Jump to content
Ultimaker Community of 3D Printing Experts

Print problem with PLA

Recommended Posts



I'm new to 3D printing. I use a ultimaker 3 extended, with PLA and PVA in combination.

After printing i noticed there are small bubbles / lines at the positions / lines where the print head of PLA is moving.

What is my problem with this print and how can I solve it?

Thank you in advance.


Problem 2.jpg


Share this post

Link to post
Share on other sites

Wow.  Nice print. Everytime I think I've seen everything I see something very different that people do with 3d printers.


The two features you want to experiment with are "z hop when retracted" and "combing mode".


In the first place I'm surprised this happens at all - by default combing is enabled which means it should not ever hop over those gaps and instead should stay within the thin walls when moving to another location to print.  Maybe it can't do that though - because maybe the center area is hollow underneath.


So the alternative is to enable the z-hop thing and maybe (probably not) also disable combing.  Because it doesn't retract when doing a combing move so it might not be retracting when making those "lines".  But I doubt it.  Probably you can leave combing alone.


You probably want to use the horizontal slider in layer mode to see if the head is moving up every time.


In addition you might have to play with retraction settings.  You are printing very little between when retractions need to happen so maybe one of the retraction settins is occasionally preventing retraction:

minimum retraction travel (set to 0 to make it always retract)

maximum retraction count (set to 1000 to make it always retract)


Note that these last two are a bit dangerous and can cause your filament to grind to dust if there are too many retractions.  So I would set these back to normal for any other print than this.

  • Like 1
  • Thanks 1

Share this post

Link to post
Share on other sites

Dear gr5, 


thank you a lot for your fast reply. Following your ideas I have tried to fix my  issue with the help of your tips.

The use of always-retraction ended up in a mess and the print looked that ugly during the print process, that i aborted it. 

z-Hoping was always activated during my prints. 


These  blobs of PLA appear to happen at the position where the print head moves, the travelling paths.

The diagonal lines in the objects are 1 mm thick. 

My latest idea was to change the size of width of the lines from 0,35 mm to 0,37 mm, as that resulted in less blue travelling lines in the slider view.

I can post my result on monday. Would it help if i uploaded the .stl file, or the cura file?


Thank you for your help, its really appreciated.




Share this post

Link to post
Share on other sites

I just noticed something else. 

The diagonal rectangles have a width of 1 mm. The printed printed them with 0,35 mm of line width which results in 2 lines and infill mess.

Now I played around with the line width in Cura and set it to 0.33 mm which fits 3 times into 1 mm and a bit of space. Which seems okay.

I will test print it on monday. I have a 0.4 AA printcore of PLA and 0.4 BB printcore for PVA. Maybe it works!?

  • Like 1

Share this post

Link to post
Share on other sites

I"m a bit confused because the "Z hop when retracted" should have taken care of the problem.  I thought.  I guess it fixes most of them but occasionally it doesn't retract (if it retracts too much it can grind the filament).


Another solution might be to increase retractions (always retract) and I know you got ground up filament and a failed print but you could lower the print speed by X2 to reduce the pressure and reduce how hard the feeder has to work.  Then loosen the feeder all the way to the top position (weakest squeezing of filament).

Share this post

Link to post
Share on other sites



i have been tweaking a lot, and finally found a solution that solved my problem. I changed the line width from 0.35 to 0.3 and now I don't have these problems anymore. The print looks really fine. What also helped was the change of "z-hop when retracted" from 2 mm to 4 mm. These travel moves, which caused the entire problem, do not occure anymore.

I guess the whole problem was, that my 1 mm diagonal lines did not allow 3 full 0.35 mm walls to be printed. So the printer tried to fill space, where walls do not fit. I solved it only by passing by this problem with printing thinner lines. What happily works. Its more or less a work around, i think.

I have saved my printing profile now for that this does not happen anymore in the future.

The whole thing helped a lot to get more into 3dprinting.


Now i only have some PVA doesnt always perfectly stick in the first layer problem, so that the rest of the print would be ruined and i have to watch in the beginning.


I sometimes catch and hold back the big pva blob before its moved around by sticking with the printing core and from time to time i get the message, that print cores do exceed realistic values. After some leveling it worked, and i am ok with the results, not knowing where i could improve much more right now.


Thank you gr5, for your help.


Share this post

Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Our picks

    • Ultimaker Cura | a new interface
      We're not only trying to always make Ultimaker Cura better with the usual new features and improvements we build, but we're also trying to make it more pleasant to operate. The interface was the focus for the upcoming release, from which we would already like to present you the first glance. 
        • Like
      • 79 replies
    • "Back To The Future" using Generative Design & Investment Casting
      Designing for light-weight parts is becoming more important, and I’m a firm believer in the need to produce lighter weight, less over-engineered parts for the future. This is for sustainability reasons because we need to be using less raw materials and, in things like transportation, it impacts the energy usage of the product during it’s service life.
        • Like
      • 12 replies

Important Information

Welcome to the Ultimaker Community of 3D printing experts. Visit the following links to read more about our Terms of Use or our Privacy Policy. Thank you!