Things just don’t look placed right in the picture. I guess I can’t say without a printer to look at.
oh - well of course the components are only approximately positioned - but it doesn’t matter, it’s enough to show that right angle triangle math is not sufficient for the problem
and you’re interpreting the perspective view wrong - heres the same model side on:
No it is not. Redesign your model so the following constraints are true, which I’m fairly certain they are on the form1+. The large mirror is exactly 45 degrees different from the tray. The center of the large mirror is directly below the center of the tray. The small mirror is exactly 90 degrees different from the large mirror. The center of the small mirror is at exactly the same height as the center of the large mirror. The center of the x galvo is directly above the center of the small mirror. The center of the y galvo is at exactly the same height as the center of the x galvo. The center of the y galvo is directly on the path of the laser. The length of the path from the laser to each consecutive center totals 300mm.
If my assertion that the above constraints are true is correct, I’m confident your new model meeting them will consistently yield a value less than 312.75mm for any path to any position in the build area. I did my rough calculation based on all the assumptions listed above, but like I said I am pretty confident that is how the form1+ is laid out.
If you have all the constraints I listed met and both galvos are at 45 degree angles, the path from the laser should hit the centers of everything.
@RocusHalbasch I did start out making those changes to the model - but then SW barfed, I just can’t get it to handle lots of chained mates, and I have a lot to do before my 50cm focal length UV lens arrives tomorrow.
After my beam profile images from post 226 above I’m starting to feel more enthused about a solution …
1 Like
@KevinHolmes & @JoshK Good work. Thank you for contributing. I think I understand this more.
@RocusHalbasch I know from talking directly to people at FL that the original problem was because of some bogus epoxy the vendor was using to bond the laser die to the case. The epoxy was boiling off and condensing on inside of the laser’s lens. I was shocked that they were just buying lasers from China with out doing accelerated age testing. I not know about optics but I do know about semiconductors. The more we talked the more I felt like they were shining me about doing this testing now but I am sure they are not going to ever ship faulty lasers again. I think they have someone acting as an in between doing testing and etc.
2 Likes
@EvanFoss thanks for the added insight on the form1 lasers, I really like knowing what happened. As for them not ever shiping faulty lasers again. I think they might currently be doing just that. The problem here may not be degradation over time. But if the spot profile is bad enough to case some of the problems we are seeing, I’d call the lasers faulty.
1 Like
Hah. Actually, that is also due to the angle of incidence changing depending on the spot at which the beam hits the main mirror. I’ll try and illustrate it…
Awesome work! But i think that’s perfectly fine for the distances involved.
I doubt the beam path length changes by more than a cm or so.
1 Like
Agreed - the problem is it’s impact on an aperture/iris solution to laser flare. I’m working on an extra-mirror+extra-lens+aperture approach now though …
1 Like
Re: geometry…
You can greatly simplify the problem by treating the galvo assembly as a point source.
The changes in beam length contributed by the galvos are negligible.
You’re then left with something like this:
Of course, without knowing the angle of the main mirror, the numbers are just one big guess 
This is what i’ve meant by the angle of incidence changing the flare (shape and size):
Edit: obviously, the “shadows” or rather projections should be cast at the point where the beam crosses the print surface - but that’s irrelevant for the purposes of the illustration.
Right…I pretty much said the same thing without the fancy diagrams 
“Fancy”, huh? 
I’m pretty sure the printer achieves ideal… With the mirror at 45°, and the distance from it’s center to the other centers being equal.
Depends on space constraints and internal component arrangement.
Sometimes product design and compactness take precedence over ideal component placement.
Should be easy to figure out even without measuring the angle directly - assuming the mirror-to-print coverage is 100%, measuring the longer side of the mirror should be enough.
I have a good digital inclinometer at home I’ll do some measurements tonight, get the main mirror angle and size, distance to small mirror etc.
@RocusHalbasch This is not a failure of the laser but a failure of formlabs to understand how to use tolerances in respect to lasers. It took decades from the first laser print to the first home desktop one. That was years of working out how to go from having optics that look like formlabs stuff with fasteners and custom machined metal blocks to having an epoxy fiberglass box that had all the fittings for the optics just built in. Your desktop laser printer has resolution on a par with the form 1+ and it uses crappy lasers too I bet. The difference is that the people who print on paper did the math to work out what all but the worst say 5% of lasers would be like and designed the device to accommodate that. Knowing how to do that math is what we studied in engineering school. Just doing what they did and building a device that works as a prototype and then doing a production run of them and simply retrofitting them all later is what a poor hobbiest would do. (That is being to harsh on electronics hobbiests, i was one for decades before i got my degree)
In medical device design we have to do worst case tolerance for somethings. What was done on this printer is so far from that I can not even tell what name to put on it.
3 Likes
@KevinHolmes Not to drag the thread off topic but would it not have been nice if they had explained to the public how that original laser thing had gone wrong. Knowing does not make me more sympathetic but it does make me less frustrated at the lack of transparency. There is a subtle feeling in the way a lot of customers are dealt with here of “We built the printer you just get to use it.” that bothers me. Perhaps I am too used to working in the open source domain.
It was the same story with the galvos. Any EE worth his/her salt would have looked at those original driver boards and instantly gone “That is too many trim pots to ever have low enough drift to ship.” Some how they just figured that it was ok. I think because the first few prototypes worked. I wonder if they do thermal testing? I have to question what corner cases they check.
2 Likes
To anyone at formlabs who reads my two above posts please keep in mind this is not meant as some kind of offense or statement of “i know more than you”. I am not by nature a competitive person. The thing is these errors in judgement are something I have no humor for any more. Look up at this I was for a long time sympathetic.
2 Likes