Is humidity effecting your SLA parts?
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  1. #1
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    Default Is humidity effecting your SLA parts?

    Over the winter the machine was producing exceptional parts. Crisp clean lines, super thin features. Come about May, June and now all through July the pieces warp once they are rinsed in the solvent. They only marginally straighten out in the curing oven.

    Just wonder if any of you have seen this behaviour during the more humid months?

    The strange thing is the building has A/C, which is supposed to dehumidify the air somewhat.

    Not sure if the resin is holding moisture or if the humidity in the machine's chamber is lowering the laser strength by beam scatter.

    Any thoughts are appreciated.

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    Moisture might also affect the resin curing if it is a reactant or byproduct of the polymerization reaction.

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    There's a chance that the resin you're using is slight hygroscopic, meaning it holds moisture, much like nylon, and when you use the solvent bath, the solvent draws the water out, causing microcavities that collapse under the weight/internal stresses of the semi-cured resin.

    If you're worried about it, you can put a few desiccate packets inside your enclosure(like the ones you find in a new pair of sneakers). These will passively dehumidify it, and if you put them out of the way, they shouldn't mess with the prints.

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    What is the specific polymer (system) that you are using ?

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    I had that thought exactly. Put a pile in, out of the way.

    The service tech came to have a look. Turned out the laser's are water cooled and the reservoir was low, causing the laser to derate the power available.

    Still confident there is a moisture issue, since the quality seems to drop during the damp seasons.

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    The System is a 3D System Viper 2i... something or other... the polymer is Clearvu

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    Quote Originally Posted by Jarrod View Post
    The System is a 3D System Viper 2i... something or other... the polymer is Clearvu
    Ok I looked at the MTDSS (Material data safety sheet) to find what the actual chemical components are for Clearvue.

    Accura ClearVue (SLA) | 3D Systems

    4,4'-Isopropylidenedicyclohexanol CAS#: 80-04-6

    ChemicalBook---Chemical Products Search

    (R)-(-)-Epichlorohydrin CAS#: 51594-55-9



    I can't really "See" anything that would directly be affected by differences in relative humidity.

    However with any epoxy-ish system IME all of the critical reagents/ accelerators and photo (cationic photo intiators) have to be kept refrigerated...

    https://www.radtech.org/proceedings/...has%20been%20-

    IME working with various polymeric systems Epoxies for example become very hygroscopic if the stoichiometry is not right (exact proportions of reagents / accelerators) is not right, sometimes you get "weeping" of polymer and other shorter chain components. All very hygroscopic.

    As I understand it the Clearvue is billed as being the most transparent on the market with "Polycarobonate " - like properties ?



    I would not expect RH (relative humidity) to affect beam and focus characteristics of the optical train and UV laser etc. to such a significant degree. I assume there's some sort of phase locked loop that keeps everything sharp as it can be (dynamically) ?

    I'm wondering if RH might be an indirect corollate (or false correlate) between what you guys may be doing seasonally ? I.e. It's warmer when it's more humid ? Its drier when it's winter - colder depending on where you are. OR vacations and semesters and shelf life of various products ? / use ? What your lab technicians do ?

    In a sense if this is not a known problem then literally this becomes a research project.

    Devise ways to isolate the problem with various test chambers. (outside of the machine.).

    Maybe someone knows the answer to your query but they probably work for 3D systems and they aren't gonna tell you ;-)

    Doing independent research may be you only bet.

    IME even some of the most stable polymers known to man do not live up to their manufacturer's claims ;-)

    Test these things yourself.

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    Quote Originally Posted by Jarrod View Post
    The service tech came to have a look. Turned out the laser's are water cooled and the reservoir was low, causing the laser to derate the power available.
    That’s probably it... incomplete curing of the layers, then it warps in rinse & postcure.

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    Moisture affects the adhesion of plastic to the extruder walls and indirectly the adhesion between the layers.


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