Misbehaving print of small ABS part.

[Pridanc 4]

OK, y'all know I'm often confused but today? More so than ever. 

 

Never forget I'm a small time printer but still do it several times a week so more than zero right?  After a typical successful run of parts, I needed to switch over to some ABS and this is what happened.  What The Heck?

 

All my filament lives in a box that keeps the humidity around 18% day in and day out. Add to that I placed the ABS filament into a typical drying box for 4 hours, acknowledging that ABS usually needs a longer bake, but the point is that the filament lives in a relatively dry place prior to my tossing the roll into a dry box to top it off.

 

This part is small at a little over 30mm long depending on how you measure it, and say 11mm thick.

 

First oddity can be seen on the top surface (where you see a place for a steel nut) that has blister bumps!  Next, the lowest first few layers, the ones coming up from the bed, are way confused leaving the whole piece misshapen and useless.

 

Below please find a few pictures along with the .3mf file.  I'm using CURA 5.8.0

 

As I type, I've chosen to start a print 2 of these parts at once in an effort to see if layer time/heat is an issue. I've also ditched the Tree growing out of the bed to support the gap. Maybe that tree trunk causes the rest of the print to be freaked up?  I'm reaching here.

 

The settings seen here are ones I've used with this very ABS previously with great success. Lucky I guess. I can say that the other parts were considerably larger in size.

Let me know any thoughts as I'm happy to make changes. These are those days that can be discouraging. 

DR-013 Lock reva.3mf

[GregValiant 1,409]

People will disagree with me on this but I will not be dissuaded.

Your first image shows pressure in the infill void pushing up the soft plastic.  Filament dryer or not, that's a moisture issue.

Do you have another roll of ABS you can try?

You might try the "Advanced Cooling Fan Control" post-processor.  You can set it to "By Feature" and turn the fan off for everything except those top skins.  Rapidly cooling the skins over the infill might keep the pressure from developing, and the skins would cool faster and hold their shape/position.

I looked at the settings and they look normal.  With the bed above the boiling point of water, and the fact that the model is so short, the bed heat can be affecting the situation as it drives the moisture from the bottom skins upward.

I'd set the fan up like this.  I set the Skin Fan Speed to 100%.  You can of course use whatever you want.

The fan will come on for Skins only starting with layer 89 and keeping that up until the print ends.  It's a small part so there will be some lag time between the fan being told to turn on, and it coming up to speed, and then some slow down time when it turns off.

 

[Slashee_the_Cow 479]

1 hour ago, GregValiant said:

Your first image shows pressure in the infill void pushing up the soft plastic.  Filament dryer or not, that's a moisture issue.

Using Cubic infill (good thing👍) you could also try increasing the infill density to make any pockets of air that might form smaller.

I'm not going to argue with @GregValiant since there are far too many times I'm sure I'm right and people doubt me and I turn out being right that when he's this sure, it'll probably turn out that he's right 🙂

Other than that if you've had good luck printing ABS so far, nice 😉 It took me apparently me 0.4 prints with ABS before I started having problems.

[Pridanc 4]

Gents, 

Huge thanks as always. I will purchase another roll of ABS just to see what the heck. Can't lose because a) moisture is the issue and I can then really dry the other roll and  b) if not I will use the roll someday so not wasted money.

 

Whilst y'all were considering my plight, I ran off two at once to see if heat was an issue. Best answer is maybe as both of these two parts are usable.  Saddest thing is that for some silly reason I flipped the prints so that the visible side of the part would be shiny (from the bed surface)   Arrggg.  That shiny side needed to be the other side than how I oriented it.  Hmm, I'm probably old enough that Sundowners had set in early after noon.  

 

Anyway, see the picts below. Meanwhile, what are your thoughts on why the first one (above picts) look so awful as the print rises off the build plate?  Mentally I always say "too much heat" but have no reason to say that to myself especially when ABS isn't generally a fan of ...fans.    Part of my frustration in all of this is my inability to look at something, like what we speak of here, and say unequivocally "Oh, too much XXX, or not enough YYY" as an example. I just sit back totally lost.

 

 I will, as stated above, change filament and continue to mess with the temps and cooling by levels. These last two are danged close to usable as they are. 

 

Any more thoughts, please share them with me.

You so rock, TY

[LePaul 354]

Are you using an actual filament dryer, that allows you to set the drying temp and duration?  Or are you placing your material in with a bunch of desiccant and hoping for the best?

 

I ask because many miss the point of the filament dryer - heating the material to release the moisture from the filament.

 

Just curious!

 

[Pridanc 4]

Hey LePaul,

Great question but yes, an actual filament dryer. 

[Pridanc 4]

Alright, I'm back with the latest results along with the .3mf file.

IMO a couple of issues that seemed to cure themselves by simply printing this part by a pair all at once. If you look at the first pictures notice how the layers coming off the bed absolutely stink. I think this is heat related but do not quote me. However this is why I chose to print in pairs. 

 

Next, I've lowered the bed temp a bit, as well as I suddenly decided to look at my notes on the ABS filament I use and missed the retract distance and speed. Do I know how this might affect it? Nope but the retract went to the default of my ancient old machine which was a Bowden fed device but long since converted to DD. Thus, less retract is typically used.

 

And, drum roll, I chose to follow the cooling fan by layers suggested by the wizards here. Check out the results. These pictures are as the parts were literally just pulled off the build plate. Nothing has been done much less any of the support material removed.

 

These parts are very small so picts are very enlarged.  To anyone's naked eye from any distance (say a foot or more) these parts are perfect. For our use, without question 100% on the money.

 

To all of use worried about moisture, could be as my new filament has not arrived but I baked this ABS for another 7 hours prior to this last print. Did that do the trick? Could well be as there are no bubbles coming out of the top layers. The top is the side with the well for a metal nut to be dropped into.  So lets say that perhaps we are looking at a combo of drier filament and the fan-by-layer script with me leaning towards the fan-by-layer as the winner.

Regardless, this is a huge success IMO and want to thank the great folks who are always here to help on the CURA forum... once again  :-)

 

All the best, no onward and upward!