0.3 degrees over 100mm is still over 0.5mm difference. Which is fine for organics but I design three dimensional puzzles, a little skew is really not good for me.
Also Iāve had worse numbers than just 0.3 degrees off but I figured Iād just do the math using the numbers you provided. 
Hey guys I followed the laser flare threads a bit and I have been quite as I donāt have the big knowledge of the technology. Anyway I have some questions and was hoping you can clear things up.
I was reading on this site http://form1printer.pbworks.com/w/page/73582883/Replacement%20Components about the laser especially and was trying to find a similar laser that could be possibly replaced with. There are 405nm lasers to get but I guess its hard to just replace it without a suitable designed circuit board?
Another question is why canāt we use a focal lens on top of the laser instead of a choke? Sorry if this was already answered.
http://www.ebay.com/itm/Short-Focal-Length-Laser-Diode-Collimating-Lens-Collimator-Lens-405nm-445nm-/111598181259
@MarcusKnorr see here http://marketplace.idexop.com/store/SupportDocuments/Lens_Combination_FormulasWEB.pdf for the equation for combined focal length of two lenses.
Adding another convex lens to the existing system will dramactically reduce the focal length and hence defocus the laser spot. Collimating lenses like that one donāt produce collimated light on their own - they have to be used in combination with another lens - or with light that is already naturally very divergent.
My initial thoughts ran to a weak concave lens to slightly increase the focal length - allowing for the laser to be pulled back and an iris/aperture/filter applied - but I tried several and although I could get the focal point (point of maximum convergence) at the right distance it was still very defocused.
So then I thought about a stronger concave lens plus a subsequent convex lens - and this had the added benefit that the spot profile would be initially magnified - hence making the job of a āspatial filterā to block part of the profile containing flare easier. Moreover - I was able to achieve a tightly focused spot at the right distance. However this approach can not work for two reasons.
Firstly and most importantly - as covered above in the op light path diagrams - the flare portion of the beam profile is pretty much integrated with the āgoodā light for nearly all of the path between the laser and the build surface - only when you are right up against the last lens inside the laser, can it be separated from the rest of the good light - or when you are on the build surface itself, and obviously itās impossible to do anything there.
Secondly adding two lenses requires bringing the laser back a significant distance - and hence requires a mirror - so there are now 5 extra surfaces than can reflect light and slightly reduce beam power - moreover, although it is possible to achieve a tightly focused dot on the build platform with this setup - the dot will inevitably have a slightly different shape from the default - whichever of these two effects is most important Iām not sure - but I wasnāt able to to print successfully over the whole build platform even before trying to apply an iris/spatial-filter/aperture to remove the flare.
I went through many iterations on this approach - finally arriving at the one underneath - to reach the above two conclusions; ie that this approach cannot work, and that cutting off the flare was only possible when right up against the last lens inside the laser.
Note all lenses are UV rated with AR coatings, and the mirror is a fragment cut from a larger surface first laser mirror that I have previously used in place of the main mirror without issues.
best results with above setup before trying to cut out flare - pieces were mostly ok on the hinge side, but were pretty much all hollow on non-hinge side.
Underneath is a side by side comparison of the laser default laser spot above the refocused laser spot from the system above., The grey blob is a tiny typex spot for scale on a yellow lens filter sitting on plastic in the vat frame. The shots were taken with a cheap usb microscope at 20x power with low exposure.
The refocused dot is slightly smaller than the default dot - and not as regularly round. Iām not sure whether it was this, or the slight loss of power through the extra two lenses and the mirror that caused the failures above ā¦
Regardless - Iām pretty sure the whole idea of cutting off flare using a system with an extra lens or lenses is a dead-end.
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Pretty much dead-on - thereās no point in refocusing a bad beam, itāll still have the same issue. Itās already focused anyways. All you can do is diverge and re-converge the same quality beam, nothing more. It has to be filtered immediately after the optics.
Anywho, i know iām (still) off topic, but hereās my first (non-butterfly) print, i wonder what you guysā take on it is. The height of the rook in the photos is 51mm, printed at 0.05mm layer height:
The chunk missing in the lower left is due to removal from the platform. The āfluffā at the bottom facing surfaces at the top are the flakes:
These, to me, look like what iāve seen numerous times (on surfaces facing away from the vat) with not very opaque or transparent resins, but i might be wrong. If it was in any way due to laser, iām guessing iād be seeing it in other places on the sides as well.
Hereās the bubbling:
I know it looks like itās on the surface, but itās not. Itās embedded into the wall, although there seems to be a slight leakage of resin where one of them just about intersects the surface.
Actually, now that i look at the geometryā¦
The flakes at the top are likely because the solidified layer got ripped apart during a peel.
There was nothing to support that tiny bridge of resin between the ends of the spiral columns until it built up enough layers to endure the peels. In fact, comparing it to the original Formlabs spiral rook, the gap is much much bigger and the slant of the bottom facing edge is much steeper. It looks like whoever designed the rook for Formlabs encountered the exact same issue and engineered their version around it.
So iād say you can safely disregard that part.
The bubbling, OTOH, iām still not sure about.
Thatās about as good as it gets. Chain that printer to your desk so FormLabs never exchanges it.
Hahah, iāll epoxy it to the desk and make a sacrifice to the gods of lasers and optics 
Still, i wonder what iāll get when i try the black resin.
Way higher laser output, there might still be much more significant surface artifacts.
Also, iāve put a tallish print on using the 0.2mm clear setting.
Iām curious as to what the surface quality will be considering the longer laser exposures.
@Ante_Vukorepa Will you try reprinting @KevinHolmes tall plus sign?
Thatās not just a good guess, Iād bet on it, and I am not a betting man. Formlabs can still do things to decrease the amount of this effect by changing the PDMS material, and/or reformulating the resin, and/or improving their slicing/curing algorithm to over cure some of those layers, or pad them to a slight angle to build up. However as you Iām sure know this isnāt a sign of a bad printer itās just a limitation of the method, which can be worked with and improved upon but will likely never be āfixedā.
You need to work on your technique here thatās a lot of damage. 
I know you know a lot of this, however for benefit of other users Iām going to give a rather thorough breakdown of my knowledge of bubbles. I wouldnāt be too worried yet. In my experience some small bubbling occasionally happens even on good printers. When it does happen it comes in several notably different forms.
The first is non repeatable bubbles, in this case you print and you get some bubbles, but if you print the same part in the same position and orientation again there are no bubbles, and through repeated prints they donāt come back.
Next are repeatable bubbles, with these repeated prints of the same part in the same position and orientation results in similar bubbles. You can pretty much break repeatable bubbles into three further categories.
With the more common of these when you re-position the part the bubbles appear in the same spot on the build area and on a different spot on the part, this is usually indicative of dust on the later surfaces like the large mirror or the bottom of the tank, and is easy to fix just clean the mirrors. These are not indicative of any real problem with the printer and are just a sign that itās time for you to perform some standard maintenance.
With the second most common form, the bubbles move with the part as it is moved around the print area. When the part is rotated around the z-axis the bubbles remain, however they may move around to different positions in some cases. Rotating around the x-axis and/or the y-axis sometimes fixes the problem other times may make it worse. In this category the bubbles go all the way through some part of the print from one open area in the print to another area in the print. These are commonly called blowouts and result from forces acting on a closed cell in the peel process. There are multiple places on the forums that discuss how to work with or around them. These are generally considered expected behavior and are not generally indicative of a problem with the printer. Clearly these are not what you have in this case.
In the last category of repeatable bubbles when you move the part the bubbles seems to move with it, they may get worse or better when the part is positioned in certain areas of the platform, and when the part is rotated they seem to migrate to a different side of the part maintaining their orientation to the rest of the printer. These last ones are what @Steve_Johnstone has and they are the really bad ones for which there is no simple solution.
So all in all you probably donāt have a laser problem, try some of the flare tests (cross and helix) if you want to check more precisely. However Iām still guessing you have alignment issues or a bad tank.
@Ante_Vukorepa can you take a couple shots of the top surfaces on that rook print. Also if those look like I think they do I really want to know what your laser spot looks like.
Will take some shots of the top as soon as iām done with work.
In the meantime, here are the results of printing the 4 squares:
All 4 squares measure 25.3 x 25.3 mm in X and Y.
The shortest one is 0.98mm tall.
The tallest one is 1.54mm tall.
So i was pretty much right on the money when iāve eyeballed it to 1mm then corrected myself to half that (0.5mm) due to reflection
I still have to measure the actual PDMS level, will do that when i empty the tank.
Also, yeah, planning on printing the tall crosses and the cylinder with the spiral at some point too.
Hereās the top.
You can see some more flaking/bubbling on the platform at the end of the stairs.
@Ante_Vukorepa the flaking and bubbling there is also from unsupported surfaces. The interesting part to me is on the actual top surface. Itās hard to make out but you can see it clearly in the reflection. You can clearly see the path the laser followed. From that alone Iām guessing your actual laser spot profile is quite clean. My printer with flare has the smoothest surface Iāve seen yet, however the best detail Iāve seen was on a printer with this path so pronounced you could feel the ridges.
Yes, you can clearly see (well, clearly with a magnifying glass and under the right lighting angle) the laser traces of the infill and the perimeter on the prints iāve made so far, although you canāt quite discern them with a fingernail. I assumed thatās what itās supposed to be like, since the two sample rooks (one black, one gray) i got from FormLabs before making the purchase were the same way.
@Ante_Vukorepa Iām pretty sure it is supposed to be like that. However I do not think on printers with flare problems you can see that path that well at all. So I was saying that is a good indicator your laser is cleanly focused and without significant enough flare to cause problems. Iām also assuming that that means you donāt have the same bubbling problems that @Steve_Johnstone has as a result. If you get the time sometime Iād like to see a series of shots of your laser spot. I donāt know if @Annino is going to get to it at this rate, and we still need a clean series for comparison.
Iām starting to believe the ātiltā in the PDMS layer is actually an extreme meniscus on the hinge side.
And by meniscus i donāt mean from the resin, but from the PDMS pour.
Looking at it during a print, it definitely seems like it suddenly gets thicker a cm or two away from the edge, rather than being off-level across the whole length. Also, iāve been trying to print some casings for a client (wanted to seize the opportunity and use the printer for something useful while testing and getting to grips with it) and i keep getting deformed (concave) prints in the exact spot where iām seeing the sudden thickening.
Iāve just moved the object away from the hinge side and closer to the center, going to reprint to see what happens.
@Ante_Vukorepa Hopefully the problem is just a funky tray. If so itās an easy fix.
Iāve just experienced it again. Hereās what it looks like (exaggerated mockup, iām still waiting for the print to cure):
Itās not that bent (again, exaggerated doodle), but itās fairly noticeable, especially on the little tab in the corner. That whole face facing bottom right also has a pretty bad surface quality (pockmarked). Iām now thinking it might be due to supports.
(And no, itās not the usual resin shrinkage during curing - it was like that the moment it was printed.)
Edit: Just checked, the bend is actually the other way - itās concave, not convex. Which is interesting because the previous print had it the other way around.