阅读说明：本技术 一种塑料的激光焊接方法 (Laser welding method for plastic ) 是由 江硕 江柏霖 刘承杰 李芷菲 张坤 王建刚 于 2021-06-24 设计创作，主要内容包括：本发明涉及一种塑料的激光焊接方法,包括：将两个不透光塑料工件对接,使两塑料工件的表面平齐,并在二者表面覆一平面玻璃以至少对两塑料工件的接缝处施与平面压力；采用可穿透平面玻璃的红外激光照射在接缝处,使两塑料工件熔化粘接,红外激光为连续激光,激光波长为700～1500nm,离焦量为负离焦；将平面玻璃与两塑料工件分离,获得所需产品。本发明采用不透光塑料作为加工对象进行对接拼焊,采用波长为700～1500nm的红外激光进行负离焦式焊接,焊接效果可控并且能获得较高的焊接质量,扩大了塑料激光焊接的可适用范围,而且能显著地降低加工成本；采用平面玻璃,在便于激光通过的同时,其施与的平面压力能显著地提高焊缝质量,使焊缝平滑整齐更牢固。(The invention relates to a laser welding method of plastic, which comprises the following steps: butting the two light-tight plastic workpieces to enable the surfaces of the two plastic workpieces to be flush, and covering a plane glass on the surfaces of the two plastic workpieces to apply plane pressure to at least the joint of the two plastic workpieces; irradiating the joint by adopting infrared laser capable of penetrating through the plane glass to melt and bond the two plastic workpieces, wherein the infrared laser is continuous laser, the laser wavelength is 700-1500 nm, and the defocusing amount is negative defocusing; separating the plane glass from the two plastic workpieces to obtain the required product. The invention adopts opaque plastics as a processing object to carry out butt-joint tailor-welding, adopts infrared laser with the wavelength of 700-1500 nm to carry out negative defocusing type welding, has controllable welding effect, can obtain higher welding quality, enlarges the applicable range of plastic laser welding, and can obviously reduce the processing cost; by adopting the plane glass, the laser can conveniently pass through, and the applied plane pressure can obviously improve the quality of the welding seam, so that the welding seam is smooth, regular and firmer.)

1. A method of laser welding plastic material, comprising:

butting the two light-tight plastic workpieces to enable the surfaces of the two plastic workpieces to be flush, and covering a plane glass on the surfaces of the two plastic workpieces to apply plane pressure to at least the joint of the two plastic workpieces;

irradiating the joint by adopting infrared laser capable of penetrating through the plane glass to melt and bond the two plastic workpieces, wherein the infrared laser is continuous laser, the laser wavelength is 700-1500 nm, and the defocusing amount is negative defocusing;

and separating the plane glass from the two plastic workpieces to obtain the required product.

2. A method of laser welding plastic material according to claim 1, characterized in that: the surface of one plastic workpiece adopts a step structure, and the other plastic workpiece is lapped on the step surface of the step structure.

3. A method of laser welding plastic material according to claim 1, characterized in that: and applying pre-compaction acting force to at least one of the plastic workpieces so as to enable the abutting surfaces of the two plastic workpieces to be attached before laser irradiation.

4. A method of laser welding plastic material according to claim 1, characterized in that: and controlling the swing amplitude and the swing frequency of the infrared laser to realize the swing welding of the laser beam.

5. A method of laser welding plastic material according to claim 1, characterized in that: and carrying out laser irradiation on the welding seam area for multiple times so as to achieve the set fusion depth.

6. A method of laser welding plastic material according to claim 1, characterized in that: the infrared laser is emitted by a semiconductor laser, and the power of the laser is 600-800W.

Technical Field

The invention relates to a laser welding method for plastic.

Background

Plastics have the excellent characteristics of low manufacturing cost, corrosion resistance, good insulating property, easy processing, long service life and the like, and have been developed in recent years to be used as novel artificial materials in parallel with base materials such as steel, cement, wood and the like, so that the plastics are increasingly widely applied to the fields of medical treatment, machinery, food, agriculture, aviation and the like. Along with the development of plastics, it is imperative to its secondary connection, traditional plastics welding mode has ultrasonic bonding, friction weld, vibration welding, hot plate welding, hot gas welding, implantation welding etc. wherein: although the ultrasonic welding, the friction welding and the vibration welding have simple process and strong repeatability, the scraps, marks and the like are easy to generate, and the performance of the plastic is reduced; hot plate welding, hot gas welding, implant welding are demanding on the operator and tend to break the consistency of the plastic.

At present, a laser welding technology is applied to plastic welding, and a transmission laser welding mode is generally adopted, namely, a laser beam passes through an upper layer of transparent plastic material and is absorbed by a lower layer of plastic material, and laser energy is absorbed to enable the temperature of the lower layer of plastic material to rise and melt the upper layer of plastic material and the lower layer of plastic material. The method has the advantages of high efficiency, high precision, good sealing performance, small heat influence and the like, and also has some problems: (1) the material of the sample plastic is required to be more, and the sample plastic is of a lap joint structure, so that the basic requirement that the light transmittance of an upper layer sample is higher (at least up to 20%) and the laser absorption capacity of a lower layer sample is strong is met; (2) for the lower layer sample, if the absorption capacity of the lower layer sample to the laser is required to be increased, the lower layer sample is realized by adopting an additive (such as carbon black) or a surface coating method, but more filler or thicker plastic cannot be welded, the requirements on the using amount of the additive and the thickness of the material are higher, the complexity of plastic welding is increased, and the application range is smaller.

Disclosure of Invention

The present invention relates to a method for laser welding of plastics, which solves at least some of the drawbacks of the prior art.

The invention relates to a laser welding method of plastic, which comprises the following steps:

butting the two light-tight plastic workpieces to enable the surfaces of the two plastic workpieces to be flush, and covering a plane glass on the surfaces of the two plastic workpieces to apply plane pressure to at least the joint of the two plastic workpieces;

irradiating the joint by adopting infrared laser capable of penetrating through the plane glass to melt and bond the two plastic workpieces, wherein the infrared laser is continuous laser, the laser wavelength is 700-1500 nm, and the defocusing amount is negative defocusing;

and separating the plane glass from the two plastic workpieces to obtain the required product.

In one embodiment, the surface of one plastic workpiece adopts a step structure, and the other plastic workpiece is overlapped on the step surface of the step structure.

In one embodiment, a pre-compression force is applied to at least one of the plastic workpieces to bond the abutting surfaces of the two plastic workpieces together prior to laser irradiation.

As one embodiment, the oscillation amplitude and oscillation frequency of the infrared laser are controlled to achieve oscillation welding of the laser beam.

In one embodiment, the weld zone is irradiated with laser light a plurality of times to achieve a set penetration depth.

In one embodiment, the infrared laser is emitted from a semiconductor laser, and the laser power is 600 to 800W.

The invention has at least the following beneficial effects:

according to the plastic laser welding method, opaque plastic is used as a processing object to be subjected to butt-joint tailor welding, infrared laser with the wavelength of 700-1500 nm is used for negative defocusing type welding, laser energy is converged at the junction of two plastic workpieces and absorbed by the surfaces of the two plastic workpieces, the two plastic workpieces are melted and bonded, the welding effect is controllable, high welding quality can be obtained, and the product rework rate is low; compared with the traditional plastic laser processing scheme, the method does not need to adopt a lap joint structure, does not need to enable laser to penetrate through the upper layer structure of the material and enable the lower layer structure to absorb the laser, does not need to adopt additives, avoids the conditions of unstable welding depth and the like caused by different amounts of the additives, enlarges the applicable range of plastic laser welding, and can obviously reduce the processing cost. By adopting the plane glass, laser can conveniently pass through the plane glass, and the plane pressure applied by the plane glass can obviously improve the quality of the welding seam, so that the welding seam is smooth, regular and firmer.

Drawings

In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings used in the description of the embodiments or the prior art will be briefly described below, it is obvious that the drawings in the following description are only some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to the drawings without creative efforts.

Fig. 1 is a schematic diagram of a laser welding method for plastic according to an embodiment of the present invention.

Detailed Description

The technical solutions in the embodiments of the present invention are clearly and completely described below, and it is obvious that the described embodiments are only a part of the embodiments of the present invention, and not all embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.

Referring to fig. 1, an embodiment of the present invention provides a method for laser welding plastic, including:

butting two light-tight plastic workpieces 1 to enable the surfaces of the two plastic workpieces 1 to be flush, and covering a plane glass 2 on the surfaces of the two plastic workpieces 1 to apply plane pressure to at least the joint of the two plastic workpieces 1;

irradiating the joint by adopting infrared laser capable of penetrating through the plane glass 2 to melt and bond the two plastic workpieces 1, wherein the infrared laser is continuous laser, the laser wavelength is 700-1500 nm, and the defocusing amount is negative defocusing;

and separating the plane glass 2 from the two plastic workpieces 1 to obtain the required product.

It can be understood that, unlike the conventional lap welding method for two plastic workpieces 1, in the present embodiment, a butt-joint welding method is adopted between the two plastic workpieces 1; the butt joint mode between two plastic work pieces 1 is the same as the conventional butt joint welding mode, taking the horizontal arrangement of the two plastic work pieces 1 as an example, the surfaces of the plastic work pieces 1 are parallel to a horizontal plane, the butt joint surfaces of the two plastic work pieces 1 are all parallel to a vertical direction, the formed joint seam is also parallel to the vertical direction, the two butt joint surfaces are opposite, and a laminating contact mode or an interval arrangement mode can be adopted between the two.

In this embodiment, the abutting surfaces of the two plastic workpieces 1 are preferably in contact with each other, so that the two plastic workpieces are attached to each other as much as possible without a gap, the firmness and the attractiveness of a weld joint can be improved, and a laser processing molded product is not easy to damage. Preferably, when the plane pressure is applied through the plane glass 2, a pre-pressing force can be further applied to at least one of the plastic workpieces 1 so as to make the abutting surfaces of the two plastic workpieces 1 abut before the laser irradiation; the pre-pressing acting force can be realized through a workpiece clamp, clamping a workpiece to be welded through the workpiece clamp is a conventional technology in the welding field, and is not described herein any more, and generally, the direction of the pre-pressing acting force is perpendicular to the joint.

After the surface of the two plastic workpieces 1 is covered by the plane glass 2, the plane glass 2 can be pressed tightly by a pressing block and other members, so that the purpose of applying plane pressure to the joint of the two plastic workpieces 1 can be achieved, and when the area of the plane glass 2 is enough, the plane glass 2 can uniformly apply plane pressure to the whole surface of the two plastic workpieces 1.

Further preferably, as shown in fig. 1, the surface of one plastic workpiece 1 adopts a step structure, and the other plastic workpiece 1 is overlapped on the step surface of the step structure. For convenience of description, the step structure includes a first step surface, a second step surface and an adapter surface connecting the two step surfaces, wherein the first step surface is a top surface (i.e., a surface pressed by the flat glass 2) of the plastic workpiece 1, and the other plastic workpiece 1 is supported on the second step surface, the adapter surface is a butt-joint surface corresponding to the plastic workpiece 1, and the butt-joint surface of the other plastic workpiece 1 is attached to the adapter surface. Based on the structure, on one hand, the positioning between the two plastic workpieces 1 is convenient, and the welding quality can be correspondingly improved; on the other hand, the welding operation between the plastic workpieces 1 with different specifications can be facilitated, for example, when the thicknesses/heights of the two plastic workpieces 1 are different, the surfaces of the two plastic workpieces 1 can be kept flush by adopting the step structure through the change of the structures of the plastic workpieces 1, so that the welding quality is improved.

Further preferably, in the above scheme with the step structure, when the step height (i.e. the height of the above-mentioned adapting surface) is greater than the preset weld depth, a heat-conducting copper sheet may be attached to the adapting surface or the abutting surface of another plastic workpiece 1, the heat-conducting copper sheet is preferably located below the preset weld zone, after the surface of the plastic workpiece 1 is irradiated with laser to form a molten pool, heat of the molten pool may be transferred to the plastic surface areas on both sides of the copper sheet through the above-mentioned heat-conducting copper sheet, so that the plastic surface areas are melted by heat, thereby increasing the depth of the molten pool and improving the connection reliability of the two plastic workpieces 1 accordingly. Furthermore, the heat-conducting copper sheet can be provided with a penetration hole or a penetration groove to communicate the plastic surface areas on the two sides, so that the effect of melting and bonding the plastic surface areas on the two sides can be improved.

The plane glass 2 preferably allows the infrared laser with the wavelength of 700-1500 nm to substantially completely transmit, and in the embodiment, the transmittance of the plane glass 2 to the infrared laser with the wavelength of 700-1500 nm is controlled to be more than 90%, so that the energy loss can be effectively reduced, the processing efficiency can be improved, and the processing cost can be reduced.

The opaque plastic is preferably black thermoplastic.

According to the plastic laser welding method provided by the embodiment, opaque plastic is used as a processing object for butt-joint tailor welding, infrared laser with the wavelength of 700-1500 nm is used for negative defocusing type welding, laser energy is converged at the junction of the two plastic workpieces 1 and absorbed by the surfaces of the two plastic workpieces 1, the two plastic workpieces 1 are melted and bonded, the welding effect is controllable, higher welding quality can be obtained, and the rework rate of products is low; compared with the traditional plastic laser processing scheme, the method does not need to adopt a lap joint structure, does not need to enable laser to penetrate through the upper layer structure of the material and enable the lower layer structure to absorb the laser, does not need to adopt additives, avoids the conditions of unstable welding depth and the like caused by different amounts of the additives, enlarges the applicable range of plastic laser welding, and can obviously reduce the processing cost. By adopting the plane glass 2, laser can conveniently pass through, and meanwhile, the plane pressure applied by the plane glass 2 can obviously improve the quality of the welding seam, so that the welding seam is smooth, regular and firmer.

In a further preferable scheme, the wavelength of the infrared laser is selectively controlled within the range of 900-1020 nm, wherein the optimal welding quality can be obtained by selecting the laser wavelength with the wavelength of about 980nm (960-990 nm), and meanwhile, the processing efficiency is guaranteed.

The welding method is further optimized, when plastic laser welding is carried out, air holes are easy to generate, the effective working surface of a welding seam is further weakened, the problem of stress concentration is caused, welding airtightness is affected, and the strength and toughness of the welding seam are reduced; in general, the oscillation of the laser beam 3 can be achieved by a galvanometer.

Generally, plastics have good thermoplasticity, and when laser beam 3 shines on the plastics surface, plastics are heated and melt, and high strength laser beam 3 can make plastics gasification, molten bath collapse, and in this embodiment, the processing is carried out to the laser power of selecting suitable, and the melting of control plastics work piece 1 is melted but not gasified, especially based on the laser processing mode of negative defocusing, combines the effect of plane glass 2, can make the molten bath develop downwards, reaches required penetration, obtains the target weld depth. In this embodiment, preferably, the infrared laser is emitted by a semiconductor laser, and the laser power is 600 to 800W, and further preferably controlled at 700 to 800W.

In addition, to achieve the desired weld quality, the weld zone is subjected to multiple laser shots to achieve a set penetration. The multiple laser irradiation can be laser irradiation for a preset time on the same welding spot position, and after the welding spot position is processed, the operation of the next welding spot position is carried out; it is preferable to perform a plurality of welding operations reciprocally along the extending direction of the weld. Because the plane glass 2 is adopted to carry out plane compaction on the two plastic workpieces 1, the transverse diffusion of a heat affected zone has no influence on the quality of a formed product; cooling means, such as blowing a cooling gas onto the surface of the flat glass 2, may be used to control the lateral diffusion of the heat affected zone.

The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like that fall within the spirit and principle of the present invention are intended to be included therein.