Laser Flare & the effects on your print

This thread follows on from –

Previously it was my belief that cold resin was at the root of the major defects I was experiencing, with the laser flare compounding the effect. To some extent this is still true because the colder the resin is, the thicker it becomes. The effect of laser flare further thickens the resin whilst printing. It’s this part cured resin with the consistency of jelly, that cause the major defects.

Bringing the printer into a warmer room helped significantly with the major defects, but print surface quality, perpendicular to the laser flare (rear faces), were poor.

This was until I changed from clear v1 to clear v2 resin. Now the effects of laser flare, IMO are even worse.

The two prints below are proof of concept molds for a project I’m working on. In the video at the end I go into a lot more detail and also show Preform orientation etc.

Core Test Mold

  • FormLabs Clear v2 resin
  • 0.2mm layer height
  • 17c – 20c room ambient temperature.

CAD Render of Core Test Mold

Rear facing surface - most at risk from laser flare

Rear face detail

Cavity Test Mold

  • FormLabs Clear v2 resin
  • 0.05mm layer height
  • 17c – 20c room ambient temperature.

CAD Render of Cavity Test Mold

Fresh out of the printer

Rear face - worst affected by laser flare

Front face - not so affected by Laser Flare


@Steve_Johnstone so still with the bubbling - and most definitely on the flare side - that makes it a much worse problem than just flaking and washed solid surface corrugation, as I reported in my main thread.

I think that absolutely warrants a replacement printer - which has pased much more stringent QA tests than they what have been using - since it’s clear that not all printers have flare problems.

I’d raise a ticket for a replacement myself, but I’m not quite ready to quit on a mod-solution yet.

@Steve_Johnstone that positive piece - though, I’m fairly sure that flare is not the whole issue - it seems you went with solid?

The problem is that peeling-vat-SLA-printers are fundamentally limited in the surface area that can be successfully printed per layer.

That juddered layer effect you have on the first piece is typical of the effect you get when the peel stresses are too high.

You can hear it and see it when this is the case - the vat separates from the build with an audible thunk - and you can see the vat and build platform jerk at the same time.

Obviously flare is playing its part in the poor surface quality there, but I really think it would have turned out much better if it wasn’t solid.

“What would we call that.”

I propose “dandruff”.


I second Dandruff!

Yip, it looks like dandruff when it comes off the printer, but when its cleaned and cured, looks like termites have had a go at it.

Agreed, I’ve redesigned it similar to the cavity mold part and will reprint it at 0.1mm layer height.

Just a quick update -

I shelled the core part of the mold for a wall thicknesses between 3mm & 5mm. In Preform I angled the model as much as I could and printed it at 0.1mm LH.

The print came out much better with no major surface defects :smile:.

The core part sanded and polished fine. 0.1mm layer heights are more the acquitted for the internal cast faces that no ones going to see. I may try and print it again at 0.2mm.

Sanded and polished the cavity part of the mold and the critical surfaces came out fine, so its good to use for the casting tests.

Core & Cavity ready for action

I’m hoping to cast the first test piece after work tonight…

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That surface looks like a nightmare @Steve_Johnstone! Luckily with sanding you’ll atleast be able to work with it. Though printing these for customers is probably a no-go… Looking forward to the casted result!

@Steve_Johnstone - another thought on bubbling - I’m becoming more and more convinced that it happens more around supports - especially when close packed. So it may be that the bubbling you’re seeing there is not entirely due to it being the flare side, it’s probably a combination of supports and flaking acting in concert as super effective air traps.

Yeah, there is no way I could offer this to a customer. Until I can get to the bottom of this, I’m not even offering this service. There is nothing worse then letting a customer down.

In the background support are still working with me on this and at the moment it’s just good to get usable prints of it, if only for in house R&D.

That’s a good point @KevinHolmes and worth thinking about when I next print.

is this something that affect every printer? it looks like a mayor flaw… I mean pay $3500 for a printer that does that… I have not seen such problems on mine yet… crossing my fingers…

Hi @Victor_Wolansky

No certainly not. I think there are four users on the forum with this kind of issue, but there may be others out there, either working with FL support or unreported.

The latest from FL support is that they are aware of this issue on some parts, printed in clear resin at .05mm. They are working on a material setting change to fix it, which make me think that @KevinHolmes observations earlier may have something to do with it… who knows, its all still “black magic to me” :blush:


My Form1+ shipped today.
Fingers crossed, knocking on wood etc.


I think that there are a lot more than 4, but most like me don’t post much. I am certainly having issues that I think are misshapen laser i.e. rough surfaces on all the forward facing areas, but all I get is a charming support person telling me to clean mirrors again. I have a 3month old form 1+ which has to have the cleanest mirrors this side of the Hubble telescope.


LOL… Yeah that’s Formlabs support. Supposedly according to @Sam_Jacoby they are now more aware of these problems, and should be responding differently… Oh well, guess not.

I have a different opinion about what might be the issue here.

Abberations in the illumination laser beam should cause systematic errors throughout the print. But here, we see somewhat of a random error here and there. The globular structure of these errors suggest to me that it’s one of two problems: (1) prematurely polymerized resin sticking onto the surfaces and (2) some sort of a galvanometer malfunction, leading to jitter/backlash that create random structures or delays that create larger voxels during that delay. If it’s (1), then the only solution really is to reformulate the resin to work on a variety of printers in variety of environmental conditions (different humidity and gas content) e.g. by adding inhibitory agents. This may be too much work for DIY (but if anyone’s interested, I can offer more suggestions; I’ve seen this happen before on a research-grade stereolithography system with problem (1), and was able to fix it by modifying the resin.). If it’s (2), then you might want to send your printer in for repairs.

I don’t think that there is anything random about what I see. The laser energy outside of the main spot is not enough to give a full cure at one pass, so it creates a ‘gelled’ resin area next to the print. Eventually after a few passes (layers), this gelled area is cured enough and bonds onto the main part thus you see a pattern of an extra lump adhered every few layers. This can be minor and result in a rough surface, or major resulting in large flaps attached at intervals.
What supports this hypothesis is that the effect is so much worse on vertical walls, where the laser hits the same area repeatedly, and it is not see on sloping faces.