Welding of uncoloured plastics with the laser
In laser welding of plastics, the laser beam penetrates the upper, transmissive component and is absorbed in the lower component. In order for the laser energy to be absorbed in the lower joining partner, an additive (e.g. carbon black) is usually compounded into the lower component to provide it with absorbing properties. This enables heat to be introduced in the lower joining partner during the welding process and thus the necessary process heat required to produce the weld seam between the two joining parts. Usually, a laser beam with a wavelength in the range of 800 to 1100 nm is used for this. Thermoplastics are used as material.
But is laser welding of plastics also possible with uncolored material? Particularly in medical technology applications, the addition of soot leads to an optically undesirable color impression and is not conceivable for hygienic reasons. Moreover, the addition of additives during medical approval and in the upstream injection molding process leads to higher costs, especially for high volumes.
Here again, the laser shows its strengths compared to other joining methods! The solution is the use of a laser beam with a special wavelength in the range of 1500 - 2000 nm (1.5 to 2.2 µm). With the so-called 2 µm process, two workpieces can be joined without additional absorber. Clear-clear welding exploits the property of some thermoplastics to absorb wavelengths above 1500 nm more strongly in their uncoloured natural state. In contrast to the conventional transmission method, the heat input of the laser takes place in the complete volume which is irradiated and transmitted. A different beam shaping is also used. The two joining partners plasticize in the joining zone and form a safe and optically attractive weld seam.
In principle, all thermoplastics such as PA, PP, PC, COC, PMMA, MABS and PS can be used for 2µm welding. Evosys Laser has already successfully tested many of these materials and has a lot of experience in using this process. EVOSYS can also offer suitable automation solutions and integration modules in terms of system technology.
Current applications and developments show that the 2µ process is in many cases not only a clean but also an economical alternative to other joining processes. A detailed process description and further information can be found here.
May we help you for your special application that is suitable for clear-clear welding? Talk to our specialists at Tel. +49 9131 - 81497 - 29 (Mr. Holger Aldebert) or by e-mail to firstname.lastname@example.org.