Strange outside wall artifacts.

[Pridanc 4]

Folks, after printing several of this part without issue, today I wake up to a print that is more than useable (and will be) but has some strange visible artifacts that end suddenly at a certain height.  I'm no longer a newbie but have no idea what might have caused this?  I just want to avoid this in the future but hard to do if I've no clue why this happened in the first place. 

 

ABS on an Ender 3V2 converted to simple DD using all the original Ender extruder bits moved on top of the Ender Spyder hotend.  This is printed in an enclosure and I had no warping etc. 

 

Couple of pictures. Notice how it all ends at the same height?  

 

I look forward to hearing anyone's thoughts.  

[Slashee_the_Cow 421]

If you could provide the .3mf file (File > Save Project in Cura) that always helps us sleuths.

 

I will offer one piece of advice which I'm told I offer too readily: if you used Cura 5.4, that has some known bugs when it comes to slicing, try slicing it Cura 5.3.1 (don't have to uninstall 5.4, you can run them side by side) and see if that makes a difference. Although this doesn't look like the sort of problems which usually come up with 5.4, so take that with a grain of salt if you want.

[Pridanc 4]

Slash, of course the one time I don't make a .3mf project file this happens.  So, here is an after the fact version. I did make an html "project file" for my records so I've been able to verify the slicer settings. No proof I've made this .3mf file 100% accurately but it is darned close.  

 

Only thing I don't see here is that the printer was in a chamber heated to 105F or 40c. I can make it hotter but this appears to work.  

 

Advice is what makes the world turn so never hesitate to give any and all to me. 

 

BTW, is it possible that this behavior is from under-extrusion by the filament getting temporarily stuck on the spool?   I'm going to a dual gear extruder, just because I have one, but perhaps all my el-cheapo equipment somehow caused this?

 

Please understand, I don't know under-extrude from over-extrude so the use of those words is just me grasping.  Yes I know what the words mean but visually?  I know very little.

Sad, I know. :-)

 

TYVM, PDC

Steve 88.3mf

[Slashee_the_Cow 421]

11 hours ago, Pridanc said:

BTW, is it possible that this behavior is from under-extrusion by the filament getting temporarily stuck on the spool?   I'm going to a dual gear extruder, just because I have one, but perhaps all my el-cheapo equipment somehow caused this?

To my (somewhat) trained eye, that's definitely possible. In your second photo, see how instead of straight lines (in the good spots) there's a lot of bits that look like it got a bit of filament and pulled it instead of smoothly coming out? That could be underextrusion - the printer isn't extruding as much as it should, and if it's having trouble pulling more filament in as it needs it then the pressure in the nozzle will definitely drop, and it needs enough pressure to actually spit out filament. And if your filament is only getting stuck at certain parts (how does filament get stuck on a spool, anyway?) that would explain why most of it is fine.

 

What extruder are you using now? I've never had a problem with the Bowden extruder that came with my Ender-3 v2 Neo... though I've only had it a couple of months, so too early to properly call it. If you're using a Bowden extruder, your Retraction Distance setting is way too low (given how much filament is in the tube to the hot end, you do need to pull back a bit) and your Retraction Speed is too high.

 

Also, one thing I've definitely found messing around with 3D printers - if it ain't broke, don't fix it. Don't use a different extruder just because you have one (whereas if your extruder is broken and you have another one - quite convenient).

 

Some suggestions I can offer without messing with extruders (hardware):

• Use a smaller nozzle - yes, it'll take longer to print, but it also reduces the flow rate of filament required, so it's easier for an extruder to keep up.
• Are you printing PLA or did you forget to change that in the profile? Cause I've never seen PLA printed anywhere near that hot.
• In the print settings, you could try turning up Material > Flow > Outer Wall Flow just a smidge (I'd guesstimate about 105%). This will give the printer a little more filament when printing the outer walls, which could help it keep up with the lines it needs to do (or fill any gaps, etc.). You definitely don't want to overdo that one or it'll result in overextrusion (the printer is pushing out more filament than it needs for that feature - can lead to blobs and stringing).

Or of course it could have nothing to do with extrusion. But that would be my first guess based on the pictures (much as I don't want to have surface problems, I can't wait for the moment I do, cause it gives me an excuse to break out my macro lens).

[Pridanc 4]

Slash,

Lots of great questions.

First is yes, I forgot to change the words as the part is ABS and in an enclosure and printed with a .4nzl.

 

Retraction tests actually want me to between  .8mm and 1mm on my DD extruder and I float between .8 and 2mm to see if there is a difference. I've never seen any.   A Bowden machine needs a much longer retraction setting do to the flex, flop, and compressible nature of all that makes up the Bowden mechanism.  When using Bowden my machine loves 5-6 on PLA and ABS but wanted 10-12mm on the flexibles I've used. 

 

I've also been floating between 35mms and 45mms retraction speeds. I've seen nothing visible to point that I should use one speed over the others

 

Next, filament can get tangled on the spool as it moves around being pulled and pushed as the extruder does its thing.  When slack gets into the spool, filament can get under other "lines" of filament and then get stuck and can slow the feed enough to be an issue and can even outright stop the feed.  I can only point to this as a fact one time. I can not say that this sticking happened this time.  That one for sure time, the extruder pulled so hard it yanked the spool off its holder and if memory serves broke part of the x-z carriage.  Boggles the mind. Although I have a camera watching the prints, I don't record them unless I feel there might be an issue.  I know....sad huh?

 

So my "is it possible" is just a pure guess but it makes me curious and that the print cleared up 100% at the exact line all the way around the print from that point on?  Even more curious as this could have been filament feeding normally from that point on.  Makes me want to get a filament sensor to monitor avg movement.  Not as yet with printing, but I've been in a place where we recorded everything so I'm use to such silliness.

 

The dual gear extruder is what was on my machine when I got it. (used, $109).   Someone had replaced the stock plastic one-driven gear/idler extruder that comes with the Ender3 v2 to an aluminum dual driven gear extruder and it was perfect.  Along the way I ended up with a similar looking aluminum extruder but one that is closer to the original Ender that has only one driven roller wheel and one idler wheel which presses the filament into the driven roller. 

 

This single driven wheel extruder is being used now only because the printed part I have to mount the Ender extruder motor on the hotend (to make it a DD extruder if you will) did not have the correct offset to use my dual drive extruder.  That is being rectified.

 

My personal experience has been better with the dual gear extruder so I will go back to what I know. Right or wrong, I figure that if there is some resistance with the filament spool, the single driven wheel extruder might lack pulling force as compared to the dual driven wheel extruder.  I do not have any actual proof of this beyond my gut.  Maybe I'll rig up a test stand.  :-)

 

Your words are very well taken. The machine was a good old Bowden tube essentially stock Ender 3v2 and did an admirable job, that is, until I started to print with flexibles.  Some times it was still perfect, other times not so much.

 

Hard as it may be to fathom but yes, I actually do follow the "if it ain't broke, don't fix it"  credo. However, and here is where my weakness comes in, I love to freak with stuff but the overriding goal for me here is to have a machine that can print most any material without any concerns or changes needed beyond the slicer settings. 

 

While I have you here, is Z hop needed?  I'm also a  "if not needed, don't do it" kind of person.

 

As many of these boxes as I've printed out of ABS, it is the first to have any external surface flaws.

 

Now, for practice, off to print more boxes trying your flow suggestions etc.  See? I'm a gluten for punishment.  

 

HUGE thanks for your input and thoughts as it is the only way I will figure this out.

Stay well, PDC

[Slashee_the_Cow 421]

13 minutes ago, Pridanc said:

While I have you here, is Z hop needed?  I'm also a  "if not needed, don't do it" kind of person.

I've never needed to use a Z hop. It won't make a difference here. It's only really necessary if your nozzle always runs into stuff or your extruder isn't retracting properly (in which case a Z hop would make it leave stringy stuff more than actual plastic on plastic). It does also put more wear on the motor and mechanical components of the Z axis gantry since it's moving a lot, instead of just once a layer.

 

19 minutes ago, Pridanc said:

See? I'm a gluten for punishment.

The term you're looking for is "glutton", so based on what you said I'm hoping you don't have celiac disease.

[Pridanc 4]

Slash....LOL over the glutton gluten thing. I'm betting I chose it after leaving a T out of the first word and missed that. I'm such a dork.  C'est la vie.

 

Z hop is one of those that seem to be on by default. I'll deselect it and watch what may happen using your words as a guide just in case. 

 

Stay well and again, TYVM for your help and words.

Onward and upward,  PDC