Jump to content
UltiMaker Community of 3D Printing Experts

Flow of plastic stopping for a while after 2-3 layers.


rewolff
 Share

Recommended Posts

Posted · Flow of plastic stopping for a while after 2-3 layers.

We're trying to print some stuff, but after two or three layers the flow of plastic stops. It prints 2-4 layers of "mostly air" and then starts putting out the proper amount of plastic again.

I've added G-code to the "start G-code" window to start by extruding 20mm of plastic (at Z=20). Then move to the platform and deposit a nice "wall" of a few layers of plastic.

The wall looks mostly solid every time.

All this has made very little difference: it still stops extruding for a while during the actual build.

Oh. It is not something mechanical with the material feed mechanism. The stepper turns and the PLA moves into the machine just fine (at that point in the machine).

Suggestions?

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    Did you also put a G92 E0 after your extrusion code...?

    Your E values are absolute, does your extruder wheel runs reverse after your startup code...?

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    Have you tried raising the temperature? Could be that the first two layers are being printed with slightly hotter PLA and then it cools down, to recover later. This could be (but hopefully isn't) a classic bowden plug.

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    @technicality: I was informed I probably have a "bad" bowden tube, so I'm getting a new one. The prints are reasonable, and I wasn't informed how "bad" a "bad" bowden tube is. (I'm not expecting it to turn zombie on me....)

    (what's a classic bowden plug? Googling for that phrase gives hits like:

    )

    Yes, I've nulled the Extrusion position after extruding the "wall".

    I've found that I can prevent having to edit G-code manually by enabeling the skirt. So now I have 8 loops of plastic on the bottom layer around my object and I've eleminated the "possibly faulty" G-code that I manually wrote.

    I've tried getting skeinforge generated G-code to work. That was a big disaster. Absolutely nothing worked. I've given up and I'm back to slic3r.

    At what temp do you guys extrude PLA? First layer same temp?

    [update] Some more experimenting... I've written a program to generate the G-code for a "cup". Doing the bottom layers slow, speeding up for the higher layers. To get the flow going I draw a 160mm line around my object. This works reliable. I think the retractions influence the extruded material. I've written my own "write-the-G-code" program because I was anoyed at slic3r who generates blobs in my objects because he stops for changing layers. The stopping with extrusion means the solid PLA is pulled back, but the molten PLA keeps coming out. The result is at least blobs of extra material near the place where layers are changed. My program simply increments the layer and gets really nice results. (Just that the sides of the cup don't attach strongly enough to the base. :-( )

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    The classic bowden plug is when there is still a gap between the PEEK/brass and the bowden tube. Molten plastic will come up (because of backflow:

     

    ) and stick to the PEEK. Because the PEEK is much cooler than the brass, the PLA will also solidify. EVen more plastic comes up, sticking to the other cooled plastic and thereby creating a plug.

    With ABS there is no backflow.

    Edit: there are some other options for slicing. You can use Cura, which is a nice front-end for a (modified) skeinforge. It uses printrun to communicate with the machine. And some people are using KISSlicer which seems to generate top-notch results so far.

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.
    @technicality: I was informed I probably have a "bad" bowden tube, so I'm getting a new one. The prints are reasonable, and I wasn't informed how "bad" a "bad" bowden tube is. (I'm not expecting it to turn zombie on me....)

    (what's a classic bowden plug? Googling for that phrase gives hits like:

    )

     

    I just made this animation that explains the 'classic' bowden plug:

    http://wiki.ultimaker.com/images/Bowden_plug.gif

     

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    Is your bowden tube is one of the newer, wider ID PFA tubes?

    I'm having similar issues, and I wonder if it's to do with having the filament a little loose in the bowden tube. My kit came with one of the defective tubes and this replacement is pretty loose fitting.

  • Link to post
    Share on other sites

    Posted · Flow of plastic stopping for a while after 2-3 layers.

    Aaargh... We've fixed it. I don't remember what we changed to get it this way, but this hasn't happened for a few days now. Grrr. Sorry guys.

    I think switching to cura and printing a skirt has helped....

  • 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
     Share

    • Our picks

      • Here it is. The new UltiMaker S7
        The UltiMaker S7 is built on the success of the UltiMaker S5 and its design decisions were heavily based on feedback from customers.
         
         
        So what’s new?
        The obvious change is the S7’s height. It now includes an integrated Air Manager. This filters the exhaust air of every print and also improves build temperature stability. To further enclose the build chamber the S7 only has one magnetically latched door.
         
        The build stack has also been completely redesigned. A PEI-coated flexible steel build plate makes a big difference to productivity. Not only do you not need tools to pop a printed part off. But we also don’t recommend using or adhesion structures for UltiMaker materials (except PC, because...it’s PC). Along with that, 4 pins and 25 magnets make it easy to replace the flex plate perfectly – even with one hand.
         
        The re-engineered print head has an inductive sensor which reduces noise when probing the build plate. This effectively makes it much harder to not achieve a perfect first layer, improving overall print success. We also reversed the front fan direction (fewer plastic hairs, less maintenance), made the print core door magnets stronger, and add a sensor that helps avoid flooding.
         

         
        The UltiMaker S7 also includes quality of life improvements:
        Reliable bed tilt compensation (no more thumbscrews) 2.4 and 5 GHz Wi-Fi A 1080p camera (mounted higher for a better view) Compatibility with 280+ Marketplace materials Compatibility with S5 project files (no reslicing needed) And a whole lot more  
        Curious to see the S7 in action?
        We’re hosting a free tech demo on February 7.
        It will be live and you can ask any questions to our CTO, Miguel Calvo.
        Register here for the Webinar
          • Like
        • 10 replies
      • UltiMaker Cura 5.3.0-Alpha 🎄 Tree Support Spotlight 🎄
        Are you a fan of tree support, but dislike the removal process and the amount of filament it uses? Then we would like to invite you to try this special release of UltiMaker Cura. Brought to you by our special community contributor @thomasrahm
         
        We generated a special version of Cura 5.2 called 5.3.0 Alpha + Xmas. The only changes we introduced compared to UltiMaker Cura 5.2.1 are those which are needed for the new supports. So keep in mind, this is not a sneak peek for Cura 5.3 (there are some really cool new features coming up) but a spotlight release highlighting this new version of tree supports.  
          • Like
        • 16 replies
      • New here? Get ahead with a free onboarding course
        Hi,
         
        Often getting started is the most difficult part of any process. A good start sets you up for success and saves you time and energy that could be spent elsewhere. That is why we have a onboarding course ready for
        Ultimaker S5 Pro Bundle, Ultimaker S5, Ultimaker S3 Ultimaker 2+ Connect.   
        They're ready for you on the Ultimaker Academy platform. All you need to do to gain access is to register your product to gain free access. 
        Ready? Register your product here in just 60 seconds.
          • Like
        • 14 replies
    ×
    ×
    • Create New...