Electrical discharge ultrasonic assisted milling device and method

Abstract

The application discloses an electric spark ultrasonic auxiliary milling device, which comprises a rack, a cutting module and an electric spark generating module installed on the rack; the cutting module comprises a cutter, an ultrasonic vibration module and a driving module; the driving module comprises a main shaft box capable of moving in a vertical direction; the main shaft box is rotationally connected with a main shaft at the bottom end; the main shaft is capable of rotating under the driving of a power element; the ultrasonic vibration module is installed on the main shaft; the ultrasonic vibration module is used for driving the cutter to reciprocate in the vertical direction; the electric spark generating module is installed on the main shaft box and is used for periodically discharging the workpiece. The cutter is driven in a vibration mode; the discharge electric needle is used for discharging the workpiece surface when the cutter is driven to move away from the workpiece surface; the cutter and the discharge electric needle are not too close for a long time, so that the discharge electric needle is prevented from transferring the electric discharge to the cutter and damaging the cutter.

Description

TECHNICAL FIELD

[0001] The application belongs to the technical field of electric spark machining equipment, and particularly relates to a milling machining device and method assisted by electric spark and ultrasonic waves. BACKGROUND

[0002] Milling machining machines are generally used for milling machining of workpieces or milling machining or polishing of surfaces of workpieces, and generally, rotary motion of a milling cutter is main motion, and movement of the workpiece and the milling cutter through a planar moving device is feeding motion. During machining, the milling cutter rotates at high speed and processes the outer surface of the workpiece according to a predetermined path; however, the workpiece surface suffers great resistance during cutting, which not only causes great wear of the milling cutter, but also makes cutting machining difficult and hard to cut off.

[0003] A milling cutter and milling machine assisted by ultrasonic electric spark are disclosed in Chinese Patent No. CN212191604U, which comprises a cutter body, a milling blade group and a discharge electrode group are arranged at a milling end of the cutter body, the discharge electrode group discharges on a workpiece to be processed through air as a medium, and the workpiece to be processed is connected with a charging device, so that the charging device, the discharge electrode group and the workpiece to be processed form a loop, the electrode discharges to break the gap between the discharge electrode group and the workpiece to be processed to generate high temperature, so that the surface properties of the workpiece to be processed are changed, the surface of the workpiece to be processed is softened, a denatured layer easy to cut is generated, cutting is facilitated, and the milling blade group is not worn.

[0004] In the above-mentioned Chinese patent, the discharge electrode group is arranged at the end of the cutter, the discharge electrode group and the workpiece to be processed form a loop, and electric sparks generated by the discharge of the electrode group hit the surface of the workpiece to be processed, so that high temperature is generated on the surface of the workpiece to be processed, the properties of the workpiece to be processed are changed, and the workpiece to be processed is cut off. However, since the cutter itself is mostly made of metal, and the discharge electrode group is installed at the end of the cutter, the electric sparks generated by the discharge electrode group hit the surface of the workpiece to be processed, and the electric sparks are transmitted to the cutter, which affects the properties of the cutter and the cutting of the workpiece to be processed. SUMMARY

[0005] The application aims to provide a milling machining device and method assisted by electric spark and ultrasonic waves.

[0006] In a first aspect, the present invention provides an ultrasonic-assisted electrical discharge machining (EDM) milling apparatus, comprising a frame, a worktable, and a cutting module and an EDM generation module mounted on the frame; characterized in that: the worktable is mounted on the frame for clamping a workpiece; the cutting module includes a cutting tool, an ultrasonic vibration module, an ultrasonic power supply module, and a drive module; the drive module includes a spindle housing capable of vertical movement; a spindle is rotatably connected to the bottom end of the spindle housing; the spindle is capable of rotating under the drive of a power element; the ultrasonic vibration module is mounted on the spindle; the cutting tool is mounted at the bottom end of the ultrasonic vibration module; the ultrasonic vibration module is used to drive the cutting tool to reciprocate vertically; the EDM generation module is mounted on the spindle housing for periodically discharging the workpiece.

[0007] The ultrasonic power supply module includes a permanent magnet and an inductor coil; the permanent magnet is fixed to the spindle box; the inductor coil is fixed on the spindle; the inductor coil and the permanent magnet are positioned in the axial direction of the spindle; as the inductor coil rotates with the spindle, it cuts the magnetic field lines of the permanent magnet, generating an induced current to power the ultrasonic vibration module.

[0008] During operation, the rotating tool cuts the workpiece, while the electrical discharge module periodically discharges the workpiece. The ultrasonic vibration module drives the tool to perform periodic up-and-down reciprocating motion. The cycle of the tool's up-and-down reciprocating motion is equal to the discharge cycle of the electrical discharge module. Whenever the tool reaches the position furthest from the workpiece, the electrical discharge module discharges the workpiece, ensuring that the tool is separated from the workpiece each time the electrical discharge module discharges.

[0009] Preferably, the ultrasonic power supply device further includes a support rod and a coil base; the top of the vertically arranged support rod is fixed to the spindle box. A permanent magnet is fixedly connected to the bottom end of the support rod. The permanent magnet is fan-shaped, with its center on the axis of the spindle. The coil base is fixed to the spindle. An inductor coil is mounted on the coil base.

[0010] Preferably, the ultrasonic vibration module includes an ultrasonic transducer and an ultrasonic amplitude transformer. The ultrasonic transducer is fixed to the bottom of the coil base; the ultrasonic amplitude transformer is mounted on the ultrasonic transducer. A cutting tool is fixedly connected to the bottom end of the ultrasonic amplitude transformer.

[0011] Preferably, the ultrasonic vibration module has an amplitude of 4.37 μm and a vibration frequency of 25.34 kHz.

[0012] Preferably, during operation, the distance between the tip of the discharge needle and the workpiece is 0.01-0.05 mm.

[0013] Secondly, a milling method using an electrical discharge ultrasonic-assisted milling device includes the following steps:

[0014] Step 1: Mount the workpiece to be processed on the worktable.

[0015] Step 2: Set the machining path of the tool.

[0016] Step 3: Adjust the distance between the discharge terminal of the EDM module and the surface of the workpiece to the preset distance.

[0017] Step 4: The spindle drives the cutter and inductor coil to rotate; the rotating inductor coil generates current by cutting the magnetic field lines on the permanent magnet, which powers the ultrasonic transducer. The ultrasonic transducer drives the cutter to perform periodic up-and-down reciprocating motion.

[0018] Step 5: The cutting tool mills the workpiece along the machining path. During the milling process, whenever the cutting tool reaches the position furthest from the workpiece under the drive of the ultrasonic transducer, the electrical discharge module discharges electricity onto the workpiece.

[0019] The beneficial effects of this invention are:

[0020] 1. This invention involves a tool undergoing periodic up-and-down reciprocating motion; simultaneously, an electrical discharge module performs periodic discharges. The cycle of the tool's up-and-down reciprocating motion is equal to the discharge cycle of the electrical discharge module. Whenever the tool reaches the position furthest from the workpiece, the electrical discharge module discharges onto the workpiece, ensuring that the tool is separated from the workpiece during each discharge. This avoids damage to the tool caused by insufficient clearance between the tool and the discharge needle, which would otherwise be transmitted to the tool during the discharge.

[0021] 2. The tool of the present invention uses vibration to mill the workpiece; during each vibration milling process, the tool moves away from the milled surface of the workpiece; during this movement, the gap between the tool and the workpiece is increased, which facilitates the entry of cutting fluid into the gap, carries out the chips generated during the machining process, and reduces the impact of the chips on the tool. Attached Figure Description

[0022] Figure 1 This is a schematic diagram of the overall structure of the present invention.

[0023] Figure 2 This is a schematic diagram showing the position of the cutting tool and the discharge needle during milling in this invention.

[0024] The components are: 1. Frame; 2-1. Clamping base; 2-2. First slide assembly; 2-3. Second slide assembly; 3-1. Cutting tool; 3-2. Ultrasonic cutter holder; 3-3. Spindle box; 4-1. Support rod; 4-2. Permanent magnet; 4-3. Ultrasonic transducer; 4-4. Coil base; 5-1. Discharge needle; 5-2. Industrial robot. Detailed Implementation

[0025] The present invention will be further described below with reference to the accompanying drawings.

[0026] like Figure 1 As shown, an ultrasonic-assisted EDM milling apparatus includes a frame 1, a cutting module, a worktable, and an EDM generating module mounted on the frame 1. The worktable includes a displacement drive mechanism and a clamping base 2-1. The displacement drive mechanism includes a first slide assembly 2-2 and a second slide assembly 2-3. The first slide assembly 2-2 includes a first guide rail, a first slider, and a first drive assembly. The first guide rail is fixed to the frame 1. The first slider and the first guide rail form a sliding pair. The first drive assembly includes a first motor and a first lead screw. The first motor is fixed to the guide rail; the first lead screw is fixedly connected to the output shaft of the first motor; the first lead screw and the first slider form a sliding pair. The second slide assembly 2-3 is mounted on the first slider. The second slide assembly 2-3 includes a second guide rail, a second slider, and a second drive assembly. The second guide rail is fixedly connected to the first slider, and its length direction is along the width direction of the frame 1 and perpendicular to the sliding direction of the first slider. The second slider and the second guide rail form a sliding pair. The clamping base 2-1 is fixedly connected to the second slider. The second drive assembly includes a second lead screw and a second motor. The second motor is fixed on the second slide rail; the second lead screw is fixed to the output shaft of the second motor. The second lead screw and the second slide block form a threaded pair.

[0027] The cutting module includes a tool 3-1, an ultrasonic power supply module, an ultrasonic vibration module, and a drive module. The drive module includes a spindle head 3-3 and an ultrasonic tool holder 3-2. The spindle head 3-3 moves vertically. A spindle is rotatably connected to the bottom of the spindle head 3-3; the spindle can rotate under the drive of the power element. The ultrasonic tool holder 3-2 is fixedly connected to the spindle. During machining, the spindle speed in the spindle head is 3000 r / min, and the feed rate per tooth is 5–15 μm.

[0028] The ultrasonic vibration module includes an ultrasonic transducer and an ultrasonic amplitude transformer. The ultrasonic power supply module includes a support rod 4-1, a permanent magnet 4-2, an inductor coil, and a coil base 4-4. The top of the support rod 4-1 is fixedly connected to the spindle box 3-3. The permanent magnet (4-2) is fixedly connected to the bottom of the support rod 4-1. The permanent magnet (4-2) is fan-shaped, with its center on the axis of the spindle. The coil base 4-4 is fixedly connected to the bottom of the ultrasonic scalpel handle 3-2 and rotates within the fan-shaped area of ​​the permanent magnet 4-2 driven by the spindle. The inductor coil is wrapped around the coil base 4-4. The inductor coil is used to cut the magnetic induction lines on the permanent magnet 4-2, thereby providing electrical energy to the ultrasonic transducer. The ultrasonic transducer 4-3 and the ultrasonic amplitude transformer are fixed sequentially to the bottom of the coil base. The ultrasonic transducer 4-3 is used to convert the input electrical energy into mechanical energy; it generates reciprocating vibration in the vertical direction and transmits it to the ultrasonic amplitude transformer. The ultrasonic amplitude transformer is used to adjust the vibration amplitude generated by the ultrasonic transducer 4-3. The cutting tool 3-1 is mounted at the bottom of the ultrasonic amplitude transformer. Cutting tool 3-1 is a PCD end mill with a length of 100mm, a diameter of 12mm, a rake angle of 0°, a clearance angle of 6°, a cutting edge radius of 0.1mm, a cutting edge diameter of 12mm, and a cutting edge length of 45mm. During machining, the ultrasonic amplitude transformer drives the cutting tool 3-1 to an amplitude of 4.37μm, with the vibration frequency controlled at approximately 25.34kHz. The radial cutting depth of cutting tool 3-1 is 0.15mm per minute, and the axial cutting depth is 1.5mm per minute. The ultrasonic vibration module drives the cutting tool 3-1 to perform periodic up-and-down reciprocating motion. When the cutting tool 3-1 reaches its furthest position from the workpiece, the distance between the cutting tool 3-1 and the workpiece surface increases, facilitating the entry of coolant into the machining area to remove machining residue and preventing the formation of built-up edge.

[0029] The electrical discharge machining (EDM) module includes a discharge needle 5-1, a distance sensor, an industrial robot 5-2, and a charging device. The base of the industrial robot 5-2 is fixedly connected to the spindle box 3-3. Both the discharge needle 5-1 and the distance sensor are located at the end of the industrial robot 5-2. The distance sensor is used to detect the distance from the tip of the discharge needle 5-1 to the surface of the workpiece, ensuring that the distance between the tip of the discharge needle 5-1 and the workpiece is set at 0.01-0.05 mm. The industrial robot 5-2 uses the IRB1010 model. The distance sensor uses the OM20-P0026.HH.YUN model. The charging device supplies power to the discharge needle. The charging device is existing technology and will not be described in detail here.

[0030] like Figure 1 and 2As shown, during use, the tip of the discharge needle 5-1 discharges, breaking down the gap between the discharge needle 5-1 and the workpiece, generating high temperatures on the workpiece surface. This alters the surface properties of the workpiece, softening it and creating an easily machinable modified layer that is easier to remove and less likely to damage the tool 3-1. Simultaneously, when milling the workpiece surface, the tool 3-1 employs vibration milling. When the tool 3-1 reaches its furthest position from the workpiece, it avoids the electrical sparks generated by the discharge needle 5-1 being transmitted to the tool 3-1, thus preventing damage.

[0031] The milling method of the ultrasonic-assisted electrical discharge machining device includes the following steps:

[0032] Step 1: Control the temperature of the laboratory where the device is located at 20±0.1℃, the humidity at 35±5%, and the cleanliness at or above Class 1000; reset the clamping base 2-1 using the first slide assembly 2-2 and the second slide assembly 2-3; install the workpiece to be processed on the clamping base 2-1.

[0033] Step 2: Adjust the position of the workpiece held by the clamping base 2-1 by manipulating the first slide assembly 2-2 and the second slide assembly 2-3; manipulate the cutting tool 3-1 to complete the tool setting of the workpiece.

[0034] Step 3: Set the machining trajectory of the tool 3-1, and the running trajectory of the first slide assembly 2-2 and the second slide assembly 2-3 to drive the workpiece; thereby machining the workpiece to form the curved surface shape of the tenon.

[0035] Step 4: Control the industrial robot 5-2 to move the discharge needle 5-1 to the milling position of the tool 3-1; at the same time, the tip of the discharge needle 5-1 is at a preset distance from the processing surface of the workpiece.

[0036] Step 5: Start the spindle box 3-3. The spindle of the spindle box 3-3 rotates at a speed of 3000 r / min. The spindle drives the coil base 4-4 to rotate via the ultrasonic stalk 3-2. The inductor coil on the coil base 4-4 generates electrical energy by cutting the magnetic induction lines on the permanent magnet 4-2, thereby activating the ultrasonic transducer. The ultrasonic transducer 4-3 converts the input electrical energy into mechanical energy that reciprocates vertically, and amplifies the amplitude acting on the cutter 3-1 through the ultrasonic amplitude transformer.

[0037] Step Six: Control the cutting tool 3-1 to mill the workpiece along the machining path. During milling, whenever the cutting tool 3-1 reaches the position furthest from the workpiece under the drive of the ultrasonic vibration module, the electrical discharge module discharges the workpiece; the discharge needle 5-1 releases the electrical energy in the capacitor, discharging the workpiece surface to change its properties, softening the surface and generating an easily machinable modified layer, facilitating the removal of the workpiece. Simultaneously, the cutting tool 3-1 moves away from the workpiece. The gap between the cutting tool 3-1 and the workpiece surface increases, allowing cutting fluid to enter the gap and carry away the chips generated during machining. Meanwhile...

[0038] Step 7: Close all modules and remove the workpiece from the clamping base 2-1.

Claims

1. A milling method using an electrical discharge ultrasonic-assisted milling apparatus, characterized in that: The ultrasonic-assisted EDM milling device includes a frame (1), a worktable, and a cutting module and an EDM generation module mounted on the frame (1). The worktable is mounted on the frame (1) and is used to clamp the workpiece. The cutting module includes a cutting tool (3-1), an ultrasonic vibration module, an ultrasonic power supply module, and a drive module. The drive module includes a spindle box (3-3) that can move in the vertical direction. The bottom end of the spindle box (3-3) is rotatably connected to a spindle. The spindle can rotate under the drive of a power element. The ultrasonic vibration module is mounted on the spindle. The cutting tool (3-1) is mounted on the bottom end of the ultrasonic vibration module. The ultrasonic vibration module is used to drive the cutting tool (3-1) to reciprocate in the vertical direction. The EDM generation module is mounted on the spindle box (3-3) and is used to perform periodic discharge treatment on the workpiece. The ultrasonic power supply module includes a permanent magnet (4-2) and an inductor coil; the permanent magnet (4-2) is fixed to the spindle box (3-3); the inductor coil is fixed on the spindle; the inductor coil and the permanent magnet (4-2) are positioned in the axial direction of the spindle; as the inductor coil rotates with the spindle, it cuts the magnetic field lines of the permanent magnet (4-2) to generate an induced current, which powers the ultrasonic vibration module. The ultrasonic power supply module also includes a support rod (4-1) and a coil base (4-4); the top of the vertically arranged support rod (4-1) is fixed to the spindle box (3-3); a permanent magnet (4-2) is fixedly connected to the bottom end of the support rod (4-1); the permanent magnet (4-2) is fan-shaped and its center is on the axis of the spindle; the coil base (4-4) is fixed to the spindle; and an inductor coil is installed on the coil base (4-4). The electric spark generating module includes a discharge needle (5-1), a distance sensor, an industrial robot (5-2), and a charging device; the base of the industrial robot (5-2) is fixedly connected to the spindle box (3-3); the discharge needle (5-1) and the distance sensor are both located at the end of the industrial robot (5-2); the charging device is fixed on the frame (1); the industrial robot (5-2) is used to drive the discharge needle (5-1) to the cutting position of the workpiece; During operation, the rotating tool (3-1) cuts the workpiece, while the electrical discharge module periodically discharges the workpiece. The ultrasonic vibration module drives the tool (3-1) to perform periodic up-and-down reciprocating motion. The up-and-down reciprocating motion cycle of the tool (3-1) is equal to the discharge cycle of the electrical discharge module. Whenever the tool (3-1) reaches the position furthest from the workpiece, the electrical discharge module discharges the workpiece, so that the tool (3-1) is separated from the workpiece each time the electrical discharge module discharges. The milling process includes the following steps: Step 1: Mount the workpiece to be processed on the worktable; Step 2: Set the machining path of the tool (3-1); Step 3: Adjust the distance between the discharge terminal of the EDM module and the surface of the workpiece to the preset distance; Step 4: The spindle drives the cutter (3-1) and the inductor coil to rotate; the rotating inductor coil generates current by cutting the magnetic field lines on the permanent magnet (4-2), which powers the ultrasonic transducer; the ultrasonic vibration module drives the cutter (3-1) to perform periodic up-and-down reciprocating motion; Step 5: The cutting tool (3-1) mills the workpiece along the machining path. During the milling process, whenever the cutting tool (3-1) reaches the position furthest from the workpiece under the drive of the ultrasonic vibration module, the electrical discharge module discharges onto the workpiece.

2. The milling method as described in claim 1, characterized in that: The ultrasonic vibration module includes an ultrasonic transducer and an ultrasonic amplitude transformer; the ultrasonic transducer (4-3) is fixed to the bottom of the coil base (4-4); the ultrasonic amplitude transformer is installed on the ultrasonic transducer (4-3); and the cutter (3-1) is fixedly connected to the bottom end of the ultrasonic amplitude transformer.

3. The milling method as described in claim 1, characterized in that: The worktable includes a displacement driving mechanism and a clamping base (2-1) mounted on the displacement driving mechanism; the displacement driving mechanism includes a first slide assembly (2-2) and a second slide assembly (2-3); the first slide assembly (2-2) and the second slide assembly (2-3) are used to drive the clamping base (2-1) to move horizontally.

4. The milling method as described in claim 3, characterized in that: The first slide assembly (2-2) includes a first guide rail, a first slider, and a first drive assembly; the first guide rail is fixed on the frame (1); the first slider and the first guide rail form a sliding pair; the first drive assembly is used to drive the first slider to slide; the second slide assembly (2-3) is mounted on the first slider; the second slide assembly (2-3) includes a second guide rail, a second slider, and a second drive assembly; the second guide rail is fixedly connected to the first slider, and the length direction of the second guide rail is perpendicular to the sliding direction of the first slider; the second slider and the second guide rail form a sliding pair; the second drive assembly is used to drive the second slider to slide.

5. The milling method as described in claim 1, characterized in that: The drive module also includes an ultrasonic scalpel holder (3-2); the ultrasonic scalpel holder (3-2) is fixedly connected to the spindle of the spindle box (3-3); and the coil base (4-4) is fixed to the bottom end of the ultrasonic scalpel holder (3-2).

6. The milling method as described in claim 1, characterized in that: The ultrasonic vibration module has an amplitude of 4.37µm and a vibration frequency of 25.34kHz.

7. The milling method as described in claim 2, characterized in that: During operation, the distance between the tip of the discharge needle (5-1) and the workpiece is 0.01-0.05mm.

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