A system for collecting drilling force signals in an automatic feed drilling process and a method for using the signals

Abstract

This invention discloses a system for acquiring drilling force signals during automatic feed drilling and its application method. The system includes an automatic feed drill and a drilling force sensor. The automatic feed drill includes a spindle, with a drill bit connected to the bottom end of the spindle via a reverse thread. A nose tube is fitted around the outside of the spindle, and the lower end of the nose tube is connected to a drill bushing fitted around the drill bit via a flange. The drill bushing passes through a hole in the drill template, allowing the drill bit to drill a hole in the workpiece. A drilling force sensor is installed between the nose tube and the drill template. The method involves stopping the operation if a significant change in the actual drilling force or torque value occurs during the drilling process. If no significant change occurs, a threshold is set. When the actual drilling force or torque value exceeds the threshold, the spindle speed is reduced. This invention solves the problems of existing automatic feed drills requiring a dedicated fixture to fix the force gauge in order to acquire drilling force and torque signals during the drilling of aerospace materials, resulting in complex structures, inconvenient operation, and high costs.

Description

Technical Field

[0001] This invention relates to the field of machining technology for aerospace equipment, and in particular to a system for acquiring drilling force signals during automatic feed drilling and a method for applying those signals. Background Technology

[0002] Automatic feed drills (AFDs) offer advantages such as high drilling speed and efficiency, making them widely used in drilling operations for aerospace materials like CFRP, titanium alloys, and aluminum alloys. However, in actual operation, these drills often require specialized fixtures to hold the force gauge and collect drilling force and torque signals. This method of acquiring these signals necessitates expensive force gauges and specialized tooling fixtures. Furthermore, when the geometry of the workpiece changes, the fixtures must be replaced, increasing the operating cost of the AFD and complicating the work platform structure. Therefore, finding a more convenient and cost-effective way to collect drilling force and torque signals during drilling operations, as well as processing and analyzing the collected data to adjust the AFD's operating status, is a pressing issue that needs to be addressed. Summary of the Invention

[0003] Purpose of the invention: The purpose of this invention is to provide a convenient, simple, and low-cost automatic feed drilling process drilling force signal acquisition system and its signal application method.

[0004] Technical Solution: To achieve the above objectives, the present invention provides a drilling force signal acquisition system for automatic feed drilling, comprising an automatic feed drill and a drilling force sensor. The automatic feed drill includes a spindle that performs a combined rotational and feed motion. A drill bit is connected to the bottom end of the spindle via a reverse thread. A nose tube is fitted around the outside of the spindle. A drill sleeve, fitted around the drill bit, is connected to the lower end of the nose tube via a flange. The drill sleeve passes through a hole in a drill template fixed to the workpiece, allowing the drill bit to drill a hole in the workpiece. A drilling force sensor is installed between the nose tube and the drill template to acquire drilling force and torque signals generated during the drilling process.

[0005] The rotary motor and feed motor drive the gearbox, thereby driving the main shaft to perform a combined rotation and feed motion. The upper end of the nose tube is connected to the lower end of the gearbox.

[0006] The upper end of the gearbox is connected to a bushing to prevent dust from entering and affecting the rotation of the main shaft.

[0007] The drilling force sensor is installed between the drill bushing and the nose tube to collect the drilling force and torque signals of the drill bushing.

[0008] The drilling force sensor is installed on the nose tube to collect drilling force and torque signals from the nose tube.

[0009] Among them, the drilling force sensor is a quartz pressure sensor or a quartz strain sensor.

[0010] The drill bushing has a protrusion in the middle, which is fixed to the drill template by a stop nut.

[0011] The drilling force sensor collects drilling force and torque signals, which are then sent to the signal processing module to convert the actual drilling force or torque value. The module then adjusts the speed of the rotary motor and the feed motor according to the magnitude of the actual drilling force or torque value.

[0012] The signal processing module includes a charge amplifier and a controller. The drilling force and torque signals collected by the drilling force sensor are first amplified by the charge amplifier and then sent to the controller for conversion of the actual drilling force or torque value.

[0013] The present invention also provides a method for applying the signals acquired by the drilling force signal acquisition system during the automatic feed drilling process. During the drilling process, if the actual drilling force or torque value changes drastically, the operation is stopped and the drill bit is checked for damage. If the actual drilling force or torque value does not change drastically, a threshold is set. When the actual drilling force or torque value exceeds the threshold, the spindle speed is reduced.

[0014] Beneficial effects: The present invention has the following advantages: 1. The present invention installs the drilling force sensor between the nose tube and the drill template to directly collect the drilling force signal and torque signal generated by the automatic feed drill during the hole making process. There is no need to use additional force measuring equipment and tooling fixtures. The structure is simple, the operation is convenient, and the cost is also saved.

[0015] 2. The signal processing module adjusts the speed of the automatic feed drill spindle according to the actual drilling force and torque values ​​collected by the sensor, and monitors the operation in real time. It is suitable for drilling holes in both single-layer and multi-layer aerospace materials.

[0016] 3. When the actual drilling force and torque values ​​change drastically, it indicates that the drill bit is damaged. The controller sends a stop command, which is amplified by the charge amplifier and then stops the feed of the automatic feed drill spindle, thus improving the safety of the operation. Attached Figure Description

[0017] Figure 1 This is a schematic diagram of the system structure of the present invention;

[0018] Figure 2 This is a schematic cross-sectional view of the system of the present invention;

[0019] Figure 3 This is a diagram illustrating the drilling force transmission process of the present invention.

[0020] Figure 4This is a diagram illustrating the torque transmission process of the present invention;

[0021] Figure 5 This is a diagram of the actual drilling force signal collected by the system of the present invention during operation;

[0022] Figure 6 This is a graph showing the actual torque value signal collected by the system of the present invention during operation. Detailed Implementation

[0023] The technical solution of the present invention will be described in detail below with reference to the embodiments and accompanying drawings.

[0024] like Figure 1 As shown, the automatic feed drilling system for acquiring drilling force signals during the drilling process provided by the present invention includes an automatic feed drill, a drilling force sensor, and a signal processing module.

[0025] The automatic feed drill includes a spindle 9 that performs a combined rotation and feed motion. A drill bit 11 is connected to the bottom of the spindle 9 via a reverse thread. A nose tube 8 is fitted around the outside of the spindle 9. A drill sleeve 12 is fitted around the outside of the drill bit 11. The drill sleeve 12 has a protrusion in the middle and is fixed to the drill template 4 by a stop nut 13. The lower part of the drill sleeve 12 passes through the hole in the drill template 4, allowing the drill bit 11 to drill a hole in the workpiece 14. The drill template 4 is fixed to the workpiece 14 by a stud nut 5. A bushing 6 is fitted on the upper end of the spindle 9 to prevent dust and other debris from entering the spindle 9 and causing errors during the feed motion of the spindle 9.

[0026] There are two installation methods for the drilling force sensor 3 of this invention. The first method is as follows: Figure 2 As shown, the drilling force sensor 3 is installed between the drill bushing 12 and the nose tube 8 to collect the drilling force and torque signals of the drill bushing 12. The upper end of the drilling force sensor 3 is connected to the lower end of the nose tube 8 via a flange 10. The upper end of the drill bushing 12 has a platform with a threaded hole, and the lower end of the drilling force sensor 3 is connected to the upper platform of the drill bushing 12 via screws. Alternatively, the drilling force sensor 3 can be directly installed on the nose tube 8 to collect the drilling force and torque signals of the nose tube 8. The lower end of the nose tube 8 is connected to the upper platform of the drill bushing 12 via a flange 10. The drilling force sensor 3 is either a quartz pressure sensor or a quartz strain sensor, and its wiring is a side-mounted cable.

[0027] The spindle 9 performs a combined rotational and feed motion in the following ways: the gearbox 7 is driven by the rotary motor 1 and the feed motor 2, which in turn drive the spindle 9 to perform a combined rotational and feed motion; or the gearbox 7 is driven by the rotary pneumatic motor and the feed pneumatic motor, which in turn drive the spindle 9 to perform a combined rotational and feed motion. The upper end of the nose tube 8 is connected to the lower end of the gearbox 7, and the upper end of the gearbox 7 is connected to the bushing 6 to prevent dust and other debris from entering the spindle 9.

[0028] The signal processing module of the present invention includes a charge amplifier 15 and a controller 16. The drilling force signal and torque signal collected by the drilling force sensor 3 are first amplified by the charge amplifier 15 and then sent to the controller 16.

[0029] like Figure 3 As shown, taking the rotary motor 1 and feed motor 2 driving the spindle 9 in differential mode through the gearbox 7 to achieve feed motion as an example, during the hole-making process, part of the drilling force is transmitted sequentially through the drill bit 11 to the spindle 9, the gearbox 7 housing, and the nose tube 8; part of the drilling force is transmitted through the gearbox 7 to the nose tube 8. Therefore, after the drill bit 11 makes stable contact with the workpiece 14, the drilling force transmission process is as follows: drill bit 11 → spindle 9 → gearbox 7 → nose tube 8 → flange 10 → drill sleeve 12 → stop nut 13 → drill template 4 → stud nut 5 → workpiece 14.

[0030] When the drilling force sensor 3 is installed between the drill sleeve 12 and the nose tube 8, it collects the drilling force of the drill sleeve 12. This drilling force is equal to the drilling force of the drill bit 11 on the workpiece 14 being processed. Therefore, it can effectively characterize the actual drilling force signal in the hole-making process.

[0031] When the drilling force sensor 3 is installed at any position on the nose tube 8, it collects the drilling force on the nose tube 8. The drilling force is equal to the drilling force on the drill bit 11. Therefore, it can effectively characterize the actual drilling force signal in the hole making process.

[0032] like Figure 4 As shown, the rotary motor 1 drives the spindle 9 to rotate at a speed of n1 via the gearbox 7. The torque transmission process generated by this motion is as follows: drill bit 11 → spindle 9 → gearbox 7 → nose tube 8 → flange 10 → drill sleeve 12 → stop nut 13 → drill template 4 → stud nut 5 → workpiece 14.

[0033] This invention also provides a method for applying signals acquired by a drilling force signal acquisition system during automatic feed drilling. The signals acquired by the drilling force sensor 3 are processed by a charge amplifier 15 and then transmitted to a controller 16 via a data transmission cable for conversion of actual drilling force and torque values. The actual drilling force and torque values ​​are displayed on a host computer, enabling real-time monitoring of the drilling force and torque values. The controller 16 converts the signals transmitted from the charge amplifier 15 to obtain the actual drilling force and torque values. Specifically, the process is as follows: Let F be the triaxial force signal related to the drilling force amplified by the charge amplifier 15. x ', F y 'and F z The amplified torque signal is M. z After conversion, the three-dimensional force values ​​Fx, Fy, and Fz are compared with F... x ', F y 'and Fz The following relationship exists:

[0034] F x =k1F x '+b1 (1.1);

[0035] F y =k2F y '+b2 (1.2);

[0036] F z =k3F z '+b3 (1.3);

[0037] The converted moment value M z With M z The following relationship exists:

[0038] M z =k4M z '+b4(1.4);

[0039] In Example 1, when the spindle 9 performs hole-making operations at a speed of 1000 rpm and a feed rate of 0.03 mm / r, the drilling force sensor 3 collects stable drilling force and torque signals in real time. When unexpected situations such as tool breakage occur, the host computer monitors the actual drilling force value and detects a jump, promptly responding with spindle retraction. If the actual drilling force value does not jump but increases slowly with the increase of tool wear, a drilling force threshold is set. Assuming 95% is the safe value, if the threshold is set to 1000 N, then the safe value is equal to... When the actual drilling force reaches 950N, the host computer sends a control command to drive the rotary motor 1 and the feed motor 2, which in turn drive the spindle 9 through the gearbox 7. This causes the feed rate of the spindle 9 to decrease by a certain percentage. In this embodiment, the given percentage is 10%, so the feed rate of the spindle 9 decreases to 0.027mm / r. As the feed rate of the spindle 9 decreases, the drilling force on the spindle 9 also decreases slowly. Therefore, the actual drilling force can be kept within a safe range, avoiding unexpected situations such as tool breakage due to the actual drilling force exceeding the threshold. Figure 5 The image shows a signal diagram of the actual drilling force value collected by the system of the present invention during operation. Based on actual processing experience, the maximum actual range of drilling force is 3000 N, and the maximum actual range of torque is 20 N·m.

[0040] In Example 2, when the spindle 9 performs hole-making operations at a speed of 800 rpm and a feed rate of 0.03 mm / r, the drilling force sensor 3 collects stable drilling force and torque signals in real time. When unexpected situations such as tool breakage occur, the host computer monitors the actual torque value and detects a jump, promptly responding with spindle retraction. If the actual torque value does not jump but increases slowly with increasing tool wear, a torque threshold is set. Assuming 95% is the safety value, for example, if the torque threshold is set to 3.8 N·m, then the safety value is 3.6 N·m. When the actual torque signal value reaches 3.61 N·m, the host computer sends a control command to drive the rotary motor 1 and the feed motor 2, which in turn drive the spindle 9 through the gearbox 7. This causes the feed rate of the spindle 9 to decrease by a certain percentage. In this embodiment, the given percentage is 10%, so the feed rate of the spindle 9 decreases to 0.027 mm / r. As the feed rate of the spindle 9 decreases, the torque borne by the spindle 9 also decreases slowly. Therefore, the actual torque value can be kept within a safe range, avoiding unexpected situations such as tool breakage due to the actual torque value exceeding the threshold. Figure 6 The image shown is a graph of the actual torque value signal collected by the system of the present invention during operation.

[0041] After each machining operation is completed, the controller 16 will record the operation time t of this hole-making operation in real time. d The data is stored in a Flash chip. If the same tool is used for hole drilling, assuming the first drilling time is t... d1 The second processing time is t. d2 ..., if machining continues until the tool becomes unusable, then the tool's service life L... tc for:

[0042]

[0043] This recording method enables health monitoring of drill bit lifespan.

[0044] Drilling force is a crucial signal for judging the machining status. It can be used to monitor the stability of the drilling force signal in real time during hole making, preventing unexpected situations such as tool breakage. It can also adjust the speed of the automatic feed drill spindle according to the actual drilling force and torque values, making it suitable for hole making of various aerospace materials. The system and method provided by this invention directly collect the drilling force and torque signals generated by the automatic feed drill during hole making, eliminating the need for additional force measuring equipment and tooling fixtures. It has a simple structure, is easy to operate, and saves costs. It provides real-time monitoring of the operation, responds promptly to sudden changes, prepares data for adaptive process parameter adjustment in hole making of aerospace laminated materials, and monitors the health of the drill bit life.

Claims

1. A system for collecting drilling force signals in an automatic feed drilling process, characterized in that The system includes an automatic feed drill and a drilling force sensor. The automatic feed drill includes a spindle (9) that performs a combined rotation and feed motion. The bottom end of the spindle (9) is connected to a drill bit (11) via a reverse thread. The spindle (9) is fitted with a nose tube (8), and the drill bit (11) is fitted with a drill sleeve (12). The lower end of the nose tube (8) is connected to a drilling force sensor (3) via a flange (10). The lower end of the drilling force sensor (3) is connected to the upper end of the drill sleeve (12). The drill sleeve (12) passes through the hole of the drill template (4) fixed on the workpiece (14), so that the drill bit (11) drills a hole in the workpiece (14). The drilling force sensor (3) is used to collect the drilling force signal and torque signal of the drill sleeve (12).

2. The automatic feed drilling force signal acquisition system according to claim 1, characterized in that, The rotary motor (1) and the feed motor (2) drive the gearbox (7), thereby driving the main shaft (9) to perform a combined rotation and feed motion. The upper end of the nose tube (8) is connected to the lower end of the gearbox (7).

3. The automatic feed drilling force signal acquisition system according to claim 1 is characterized in that, The upper end of the gearbox (7) is connected to a bushing (6) to prevent dust from entering and affecting the rotation of the main shaft (9).

4. The automatic feed drilling force signal acquisition system according to claim 1, characterized in that, The drilling force sensor (3) is a quartz pressure sensor or a quartz strain sensor.

5. The automatic feed drilling force signal acquisition system according to claim 1, characterized in that, The drill bushing (12) has a protrusion in the middle and is fixed to the drill template (4) by a stop nut (13).

6. The automatic feed drilling force signal acquisition system according to claim 1, characterized in that, The drilling force sensor (3) collects the drilling force signal and torque signal and sends them to the signal processing module to convert the actual drilling force or torque value. The rotation speed of the rotary motor (1) and the feed motor (2) is adjusted according to the magnitude of the actual drilling force or torque value.

7. The automatic feed drilling force signal acquisition system according to claim 6, characterized in that, The signal processing module includes a charge amplifier (15) and a controller (16). The drilling force signal and torque signal collected by the drilling force sensor (3) are first amplified by the charge amplifier (15) and then sent to the controller (16) for conversion of the actual drilling force or torque value.

8. A method for applying the signal acquired by the drilling force signal acquisition system during automatic feed drilling as described in claim 1, characterized in that, If the actual drilling force or torque value changes drastically during the drilling process, the operation is stopped and the drill bit (11) is checked for damage. If the actual drilling force or torque value does not change drastically, a threshold is set. When the actual drilling force or torque value exceeds the threshold, the spindle speed (9) is reduced.

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