Kjell, Again, those look great.
@Ante_Vukorepa, What do you think about saying the printer promises 300 micron deviation and at least 900 micron features sizes?
What iām trying to say isā¦ In the theoretical case the curing spot was perfectly known and consistent, the slicer could compensate for the width of the cured spot and - again, in theory - generate infinitesimally small holes. The limit would then be the resolution of galvos (which i suspect is somewhere on the order of 10-20 um, ideally).
Thatās for the holes.
For positive features, the limit is always the laser, there is no getting around it. In the ideal theoretical case above, that would be 300 um. Again, thatās for positive features, e.g. bumps, corner radiuses) and in the case of an ideal laser spot and ideal curing profile.
In reality, due to flare and unknown variations in the laser beam profile, resin curing etc. both numbers are probably way off and will differ from printer to printer. Still, minimum feature should always be slightly bigger than the minimum hole.
BTW: printing your test STL now, at 50 um, black.
Yea I understand what youāre saying about the spot itself is not what determines min hole size. That is actually determined by the fuzzy nature of the spot and the resinās reaction to fuzzy. How small can the hole feature be and still be purged of partially cured resin? Thatās what this test can discover.
Iām not saying this is not normal for a laser to be fuzzy (Gaussian). It is normal to a point, but what is theoretically possible for the photograph will not be discovered here. The goal of this test is to experimentally determine what the average Form1+ printer can deliver. When selling something itās smart to under promise and over deliver.
I donāt think FormLabs was intentionally lying about what to expect, I just donāt think they really knew back when they wrote the specs. Today, that question can be answered.
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Well, the 50um print turned outā¦ Interesting.
The smallest holes are visible.
But overall, this has got to be the ugliest print i ever had from my printer.
The base has skins on one side (iām guessing accumulation due to flare), the top surface is ugly, event the supports turned out bumpy. Not sure what to say (this wasnāt the first black 50um print i did - i also did the cylinder with double helix - you can see that one in @KevinHolmesā flare fix thread).
The funny thing is, i cleaned out the tank and shook the bottle really REALLY well and repoured to do this test. Printing another one at 100 um in an effort to try and figure whatās going on.
Sounds good, I am looking forward to a few pics when you get the time.
And for anyone following along, I canāt say enough, this thread is just about discovering what minimum feature size the Form1+ printers are doing. Not what would be possible though added settings or hardware changes.
Here we go:
That was 50 um, printed diagonally at 45 degrees.
Iām now printing 100 um, vertically and if i find some time, iāll try two 50 um side by side, one horizontal, one vertical (iām curious to see the difference - horizontal one should be the worst, vertical should be the best, but itād be nice to confirm and see the difference).
Thanks. This is one more set of observations for our study. What is the smallest set you can see through?
Your last print was a mechanical part, I bet seeing your printerās results on this is extremely valuable for designing, isnāt it?
Yes, although iām more worried about the sudden (downwards) shift in surface quality at the moment 
The smallest hole i can see through is the square 600 um.
Bear in mind i havenāt tried squeezing IPA through any of the holes and i kept them in the IPA for a pretty brief time (just enough for them to get the slime off).
Another thing to bear in mind - when printing diagonally like this, the smallest hole that will be completely passable will be more limited by the layer height than at first apparent. You might also get holes that are smaller or larger than they should be, or perhaps even completely closed.
Hereās a very very simplified (and not very accurate - note the assumed X/Y resolution in the pic is the same as layer height) illustration, just to give the idea of what iām aiming at:
Yea that diagram is a whole software discussion in itself. As far as your surface quality degrading, maybe check your mirrors with careful back-lighting. Maybe that would be a good thread for troubleshooting. If you store the resin in the printer itās my belief the fumes deposit on the surface after enough time.
Thanks again for running the test and sharing.
Itād definitely appear either my laser is underpowered or my bottle of black is out of whack (or perhaps both). For one, the infill on the top of the vertically printed test looks like swiss cheese (which iāve already noticed on the double helix cylinder). Just the infill, mind you, the perimeter is fine(ish).
On top of that, for some reason, even though the resin in the tank is free of bubbles, the object keeps foaming up like crazy during the print. And no, iām not talking about flakes (although thereās some of that too). No idea where that foam is coming from.
It just hit meā¦ The reason iām seeing crappy surfaces with black is precisely due to undercure - itās the resin from the infill seeping through the perimeters here and there.
I just looked at the vertical print up close and there are layers that are perfect (and sharply delineated), then every once in a while, thereās an area thatās wet, with layers fused and sloppy.
Hereās my offering before my printer goes back for repair.
Printed in clear v2 resin @0.1mm layer height, auto orientation.
Even with my laser problems Iām totally blown away by resolution and detail thatās achievable on the Form1+
I also setup a print to test the positive shapes of @JoshK test, plus a small semi circle to test minimum wall thickness.
You can download the files here - LINK
Printed in clear v2 resin @0.1mm layer height, auto orientation.
Due to my laser problem there was quite a bit of part cured resin & some flaking. I was very gentle with the cleaning as I didnāt want to break the fine details. Again, Iām very impressed with the results.
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Interesting!
I wonder what the actual size of that 300um pillar is.
Here is one more test printed at 100 micron, black. Dimensions measured with digital caliper:
Round pillars, 0.27, 0.54, 0.88, 1.15 and 1.45
Sqare pillars, 0.26.x 0.27, 0.52 x0.50, 0.85 x 0.82, 1.18 x 1.15 and 1.48 x 1.42
Walls, 0.36, 0.55, 0.95, 1.17 and 1.45
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Wow @KjellNilsson, thatās supper impressiveā¦ awesome ! 
@Steve_Johnstone, Thanks. It looks like the square .6 was a success but the round .6 wasnāt. That is pretty good.
@KjellNilsson, everything you print is mind blowing. Do you have a laser spot test to share? I donāt know what it would look like but Iām interested. If not no big deal.
I wish i could get surfaces that clean.
JoshK, this is what my laser spot looks likeā¦
Holy F-ing WOW! Those .3mm rods look amazing! A human hair is ~8 thousandths of an inch, and those are ~11 thousandths! Can you throw the calipers on that and tell how accurate they are?
I gotta get some black resin for sure.
-C
just tried to get some resin, and the store is offline - can anyone else get there?