backlash

[roald 2]

After i get some strange gapes between my outer and inner wall, i design a pen holder and wright a simple g-code to check what get wrong.

after some sketches i detect the same problem but couldn't fix it. i'm already dismount, switch some parts and mount the X/Y axis but without improvement

[gr5 2,093]

Gaps can be caused by backlash or underextrusion.  There's nothing wrong with marlin or cura.  For example if your nozzle width is .4 and your shell is .8 then it will place the lines .2mm inward from the final edge (radius of nozzle) and extrude just the right amount to make lines .4mm thick.  Cura is very sophisticated that way and corrects for nozzle width.

Underextrusion:

Try printing slower and hotter and thinner (15mm/sec .1mm layer 230C) as an experiment to eliminate this issue as slower and hotter almost always fix this. You only have to test this for a few layers of a print to realize if this matters.

backlash:

Very common on UMO and easy to eliminate.  It can be because of high friction (belts stretch and head never quite reaches desired location) or it can be because something is loose.

Friction is often the endcaps on the ends of the rods.  Try loosening all of them a tiny amount and push the head around and see if it move more easily.  Or if X and Y axes have different friction then concentrate on that issue.  Belts too tight can cause extra friction also.

Loose - most commonly the belts are too lose (what?  belts too tight or too lose can both cause backlash?  yes.).  But other things can be loose.  Without letting the steppers move (don't push hard enough to move stepeprs) push the head around in different directions - does it move?  Is it loose?

Edited May 16, 2016 by Guest

[roald 2]

oke i tried the follow things and check if there is a improvement

loose/fasten the bands

check rod caps

exchange X/Y stepper motor

exchange stepper drivers

play with retraction

change bed nozzle distance

when i loose the belt a little change retraction and bed distance i get a solid first layer but there are a few miss steps at the right side and the round but not on the left wall strange enough? also not a fully solid top

the next thing i getting tried now is to change my belts en and pully's to gt2 ones

4x 606mm closed-loop belt gt2

2x 202mm endless belt gt2

6x GT2 Pulley 20 Tooth 8mm Bore

2x UM GT2 Pulley 20 Tooth 5mm

2x Twin Pulley GT2 20 Tooth 8mm Bore

4x Selfgraphite Linear Bearing 8*12*30mm

[gr5 2,093]

Seems like a lot of trouble if your problem was actually not backlash and instead underextrusion as either problem can create gaps between walls of a part.

Anyway here is some more info on backlash:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=14474