CN108655569B - A device and method for underwater laser shock dieless incremental forming - Google Patents

Abstract

The invention provides an underwater laser shock die-free incremental forming device and method, which comprise a computer, a laser emitting system, a laser ranging system and a workpiece bearing system, wherein a laser beam emitted by a femtosecond laser in the laser emitting system is reflected to a beam splitter through a plane reflector, then the laser beam passes through a focusing lens and then the focus is positioned at the H position above the surface of a workpiece, the laser beam emitted by the femtosecond laser is reflected to the beam splitter through the plane reflector, then the focus is positioned at the H position through the focusing lens, the computer receives a signal fed back by the laser ranging instrument and then calculates and displays the distance from a light emitting point of the focusing lens to the H position, and the computer controls the H position to be kept at the position 1-1.5 mm above the surface of the workpiece. The invention uses femtosecond laser to break through water induced shock wave as a force source, and uses the nonlinear absorption characteristic of a transparent medium to focused ultrafast laser to ensure that water is used as a restraint layer and an absorption layer, i.e. the restraint layer and the absorption layer are integrated, thereby realizing the gradual forming of a workpiece.

Description

A device and method for underwater laser shock dieless incremental forming

technical field

The invention relates to the fields of laser shock forming and incremental forming, in particular to an underwater laser shock dieless incremental forming device and method.

Background technique

Microplastic forming is an important technology for manufacturing tiny metal parts, and plays an increasingly important role in emerging strategic fields such as industrial sensors, MEMS, and micro-robots. However, conventional microplastic forming requires tiny molds, which not only increases the manufacturing cost and prolongs the product development cycle, but also the friction between the mold and the material, the strict alignment requirements of the tiny concave and convex molds, and the difficulty of demolding after forming, all of which have become the limitations of mold microplastics. Technical barriers to the development of plastic forming. In incremental forming, the size and properties of the resulting target part are mainly determined by the force and relative motion between the tool and the material. This technology has attracted close attention in recent years due to its advantages of "no mold", "rapid prototyping" and easy realization of intelligent manufacturing. However, the shortcomings of incremental forming technology in forming efficiency, geometric accuracy, and surface quality control, as well as the easy occurrence of wrinkles and cracks in the process of forming complex shapes of foils, seriously affect the wide application of this technology. Scholars have proposed many new incremental forming technologies, the more potential ones include: laser-assisted incremental forming, double-sided incremental forming, electromagnetic-assisted incremental forming, and electrothermal-assisted incremental forming. physical properties to improve geometric accuracy and surface quality. In recent years, with the development of laser technology, laser shock forming has received widespread attention. Laser shock forming uses the force effect generated by laser-induced shock waves to achieve plastic deformation of metal foils. This technology can effectively overcome the foil forming process. The springback problem in the material can be improved, and the fatigue strength of the material after forming can be improved.

Chinese patent CN1751837A discloses a method of underwater laser shock forming. In this method, an elastic film belt is arranged in front of the workpiece as an absorption layer. After laser irradiation, the absorption layer is partially vaporized and ionized to form a shock wave. The shock wave is transmitted in the water for a certain distance. Causes plastic deformation on the workpiece surface. Although this method takes into account the inconvenience of directly coating the absorbing layer on the surface of the workpiece, the shock wave pressure transmitted to the surface of the workpiece is reduced due to the attenuation effect of the medium water, and the elastic film belt itself also has a certain attenuation effect on the peak value of the shock wave pressure. , the forming effect is greatly weakened.

SUMMARY OF THE INVENTION

In view of the deficiencies in the prior art, the present invention provides an underwater laser shock dieless progressive forming device and method, which utilizes a femtosecond laser to break down a water-induced shock wave as a force source, and utilizes a transparent medium for the nonlinearity of the focused ultrafast laser. The absorption characteristics make the water both the constraining layer and the absorbing layer, that is, the constraining layer and the absorbing layer are integrated to realize the progressive forming of the workpiece.

The present invention achieves the above technical purpose through the following technical means.

An underwater laser shock dieless progressive forming device, comprising a computer, a laser emission system, a laser ranging system, and a workpiece carrying system;

The workpiece carrying system includes a water tank for accommodating water, a carrying fixture, a three-dimensional moving platform and a three-dimensional moving platform controller; the workpiece is installed in the water tank through the carrying fixture, and is located below the upper surface of the water layer, and the water tank is installed in the three-dimensional moving platform. On the mobile platform, the three-dimensional mobile platform controller is electrically connected with the computer and the three-dimensional mobile platform to control the workpiece to move accurately in the three-dimensional direction according to the processing track;

The laser emission system includes a femtosecond laser controller, a femtosecond laser, a plane mirror, a beam splitter and a focusing lens, the femtosecond laser controller is electrically connected with the computer and the femtosecond laser, and the femtosecond laser emits The first laser beam is reflected to the beam splitter by the plane mirror, and then the focus is located at the H position after the focusing lens, and the H position is located above the surface of the workpiece;

The laser range finder system includes a laser range finder controller and a laser range finder, the laser range finder is electrically connected with the laser range finder controller and a computer, and the second laser beam emitted by the laser range finder passes through After the beam splitter and focusing lens reach the surface of the workpiece, they return to the laser rangefinder according to the original optical path. The computer receives the feedback signal from the laser rangefinder and calculates and displays the distance from the light-emitting point of the focusing lens to the H position, and the computer controls the three-dimensional mobile platform. The movement of the focal point keeps the H position of the focal point at 1-1.5mm above the workpiece surface.

Preferably, the distance between the upper surface of the workpiece and the upper surface of the water layer in the water tank is not less than 5 mm.

Preferably, the bearing jig includes two support blocks, the two support blocks are provided with pressing blocks, and the two ends of the workpiece are respectively placed on the two support blocks, and are respectively pressed by the pressing blocks.

Preferably, the carrying fixture includes two support blocks, and V-shaped block assemblies are provided on opposite side walls of the two support blocks. The V-shaped block assemblies include an upper pressure block and a lower pressure block, and the lower pressure block The upper surface of the upper pressure block is provided with a V-shaped groove, the lower surface of the upper pressure block is provided with a protrusion that matches the V-shaped groove, and the upper surface of the lower pressure block can be closely connected with the lower surface of the upper pressure block. The two ends of the workpiece are respectively placed between the upper pressure block and the lower pressure block of the two V-shaped block assemblies, and both ends of the upper pressure block (801) and the lower pressure block are provided with threaded holes, And connected by bolts.

Preferably, the workpiece carrying system further includes a plexiglass plate, and both ends of the plexiglass plate are placed on the pressing block to control the fluctuation of the water layer above the workpiece.

Preferably, the plexiglass plate is provided with a plurality of exhaust holes.

Preferably, the first laser beam emitted by the femtosecond laser is in a horizontal direction, the angle between the plane mirror and the horizontal direction is 45°, the beam splitter is arranged directly below the plane mirror, and the split mirror The mirror surface of the beam mirror and the mirror surface of the plane mirror are perpendicular to each other, and the focusing lens is placed horizontally below the beam splitter.

A kind of incremental forming method utilizing underwater laser shock without die incremental forming device, comprising the following steps:

Step 1: Use alcohol or acetone to clean the surface of the workpiece to remove oil stains and impurities, and ensure that the surface of the workpiece will not absorb air bubbles after entering the water;

Step 2: Clamp both ends of the workpiece on the bearing fixture to ensure that the upper surface of the workpiece is set horizontally;

Step 3: Pour water into the water tank, put in the plexiglass plate, and the upper surface of the water layer is at least 5mm away from the upper surface of the workpiece;

Step 4: The laser rangefinder sends out the first test laser, and the laser rangefinder controller receives the signal feedback and then inputs it to the computer, and the computer calculates and displays the distance from the light exit point of the focusing lens to the H position;

Step 5: The computer controls the start of the three-dimensional moving platform, moves the workpiece to the initial processing position, and ensures that the focus of the laser beam is located 1-1.5mm above the workpiece surface;

Step 6: Start the femtosecond laser and perform the first impact. After the impact is completed, the workpiece undergoes plastic deformation;

Step 7: Repeat steps 4 to 6, control the three-dimensional mobile platform to move according to the set trajectory through the computer, and induce the workpiece to achieve precise incremental forming after multiple impacts.

Beneficial effects of the present invention:

1) The present invention utilizes the performance that the ultrafast laser can be as short as femtosecond in the time domain and can be focused to the micrometer level in the space domain, which can effectively improve the precision and controllability of moldless microplastic incremental forming;

2) Using ultra-fast laser instead of tool head as the force source, it can realize the incremental forming of metal foil, with a high degree of automation;

3) Compared with conventional laser shock forming, in the present invention, the focus position of the laser beam emitted by the femtosecond laser is maintained at 1-1.5mm above the surface of the workpiece after passing through the focusing lens, so that water can be used as both an absorption layer and a constraining layer. It is inconvenient to apply the absorption layer and update the absorption layer online, and at the same time effectively improve the precision and controllability of moldless microplastic incremental forming.

Description of drawings

FIG. 1 is a schematic structural diagram of an underwater laser shock dieless incremental forming device according to the present invention.

FIG. 2 is a schematic diagram of the principle of femtosecond laser shock incremental forming according to the present invention.

FIG. 3 is a schematic structural diagram of the carrying fixture according to the present invention.

Figure 4 is a top view of the V-block assembly of the present invention.

FIG. 5 is an experimental effect diagram of a specific embodiment of the present invention.

In the picture: 1-femtosecond laser, 2-light guide, 3-plane mirror, 4-beam splitter, 5-focusing lens, 6-laser rangefinder, 7-laser rangefinder controller, 8- Carrying fixture, 801-upper pressing block, 802-lower pressing block, 9-three-dimensional mobile platform, 10-workpiece, 11-water tank, 12-three-dimensional mobile platform controller, 13-computer, 14-femtosecond laser controller, 15 - first laser beam, 16 - plasma, 17 - shock wave, 18 - plexiglass plate, 19 - second laser beam.

Detailed ways

The present invention will be further described below with reference to the accompanying drawings and specific embodiments, but the protection scope of the present invention is not limited thereto.

As shown in FIG. 1 , an underwater laser shock dieless incremental forming device according to the present invention includes a computer 13 , a laser emission system, a laser ranging system, and a workpiece carrying system.

As shown in FIG. 1 , the workpiece carrying system includes a water tank 11 for accommodating water, a carrying fixture 8, a three-dimensional moving platform 9, a plexiglass plate 18 and a three-dimensional moving platform controller 12; the carrying fixture 8 is located in the water tank 11, including two The support block, the two support blocks are provided with pressing blocks, the two ends of the workpiece 10 are respectively placed on the two support blocks, and are respectively pressed by the pressing blocks, and are located below the upper surface of the water layer, and the upper part of the workpiece 10 The distance between the surface and the upper surface of the water layer in the water tank 11 is not less than 5 mm. Both ends of the plexiglass plate 18 are placed on the pressing block to control the fluctuation of the water layer above the workpiece 10 . The plexiglass plate 18 is provided with a plurality of exhaust holes. The water tank 11 is installed on the three-dimensional moving platform 9 , and the three-dimensional moving platform controller 12 is electrically connected with the computer 13 and the three-dimensional moving platform 9 to control the workpiece 10 to move accurately in three-dimensional direction according to the processing track.

As a preferred example, as shown in FIG. 3 and FIG. 4 , the carrier jig 8 includes two support blocks, and V-shaped block assemblies are provided on opposite side walls of the two support blocks, and the V-shaped block assemblies include an upper pressing block 801 and a lower pressing block 802, the upper surface of the lower pressing block 802 is provided with a V-shaped groove, the lower surface of the upper pressing block 801 is provided with a protrusion matched with the V-shaped groove, and the upper The surface can be closely attached to the lower surface of the upper pressure block 801, and the two ends of the workpiece 10 are respectively placed between the upper pressure block 801 and the lower pressure block 802 of the two V-shaped block assemblies. Both ends of the lower pressing block 802 are provided with threaded holes and are fixedly connected by bolts. Foil deformation is prevented by two V-block assemblies.

The laser emission system includes a femtosecond laser controller 14, a light guide tube 2, a femtosecond laser 1, a flat mirror 3, a beam splitter 4 and a focusing lens 5. The femtosecond laser controller 14 is connected to the computer 13 and the femtosecond laser. The second laser 1 is electrically connected, the first laser beam 15 emitted by the femtosecond laser 1 is in a horizontal direction, the angle between the plane reflection mirror 3 and the horizontal direction is 45°, and the beam splitter 4 is arranged on the plane reflection mirror. Directly below 3, the mirror surface of the beam splitter 4 and the mirror surface of the plane mirror 3 are perpendicular to each other, and the focusing lens 5 is placed horizontally below the beam splitter 4. The first laser beam 15 emitted by the femtosecond laser 1 is reflected by the light guide tube 2 through the plane mirror 3 to the beam splitter 4 , and then focused by the focusing lens 5 at 1-1.5 mm above the surface of the workpiece 10 . .

The laser range finder system includes a laser range finder controller 7 and a laser range finder 6, the laser range finder 6 is electrically connected with the laser range finder controller 7 and the computer 13, and the laser range finder 6 emits a second The laser beam 19 reaches the surface of the workpiece 10 through the beam splitter 4 and the focusing lens 5 and returns to the laser range finder 6 according to the original optical path. The distance of the H position, and the computer 13 controls the movement of the three-dimensional moving platform 12 so that the focus position is maintained at 1-1.5 mm above the surface of the workpiece 10 .

The incremental forming method of the underwater laser shock dieless incremental forming device of the present invention comprises the following steps:

Step 1: Clean the surface of the workpiece 10 with alcohol or acetone to remove oil stains and impurities, and ensure that the surface of the workpiece 10 will not absorb air bubbles after it enters the water;

Step 2: flatten the workpiece 10, and clamp both ends on the bearing fixture 8 to ensure that the upper surface of the workpiece 10 is set horizontally;

Step 3: inject water into the water tank 11, put in the plexiglass plate 18, and the upper surface of the water layer is at least 5mm away from the upper surface of the workpiece 10;

Step 4: The laser rangefinder 6 sends out the first test laser, and the laser rangefinder controller 7 receives the signal feedback and then inputs it to the computer 13, and the computer 13 calculates and displays the distance from the light-emitting point of the focusing lens 5 to the H position;

Step 5: The computer 13 controls the three-dimensional moving platform 9 to start, moves the workpiece 10 to the initial processing position, and ensures that the focus of the laser beam is located 1-1.5 mm above the surface of the workpiece 10;

Step 6: start the femtosecond laser 1, perform the first impact, and plastic deformation of the workpiece 10 occurs after the impact is completed;

Step 7: Repeat steps 4 to 6, control the three-dimensional moving platform 9 to move according to the set trajectory through the computer 13, and induce the workpiece 10 to achieve precise incremental forming after multiple impacts.

The working principle of the present invention: As shown in FIG. 2, when the femtosecond laser 1 emits the first laser beam 15, the medium water is instantly broken down to form a high-temperature plasma 16, and at the same time, a compression shock wave 17 with an ultra-high peak pressure is formed on the surrounding medium. , under the action of the shock wave 17, the workpiece 10 undergoes plastic deformation.

In this embodiment, the center wavelength of the femtosecond laser is 800 nm, the maximum energy is 500 μJ, the pulse width is adjustable from 80 fs to 800 fs, the repetition frequency is from 1 Hz to 1 kHz, and the spot diameter of the first laser beam 15 output by the femtosecond laser 1 is 6 mm. , the focal length of the focusing lens 5 is 1000mm, and the sample is 20μm thick aluminum foil. Fig. 5 shows the shape of the pits on the foil when the distances between the focal point of the first laser beam 15 output by the femtosecond laser 1 after passing through the focusing lens 5 and the surface of the foil are 1 mm, 1.5 mm, 2 mm and 2.5 mm respectively In the figure, from top to bottom, it corresponds to the defocus 1-2.5mm. It can be clearly seen that the pits are more obvious when the defocus is 1mm and 1.5mm.

The embodiments are preferred embodiments of the present invention, but the present invention is not limited to the above-mentioned embodiments, and any obvious improvement, replacement or All modifications belong to the protection scope of the present invention.

Claims (8)

1. An underwater laser shock die-free incremental forming device is characterized by comprising a computer (13), a laser emitting system, a laser ranging system and a workpiece bearing system;

the workpiece bearing system comprises a water tank (11) for containing water, a bearing clamp (8), a three-dimensional moving platform (9) and a three-dimensional moving platform controller (12); the workpiece (10) is arranged in a water tank (11) through a bearing clamp (8) and is positioned below the upper surface of a water layer, the water tank (11) is arranged on a three-dimensional moving platform (9), and a three-dimensional moving platform controller (12) is electrically connected with a computer (13) and the three-dimensional moving platform (9) so as to control the workpiece (10) to accurately move in the three-dimensional direction according to a processing track;

the laser emission system comprises a femtosecond laser controller (14), a femtosecond laser device (1), a plane mirror (3), a beam splitter (4) and a focusing lens (5), wherein the femtosecond laser controller (14) is electrically connected with a computer (13) and the femtosecond laser device (1), a first laser beam (15) emitted by the femtosecond laser device (1) is reflected to the beam splitter (4) through the plane mirror (3), then passes through the focusing lens (5) and then is focused at an H position, and the H position is positioned above the surface of a workpiece (10);

the laser ranging system comprises a laser range finder controller (7) and a laser range finder (6), wherein the laser range finder (6) is electrically connected with the laser range finder controller (7) and a computer (13), a second laser beam (19) emitted by the laser range finder (6) returns to the laser range finder (6) according to an original light path after reaching the surface of a workpiece (10) through a beam splitter (4) and a focusing lens (5), the computer (13) calculates and displays the distance from a light emitting point of the focusing lens (5) to an H position after receiving a signal fed back by the laser range finder (6), and the computer (13) controls the movement of a three-dimensional moving platform (9) to enable the H position where a focus is located to be kept at a position 1-1.5 mm above the surface of the workpiece (10).

2. The underwater laser shock die-less incremental forming apparatus according to claim 1, wherein a distance between an upper surface of the workpiece (10) and an upper surface of a water layer in the water tank (11) is not less than 5 mm.

3. The underwater laser shock die-less incremental forming device of claim 1, wherein the carrying clamp (8) comprises two supporting blocks, pressing blocks are arranged on the two supporting blocks, and two ends of the workpiece (10) are respectively placed on the two supporting blocks and are respectively pressed by the pressing blocks.

4. The underwater laser shock die-free incremental forming device of claim 1, wherein the bearing clamp (8) comprises two support blocks, V-shaped block assemblies are arranged on opposite side walls of the two support blocks, each V-shaped block assembly comprises an upper pressing block (801) and a lower pressing block (802), a V-shaped groove is formed in the upper surface of each lower pressing block (802), a protrusion matched with the V-shaped groove is formed in the lower surface of each upper pressing block (801), the upper surface of each lower pressing block (802) can be tightly attached to the lower surface of each upper pressing block (801), two ends of the workpiece (10) are respectively arranged between the upper pressing block (801) and the lower pressing block (802) of the two V-shaped block assemblies, and two ends of each upper pressing block (801) and each lower pressing block (802) are provided with threaded holes and fixedly connected through bolts.

5. The underwater laser shock die-less incremental forming device of claim 3, wherein the workpiece carrying system further comprises a plexiglas plate (18), both ends of the plexiglas plate (18) being placed on the compaction blocks to control water layer fluctuation above the workpiece (10).

6. The underwater laser shock die-less incremental forming device according to claim 5, wherein the organic glass plate (18) is provided with a plurality of vent holes.

7. The underwater laser shock die-free incremental forming device of claim 1, wherein the first laser beam (15) emitted by the femtosecond laser (1) is in a horizontal direction, the included angle between the plane mirror (3) and the horizontal direction is 45 degrees, the beam splitter (4) is arranged right below the plane mirror (3), the mirror surface of the beam splitter (4) is perpendicular to the mirror surface of the plane mirror (3), and the focusing lens (5) is horizontally arranged below the beam splitter (4).

8. A progressive forming method by using the underwater laser shock die-free progressive forming device of any one of claims 1 to 7, characterized by comprising the following steps:

the method comprises the following steps: cleaning the surface of the workpiece (10) by using alcohol or acetone to remove oil stains and impurities, and ensuring that the surface of the workpiece (10) can not absorb bubbles after entering water;

step two: clamping two ends of a workpiece (10) on a bearing clamp (8) to ensure that the upper surface of the workpiece (10) is horizontally arranged;

step three: injecting water into the water tank (11), putting an organic glass plate (18), wherein the upper surface of the water layer is at least 5mm away from the upper surface of the workpiece (10);

step four: the laser range finder (6) sends out first test laser, the laser range finder controller (7) receives signal feedback and then inputs the signal feedback into the computer (13), and the computer (13) calculates and displays the distance from the light emitting point of the focusing lens (5) to the H position;

step five: the computer (13) controls the three-dimensional moving platform (9) to start, moves the workpiece (10) to an initial processing position, and ensures that the focal point of the laser beam is 1-1.5 mm above the surface of the workpiece (10);

step six: starting the femtosecond laser device (1) to carry out first impact, and after the impact is finished, carrying out plastic deformation on the workpiece (10);

step seven: and repeating the fourth step to the sixth step, controlling the three-dimensional moving platform (9) to move according to a set track through the computer (13), and inducing the workpiece (10) to realize accurate incremental forming after multiple times of impact.

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