CN102107530A - A New Method of Welding Plastics Using a Metal Laser Welding Machine - Google Patents

Abstract

The invention discloses a new method for welding plastics by a metal laser welding machine, which comprises the following steps: a) a computer is adopted to control a special board card, and near infrared laser with certain frequency and wavelength of 800-; b) clamping two plastic parts to be welded together, allowing near infrared laser to transmit through a first part in a mode of deviating from a focus and then to be absorbed by a second part, wherein the absorbed near infrared laser is converted into heat energy, and melting the contact surfaces of the two parts to form a welding area; the method can generate precise, firm and sealed welding, the resin degradation is less, the generated scraps are less, the surfaces of the products can be tightly connected together around the welding line, the high-speed welding can be realized only by very low frequency, and the efficiency is three times that of the common plastic welding.

Description

A New Method of Welding Plastics Using a Metal Laser Welding Machine

the

technical field

The invention belongs to the technical field of laser welding, and in particular relates to a new method for welding plastics with a metal laser welding machine.

Background technique

Traditional plastic welding is realized by heating, the heat-affected zone is large, and the surface will be deformed, which will affect the appearance. Moreover, the vibration stress and thermal stress of the welded products are very large, which means that the aging speed of the products or internal components of the device is very fast, which greatly shortens the service life of the products.

So far there has been no extensive research on the application of metal laser welding machines to weld plastic parts of different materials.

Contents of the invention

The object of the present invention is to provide a method for welding two plastic parts together by using a laser welding machine.

The technical solution adopted by the present invention to solve the technical problem is: a new method of welding plastics with a metal laser welding machine, the steps are as follows: a) Using a computer-controlled special board to output a near frequency with a wavelength of 800-1064nm Infrared laser; b) Clamp the two plastic parts to be welded together, let the near-infrared laser transmit through the first part in an off-focus manner, and then be absorbed by the second part, the absorbed near-infrared laser Turned into heat energy, the contact surfaces of the two parts are melted to form a welding zone.

Further, the distance of focus deviation in step b) is 50-90mm, and the spot diameter is 3-5mm.

Further, the welding machine is a semiconductor laser welding machine, an optical fiber laser welding machine or an end-pump laser welding machine.

Still further, the welding process parameters are as follows: the current is 150-180A, the pulse width is 8-10ms, the speed is 2700mm/s, and the frequency is 2Hz.

The beneficial effects of the present invention are:

(1) It can produce precise, firm and airtight (airtight and watertight) welding, with less resin degradation and less debris, and the surface of the product can be tightly connected around the weld;

(2) It is easy to control, has good adaptability, and can weld workpieces with small size or complex shape and structure;

(3) The vibration stress and thermal stress of the product are greatly reduced, much smaller than the vibration stress and thermal stress generated by other connection methods;

(4) Ability to weld many different types of materials together;

(5) Due to the off-focus welding, the welding spot is large, and only a very low frequency can be used to achieve high-speed welding, which is three times the efficiency of general plastic welding.

Description of drawings

Fig. 1 is the schematic diagram during positive focal length welding of the present invention;

Fig. 2 is a schematic diagram of the present invention during negative focal length welding.

Detailed ways

The present invention is described in further detail below in conjunction with embodiment.

A new method of welding plastics using a metal laser welding machine that can create welds that exceed the strength of the raw material, the steps are as follows:

a) Select semiconductor laser welding machine, fiber laser welding machine or end-pump laser welding machine, use computer-controlled special board to output near-infrared laser with a certain frequency and wavelength of 800-1064nm;

b) Clamp the two plastic parts to be welded together, let the near-infrared laser transmit through the first part in a way that deviates from the focus, where the distance from the focus is 50-90mm, and the diameter of the spot is 3-5mm. Absorbed by the second component, the absorbed near-infrared ray is lasered into heat energy, melting the contact surfaces of the two components to form a welding zone. The welding process parameters are as follows: the current is 150-180A, and the pulse width is 8- 10ms, the speed is 2700mm/s, and the frequency is 2Hz.

As shown in Figures 1 and 2, the laser light 3 generated by the laser 1 is projected onto two pieces of plastic through the focusing lens 2, passes through the transparent plastic 5, forms a spot 4 on the non-transparent plastic 6, and finally focuses on the focal plane 7.

Due to the small divergence angle of the welding machine laser and the good optical mode, the spot size is usually 0.06mm when marking at the focus position, which provides a feasible basis for precision plastic welding. Positioning marking, when plastic components are used as marking components, due to the absorption of the laser wavelength by the plastic, there will be processing hot-melt marks on the lines scanned by the laser. Using this feature, the marking is completed using the principle of marking The trajectory realizes the function of plastic welding.

The choice of welding focal length, usually when welding the workpiece, the laser is within 4mm of the focal point, and the long-distance partial focus is used for leveling and beautiful after welding. However, if the plastic welding is performed at a position 30-50mm away from the focal point, the firmness of the plastic welding can be achieved. When using this equipment to weld plastics, it must be defocused. The reason is that due to the high power density during positive focus welding, the absorption of laser wavelengths by plastics is generally at 810--980nm, but when the wavelength of 1064nm is used, the absorption of lasers by plastics is not very good. In this way, it is easy to burn the upper surface of the plastic during positive focus welding, which cannot meet the welding requirements. The test proves that if the welding is performed at a position where the focus position is not far away, the transparent plastic on the upper surface will be severely burned, and there will be Irregular punch points. There is no joint strength between the two pieces of plastic.

Welding method of the present invention has following beneficial effect:

(1) It can produce precise, firm and airtight (airtight and watertight) welding, and there is less resin degradation and less debris generated. The surface of the product can be tightly connected around the weld, and the advantages of no residue make it It is more suitable for pharmaceutical products and electronic sensors regulated by the State Food and Drug Administration. the

(2) It is easy to control, has good adaptability, and can weld workpieces with small size or complex shape structure, mainly because the laser is easy to control by computer software,

(3) The vibration stress and thermal stress of the product are greatly reduced, which is much smaller than that generated by other connection methods, which means that the aging speed of the product or the internal components of the device is slower, and it can be applied to Very fragile product.

(4) It can weld many kinds of different materials together, for example, it can connect polycarbonate (PC) through near-infrared laser and black polybutylene terephthalate (PBT) reinforced with 30% glass fiber. Together, other welding methods simply cannot join two polymers that are so different in terms of structure, softening point and reinforcement material.

(5) High welding efficiency and low welding frequency. Because it is Gaussian light, laser melting and welding are smoother, and the laser welding spot is large due to the large distance from the focus (generally 5-10mm), so that when the sealing welding requirements are to be met, the welding speed will naturally be fast. Focus welding, large welding spot, only need a very low frequency to achieve high-speed welding, which is three times the efficiency of general plastic welding.

Almost all thermoplastics and thermoplastic elastomers can use laser welding technology, commonly used welding materials are PP, PS, PC, ABS, polyamide, PMMA, polyoxymethylene, PET and PBT, etc., and some other engineering plastics such as poly Phenyl sulfide PPS and liquid crystal polymer, etc., are not suitable for laser welding technology due to their low laser transmittance, so carbon black is often added to the bottom material so that it can absorb enough energy to meet the requirements of laser welding. Requirements for transmission welding.

Unfilled or glass fiber reinforced polymer materials can be used for laser welding, but too high glass fiber content will scatter the emitted IR laser light, reducing the penetration of the beam through the polymer.

Colored plastics can also be used for laser welding, but as the pigment or dye content increases, the penetration of the laser beam through the plastic decreases.

The above-mentioned embodiments only illustrate the principles and effects of the present invention, as well as the partially used embodiments. For those of ordinary skill in the art, without departing from the inventive concept of the present invention, some deformations and modifications can also be made. Improvements, these all belong to the protection scope of the present invention.

Claims (4)

1. A novel method for welding plastics using a metal laser welding machine, characterized in that the steps are as follows: a) Using a computer-controlled special board to output a near-infrared laser with a certain frequency and a wavelength of 800-1064nm; b) Clamp the two plastic parts to be welded together, let the near-infrared laser transmit through the first part in a defocused manner, and then be absorbed by the second part, and the absorbed near-infrared laser is converted into heat energy , to melt the contact surfaces of the two components to form a weld zone. 2. The new method of welding plastics according to claim 1, characterized in that, in the step b), the focal point deviation distance is 50-90mm, and the spot diameter is 3-5mm. 3. The new method for welding plastics according to claim 2, wherein the welding machine is a semiconductor laser welding machine, an optical fiber laser welding machine or an end-pump laser welding machine. 4. The new method of welding plastics according to claim 3, characterized in that the welding process parameters are as follows: current is 150-180A, pulse width is 8-10ms, speed is 2700mm/s, and frequency is 2Hz.

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