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6 common problems in plastic laser welding

Release time:2023-05-06 10:05:40

【summary】

There will be a series of process problems such as shrinkage marks, burns, poor welding, etc. Pay attention to black nylon or PBT materials, whose production and injection molding process easily lead to unstable laser penetration rate of the workpiece after injection molding. Laser penetration detector can be used for detection.

鈻?amp;nbsp;What is the principle of laser transmission welding of plastics?

Laser transmission welding refers to the laser beam penetrating the upper transparent component and then being absorbed by the lower laser absorbing part. When the energy of the laser is absorbed by the dye or additive particles, it is converted into heat energy. The surface of the absorbing component melts and the heat is transferred to the upper transmitting component through heat conduction. Before welding begins, the two components are in contact with each other under the action of external force. During welding, the components are locally heated, which causes thermal expansion of the material and generates internal welding pressure. Under the combined effect of internal and external welding pressure, the two parts are firmly welded together. The relative movement of the laser beam and the welding parts forms the weld.


鈻?amp;nbsp;What problems will low laser penetration cause?

A series of process problems such as shrinkage marks, burns, and poor welding will occur. Pay attention to black nylon or PBT materials, whose production and injection molding process easily leads to unstable laser penetration rate of the workpiece after injection molding. Laser penetration detector can be used for detection.

6 common problems in plastic laser welding(图1)

鈻?amp;nbsp;UpperAre transmissive parts black weldable?

Weldable. Black plastics that are colored with special dyes or have laser absorbers added may also have sufficient laser transmittance. Consult with the material supplier and test.


鈻?amp;nbsp;What is a typical weld design?

For welding electronic components such as EPB electronic parking brake and thermal management expansion valve, the following weld design can be adopted. The weld width is 1.2mm, the welding depth is 0.4mm, and there are ribs inside and outside to prevent overflow and extrusion.


鈻?amp;nbsp;How to determine the thickness of the upper transmission component?

General principle, amorphous plastics such as PC, PMMA and ABS, etc., the mother without adding color is transparent, and there is no specific requirement for its thickness. But the thickness of welding semi-crystalline plastics is generally not more than 2 mm, because the mother without adding color is milky white or milky yellow. When containing glass fiber plastic, the thickness should be as small as possible on the basis of ensuring the mechanical properties of the parts.

1. It is recommended to use PBT material with a thickness of less than 1.5. mm.

2.If nylon material is used, the thickness is recommended to be less than 2mm.

3.If POM material is used, the thickness is recommended to be less than 3mm.


鈻?What quality control measures are there during laser welding?

Use a thermometer to detect the temperature of the welding pool in real time through infrared rays. Note that the temperature detected by the thermometer is a comparative value, not an actual value. The common quality monitoring method in the automotive parts industry is to use a displacement sensor to monitor the depth of welding collapse. Use a force sensor to monitor welding pressure.


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