Wuhan Questt Asia Technology Co., Ltd
Address:
A7-101, Hangyu building, Wuhan University Sci & Tech Park, East Lake High-tech Dev. Zone, Wuhan, Hubei, China
Email:[email protected]
17
German Technology | Made in China
breaker will be opened and the pre-burning circuit and main circuit will be disconnected,
resulting in the shutoff of the whole machine.
4-3 Optical system
Figure 4-1
Two off-focus modes are available: positive off-focus and negative off-focus. If the focal
plane is above the work piece, it is called positive off-focus, contrarily; it is called negative
off-focus. According to the theory of geometrical optics, when the positive off-focus distance
is the same as the negative off-focus distance, the power density on corresponding planes
will approximate to each other. However, the shape the obtained molten pool is different.
Under the circumstance of negative off-focus, the large penetration depth could be reached,
which is related to the forming of the molten pool. Experiments show that when the material
is heated by laser for 50
～
200us, it begins to be molten, forms the liquid-phase metal and
the evaporation appears to form the pressure-applying vapor that spurs at extremely high
speed with dazzling white light. At the same time, the high density gas moves the
liquid-phase metal to the edge of the molten pool to form the dent at the center of the molten
pool. Under the circumstance of negative off-focus, the power density inside the material is
even higher than the surface, which is apt to cause stronger melting and vaporizing that
Impact of Focus Setover on Welding Quality
The laser welding normally needs a certain degree of off-focus operation, for the welding
point can be vaporized into a hole if the power density at facula center of laser focus is
excessively high. The planes that are not with the laser focus will have relatively even
distribution of power density.
