Print and Cut alignment accuracy - red dot or beam combiner

I need to add a red dot or beam combiner to my laser so that I can set up 100% accuracy (or as close as possible) for the print and cut feature in Lightburn. Ideally I would love a set up the same as the Trotec Vision Cam.

I have a sewing embroidery machine that has a head mounted camera and the principle is the same as the Lightburn method. I can see that Lightburn has a feature for a head mounted camera that is not turned on yet. I hope that there is something not too far away for release.

That aside, can anyone please explain how this system works in the video link below? The red laser is mounted between the first and second mirror. I am wondering whether the red laser that emits from the focus lens would infact be accurate and on the same path as the actual laser beam? Obviously, this system is only for set up process with the print and cut feature in Lightburn or the laser would be toast if you forgot to remove it. It is at the 5:50 mark in the linked video.

Any ideas about this or the best way to get as accurate as possible print and cut please?

There are several different ways of adding a red dot that can be used for alignment.

  1. CO2 laser tube with integrated red dot - this is likely to be the most consistent and least fussy method of getting a red dot as the red dot is integrated into the function of the tube itself. Obviously this is costly but a consideration if you ever replace your tube

  2. beam combiner - this allows for the introduction of the red dot immediately before M1. The advantage of this system is that the red dot can be in alignment with the cutting laser for any focal range. However, this can be extremely fussy to set up and equally easy to get misaligned if anything gets bumped at the combiner or mirrors. This approach also very much depends on mirror alignment being dead-on as the red laser and cutting laser lines can easily diverge. When it works the results are seamless and accurate.
    Will look something like this:

  3. head mounted red-dot laser - this laser is mounted directly against the laser head and is aimed at an angle to the direction of the cutting laser. As a result, the red dot and the cutting dot will only converge at a single distance from the material, ideally at the focus distance. This means that the red dot cannot be used for alignment if you are dofocused. In practice, this isn’t usually an issue since you can align first, then defocus.
    Will look something like this:

  4. the red dot used in the video. I wasn’t familiar with this style. While I can see this working to a reasonable degree, unless there are specific measures to guarantee registration to a very specific orientation I don’t see how this could be repeatable and accurate. Again, I’m not familiar with this specific system so there may have been special provisions made for it. I assume this red laser is aligned to enter M3 and exit the center of the lens tube. If you assume that the cutting laser is also doing the same thing you can reasonably assume that the two lasers are roughly colinear. As you suspect, you’d have to be extremely careful to remove the red dot before firing the laser.

While still considered to be in Beta, this feature works today. Note that camera and red dot alignment is unrelated, however.

Print and Cut only relies on the accurate position of the laser head which is most easily accomplished through a red dot. You could theoretically keep pulsing your laser near the target mark until you achieved perfect registration, assuming you have material to spare around the mark.

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I am a big fan of the head mounted red dot laser… I added one to my big C02 laser and just point it at the exact spot when my laser is in focus. It was cheap and easy to install. I had plans to add a combiner and all that but this worked well enough for my workflow.

3.1 If there is enough space on the nozzle head, 2 of the holders you show but with a single line filter in front of the red point laser diodes will give very nice results. It allows for a crosshair after the lasers are aligned parallel to X and Y. The advantage is that it is very easy to adjust and any inaccuracy can easily be seen, that it works independently of focusing and is cheap.

Thank you. I have actually made and wired up a crosshair mount for my laser head but find the lasers move on their vertical axis -thinking I may need to glue them in place as well as the focusing ring on the ends of the red laser tubes. When aligned on parallel to the X and Y, do you mean to the gantry or that the red laser lines are square to each other? Thanks

Thank you. I am thinking the red dot is probably the easiest to install. Was considering upgrading to a newer laser just so I could get an accurate red dot!!

Thanks for your indepth reply. Lots of options to consider and good to know that the head mounted camera in beta form is working. This similar system works brilliantly on my embroidery machine whereby it scans the workbed for and recognises the crosshair alignment marker. It compensates for any misalignment of the work piece and adjusts accordingly. It would be brilliant if the same set up was readily included on lasers other than the Trotec (which is way to many $$$$ for me) :slight_smile:

Perhaps something to upvote or add in the feature request page. I’ve seen similar registration mark scanning solutions like you’re describing on vinyl cutting machines. While convenient when they work I find the process at times fussy and the results not always great. Print and cut is slower but extremely accurate and flexible.

Yes, exactly 90 degrees to each other and I used my gantry for this adjustment because it is very precise.
I have not experienced the diode moving in the small ring held by the pinol screw.
To make the beam even finer, a kind of pole filter or a thin disc with a 0.1mm hole in the center can be used, placed in front of the diode, that’s what I read here in another post.

I usually don’t get involved with the led pointer discussion, but I though a different view might not hurt…

My China Blue 5030 came with a lens tube mounted led pointer (@berainlb last photo in post 2). It never was worth the trouble, for me. I had to adjust it depending on the lens I was using… for acrylic it was easy to set to the exact point and worked relatively well. It failed on about everything else to be worth the extra time and effort.

A beam combiner should work… I thought, but after watching some of Russ Sadler videos on this and similar alignment issue it was clear there wasn’t a good solution.

The simple facts are you have to align the pointer beam exactly with the lasers beam, which is pretty much impossible.

When my tube went south, I asked Russ about replacing it with an internal beam combiner in a factory tube, like he mentions in one of his videos…

He response was not very supportive and stated since then he’s run into too many of these that wasn’t working properly and no way to change them… he suggested I not spend the extra money.

So I just replaced it with a good 40W tube…

I align my work to the machine or use jigs to hold parts in place.

It depends on what you do and what kind of accuracy you need… Lots of people use them, I’ve managed without them for quite a while.

Good luck

:smile_cat:

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Red dot beam combiners are accurate in themselves. However, there is always some power loss on any optic. On these 45 deg combiner plates, they can lose a lot to reflection if they’re wonky. Wonky comes from poor mfg or poor mounting.

Mounting stress causes the problem. Ideally, they should be glued in. The ones with nylon compression screws will cause major reflections if they’re tightened down much at all.

Also, you MUST have a black anodized aluminum beam stop in the reflected path. Otherwise you can burn holes in clothing, set something on fire across the room, etc.

100% Jigs are my best friend. I save all my big flat pieces of cardboard. Tape cardboard down and just cut out my shape. Pop my part into the hole. Done, no fiddling around with trying to align my parts. This has been my go-to method. I believe you cannot get a more absolute position than that.

Jigs are fantastic for their own purpose but don’t address many of the use cases where print and cut shines.

I reference my materials for print and cut on the machine the same way… I do have a large cutting area, so I have room for a jig to take up some space. Definitely jigs do not suit every situation that is for sure. My workflow may be much different than others, but for many of these “how do I align so and so tile or coaster for burning” etc questions are easily solved with some form of jig or reference end-stop.

I always use jigs where possible too and agree that they are quick and easy to use with good alignment.

In this instance I need to use the print and cut method as I outsource UV printing on acrylic and then cut the shapes when returned. The cutting tolerance is tight and the prints requiring exact placement otherwise the whole sheet is ruined. If I could UV print myself it would probably be easier as I would have complete control over the job. Maybe oneday I can afford a 30k printer!!

Thank you! I have seen that other post you mentioned so will look into that as well :slight_smile:

Thanks for the info. Lots to thinks about and weigh up. Am thinking I will just stick with the red dot/crosshair and jigs. I suppose I don’t really need to upgrade my laser for now so that can only be a win :slight_smile:

Learn to use what you have… as you get more experience doing this, you’ll figure out what is best for you…

:smile_cat:

I know right ?! Ive been looking into a UV printer for some time. I have so many things I can do with one. As a small manufacturer I am always looking into the next tool… Eventually the price will come down or even become accessible to the DIY market and I will get my printer.

I have a CO2 and a diode laser, both with a simple red dot pointer mounted on the head vertically, so parallel to the laser beam. Using the red dot offset in Lightburn, i can use the red dot to frame jobs easily and the Print and Cut feature works perfectly. When the job starts, the laser moves to the offset position before starting the job. No issues with head height before or after framing or trying to align the red dot and the laser dot.