The best way to deal with surface burns during laser welding of PBT materials

Material Introduction

PBT is a milky white, translucent to opaque, crystalline thermoplastic polyester. Due to its heat resistance, weather resistance, drug resistance, good electrical properties, low water absorption and good gloss, PBT is widely used in electronic appliances, automotive parts, machinery, household products, etc.

Difficulties of PBT laser welding

Plastic laser welding technology requires that the upper plastic can penetrate the laser and the lower plastic can absorb the laser energy. The most commonly used combination of plastic laser welding of PBT material is.

1. Natural color PBT + black PBT

2. Black PBT + black PBT

Natural color PBT plastic can penetrate lasers regardless of whether glass fiber is added; if black PBT plastic is to be used as a penetrating part, a special brand of PBT material is required. PBT is a semi-crystalline material and is not suitable for laser plastic welding with a laser wavelength of 808nm. For some brands of PBT materials, the laser penetration rate of 940nm and 980nm is very low. For PBT plastic with a thickness of 1mm, the laser penetration rate may be less than 10%, which is not conducive to laser welding. Taking BASF's Ultradur series PBT type black laser penetration test piece as an example, a 1mm thick test piece can obtain a better processing effect, and a 2mm thick test piece has a significantly reduced process window and welding effect. If automotive electronic products are designed with PBT materials, it is recommended that the thickness of the laser penetrating part be less than 1.5mm. In addition to the low laser penetration rate, the surface of PBT material easily absorbs laser energy, resulting in burns during laser welding.

In response to the problem of low laser penetration rate of PBT material, foreign companies such as BASF of Germany and Panasonic of Japan have launched high-penetration PBT materials for plastic laser welding. However, in actual large-scale production, PBT top covers are often burned by lasers.

How to laser weld PBT plastic?

Using high permeability PBT material is the best way to solve the surface burns during PBT material welding. Imported materials, such as BASF's ULTradur series and domestic materials, such as ECOTLEW series.

In addition, the use of special fixtures is another effective way to solve the burns of laser welding PBT materials. Using laser welding process, continuous cooling of the penetrating weld surface can reduce burns to the plastic surface.

If workers want to do their job well, they must first sharpen their tools. Good laser plastic welding equipment can also reduce the probability of burns on PBT plastics during laser welding. The imported laser welding equipment uses a high-brightness light source with good beam quality. Some laser welding equipment suppliers have also adopted special spot forming technology, which makes the spot distribution and energy density distribution more reasonable when laser welding PBT plastics. In addition, the current equipment also has welding process monitoring and quality monitoring, which can greatly reduce the probability of PBT surface burns through closed-loop monitoring of welding temperature.