Horizontal ridges?

[janpieter 0]

 

 

Does anyone know what causes these horizontal ridges, and how it's possible to reduce this effect?

 

I printed these stands from http://www.thingiverse.com/thing:106568.

Very simple prints, no overhang, no retractions etc. Printed at 0.2 mm at low speed (outer shell only 20 mm/s), see Cura 14.06-settings screenshot. Some overhanging ridge appeared on the first print (left), mostly on the x-axis it seems. At first I thought the whole x-plane had shifted somewhat (slipping belt?), but it appears only at one side of the print. So with the second (mirrored) stand I rotated the print 90° to see if it was again mostly the x-axis. Seems to be the case.

 

Also, it looks as if the z-resolution changes whenever there is a 'change' in the shape or total surface area of a layer, causing 'ridges' all over the print. If I were printing fast, it would probably be that previous layers had more cooling time. But does that still have such a big effect at low speed? You'd think there would be plenty of cooling time anyway. I'm using this fanduct btw: http://www.thingiverse.com/thing:151061

 

Some more pics:

I'd be grateful for some helpful tips to reduce these effects!

 

[3dcase 37]

Hi,

Check your belttension(s) and printhead bearings

Reduce the Travelspeed (75) and see what happens.

It seems to be worse when the head jumps from Island to Island.

I f you use a Ulticontroller, you can lower the acceleration settings.

Groeten Kees

 

[janpieter 0]

Hi,

Check your belttension(s) and printhead bearings

Reduce the Travelspeed (75) and see what happens.

It seems to be worse when the head jumps from Island to Island.

I f you use a Ulticontroller, you can lower the acceleration settings.

Groeten Kees

 

Thanks for the reply, Kees, I'll try that later today.

At the moment it's printing these (same Cura-settings), and they look perfectly okay to me. Nice straight walls, consistent z-resolution. Of course there are no changes in surface area in these layers, like in the previous prints.

 

[gr5 1,710]

This is a complicated problem with a simple solution. I've seen this before (mostly on UM Original).

It's caused by "play" also known as "backlash". You can read about this in wikipedia. There are several symptoms you have all caused by the same thing. For example in your first posted photo on the inside of the left most wall you can see that in one section every other pass sticks "out". This is because the outer shell pass is clockwise on one pass and counter-clockwise on the next.

Anyway backlash can be caused by either high friction or more likely loose belts. Especially the short belts but long belts also. Make sure the short belts are quit tight - and/or tighten your long belts a bit. Check the tension on all 4 long belts and make them all as tight as the currently tightest one. They can be quite loose but I think you are too loose. There is a video by Erik that plays the long belts as a note and indicates the ideal tension. A little tighter than that is best. His video also shows how to tighten the belts or you can look at other options on thingiverse.