I have couple weeks with Form3. I have recently printed two models. I saw on my prints that surface finish is not good where the supports are in my model. it supposed to be flat but the face has like bumps
That is totally normal. It’s part of the process. If possible place supports on non-critical areas of your print, use snips to cut them (if you peel them off you can end up with little dimples instead). Use an xacto blade to remove excess and sand.
I’m printing mainly flat shells and I witness this effect - the surfaces facing to the build plate when they are close to horizontal (below 30-40 deg) and also if there are supports in the area appear covered with cured resin. All details in this area are smeared, parasitic cured resin is thicker around the supports. See this conversation in the foruma:
The solution is simple in your case - just rotate the detail to be 60-70 deg to build plate and ensure you have enough supports.
I have found if I have to orient the part in such a way that the supports are in contact with a surface that I care the finish then I change the touch point size to the smallest size and then increase the density of the supports as necessary.
This appears to be a weakness for all resin printers. The support surface will always have this “pillowing” and it becomes pretty creative to try to minimize it. Not as much of a problem printing figures but on parts like your example, it can be critical and require a LOT of cleanup by hand. Even those printers that are in the 100k range have this though it is almost negligible - almost. The difference (it appears to me) is in the resin. I wonder if thinner resins will be better at not having this?
Thinner resins would work better since they would flow around more, the thicker resin is more likely to stay in the same place and receive repeated exposure from indirect light from the laser. That’s also why there’s more material around supports because the resin sticks in the crevices more easily.
The issue with thinner resin though is that the pigment will settle out of it more quickly, you can end up needing to stir it after each print to get it mixed again, not sure if it would be as bad enough to where it would settle too much during a longer print.
Though I think there might be able to develop a printing method where the printer could spread a small layer of resin on the bottom of the tank for each layer and so keeping the amount of resin in the tank very thin rather than submerging the print each time could reduce the effect. Doing that method might even benefit from oxygen inhibiting the top of the resin from curing.
This effect is present in every SLA or DLP print. It is much less severe in the upper echelon machines (like Perfactory) but is still there. Not only is it on the first part layer where the supports attach but this “pillowing” is present on every first layer of every feature. When the part is removed and washed, check the underside of every feature point on the print. You will find a thicker layer build up when you compare it to the file itself.
From my experience the third-party resins are all thinner than the Formlabs resin, but I haven’t found any that print as well, I think it’s the case that they cure more quickly and all of the printer material settings expose too long for those materials to get comparable results to the Formlabs resins.
+1 to @MattBowen33 suggestion to decreasing the touchpoint size and increasing the density of the supports. This will result in a better supported part (less “spans” between supports) that are also easier to tear off and leave smaller removal marks. You do end up with more small touchpoint marks overall but they are easier to sand off individually.
I think this is two different issues. The “pillowing” effect shown in the pics of the original post is much more of a concern than the touchpoints of the supports. These are pretty easy to take care of with a little sanding or filing. One thing I have noticed is that removing the supports for the High Temp resin is usually best if done before curing. The parts are really brittle once cured and can chip off at the places where the supports touch. This may not be practical for some parts that need the extra support while curing to prevent curling. In general, I have had much better detailed prints (when examined with a stereo microscope) from the High Temp resin.