How I prevent failed printouts on my sla 3d printer

I have found that doing the following things have cut the number of failed prints I have when using my 3d printer to almost none.

I “paint” the build plate face with resin and harden it before each print run. The resin does not naturally want to stick to my un anodized aluminum build plate but what I have found is that coating the face of the build plate with resin seems to create a resin “suction cup” and during printing the first few base layers of a printout stick to that suction cup very well.  I have to build up the resin coat on the build plate in several very thin layers curing each layer before the next is applied to build up a decent thickness I have since found that a very thick initial layer works best, so if you are going to pre-coat your build plate slather the resin on especially for pigmented resin (I use a nail curing lamp to cure the build plate coating and to post cure parts). Since the resin does not really stick to the aluminum build plate very strongly after a part is finished printing removing it from the build plate is just a matter of getting a putty knife or spatula under an edge and “breaking” the vacuum, then the part peels right off with very little effort. I prep the build plate for the next print run by lightly sanding the build plate face to “feather” the edges of the resin left on the build plate before I re-coat it.

I have found that trying to print large solid parts are a no no, the combination of part shrinkage and heat buildup in the part during printing will make the part separate from the build plate every time.  I always hollow any part that is large enough to have 1-2mm thick walls and a hollow able interior (for example, a 6mm thick box could have a 2mm thick hollow inside with 2mm walls). I try to use 2mm walls when I can because I find that overhangs and unsupported flat areas hold up well with that wall thickness. Hollow parts also seem to shrink less.  I will have a post on how I prep, hollow and make resin drain holes with stl files soon.

I float the part I’m printing on supports. Supports do a few things, they provide a layer that does not want to separate from the build plate if the base (foot) of the supports are kept reasonably thin (I like my supports base layer to look like an array of slightly overlapping circles), the supports themselves “soak up” shrinkage from the part they are supporting (sometimes you can even see the supports bending slightly inward during a print run). I generally use a minimum support height of 5mm and I will often tilt the part I’m printing 3 or 4 degrees around both the x and y axis especially for parts with large flat areas.

When printing a part I keep enough resin in the vat to keep the part’s build face under the resin surface while the vat is tilting.  I have found that if I do not do this I may get gaps in the edges of the part being printed (an air bubble sitting in one place for a couple of layers seems to be one cause of this problem although a worn out vat floor release layer or lack of supports under certain profiles are also suspects).

I have also been doing this lately:  vat floor refresh


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