Issue printing ABS first layer UM2+

[LloydXmas 0]

Hi all. I'm new in the world of 3D printing and I could really use some advice/help with my UM2+ . I'm having problems with a 0.6mm nozzle on the first layer of ABS (Ultimaker brand). I've tried adjusting numerous things:

 

• re-leveling the glass surface
  
• adjusting the print temperature, everything from 215 to 240
  
• adjusting layer heights starting at 0.15mm and up to 0.25mm
  
• I read somewhere to adjust the Retraction Minimum Travel (I've lowered it to 0.5mm to no avail)
  
• I've played around with retraction distance and speeds too
  
• print speed currently at 40mm/s and travel 120mm/s, i've tried going down to 35mm/s print speed
  

 

I'm using Wolfbite's ABS formula (I've also used the glue stick) but adhesion doesn't seem to be an issue.

Am I missing something really obvious here? Again, I'm new at this so I'm hoping there is something simple that I just haven't set correctly. Any help would be greatly appreciated, thanks!

Also, is the nozzle supposed to look this dirty?? I've done about 8 prints with this nozzle, however they were 7-10 hour prints.

[gr5 897]

You never said what the problem is. Your bottom layer looks textbook perfect. However I'm going to have to guess you don't like those lines between the holes. Those are non-printing moves that have no retraction. Is this what you are talking about?

To get the printer to retract during infill like that (the slicer thinks of this as infill) you have to turn off combing. Combing is a feature where it tries to do non printing moves within infill and as a side effect it doesn't bother retracting as it's (wrongly) assuming this layer isn't visible.

Then on top of that - there might also be a "combing on first layer" option or something like that. So make sure you found all the combing related options and disable them all.

[LloydXmas 0]

Thanks that was exactly my question/issue: combing. The prints look great on the bottom now with combing disabled. I have one further question for anyone that may be able to answer. What is causing this to occur on some of my prints? (see circle on image) I'm guessing it may be a piece of ABS from nozzle build-up that comes loose during printing but I don't know.

[gr5 897]

That's strange. I'm guessing it's the initial bottom layer blob? Because even the bottom most layer (I assume this is upside-down) has the problem.

At any rate you are getting some over cooked ABS turned brown there. What temp are you printing at? I don't like to go over 240C as ABS can get cooked into a gunky gum if you don't get it through the nozzle fast enough (a few minutes). But printing as cool as 240C means I need almost zero fan or layer bonding isn't great. ABS is tricky.