Small chambers inconsistent volume

I have some issues regarding printing high-resolution small-scale prints, the background information is: my project requires a small fluidic chamber with 400 microliters internal volume, I calculated this for a cylindrical chamber and made it using fusion 360. When the fluid chamber was printed and during testing, I noticed that the final volume of the chamber was not accurate and only gave me 380microliters. I reprinted this same piece 3 times and each print gave me a different final volume, I broke them open and measured the inner dimensions of the chamber only to notice that the walls have shrunken inwards, leaving me with a smaller internal volume. The dimension of the cylinder model is 5mm in diameter and 20.37 in height, the finished product had ~4.6mm diameter and ~20mm height. The printer uses Clear V4 resin and is printing at 0.025mm resolution.
What can I do to improve this situation and make my prints more accurate?

Hello @teo93 ,

Thanks for reaching out! Microfluidics in particular are a challenging type of print that require very specific post-processing steps in order to ensure that the internal chambers and cavities are flushed of any excess resin before curing. If the channels are not properly flushed with a syringe and IPA, then that liquid resin will cure and end up reducing the expected volume.

We have a white-paper on Microfluidics and Millifluidics that I think will help out with the post-processing . Please be sure to read through this guide thoroughly to get you the most accurate parts possible. If the issue persists past following all of these steps, then I would recommend you reach out to our Support Team to ensure it is not an issue with the printer. I hope this helps!

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Think of it this way: Preform out puts in something like G-code which is a path for the laser to follow. The printer does not know which side of the path should be solid, so it follows the centre of the path. This means that any edge face is extended by around half the diameter of the laser spot.

This problem shows up where there are components that have to be fitted to gather. Allowances must be made to compensate for the oversize of mating surfaces to allow them to fit together.

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Yes, but Preform knows which side of the path should be solid and has ample opportunity to correct the path before sending to the printer.

The inconsistency is likely due to partially cured resin on the chamber walls. A regular iso bath doesn’t get rid of all of it, and when you go to cure it, it shrinks your ID. Give it a regular iso bath as prescribed to get the majority of the gunk off, then get a small container with iso and a toothbrush and go to town scrubbing it. You don’t have to go crazy, just a couple of minutes, rinse with water, air dry and take a look, might need a second scrubbing. These printers tend to shrink IDs anyway, especially on clear resins, but it’s usually pretty consistent.

I’m been printing .025 tapered holes and frankly the only reliable material is white. But it’s too brittle. You need tough2000, BUT that won’t resolve small holes. At least that’s what I thought. (after lots of testing). Then I started more precision cleaning and it appears the material is hardened closer to tolerance, but the cleaning for the sludge is really hard. I use high pressure air, 99% only each time and real fine sable brushes to wash. Also have a hypodermic needle with 99% I shoot through holes. It’s a pain, but if you can get the tough materials to resolve fine details, they are great.

But do you know that it does?