Thanks to everyone, finally got K40 laser functioning. After about 4 hrs of use, the laser can barely mark a piece of foam board never mind cutting it. Cleaned mirrors/lens, centered mirrors, no help. Checked power supply. At full power it is giving 19.6 mA. Is this the problem?
Thanks
Make sure you have the material at the right focal length distance for your lens (might be too low) and if that’s OK, flip your lens over.
19.6 is way too much. You shouldn’t push that tube much past 16mA.
Is your water flowing ok?
It’s either the alignment or as @Jim_Hatch has stated the focal length is way off.
Thanks for the responses. 19.6 mA is what the PS ran at when I tested it. I usually run 10-15 mA. Focal length is 50.7 mm. According to Lightobject lens is supposed to be 50.8. Water is flowing fine. I flipped lens. no result. Night before this happened it was cutting 1/16 maple like paper at 5 mm/sec.
One other thing. In the past, when centering the mirrors, the beam would burn a relatively round hole in the paper. Now it is burning a “reverse L” when I align the mirrors.
Is it burning that right out of the tube?
It’s burning that at the cutter head. I will check right at the tube.
Right at the tube it is burning a round hole.
Cracked/scorched mirror? if so, what would be the cause?
Dirty mirrors…when dirt builds up on them they tend to get burn marks on them.
@Scott_Thorne Yep. The L shape says something is disrupting the beam. Dirt or a crack.
Holding both mirrors in my hand. Neither looks cracked or dirty. Later tonight I will super clean and reinstall them. Right now, SWMBO says that if I don’t take her to dinner, she will stop functioning. 
Thanks for the help. Will keep you posted.
@Wayne_Herndon Check the lens too. Is there any water on it (that will mess it up)? You can see if there is an internal crack by repositioning the mirror so the beam hits off center. If the L spot is now a circle again that points to a lens flaw.
@Wayne_Herndon You have 3 not 2 mirrors. 2 external and one in the head.
Standard K40 has a 50.8 mm or 2 inch focal length. Ideally the lens to the target should be that length.
Finally back. All 3 mirrors have been cleaned. The beam is centered. The lens has been flipped and flipped again. Now it will not even mark foam board. I am running out of ideas except for the tube.
@Wayne_Herndon Did the reverse L shaped spot go back to a circle? Does it burn a hole in paper or cardboard placed in front of the final mirror? If not at 5ma, what about 10 or 15ma?
@Wayne_Herndon also, you said it was a LightObjects lens. Are you sure it’s a 50.7mm focal length? They have other lenses with different focal lengths. I’d put a ramped piece of material in there with the base as low as possible and the top edge up near maximum height that still clears the lens - maybe 10mm. Fire the laser at 10 or 15ma the whole length. If it does mark/cut somewhere in there, measure that to find out what the focal length is.
@Wayne_Herndon …make sure that the beam is not hitting the side of the head before it gets to the lens…I’ve had that problem before.