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Your laser lost power - check the cheap things first
A job that cut in one pass last month now needs two. Before you price a replacement tube or diode module, work down this list. Nine times out of ten it is a dirty lens, and that is free.
Check your job time →1. Optics first, because smoke film is invisible
A lens does not have to look dirty to have lost you 30% of your power. A thin smoke film absorbs energy before it ever reaches the material, and it builds up gradually - which is exactly why the loss feels like the machine 'wearing out'. Clean every optical surface in the path: the lens, the protective window, and on CO2 machines all three mirrors. Use isopropyl and a proper swab, and do not scrub.
2. Check the lens went back in the right way round
A convex lens has an orientation, and it is easy to reinstall inverted after cleaning. Inverted, it still focuses - just not where the machine expects - so you get weak, wide cuts that look like a power problem. If power dropped immediately after a clean rather than gradually, this is the first thing to check.
3. Focus and material flatness
Before blaming hardware, confirm the focus is genuinely correct for the material in front of you and that the sheet is flat. An out-of-focus beam is a weak beam. This costs nothing to rule out and is a common cause of 'it used to cut this'.
4. Cooling, on CO2 machines
A CO2 tube's output falls as its coolant warms. If your water sits well above room temperature by the end of a long session - or the chiller is undersized or alarming - power drops off through the day and recovers overnight. That pattern, strong in the morning and weak by the afternoon, points straight at cooling rather than at the tube itself.
5. Nozzle, air and beam path
A partly blocked nozzle or an off-centre beam clipping the nozzle edge both waste power. Tape over the nozzle, pulse at low power and confirm the mark is central. On CO2 machines, drifting alignment shows up as power that is fine in one part of the bed and weak in another - that is alignment, not tube death.
6. Only then, the tube or diode
CO2 tubes genuinely wear out, typically over years, and the symptom is a slow decline that survives clean optics, correct focus and good cooling. Diode modules degrade too, though usually less gracefully. If everything above checks out and current draw looks normal while cuts keep getting worse, the source is a fair suspect - but it should be the last one, not the first.
Rule of thumb: Order matters: optics, lens orientation, focus, cooling, nozzle and alignment, then the source. Every step above the last one is free.
Open the calculator →FAQ
Why did my laser suddenly lose power?
Most often a smoke film on the lens or mirrors, which absorbs energy before it reaches the material and builds up gradually. Clean every optical surface before suspecting the tube or diode.
Can a dirty lens cause power loss?
Yes, and it is the most common cause. The film does not have to be visible to cost a significant share of your power.
My laser is weaker in the afternoon than the morning - why?
On a CO2 machine that pattern points at cooling. Tube output falls as coolant warms, so an undersized or struggling chiller shows up as power that declines through the day and recovers overnight.
How do I know if my CO2 tube is dying?
A slow decline over months that survives clean optics, correct focus, good cooling and proper alignment. Rule those out first, because they are free and far more common.