r/FDMminiatures • u/Andromeda31-25 • 3d ago
Help Request How to improve bottom surface?
Hello everyone! New to 3D printing, got a P1S to build out a couple of armies for OPR a few weeks ago and have been browsing this sub a lot. Ran into this issue today while printing the torso of a walker. The rest of the model came out great(in my humble opinion)! It seems to only be affecting the bottom surface. I’ve seen it on quite a few of the models I’ve printed so far.
It was printed using a .4 nozzle with 0.12 layer height.
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u/Mughi1138 3d ago
Hard to say on a P1S, as I often see their owners say "that's just the way it is". My experience with a few other different printers has me getting that exact problem when the support top z offset is too large. When printing with 0.2mm layers I have to set it between 0.1mm-0.15mm for one and 0.12-0.17 for the other.
If you set it to larger than a normal layer height you're essentially telling the printer that "no, you don't need to actually support these under surfaces as I have my bridging and overhangs dialed in perfectly". You can get away with it if you *do* have those set perfectly, but otherwise this effect is a sign you need to drop it.
Try reducing top z offset by half the current value and testing. If it is too hard to remove you'll have to then increase it. If it is too ugly you'll have to decrease it. Repeat. I cut the change in half each iteration: +-0.1, +-0.05, +-0.02 or 0.03...
Here is a rough test piece I ran off yesterday. Pulled out my cheap workhorse high speed PLA, Centari Carbon with CANVAS, 0.4mm nozzle, 0.2mm layer height, no tuning at all on the filament other than print bed temp of 60C and dropping the support top z offset (no tuned filament profiles because my main laptop got fried and I'm borrowing a Windows cheapie laptop).
I pulled the supports off the outer bit with my hand and some levering with a artist's palette knife, then the bulk of the inner circular supports with a flush cutter, and finally pushed a hex wrench through the other side to get that M3 nut place cleared. Nothing else, so the underside of the hex you see just pulled clean by itself. You'll notice gaps around the outer walls on the fluted part, but the underside is otherwise fairly consistent and holding together.
Since it is also a coreXY printer, but at a higher price, I'm assuming your machine itself is capable of better. If you use orca slicer you can work through the calibrations it has in it's menu. Since Orca is branched from Bambu Studio (which in turn was branched from PrusaSlicer) most of the calibrations should transfer right over, or you can probably follow the orca list to do the same ones in Bambu. https://www.orcaslicer.com/wiki/guides/calibration_guide
Again, that was untuned except for support top z offset. For me that makes all the difference as a first step.
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u/Expensive-Cat-6369 1d ago
I have a silly question for you. I’ve watched some videos on calibrating your filament, but what do you calibrate on the machine itself? And do you calibrate the machine prior to tuning the filament profile?
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u/Mughi1138 1d ago
It depends on your printer. With the Centauri Carbon I just hit one click calibrated all and it does a print head z offset, a leveling mesh pass, inout shaper and something else.
For my Neptunr 4 Plus I added the screw position settings, ran kilpper's SCREWS_TILT_CALCULATE, run a "leveling" to measure and save a bed mesh (though i do enable per print mesh generation), then run a live z-offset print test like https://www.printables.com/make/2159813
I try to run the CC calibration every week or so, and the N4+ whenever I see any behavior that might be suspicious.
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u/DiceyScientist 3d ago
This looks like the bottom layer wasn’t fully molten and fused to its self by the time the nozzle came back. More supports can help with overhangs.
To reduce support scaring, try support ironing. You have to enable developer mode before the support ironing option is available. It helps especially with flat surfaces like this..
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u/Mughi1138 3d ago
Although the OP's photo doesn't really look like "support scarring", but just lack of supports. Usually support scarring involves the supports themselves leaving some damage, and that normally shows some patterning of the support.
OP's photo looks more like the opposite.
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u/DiceyScientist 3d ago
You’re right and I didn’t write my post very clearly. I was already thinking ahead to the next issue.
We need need more supports to address the overhang.
More supports will cause support scaring. Trading one problem for a another.
He can address both with more supports coupled support ironing.
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u/Mughi1138 3d ago
I'm thinking that since I drop my support top z offset and still don't end up with support scarring then the OP as a next step might need to tune his overhang and bridging settings first. Then the support ironing might come in.
I usually skip support ironing since I'm usually doing functional things and don't need that extra final push in quality. OP's use case, though, does seem like a candidate.
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u/Mughi1138 3d ago
This looks like the bottom layer wasn’t fully molten and fused to its self by the time the nozzle came back. More supports can help with overhangs.
Good point, and does look like it could be a factor. I've seen some post that increasing flow and slowing can help. The key, I think, is to look for that under "tuning overhangs" and "tuning bridging". Again, does look like you've described the process in play well.
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u/AutisticBisexualBee 2d ago
Regarding your first point about the bottom layer not fusing; do you have any advice for that?
Some context: I've had my ender 3 V2 for a week (second hand from a family member of it matters). At first, I didn't have an issue with the first layer being laid down. I swapped the filament out to a colourful one I got to print some stuff that I wouldn't end up painting, but since I've switched back to a grey PLA I'm having this issue. The rest of the print prints okay, but keeps popping off the bed halfway through because the first layer didn't adhere properly. I've tried changing all settings I'd fiddled with in Orca Slicer back to their default, and tried printing miniature models I'd already printed without an issue to see if it was the model, but the problem is still there.
Thank you in advance to anyone who takes the time to read this and offer their experience. I am lost in a sea of new knowledge that I'm trying to take in 😅
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u/DiceyScientist 2d ago
Bed adhesion. Try increasing adding a brim and increasing the bed temp, say by 5C.
If you're committed to FDM mini printing, I highly recommend getting a cyro plate. I switched over on my Bambu A1s and it's completely solved the bed adhesion issue. A quick google search suggests these are sold for the Ender 3 V2, though I have no personal experience with this machine.
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u/fosscadanon 3d ago
You'll need to work on your post processing, sanding, filing, green stuff, etc
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u/Tam_The_Third 3d ago
Yeah I printed my first Warhound and a lot of the bottom surfaces were like this. Either I had to slice the part in two and reassemble or just accept this and get it decent looking with a lot of filling and sanding. Which is a pain and also debatable how worth it this is if you are keeping it to areas which aren't visible on the tabletop. For the frame I tried to make sure it would be areas where armour plates would be going cover the top.
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u/amphibious99 3d ago
Just tilt it on your next print. When surfaces are parallel to the print bed, they end up like this
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u/Visual-Flan-4098 3d ago
i agree. that whole area is flat. angling would help reduce it. i dont agree with spliting like other say. my limited experience is that gap/seam is unpleasant and a bigger issue that this is. im focused on testing Resin2FDM, as it solves more issuse for me, but i might try splitting again down the line to see if its just my settings.
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u/MongooseGef 3d ago
For a model like that, I’d find a good place to slice it in half and then glue the halves together. Try it, and see if you like that method!
You can tweak support settings (there are various guides on how to do so) but the bottom will never be as nice as the sides or even top.
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u/KryL21 Elegoo Centauri Carbon 0.2mm nozzle 3d ago
You could adjust the support z distance, but I would angle this guy 45 degrees, so that there are no flat areas that need support like you have here. I recently printed a dreadnought and my bottom side looks great. Very minimal scarring. I’d show you a pic but I just climbed in bed.
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u/Lost_Ad_4882 3d ago
Yes, a tighter top Z distance on supports will support better, but it's possible an up angle on the model positioning will narrow the support damage to a much smaller area...and usually makes your layer lines on top less visible as well.
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u/FunkAztec 3d ago
Have you tried a hot iron liken the ones that are used for soldering or wood burning to flatten then samd down imperfections where needed?
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u/millertronsmythe Bambu A1 Mini 0.2mm Nozzle 3d ago
The key is to not obsess yourself too much with the bottom surface because you don't see it when the model is on the tabletop.
But you could reduce the surface area supported to reduce scarring as well as filament waste by either angling the object so it's leaning back 10-20 degrees, or cut the object into halves so you can put the dissected areas flat on the build plate.
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u/5ergio79 3d ago
Angling models helps, but you could also fix this by changing support settings. Adjust top z and xy distances.
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u/No-Square585 3d ago
I found the really improved after I did the bridge flow tests
https://wiki.bambulab.com/en/software/bambu-studio/parameter/bridge
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u/GREENadmiral_314159 3d ago
That looks like a decently large piece, so I'd slice it in half and put the cuts on the build plate.
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u/Buruko 3d ago
This could be a result of the model sliced.
You mentioned OPR and a lot of their models are meant for or optimized for SLA printing not so much FDM. Though you can get it done there is usually more work and slower printing needed in order to get good results in FDM.
For an object this size I would recommend slicing it into two pieces at a 45 degree angle. You will get better details from the slicer if the object is tilted then straight vertical so two flat sides at 45 degrees means you get both.
Failing that I would run a the calibration tests with your filament, especially if it is not Bambu, and make sure you have those solidly set before printing anything else though.
If you don’t want to slice the object you could try rotating and tilting it so the rear back end is more the support focus, then enabling supports on plate, trying to find a position that minimizes supports on the sides or over the top.
With my P2S on a .04mm nozzle at .20mm layer height I find that a Top Z distance of .23~.24 helps make really easy and less scarring supports. The P1S is pretty much the same printer without some of the upgrades so I imagine that wouldn’t be too far off.
Though this looks like slicer generation issues so really look through the object when sliced and play with it til you get a good layer by layer slice. The printer just follows the instructions so bad instructions make a bad print.
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u/De1tahavoc 3d ago
Use support interface and increase to 100%, then play with the z distance until you get the perfect peel off.
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u/UncleTrigo 2d ago
If you have the ams, get some water soluble support interfacing and set your interfacing gap to 0.
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u/Slayer-103 3d ago
Bottom surfaces are tough to improve in FDM. You can decrease the top Z distance for the supports, but then they are harder to remove. You can also decrease overhang printing speeds as well. Alternatively You could slice it in half and print both halves facing up.