Jump to content
Ultimaker Community of 3D Printing Experts

UM2 retracts after print way too far


Recommended Posts

Posted · UM2 retracts after print way too far

Hi,

I noticed that after a finished print the filament is retracted quite a bit. This is actually a problem because the filament is transported very far up, past the teflon piece. On the next print, the filament is pushed down again, through the teflon piece. This will certainly lead to increased wear because the filament tip tends to form a significant buldge which is squished through the teflon for every print.

retraction before print

filament Tip with buldge

Depending on the reason why the filament tip forms such a buldge or how pronounced it is, this might explain the underextrusion problems of some users where the teflon piece gets deformed.

What do you think?

Tested with firmware 14.09.

 

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    I've noticed the extreme retraction as well. I've noticed myself checking more and more lately on the beginning layer of prints to make sure the nozzle is sufficiently primed, and the first layer is going down fine. I'm having to do this becasue there are times where it just doesn't prime enough, or for whatever reason the filament binds in the hotend/teflon, causing a jam. I used to be able to just hit print and walk away. Not 100% sure it's this long retraction, but it's definitely a strong candidate for being the culprit.

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    By the way, why does it have to retract at all?

     

    Not sure but maybe "filament change" wouldn't work if you didn't retract?

    I wish it would wait until temp is 100C and then do a "cold pull".

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    @Nicolinux: If someone is printing very hot it might drop onto the finished print -> not funny. But a standard retraction would be enough IMHO.

    @gr5: Thought of that too. But does the motor have the strength to do a cold pull or would it just result in skipping?

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Hm, right after the print, the bed moves down a bit (but fast) and then the head moves to the side. I don't think there would be a big chance of excess filament falling down. And even if, this lil strand of filament would be no problem to remove. I think teflon piece wear is by far more serious than that.

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Yeah I have the same issue.

    Its not for change material because the process heat the nozzle before retracting it.

    It might just be to prevent materials to burn in the hot nozzle like it can happen for woodfill.

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Yep - it's to keep PLA from baking onto the nozzle while it cools down, and so you can more easily switch filament between prints.

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    But are you happy with the status quo? The prospect of the filament bulge passing through the teflon piece every time isn't something I'd would trade. I mean, this retraction after print is a somewhat recent change if I remember correctly (since 14.x). Even if PLA bakes onto the nozzle, the next time it is heated up it will soften again so it can be pulled out easily.

    I'd love to hear Daid's thoughts about it.

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    I agree with you Nico i think i sometimes have problems with that retraction as you said it can probably damage the Teflon, i had one or twice the filament stuck in the Teflon because it was too expanded.

    I had to remove the filament by taking the Bowden off like in the Atomic procedure to get it out (was to hard to pull out from the feeder).

    But indeed for things like woodfill it's probably a very good thing, anyway i would recommend cleaning the nozzle after every woodfill or bronzefill print to prevent blockage. Maybe it could be a parameter of the material?

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Maybe it could be a parameter of the material?

     

    +1 :)

    Is it retracting when aborting a print? I don't have the impression it does (I'm not home to test it).

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    +1 :)

    Is it retracting when aborting a print? I don't have the impression it does (I'm not home to test it).

     

    It does in later firmware versions.

    The idea of this retraction is to remove the filament from the hot-zone so it does not degrade while the hotend is cooling down. And heat from the hotend "creeps" up trough the filament melting more filament inside the teflon, causing problems there.

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Could it be a good idea to keep pushing some filament out while starting to cool down (at least a few degrees) and then retract? It could prevent the blockage in the teflon like it does now.

    I can already see cases where that would potentially grind the filament :(

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    The feeder motor is impressively strong. Mine pulls 5kg. That should be enough for a cold pull. Then if you change colors later you don't have to wait for the color to change. It changes instantly.

    http://umforum.ultimaker.com/index.php?/topic/4222-pulling-force-of-um-extruder/?p=34887

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Daid: It seems like it would be good idea to have the fans run for a minute after Abort or Ending a print, to reduce that heat soak from the still-hot hotend (and from pulling the hot filament up into the spacer).

     

  • Link to post
    Share on other sites
    Posted · UM2 retracts after print way too far

    Same problem for me.

    Is there a way to change the retract lenght after print?

  • 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

      • Talking additive | The 3D printing podcast
        Why should we be the only ones asking questions? Join us and ask Jabil all your questions on September 22nd 5pm CET
          • Like
        • 3 replies
      • Ultimaker masterclass: Optimizing your Ultimaker Cura workflow
        Save your seat for either broadcast on September 23.
        What will you learn?
        · Best practices for iterative print preparation and every lesson you should learn from each print
        · The right way to use per-object settings and when they are most useful
        · Easy-to-use resources for anyone who wants to develop their own printer definitions, plugins, or print profiles
        · How to optimize print profile settings and whether to “keep” or “discard” changes
        · When is the right time to export your drawing from CAD? (Based on Ultimaker Cura’s surprising power as 3D control software)
        · And a whole lot more tips and tricks!
         
        How can I join?
        This free masterclass will take place twice:
        1. 11am CEST (5pm SGT, 5am EDT)
        2. 5pm CEST (11am EDT, 8am PDT, 11pm SGT)
          • Like
        • 0 replies
      • Do you use 3D printing at work? Let us know
        It doesn't matter if you are using 1 Ultimaker or 10, there is inspiration in everything. We're looking for ...
        • 1 reply
    ×
    ×
    • Create New...