At the moment it’s an unfair lottery when generating supports on large parts with hollow insides as to whether the raft will be hollow to match or whether the raft will be a solid infill covering the entire outer profile of the part.
The main complaint here is not wasted resin - these large rafts can actually damage the printer, because the suction is so great that the slide mechanism skips - with incredibly loud thunks, and jerking resin trays - which will cause undue wear on the slide drive belt and cog.
It may sound bad but I don’t think it damages the printer. I’ve run numerous prints that nearly filled the build plate with no apparent issues or wear on my Form2 (after 291 prints and 14.8 liters of resin)
@Steven_Hines I’m not sure you’ve experienced the same thing despite your large prints. I’m not talking about a thunk as the build platform lifts off the resin tray surface. I’m talking “clutch-slipping” during the sideways slide - which get’s stuck - and there’s up to half a dozen repeated slips - each making a loud thunk and jerking the resin tray before the slide will complete.
That means the slide drive belt is slipping over the teeth of the slide drive cog - and that is never good.
One point I haven’t mentioned before is that I’m using the new LT resin tray - which might be difference between your large prints and mine…
Actually - thinking back to 2016 I did loads of prints with rafts this big without a problem - so yeah - it probably only becomes a major issue once you switch the LT - and I think we will all be switching. Assuming the 20x lifetime claim is accurate - which seems to be the case so far - there’s not even the slightest trace of clouding on mine after several litres of prints. In fact I would not be surprised if FL discontinues the standard trays once they’ve ramped up LT production.
@Stephen - ok so you’re using LT too. How much of that 291-prints/14-Litres was on the LT and how many was of prints with rafts that cover the build plate?
Not sure how relevant my question is though, assuming you’ve run at least one such large raft print in an LT, since this happened to me on the first and only large raft print I ran in my LT tray. I’ve been very careful to make sure rafts are smaller since.
As to whether something else is going on - seems like a reasonable question - although everything is running fine with smaller rafts. I’m hacking the parts to make a “bald patch” for a support gap, so that I can get the hollow raft - and the part prints fine… albeit with a little distortion around the bald patch.
Admittedly not many of my prints were done with LT tanks. Looking through my history I have a few that were large rafts but nothing that looks like it covers as much as your example here. I’m wondering if something about the peel process for LT tanks is more aggressive (if it’s assuming parts don’t stick) and that’s causing the problems you’re seeing?
It’s not automated but you can manually edit the supports to eliminate the solid rafts. Just edit the supports and make an empty space (start with maybe 5mm or so) for the software to see as an opening. Once the gap is large enough you’ll have an empty center in the base.
I’ve done a few mold prints directly on the build plate with the new LT tank and haven’t seen this issue. Might be a good idea to reach out to Formlabs support for some tuning tips.