Build Your Own SLA/SLS

I've finally got an early prototype working using the top-down method, an Acer H6510BD, and Fun To Do Industrial Blend, but I'm having a few issues currently that I'm working on figuring out.

First thing - leveling the print bed - what types of methods are good for this in a top down set up? There is a lot of info here about this with bottom up but much less about top down systems.

Second - I am having trouble finding a cure time/brightness for my projector. I'm using an Acer H6510BD positioned for 100 micron resolution. When I set the brightness too far up I have issues with the entire print bed curing where it shouldn't be. I'm also having trouble dialing in a good cure time. Can anyone suggest some good settings for this projector? Or settings for any similar projector using the top down method?

Third - what are you all using to scrape cured resin off your build plates? I've been using a chisel but that has damaged the build plate I am using (steel sheet metal right now) and it seems like parts are not sticking very well to it now.

Fourth - has anyone experienced having the resin bubble up when being cured rather than curing flat? I'm assuming this is an issue which is more common with top down. It seems to happen more often when curing large amounts of space on the first levels of the print.

Thanks to everyone taking part in this forum, and a big thanks to PacManFan for setting it up and for your amazing work with creation workshop!

I think excessive photoinitiator which is meant to allow very fast curing is not helpful. One of Funtodo's main claims seems to be this type of very fast cure. Curing very quickly leads to greater stress and causes a lot more worries about external light. With Makerjuice (G+ or SubF) the background light from the projector has no effect even after hours and hours. I run the unit with full light (100W warm white LED bulb) in my office.

For leveling on top down it's a trial and error. Also, i build a layer with the build plate just above the resin level (manually squirt clear resin onto the build plate) and then let it start the build cycle. This requires that all parts be supported so that the build discrepancy (1 or 2mm) gets absorbed into the support structure.

Thanks for the input guys. I took a break for a while but I'm back setting things up with some new improvements to my build and I will get to testing exposure times. I think the primary issue so far has been that my layers were not settling out properly and my exposure times were to high. Also I was using a flat piece of sheet metal without holes in it which I think is why my layers were taking eons to settle out.

Right now I am working on a 2 part detachable build platform with holes drilled into it. This should solve my issue of destroying the platform trying to get the parts off! Now I will just pull of the platform and put it straight into an alcohol bath - this will keep my build plate clean and allow for much easier part removal. Also I was printing large flat parts directly to the bed which made them even harder to remove. I will now be experimenting more with support structures.

I think it would be great to start a thread with resin / projector cure times if there isn't already one. If there is one someone let me know, otherwise I'll go ahead and start one. Cure times can be a bit frustrating when first setting up when also dealing with a bunch of other things to figure out.

How about build supports for all you top-down people out there? I've seen a lot of people having issues with large holes on the bottoms of their prints. For me I am going to be printing objects with large flat bottoms pretty often. I'm not there yet but I am wondering how well this will work using build supports.

Vaughn thanks for your input - we have a very similar set up and I've been following your thread and posts - good stuff keep it up!

BTW for everyone using an Acer H6510BD, I'll post a link for a great projector mount that you can get for $25 that works pretty well. You have to play with the arms a fair amount to get them to work with the mounts on the projector. The mount comes with 4 arms - the two shortened ones are next to eachother. I swapped this so that they are across from each other in order to make it fit. Piece of cake.

http://www.amazon.com/gp/product/B000TU ... UTF8&psc=1