When everything is aligned properly, I would take a reference alignment shot at your first external mirror, and at the cutting head.  Then when you have cutting issues, check the alignment on that first mirror again and compare with original shot.  If it moved, then beam coming out of resonator is moving.  If it is still good, check alignment at the head; if that one moved, then external optics are the problem.
However, depending on the machine configuration you have, the distance between resonator output and first mirror may be very short; so even if the beam coming out of resonator did shift a bit, you may not be able to tell.  That's were mode shots would be more interesting.  If internal optics shifted, your mode would change, and you would see it on the mode shot.
If you're not sure how to take a mode shot, you can also check parameter 15204 (calibration coef).  If you see a big jump in it's value after the alignment shifts, it could indicate something shifted internally.  of course, you need to shut down, then restart the resonator in order for the system to go through its calibration and recalculate that parameter.

What are the Amada techs doing to get the machine back up and running?  Are they adjusting the mode, or are they only aligning the external optics?

I have personally never experienced a beam shifting due to internal optics on Fanuc resonators.  But in the case of short beam path, the Fanuc resonator can have 2 small mirrors inside the resonator (they reflect the beam to make the optical path longer), but they are not part of the internal optics (although they are inside the resonator).  I have seen beam shifting due to those 2 little optics.  If your machine has those 2 optics, you could try to cut the ties holding the water cooling lines attached to the frame (leave the cooling lines hanging free); sometimes, chiller start/stop and vibration from water circulation can make those mirror vibrate a bit and knock off alignment (I have seen this once).  Make sure the spring loaded screws are completely screwed in (so spring is compressed to the max).  Also make sure the 3 big bolts holding the plate where those 2 mirrors are mounted are tight.  I've had them a bit loose once and beam would shift just enough to cause problems.

Also make sure your machine foundation is good.  Do you have heavy punch presses close by the machine?  If so, make sure you have cut an isolation around the machine foundation, and filled up with insulation material (rubber or Teflon).
Could there be a cooling issues which could overheat your optics and shift them?  You could use an infrared temp probe and check your mirror blocks right after cutting at full power for a while.  Temperature should be close to chiller temp setting.
Is the resonator properly attached to the machine frame or floor?
Are all the mirror blocks attached properly?

I agree with you, seems more likely that this is an external optics issue.  I think the best is to take alignment reference shots are each mirror block.  Then compare with same shots taken once the beam shifts.
If you still can't find out which mirror is the problem, you could try to push and shake each mirror block one at a time, trying to make them vibrate a bit; then take another shot at the head.  It should not shift; if it does, the mirror you just pushed is the problem.  Do the same for each mirror block.

The story about replacing the blower seems weird.  If the blower was bad, it would project oil or debris internally, on all your optics.  So if that was their explanation, I hope they also replaced all the internal optics.  Taking a cold and hot mode would have also shown big signs of degradation if that was the case.  Did they take a cold and hot mode?
Also, your calibration coef (param 15204) would have been going up; and you should have gotten power down alarms.  Either they are not telling you everything, or the service engineer just did it so he did something...



 

The Amada service tech has replaced the blower with the Fanuc service tech assisting him. We have run the machine for a week, as they had recommended and are experiencing the same problem. We cannot keep the nozzle alignment in check. The service techs (Amada and Fanuc)returned and replaced the internal optics and re-aligned the machine. The theory was that after the blower replacement that a weeks worth of running would insure that any debris or contaments would be purged, giving the new optics greater longevity.
Once again they recommended running the mac hine for another week to see if things would settle in, but they have not. We are still experiencing the same problems. The answer now is that we should perform the full seven step auto aging process at least three times a week, rather than once a week. Typically on a Monday after a weekend shut down.

Hi Laser west,

If you have removed the external mirrors was there sufficient heat thermal compound behind it?

I have found the Amada mirror holders to be under engineered with small flimsy shim holding the mirror in place.

If you don't have the thermal compound or not enough this may be your problem.

The worst thing is you remove an external optic you need to do an external alignment from that optic (bad design)

 

That whole blower replacement is a joke.  Why would a bad blower shift the beam?  Oh well, I guess if it's warranty, not too big of a deal.  Hopefully they installed the new style blower.
Same joke for the auto-aging, full 7 steps is only required when the system has been open to atmosphere (like when changing tubes, optics).  Worst case when not aging enough is that your power calibration (param 15204) will go up.  But this will not cause your beam to shift.
If the mirrors seem that flimsy, I'd look into that.  Take a shot at head, push first mirror by hand.  Take another shot and compare.  Do same for all optics starting from resonator towards cutting head.
Also make sure it's not the cutting head moving.  You could check that with a dial indicator on the head; push it and make sure dial comes back to same spot.  Check it in 2 directions (X, Y).
 

Foostrap is a man after my own heart. I agree with about 90% of what he said. Except for this.

As the internal mirrors get dirty, the source of the beam shifts. More specifically, a Fanuc laser with a Coefficient of 980 will not have the same external alignment as when it gets to 1100.

Conversely, if the external alignment is preformed before the laser is finished aging (after turbo replacement or internal cleaning), the alignment will change over the next few days.

Was this machine purchased new or used?

I would also like to say this. Amada / Fanuc laser are very stable. You did not make a mistake in buying it. The cause of the problem will be discovered and you will have a great machine that will make tons of money for you.

With out seeing the machine, its difficult to say exactly what the problem is.

First off all lasers float. The alignment shifts around from morning to evening from summer to winter.  Its the nature of steel and changing temperature. The question is how much is too much.

Foostrap has some great ideas.

First step is to get a stable laser power coefficient. (15204). It should be with in 20 points from one day to the next.

Second, The cutting head is the second most common cause for alignment issues. If the head has been crashed, it could be loose and have wiggle around changing your nozzle center. That is why I asked if the machine was used. It may have a history.

Last, and least likely, is a problem with an external mirror. The mirror in the laser cabinet that is not a "internal mirror" can pivot on two of the three adjustments screws. That is where i have heard of problems in the past but never experienced it myself.

You said Amada FO3015. Is it an NT? NT has a different head design and could cause other issues.

Where are you located? I may be able to tell who you service reps are and whether or on they know what they are doing.
 

The Laser service representatives in you area are, in my opinion, some of Amada's and Fanuc's best. The people that I have talked to about your machine care deeply about you situation and are making their best efforts to rectify the situation.

From what I understand, there was indeed an issue with original turbo blower. Its good that it has been replaced and eliminated as a possible source of contamination.

As I said in my previous post, the first step in solving this problem is to get the Fanuc part of the laser stable, good beam quality, stable power. It sounds like you are close to being there.

I will forward Foostraps ideas to the Amada laser mechanic. I have been assured that all the items outlined have been checked but, it doesn't hurt to check them again.

Obviously, you posted here looking for help. In this case, I don't think there is an easy solution that can be posted on this forum. What we can do is keep passing around ideas, testing them out, hopefully share some information that will increase the greater understanding and yield a favorable outcome.
 

Laserninja, that's interesting.  I have never personally experienced beam shifting due to internal optics getting dirty.
In theory you would think the direction of the beam coming out would only depend on internal optics alignment.  How much power actually gets out should not affect beam alignment.  At least, that's what I'm thinking and that's what I've experienced so far.
Not that I recommend it, but I've seen plenty of customers not changing optics for over 8000 hours, running for more than 1 year pretty much 24/7; calibration coefficient did indeed increase from for example 960 to 1150 (or sometimes even more).  But optical path alignment was still good.
Another example, more than once, I have replaced all tubes and did not have to re-tune and re-align anything; internals or externals.  I let the customer run a couple of days, to make sure all contamination gets burnt onto the old optics.  Then replace them.  Same thing there, no need to re-align until optics actually got replaced.
But I guess if you mention this is possible, you must have experienced it.  Anybody else experienced the same?

I agree with you regarding the Fanuc resonator; it is indeed very stable and very forgiving when the maintenance is not done on time.  There is a good reason why so many laser manufacturers besides Amada use the Fanuc resonator.

Other thought; I don't think the resonator power was mentioned.  If it is a 5 or 6kW, those require nitrogen in optical path and can give very unstable beam if nitrogen purity or flow is not good enough.  If using a nitrogen generator, purity should be at least 98%.
The beam can also react to acid fumes, paint or chemicals (welding crack-check products).
What are you using for your cooling water additive?  Some antifreeze products will also affect the beam.  They'll work fine when you have no water leak.  But it can take just a tiny little water leak (you may not even see it) to get those products into your optical path and affect the beam.  If this may be a possibility, switching to regular de-mineralized water for a while would be a good test.

It'd be interesting to know what the problem is.  Please let us know once the problem is fixed.

Not sure why that got posted twice. Sorry

Fixing lasers is not something I talk about very much, or put down in to words. Most people seem to have a problem with their eyes glassing over when I get started. So, I don't even bother. Forgive me if my thoughts are not cohesive.

I'm not saying I'm right. I just would like to explain the logic. If nothing else than share my opinions and observations with those who can argue with me.

My understanding of a pre-focused mode is this. I imagine the output coupler with detritus on the internal surface. This material absorbs the laser power to a small extent and causes the optic to heat up more than a clean one. I envision the optic expanding, as most things do when heated, and altering the curvature of the optic, thus causing, the beam shape to change. This may or may not be the case. I have cleaned mirrors and the problem has gotten better.

In my previous post, I stated matter of fact that the external beam changes position as the internal mirrors get dirty. Foostraps comments have made me think about my comments and maybe I'm wrong. But isn't that one purpose of this media, to get people to question things the assume to be true?

But, let's say that the output coupler expands with heat and changes shape. More dirt on the optic more heat absorbed, more distortion. Is it then possible that a distorted surface of an output coupler be considered "out of alignment" from its ideal position? And, taking it a step further, if the internal beam path changes, isn't it safe to assume all down stream optics are effected as well? Can I then apply the logic to all eight internal mirrors in a Fanuc 4kw laser (the one in question).

How about this? What if the contamination is not evenly distributed over the surface of the optic. What if more glass dust or oil is on one side than the other? Would that side absorb more energy than the cleaner side? If there was a temperature gradient across the body of the optic, wouldn't that cause some funky distortion? And so on and so forth.

I have gone in to work on machines for a reason other than cutting issues. Because I'm a nice guy, I check the external beam alignment. Sometimes it's not perfect, not how I left it. As with most qualified laser mechanics, I can shoot four corners on a flying optic machine and tell you exactly which mirror is off. From my experience, either the first adjustable bend mirror after the output coupler is a P.O.S. or the beam has shifted inside the laser. That's just what I have seen.


 

I agree with you regarding pre-focused beam or cooling issue.  That's why in my first post, I asked if the Amada tech took a cold and hot mode before changing the blower.  If there was something wrong with cold/hot mode, then I agree that something was wrong with the resonator.  But if they changed the blower simply because the nozzle alignment was shifting, it makes no sense.

A bad cold/hot mode would have also caused lots of cutting issues (especially at full power), even if the alignment was still good and did not shift.

If you have doubts about the beam shifting because your optics are getting dirty and heating up; you could do this test:
Take an alignment shot at the head with the resonator cold (after letting the machine sit with no cutting for 10min).  Then perform full power internal discharge for 10min, and take another shot right after that.  You might notice a small change in beam diameter, but the alignment should not shift.
If it does, you have a resonator problem.
If it did not shift, the problem is most likely on the machine side.
 

This machine was purchased used and is a 4000 watt machine. The machine is a FO3015NT and at first was cutting like a dream and has just recently developed this problem. There were issues with the previous owners and or operators, and theses issues have been researched and considered in trying to correct this current problem. Amada has recruted the help of the service teams from the Washington area to have some new eyes look into the problem. So far all that has changed is we are having to use bigger nozzles in order to consistantly cut from one end of the table to the other and combat with the beam shift. this is not the permenant fix but offers us a little more consistancy while trying to maitain production. Thank you for all of your suggestions, for this is the power of this forum, collectively sharing the vast experience that our members hold. Hopefully in turn we all walk away with a greater knowledge of our indusry. I will keep you informed as changes develop.

I've been thinking about this one for a while and haven't gotten much further. I have heard that this laser, AF4000E, is now stable. Hot and cold mode look good. Laser power is awesome. Coefficient around 980 and stable (pucked out of the cabinet). Amada Gemini uses one adoptive optic above the cutting head, it has been replaced recently, withing the last few months. By the way, this laser is a "spring chicken" 6000 hours on the laser with new turbo (not re-built)and new Fanuc internal optics.

The fore mentioned Amada Service Representative was there last Wednesday, Thursday and Friday. He came in and checked the four corners right away. Off "maybe 1mm". The machine cut very well all day Wednesday and Thursday. Friday morning, it started acting up on the end of the table furthest from the control. Once the sheet was finished, the program was reversed so it started at the "bad" end of the table and then came toward the control. Still bad at the bad end then got better.  One more interesting note. holes were using one set of cut conditions while the perimeter used another. The holes were having the problems and not the outside.  I've attached some photos (maybe).

It looks to me like a drop in gas flow, but I have been assured that is not the case. The dross is not in the same location every time. Sometimes 12 o'clock 9, 6, 7:45. some times all way around the hole. Keep in mind the perimeter of the part, still cuts well.

For the sake of argument, right after the laser started to cut the holes poorly, the laser was shut off and then restarted to see if the calibration was different. It went from 984 down to 980. And no change in the external alignment was observed.  

• http://files.engineering.com/getfile.aspx?folder=ba9a590f-3712-4685-bfe2-2f

Another attempt at picture upload.

• http://files.engineering.com/getfile.aspx?folder=07d49818-873b-465c-b2b3-c4

Laserwest, Laserninja, thanks for the update and additional info.

First question is, how was the alignment once it started cutting bad in the back end of the table?  Did it move compared to the shots when the machine was cutting good?

The burr on the picture could be caused by:
- Not enough gas pressure
- Focal point too high
- Too much power for inside profiles
- Nozzle too small
- Table slats completely worn down

Is the sensing system of the machine stable?  Is the piercing OK?
Sometimes, when the piercing leaves too much scrap on top of the material, the sensing system to follow the material height might bounce up a little.  This would affect gas pressure on the material surface, and also focal point, which could result in the inconsistent burr you see.

Other difference there could be between outside cut (which looks like straight cuts) and inside holes would be the machine acceleration.  Could the nozzle (or head) shift while cutting a small circle at high speed?

Are they cutting any mild steel with oxygen, which would require a much smaller nozzle?
This would be a better test to check the nozzle alignment and beam alignment stability.  If you can cut consistently with a 1mm nozzle, alignment is good and stable.