stage, and at the same time adopts a low speed and fast feed scheme to form a continuous and smooth drilling.

[0093] Ln represents the finishing stage at the exit point. During this stage, a low drilling speed and low feed rate strategy is employed, with a single feed depth ≤ 0.1 mm.

[0094] In the drilling scheme, the number of stages n≥2. By establishing the maximum threshold Dmax of diameter D in the mapping database, if the diameter of the currently drilled hole is >Dmax, the drill bit diameter is large, and n=2. A two-stage drilling method is adopted, in which the high-efficiency chip removal stage L2 and the exit finishing stage are merged to form the high-efficiency drilling stage, and the same dynamic adjustment scheme as the high-efficiency chip removal stage L2 is adopted in the high-efficiency drilling stage.

[0095] In step S3, the drill bit load monitoring also includes temperature monitoring. When dealing with different drilling materials and corresponding drill bit materials, the temperature at the drill bit hole is captured in real time by an infrared temperature sensor. By setting corresponding temperature thresholds Tmax for drill bits of different materials, when the temperature at the drill hole reaches Tmax, the drill bit speed and feed rate are actively reduced. At the same time, for heat-sensitive plates, the machine is shut down for protection when the temperature approaches Tmax.

[0096] The "parameter-material-aperture" mapping database stores historical drilling data and drilling results by establishing a "cloud database". It also designs a data analysis model to periodically analyze the drilling data and results in the "cloud database" and then updates the mapping database based on the analysis results.

[0097] Working principle: In this embodiment, for aluminum-based metal substrates with a thickness of 5mm, a large hole diameter and depth of 5mm are processed with a depth-to-diameter ratio of 1:1. A two-stage drilling process is designed to solve the problems of poor chip removal and exit burrs in large hole processing.

[0098] During this machining process, a carbide drill bit with a diameter of 5mm, a total length of 50mm, a working section length of 10mm, and a torsional strength of 900MPa was selected. The machining equipment was a conventional CNC drilling machine with a spindle speed range of 5000-20000r / min, equipped with a load current sensor with threshold values ​​of Imin=1.2A and Imax=2.5A.

[0099]

[0100] During the positioning stage: set the drill bit extension to 5mm, and process at a high speed of 18000r / min and a low feed rate of 20mm / min, with a single feed of 0.08mm, forming a 0.1mm deep guide hole on the substrate surface; if the load current is >2.5A, it is determined that the board hardness is too high, and the speed is increased to 20000r / min and the feed rate is reduced to 15mm / min;

[0101] High-efficiency drilling stage: Combines chip removal and finishing functions. Initial parameters: 12000 r / min rotation speed, 80 mm / min feed rate, 1 mm single cut depth. During machining, the load current is monitored in real time. If I ∈ [1.2A, 2.5A], as the hole depth increases, the rotation speed gradient increases to 15000 r / min, the feed rate decreases to 50 mm / min, and the single cut depth decreases to 0.5 mm to ensure continuous chip removal. If the current > 2.5A, a 1 mm chip removal retraction is performed before resuming machining. If the current < 1.2A, drill wear is detected, and the machine is stopped for tool replacement. If the current exceeds the threshold for 100 ms, a first-level warning is triggered to retract the chip removal. If the current still fails to return to the threshold, a second-level warning is triggered to stop the machine, ensuring machining safety.

[0102] During this trial processing, the two-stage process achieved a hole position accuracy of ±0.02mm and an exit burr of ≤0.03mm for large-diameter holes, with a single hole processing time of only 45 seconds, which is 40% more efficient than the traditional process. At the same time, no abnormal load or temperature occurred during the entire processing. Therefore, it can be seen that this solution has obvious technical advantages for mainstream PCB board materials and, while ensuring the quality of the board material, it has significant advantages for processing.

[0103] The foregoing has shown and described the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The embodiments and descriptions in the specification are merely illustrative of the principles of the invention. Various changes and modifications can be made to the invention without departing from its spirit and scope, and all such changes and modifications fall within the scope of the present invention as claimed. The scope of protection of this invention is defined by the appended claims and their equivalents.

Claims

1. A method for segmented drilling with a thread needle fixture, characterized in that, Includes the following steps: S1. Establish a "parameter-material-pore size" mapping database; S2. Select the drilling scheme with the corresponding number of segments based on the depth-to-diameter ratio of the drilled hole; S3. Call the mapping database to configure the feed parameters to execute the drilling plan; S4. Real-time monitoring of drill bit load, and dynamic adjustment of feed parameters based on load threshold; S5. Establish an early warning and protection mechanism to perform rollback and shutdown protection when overload abnormalities occur; in; In step S2, the drilling scheme adopts a segmented drilling execution strategy, wherein the segments are sequentially L1, L2, ... Ln, and the value of n is proportional to the depth-to-diameter ratio of the hole; L1 adopts a slow feed strategy to ensure that the drill bit can feed steadily and form a preset hole on the surface of the plate; L2 to Ln-1 adopt a fast feed strategy based on the dynamic adjustment in S4 to ensure that the hole depth is advanced quickly; Ln adopts a low feed strategy to avoid edge chipping at the end of the hole. The "parameter-material-aperture" mapping database includes parameters such as rotational speed Vr, feed rate Vh, and single depth of cut Ho; material represents the plate material M; and aperture includes hole depth H and diameter D. A mapping data table of rotational speed Vr, feed rate Vh, and single depth of cut Ho is established by matching the hole depth and diameter of different plate materials. In use, by inputting material and aperture data, the corresponding execution parameters are automatically exported to execute the drilling scheme in step S3. In the drilling scheme, L1 is the positioning stage, during which the minimum extension of the drill bit is Smin, so that the torsional resistance Tn of the drill bit reaches its maximum value; L1 adopts a high-speed, low-feed-speed strategy, and the single feed depth is ≤0.1mm, so that a precise guide hole is formed on the plate. L2 to Ln-1 is the high-efficiency chip removal stage. The high-efficiency chip removal stage adopts a single feed depth scheme that is higher than that of the positioning stage, and at the same time adopts a low speed and fast feed scheme to form a continuous and smooth drilling. Ln represents the exit finishing stage, which employs a low drilling speed and low feed rate strategy, with a single feed depth ≤ 0.1 mm.

2. The method for segmented drilling with a needle and thread fixture according to claim 1, characterized in that, In step S3, the load current of the drill bit spindle is monitored in real time by a spindle load current sensor. The drilling resistance of the drill bit is determined based on the load current change, and corresponding load thresholds Imax and Imin are designed. Differentiated dynamic adjustment schemes are implemented according to different drilling stages.

3. The method for segmented drilling with a needle and thread fixture according to claim 2, characterized in that, The dynamic adjustment scheme includes: During the positioning stage, if the load current is detected to be greater than Imax, it indicates that the hardness of the plate material is greater than that of the preset plate material. At this time, the rotation speed can be increased while the feed speed is reduced. If the load current is detected to be greater than Imax during the high-efficiency chip removal stage and the exit finishing stage, it indicates that chip blockage has occurred inside the borehole. At this time, the drill bit is controlled to retract to remove the chips. If the load current is less than 1 min during the entire drilling process, it indicates that the drill bit is worn and needs to be replaced.

4. The method for segmented drilling with a needle and thread fixture according to claim 3, characterized in that, During the high-efficiency chip removal stage, when the monitored load current ∈ [Imin, Imax], from L2 to Ln-1, the drill bit speed gradually increases with the increase of feed depth, while the single feed amount decreases; the feed rate decreases.

5. The method for segmented drilling with a needle and thread fixture according to claim 1, characterized in that, In the drilling scheme, the number of stages n≥2. By establishing a maximum threshold Dmax for diameter D in the mapping database, if the diameter of the currently drilled hole is >Dmax, the drill bit diameter is large, and n=2. A two-stage drilling method is adopted, in which the high-efficiency chip removal stage L2 and the exit finishing stage are combined to form the high-efficiency drilling stage, and the same dynamic adjustment scheme as the high-efficiency chip removal stage L2 is adopted in the high-efficiency drilling stage.

6. The method for segmented drilling with a needle and thread fixture according to claim 2, characterized in that, In step S3, the drill bit load monitoring also includes temperature monitoring. When dealing with different drilling materials and corresponding drill bit materials, the temperature at the drill bit hole is captured in real time by an infrared temperature sensor. By setting corresponding temperature thresholds Tmax for drill bits of different materials, when the temperature at the drill hole reaches Tmax, the drill bit speed and feed rate are actively reduced. At the same time, for heat-sensitive plates, the machine is shut down for protection when the temperature reaches Tmax.

7. The method for segmented drilling with a needle and thread fixture according to claim 1, characterized in that, During the finishing stage at the exit, by reserving an exit protection section, when the distance H between the drilling depth and the bottom of the plate is ≤1mm, a "pecking drill" method is adopted, and the drill is immediately retracted after each advance. The single advance amount is greater than the retraction amount by 0.1mm, thereby achieving downward advancement at a rate of 0.1mm.

8. The method for segmented drilling with a needle and thread fixture according to claim 1, characterized in that, The "parameter-material-aperture" mapping database stores historical drilling data and drilling results by establishing a "cloud database". A data analysis model is designed to periodically analyze the drilling data and results in the "cloud database" and then update the mapping database based on the analysis results.

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