Hello there, This is a little off-topic: My first printer,

Hello there,

This is a little off-topic:
My first printer, a BQ witbox is giving me headaches, it doesn’t print round circles. I printed a test piece, see photo. Straight lines and infill is not best quality, but fine. However the circles are another story:

  • They’re printed clockwise, see the angles at 13 and 19 o’clock.
  • This one is at 60mm/s, same results with different speeds.
  • Cura, slic3d or Simplify3d, same results
  • Hardware seems fine, no belt or hotend play.
    Do you have any idea where to start searching ?
  • Replace x-y steppers ?
  • Replace electronics ?

If this is too far from the group’s topic, feel free to remove this post :wink:

If this is the orientation it printed, looks like backlash in Y (bed direction reversing is not crisp, and that lag causes the lack of roundness).

Loose pulley?

Yes the picture is as printed, X horizontal, Y vertical

@Miguel_Sanchez Pulleys are ok, I checked first. In this case I think it should be visible on squares and infill.
@Eclsnowman good point, I’ll check the Y axis. Maybe the Y belts are worn out and there’s some play with the pulleys

Try and engauging the Y stepper so it’s locked and then try and move the bed. You can then determine if it’s perhaps the glass moving on the bed, or the bed moving on the belt clamp, or the pulley moving on the motor, etc.

@Maxime_Favre If you draw a line with a dark marker across shaft and pulley side you can double check that line is never changing alignment. It is not uncommon that it looks ok on first inspection but a loose grub screw allows certain play only when motion direction changes. Squares will not be affected on their squareness but measure would be a bit off.

Also make sure your X- and Y-axis’ are square.

If you watch Tom’s review of the witbox, he blames it on the stickness of the igus bushings. https://www.youtube.com/watch?v=7KcdMEmCj0g&list=UUb8Rde3uRL1ohROUVg46h1A (half way through the video).

@Walter_Hsiao that would make sense. I had similar issues on my old corexy using pbc linear bearing that are similar to the Igus type.

@Walter_Hsiao Thanks for the link ! I’ll look for replacing thoses igus sticky things. Sadly I bought the printer 10 month before his review, it maybe would have changed my mind.

Could you try @Mike_Miller 's trick posted here https://plus.google.com/+MikeMiller0/posts/RdWbwVSw3Es ?

That’s only for carriages that drag upon initial assembly…IGUS bushings seem to have non-circular prints of a certain size, I had no issues with larger circles, or really small holes…larger non circular issues may be caused by un matched belt tension.