I’m using a laser path calibration kit from Cloudray Cloudray Laser Path Calibrating Kit For E Series Laser Head. And Mirror 1 (first mirror after laser) is dead center, Mirror 2 I find also to be in center both in the near and far position (2a and b) but at the last mirror I can’t find a good position.
If I hit center of the circle in the middle far right position (3e) then the laser beam is to high in the middle left position (3b)
For me that means that the laser beam is to high, and ideally the whole mirror 3 system and lens should be raised - or the laser source should be lowered. But I guess its not important that it hits dead center in the vertical direction - that can be adjusted in the mirror.
If I make the beam hit a bit above the center I can make it hit (roughly) the same position in both the middle left (3b) and right (3e) position. And now - given that the beam seems to hit mirror 2 in the center both near and far - the whole system should be aligned.
But as you can see from my attachment it both changes in the horizontal and vertical position when the laser is moved. Is the whole system skewed? Or can someone point me in the right direction?
Or is a cheap china machine at 1300x900mm simply too big that I can expect a good calibration in the whole area?
Hi Lasse, As you yourself mention it is a reasonably large machine and the results you have are in my opinion “good enough”. What about the nozzle itself ?, do you hit the spot? It is likely that your frame is a little crooked, and you could experiment until a better result, by compensating with intermediate layers, small thin metal strips. But, what does your current outcome look like? Is it fine, fair or bad? Ps. I also use Cloudray’s calibration tool and am very happy with those.
So here is an opinion from a laser service engineer. Personally do not like the cross hair jig and here’s why. I serviced lasers for 25 years and never needed one with one exception…when aligning the laser to the first mirror. I want the laser to hit dead center on mirror one.
Now the rest of the mirrors I burn on usually doubled masking tape and use a short pulse. This is for mirrors two and three.
The reason is I want to see the exact amount of beam walk on a near and far burn. I don’t need a jig splitting the beam and making the burn diffused and obscuring the walk. Even minor walk between mirrors one and two will exponentially grow when check mirror three at x and y max distance…front right of the laser and rear right. This is where any and I mean any misalignment will be exaggerated.
So I do a near burn and a specific mirror and then a far burn…whatever the walk is when I am at the far position I move the mirror aiming the beam at the tape halfway between where the far burn is and the near burn is. Do not invert this method…must be near then far then adjust mirror so burn is between the two burns, repeat until no walk.
I have aligned many articulating arms that have 6 or more mirrors and can get them all spot on….been doing it for over twenty five years.
Don’t worry about whether you are hitting the center of the mirror once you have it centered on mirror one. The point of a near far burn is not to hit center it is only and I say only to make sure the beam travels on a flats plane through all the mirrors and is not walking. If it’s not dead nuts center no big deal. If it’s off too much you either need to move your tube…or move a mirror mount. But changing the angle of a mirror solves nothing for hitting center ever…so ditch the jig until you need to check say if it’s hitting mirror three close enough.
I think mirror one is still not aligned and I can see it in your burns but your jig is diffusing it.
So…when you do not get any beam walk on mirror three when you place a burn marker over it…and this it all four corners of x and y extremes…your mirrors are aligned period. Toss the jig on…if it’s not on center you can adjust the whole mirror three mount…if it’s off for to aft…up down well that’s not possible on this mirror…but real close is usually fine.
Last…there can always may be mechanical deviation such as a slightly warped or tweaked gantry or a rail. These are not 20K Epilog lasers so…mechanical quality is well…good enough but nor perfect. I have had bad rails before that were very slightly tweaked. These will be apparent when the beam walk is wonky and not consistent between two extremes of an axis. If you check at the midpoint as well and you look at the walk it won’t be linear. If so thats another issue and only if it creates an issue…it may not.
Now adjusting mirror three to be on plane to the lens is a whole other art form
John: I will measure the diameter of the beam when I get back from my day job
I have also wondered if it should actually be that big in the far corner.
Scott: Why is it so important for the laser to hit dead center of Mirror 1 (closest to the laser source)?
I have also tried using just doubled masking tape - and maybe will try that method again - I understand that getting it to hit dead center is less important than being completely parallel with the axis. And the jig can get me focused a bit to much of the center. And yes - a big problem with my laser as I see it is the lack of adjustment at mirror 3. When I get to the final adjustment - only to find out that I need the laser beem to be far from the center I have to make the adjustment at the laser source - and start from scratch…
Hi Bernd
The outcome is fair - I think I dont know how much better it will be if I get it to hit spot on.
It cuts 12mm plywood (pine) fine at 8mm/s 65% power. (I have my max set at 73% to avoid damaging the tube) I think I have seen others go quite a lot faster than this…
Hi Lasse,
First something about the beam diameter of your laser tube For a good quality tube, it is indicated by 5 mm for a 130 Watt tube, at the output at the last mirror from the tube. On his way through 3 mirrors and a distance of approx. 2.25 m (your laser machine) the laser beam will expand its diameter, you could calculate it with a mRad factor … Long story short, the laser beam expands. The mirrors and lens in our laser machines therefore have different diameters, the more powerful a laser the larger the mirrors and lens. The purpose of fine-tuning a laser beam is to get as much energy as possible “through” the center of the mirrors and of course the lens. Which system is used to achieve this is subordinate as long as the goal is achieved. American Photonics, for example, does the opposite, they send a pilot laser from the nozzle side towards the CO2 tube, - fine, if that works. Some use only a few layers of tape others the little tools we use, just it works!
When my laser machine arrived, I dismantled the laser tube itself so it would not break on its way into my workshop, down into the basement. When installing my laser, it was important to me that it is completely straight and stable. As @shughey emphasizes, mirror number 1 is very important. I had to adjust the angle of the tube itself, horizontally and vertically to get an acceptable centering on No. 1 and the other mirrors. The biggest challenge, in my opinion, is that the machine itself is built of enormously thin metal tin and responds sensitively to all movement of the laser head. The machine bends and twists a lot. On top of that comes the actual mounting accuracy, do you think the difference in the actual frame level is in the submillimeter range?
It is incomprehensible to me that it is still possible to get amazing results out of the machines, It should not be possible.
Therefore, I also asked if you are otherwise reasonably satisfied. If you have done your best to get the machine balanced and get a thin (0.1-0.2mm) and straight laser beam out of the nozzle itself, then you (we) can not expect more for the amount of money the machines cost.
Regarding your settings for cutting wood, I am also relatively conservative in terms of my settings. I have the luxury that I make some money with my lasers but I do not have to make a living from my lasers. So no stress on the machine or me.
12 mm Plywood, it sounds fine if the cut is even nice. It roughly fits my half as big machine, I get acceptable results with up to 6mm standard construction site plywood.
The ultimate goal of the alignment is to get the beam to enter the focusing lens in the center and perpendicular to the surface of the lens. The lens is a convex lens and if you do not have the beam entering it centered and perpendicular to its surface then you can have issues with beam quality and profile. One can see this with a magnifying glass and the sun…if you have the magnifying glass perpendicular to the sun you get a nice round spot and if focused correctly you can burn with it. But tilt the lens off axis and that round spot distorts…so same thing with your laser.
You try and get the beam dead on center at mirror one because from there we can check the rest of the mirrors and see, after fully aligned, if we follow fairly close to center on the rest. Ideally we hit every mirror dean center…reality is we usually get close.
Unlike a convex lens which has to be hit on center a mirror does not cause any problems if the beam is off a bit. It’s a flat surface so it won’t cause any beam distortion. Rather it’s really about ultimately staying on center through the entire beam path so that when we get to mirror three and it reflects to the lens we are still close to center.
If you do not start on center any error tends to grow over distance and then when we get to mirror three you will be far enough off center you can’t get a good beam off the lens.
Our lasers do not have a complex final delivery setup. A simple convex lens is very basic. Therefore these rather simple lasers and the middling quality mechanics will suffice. If these were surgical lasers with a complex final delivery assembly any slight misaligned error would cause noticeable issues.
I have used these lasers for ten years, for their designed purpose and market they are very good. They are robust…just not a finely tuned 30k dollar laser nor do they need to be.
I would suggest that when you do your final test of the beam quality on say wood. Defocus your beam about 3-4 inches. This will give you a beam diameter close to the beam size prior to it entering the lens. Then move all around the gantry and do burns and note the beam shape. If it doesn’t change much you are fine. If you are off too much you will get a round burn close to the left side of the gantry and then wonky D shaped burns on the far right in spots. This due to the beam not entering the lens correctly at that position. You can slightly tweak mirror three at those wonky burns a tad to try and eliminate that. But you cant tweak it much or you throw it out somewhere else. As long as your beam is pretty darn good all around your good. When it’s focused properly the beam is so small and power density so high it won’t matter.
BTW…I have 5 lasers…three of which are OMTECH Co2 lasers…the other two are diodes. I DO MAKE MONEY on mine…they are my business. I would rather have 4 OMTECH lasers than one Trotec etc. for the same coin. I can fix them for cheap…not so with Trotec or the others…with those you are stuck buying parts from them and or using their field service guys…remember I am a retired laser field engineer…I know how it goes. We make money on service!!
There is one last check I forgot…and I editing this as I realized theres an easier way.
So there are two goals. To insure the beam hits the focusing lens on center and not a weird angle.
Second to make sure the beam hits the work surface perpendicular to that surface.
I think first I would remove the lens and nozzle assembly and let the tube out as much as possible…usually the tube can move up and down a bit.
I would raise Z bed until I was close enough to get a good small square in there and make sure the tube is perpendicular to the bed…just do it around center or so of the Z bed. You can adjust the whole tube and mirror assembly with the screws on the side of the big black block that holds the mirror…this will tilt the tube for and aft. If it is off front to back you need to remove the block and get to the back screws.
Very close is fine…but i had one laser that was off.
Now as long as that is close enough for government work you need to align mirror 3 to the lens.
I do this with the lens/nozzle out. I run Z to within an inch of the tube…do burn…lower Z about 5 inches or more. DO a burn…adjust mirror 3 so next burn is halfway between far and near burn. always move at the far burn. Repeat until no walk.
Now put a piece of tape over the tube and do a quick burn shot…beam should be close to center and since we squared the tube to the bed and did a near/far the beam should hit the lens very close to perpendicular.
As stated earlier if you beam isn’t centered but is off either for or aft you can loosen the screws on the side of the block and slide the block a bit…trying not to tilt it at the same time. Again only if you are way off but even then to be way off something prior to mirror 3 is out.
Now put your lens assembly back in. Defocus by making it about 4 inches away, from the bed with a piece of wood to burn on, or until your beam is about same size as it is prior to the lens.
Move your x and y to both extremes and do burns and check beam profile. Should have a beam that looks the same or close to it when x and Y are at extremes. If there is some wonky I usually just tweak the 3rd mirror a tad as it usually means the beam is not perpendicular to the lens at that position. Its a tweak and check…small movements. Usually if it is off the beam will be D shaped. I find that mirror moves in relation to the straight side of the D shape…I think it is away from the straight edge of the burn…but you will easily see.
Modify this as you see fit…this is just my way taken from how we did it in the field on different equipment. Your experience may differ.
Usually there is some compromise on the final alignment. We do not have precision jigs to test mirror 3 to the lens…so there is some tweak and check out of the lens to work surface. We are not working with a precision made machine its made close enough so we align close enough and tweak for effect if needed…
One would think that Russ keeps an eye on us The first part of his new video covers part of our little interesting discussion. I’m excited about what he’s coming up with again.
The first part of his new video covers part of our little interesting discussion. I’m excited about what he’s coming up with again.