Currently unsupported prints are overexposed for the first 5mm. For a supported print you want to overexpose to adhere to the bed and to get the support raft to be nice and hard for easy removal.
The problem is this setting remains when you print directly on the build plate with no supports. The default causes closed holes and ridges for the first 5mm. The software already detects and nags when there are no supports. When the user selects yes I’m a dummy and want to continue it would be nice to reduce the over exposed layers to 0.5mm.
I’ve seen this for a few small parts and for small molds. With the flat bottoms I don’t need to waste supports on a lot of these prints.
It’s likely that even without supports it needs to expose the first layers for a longer amount of time to make sure that the print is stable.
A 0.5mm layer of overexposure works fine for adhesion (used open FL to check). If we knew reasonable settings for the Formlabs resins at different layer heights this could be done in open FL.
While the majority of parts print best with supports, there’s an advantage to printing certain geometries on their own. As far as I know, the overexposure of the first ~5 mm is applied to encourage adherence for all prints. I think what we’d be looking at here is an entirely different sequence for curing and compressing the initial layers of all prints OR developing separate settings (currently one set for each resin type and layer height) for the unsupported parts. Given this, I’m also very intrigued what could be imagined and created for unsupported parts to have different settings that output the same or better print success compared to the current settings. It’s a very thought-provoking challenge!
I know I would like to see a set of profiles that have the 5mm changed to anywhere between .5mm and 1mm thick that is specifically designed for printing without rafts, maybe let us decide based upon our projects specific needs. The compression and overexposure can stay the same for pass count up to .5mm or 1mm. Then like the regular resin profiles, the transition that is present in the current profile can stay, ensuring a proper transition. Then after x layers (what ever the current transition is), the model prints just like all the others. I was messing around with this before my tilt motor started acting up and now that my printers new tilt motor is in and functioning ( THANKS FORMLABS!!) I have been considering working on my stamp project again where I print the stamp flat on the build platform. But I need this feature or I need to continue to play with OpenFL. I would much rather be able to select a profile FL writes knowing all the exposure, spends and feeds are correct.
The more I think about this, I have another project or two that would benefit from this.
I, too, would love to be able to control the curing of the first 5mm. 80% of my work is lithophanes. These are about 100mm x 140mm by 6.22mm thick. But they are nearly impossible to do flat. Adding supports requires me to put it up at a steep angle and the base and support at least double the resin usage. Also, consider the time it takes to print upright vs flat. 6.22 mm of printing vs 150mm or so. At .5 microns, the upright version takes me 8-12 hours. Flat would be a mere fraction of that.
I have not yet played with open mode, but seeing it mentioned here, I will try that. I prefer FL develop a best-practices resolution for this.
I have done lithophanes for years (CNC router), but FL SLA is certainly the best method I have found for the quality. Samples from my old methods sell the concept. But doing it in white (V2) resin gets me instant orders every time I show what is possible. I just need to find a way to make it time-effective as well.
do you print jewelry models?
yes I print jewelry models. most of what I do is jewelry
I think the main problem is not over curing the first few layers so much as it is the compressing that goes along with it. Unsupported parts then to come out 0.010-0.15" shorter than the cad geometry which i assume can be attributed to the compressing of the first several mm. Also you can sometimes see a distinct line in the part a few mm up into it when printing unsupported. It would be great if we could say half the numbers of layers that get squished.
I bought a Form 1+ to print directly on the bed. These parts work best direct on the bed. I design for SLA direct-to-bed printing.
I understand the issue of PDMS to build plate parallelism. I am able to compensate without any issues. I am also able to compensate for compression.
The overexposure on first 5mm when I’m printing without supports is troublesome.
I would use OpenFL but there aren’t enough profiles available, and quite frankly, I prefer to use up-to-date software. I’m using Clear v3 25 micron.
As I commented in your other post about the bloat. You can use the latest flavor of Preform if you wish and edit the FLP layers after they are uploaded to the printer.
I think it would be great if OpenFL was updated with the latest resin profiles but it isn’t completely necessary as editing FLP files doesn’t use OpenFL.
I agree on this as well. I’m using my printer for jewelry, and I would like to be able to minimize print time with fewer layers. In most cases, I am not using PreForm’s supports.
Also, there is a line that appears around maybe 5-6mm up…is this part of the same issue?
I, too, am badly in need of an advanced toggle to adjust the overexposure height. At least I think I am. I’ve got a finished, direct-on-base part that comes out beautifully except for a terrible, ugly-arse layer line near the 5mm mark.
I spent hours troubleshooting layer shifting, manually constructing loads of supports around that layer, etc., before I examined it more closely and realized this may not be a shift, but rather something more like overexposure or compression. To the touch, the walls feel like they contract inward around the entire perimeter of my print after it hits that layer. Smells like an artifact of overexposure switching off.
When it occurs, the line is always consistently at the same height in every print (roughly 4.6mm; also note my model has 0.45mm of “extra base” at the bottom which gets consumed by compression).
Interestingly, in one test where I sliced my model at 6.5mm, the line did not occur (picture on left, notice the clean space under the “e” and rest of text). Does Preform have some logic in it that adjusts overexposure based on model geometry?
I do also get some banding at layers where the holes are encountered but it’s less pronounced.
For the first 5mm it has a different exposure so that it can stick better to the platform. They haven’t done anything so far to avoid the issue when printing something directly to the platform.