For fine tabletop welding, particularly on thin aluminum and stainless steel, a QCW laser is usually the better fit than a continuous-wave (CW) laser. It is gentler on the part. It is not gentler on people, and that difference is the subject of this article.
The two lasers in brief
QCW (quasi-continuous wave) fiber lasers fire short, controlled pulses with high peak power and low average power. Less heat soaks into the part, so there is less warping and discoloration and a much lower risk of burning through. That suits thin, delicate work and gives precise starts and stops.
CW fiber lasers produce a continuous beam. The average power stays high and heat builds up, so thin parts can warp or burn through. CW is the better choice for thicker material and fast, uninterrupted production.
Why QCW suits the bench
A QCW laser hits the joint with short, intense pulses, and the metal cools a little before the next one arrives. The peak of a pulse can be up to about ten times the average power. The Ascent QCW tabletop and handheld welder, for example, has a 300W QCW source whose pulses peak at up to 3,000W. The result:
- Cleaner, sharper welds
- A smaller heat-affected zone
- Less warping and staining
- Less chance of burning through
- Finer control on small details and corners
- Good results on thin aluminum and stainless steel
Safety is the same for both
QCW welds with less heat, but it is not eye-safe. A QCW welder and a CW welder of this power are both Class 4 lasers. A direct beam, a bright reflection or even scattered light can injure eyes or skin in an instant, and both are fire hazards. Enclosure, fume extraction, training and laser eyewear are required either way. Minimum OD 5; prefer OD 7 or 8. OSHA's laser hazard guidance applies to every setup.
| Factor | QCW laser | CW laser |
|---|---|---|
| Heat into the part | Pulses with pauses, so the part usually runs cooler | Constant power, so the part heats quickly |
| Thin metal | Lower risk of burn-through and warping | Higher risk |
| Fire risk at the part | Often lower, with less sustained heat | Higher |
| Eyes and skin | Hazardous | Hazardous |
| Reflections | Dangerous, especially off shiny aluminum and stainless | Dangerous in the same way |
What a camera does and does not do
Many tabletop welders let the operator line up the joint on a CCD camera instead of looking at it directly. The Ascent QCW welder has a CCD camera system and a dedicated monitor for this. A camera helps the operator place the weld precisely and keeps their face away from the work.
A camera is not a safety system on its own, though. Unless a machine is a fully enclosed product designed and certified so that no one can be exposed during normal use, Class 4 precautions still apply. For an enclosed system, the things that make it safe are:
- A closed chamber that keeps the laser light inside
- An interlock that switches the laser off when a door opens
- Viewing windows, if any, rated for the laser's wavelength and power
- Interior surfaces and a beam stop that safely absorb stray beams
- Emergency stop and key-switch controls
- Fume extraction
For an open bench or handheld setup, the work area needs laser-rated partitions, controlled entry and laser eyewear for everyone inside. The Ascent QCW welder comes with laser safety glasses or a laser helmet, and we recommend wearing them.
So is QCW safer?
For the part, yes. Pulsing lowers the odds of distortion, overheating and burn-through, because less average energy reaches the metal. For people, no. Each pulse still carries enough power to cause an instant, serious eye or skin injury. Choose QCW for the quality of thin-metal welds, and plan the same Class 4 safety either way.
For help laying out a safe station, see our laser safety page or contact us. Installation and operator training at your facility are included with the Ascent QCW welder, and it has a 1-year parts-and-labor warranty.
