For a bottom-up stererolithography 3D printer, the most common failure would be the adhesion problem which means that you only get support and raft structures on the build plate after 3D printing instead of the intended object. In this case you will see part of the model still sticking to build plate and part of it sticking to resin vat.
Though this experience is so frustrating, sometimes you even get nothing on the build plate and only raft/bottomsticking to resin vat. So before solveing this issue, let’s make clear why the raft/bottom is not sticking to build plate first.
Step 1: Why the Raft/bottom Is Not Sticking to Build Plate?
Most of the reasons why the raft/bottom is not sticking to build plate are related to the build plate and the first layer. If the build plate is not flat, you will likely have adhesion problems and possible failures especially when you are attempting large prints. The slant raft or bottom may cause the failures for the generation of supports. Then the print job fails. Besides, if the distance between the screen and the build plate is too huge, your print won’t stick properly to the build plate. While it might be tempting to start printing, the first step is to make sure your 3D printer is properly calibrated and leveled.
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And if the first layer of your model is too thin, the force will not be enough to peel the first layer away from the FEP film. If printed too fast, the first layer do not have time to bond to the build plate. Also increase exposure time of your first layer. Make it around 10 times longer than your normal layer cure time.
Step 2: Prints Aren’t Sticking to the Build Plate
Fortunately, now support and raft structures have sticked to the build plate. But where is the print? When you're experiencing difficulties with prints sticking to the build plate, there still could be a few things going on. Here we use ChiTuBox to calibrate the support settings and download tyrant scale rending claws from thingiverse to test.
Step 3: Contact Depth, Upper Diameter and Lower Diameter
The key parameter of supports usually is its top. Top refers to the top part of the support. The top part is the key factor to link the model and support. And a little note, there are 3 parameters about the top: contact depth, upper diameter and lower diameter.
The deeper the contact depth, the deeper the support tip inserts into the model. We need to confirm that the contact depth is deep enough to win the tug of war between the build plate and the FEP film in the bottom of the vat. But this operation will also leave more visible marks after removal.
The thicker the upper diameter, the stronger the support is. And so to the lower diameter. It's helpful to reasonably adjust the upper diameter and lower diameter and also avoid that the middle part cann’t afford the heavy top.
Step 4: First Try to Print the Object
The model “tyrant scale rending claws” is just a small one (26.63*60.46*47.21mm). So at first, we thoght the “light” parameters with 0.2mm contact depth, 0.2mm upper diameter and 0.6mm lower diameter were enough to hold the print.
Step 5: Second Try to Print the Object
Unfortunately, the print job fails. We lose the tug of war. Then we change the “light” parameters to “Medium” ones and adjust those parameters manually with 0.4mm contact depth, 0.4mm upper diameter and 0.9mm lower diameter.
As illustrated above, the truth seems to be that the “medium” version saves even more materials that the “light” one. Or at least it seems to be. Besides the top, the diameter of middle increased 0.2mm from the “light” version to the “medium” version.
Excluding some equipment and hardware factors, most adhesion problems are due to the poor settings of support structures. There is no “one-fits-all” parameter setting that can be duplicated for any type of resin or with any type of 3D design. That means, the printing parameters may differ every time you have a new resin or a very different model. However, rest assured! Just try it! Follow this general guideline to customize printing parameter for each print.
Model source: https://www.thingiverse.com/thing:2520821