Minimum Feature Size Test


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 printer’s results on this is extremely valuable for designing, isn’t it?


Yes, although i’m more worried about the sudden (downwards) shift in surface quality at the moment :smile:

The smallest hole i can see through is the square 600 um.
Bear in mind i haven’t 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.

Here’s 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 i’m 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 it’s my belief the fumes deposit on the surface after enough time.
Thanks again for running the test and sharing.


It’d 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 i’ve 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, i’m not talking about flakes (although there’s some of that too). No idea where that foam is coming from.


It just hit me… The reason i’m seeing crappy surfaces with black is precisely due to undercure - it’s 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, there’s an area that’s wet, with layers fused and sloppy.


Here’s 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 I’m totally blown away by resolution and detail that’s 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 didn’t want to break the fine details. Again, I’m very impressed with the results.

Retro Form 1+ Guide

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

Laser Flare & the effects on your prints - Part II

Wow @KjellNilsson, that’s supper impressive… awesome ! :hushed:


@Steve_Johnstone, Thanks. It looks like the square .6 was a success but the round .6 wasn’t. That is pretty good.
@KjellNilsson, everything you print is mind blowing. Do you have a laser spot test to share? I don’t know what it would look like but I’m interested. If not no big deal.


I wish i could get surfaces that clean.


JoshK, this is what my laser spot looks like…


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.



just tried to get some resin, and the store is offline - can anyone else get there?


See the measurement figures some posts above. I fully realise that measure that small parts (and a bit soft…) with a caliper is not very exact but it was the only method available to me. To measure the tiniest rods I had to cut them off and place the in the caliper.

I have now also tried to print the file at 25 microns just to compare. Then the tiniest sqaure ros failed and there are som “extra structures” aside the tiniest rods. My guess is that this represents curing made by the part of the laser beam outside the absolute focus (flair, rabbit ears or whatever) which is only produced at this resolution with 4 times as many laser passages as the 100 micron file. It ´s amazing that the very thin bi-rod aside the smallest round one survives to that hight during all the peel cycles before it eventually fails.


@KjellNilsson, Have you printed anything tall and thin lately? I’m wondering if that was perfect too? Your small stuff is amazing even with the laser spot test flared. I’m curious if any flare issues show up on your tall stuff.


Sorry for going back to the previous (JoshK’s) test, but here’s a print in black, at castable setting, at 50um from my printer, for comparison…

The “good” side:

The “bad” side:

Looking through:


Thanks. It looks like you got a better surface on the face by rolling it a bit from before.

So far everybody has nailed the 900 micron and larger. Nobody has achieved 300 micron, and it’s hit or miss on the 600 micron.


If you mean light visible through 300 micron - i doubt you’ll get that. The surface (especially inside a hole) is too irregular for that. On top of that, there’s no way to get the resin inside such a hole out - the surface tension is simply too strong.

As such, light passing through the 300 micron hole is not a good indicator.
Being able to discern the circle from the square, however, is.

Re: surface quality - i think it’s due to castable setting, but mostly due to regularity/irregularity of the layer striations. When you put the previous print and this one side by side, there is really not that much of a difference, and the interesting thing is, the surface is the worst near the 300 um hole side, regardless of whether it’s facing up or down (previous print had that side angled up).


Remember we are testing a whole manufacturing process, not one single part of it. The methods, resin, hardware, and software is all one system that we are testing. It either makes a hole or it doesn’t.