I got a very viscous resin that is not a commercially available 3rd party resin, so there are no machine parameters recommendations. Someone gave to me some academic and theoretical characteristics of the resin as guidelines. Any suggestions on how I should set parameters for a very viscous resin in open mode? This will be the first time that I will print a non-formlabs resin in my Form2 machine.
Try printing with Tough setting. Tough is pretty viscous, too.
You might ask the manufacturer what settings they recommend. Most third party resin suppliers list which PreForm settings work best. Flexible will be the most viscous followed by Tough but there will be other important settings like laser exposure to account for.
@Frew: This is not a commercially available resin, and the processing characteristics have not been characterized. All I have is some academic/theoretical characteristics derived from mathematical models/equations.
That sounds interesting and your best bet is probably going to be iterating through different material settings in Open Mode to see which is best suited. You should post your results! (if you can).
@frew: exactly what do you mean by “there will be other important settings like laser exposure to account for”? Can you elaborate on this please?
I think what he means, is in addition to considering the viscosity, you will want to consider laser exposure.
The various resin profiles adjust the laser exposure. For instance, clear has lower exposure than say gray, and castable has more exposure than gray. I believe transparent is the lowest setting and castable the highest.
I could be wrong, but since the wiper is disabled in open mode, laser exposure is probably a more important consideration than viscosity.
I really wish Formlabs would just allow us to directly control exposure other than trying various resin profiles on the Form 2. 
@Ken_Smith 3DTOPO has it right. The laser exposure is not the same for each resin nor is it uniform throughout a print. The first couple of layers have increased laser exposure to help with adhesion. These parameters can be tweaked with OpenFL for the Form 1/1+ and on the Form 2, the best way to go about it is to iterate through resin profiles to figure out which works best.
@Frew: Thanks for this confirmation. But how and where do I navigate to tweak the laser exposure? I navigated through the screens on my Form2 machine and did not find any parameters I could tweak, and I also navigated in PreForm and again did not find any parameters that I could tweak. I must be missing something here. How can I go about doing these tweaks? Thanks for your patience with me on this.
Laser exposure can’t be precisely controlled on the Form 2. OpenFL is only available for the Form 1 and 1+ presently. The best way to go about this will be to try different material settings and see which produces the best prints. With commercial 3rd party resins, usually manufacturers know which settings work and will make recommendations. If this is an experimental resin, iteration is the best way to go.
@Frew: Okay, it is clear - at least I think so 
. So all I can do in Open Mode is to change the material type selection, and the machine will use the preprogrammed settings for any given material type. Is this the case?
Sounds like you’ve got it right. Use Open Mode and iterate through material settings until you find the one that works best.
I would probably start with Clear v1 profile first. If it is slightly under-exposed, then go to Gray v1, then white V1, Gray v2, Clear v2, Black then castable.
There is a chart of laser exposures in this thread.
@Frew I think it would be really helpful if Formlabs published a similar chart, updated with all the resins that have been introduced since that graph was made.
P.S. if you get overexposed results using Clear v1 profile, you might consider incrementally adding a small amount of pigment to the resin until it is no longer over-cured.
On the other hand, if it is under exposed using the castable profile, then I suppose there is not much you can do other than add more activators to the resin.
(assuming you are using a Form 2)
@3DTOPO: Yes, I have a Form2 machine. Thank you for this additional information. I have a very viscous resin (I actually have not yet seen it, but an R&D colleague who developed the material told me that it is very viscous), so I was thinking to initially try the Flexible material profile. Is there any specific reason you are suggesting the Clear v1 profile as the first try?
You’re quite welcome!
Yes, Clear v1 is apparently the lowest setting. If the resin is over-reactive, scarring/burning the silicone layer is possible. So I would start with the lowest exposure and go from there.
In Open Mode, the wiper is disabled, I could be wrong, but I don’t think there is reason to try to match viscosity.
I’d be curious to learn more about the resin if you are able to share any more details.
Another thought is increasing the temperature will likely make the resin less viscous. It is my understanding, that in general (and all else being equal) that less viscous resin produces higher quality prints. I also think having it set to the same temperature improves repeatability.
In Open Mode, the heater is disabled, but I have installed a heater pad in my build chamber that allows me to manually increase the temperature. I usually set it for 100F. I have been meaning to write up a BOM and instructions and share them in this forum. I’ll post a link here when it is up.
Temperature accelerates failure rate. If by “build chamber” you mean that you’re putting the entire printer in a chamber at 100ºF, you’re not doing yourself a favor in terms of long term reliability. Component temperatures inside the printer will be much higher than at an ambient of 70ºF. Some components (like the Flash memory the FW and data is stored on) are very sensitive to higher temperature. I can’t quantify the impact of what I’m assuming you’re doing, but the relationship between temperature and failure rate is exponential so if you’re doing this, I wouldn’t recommend doing this. 
Nope - not what I am doing. By build chamber I mean the enclosed print volume - not the entire machine.
The temperature I heat it to is about the same temperature Formlabs heats the resin too when it isn’t disabled.