Dynamic negative pressure control method for high-aspect-ratio PCB drilling

Abstract

The present application relates to the technical field of PCB numerical control drilling and dust suction negative pressure control, and discloses a dynamic negative pressure control method for high thickness-diameter ratio PCB drilling. The method acquires Z-axis position data, motion state data and actual negative pressure of the presser foot cavity, and the actual negative pressure is used for monitoring the negative pressure reaching and safety state; based on the position and motion direction, the first drilling state, the second drilling state or the back-off reinforced chip removal state is determined, and the presser foot cavity is controlled to adopt the first negative pressure P1, the second negative pressure P2 or the third negative pressure P3, wherein P1P2P3; after confirming the back-off event, the negative pressure is increased to P3 during the current back-off period and is maintained until the back-off ends, then the state is re-judged according to the current position and motion direction, P1 or P2 is restored, or the safety basic negative pressure is adopted when safety degradation is needed. The present application helps to consider the drilling stability of the plate entering and shallow hole stage, the chip removal demand of the drilling in the deeper hole and the back-off stage, and reduces the risk of negative pressure state mismatch.

Description

Technical Field

[0001] This invention relates to the field of PCB CNC drilling and dust extraction negative pressure control technology, and in particular to a method for dynamically controlling the negative pressure of the pressure foot cavity according to the drilling state during the drilling process of PCBs with high thickness-to-diameter ratio. Background Technology

[0002] With the development of high-density interconnects and multilayer printed circuit boards, PCB board thickness has increased and finished hole diameter has decreased. Drilling of high aspect ratio PCBs is more prone to problems such as drill bit wobble, poor chip removal, and tool breakage. High aspect ratio PCBs refer to products with a high ratio of PCB board thickness to finished hole diameter. The micro drills used for drilling these PCBs are usually quite thin and long, and are more sensitive to airflow and chip removal conditions during the drilling process.

[0003] Current PCB CNC drilling processes typically set a suction negative pressure before machining begins and maintain this pressure throughout the drilling process. While a larger fixed negative pressure is beneficial for chip removal, when the drill bit first enters the board or is in a shallow hole, the drill bit has a longer overhang and has not yet received sufficient hole wall support. Strong and uneven airflow can increase the risk of drill tip wobble, hole position deviation, instability, and tool breakage. If a lower negative pressure is used throughout to reduce these risks, chip retention, friction, and temperature rise may occur as the drill bit enters deeper holes due to the extended chip removal path, further increasing the risk of hole wall quality degradation and tool breakage.

[0004] Furthermore, during the retraction of the drill bit, the upward movement of the drill bit increases the flow space within the hole, providing conditions for the concentrated discharge of chips from the bottom of the hole and near the chip removal groove. However, a fixed negative pressure cannot enhance chip removal during this short-term condition. After the retraction is completed, if the high negative pressure maintained during the retraction is continued, or if only the fixed value before the retraction is restored, the negative pressure in the pressure foot chamber may become mismatched with the current position, direction of movement, or safety status of the drill bit.

[0005] Therefore, there is an urgent need for a control method that can dynamically configure the negative pressure of the pressure foot cavity according to the state of the drill bit in the entry plate or shallow hole, the drilling state in deeper holes, and the retraction state, and redetermine the appropriate negative pressure state after the retraction ends or in abnormal situations, so as to take into account the stability of shallow hole drilling, the chip removal requirements in the hole, and the safety of chip removal during retraction. Summary of the Invention

[0006] The purpose of this invention is to provide a dynamic negative pressure control method for drilling PCBs with high aspect ratios, in order to solve the technical problem that the fixed negative pressure in the prior art is difficult to adapt to the negative pressure requirements of the drill bit in different states such as approaching the PCB board, entering the board or drilling in shallow holes, deeper holes, and upward retraction, and that the negative pressure state mismatch may occur after the retraction is completed.

[0007] To achieve this objective, the present invention adopts the following technical solution: This invention provides a dynamic negative pressure control method for drilling holes in PCBs with high aspect ratios, comprising the following steps: S1. During PCB drilling, acquire Z-axis position data that can determine the axial position or drilling depth of the drill bit, motion state data that can determine the feed direction or retraction direction of the drill bit, and detect the actual negative pressure of the pressure foot cavity. Based on the actual negative pressure, monitor the negative pressure status and safety status of the pressure foot cavity. S2. Based on the Z-axis position data and the motion state data, determine whether the drill bit is in a first drilling state, a second drilling state, or a retraction and chip removal state. The first drilling state is when the drill bit is close to the PCB board, enters the board, or is within a preset shallow hole range. The second drilling state is when the drill bit enters the PCB board and is at a deeper position after the preset shallow hole range to perform drilling inside the hole. The retraction and chip removal state is when the drill bit is confirmed to retract upwards. S3. Based on the determined drilling state, control the negative pressure of the pressure foot cavity. In the first drilling state, control it to a first negative pressure P1, and in the second drilling state, control it to a second negative pressure P2. After confirming the retraction event, enter the retraction enhanced chip removal state, and during this retraction, increase the negative pressure of the pressure foot cavity to a third negative pressure P3 and maintain it until the end of this retraction. Here, P1, P2 and P3 all represent the magnitude of the negative pressure, and P1 < P2 < P3. S4. After this retraction is completed, the drilling state of the drill bit is re-determined based on the current Z-axis position data and the motion state data, and the negative pressure of the pressure foot cavity is controlled to P1 or P2 according to the re-determined drilling state, or the negative pressure of the pressure foot cavity is controlled to the safe basic negative pressure when the safety state indicates that a safety degradation is required.

[0008] In some implementations, step S2, determining the first drilling state and the second drilling state, specifically includes: The position where the drill tip just contacts the cover plate or the surface of the PCB board is defined as the zero point of board entry. The safe position above the surface of the PCB board is recorded as H0. The end position of the shallow hole stage is recorded as H1. The final position that the hole is planned to reach is recorded as H2. The range between H0 and the zero point of the board entry is defined as the range in which the drill bit approaches the PCB board. The range between the zero point of the board entry and H1 is defined as the preset shallow hole range. The range between H1 and H2 is defined as the hole drilling range corresponding to the second drilling state.

[0009] In some implementations, step S2, switching between the first drilling state and the second drilling state based on the Z-axis position data and the motion state data, specifically includes: After the detection results obtained based on the Z-axis position data and the motion state data have been continuously stable for a period of time, the drilling state is switched and the negative pressure of the pressure foot cavity is switched accordingly. Different state boundary positions are used when the pressure is increased from P1 to P2 and when the pressure is decreased from P2 to P1.

[0010] In some implementations, step S3, confirming the rollback event, specifically includes: When the drill bit retracts after receiving the drill retraction command, the actual Z-axis movement direction indicated by the motion state data is used to confirm that the drill bit retracts upward. If the drill bit retraction command is not received, after the motion status data indicates that the drill bit has changed from continuous downward movement to continuous upward movement, the drill bit is confirmed to retract upward.

[0011] In some implementations, step S3, after confirming the retraction event, involves increasing the negative pressure in the pressure foot chamber to P3 and maintaining it until the current retraction ends. Specifically, this includes: Within one control cycle after confirming the retraction event, the negative pressure rise process of the presser foot chamber is initiated to smoothly raise the negative pressure of the presser foot chamber to P3, and P3 is maintained until the end of this retraction. After this retraction is completed, the negative pressure in the pressure foot cavity will be steadily reduced.

[0012] In some implementations, step S4, after the current retraction is completed, re-determines the drilling state of the drill bit and controls the negative pressure in the pressure foot cavity, specifically including: Prioritize handling safety signals such as emergency stop, tool change, malfunction, or completion of this hole. When such safety signal is present, control the negative pressure of the pressure foot cavity to the safety baseline negative pressure. In the absence of the safety signal, based on the current Z-axis position data and the motion state data, P1 is used when the drill bit moves downward again and is within the preset shallow hole range, P2 is used when the drill bit is not in an upward retraction and is in a deeper position beyond the preset shallow hole range, and P3 is used only when it is confirmed that the drill bit has retracted upward again. After this rollback is completed, the P3 flag used to indicate entry into P3 is cleared, and entry into P3 is only allowed again after a complete rollback action is detected again.

[0013] In some implementations, during the execution of the above method, safety control is performed based on the Z-axis position data, the motion state data, and the actual negative pressure, specifically including: If at least one of the Z-axis position data, the motion state data, and the actual negative pressure is lost, exceeds the range, or continuously times out, or if there is a contradiction between the Z-axis position data, the motion state data, and the actual negative pressure, the increase of the negative pressure in the pressure foot cavity is stopped, the pressure is switched to the safe basic negative pressure, and an alarm is recorded. In the event of an emergency stop, abnormal tool retraction, position detection failure, excessively high actual negative pressure, or valve malfunction, P3 is canceled to control the negative pressure in the pressure foot chamber to the safe baseline negative pressure, and tool retraction or shutdown protection is executed.

[0014] In some implementations, the Z-axis position data and the motion state data come from the CNC system or Z-axis encoder of the PCB CNC drilling equipment, and the actual negative pressure is detected by a pressure sensor located in or near the presser foot cavity; The dynamic negative pressure control method for drilling holes in high aspect ratio PCBs also includes: The drilling state determination result is verified by acquiring at least one of the following: a pecking command, a spindle load, a feed force, or a vibration signal. The pecking command comes from the drilling program or the controller, the spindle load comes from the current feedback or torque feedback of the driver, and the feed force comes from the feed axis load or an independent force sensor.

[0015] In some implementations, the specific values ​​of the first negative pressure P1, the second negative pressure P2, and the third negative pressure P3 are determined through trial drilling based on the PCB board thickness, finished hole diameter, material type, drill bit specifications, and dust extraction pipeline.

[0016] In some embodiments, the ratio of the thickness of the PCB board to the finished hole diameter is not less than 30:1, and the finished hole diameter is 0.15-0.35mm.

[0017] Compared with the prior art, the present invention has the following beneficial effects: This invention identifies the drilling state of the drill bit using Z-axis position data and motion state data. A lower first negative pressure P1 is applied when drilling near the PCB board, entering the board, or within a preset shallow hole range, while a higher second negative pressure P2 is applied when drilling in deeper holes. This helps reduce the risk of drill bit wobbling and instability caused by uneven airflow during shallow hole drilling, and enhances the upward airflow along the drill bit's chip removal grooves when the chip removal path is extended, reducing the risk of chip retention, friction, and temperature rise. On the other hand, after confirming the drill bit's upward retraction, a third negative pressure P3, higher than P2, is applied and maintained until the end of this retraction. This helps to concentrate and remove chips and heat by utilizing the increased flow space within the hole during the retraction period; after the retraction is completed, the drilling status is re-determined based on the current position and direction of the drill bit, rather than simply restoring the negative pressure before retraction or continuing to maintain P3, thereby reducing the risk of negative pressure mismatch and P3 erroneous maintenance; on the other hand, by using the actual negative pressure to monitor the negative pressure level and safety status of the pressure foot chamber, and stopping the pressure increase, switching to a safe basic negative pressure, and implementing corresponding protection when necessary input abnormalities or equipment malfunctions, it helps to avoid continuing to increase or maintain a high negative pressure under abnormal conditions.

[0018] The present invention has other features and advantages, which will be apparent from or will be set forth in detail in the accompanying drawings and the following detailed description, which together serve to explain the particular principles of the invention. Attached Figure Description

[0019] 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.

[0020] Figure 1 This is a structural schematic diagram of the first drilling state in an embodiment of the present invention.

[0021] Figure 2 This is a structural schematic diagram of the second drilling state in an embodiment of the present invention.

[0022] Figure 3 This is a schematic diagram of the structure of the retraction-enhanced chip removal state in an embodiment of the present invention.

[0023] Figure 4 This is a flowchart of the core steps of the dynamic negative pressure control method for drilling PCBs with high aspect ratios, according to an embodiment of the present invention.

[0024] Figure 5This is a complete logic block diagram of one embodiment of the dynamic negative pressure control method for drilling holes in PCBs with high aspect ratios according to the present invention. Detailed Implementation

[0025] To illustrate the possible application scenarios, technical principles, implementable specific solutions, and achievable objectives and effects of this application in detail, the following description, in conjunction with the listed specific embodiments and accompanying drawings, provides a detailed explanation. The embodiments described herein are merely illustrative of the technical solutions of this application and are therefore intended to limit the scope of protection of this application.

[0026] Please see Figures 1-5 The dynamic negative pressure control method for drilling high aspect ratio PCBs in this embodiment is used in the drilling process of PCB CNC drilling equipment. During drilling, the pressure foot cavity 31 is located above the PCB board 10 and forms a negative pressure environment for sucking out the chips 50. The drilling equipment adjusts the negative pressure of the pressure foot cavity 31 according to the drilling state of the drill bit 40.

[0027] For ease of description, the first negative pressure P1, the second negative pressure P2, and the third negative pressure P3 mentioned below all refer to the magnitude of the negative pressure. The larger the value, the stronger the suction, and the condition P1 < P2 < P3 is met. It is worth noting that P1, P2, and P3 represent the target negative pressure magnitude under different drilling conditions, rather than gauge pressure values ​​with positive and negative signs. It should be noted that the safety baseline negative pressure is a pre-verified safety negative pressure used in situations such as safety signal triggering, necessary input abnormalities, or drilling processes occurring in abnormal drilling conditions.

[0028] The core steps of the dynamic negative pressure control method for drilling high aspect ratio PCBs in this embodiment are as follows: Figure 4 As shown below, the steps of the method in this embodiment will be described in detail.

[0029] S1. During PCB drilling, acquire Z-axis position data that can determine the axial position or drilling depth of drill bit 40, motion state data that can determine the feed direction or retraction direction of drill bit 40, and detect the actual negative pressure of pressure foot cavity 31. Based on the actual negative pressure, monitor the negative pressure status and safety status of pressure foot cavity 31.

[0030] Understandably, all data are read in the same chronological order, with the specific reading speed and accuracy determined by the actual drilling rig and sensors. It is worth noting that the Z-axis position data and motion status data are used to identify the position range and direction of movement of the drill bit 40, while the actual negative pressure is used to monitor the negative pressure level and safety status of the pressure foot chamber 31, rather than using the actual negative pressure as a separate criterion for distinguishing between the first drilling state, the second drilling state, and the retraction and chip removal state.

[0031] The Z-axis position data and motion status data can come from the CNC system or Z-axis encoder of the PCB CNC drilling equipment, and the actual negative pressure can be detected by a pressure sensor located in or near the pressure foot cavity 31. As an extension, the method of this embodiment can further acquire at least one of the following: a pecking drill command, spindle load, feed force, or vibration signal, to verify the determination result of the drilling state. The pecking drill command can come from the drilling program or controller, the spindle load can come from the current feedback or torque feedback of the driver, and the feed force can come from the feed axis load or an independent force sensor.

[0032] S2. Based on the Z-axis position data and the motion state data, determine whether the drill bit 40 is in a first drilling state, a second drilling state, or a retraction and chip removal state. The first drilling state is when the drill bit 40 is close to the PCB board 10, enters the board, or is within a preset shallow hole range. The second drilling state is when the drill bit 40 enters the PCB board 10 and is at a deeper position after the preset shallow hole range to perform drilling inside the hole. The retraction and chip removal state is when the drill bit 40 is confirmed to be retracting upwards.

[0033] Specifically, in a hole machining cycle, the control process may also include a positioning preparation state and a drill-out reset state. The positioning preparation state corresponds to the stage where the drill bit 40 is in a safe position above the board surface shown by H0 and has not yet begun to approach the PCB board 10. The drill-out reset state corresponds to the stage where the current drilling process is exited after the hole is completed. In addition, a safe basic negative pressure is used in the above stages.

[0034] The position where the drill tip of drill bit 40 just contacts the surface of the cover plate or PCB board 10 is defined as the zero point O of board entry. The safe position above the surface of PCB board 10 is recorded as H0. The end position of the shallow hole stage is recorded as H1. The final position that the hole is planned to reach is recorded as H2.

[0035] The range from H0 to the zero point O of the board entry is defined as the range where the drill bit 40 approaches the PCB board 10, and the range from the zero point O of the board entry to H1 is defined as the preset shallow hole range. The two correspond to the first drilling state. The range between H1 and H2 is defined as the drilling range in the deeper hole after the preset shallow hole range, and corresponds to the second drilling state when the drill bit 40 does not retract upward. When it is confirmed that the drill bit 40 is retracting upwards, the drill bit 40 enters the retraction enhanced chip removal state.

[0036] It is understandable that H1 is a preset boundary position for the shallow hole stage based on specific drilling conditions, and can be adjusted according to the PCB board thickness, finished hole diameter, cover plate, and drill bit specifications. For example, under suitable conditions, the position where the drilling depth reaches approximately 10% of the planned hole depth D can be used as a reference for setting H1. This ratio is only an adjustable example, and D represents the planned drilling depth of this hole, not simply calculated based on the thickness of the entire PCB board (10).

[0037] To reduce repeated changes in negative pressure when the drill bit 40 is near the boundary position, the drilling state is switched and the negative pressure of the pressure foot cavity 31 is switched accordingly after the detection results obtained based on the Z-axis position data and motion state data have been continuously stable for a period of time. Different state boundary positions are used when increasing pressure from P1 to P2 and when decreasing pressure from P2 to P1 to form a hysteresis in the state switching.

[0038] S3. Based on the determined drilling state, control the negative pressure of the pressure foot cavity 31. In the first drilling state, control it to a first negative pressure P1, and in the second drilling state, control it to a second negative pressure P2. After confirming the retraction event, enter the retraction enhanced chip removal state, and during this retraction, increase the negative pressure of the pressure foot cavity 31 to a third negative pressure P3 and maintain it until the end of this retraction. Here, P1, P2 and P3 all represent the magnitude of the negative pressure, and P1 < P2 < P3.

[0039] The following is combined Figures 1 to 3 The working process of the method in this embodiment will be described in detail below.

[0040] The PCB board 10 is placed on the pad 20, and the pressure foot 30 is located above the PCB board 10. A pressure foot cavity 31 is formed inside the pressure foot 30, and the pressure foot 30 is provided with a chip removal outlet 32 ​​communicating with the pressure foot cavity 31. The drill bit 40 passes through the pressure foot cavity 31 and faces the PCB board 10. After the drill bit 40 enters the PCB board 10, it forms a drill hole 41. The chips 50 generated during drilling are discharged through the pressure foot cavity 31 and the chip removal outlet 32.

[0041] like Figure 1 As shown, when the drill bit 40 is located between H0 and the zero point O of the board entry and is close to the PCB board 10, or has already entered the board and is located within the preset shallow hole range between the zero point O and H1, the drill bit 40 is determined to be in the first drilling state and P1 is adopted. In this state, the effective overhang length of the drill bit 40 is relatively large, and the hole wall has not yet provided sufficient support for the drill bit 40. It is understandable that adopting a lower P1, while meeting the basic dust collection requirements at this stage, helps to reduce the lateral disturbance of the micro-drill caused by the uneven airflow in the pressure foot cavity 31, thereby reducing the risk of drill tip wobble, hole position deviation, instability, and tool breakage. Figure 1 In the diagram, the dashed arrow indicates the direction of the chip removal airflow, and the solid arrow indicates the forward direction of the drill bit 40.

[0042] like Figure 2 As shown, when the drill bit 40 enters the PCB board 10, passes H1 and is located at a deeper position after the preset shallow hole range, and is not in an upward retraction state, the drill bit 40 is determined to be in the second drilling state and P2 is adopted. It can be understood that as the drilling depth increases, the hole wall can form a certain radial guide for the drill bit 40, but the chip 50 discharge path is also correspondingly lengthened; increasing the negative pressure of the pressure foot cavity 31 from P1 to P2 helps to enhance the airflow upward along the chip removal groove of the drill bit 40, so that the chips 50 are discharged out of the hole and take away the heat, thereby reducing the risk of chip 50 retention, friction and temperature rise in the hole. Figure 2 In the diagram, the dashed arrow indicates the direction of the chip removal airflow, and the solid arrow indicates the forward direction of the drill bit 40.

[0043] For the drill bit 40 retraction event, when the drill bit retraction command can be obtained, the drill bit retraction command issued by the drill rig is obtained and confirmed in combination with the actual Z-axis movement direction indicated by the motion status data. When the actual movement direction is upward, the drill bit 40 is confirmed to have retracted. When the drill bit retraction command is not obtained, the drill bit 40 is confirmed to have retracted after the motion status data indicates that the drill bit 40 has changed from continuous downward movement to continuous upward movement.

[0044] Upon confirmation of the rollback event, the negative pressure increase process of the pressure foot chamber 31 is initiated within one control cycle, smoothly increasing the negative pressure of the pressure foot chamber 31 from the current negative pressure to the third negative pressure P3, and maintaining it at P3 until the end of this rollback; after the end of this rollback, the negative pressure of the pressure foot chamber 31 is smoothly reduced. Note that "initiated within one control cycle" means that the pressure increase process begins within that control cycle, and does not mean that the negative pressure reaches P3 in a physically instantaneous step manner within that control cycle.

[0045] like Figure 3 As shown, after the drill bit 40 retracts upwards, the flow space inside the hole increases. By using P3, which is higher than P2, a stronger airflow can be used to concentrate and remove the chips 50 from the bottom of the hole and the vicinity of the chip flute, and also remove heat. P3 is maintained only during the confirmed retraction period and does not automatically continue into subsequent drilling processes even if the drill bit 40 has previously entered a retraction-enhanced chip removal state. Figure 3 In the diagram, the dashed arrow indicates the direction of the chip removal airflow, and the solid arrow indicates the direction of the drill bit's 40° retraction.

[0046] S4. After this retraction is completed, the drilling state of the drill bit 40 is re-determined based on the current Z-axis position data and the motion state data, and the negative pressure of the pressure foot cavity 31 is controlled to P1 or P2 according to the re-determined drilling state, or the negative pressure of the pressure foot cavity 31 is controlled to the safe basic negative pressure when the safety state indicates that a safety downgrade is required.

[0047] Specifically, during the reassessment, priority is given to handling safety signals such as emergency stop, tool change, malfunction, or completion of the current hole. If any of these safety signals are present, the negative pressure in the pressure foot chamber 31 is controlled to a safe baseline negative pressure. If no such safety signal is present, if the drill bit 40 moves downwards again and is within the preset shallow hole range, P1 is used; if the drill bit 40 is not in the upward retraction state and is located at a deeper position beyond the preset shallow hole range, P2 is used; P3 is only used when it is confirmed that the drill bit 40 has retracted upwards again.

[0048] It is important to note that after this retraction is completed, the P3 marker indicating entry into P3 is cleared, and re-entry into P3 is only permitted after a complete retraction action is detected again. The target negative pressure after the retraction ends depends on the current position, direction of movement, and safety status of the drill bit 40, rather than simply restoring the negative pressure before the retraction or continuing to maintain P3.

[0049] When the drill bit 40 penetrates the PCB board 10, leaves the board surface, pauses for a long time, or is about to move to the next hole, the negative pressure of the pressure foot cavity 31 is controlled to a safe basic negative pressure so as to distinguish the abnormal drilling stage from the drilling states corresponding to P1, P2 and P3.

[0050] Furthermore, during the execution of the above method, if at least one of the Z-axis position data, motion status data, and actual negative pressure is lost, exceeds the range, or continuously times out, or if the above data contradict each other, the increase of negative pressure in the pressure foot chamber 31 is stopped, the pressure is switched to the safe basic negative pressure, and an alarm is recorded.

[0051] In addition, in the event of emergency stop, abnormal tool retraction, position detection failure, excessively high actual negative pressure, or valve malfunction, P3 is canceled to control the negative pressure of the pressure foot chamber 31 to a safe baseline negative pressure and to perform tool retraction or shutdown protection.

[0052] Figure 5 The complete logic block diagram of the method in this embodiment is shown. The method in this embodiment starts with the acquisition and validity check of Z-axis position data, motion state data and actual negative pressure, and can use at least one of the following to verify the judgment result: pecking drill command, spindle load, feed force or vibration signal; then, the drilling state is identified by combining the position range and motion direction and P1, P2 or P3 is controlled; after the retraction is completed, the state is re-judged and the P3 flag is cleared; and in case of abnormality, the system switches to the safe basic negative pressure and performs alarm, tool retraction or shutdown protection.

[0053] It is worth noting that the specific values ​​of P1, P2 and P3 in this embodiment are determined by trial drilling based on the PCB board thickness, finished hole diameter, material, drill bit specifications and dust extraction pipeline, and the values ​​used maintain the relationship that P1 < P2 < P3.

[0054] The method described in this embodiment is mainly applicable to drilling of PCB board 10 where the ratio of board thickness to finished hole diameter is not less than 30:1 and the finished hole diameter is 0.15-0.35mm. Furthermore, this range is used to illustrate the main application scenario; the specific applicable boundaries should still be determined through trial drilling based on the board material, drill bit, and processing parameters.

[0055] For example, in a set of existing test drills, the PCB board thickness was 7.5mm, the hole diameter was 0.20mm, and the PCB thickness-to-diameter ratio was 37.5:1; a Jinzhou HL series coated drill bit with a diameter of 0.20mm was used, with an effective cutting length of 8.5mm and a cutting length-to-diameter ratio of 42.5:1. With other drilling parameters basically the same, multiple tool breaks occurred when the fixed dust suction negative pressure amplitude was set to 17-18kPa; after reducing the fixed dust suction negative pressure amplitude to 10-12kPa, continuous test drilling of 8 boards, each with more than 10,000 holes, did not result in tool breakage.

[0056] It should be noted that the 17-18 kPa and 10-12 kPa mentioned above are fixed negative pressure values ​​used under specific test drilling conditions, and cannot be equated with P1, P2, or P3 in this embodiment. The test drilling results are only used to illustrate that reducing the fixed negative pressure under the specific conditions helps to reduce the risk of drill bit 40° deflection and tool breakage, and to provide a basis for using a lower P1 in the plate entry or shallow hole stage. It does not constitute a complete control experiment of the three-stage dynamic control of P1, P2, and P3, nor is it used to calculate the tool breakage rate or derive the quantitative improvement results of dynamic control.

[0057] Combination Figures 1-5 On the one hand, this invention identifies the drilling state of the drill bit 40 by using Z-axis position data and motion state data. A lower first negative pressure P1 is applied when the drill bit is near the PCB board 10, entering the board, or within a preset shallow hole range. A higher second negative pressure P2 is applied when drilling in deeper holes. This helps reduce the risk of drill bit 40 wobbling and instability caused by uneven airflow during shallow hole drilling. Furthermore, it enhances the upward airflow along the drill bit's chip removal grooves when the chip removal path is extended, reducing the risk of chip retention, friction, and temperature rise. On the other hand, after confirming that the drill bit 40 has retracted upwards, a third negative pressure P3 higher than P2 is applied, and P3 is maintained until the current retraction. The retraction process helps to concentrate and remove chips and heat by utilizing the increased flow space within the hole during the retraction. After the retraction is completed, the drilling status is re-determined based on the current position and direction of movement of the drill bit 40, rather than simply restoring the negative pressure before retraction or continuing to maintain P3, thereby reducing the risk of mismatch in negative pressure status and erroneous maintenance of P3. Furthermore, by using the actual negative pressure to monitor the negative pressure level and safety status of the pressure foot cavity 31, and stopping the pressure increase, switching to a safe basic negative pressure, and implementing corresponding protection when necessary input abnormalities or equipment malfunctions, it helps to avoid continuing to increase or maintain a high negative pressure under abnormal conditions.

[0058] The above embodiments are only used to illustrate the technical solutions of the present invention, and are not intended to limit it. Although the present invention has been described in detail with reference to the foregoing embodiments, those skilled in the art should understand that modifications can still be made to the technical solutions described in the foregoing embodiments, or equivalent substitutions can be made to some of the technical features. Such modifications or substitutions do not cause the essence of the corresponding technical solutions to deviate from the spirit and scope of the technical solutions of the embodiments of the present invention.

Claims

1. A dynamic negative pressure control method for drilling holes in high aspect ratio PCBs, characterized in that, Includes the following steps: During PCB drilling, Z-axis position data that can determine the axial position or drilling depth of the drill bit, motion state data that can determine the feed direction or retraction direction of the drill bit, and actual negative pressure of the pressure foot cavity are detected. Based on the actual negative pressure, the negative pressure status and safety status of the pressure foot cavity are monitored. Based on the Z-axis position data and the motion state data, the drill bit is determined to be in a first drilling state, a second drilling state, or a retraction and chip removal state. The first drilling state is when the drill bit is close to the PCB board, enters the board, or is within a preset shallow hole range. The second drilling state is when the drill bit enters the PCB board and is at a deeper position after the preset shallow hole range to perform drilling inside the hole. The retraction and chip removal state is when the drill bit is confirmed to be retracting upwards. The negative pressure of the pressure foot cavity is controlled based on the determined drilling state. In the first drilling state, it is controlled as a first negative pressure P1, and in the second drilling state, it is controlled as a second negative pressure P2. After confirming the retraction event, the retraction enhanced chip removal state is entered, and during this retraction, the negative pressure of the pressure foot cavity is increased to a third negative pressure P3 and maintained until the end of this retraction. Here, P1, P2 and P3 all represent the magnitude of the negative pressure, and P1 < P2 < P3. After this rollback is completed, the drilling state of the drill bit is re-determined based on the current Z-axis position data and the motion state data. Based on the re-determined drilling state, the negative pressure of the pressure foot chamber is controlled to P1 or P2, or the negative pressure of the pressure foot chamber is controlled to a safe basic negative pressure when the safety status indicates that a safety degradation is required.

2. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, Determining the first drilling state and the second drilling state specifically includes: The position where the drill tip just contacts the cover plate or the surface of the PCB board is defined as the zero point of board entry. The safe position above the surface of the PCB board is recorded as H0. The end position of the shallow hole stage is recorded as H1. The final position that the hole is planned to reach is recorded as H2. The range between H0 and the zero point of the board entry is defined as the range in which the drill bit approaches the PCB board. The range between the zero point of the board entry and H1 is defined as the preset shallow hole range. The range between H1 and H2 is defined as the hole drilling range corresponding to the second drilling state.

3. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 2, characterized in that, Switching between the first drilling state and the second drilling state based on the Z-axis position data and the motion state data specifically includes: After the detection results obtained based on the Z-axis position data and the motion state data have been continuously stable for a period of time, the drilling state is switched and the negative pressure of the pressure foot cavity is switched accordingly. Different state boundary positions are used when the pressure is increased from P1 to P2 and when the pressure is decreased from P2 to P1.

4. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, The rollback event is confirmed, specifically including: When the drill bit retracts after receiving the drill retraction command, the actual Z-axis movement direction indicated by the motion state data is used to confirm that the drill bit retracts upward. If the drill bit retraction command is not received, after the motion status data indicates that the drill bit has changed from continuous downward movement to continuous upward movement, the drill bit is confirmed to retract upward.

5. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, After confirming the retraction event, the negative pressure in the pressure foot chamber is increased to P3 and maintained until the retraction ends. Specifically, this includes: Within one control cycle after confirming the retraction event, the negative pressure rise process of the presser foot chamber is initiated to smoothly raise the negative pressure of the presser foot chamber to P3, and P3 is maintained until the end of this retraction. After this retraction is completed, the negative pressure in the pressure foot cavity will be steadily reduced.

6. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, After this rollback is completed, the drilling state of the drill bit is reassessed and the negative pressure of the pressure foot chamber is controlled, specifically including: Prioritize handling safety signals such as emergency stop, tool change, malfunction, or completion of this hole. When such safety signal is present, control the negative pressure of the pressure foot cavity to the safety baseline negative pressure. In the absence of the safety signal, based on the current Z-axis position data and the motion state data, P1 is used when the drill bit moves downward again and is within the preset shallow hole range, P2 is used when the drill bit is not in an upward retraction and is in a deeper position beyond the preset shallow hole range, and P3 is used only when it is confirmed that the drill bit has retracted upward again. After this rollback is completed, the P3 flag used to indicate entry into P3 is cleared, and entry into P3 is only allowed again after a complete rollback action is detected again.

7. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, Safety control is performed based on the Z-axis position data, the motion state data, and the actual negative pressure, specifically including: If at least one of the Z-axis position data, the motion state data, and the actual negative pressure is lost, exceeds the range, or continuously times out, or if there is a contradiction between the Z-axis position data, the motion state data, and the actual negative pressure, the increase of the negative pressure in the pressure foot cavity is stopped, the pressure is switched to the safe basic negative pressure, and an alarm is recorded. In the event of an emergency stop, abnormal tool retraction, position detection failure, excessively high actual negative pressure, or valve malfunction, P3 is canceled to control the negative pressure in the pressure foot chamber to the safe baseline negative pressure, and tool retraction or shutdown protection is executed.

8. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, The Z-axis position data and the motion state data come from the CNC system or Z-axis encoder of the PCB CNC drilling equipment, and the actual negative pressure is detected by a pressure sensor located in or near the presser foot cavity; The dynamic negative pressure control method for drilling holes in high aspect ratio PCBs also includes: The drilling state determination result is verified by acquiring at least one of the following: a pecking command, a spindle load, a feed force, or a vibration signal. The pecking command comes from the drilling program or the controller, the spindle load comes from the current feedback or torque feedback of the driver, and the feed force comes from the feed axis load or an independent force sensor.

9. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, The specific values ​​of the first negative pressure P1, the second negative pressure P2, and the third negative pressure P3 are determined through trial drilling based on the PCB board thickness, finished hole diameter, material type, drill bit specifications, and dust extraction pipeline.

10. The dynamic negative pressure control method for drilling high aspect ratio PCBs as described in claim 1, characterized in that, The ratio of the thickness of the PCB board to the finished hole diameter is not less than 30:1, and the finished hole diameter is 0.15-0.35mm.

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