Jump to content

Square circles


Sorbue

Recommended Posts

Posted · Square circles

Hello everybody,

I'am making my first prints with my new UM original + and i am quite happy with the printing quality. However the circles i want to print are a bit square, as it can be seen on the next picture :

Trou.thumb.jpg.d7837e70092a98723b5371a722a51ca3.jpg

So i had a look at several tips and i :

 

  • Checked the belts tension
  • Checked the XY axis alignment

 

I also tried to print a 100m x 100mm square. Measuring the printed part gives 98.5mm x 99.3mm. Is it normal ? Can it be the origin of my square circle ?

Thanks for your answers !

Trou.thumb.jpg.d7837e70092a98723b5371a722a51ca3.jpg

  • Link to post
    Share on other sites

    Posted · Square circles

    are the thin rods exactly square? compared to the thicker rods?

  • Link to post
    Share on other sites

    Posted · Square circles

    I will wheck again the pulleys.

    Can a too high tension in the belts be a problem ?

    What do you mean @peggyb ?

  • Link to post
    Share on other sites

    Posted · Square circles

    I will wheck again the pulleys.

    Can a too high tension in the belts be a problem ?

    I would say that, from time to time, lines are not touching properly, i can see small gaps sometimes.

    What do you mean @peggyb ?

  • Link to post
    Share on other sites

    Posted · Square circles

    It's hard to tell from your photo but I think that might be normal. It's not a problem exactly with the printer but the PLA. It shrinks very quickly (milliseconds) as it comes out and while it is still liquid but shrinking it sticks to itself like a liquid rubber band. It's difficult to make vertical holes in this situation and they tend to be about .5mm smaller than where the head is positioned. However the holes although they tend to be smaller are usually mostly round but I don't always zoom in on them quite this much so I'm not sure if this is normal or not.

    Yes, too tight belts can cause a problem - it can greatly increase the friction causing play/backlash. It's weird but having the belts too loose or too tight will cause backlash but "too tight" is much more rare and is easily detected by pushing the head around with power to servos off.

  • Link to post
    Share on other sites

    Posted · Square circles

    I am pretty sure that my circles are not good. I have seen many pictures of them (UM + PLA) and they look much better than mine.

  • Link to post
    Share on other sites

    Posted · Square circles

    I'd like to see more pictures. Is this the bottom layer or top? I'd like to see outer edges also on top layers. Some of the issues causing square circles only affect the bottom layer (leveling off slightly). Some affect only upper levels. Loose belts and backlash affect how well the solid infill touches the edges. Typically with loose belts one is worse than the other and you get a pattern of alternating diagonal infill that is very distinct and clearly a belt issue - if both axes are EXACTLY equally loose then it's possible to get a nice pattern like in your picture but then the other problem is the infill doesn't touch the outer walls. Also with loose belts if you print certain rectangular/blocky objects and Cura switches directions (clockwise versus counter) you get very distinct patterns that instantly (to my eye) say "loose belt".

    Instead if this is a bottom layer picture it could be simply "move the nozzle closer to the bed by 1/4 turn on all 3 leveling screws".

  • Link to post
    Share on other sites

    Posted · Square circles

    Thank you for your help.

    Here are two more pictures. The first one is the down side. The square shape is the same for each Z level.

    Down.thumb.jpg.ec78f9f2a462c0f90a65b2d04d50a54c.jpg

    Top.thumb.jpg.9028ef3e652de0ab7ccb3e57eade5c68.jpg

    Down.thumb.jpg.ec78f9f2a462c0f90a65b2d04d50a54c.jpg

    Top.thumb.jpg.9028ef3e652de0ab7ccb3e57eade5c68.jpg

  • Link to post
    Share on other sites

    Posted · Square circles

    Table which the printer sits on vibrates, or printer has "DHL Elephant Sits on UM2-Syndrome", so is not stable on surface, if its not the short belts.

  • Link to post
    Share on other sites

    Posted · Square circles

    Alternatively, you can also see some density change in the infill at the top layer.

    What could also be is that 1 or 2 pulleys are not centrally drilled, like the hole is not completely in the middle.

    It is quite a hassle to check, but if we are totally sure it is not the short belts, it is something to look into.

    • Like 1
    Link to post
    Share on other sites

    Posted · Square circles

    Ah!!! Yes! I see it now! Backlash. See how you have pairs of infill touching and then a gap? touching/gap/touching/gap - the pattern repeats. The is EXACTLY what I was looking for. I didn't notice this in the first picture.

    This means you have backlash/play. It could be due to friction (consider loosening the end caps slightly on the 4 long rods or belts too tight) but more likely it's the belts and most likely the short belts (those going to one or both stepper motors).

    • Like 1
    Link to post
    Share on other sites

    Posted · Square circles

    the calibration of the rods is on page 55 of the manual, using the calibration sticks to get everything aligned and square.

  • Link to post
    Share on other sites

    Posted · Square circles

    @peggyb Yes the calibration of te rods seems good to me, thanks to the sticks.

    @gr5 I made a new test with more loose short belts : the circles are more and more square. So it means that your idea of a lack of tension in the short belts could be good. But the motors were placed at the lowest possible position : I can't give more tension to the short belts. So i'll try to minimize the friction with the end caps.

    I've also noticed that moving the extruder head manually is not totally fluid ...

    Different solutions to be explored ;)

  • Link to post
    Share on other sites

    Posted · Square circles

    We'll get there! Plenty of expertise in the forums :)

  • Link to post
    Share on other sites

    Posted · Square circles

    I know on my old UMO (three years old) I had to file one of the slots for the motors as it hadn't been cut through fully. That's probably not the issue here but you could still file the slot a bit so that you can push the motor down further if need be.

  • Link to post
    Share on other sites

    Posted · Square circles

    OK that's it ! To much friction because of the end caps !

    Now my circle are almost perfect (and no more gaps)!

    Thank you everybody :)

    • Like 2
    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

      • Introducing Universal Cura Projects in the UltiMaker Cura 5.7 beta
        Strap in for the first Cura release of 2024! This 5.7 beta release brings new material profiles as well as cloud printing for Method series printers, and introduces a powerful new way of sharing print settings using printer-agnostic project files! Also, if you want to download the cute dinosaur card holder featured below, it was specially designed for this release and can be found on Thingiverse! 
        • 10 replies
      • S-Line Firmware 8.3.0 was released Nov. 20th on the "Latest" firmware branch.
        (Sorry, was out of office when this released)

        This update is for...
        All UltiMaker S series  
        New features
         
        Temperature status. During print preparation, the temperatures of the print cores and build plate will be shown on the display. This gives a better indication of the progress and remaining wait time. Save log files in paused state. It is now possible to save the printer's log files to USB if the currently active print job is paused. Previously, the Dump logs to USB option was only enabled if the printer was in idle state. Confirm print removal via Digital Factory. If the printer is connected to the Digital Factory, it is now possible to confirm the removal of a previous print job via the Digital Factory interface. This is useful in situations where the build plate is clear, but the operator forgot to select Confirm removal on the printer’s display. Visit this page for more information about this feature.
        • 0 replies
    ×
    ×
    • Create New...