Laser butt welding device and method for transparent plastic

Abstract

A transparent plastic laser butt welding device and method thereof, the butt welding device includes a laser and a workbench, the workbench is provided with a motion platform and a fixture assembly, the fixture assembly is provided with two butt-welded transparent plastic plates, a heat sink is provided above the butt joint of the plastic plates, the motion platform is provided with a welding head assembly, the two welding heads on the welding head assembly are installed at a certain angle, and the welding heads are connected to the laser via optical fibers. The butt welding method includes the laser emitting two laser beams, the focal points of the two laser beams are both focused on the butt joint of the two butt-welded transparent plastic plates, the plastic absorbs the laser energy and converts it into heat energy, causing a small amount of melting of the plastic at the butt joint, and forming a butt weld after cooling. The present invention realizes laser butt welding of two transparent plastics without coating an absorbent, and has the characteristics of high welding efficiency, high welding strength, beautiful welds, cleanliness and environmental protection, and is suitable for laser butt welding of transparent plastics in high-requirement fields such as food and medical care.

Description

Technical Field

[0001] The invention relates to the field of plastic laser welding, in particular to the field of laser butt welding of transparent plastics. Background Art

[0002] Plastic is a high molecular compound made from monomers through addition or condensation reactions. It is a widely used engineering material due to its excellent characteristics such as light weight, good chemical stability, corrosion resistance, impact resistance and good insulation.

[0003] Most plastic products on the market are made through injection molding. Due to the development of diverse plastic products, it is difficult to meet personalized needs by relying solely on injection molding. Therefore, secondary molding of injection molded plastics is imperative. At present, traditional plastic secondary molding methods mainly include gluing, hot melt welding, hot air welding, ultrasonic welding, friction welding, etc. In the actual production process, traditional plastic secondary molding methods all have their own shortcomings that are difficult to overcome, such as low connection strength, toxic gases, noise, welding stress, etc. In recent years, laser welding has gradually become a very promising plastic welding method due to its advantages such as high welding strength, fast welding efficiency, precision and micro welding, stress-free, clean and environmentally friendly.

[0004] Conventional plastic laser welding (wavelength 800-1000nm) requires the two layers of plastic being welded to contain a light-absorbing layer and a light-transmitting layer. The laser passes through the light-transmitting layer to the light-absorbing layer, where the laser energy is absorbed, achieving the desired weld. However, a large proportion of plastic products on the market have double-layered, light-transmitting layers, making them difficult to weld directly with conventional laser welding.

[0005] Engineers have conducted extensive research on double-layer transparent plastic welding. Patents CN101868495B and CN105440639B disclose a method of adding near-infrared laser absorbers or carbon black to the raw material powder for transparent plastic injection molding. The plastic powder and light-absorbing powder are evenly mixed in a mixing blender, and then injection molded into a plastic product. The light-absorbing powder absorbs the laser energy to achieve the welding effect. Patent CN107379560B discloses a method of applying Clearweld absorber or black paint to the surface of the lower light-transmitting layer. This method also achieves the welding effect by assisting the light-absorbing agent in absorbing the laser energy. Patent CN105968566B discloses a method of using a plastic dissolving agent to dissolve black light-absorbing plastic particles. After the two are mixed, they are stirred to form a viscous plastic dissolving liquid, which is then applied to the surface of the lower transparent layer. The light-absorbing agent achieves the welding effect. The methods disclosed in the above four patents can achieve the welding of double-layer transparent plastics, but will increase the raw material cost of plastic products to a certain extent, and will also affect the appearance of transparent plastic products; in addition, due to the uneven distribution of light-absorbing powder, the quality of the weld will also be uneven. Patent "CN108515703A" discloses a method of utilizing transparent plastic to have a low transmittance to lasers with a wavelength of 1700nm to 2000nm, so that no absorbent is required when welding transparent plastics. However, the method disclosed in this patent can only achieve laser lap welding of transparent plastics, and cannot achieve laser butt welding of transparent plastics. Moreover, the welding speed in the method disclosed in this patent is low, only 2mm / s to 4mm / s. Such a low welding speed is difficult to meet the needs of the rapidly developing market.

[0006] In summary, through the investigation of existing public methods and patents, no laser butt welding method and device that can meet the requirements of transparent plastics has been found, and it is necessary to further develop new methods and new devices. Summary of the Invention

[0007] The purpose of the present invention is to provide a transparent plastic laser butt welding device and method that does not require absorbent coating, has high welding efficiency, high welding strength, beautiful welds, is clean and environmentally friendly, and meets the needs of transparent plastic butt welding in high-requirement fields such as food and medical care, so as to overcome the shortcomings of the existing technology.

[0008] A transparent plastic laser butt welding device designed for this purpose includes a laser and a workbench. The workbench is provided with a motion platform and a fixture assembly for clamping two butt-welded transparent plastic plates. A heat sink is provided above the two butt-welded transparent plastic plates, and the heat sink covers at least the butt-welded parts of the two butt-welded transparent plastic plates. The motion platform is provided with a welding head assembly. The welding head assembly includes two welding heads. The two welding heads are connected to the laser via optical fibers. The laser beam emitted by the laser is transmitted via the optical fibers and passes through the two welding heads respectively. An angle A is formed between the two welding heads so that the relative angle of the two laser beams passing through the two welding heads is 60° to 90°. The focal points of the two laser beams are both focused on the butt-welded parts of the two butt-welded transparent plastic plates.

[0009] The two welding heads are respectively equipped with a focusing lens assembly and a collimating lens assembly to achieve focusing and collimation of the laser beam output by the optical fiber; wherein, the welding head achieves a uniform laser beam spot by adjusting the installation position of the focusing lens assembly, and the spot diameter is 0.4 to 2.0 mm; the welding head assembly also includes a welding head fixing block, and the two welding heads are respectively fixed on the welding head fixing block in an inclined manner. The installation method of the two welding heads can achieve the maximum absorption of laser energy by the plastic at the butt joint of the two butt-welded transparent plastic plates. By precisely controlling the laser power and welding speed, it can be achieved that only a small amount of plastic at the butt joint is melted, while ensuring that the plastic on the upper and lower surfaces is not melted.

[0010] The laser is at least a semiconductor laser, the laser emits a laser beam with a wavelength of 1700nm to 2000nm, the output power of the laser is 30 to 100W, the output power stable fluctuation value is less than 3%, and the beam quality M 2 The factor is less than 1.5.

[0011] The motion platform is at least a three-axis linear motion platform or a multi-joint manipulator motion platform, and the two welding heads respectively realize the execution mechanism of the two-dimensional plane or three-dimensional space curve welding trajectory through the motion platform.

[0012] The tooling fixture assembly includes a tooling base plate, electrically driven or pneumatic upper and lower clamping components, and a horizontal clamping component. The tooling base plate is provided with more than two sliding guide pillars, two clamping cylinders, and a plastic plate support fitting. The clamping cylinder is provided with a pressure plate, which is provided with an opening, and the opening is provided with a transparent heat sink. More than two sliding guide pillars pass through the pressure plate respectively, and the pressure plate is located above the plastic plate support fitting. The pressure plate and the clamping cylinder are connected to enable the pressure plate to move up and down along the sliding guide pillars. The clamping cylinder, pressure plate, and heat sink jointly realize the upper and lower clamping of the two butt-welded transparent plastic plates, so that the clamping cylinder and pressure plate are combined into pneumatic upper and lower clamping components.

[0013] The plastic plate supporting fittings include supporting side plates, supporting flat plates, and elastic parts. The elastic parts are arranged on the supporting flat plates. The supporting flat plates are located on the top of the supporting side plates, and one end of the elastic part is against the inner side of the supporting flat plates, and the other end of the elastic part is against the outer side of the transparent plastic plate. The elastic part realizes horizontal compression of the transparent plastic plates to maintain horizontal compression force between the two butt-welded transparent plastic plates during the welding process, and adjusts the horizontal compression force of the transparent plastic plates by changing the pre-compression force of the elastic part, so that the elastic part and the supporting flat plate are combined into a horizontal compression component.

[0014] The heat sink material is at least quartz glass or sapphire glass. To ensure sufficient heat dissipation efficiency without significantly consuming laser energy, the heat sink has a thermal conductivity greater than 1.0 W / m·K at a temperature of 150-300°C, and an absorptivity of less than 5% for laser beams with a wavelength of 1700nm-2000nm.

[0015] The two butt-welded transparent plastic plates are made of the same plastic or dissimilar plastics.

[0016] A method for laser butt welding of transparent plastics includes the above-mentioned laser butt welding device for transparent plastics, the laser butt welding device for transparent plastics including a laser, a motion platform and a fixture assembly arranged on a workbench, the fixture assembly clamping two butt-welded transparent plastic plates, the two butt-welded transparent plastic plates being provided with heat sinks, the motion platform being at least a three-axis linear motion platform or a multi-joint manipulator motion platform, and a welding head assembly being provided on the motion platform, the welding head assembly including two welding heads, the two welding heads being connected to the laser via optical fibers, the two welding heads being arranged at an angle, an angle A being formed between the two welding heads, and the two welding heads being respectively provided with a focusing lens assembly and a collimating lens assembly.

[0017] The welding method is

[0018] a. Clamp two butt-welded transparent plastic plates in the fixture assembly and adjust the clamping force;

[0019] b. Adjust the angle between the two welding heads on the motion platform, and adjust the installation position of the focusing lens components on the two welding heads respectively.

[0020] c. Start the laser. The laser emits two laser beams, which are transmitted through optical fibers, pass through two welding heads respectively, and then through the heat sink to reach the joint of the two transparent plastic plates. The focus of the two laser beams is focused on the joint of the transparent plastic plates. The polymer inside the plastic moves at high speed under the action of laser energy, converting the laser energy into heat energy, causing a small amount of melting of the plastic at the joint. At the same time, the plastics are fused together under the action of the fixture and form a butt weld after cooling.

[0021] In addition, by selecting the welding process parameters, the temperature of the butt joint of the two transparent plastic plates is precisely controlled to between the glass transition temperature and the thermal decomposition temperature during the welding process, thereby forming a high-strength weld. The welding process parameters include laser power, welding speed and spot diameter.

[0022] The beneficial effects of the present invention are as follows:

[0023] a. Two welding heads are installed at a certain angle on the motion platform. The focus of the two laser beams is focused on the joint of the plastic plates, so that the plastic at the joint absorbs the maximum laser energy;

[0024] b. By optimizing the welding process parameters, the plastic temperature range at the joint is controlled between the glass transition temperature and the thermal decomposition temperature during welding. At the same time, under the action of the fixture, a high-strength weld is formed;

[0025] c. Due to the reasonable spatial distribution of laser energy and the effect of heat sink, the plastic on the upper surface is ensured not to be melted.

[0026] The present invention realizes laser butt welding of two transparent plastics without coating an absorbent, and has the characteristics of high welding efficiency, high welding strength, beautiful welds, cleanliness and environmental protection. It is suitable for laser butt welding of transparent plastics in high-requirement fields such as food and medical care. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] Figure 1 This is a schematic diagram of the three-dimensional structure of a laser butt welding device for transparent plastic according to the first embodiment of the present invention.

[0028] Figure 2 It is a schematic diagram of the three-dimensional structure of the tooling fixture assembly according to the first embodiment of the present invention.

[0029] Figure 3 It is a schematic diagram of the planar structure of the fixture assembly according to the first embodiment of the present invention.

[0030] Figure 4 Schematic diagram of the planar structure of the welding head assembly according to the first embodiment of the present invention.

[0031] Figure 5 This is a structural diagram of two butt-welded transparent plastic plates according to the first embodiment of the present invention.

[0032] In the figure, 1 is a laser, 2 is an optical fiber, 3 is a welding head, 4 is a laser beam, 5 is a heat sink, 6 is a transparent plastic plate, 7 is a workbench, 8 is a moving platform, 8.1 is the first slide, 8.2 is the second slide, 8.3 is the third slide, 9 is a welding head assembly, 10 is a tooling fixture assembly, 11 is a collimating lens assembly, 12 is a focusing lens assembly, 13 is a welding head fixing block, 14 is a tooling base plate, 15 are upper and lower pressing members, 16 is a horizontal pressing member, 17 is a supporting side plate, 18 is a pressure plate, 19 is a sliding guide column, 20 is an elastic member, 21 is a supporting flat plate, 22 is a pressing cylinder, 23 is a plastic plate support fitting, and 24 is a supporting frame. DETAILED DESCRIPTION

[0033] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0034] First embodiment

[0035] See also Figure 1 A laser butt welding device for transparent plastic includes a laser 1 and a workbench 7. The workbench 7 is provided with a motion platform 8 and a fixture assembly 10 for clamping two butt-welded transparent plastic plates 6. A heat sink 5 is provided above the two butt-welded transparent plastic plates 6. The heat sink 5 at least covers the butt-welded parts of the two butt-welded transparent plastic plates 6. The motion platform 8 is provided with a welding head assembly 9. The welding head assembly 9 includes two welding heads 3. The two welding heads 3 are connected to the laser 1 through an optical fiber 2. The laser beam emitted by the laser 1 is transmitted through the optical fiber 2 and passes through the two welding heads 3 respectively. There is an angle A between the two welding heads 3, so that the relative angle of the two laser beams passing through the two welding heads 3 is 60° to 90°, and the focal points of the two laser beams are both focused on the butt-welded parts of the two butt-welded transparent plastic plates 6.

[0036] The laser 1 is at least a semiconductor laser, and the laser 1 emits a laser beam with a wavelength of 1700nm to 2000nm. The output power of the laser 1 is 30 to 100W, the output power fluctuation value is less than 3%, and the beam quality M 2 The factor is less than 1.5.

[0037] The motion platform 8 is a three-axis linear motion platform, and the two welding heads 3 are respectively implemented as a two-dimensional plane actuator through the motion platform 8. The motion platform 8 has a repeatability accuracy of ±0.02mm and is an actuator that implements a two-dimensional plane.

[0038] The motion platform 8 comprises a first slide 8.1, a second slide 8.2 and a third slide 8.3.

[0039] In this embodiment, a rectangular support frame 24 is provided on the workbench 7, and the support frame 24 is provided with a first slide 8.1 and a second slide 8.2; a sliding assembly is provided between the first slide 8.1 and the second slide 8.2, and relative movement is formed between the second slide 8.2 and the first slide 8.1 through the sliding assembly, and the second slide 8.2 is provided with a third slide 8.3, and the second slide 8.2 drives the third slide 8.3 to slide back and forth on the first slide 8.1; in addition, the third slide 8.3 and the second slide 8.2 are slidably matched, and the welding head fixing block 13 is connected to the third slide 8.3, so that the third slide 8.3 drives the two welding heads 3 to slide back and forth on the second slide 8.2 through the welding head fixing block 13.

[0040] The third slide 8.3 is provided with a lifting screw rod, or a lifting guide rail, and a sliding block corresponding to the welding head fixing block 13, so that the two welding heads 3 can be lifted up and down on the third slide 8.3.

[0041] The heat sink 5 is made of at least quartz glass or sapphire glass. To ensure sufficient heat dissipation efficiency without significantly consuming laser energy, the heat sink 5 has a thermal conductivity greater than 1.0 W / m·K at a temperature of 150-300° C., and an absorptivity of less than 5% for laser beams with a wavelength of 1700 nm to 2000 nm.

[0042] See also Figure 2-Figure 3 The fixture assembly 10 includes a fixture base 14, electrically or pneumatically driven upper and lower clamping members 15, and a horizontal clamping member 16. The fixture base 14 is provided with two or more sliding guide posts 19, two clamping cylinders 22, and a plastic plate support fitting 23. The clamping cylinder 22 is provided with a pressing plate 18, which has an opening with a transparent heat sink 5. Two or more sliding guide posts 19 extend through the pressing plate 18, which is located above the plastic plate support fitting 23. The pressing plate 18 and the clamping cylinder 22 are coupled to each other to enable the pressing plate 18 to move up and down along the sliding guide posts 19. A guide sleeve is provided between the pressing plate 18 and the sliding guide post 19 to guide and reduce sliding friction between the pressing plate 18 and the sliding guide post 19. The pressing cylinder 22 , the pressing plate 18 and the heat sink 5 jointly realize the upper and lower pressing of the two butt-welded transparent plastic plates 6 , so that the pressing cylinder 22 and the pressing plate 18 are combined into a pneumatic upper and lower pressing component 15 .

[0043] The plastic plate support fitting 23 includes a support side plate 17, a support flat plate 21, and an elastic member 20. The elastic member 20 is arranged on the support flat plate 21. The support flat plate 21 is located at the top of the support side plate 17, and one end of the elastic member 20 is against the inner side of the support flat plate 21, and the other end of the elastic member 20 is against the outer side of the transparent plastic plate 6. The elastic member 20 realizes the horizontal compression of the transparent plastic plate 6 so as to maintain the horizontal compression force of the two butt-welded transparent plastic plates 6 during the welding process, and adjusts the horizontal compression force of the transparent plastic plate 6 by changing the pre-compression force of the elastic member 20, so that the elastic member 20 and the support flat plate 21 are combined into a horizontal compression component 16.

[0044] In this embodiment, the support plate 21 has a cavity corresponding to the elastic member 20 and the transparent plastic plate 6. The elastic member 20 and the transparent plastic plate 6 are located within the cavity. Two elastic members 20 are used, one end of each elastic member 20 resting against the outside of the two transparent plastic plates 6; the other end of each elastic member 20 rests against the inside of the cavity of the support plate 21. The elastic members 20 serve as compression springs.

[0045] Alternatively, an elastic member 20 is used, the elastic member 20 abuts against the outer side of one transparent plastic plate 6 , and the outer side of the other transparent plastic plate 6 contacts the inner side of the supporting flat plate 21 to laterally press the two transparent plastic plates 6 .

[0046] See also Figure 4 The two welding heads 3 are respectively equipped with a focusing lens assembly 12 and a collimating lens assembly 11 to achieve focusing and collimation of the laser beam output by the optical fiber; wherein, the welding head 3 adjusts the installation position of the focusing lens assembly 12 to achieve a uniform laser beam spot, and the spot diameter is between 0.4 and 2.0 mm, so that the spot diameter can be adjusted within this range; the welding head assembly 9 also includes a welding head fixing block 13, and the two welding heads 3 are respectively fixed on the welding head fixing block 13 in an inclined manner.

[0047] The two butt-welded transparent plastic plates 6 are made of the same plastic or different plastics, including PMMA, ABS, etc.

[0048] See also Figure 5 A method for laser butt welding of transparent plastics, comprising the above-mentioned laser butt welding device for transparent plastics,

[0049] like Figure 1As shown, the laser butt welding device for transparent plastic includes a laser 1, a motion platform 8 and a fixture assembly 10 arranged on a workbench 7, the fixture assembly 10 clamps two butt-welded transparent plastic plates 6, and the two butt-welded transparent plastic plates 6 are provided with heat sinks 5, the motion platform 8 is a three-axis linear motion platform, and a welding head assembly 9 is provided on the motion platform 8, the welding head assembly 9 includes two welding heads 3, the two welding heads 3 are connected to the laser 1 through optical fibers 2, and the two welding heads 3 are tilted, with an angle A between the two welding heads 3, and the two welding heads 3 are respectively installed with a focusing lens assembly 12 and a collimating lens assembly 11.

[0050] The welding method is

[0051] a. Clamp two butt-welded transparent plastic plates 6 in the fixture assembly 10 and adjust the clamping force;

[0052] b. Adjust the angle between the two welding heads 3 on the motion platform 8, and adjust the installation positions of the focusing lens assemblies 12 on the two welding heads 3 respectively.

[0053] c. Start the laser 1. The laser 1 emits two laser beams 4, which are transmitted through the optical fiber 2, pass through the two welding heads 3, and then through the heat sink 5 to reach the joint of the two transparent plastic plates 6. The two laser beams 4 are both focused on the joint of the transparent plastic plates 6. The polymer inside the plastic moves at high speed under the action of the laser energy, converting the laser energy into heat energy, causing a small amount of melting of the plastic at the joint. At the same time, the plastics are fused together under the action of the fixture and form a butt weld after cooling.

[0054] By selecting the welding process parameters, the temperature of the butt joint of the two transparent plastic plates 6 is precisely controlled to between the glass transition temperature and the thermal decomposition temperature during the welding process, thereby forming a high-strength weld. The welding process parameters include laser power, welding speed and spot diameter.

[0055] Specifically, the absorption rate of the transparent plastic plate 6 to the laser beam 4 with a wavelength of 1700nm to 2000nm is 65% to 76%. Since the transparent plastic plate 6 has a high absorption rate to the laser energy, in order to prevent the upper surface of the plastic from being melted, a heat sink 5 needs to be installed on the upper surface of the plastic so as not to affect the appearance of the upper surface of the plastic.

[0056] The length of the optical fiber 2 is 2 to 5 meters, and the inner diameter of the optical fiber 2 is 200 to 600 μm.

[0057] The two welding heads 3 are relatively stationary on the motion platform 8 , and the motion trajectories of the two welding heads 3 are consistent with the weld seams at the butt joints of the two transparent plastic plates 6 . The welding heads 3 realize three-dimensional curved welding along with the motion platform 8 .

[0058] When laser 1 emits a 60W laser beam, the welding speed can reach 10 to 20 mm / s. By optimizing the welding process parameters, the temperature of the plastic at the joint is precisely controlled between the glass transition temperature and the thermal decomposition temperature during welding, resulting in a high-strength weld.

[0059] The butt joints of the two transparent plastic plates 6 are aligned with the opening of the pressing plate 18 .

[0060] Second embodiment:

[0061] A laser butt welding device for transparent plastic differs from the first embodiment in that: at least one cylinder is provided on the supporting plate 21, and an elastic member 20 is provided on the piston rod of the cylinder. The elastic member 20 is made of rubber. The piston rod of the cylinder drives the elastic member 20 to move toward the outside of the transparent plastic plate 6, and the transparent plastic plate 6 and the elastic member 20 are in contact with each other to achieve a pressing effect.

[0062] Other undescribed parts are the same as those in the first embodiment and will not be described in detail here.

[0063] Third embodiment:

[0064] A laser butt welding device for transparent plastic differs from the first embodiment in that: the motion platform 8 is a multi-joint manipulator motion platform, the multi-joint manipulator motion platform includes a six-axis manipulator, the six-axis manipulator is provided with a clamp for fixing the welding head 3, and the six-axis manipulator drives the welding head 3 to move through the clamp; so that the two welding heads 3 respectively realize the three-dimensional spatial curved welding trajectory through the motion platform 8, which is an actuator that realizes the three-dimensional spatial welding trajectory.

[0065] Other undescribed parts are the same as those in the first embodiment and will not be described in detail here.

[0066] The above is a preferred embodiment of the present invention, which illustrates and describes the basic principles, main features, and advantages of the present invention. Those skilled in the art should understand that the present invention is not limited to the above embodiments. The above embodiments and descriptions are merely illustrative of the principles of the present invention. Various changes and modifications may be made to the present invention without departing from the spirit and scope of the present invention. Such changes and modifications are intended to fall within the scope of the present invention. The scope of protection claimed in the present invention is defined by the appended claims and their equivalents.

Claims

1. A laser butt welding device for transparent plastics, comprising a laser (1) and a workbench (7), wherein the workbench (7) is provided with a motion platform (8), and a fixture assembly (10) for clamping two butt-welded transparent plastic plates (6), wherein a heat sink (5) is provided above the two butt-welded transparent plastic plates (6), and the heat sink (5) at least covers the butt joint of the two butt-welded transparent plastic plates (6), and wherein: The motion platform (8) is provided with a welding head assembly (9), the welding head assembly (9) includes two welding heads (3), the two welding heads (3) are connected to the laser (1) via an optical fiber (2), the laser beam emitted by the laser (1) is transmitted via the optical fiber (2) and passes through the two welding heads (3) respectively, and an angle A is formed between the two welding heads (3), so that the relative angle of the two laser beams passing through the two welding heads (3) is 60° to 90°, and the focal points of the two laser beams are both focused on the butt joint of the two butt-welded transparent plastic plates (6); The fixture assembly (10) includes a fixture base plate (14), an electrically driven or pneumatic upper and lower pressing members (15), and a horizontal pressing member (16). The fixture base plate (14) is provided with two or more sliding guide pillars (19), two pressing cylinders (22), and a plastic plate supporting fitting (23); the pressing cylinder (22) is provided with a pressing plate (18), the pressing plate (18) is provided with an opening, the opening is provided with a transparent heat sink (5), and the two or more sliding guide pillars are provided. (19) respectively penetrate the pressing plate (18), the pressing plate (18) is located above the plastic plate supporting fitting (23), the pressing plate (18) and the pressing cylinder (22) are connected in cooperation so that the pressing plate (18) moves up and down along the sliding guide column (19), and the pressing cylinder (22), the pressing plate (18), and the heat sink (5) jointly realize the upper and lower pressing of the two butt-welded transparent plastic plates (6), so that the pressing cylinder (22) and the pressing plate (18) are combined into an upper and lower pressing member (15); The plastic plate supporting fitting (23) comprises a supporting side plate (17), a supporting flat plate (21), and an elastic member (20). The elastic member (20) is provided on the supporting flat plate (21). The supporting flat plate (21) is located on the top of the supporting side plate (17). One end of the elastic member (20) abuts against the inner side of the supporting flat plate (21), and the other end of the elastic member (20) abuts against the outer side of the transparent plastic plate (6). The elastic member (20) realizes the horizontal pressing of the butt joint of the transparent plastic plate (6) so as to maintain the horizontal pressing force of the two butt-welded transparent plastic plates (6) during the welding process. The horizontal pressing force of the butt joint of the transparent plastic plate (6) is adjusted by changing the pre-pressing force of the elastic member (20), so that the elastic member (20) and the supporting flat plate (21) are combined into a horizontal pressing member (16). The two welding heads (3) are respectively installed with a focusing lens assembly (12) and a collimating lens assembly (11); wherein, the welding head (3) realizes a uniform laser beam spot by adjusting the installation position of the focusing lens assembly (12), and the spot diameter is 0.4 to 2.0 mm; the welding head assembly (9) further includes a welding head fixing block (13), and the two welding heads (3) are respectively fixed on the welding head fixing block (13) in an inclined manner; The laser (1) is at least a semiconductor laser, the laser (1) emits a laser beam with a wavelength of 1700 nm to 2000 nm, the output power of the laser (1) is 30 to 100 W, the output power stable fluctuation value is less than 3%, and the beam quality M2 factor is less than 1.5; The motion platform (8) is at least a three-axis linear motion platform or a multi-joint manipulator motion platform, and the two welding heads (3) respectively realize the execution mechanism of the two-dimensional plane or three-dimensional space curve welding trajectory through the motion platform (8); The heat sink (5) is made of at least quartz glass or sapphire glass, and the heat sink (5) has a thermal conductivity greater than 1.0 W / m·K at a temperature of 150 to 300° C., and an absorptivity of the laser beam with a wavelength of 1700 nm to 2000 nm less than 5%.

2. The transparent plastic laser butt welding device according to claim 1, characterized in that: The two butt-welded transparent plastic plates (6) are made of the same plastic or dissimilar plastics.

3. A method for laser butt welding of transparent plastics, comprising the laser butt welding device for transparent plastics according to claim 1 or 2, the laser butt welding device for transparent plastics comprising a laser (1), a motion platform (8) and a fixture assembly (10) arranged on a workbench (7), the fixture assembly (10) clamping two butt-welded transparent plastic plates (6), the two butt-welded transparent plastic plates (6) being provided with heat sinks (5), the motion platform (8) being at least a three-axis linear motion platform or a multi-joint manipulator motion platform, and a welding head assembly (9) being provided on the motion platform (8), the welding head assembly (9) comprising two welding heads (3), the two welding heads (3) being connected to the laser (1) via optical fibers (2), the two welding heads (3) being arranged in an inclined manner, and having an angle A between the two welding heads (3), and the two welding heads (3) being respectively provided with a focusing lens assembly (12) and a collimating lens assembly (11); Its characteristics are: The welding method is a. Clamp two butt-welded transparent plastic plates (6) in the fixture assembly (10) and adjust the clamping force; b. adjusting the angle between the two welding heads (3) on the motion platform (8), and adjusting the installation positions of the focusing lens assemblies (12) on the two welding heads (3); c. Start the laser (1). The laser (1) emits two laser beams (4), which are transmitted through the optical fiber (2), pass through the two welding heads (3), and then pass through the heat sink (5) to reach the butt joint of the two transparent plastic plates (6). The two laser beams (4) are both focused on the butt joint of the transparent plastic plates (6). The polymer inside the plastic moves at high speed under the action of the laser energy, converting the laser energy into heat energy, causing a small amount of melting of the plastic at the butt joint. At the same time, the plastics are fused together under the action of the fixture, and a butt weld is formed after cooling.

4. The laser butt welding method for transparent plastics according to claim 3, characterized in that: By selecting welding process parameters, it is ensured that the temperature of the butt joint of the two transparent plastic plates (6) is accurately controlled to between the glass transition temperature and the thermal decomposition temperature during the welding process, thereby forming a high-strength weld. The welding process parameters include laser power, welding speed and spot diameter.

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