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Timbergetter

Degraded towards end of each print layer.

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I am hoping that someone will recognise what might be causing the defects in the print shown. I am doing a draft print so the speed is 80 mm/s and the layer height is 0.4 mm. (actually 0.2 mm as found later). If the defects were more random I would think that slowing things down might help. However most of the print is acceptable to me and it is only towards the end of each layer that the feed seems to starve for filament. On the outside surface the layer change occurs at about the 5 o’clock position. Everything is good from 5 o’clock all the way around to about 4 o’clock where the problem begins. On the inside surfaces a similar but worse result occurs and is about 180 degrees rotated compared to the outside surface.

 

Even the 45 degree overhang half way up the outside surface is good except in the 4 to 5 o’clock postion.

 

Cura 3.2.1 in use.

 

AJH_3886.thumb.jpg.96c9e182f706675a864d059931df7754.jpg

Edited by Timbergetter
Fix fact

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80mm/sec with .4 layer height and .4 layer width - well that's a very thick layer.  Multiply those 3 numbers and you get 13.8mm^3/sec.  That's a bit beyond what any ultimaker printer can do (what kind of printer do you have).  Maybe you should switch to a 0.6 or 0.8 nozzle which allows a much higher printing volume.

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Many thanks gr5. I’ll try attaching photo again.

I’m a bit new to this so I didn’t recognise that 13 mm^3/s was large. If the photo worked this time you will see that the first 80% of each layer is fine but then tails off to under-extrusion (if that’s what I’m seeing) in the last 20%. I suppose the travel time between layers might allow a bit of catch-up time to replenish the filament feed/pressure. Is that a possibility?

 

My printer is the Cocoon Create

Tube-1.jpg

Edited by Timbergetter
More info

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Okay well even at 0.2mm layer that's still faster than I recommend and faster than many printers can do (7 mm^3/sec).  I'd try lowering the speed to 40mm/sec (3.5mm^3/sec). Here is a table of max speeds for ultimakers - other printers are similar:

 

Here are top recommended speeds for .2mm layers (twice as fast for .1mm layers) and .4mm nozzle:
20mm/sec at 200C
30mm/sec at 210C
40mm/sec at 225C
50mm/sec at 240C

 

So obviously the next question is what temperature are you printing at.

 

So that pattern you see are layers that are partly underextruded and part of the layer looks fine.  I would look at the part in slice view if you want to know more and you can pick a layer with the vertical layer scroll and then use the horizontal scroll just above and you can see what the print pattern is - what the order is - so you can know if outer wall is printing clockwise or counter clockwise.

 

Then also in layer view show speeds with color so you can see where it's printing faster and where it's printing slower.

 

I'm going to guess it's printing at different speeds or different line widths on a given layer (infill or inner shell different than outer shell) and the transition from slow speed to fast speed or thin line width to thicker line width means it underextrudes for a bit until the pressure can equalize.

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Thanks again gr5.  I can now see I have been asking for miracles with my selection of layer height, speed and temperature.  I shall now go away and try again while taking account of your recommended throughput/temperature combinations.

I used the Cura slice viewer for the first time and can now see the value in that.  The outside shell is being laid down in an anti-clockwise progression.  The under-extrusion is therefore happening at the start of a  circuit, and this now makes sense to me.

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