CN111002591A - Laser transmission welding method for plastic parts - Google Patents

Abstract

The invention discloses a laser transmission welding method for plastic parts, which is an optically transparent thermoplastic plastic part. Place the metal absorbent in the groove after the part to be welded of the plastic part; press the part to be welded of the first plastic part against the metal absorbent and then overlap it on the part to be welded of the second plastic part, and use a clamp to fix it. The first plastic part and the second plastic part are clamped; the laser beam generated by the laser irradiates the to-be-welded part of the first plastic part one or more times, the laser beam passes through the first plastic part and is aimed at the metal absorbent, Under the action of laser beam energy, the plastic near the metal absorbent is melted, and the gap between the first plastic part and the second plastic part is fused, so that the first plastic part and the second plastic part are welded together. The invention can effectively maintain the aesthetics of welding, improve welding quality and efficiency, and at the same time, can avoid burning of plastic parts.

Description

A laser transmission welding method for plastic parts

technical field

The invention relates to the technical field of laser welding, in particular to a laser transmission welding method for plastic parts.

Background technique

Plastic products are usually composed of two or more parts. These parts are assembled together in three ways: mechanical fixing, adhesive bonding, and thermal welding. The processing procedures of mechanical fixing and adhesive bonding are relatively complicated, and at the same time, impurities that may pose a potential threat to human health may be generated, which are not allowed in some industries such as medical treatment and food. Friction welding (ultrasonic welding, vibration welding, spin welding, etc.), electrofusion welding, hot plate welding and other thermal welding that do not require the addition of foreign substances are the common connection methods for plastic products in these fields, but friction welding, electrofusion welding and The machining accuracy of hot plate welding and other methods is relatively rough, and it is generally suitable for low-precision welding occasions.

As a relatively new welding technology, laser welding has many advantages: (1) non-contact welding; (2) adjustable beam shape and size, which can reduce the heat-affected zone and weld width, and reduce thermal stress; (3) The welding speed is fast and the efficiency is high; (4) the welding seam has high strength, no residue and good appearance. Therefore, laser welding technology can not only meet the requirements of high-precision machining, but also ensure high-strength connection requirements.

As the cost of lasers decreases, laser welding technology is gradually applied in the field of plastic welding. At present, most of the plastic laser welding equipment on the market use the near-infrared laser with a wavelength of ≤1200nm as the light source, and most of the optically transparent thermoplastics themselves have weak absorption of the near-infrared laser (10%, 1mm thick sample), and generally cannot directly welding. Therefore, in the current plastic laser transmission welding technology, in order to improve the absorption rate of the plastic to the laser, people often add a light absorber to the two optically transparent plastics. As shown in Figures 1 and 2, 1 represents the upper plastic layer, 2 represents the lower layer plastic, 3 represents the light absorber, 4 represents the laser beam, and 5 represents the welding seam. The laser welding method for optically transparent plastics in the prior art has three steps : (1) uniformly coat the upper surface of the lower plastic with a powder or liquid light absorber; (2) use a special clamping device to clamp the two plastics; (3) use a laser beam for welding. During welding, the laser beam is transmitted through the upper layer of plastic, absorbed by the absorbent coated on the upper surface of the lower layer of plastic, and converted into heat. The laser radiation fuses and cools to form a weld.

There are obvious defects in the laser welding method of optically transparent plastics in the prior art: (1) The coated light absorbing agent is usually powdered or liquid substances such as carbon black, resin, metal oxide, alloy powder, Clearweld, etc. These physical properties Unstable substances are easy to diffuse out of the welding area and cause contamination to the welded parts, which is not allowed in some high-cleanliness industries (such as medical, food, precision electronics, etc.); (2) Some commercialized special absorbents The price is relatively expensive, and the use of these absorbents will increase the welding cost; (3) The general coating process is: dissolve the absorbent with a solvent, stir the mixture evenly, and then coat it on the plastic surface, wait for the solvent to evaporate and dry before welding. The whole coating process is cumbersome and takes a long time, which leads to the reduction of welding efficiency; (4) At present, most of the coating processes are manual coating, and the coating quality depends heavily on the technical level of the operator. If the technical level is poor, it is easy to cause Poor welding quality due to uneven coating; (5) The absorbent between the interfaces will hinder the molecular diffusion and entanglement between the upper and lower plastics, reducing the bonding force of the two plastics; (6) Plastic and absorbent The thermal conductivity of the plastic is very poor. If the absorbent is not uniformly coated or the laser power is unstable, it is easy to cause the plastic to be partially burnt due to excessive energy.

Therefore, the existing technology still needs to be improved and developed.

SUMMARY OF THE INVENTION

In view of the above-mentioned deficiencies of the prior art, the purpose of the present invention is to provide a laser transmission welding method for plastic parts, using metal absorbent instead of dye as the absorbent to improve the welding efficiency and quality.

The technical scheme of the present invention is as follows:

A laser transmission welding method for plastic parts, which is used for laser welding between a first plastic part and a second plastic part, wherein the first plastic part is an optically transparent thermoplastic plastic part, which comprises the following steps:

directly place the metal absorbent on the to-be-welded part of the second plastic part, or place the metal absorbent in the groove after opening a groove on the to-be-welded part of the second plastic part;

Press the to-be-welded part of the first plastic part against the metal absorbent and then overlap it on the to-be-welded part of the second plastic part, and clamp the first plastic part and the second plastic part with a clamp;

The laser beam generated by the laser irradiates the to-be-welded part of the first plastic part one or more times. The laser beam passes through the first plastic part and is aimed at the metal absorbent. The plastic melts, and the gap between the first plastic part and the second plastic part is fused, so that the first plastic part and the second plastic part are welded together.

Preferably, directly placing the metal absorbent on the to-be-welded part of the second plastic part, or before placing the metal absorbent in the groove after opening the groove on the to-be-welded part of the second plastic part, further comprises:

Use alcohol to remove oil and dirt on the surfaces of the first and second plastic parts.

Preferably, the metal absorbent is metal wire, metal film or metal sheet.

Preferably, the metal wire has a width of 0.2-1.0 mm and a thickness of 0.1-0.5 mm.

Preferably, both the metal film and the metal sheet are arranged in a rectangular, circular or other irregular shape with several through holes.

Preferably, both the metal film and the metal sheet are made by laser cutting, chemical etching, and punching.

Preferably, the metal absorbents are all made of iron, aluminum, copper or their alloys with good thermal conductivity.

Preferably, the second plastic part is thermoplastic.

Preferably, the first plastic part and the second plastic part are clamped between two quartz glass plates with high transparency to laser beam and high temperature resistance, and clamped by two three-rod cylinders with adjustable air pressure valves .

Preferably, the laser is a continuous near-infrared semiconductor laser, and the diameter or width of the laser beam is larger than the width of the metal absorber.

Compared with the prior art, the embodiments of the present application mainly have the following beneficial effects:

(1) The physical properties of the metal absorbent are stable, no particulate impurities will be generated, and the welded parts will not be polluted.

(2) Metal absorbents can be common metals such as iron, aluminum or copper and their alloys, with wide sources and low prices;

(3) When welding, the operator can directly place the metal absorbent on the welding part to weld, which is easy to operate and has high efficiency;

(4) The operator can operate skillfully without long-term training, there is no problem of uneven coating, and the welding quality is stable;

(5) There is no foreign particle impurities in the weld to affect molecular diffusion and entanglement, and the welding strength is high;

(6) The metal absorbent has good thermal conductivity. If the laser power is instantaneously too high, the metal can diffuse the instantaneous excessive heat in time to play a buffering role and prevent the plastic from burning.

Description of drawings

In order to illustrate the solution of the present application more clearly, the following will briefly introduce the accompanying drawings used in the description of the embodiments. Obviously, the accompanying drawings in the following description are some embodiments of the present application, which are useful to ordinary skills in the art. As far as personnel are concerned, other drawings can also be obtained from these drawings on the premise of no creative work.

Figure 1 is an exploded view of a prior art plastic welding.

FIG. 2 is a schematic structural diagram of plastic welding in the prior art.

3 is an exploded view of a preferred embodiment of the laser transmission welding method for plastic parts in the present invention.

FIG. 4 is a schematic structural diagram of a preferred embodiment of the laser transmission welding method for plastic parts in the present invention.

FIG. 5 is an exploded view of another preferred embodiment of the laser transmission welding method for plastic parts according to the present invention.

FIG. 6 is a schematic structural diagram of another preferred embodiment of the laser transmission welding method for plastic parts according to the present invention.

Detailed ways

Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art of this application; terms used herein in the specification of the application are for the purpose of describing particular embodiments only , is not intended to limit the application; the terms "comprising" and "having" and any variations thereof in the description and claims of this application and the above description of the drawings are intended to cover non-exclusive inclusion. The terms "first", "second" and the like in the description and claims of the present application or the above drawings are used to distinguish different objects, rather than to describe a specific order.

Reference herein to an "embodiment" means that a particular feature, structure, or characteristic described in connection with the embodiment can be included in at least one embodiment of the present application. The appearances of the phrase in various places in the specification are not necessarily all referring to the same embodiment, nor a separate or alternative embodiment that is mutually exclusive of other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

As shown in Figures 3 to 6, 6 represents the first plastic part, 7 represents the second plastic part, 8 represents the metal absorbent, 9 represents the laser beam, and 10 represents the welding seam. A laser transmission welding method for plastic parts is specifically described with reference to the accompanying drawings, which is used for laser welding between a first plastic part and a second plastic part, and the first plastic part is an optically transparent thermoplastic part, which includes the following step:

S100, directly placing the metal absorbent on the to-be-welded part of the second plastic part, or placing the metal absorbent in the groove after opening a groove on the to-be-welded part of the second plastic part;

S200, pressing the to-be-welded part of the first plastic part against the metal absorbent and then overlapping it on the to-be-welded part of the second plastic part, and clamping the first plastic part and the second plastic part with a clamp;

S300, the laser beam generated by the laser irradiates the to-be-welded part of the first plastic part one or more times, the laser beam passes through the first plastic part and is aimed at the metal absorbent, and under the action of the energy of the laser beam, the metal absorbent The nearby plastic melts, and the gap between the first plastic part and the second plastic part is fused, so that the first plastic part and the second plastic part are welded together.

In this method, metal absorbent is used instead of traditional dye as absorbent, and the welding surface between two plastic parts does not need to be coated with powder or liquid absorbent, but can be replaced by metal wire, metal film or metal sheet. When welding by this method, the large-diameter laser beam does not need to be strictly shaped by an optical lens to form the required small-diameter beam, but is directly radiated on the metal absorbent. The light absorption rate of metal is generally higher than that of plastic, so the heating rate of metal is faster than that of plastic. The plastic near the metal absorber first melts and fuses, and then forms a weld after cooling. These welds connect the first plastic part and the second plastic part. The gaps between the pieces are fused together. Although the plastic in other parts is irradiated by the laser, because of its low light absorption rate, most of the laser light passes directly through the plastic and is not absorbed and converted into heat, so the plastic does not melt and will not form a weld.

In a further preferred embodiment of the present invention, in S100, the metal absorbent is directly placed on the to-be-welded part of the second plastic part, or the metal absorbent is placed in the groove after a groove is made on the to-be-welded part of the second plastic part Also includes:

S400, use alcohol to remove oil stains and dirt on the surfaces of the first plastic part and the second plastic part. This can effectively avoid the impact of impurities on the welding quality.

In a further preferred embodiment of the present invention, the metal absorbent is a metal wire, a metal film or a metal sheet, and the metal wire has a width of 0.2-1.0 mm and a thickness of 0.1-0.5 mm.

In order to adapt to different shapes of plastic welding parts, in addition to using metal wires, metal absorbents can also be made into sheets or films. As shown in FIGS. 5 and 6 , the metal film and the metal sheet are provided with polygons with several through holes. These metal films and metal sheets will absorb the laser beam in the part with metal, and in the part without metal, most of the laser beam will directly pass through the second plastic. Of course, the metal film and the metal sheet can also be arranged in a circle or other irregular shape with several through holes.

In a further preferred embodiment of the present invention, the metal wires, metal films and metal sheets are all made of iron, aluminum, copper or their alloys with good thermal conductivity.

In a further preferred embodiment of the present invention, the second plastic part is a thermoplastic. The first plastic part may be PET, and the second plastic part may be PET, PC, PP, PVC, PMMA, PE, POM or PETG.

In a further preferred embodiment of the present invention, the laser is a continuous near-infrared semiconductor laser, the laser wavelength range is 793-1064 nm, the continuous near-infrared semiconductor laser is output by a fiber collimator, and the continuous near-infrared semiconductor laser The maximum output power is 50W;

In a further preferred embodiment of the present invention, the first plastic part and the second plastic part are clamped between two quartz glass plates that are highly transparent to laser beams and resistant to high temperature, and pass through two adjustable air pressure valves. is clamped by a three-rod cylinder with a bore of 25mm.

In a further preferred embodiment of the present invention, the diameter or width of the laser beam is larger than the width of the metal absorber.

To sum up, the laser transmission welding method for plastic parts provided by the present invention includes the following steps: directly placing a metal absorbent on the to-be-welded part of the second plastic part, or placing a metal absorbent on the to-be-welded part of the second plastic part After slotting, place the metal absorbent in the groove; press the to-be-welded part of the first plastic part against the metal absorbent and then overlap it on the to-be-welded part of the second plastic part; The two plastic parts are clamped; the laser beam generated by the laser irradiates the to-be-welded part of the first plastic part one or more times, and the laser beam passes through the first plastic part and is aimed at the metal absorbent. The plastic near the lower metal absorbent melts, and the gap between the first plastic part and the second plastic part is fused, so that the first plastic part and the second plastic part are welded together, which effectively improves the welding efficiency and quality. At the same time, it can maintain the aesthetics, the welding cost is low, and the plastic will not be scorched.

Obviously, the above-described embodiments are only a part of the embodiments of the present application, rather than all of the embodiments. The accompanying drawings show the preferred embodiments of the present application, but do not limit the scope of the patent of the present application. This application may be embodied in many different forms, rather these embodiments are provided so that a thorough and complete understanding of the disclosure of this application is provided. Although the present application has been described in detail with reference to the foregoing embodiments, for those skilled in the art, they can still modify the technical solutions described in the foregoing specific embodiments, or perform equivalent replacements for some of the technical features. . Any equivalent structure made by using the contents of the description and drawings of the present application, which is directly or indirectly used in other related technical fields, is also within the scope of protection of the patent of the present application.

Claims (10)

1. A laser transmission welding method for plastic parts is used for laser welding between a first plastic part and a second plastic part, the first plastic part is an optical transparent thermoplastic plastic part, and the laser transmission welding method for the plastic parts comprises the following steps:

directly placing a metal absorbent on the part to be welded of the second plastic part, or placing the metal absorbent in a groove after grooving the part to be welded of the second plastic part;

pressing a metal absorbent on a part to be welded of the first plastic part, overlapping the part to be welded of the second plastic part, and clamping the first plastic part and the second plastic part by using a clamp;

the laser beam generated by the laser irradiates the part to be welded of the first plastic part one or more times, the laser beam penetrates through the first plastic part and is aligned with the metal absorbent, the plastic near the metal absorbent is melted under the action of the energy of the laser beam, and a gap between the first plastic part and the second plastic part is fused, so that the first plastic part and the second plastic part are welded.

2. The laser transmission welding method for plastic parts according to claim 1, wherein the step of directly placing the metal absorbent on the part to be welded of the second plastic part, or placing the metal absorbent in the groove after grooving the part to be welded of the second plastic part further comprises the steps of:

and removing oil stains and dirt on the surfaces of the first plastic part and the second plastic part by using alcohol.

3. The laser transmission welding method for plastic parts according to claim 2, characterized in that the metal absorber is a metal wire, a metal film or a metal sheet.

4. A laser transmission welding method for plastic parts according to claim 3, characterized in that the width of the metal wire is 0.2-1.0 mm and the thickness is 0.1-0.5 mm.

5. A laser transmission welding method for plastic parts, according to claim 3, characterized in that said metal film and metal sheet are both arranged in a rectangular, circular or other irregular shape with a plurality of through holes.

6. A laser transmission welding method for plastic parts according to claim 5, characterized in that said metal film and metal sheet are made by laser cutting, chemical etching, punching and processing.

7. The laser transmission welding method for plastic parts according to claim 1, characterized in that the metal absorbers are all made of iron, aluminum, copper or alloys thereof with good thermal conductivity.

8. Laser transmission welding method for plastic parts according to claim 1, characterised in that said second plastic part is a thermoplastic.

9. The laser transmission welding method for plastic parts according to claim 1, characterized in that the first plastic part and the second plastic part are clamped between two quartz glass plates which are highly transparent to the laser beam and resistant to high temperature and are clamped by two three-rod cylinders with adjustable gas pressure valves.

10. A laser transmission welding method for plastic parts according to claim 1, characterized in that said laser is a continuous near infrared semiconductor laser, and the diameter or width of said laser beam is larger than the width of the metal absorber.

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