CN108515703A - Transparent plastic welding method - Google Patents

Abstract

The invention relates to a transparent plastic welding method, which comprises the steps of: stacking and placing two transparent plastics to be welded; covering the upper layer of transparent plastic with a heat sink; and the transparent plastic on the upper layer, and focus on the joint surface of the two transparent plastics to weld the two transparent plastics together. In the transparent plastic welding method of the present invention, the laser with a wavelength of 1700nm to 2000nm is used to weld the transparent plastic, and the transparent plastic has a lower light transmittance to the laser with a wavelength of 1700nm to 2000nm, so that when the transparent plastic is welded , no need to add absorbent, thereby improving welding efficiency; at the same time, heat sinks are used to dissipate heat from the upper transparent plastic to avoid burning of the upper transparent plastic due to excessive temperature.

Description

Transparent plastic welding method

technical field

The invention relates to a transparent plastic welding process, in particular to a transparent plastic welding method.

Background technique

Plastic is light in weight, strong in chemical corrosion resistance, good in impact resistance, good in insulation and wear resistance, low in manufacturing cost, and easy to process into different shapes. Plastics are used in a wide range of applications, such as product packaging, daily products, pipes, etc.

Due to its high light transmittance, transparent plastics are widely used in lighting equipment, optical instruments, plastic glass, optical fiber materials, optical disc materials, transparent packaging and other fields. For special fields such as optical contact lenses, optical fiber materials, and medical plastics, the cleanliness of plastics is extremely high. The traditional transparent plastic welding methods are ultrasonic welding, friction welding, vibration welding, hot plate welding, hot gas welding, and implant welding. Although ultrasonic welding, friction welding, and vibration welding have simple processes and strong repeatability, they are prone to debris and marks, which reduce the cleanliness and light transmittance of transparent plastics. Similarly, hot plate welding, hot gas welding, and implant welding not only have high requirements for operators, but also easily destroy the consistency and transparency of plastics. Therefore, there is an urgent need for a new and reliable welding method to meet the welding requirements of transparent plastics. Laser welding as an advanced, non-contact welding technology makes this possible.

However, in the traditional transparent plastic laser welding process, absorbers such as clearweld need to be coated on the transparent plastic during the welding process, which increases the complexity and cost of the welding process.

Contents of the invention

Based on this, it is necessary to provide a transparent plastic welding method to solve the problem that traditional transparent plastic laser welding requires absorbers and affects welding efficiency.

A transparent plastic welding method, the method comprising the steps of:

Place the two transparent plastics to be welded in layers;

A heat sink is covered on the upper transparent plastic;

A laser with a wavelength of 1700nm-2000nm is used to sequentially pass through the heat sink and the upper layer of transparent plastic, and focus on the joint surface of the two transparent plastics to weld the two transparent plastics together.

In one embodiment, when the laser is focused on the joining surface of the two transparent plastics for welding, the surface of the heat sink away from the transparent plastic is pressurized.

In one embodiment, the material of the transparent plastic is selected from one of polyamide, copolyester and polycarbonate or a copolymer of at least two of the monomers of the above polymers.

In one embodiment, the wavelength of the laser is 1940nm, the power is 30W, and the transparent plastic is welded at a speed of 2mm/s˜4mm/s.

In one embodiment, during the laser welding process of the transparent plastic, the heat sink and the two transparent plastics are compressed and fixed by a clamp.

In one embodiment, the heat sink is made of quartz glass.

In one embodiment, the infrared transmittance of the quartz glass is above 95% at a wavelength of 1700nm-2000nm.

In one embodiment, the thermal conductivity of the heat sink at 150-200° C. is 1-1.2 W/m·K, and the absorption loss of the laser is not higher than 5%.

In one embodiment, the infrared transmittance of the two transparent plastics is 65%-75% at a wavelength of 1700nm-2000nm.

In one embodiment, the two transparent plastics are made of the same material.

A transparent plastic welding method provided by the present invention uses a laser with a wavelength of 1700nm to 2000nm to weld the transparent plastic, and uses the transparent plastic to have a lower light transmittance to the laser with a wavelength of 1700nm to 2000nm, so that the transparent plastic is welded During welding, there is no need to add absorbent to improve welding efficiency; at the same time, heat sinks are used to dissipate heat from the upper transparent plastic to avoid burning of the upper transparent plastic due to excessive temperature.

Description of drawings

Fig. 1 is the flow chart of the steps of transparent plastic welding method in an embodiment;

Fig. 2 is the welding schematic diagram when the laser welds the transparent plastic in one embodiment;

Fig. 3 is a comparison of the welding effect when the laser is welding transparent plastics at 1mm/s and 2mm/s respectively in one embodiment;

Fig. 4 is a cross-sectional view of a weld seam of a transparent plastic according to an embodiment.

Detailed ways

In order to facilitate the understanding of the present invention, the present invention will be described more fully below with reference to the associated drawings. Preferred embodiments of the invention are shown in the accompanying drawings. However, the present invention can be embodied in many different forms and is not limited to the embodiments described herein. On the contrary, the purpose of providing these embodiments is to make the disclosure of the present invention more thorough and comprehensive.

It should be noted that when an element is referred to as being “fixed” to another element, it can be directly on the other element or there can also be an intervening element. When an element is referred to as being "connected to" another element, it can be directly connected to the other element or intervening elements may also be present. The terms "inner", "outer", "left", "right" and similar expressions are used herein for the purpose of description only and do not represent the only embodiment.

Referring to Fig. 1 and Fig. 2, a kind of transparent plastic welding method in one embodiment, this method comprises steps:

Step S110, stacking the two transparent plastics 21 and 22 to be welded;

Step S120, covering the upper transparent plastic 22 with a cooling fin 23;

Step S130, using a laser L with a wavelength of 1700nm-2000nm to sequentially pass through the heat sink 23 and the upper transparent plastic 22, and focus on the joint surface c of the two transparent plastics 21, 22 to weld the two transparent plastics 21, 22 together .

In this embodiment, when the transparent plastics 21 and 22 are welded with the laser L having a wavelength of 1700 nm to 2000 nm, the light transmittance of the transparent plastics 21 and 22 in this wavelength range is relatively low. For example, taking the laser L with a wavelength of 1940nm as an example, the light transmittances of the transparent plastics 21 and 22 selected from polyamide, copolyester and polycarbonate at this wavelength are 70%, 42% and 72% respectively. The low light transmittance indicates that the transparent plastics 21 and 22 have a higher absorption rate for the laser light L in this wavelength range, so that when the laser light L in this wavelength range is used to weld the transparent plastics 21 and 22, there is no need to add an absorber, only the The laser light L in this wavelength range is focused on the joint surface c of the two transparent plastics 21 and 22, and the transparent plastics 21 and 22 will absorb the laser energy to melt and be connected together after cooling. In addition, in this embodiment, the upper transparent plastic 22 is covered with a heat sink 23, so that when the laser L welds the two transparent plastics 21, 22, the heat sink 23 can have a better heat dissipation effect and effectively avoid the upper layer. The transparent plastic 22 burns because the temperature is higher than the melting point.

In step S130, when the laser L is focused on the joint surface c of the two transparent plastics 21 and 22 for welding, the surface of the heat sink 23 away from the upper transparent plastic 22 is pressurized, so that the heat sink 23 and the upper transparent plastic 22 are closely attached together, absorb the heat of the transparent plastic 22 of the upper layer, and eliminate the problem of melting and burning of the transparent plastic 22 surface of the upper layer. In addition, the pressure of the heat sink 23 on the upper transparent plastic 22 makes the two transparent plastics 21 and 22 closely adhere to each other during the welding process without expanding due to heat, and finally makes the joint surface c between the two transparent plastics 21 and 22 The weld seam is relatively smooth and flat.

In some embodiments, the infrared transmittance of the two transparent plastics 21 and 22 is 65% to 75% at a wavelength of 1700nm to 2000nm, so as to ensure that the transparent plastics 21 and 22 have a better absorption effect on laser energy in this wavelength range , at the same time, also maintain the better transparent effect of the transparent plastic 21,22.

The material of transparent plastics 21,22 is selected from one of polyamide, copolyester and polycarbonate or at least two copolymers in the monomers of the above-mentioned polymers, while ensuring the cleanliness of transparent plastics 21,22 At the same time, the transparent plastics 21 and 22 can effectively absorb the laser light L with a wavelength of 1700nm-2000nm, so that they can be welded together without using an absorber.

The materials of the two transparent plastics 21 and 22 are the same, so that the welding effect is relatively uniform and no color difference will be formed between the transparent plastics 21 and 22 .

In some embodiments, during the welding of the transparent plastics 21 and 22 by the laser L, the heat sink 23 and the two transparent plastics 21 and 22 may be pressed and fixed by a clamp. On the one hand, it prevents the welding effect of the transparent plastics 21 and 22 from shifting during welding; on the other hand, the heat sink 23 and the two transparent plastics 21 and 22 are closely attached to each other by using the clamping force of the fixture. , so that the welding seam is relatively smooth and flat, and the abutment surface of the heat sink 23 and the upper transparent plastic 22 is relatively uniform, thereby improving the heat dissipation effect.

It should be noted that, in the above embodiments, the transparent plastics 21 and 22 have a relatively low transmittance under the laser light L with a wavelength of 1700nm to 2000nm, so that the transparent plastics 21 and 22 can effectively absorb laser energy. At the same time, it is necessary to use the cooling fins 23 to timely dissipate heat to the upper transparent plastic 22, and keep the temperature of the upper transparent plastic 22 at a level lower than its melting point all the time, so as to avoid burning due to excessive temperature. It can be seen that, when selecting the material of the heat sink 23, two factors should be considered: first, the heat sink 23 needs to have better infrared transmission performance, so as to reduce the energy loss when the laser L passes through as much as possible; second, The heat sink 23 needs to have better thermal conductivity, so as to quickly dissipate heat to the upper transparent plastic 22, so as to prevent the temperature of the upper transparent plastic 22 from being too high. As in this embodiment, the thermal conductivity of the heat sink 23 at 150-200° C. is 1-1.2 W/m·K, and the absorption loss of the laser light L is not higher than 5%.

Specifically, the selection of materials for the heat sink 23 mainly includes quartz-based glass materials containing SiO2, germanate-based glass materials containing GeO2, aluminate-based oxidized glass materials containing Al2O3, sulfide-based glass materials, and chalcogenide glass materials. Material. These materials all have good heat dissipation performance. Considering the permeability of the material to the laser light L with a wavelength of 1700nm to 2000nm, in this embodiment, the material of the heat sink 23 is quartz glass, and the infrared transmittance of the quartz glass is more than 95% at a wavelength of 1700nm to 2000nm. When the quartz glass radiates heat to the upper transparent material, the quartz glass will not absorb a large amount of laser energy, so that when the laser passes through the quartz glass and is incident on the joint surface c of the two transparent plastics 21, 22, the energy loss is small, and the laser energy be absorbed by the transparent plastics 21, 22 as much as possible, and finally the two transparent plastics 21, 22 are welded together.

With reference to FIG. 3 , FIG. 3 shows a comparison of the welding effects when the laser L welds the transparent plastics 21 and 22 at 1 mm/s and 2 mm/s respectively.

Specifically, after the laser L is focused on the joint surface c between the two transparent plastics 21 and 22, the welding is performed along a straight track. The wavelength of the laser L used is 1940nm and the power is 30W. When the welding speed is 1 mm/s, the weld seam a ₁ is formed. Correspondingly, when the welding speed is 2 mm/s, the weld a ₂ is formed. It can be seen from Fig. 3 that bubbles b appear at the tail of weld _a1 . This is because at the end of the welding process, the tail of the weld is in a high-temperature melting state, and the polymer material decomposes, and the gas cannot be released in time and remains in the weld. The edge of the weld seam cools faster, therefore, when the cooling ends, the remaining gas forms bubbles b inside the weld seam. In contrast, when the welding speed is increased to 2mm/s, no air bubbles will be generated in the formed weld _a2 . It can be seen that when welding transparent plastics 21 and 22, it can be avoided by increasing the welding speed. Bubbles appear at the tail of the weld and cause welding defects.

In some embodiments, the transparent plastics 21 and 22 are welded at a speed of 2 mm/s to 4 mm/s, thereby effectively avoiding bubbles at the tail of the weld during the welding process, and also avoiding excessive welding speed and transparent The laser energy absorbed by the plastics 21 and 22 is too little to affect the welding quality.

As shown in FIG. 4 , the cross-sectional shape of the weld a at the joint surface c of the two transparent plastics 21, 22 is elliptical. It can be seen that when the laser L is focused on the joint surface c of the two transparent plastics 21, 22 for welding, The two transparent plastics 21, 22 can absorb laser energy uniformly to melt, and weld together after cooling. In addition, it can be seen from FIG. 4 that when the transparent plastic is welded by the welding method of this embodiment, there are no bubbles and debris inside the weld a after welding, and the transparent plastic 22 of the upper layer and the transparent plastic 21 of the lower layer are completely fused. Together, the welding effect is better.

The technical features of the above-mentioned embodiments can be combined arbitrarily. To make the description concise, all possible combinations of the technical features in the above-mentioned embodiments are not described. However, as long as there is no contradiction in the combination of these technical features, should be considered as within the scope of this specification.

The above-mentioned embodiments only express several implementation modes of the present invention, and the descriptions thereof are relatively specific and detailed, but should not be construed as limiting the patent scope of the invention. It should be pointed out that those skilled in the art can make several modifications and improvements without departing from the concept of the present invention, and these all belong to the protection scope of the present invention. Therefore, the protection scope of the patent for the present invention should be based on the appended claims.

Claims (10)

1. a kind of transparent plastic welding method, which is characterized in that the method comprising the steps of：

Two clarity plastic layers to be welded are stacked and are set；

Cooling fin is covered on the transparent plastic in upper layer；

It is that the laser of 1700nm~2000nm penetrates the cooling fin and in the transparent plastic on upper layer successively, and gathers to use wavelength Coke welds together two transparent plastics in the joint surface of two transparent plastics.

2. transparent plastic welding method according to claim 1, which is characterized in that it is described to focus on two in the laser When the joint surface of bright plastics is welded, in surface-pressure of the cooling fin far from the transparent plastic.

3. transparent plastic welding method according to claim 1, which is characterized in that the material of the transparent plastic is selected from poly- One kind in amide, copolyester and makrolon or at least two copolymer in the monomer of above-mentioned polymer.

4. transparent plastic welding method according to claim 1, which is characterized in that the wavelength of the laser be 1940nm, Power is 30W, and is welded to the transparent plastic with the speed of 2mm/s~4mm/s.

5. transparent plastic welding method according to claim 1, which is characterized in that the laser to the transparent plastic into During row welding, the cooling fin and two transparent plastics are fixed by fixture.

6. according to claim 1-5 any one of them transparent plastic welding methods, which is characterized in that the material of the cooling fin For quartz glass.

7. transparent plastic welding method according to claim 6, which is characterized in that the ir transmissivity of the quartz glass It is 95% or more under 1700nm~2000nm wavelength.

8. transparent plastic welding method according to claim 1, which is characterized in that the cooling fin is at 150~200 DEG C Thermal coefficient is 1~1.2W/mK, and is not higher than 5% to the absorption loss of the laser.

9. transparent plastic welding method according to claim 1, which is characterized in that the infrared transmission of two transparent plastics Rate is 65%~75% under 1700nm~2000nm wavelength.

10. transparent plastic welding method according to claim 9, which is characterized in that the material phase of two transparent plastics Together.