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gabrielmfr

Severe Stringing and problems with Z hight

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Posted · Severe Stringing and problems with Z hight

 

Hello fellow builders,

I have had my ultimaker for a few months now and my prints look amazing and for the most part I don't have many problems with anything.

But for some strange reason I have severe stringing when there are jumps. I have looked in to the things that cause stringing and i think I have eliminated them all ( the movement of the jumps are now 300mm/s, I extrude at 185-190C) and for some reason it just keeps stringing and bad. Any ideas?

My other problem is with the Z axes. When I do prints that start big and get small they always tend to be a perfect print on the bottom and when I get to the small areas they over extrude. Is this normal? I use netfabb I there a way to alter the flow with the area?

Thanks for the help in advanced.

 

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Posted · Severe Stringing and problems with Z hight

I don't know much about netfabb, but you will want to make sure that you have retraction enabled; I seem to recall that for a long time netfabb didn't do retraction and/or didn't do it right. Are you fully up-to-date with the latest version?

 

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Posted · Severe Stringing and problems with Z hight

1) retraction

Sorry I don't use nf, only Cura. Lower temps helps but you need retraction on the UM because of the bowden tube. 4.5mm retraction is about right. Cura has this on by default but you have to set the minimum travel distance to enable retraction in Cura.

2) small/fast layers

Regarding smaller objects/layers not coming out as nice - you need to slow down the machine and crank the fan. Usually 5 seconds per layer is enough for it to cool. If it doesn't cool enough the next layer looks worse and the layer above that even worse until a cube is turning into a warped ellipse (the corners are particularly melted looking).

Cura again has a wonderful setting: "minimal layer cool time" which defaults to 7 seconds. It slows down the speed (mm/sec) for each layer so that if it would have taken less than 7 seconds it sets the correct speed so it takes exactly 7 seconds.

Alternatively if you have an ulticontroller you can slow down the layers manually when you get near the top of your print. Remember - no faster than 5 seconds per layer. And make sure the fan is on for these fast layers.

 

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Posted · Severe Stringing and problems with Z hight

Thank you all for your help!

I am now trying to put the 5 seg time limit for each layer on NF but still haven't been able to do this correctly. In regard to the retraction. I am now retracting on the correct speed but it still didn't help a lot. I am now thinking in playing around with the extrude rate to see if its over extruding in some point or not.

 

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Posted · Severe Stringing and problems with Z hight

If it is retracting but still stringing look at this - first photo:

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=13081

Note that each color and manufacturer is different. For white PLA from printbl I can't get it to stop stringing no matter what I do (although the strings are thinner than a hair - maybe .05mm? certainly much much less than .1mm).

 

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