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ksn-arts

top layer- the distance between the lines of plastic

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It doesn't look blocked - I mean it doesn't look underextruded. But you could raise the temp by 10C if it's a little underextruded or slow it down by 50% when it gets to the top layer. How many solid layers are under the top layer? I recommend at least 4 layers (top thickness .8).

In Cura did you enter "2.85mm" for the filament diamter? If you enter "3.0mm" it will underextrude of course.

 

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It doesn't look blocked - I mean it doesn't look underextruded. But you could raise the temp by 10C if it's a little underextruded or slow it down by 50% when it gets to the top layer. How many solid layers are under the top layer? I recommend at least 4 layers (top thickness .8).

In Cura did you enter "2.85mm" for the filament diamter? If you enter "3.0mm" it will underextrude of course.

 

i have two type plastic 3mm and 2,85 The diameter of the tunes in the printer. when replaced plastic.top botom 0.7 mm. were you enter in cura v 14.07 filament diamter???

 

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were you enter in cura v 14.07 filament diamter?

 

Sorry - that is for UM Original only. I have both printers. I forgot about that.

 

when replaced plastic.top botom 0.7 mm

 

Ah! That could be the problem. You should always make this a multiple of your layer height. I'm not sure what happens if you do that! Try .6 or .8. It probably underextrudes by 50% on the top layer. Maybe. I don't know.

This should always be a multiple of your layer height which you said is .2mm.

 

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I've had similar problems with my UM2. It's most pronounced with 0.2 mm layers but can be seen with 0.1 mm layers as well. I've been in contact with Robert at 3dverkstan and we've tested tightening the short bands, performing atomic cleaning, aligning the bed and checking the nozzle for blocking. I've tested for under extrusion with the standard test and at 250C we're getting great results all the way up to 10 mm^3/s. At 210 C it fails already at 3 mm^3/s and at 220C it fails at 8 mm^3/2.

 

I've attached an image showing a test print made at 220 C, 0.2 mm layers at 40 mm/s. The shell thickness was 0.8 mm and the top and bottom layers 0.6 mm. I've tested this at 230 C with pretty much the same result as well. I'm a bit stuck and am not sure what to try next :(

 

/Mikael

gallery_36523_1334_752806.jpg

 

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Good morning.

Nope, I'm getting pretty much the same results as you, gr5. I checked with a cheap/bad temperature probe as well (the students were busy with the nice ones) and I'm getting values that are maybe 10C below the set temperature. Considering the probe and the bad thermal connection I would assume this is fine.

 

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I just did a test with 15 x 15 x 3 mm cubes spaced out over the print area. I wanted to check if there was a large variation in the results as I've seen some lateral variations in previous prints. This test was done with PLA/PHA at 230C, 0.2 mm layers, 50 mm/s and 0.6 mm top/bottom surface. The results did vary a bit but on almost all places the top layer is not covering the surface and the side walls.

Judging from what I've read and seen it looks a lot like what seems to be coupled with the short belts not being tight enough. A couple of days ago, I did unscrew the motors and push them as far down as I could so I'm not sure if that is what really going on or if there is anything else that can be done.

Considering that the extrusion cylinder test looks fine on this instrument, could it still be under extrusion somehow? It really does look like it's not feeding enough material although this print was done at 4 mm^3/s (which works fine in the extrusion test at 230C).

gallery_36523_1334_364094.jpg

gallery_36523_1334_91582.jpg

 

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I've attached an image showing a test print made at 220 C, 0.2 mm layers at 40 mm/s. The shell thickness was 0.8 mm and the top and bottom layers 0.6 mm. I've tested this at 230 C with pretty much the same result as well. I'm a bit stuck and am not sure what to try next :(

 

Have you tried decreasing your layer thickness or increasing your top/bottom thickness? You're only giving it 3 layers of material to work with there.

If you've got good internal supports/lots of infill that might be okay, but I generally find I need at least 5-6 layers (and preferably more) to get a good looking top surface when printing over a hollow portion of a part. What usually happens is that the first layer will have some gaps/issues/broken bridges, and then those gradually get corrected on subsequent layers.

 

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Have you tried decreasing your layer thickness or increasing your top/bottom thickness? You're only giving it 3 layers of material to work with there.

If you've got good internal supports/lots of infill that might be okay, but I generally find I need at least 5-6 layers (and preferably more) to get a good looking top surface when printing over a hollow portion of a part. What usually happens is that the first layer will have some gaps/issues/broken bridges, and then those gradually get corrected on subsequent layers.

 

The effect is for sure much less visible with thinner layers. I've seen the same surface effect even with 1 mm top layer though. Since you actually can see through the top layers you still get a pretty open surface even with thicker layers it seems.

 

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I did some new tests yesterday and today and tried 0.2 mm layers at 220 and 230 C at 20 mm/s. I also tried increasing the flow to 105% while printing but without any effect. Today I did a new print with 0.1 mm layers at 40 mm/s and 220C where I get okey top surfaces on some places but still gaps to the inner shell.

If this is related to the belt tension and I've tried moving the short belt motors as far down as possible, is there anything else I could try?

 

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It has nothing to do with belt tension and we all have exactly the same issue which draws me crazy !

That's all about Cura IMO.

I'm using 14.07 Mac version (if that make any difference Vs Windows version)

Our second thread about exactly the same issue http://umforum.ultimaker.com/index.php?/topic/5375-top-layers-not-touching-um2/page-7

 

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