Help! Power set to high but output is low, not able to cut.

[Robin Croen]

Greetings all, I hope you can weigh in on a problem I'm having with my new-to-me machine.

I recently bought a used China red, 1400 x 900 130w, Ruida 6442 controller, laser power upgraded to a lightobject PSU by previous owner. I tested it out with the seller and it cut through 5mm ply without breaking a sweat. This was about 4 weeks ago.

Fast forward to this weekend. I'm excited to finally get this thing going after doing some tune-up work and getting my space set up. I've gone through the process of leveling the table, aligning the mirrors and focusing the beam and everything seems spot on. I've calibrated my max power using a newly-installed analogue ammeter; 60% power in the software gives me 28mA on the meter (tube specs called for 30mA max operating power and I figured I'd go a little low).

I fired up a test file from RDworks, a 20mm square on 5mm ply. The resulting "cut" was a disappointing burned outline barely deep enough to snag a fingernail. I've only tried the ply so far but based on that I don't think I'd be able to even cut 1/8" MDF. The settings were as follows:
From RDworks, I made a cut layer with max and min power both set to 100%, which if I understand correctly means I should be getting 100% of the 60% that I set as my software max. I set the max power on the machine control panel to 60% as well, which is the max allowed to me with the current software settings.
Speed set to 10mm/s.
Air assist is on.
Chiller is on and easily holding at 18C.
When cutting, I verified that the laser was firing at my full power setting of 60% via the ammeter which held steady at 28mA during the cut.
I verified that there was a visible purple beam inside the tube, see pics.
I've double checked the mirror alignment and beam focus, made some tweaks to improve conditions.
I double checked the lens orientation, its convex side is facing up and flat side is facing down towards the table.
I cleaned all three mirrors and the lens with DNA. The mirrors have some marks and spots that I was unable to remove, see pics.

Imgur album: https://imgur.com/a/LHfwNgC

What am I missing here? This is a used tube, but considering that the machine has been run less than an hour total since it was last able to cut through 5mm ply would it really go dead on me so fast? And if it was going dead, would the ammeter still be reading my max power setting of 28mA? I'm hoping that this user error and the right settings will solve the problem.

I've spent many hours googling and combing through the forums for answers and I'm at a loss for what to try next. Thank you all in advance for your help!

[sebastien laforet]

not sure, but your burn mark seems waaaaay too large.

is the focus ok? you should not try to burn through anything until you get a fine line when "marking". if you can't get a hair-thin line at low power, this is bad : either your mirrors, your lens, your focal distance.

most chance is that you are ok until 3rd mirror, then after 3rd mirror the beam is not vertical and hits inside the nozzle. thus, you lose an awful lot of power and the beam is not converging on the target, you have a diffuse beam that burns a large line instead of a fine one.

one test is to move your head at a fixed point, "pulse" and make the height/Z of the table change. if the burned point is moving in X/Y as the head does not, it's a clear sign your beam is not vertical.

[Dave Vigness]

Hey Robin, good to see you here.

Didn't think about that. Center of #3 has no relationship to center of the lens. Drop the lens tip off and put some tape across the bottom of the tube. That will get you a rough idea on centering. Also do like Sebastian said. Set a piece of paper and do a pulse, then drop the bed at least 100mm and do it again. They should line up just like #2 and #3 did at opposite ends of the travel. You need to be parallel and centered on the lens.

[Jeffrey Aley]

I'd also try a different material. You could have ended up with some plywood with a glue that is not laser-able.

Try some solid wood or some acrylic.

[Robin Croen]

not sure, but your burn mark seems waaaaay too large.

is the focus ok? you should not try to burn through anything until you get a fine line when "marking". if you can't get a hair-thin line at low power, this is bad : either your mirrors, your lens, your focal distance.

most chance is that you are ok until 3rd mirror, then after 3rd mirror the beam is not vertical and hits inside the nozzle. thus, you lose an awful lot of power and the beam is not converging on the target, you have a diffuse beam that burns a large line instead of a fine one.

one test is to move your head at a fixed point, "pulse" and make the height/Z of the table change. if the burned point is moving in X/Y as the head does not, it's a clear sign your beam is not vertical.

Thanks for the reply Sebastian. I think the burn mark is so large here because I’m cutting slowly, if I dial the power back I can get a very thin and clean looking line. That being said I’m sure the focal length isn’t calibrated perfectly, I haven’t been able to make any of the nifty tools that one would typically cut with the laser!

I’ll look more closely at the alignment at the head.

[Robin Croen]

I'd also try a different material. You could have ended up with some plywood with a glue that is not laser-able.

Try some solid wood or some acrylic.

I’m using a piece of ply that was previously cut on this same machine. It’s a piece of scrap with numerous cuts already in it.

[Robin Croen]

Hey Robin, good to see you here.

Didn't think about that. Center of #3 has no relationship to center of the lens. Drop the lens tip off and put some tape across the bottom of the tube. That will get you a rough idea on centering. Also do like Sebastian said. Set a piece of paper and do a pulse, then drop the bed at least 100mm and do it again. They should line up just like #2 and #3 did at opposite ends of the travel. You need to be parallel and centered on the lens.

Hi Dave, likewise.

I did do the vertical alignment test but I think perhaps this still deserves a second look. Going to mess with this part of the alignment again. The tricky part is that my laser head has some sticky mirror set screws and also doesn’t have a way to move the head assembly up and down. Looks like I’m going to be buying a new head as well as new mirrors and maybe (but hopefully not!) a new tube. Sigh.

Any recommendations on what to get for a new head assembly? I’ve watched Russ’s video about his universal nozzle and lens tube, seems like a good idea to build the system around using those parts.

[Dave Vigness]

Robin, If you are parallel all the way through from tube to Z but are not centered on the lens, then you need to look at what way you are not centered on the lens.

Front to back is easy, every laser has slots for the plate that the head mounts in. Left to right gets tricky depending on how far out you are and what direction. If you are too far left by a little, you can adjust your #3 mirror out evenly to move the beam reflection to the center of the lens. If you are out a lot you will need a spacer. I had to put a piece of 3mm acrylic AND move my mirror a bit to get it centered on the lens.

If you are out to the right a little, you MIGHT be able to tighten down #3 enough to get it there. If not, you have two choices. Wait until Cloudray released the adjustable in a few months, or raise your tube and start all over again in getting it parallel. If you were 'lucky' enough to be near the bottom on #1 and #2 you might get away with just raising the tube if you don't have to go too far.


On the focal length test. Here's a down and dirty one to at least get you started. Put a scrap strip of something on the bed, and put a piece of say 3/8" under one edge to give it a tilt. Set your head at roughly what you think the focus should be somewhere near midway of the slant. Run a line, and where your line is thinnest is your focal length. Take a scrap of something angled and make a mark for the gap and that will get you started until you can get more detailed measurements.

[Hank Morgan]

What is your MIN power setting?
Ruida controllers have a "Start Speed" setting that is usually set to 10mm/s as the default. At or below the Start Speed the controller defaults to the MIN power setting. Either turn up your MIN power, or turn the Start Speed down.
Or try cutting at 11mm/sec and see what that gets you.

ETA: I'm sorry, I reread your post and see you also had MIN set to 100%. So nevermind...

[Robin Croen]

What is your MIN power setting?
Ruida controllers have a "Start Speed" setting that is usually set to 10mm/s as the default. At or below the Start Speed the controller defaults to the MIN power setting. Either turn up your MIN power, or turn the Start Speed down.
Or try cutting at 11mm/sec and see what that gets you.

ETA: I'm sorry, I reread your post and see you also had MIN set to 100%. So nevermind...

No prob Hank, thanks for the reply. I've got some parts on order that should help me get the alignment dialed in. I'll post an update here when I do.

I appreciate everyone's help thus far.