Laser not cutting through

Hi Guys,
I have a Bodor laser with a 100watt Reci tube. It is new and has done 90hours. I am having trouble cutting through 4 mm plywood. I have used a 50.8mm, a 63.5mm and a 75mm focal length lens with the power anywhere up to 100% but still do not get through properly. I have varied the speed down to 8mm/sec which tends to burn too much despite not getting right through. Even with multiple pass and a step in the Z axis I do not get a clean through cut. I read about 100 watt laser cutting 12mm ply so am frustrated!
Any ideas where I could go next??
Thanks
Peter

Your 100W should go through 4mm plywood like butter. My 40W already does that :wink:

Your information is not very extensive, so I will ask the standard questions:

  • Are your mirrors properly aligned?
  • Are your mirrors clean?
  • is your focus lens clean?
  • Is your focus lens mounted the right way round?
  • Did you run a focus test to find out of what the ideal focus height is?
  • Did you check if your controller is outputting the desired power level?
  • Is there any other limit which can influence the power level? Maybe still a potmeter connected to power level pin of the laser power supply? Maybe even the controller has a hard limit on the power level?

Do you happen to have any pictures of your cuts?

Yes, check your beam alignment.

Also, if cutting at low speeds set MIN POWER the same as MAX POWER. At low speeds MIN POWER will be used all the time causing this problem. This got me once and was a real head scratcher.

I have the same tube and can cut 6mm baltic birch plywood at 15 mm/s and 75% power. The cut is clean with no charring on the surfaces and a medium brown colour.

Checking Min Power is my suggestion as well. Set Min & Max the same if you’re running at or below the ‘Start Speed’ setting in the controller (defaults to 10mm/sec).

Verify:

-Min / Max settings
-Focus
-Mirror cleanliness and alignment
-Lens orientation (That it isn’t upside down)
-Lens Clarity
-Actual mA draw
-Laser Tube output lens color and clarity (check reci on info about what color indicates on their tubes)
-Power Supply quality

If you have a w2:
http://www.recilaser.com/en/index.php?m=&c=Index&a=show&catid=7&id=66

If you have a w4
http://www.recilaser.com/en/index.php?m=&c=Index&a=show&catid=7&id=67

Also… do not run your power at 100% (or 90, 80, 70, 60, 50…) until you have verified the mA draw. If you over drive your laser tube, you will shorten its life. I am mentioning this because you said you are trying at 100% power.

For example, I have a 130 / 150W tube, but my laser power supply outputs a lot more (as I have not adjusted the pot on it). My max output setting is currently 62% on LB in order to maintain under 29 mA current draw on my Reci W6. Reci usually recommends less than or equal to 28 mA.

Everything above is great however what I would also really stress is high airflow. I thought my laser was having problems cutting until I increase the airflow to about 40 psi and opened it up a bit. Now it cuts like a charm.

I agree with Jeremy re: airflow.
Get lots of high speed air down in to that kerf to clear smoke & debris. It doesn’t take much smoke to absorb & diffuse most of your power, and cutting wood generates LOTS of smoke.
I usually run >30psi for cutting wood.

Other than that, what everyone else said… optics cleanliness and alignment, proper focus, and an mA meter to verify tube current. (which you should have anyway.)

Thank you all for the advice.
I have good alignment on the mirrors
Focus has been checked and is good.
Lens is clean and correctly mounted
Airflow - I have a Hailea ACO-009 air pump 195 watts, 120 l/min, >0.04MPS Not sure what that is in psi.
At 85% power and 6 mm/sec the tube is drawing 28 m amps. With those parameters I can barely cut through a soft piece of 6mm poplar plywood.
My next task is to clean the mirrors.
I have ordered another lens just in case that is the problem.
Where does that leave me?
Thanks guys

0.04 megapascals = about 5.8 psi.

WOW ! If it is only 5.8psi and folk are running at 30 psi I am way behind. That air pump was supplied with the machine.
What air pumps are you guys running?

5hp Ingersoll Rand.
I just plumbed a line from the shop compressor to the laser and stuck an inexpensive adjustable pressure regulator to the side of the machine.

If I was to buy a pump or compressor for that job I’d probably get one of those little $150 portables like this one or similar, since it would be useful for other stuff too.

image

These folks produce very quiet compressors.

https://www.ultraquietaircompressor.com/Special-Offers_c46.htm

My current setup which allow me to drive many of my air needs. https://www.californiaairtools.com/ultra-quiet-series-of-air-compressor-contractor-grade/2-0-hp-air-compressors/cat-10020ac/

Thank you guys. I have solved the problem. I went to clean the mirrors and found the first one i.e. next to the tube was terrible with pock markings +++.I hadn’t looked at that one previously as it was difficult to get at. I found a spare set of mirrors which had come with the laser and have installed those. Now it cuts 4mm ply at 85% power and a speed of 30mm/sec. Good enough!!
Cheers
Peter