Hey guys,
I have been having some strange issues with tiny dotted lines on the bottom side of my laser cuts (only noticeable on thicker material). I have been doing a lot of testing to try and figure out why this is happening. I just happened to check my tube while running today and noticed that when cutting with constant power (both min/max same) the tube flickers? This makes me think something may be wrong with either the tube or the PS or ???
My first and most obvious question is is my tube bad? Or could it be something else?
My second question is, would this cause my issues? In my tiny little brain, I am thinking it may be a factor.
How should I proceed? It is supposedly still under warranty, but not sure the seller will be any help or respond at all.
My machine specs:
90W Red & Black CO2 Laser
T series RECI tube
CW-5200 Chiller (set so the laser will not fire if there is no coolant flowing)
According to RECI “The Model T series tubes max operating current must be controlled at 28mA or less. And working life can reach 8,000 hours if the current is 24 mA or less.”.
As mentioned in the link above, I have set the PS so that when I am running 100% power it is maxing out at 24mA. And I have only ran it as high as 75% which only hit 17mA.
Also I would guess that I have less than 50 hours of run time on the laser.
My tube does the same thing. It’s almost 2 years old now. What do the dotted lines look like? Do they match up with what the project is sitting on? Might just be reflection back onto the project.
Funny you brought that up. I was just out taking some pics of the dotted lines on the back of the 1/4" boards. I don’t notice any dots on the 1/8" boards.
I will mention, for those that may not have seen my post about my serrated edges problem (towards end of thread), some areas I am seeing are very similar to those. We concluded (so I thought), after much testing, that there was some sort of bug in LB. It was associated with the kerf settings. I had to zero out the kerf settings to get rid of the serrated edges. That problem was very noticeable on 1/8" boards where I do not seem to notice this issue on the thinner stock (although I have not ran any thinner stock lately). But it is very noticeable on the bottom side of the 1/4" boards. I am beginning to think the serrated edge issue is not really resolved
While taking my pics, I noticed that the dotted lines are mostly where double sided tape was on the bottom side of the boards. On boards with no tape on the bottom side, the edges are more serrated than dotted. Because most of my recent work has been with the tape on the bottom side I assumed the issue was dotted lines.
Or that the controller shuts the laser off while repositioning the laser head to the start of the next vector. In your photos, the flicker might correspond to the larger burned points at the vertices of the shapes, where the head must (nearly) stop before changing direction.
That means the controller cannot modulate the beam power to match the laser head speed, which tends to cause overheating in the corners. Reducing the minimum power may reduce those conspicuous burns.
Those are good points and would make sense except that the video of the laser tube was taken while cutting a large square (straight lines/no changes in direction) at slow speed.
I set the test on constant power so that the flickering was not a result of the controller fluctuating the power for whatever reason.
So is this flickering normal? Am I concerned about nothing? If it is normal for the settings used, then I can move onto why I am getting the dots/serrated edges on the bottom edges?
Alright I woke up this morning on a mission to do a bunch of testing to try and figure out why my laser is flickering. The first thing I did was check the wires connected to the tube just to make sure there was not something loose. There wasn’t. I then decided to do another test to watch the tube and see if there is any arcing visible. I drew another large box and set it to constant power and slow speed and ran it. And guess what? The beam was solid with no flickering at all. Go figure! I ran more tests. Every test I ran it looked great. As much as that should make me happy, it kind of concerns me that maybe there is an intermittent problem which will be harder to diagnose and get fixed. But at this point I need to move forward and get back to the original issue that led me to finding the flickering laser.
I will keep an eye on the laser and if I have any further info to add I will. Also if anyone has any suggestions or tests I can do to determine if the PS or laser tube is bad or faulty I would welcome them.
I think I am going to go post my other issue, regarding the dots/serrated/jagged edges, in my post where we previously worked through the problem and thought we had it figured out.
The way a tube functions, is the dc voltage causes it to conduct, it will draw as much current as the lps will allow. As you increase power you are actually allowing an increase in current.
I doubt the tube is failing to conduct all of a sudden, doesn’t make sense, that leaves the lps, which is where I’d put my money… if it were mine, I’d change out the lps.
I’m not all knowledgeable about tubes, but I’ve never seen a tube do this… lps, yes…
Yeah I know very little about either but the fact that it was flickering one day and not at all since (that I have seen) makes me lean toward the LPS. I know PS’s can start acting wonky before going out. You would think if the tube is having trouble one day, it would have trouble the following day as well.
It makes me wonder if it might be a heat related issue? Maybe the PS will only start acting up at a certain temp. IDK
Since the seller is MIA, I may need to purchase a new PS myself. Although I do have the contact info for his manufacturer. Wonder if they would deal with me directly?
I’ve had mine a few years and I run it all year… it gets to about 105F before it’s too uncomfortable for me to operate it… I’ve lost a tube… lps is still going.
Doubt it’s heat related and if it is, it broken or in the process thereof.
