 What
is laser welder? |
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It is a technique to weld two moldings with the energy of laser light. The point is how to combine the "laser-transmitting material" with the "laser-absorbing material." See the figure below. The laser light that has been irradiated from above passes through the upper "laser-transmitting material" as it is, and is absorbed by the lower "laser-absorbing material." As a result, heat is produced at the interface between the moldings, which melts the resin there, and the two moldings are welded. |
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| Features
of laser welder |
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 Advantages |
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- Being free from physical stress like
vibrations or ultrasonic waves, it can also be applied to
precision components.
- Due to non-contact welding, no thermal effect, scar, or deformation is generated on the surface.
- It is a clean processing method that produces no dust or flash.
- Optimum processing conditions make it possible
to obtain high bonding strength and hermetic performance.
- Thermal effect can also be minimized by making the beam size smaller.
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 Disadvantages |
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- There are restrictions on the materials that can be used (it must be used by combining laser-transmitting materials with laser-absorbing materials)
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| Outline
of a laser welding process |
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The equipment consists of a clamp that fixes a product and a laser irradiation device.
The process includes the following 4 steps. |
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Also, laser welding can be classified into the 3 types: path welding, simultaneous welding, and mask welding, according to the laser irradiation method. |
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| Welding
conditions |
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The following is the 2 setting conditions required in laser welding.
(1) Laser power
(2) Scanning speed
Laser power is the amount of heat that melts resins. Scanning
speed is a speed at which the laser beam travels. Considering
productivity, the scanning speed should be increased and the processing
time should be shortened, and the output should be increased correspondingly.
But too high an output may cause excessive decomposition at the
absorbing material side, resulting in deformation, and therefore
with regard to this point, the point at which the welding performance
of the product stabilizes most should be searched through verification
of actual products.
Also, the following 2 points are important in selecting materials.
(3) Light transmissivity of the laser-transmitting material
(4) Thickness of the laser-transmitting material
The welding of materials is dependent on the amount of energy of the laser beam that reaches the laser-absorbing material. Therefore, light transmissivity and thickness at the laser-transmitting material side affect welding greatly. Higher light transmissivity gives greater advantages to welding. Smaller thickness is likewise more advantageous to welding. |
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As an example, the relation among welding strength, laser traveling speed, and laser output is shown in the graph below. It can be seen that as the laser output becomes higher and the traveling speed becomes lower, the welding strength becomes higher. |
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Materials: M90-44 natural vs. M90-44 black |
| Performance
comparison between laser welder and other welding methods |
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Laser welder gives higher welding strength than other welding methods like vibration welding and ultrasonic welding.
The result of performance comparison with ultrasonic welding and vibration welding is shown below. |
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Materials: M90-44 natural vs. M90-44 black
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| Durability
of welded portions |
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The durability of laser welding is very good. Even after a heat
shock (-40°C  120°C  30
min.) had been repeated for 2000 cycles, no air leakage occurred
at an internal pressure of 0.6 MPa, and there was no decrease
in welding strength either. In the example given below, a test
was conducted by increasing the scanning speed to 30 mm/sec. In
this case the welding strength decreased by half, but there was
no problem in the durability. |
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Laser Welder
