Overhangs!

[claudermilk]

Overhangs are killing me right now. I'm making progress but am not quite there yet.

I'm working on tuning my V0.2 with a Revo 0.15mm nozzle and Polymaker PolyTerra PLA. After clearing a partial clog I have eliminated my severe underextrusion issues. Now I'm just down to poor overhang quality and a corner artifact. 

Here's a couple of shots of what I'm struggling with. As you can see there's some corner smearing on overhangs and that little divot on the corners--that's not the seam (it's actually the back left corner by the tail).

Nozzle is 0.15mm, layers are 0.08mm. Line widths are based on Ellis' PIF profile. Slicer is Orca 1.8.0b2. I have under Quality Detect overhang walls, Avoid crossing walls (@50%), and Extra perimeters on overhangs turned on. On Speed Slow down for overhangs is on, the rest off (I'll be experimenting with those settings).

PA and EM are tuned from the Ellis guide--you can see the top surface looks great. I've dropped tempts down to 190C which helped a lot.

My searches thus far haven't turned up questions on this specific flaw or any solution. I'm sure someone has run into this, so any insight as to how to resolve it is greatly appreciated.

[Penatr8tor]

I was having a terrible time with overhangs on my VzBoT. Fortunately, I have another printer that prints really nice over hangs with a lot less cooling capability. So I grabbed the "slow down for overhangs setting from my RatRig and loaded them in my VzBoT profile and whadiya know... Worked like a charm. I printed this Marvin (22mm tall) with a .4 nozzle. I mean not bad really, he's standing on a penny.

Here's the settings... Maybe give them a try, see what happens. FYI, My printers print overhangs slower than a turtle, but the results are hard to deny. IMO, Best to start really slow and speed up until the quality degrades into the unacceptable range.

 

 

[Penatr8tor]

I did another test because the Marvin was printed with CF PLA (Polymaker) and I thought that maybe the addition of a filler material would aid in overhang stability as the material is less likely to sag. I loaded up a CaliCat and reduced the size to 50% (height is 17.40mm) Same settings as I posted and FWIW... I'm letting the printer adjust speed in the "Cooling" tab of my filament properties.

Print time was on the order of ~10 minutes start to finish.

Here is the result. I have to say I'm really impressed with the VzBot. I keep getting pleasantly surprised.

 

 

[mvdveer]

To my shame - I have NEVER printed a Marvin or Calicut before, so I thought I would give it a try. These are my standard print settings across the board of all my Vorons:

Orca Slicer 1. 80 beta 2

Printed in E-Sun ABS Hotend 255C, Bed 105C, Chamber 40C Cooling 25% from layer 3 (ABS is what I mostly print with, and some ASA at times)

Calicat:

  

Marvin:

  

No clean up - fresh off the plate

Printed and sliced both on the same plate - print time 24 minutes.

Printed tham but don't know what I am looking for - is late - bed time - so will do some reading tomorrow on how to interpret these.

 

[claudermilk]

 Still not there yet. I've fiddled with setting, but I'm still getting smearing along the overhang on the tail and the corners on the head. With a 0.4mm nozzle and 0.2 layers I'm sure it will be fine--I've gotten beautiful prints with those. I am trying to get the tiny nozzle and 0.08 layers working. Almost there, except for this roadblock. I am looking as much for general things to look at for dealing with this issue as much as specific settings in Orca--I know virtually nobody else is as insane as I ma trying to get that tiny nozzle working.

The reason I'm tilting at this windmill is I want to use the V0 to print up wargaming miniatures like I posted earlier from the Trident. I'm finally priming one of those examples and it looks amazingly good next to injection molded miniatures.

[claudermilk]

After beating my head against the wall on this thing. I decided to try an experiment. My thinking goes, the calicat is all right angles with a perfect 45 degree overhang. That is where I see the problem. The pieces I will be mainly printing will be more organic forms mainly with curves and a few edges. So I grabbed a 28mm figure file and sliced it up. Printing is about 85% done as I type, and....it doesn't suck. The smaller parts already complete from what I can see actually look really promising. The main body looks good so far, too. I have some speed tuning to do on the tree support speeds (too fast, looks like lacy swiss cheese). I'm going from really frustrated to encouraged and a little excited. This cunning plan might just work.

[Penatr8tor]

In my testing I found there's a lot more to good overhangs than just the angle... Having min 3 perimeters creates a support structure behind the overhanging perimeter. 2 or less perimeters and it will sag if the angle is too steep. I also found that melt temperature plays a huge role... @claudermilk I would bet that if you left your settings the way they are and just dropped the nozzle temp 5-10 degrees... that Calicat would be close to perfect. Think Cake Frosting versus Honey. The hotter your melt... the lower the viscosity, the more it will sag on overhangs. Extrusion multiplier is another factor. 

[claudermilk]

Already on that. My 0.15 settings have 6 perimeters. I also dropped my PLA temps down to 190; I worry that going lower gets below being able to extrude at all. EM is set from the Ellis tuning. I suppose I could play with those more. 

[Penatr8tor]

I think the Ellis guide provides good basic tuning as it will get you close, but you'll still need to make those few adjustments to get the best quality possible. Every filament is a bit different as well. While most will perform similarly, some will work better for a given print or geometry where some will just print like crap no matter what you try. In addition, when printing really tiny stuff... small anomalies and little blobs here and there that are barely noticeable on a larger part become huge and unacceptable on small prints. So yeah, bottom line @claudermilk is that you've got a really tuff nut to crack there buddy. That said, everyone has that one spool or brand of filament that prints better than others. If it were me... I would try to reduce my chance of failure and start with that filament instead of fighting with something that doesn't print that well to begin with.

[mvdveer]

5 hours ago, Penatr8tor said:

I would try to reduce my chance of failure and start with that filament instead of fighting with something that doesn't print that well to begin with.

Very good advice. Had a roll of E-Sun ABS Max that just did not want to print well. Was not worth the frustration.

[claudermilk]

Yeah, I'm going to try a different filament to see if this spool has gone off. It's Polymaker Polyterra PLA. I have some Jessie PLA I can try. But first, I have to take the bed apart and troubleshoot that. I found that the whole thing is moving more than I think it should; that's won't help at all and might be the root of my constant struggle at zeroing and leveling the dang bed. Getting a decent first layer has gotten me to having to stop with the printer for a while before I defenestrate it.

I certainly know this is a tough one. I'm close enough to think it's possible, but it's pushing the capabilities of the technology to the max.

[YaaJ]

Just a question : what do you print first ? Inner or outer walls ? It does not appear in the screenshots. With Cura, printing overhangs with inner walls first makes a huge difference. (but never printed with nozzle < 0.3mm)

[claudermilk]

Inner. That's default in Superslicer, Prusa Slicer, Orca. There's no way they would work at all going outer first.

Still struggling with this thing. I eliminated one big problem I've been fighting. Turns out I mistakenly used M2x6 screws to mount the bed to hte carraiges. They were bottoming out just before actually locking the Kirigami part in place. I swapped to the correct M2x4 and now the bed is sloid like it's supposed to be. I'm surprised at how well the printer has done with that wobbly bed!

I tried an old spool of Jessie PLA, but that was an insta-fail. It's near the end of that spool, so I'll have to dry it before trying again. I'm now drying a brand new spool of Polyterra. I'm also going to try a 0.1 layer test and see if that makes an appreciable difference. I would hate to lose the vertical resolution, but it doesn't do any good if I can't print clean parts any more.

[atrushing]

Have you tried printing the figurines in ABS? It is a lot more forgiving on overhangs and I think it prints cleaner in general (aside from the smell of course..).

Good catch on the Kirigami, those types of problems can be very hard to find sometimes.

[claudermilk]

I've actually been thinking of giving that a try.  I have several spool ends of ABS floating around I could use to test--these figures are a bit under 2g of material each. 

Yeah, the bed wobbling all around.."Hm...this can't be right. It's not like Voron to leave something this way, so I must have done something wrong" Which as it turns out I had. Another PICNIC error (or more like ID10T).

[Penatr8tor]

Good to hear you found a problem and corrected it. While no one wants problems... the ones you can fix are exponentially better than the intermittent ones. That wobbly bed is probably 90% of your initial problem.

As for the Polyterra filament... I really like that filament; it's always printed really well for me and is one of my goto's. 

You'll get there Chris, it's just part of the process. 

[claudermilk]

Yeah, the bed was a huge issue, now it's to what I expected. Get the bed leveled and zeroed then click print and know it's going to lay down a nice first layer. "Ah that's what Steve and the others meant when they nonchalantly said 'I just level it and never touch it again'"

I tried some ABS, the end of a spool of Polymaker Polylite and it was ugly. It printed but the overhangs were worse. I'm putting on a fresh, just-dried spool of Polyterra and see if that helps any. Then it's back to detail tweaking. I'm also trying to orient the model to minimize overhang trouble spots as much as possible. As long as the tops and obviously visible sides end up acceptable it should be ok--it's mainly for 28mm figures to be used on a 4x8 wargaming table. So nobody is going to be sitting right next to them with a magnifying glass. I'm just being picky and trying to get the very best quality I can. I'm sure it's there, I just haven't found it yet.

[claudermilk]

Just a quick update on this. I've punted this project until after the holidays. The V0 is now pressed into production duty for small printed gifts. For that, I've swapped the Revo back to the 0.4 nozzle and running standard settings for 0.4 nozzle & 0.2 layers. It's back to printing beautiful, effortless overhangs. So as I suspected this is directly related to the tiny 0.15 nozzle and paper-thin (literally) 0.08 or 0.1 layers. I'm kind of wondering at this point if I need to boost cooling to get the filament hardening back up faster.

[claudermilk]

Now that the holidays are past, I'm resurrecting this fight. I've been poking & prodding at settings in Orca and I'm so close I can taste it. As a reminder, I am running the Revo 0.15 nozzle and am now running 0.05 layers. The material is Polymaker Polylite PLA which I'm running 190 first layer, 185 after that & 60 bed, 45 after that. Speeds are pretty good overall.

I am still getting a little bit of corner smear on the sharp corners. I see outer wall curling on overhangs and I'm pretty convinced that is the problem, so I want to try and solve that.

I always print inner then outer walls. I have Orca's slow for overhangs & slow for curled perimeters turned on (tried classic mode with no observable change). Speeds are 80%, 42% (stock Orca), 12%, 4% (half Orca's default). I have fans at 100% and changed the filament cooling overhang threshold to 0% to force it to 100%. 

I'm now running on the V0.2r1 LDO kit, so LDO's included 3010 blower fans on the normal V0.2 tool head. I have been looking at the Fabreeko Honeybadger fans with higher CFM as an option for additional cooling. I'm also considering finding a replacement tool head with more cooling if need be.

So I'm fishing for any ideas of settings tweaks I may have missed.

FYI, for the standard 0.4 nozzle and 0.2 layers the printer prints beautifully. I'm pushing the envelope chasing near-resin output.

[kingstar]

Have you tried the "Reverse on odd" feature in Orcaslicer? I've found that helps with some curling because the forces are in alternating directions.

[claudermilk]

I have not. I'll give that a go, thanks. I think part of my issue is I've been so deep in the weeds now that I'm probably missing something & need a different brain to provide suggestions like that.