Laser Plastic Welding FAQ

Find answers to all of your questions about laser plastic welding. Start with our list of commonly asked questions. If you can’t find the answer you are looking for, ask your own question using the form at the bottom of the page.

What materials can be laser welded?

Most thermoplastic materials can be laser welded. The general rule of thumb is if they can be welded with another joining technology, they can be welded with laser. The two materials being welded together should be similar. Meaning, they should have the same chemical structure, overlapping melt temperatures, and their melt flow index should be of the same order.

How strong are laser welded parts?

Typically, laser welded parts are stronger than ultrasonic welding, and at least as strong as hot-plate and vibration welding.

Does the top part material have to be transparent to be laser welded?

Yes and no. The top part can look opaque, even black, to the human eye and still be able to be laser welded. It just needs to be transmissive at the correct IR wavelength. There are ways to color plastic parts that make them look opaque while still being transparent to IR energy.

Do parts need to be clamped together during laser welding?

Yes, the parts need to be clamped together throughout the entire laser plastic welding process in order to ensure intimate contact along the entire weld surface. Any areas of the weld joint that aren’t touching will result in a weak spot or no weld.

Can glass-filled material be laser welded?

Yes, glass-filled material can be laser welded. The glass content should be kept under 35%. Glass content tends to scatter the laser energy. So, the cycle time may increase. Read our blog post about using laser to weld glass-filled parts for a clean assembly.

What is the maximum allowable thickness of the top part in laser welding?

The transmissive part should be approximately 3 mm thick or less for semi-crystalline materials and can be much thicker for amorphous materials as long as they are transparent. If the transmissive part has a glass filler, the maximum allowable thickness decreases as the filler percentage increases due to scattering of the laser energy.

Is laser welding safe?

Yes, we have a certified laser safety officer that ensures each laser welding machine we build is safe to use. The laser safety officer can even visit your manufacturing facility to certify your equipment on site.

Does the laser beam have to be perpendicular to the parts or can you apply it from an angle?

Laser energy can be applied at an angle in some cases. Also, mirrors in the tooling can be used to reflect the laser energy at unique angles which allows us to weld undercuts and perpendicular ribs. Read our blog post about using mirrors in laser plastic welding.

Can laser plastic welding be used on two clear parts?

Yes, laser can weld two clear materials together. There are several ways to accomplish this type of welding: topically adding absorptive material, adding absorptive material to the polymer blend before injection molding, or using a method called 2-micron welding.

Is the clear absorptive additive material for laser plastic welding FDA approved?

Yes, there are FDA approved materials available from multiple suppliers.

Does weld depth affect the strength of the laser welding bond?

Yes, to a point. In laser welding, the typical weld depth/collapse is 0.1 – 0.5 mm. The greater the weld depth, the more part to part variation the process can accommodate.

Can you clamp parts that aren’t flat?

Yes, we make custom tooling that fits the parts. The tooling allows us to clamp parts with unique, non-flat features. Small windows in the custom tooling allow the laser beam to reach the weld.

Can laser welding work for round parts as a replacement for spin welding?

Yes, laser welding can be used to weld round parts. Read our blog post about using mirrors to weld cylindrical parts.

What type of laser does Extol use?

Most of our applications use an air-cooled, military-grade, direct diode, 980 nm laser from an American supplier. We configure our laser welding solutions around what the application requires and can utilize other wavelengths when necessary.

Is it okay to have ejection pin marks on the weld surface?

No. Laser plastic welding technology will not weld wherever there is a gap between the two surfaces. Ejection pins often leave behind an uneven surface that will have an adverse effect on the weld.

Does laser plastic welding emit smoke or off-gassing?

When the process is correctly optimized, there is usually no off-gassing. However, in cases where there is slight off-gassing, we are able to mitigate the effects. We use both positive airflow to move the smoke away from the weld and a negative airflow exhaust system to evacuate the air from the weld chamber.

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