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zoev89

Top layers not filled in completely UM original

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I recently got my UM original running and I noticed that the top layer does not get filled in completely. I have been printing with layer hight 0.2 and PLA at 220 and at 230. But still there are small holes. It seems like the amount of plastic is not enough to fill everything. Print speed was at 50 and all the rest were default settings. I am using a heated platform at 60. But since the top layer is about 2 cm away from the platform I think it is irrelevant. Any idea which parameter I need to change to get it completely filled in. At places it does do it.

Also you can see that there is some stringing on the photo some advice might be nice but the top layer has more is more noticable the strings I can cut away.

TopLayersNotFilled

 

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1) Your picture doesn't seem to work. To post a picture please post here. Click "gallery" on the top left of this page, then click blue "upload" button. Then edit your post and click on "my media" next to smile icon to insert your picture.

2) I think you are talking about "pillowing". This is much worse if the fans aren't working - please double check that your side 2 fans work. Also increasing "top/bottom layer thickness" will help. Here is a photo and explanation(post#10):

http://umforum.ultimaker.com/index.php?/topic/1872-some-calibration-photographs/?p=17300

3) I'm not sure about the stringing unless you include a photo. Make sure "retraction" is checked and look at the part in layer view and make sure it shows a vertical blue line to indicate retraction before any move causing "strings".

 

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I think I know what you're talking about, I too have seen this issue multiple times, there are little gaps between the lines that the printer head deposits. I'm not entirely sure myself which printer setting remedies this. I haven't spent much time trying to fix the problem but I think a higher printing temperature more specifically on the final layers might help. as for the stringing if you increase your retraction speed and distance you should have significantly less stringing.

 

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Hi Gr5,

What is wrong with the image? Even when I log off the forum it is still visible.

Actually your tip on increasing the top layer thickness is correct but I already anticipated that by increasing it to 1.2mm. Should be enough I think. The fan on the printhead is working. I will try to print on again tonight it takes about 2.5 hours.. If I am on time I will increase the temperature when printing the top to 240 as a experiment. I already did 220 and 230. It almost looks like there is not enough material coming out of the nozzel. When I look at the filament entering the bodentube I see that it has little holes and no signs of skipping.

The other forum post is very interesting but given those results my printing temperature is already at the high side.

Where are the holes comming from....

 

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The filament is 2.9mm at the location it is printing right now. So it is a little thicker then the 2.85 setting.

While it is printing right now I see that the small holes are coming again. I just found in the tune menu the flow parameter. I increased it from 100 to 106. Lets see what is happening..

 

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This link:

http://www.modelbouwensport.nl/3DPrinter/PhotosForum/TopLayersNotFilled.JPG

Gives me "404 - Not Found". This was true 24 hours ago and is also true now. Also unless this is your personal website it would be best to post on this forum as we want the pictures to still work 10 years from now.

The cause of pillowing has to do with the "threads" of filament breaking as they are pulled and then cross the sharp infill pattern.

 

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Yesterdays evening print printed a little better I had the flow changed from 100 to 108% and the temperature to 240 for the top layer. This resulted in a large improvement not perfect there are still some small holes.

I checked the short and long belts as far as the sound is the tone is about right. So I think that the x,y directions are ok. I also don't see artifacts on corners that would indicate belt issues.

I will move the image to the utlimaker website (will take some time since I can't do it tonight) eventhough it was posted on my personal website. But who knows what will change in 10 years from now :)

 

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I moved the image to the gallery and updated the original post. So that was a learning experience. The last print of this object (I needed 3 of them) was perfect with 240 and 108%. Then I wanted to print a other object and it failed. The print lifted from the bed. I guess I have to clean my bed after about 5 prints. I will first try cleaning it and if that does not help add a small layer of PV glue.

 

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Hi yellowshark,

Well the stringing is very likely caused by the high temperature I agree on that part. If I look at GR5 his tests they show that high temperature can cause stringing. But the holes on the top layer that was still unexplained. I have been able to improve it by increasing the temperature but that had only a little effect but the largest effect was the flow to 108%. Possible this could be solved an other way or as you say an other problem is hiding it but we have not yet been able to pinpoint it. I am open to suggestions. I still need to print an other part with similar issues.

 

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Okay - that's definitely not pillowing!

That's just basic underextrusion. Most likely caused by the top layers sagging a bit. If you make your top/bottom thickness a little thicker you can add one or two more layers and that is very likely what it takes to fix it. It takes several layers to recover - the "lowest top layer" sags quite a bit. Then the next layer above is underextruded because there is more than the normal spacing vertically, each successive layer should get better and better. Maybe 2 more layers will get you where you want to be.

Manually setting flow only on the "second lowest top layer" would help a lot to fill in the top of the sagging layer. Maybe around 150 to 200% even. For example if if sags .2mm then you would need 200% fill to compensate. If it sags a whole millimeter you would need 500% flow to fill it all in. Then go back to 100% for the remaining layers.

But it's easier just to add a few more layers to your top/bottom thickness.

 

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George beat me to it, I was going to ask what was below the top layer! Does the inside have to be hollow? If not use a 20% infill finished with 3 top layers. If it does then as George says put in a few more top layers. Alternatively you could use support and then cut away the supporting PLA. The inside as it stands with the sagging 1st top layer is going to be be a mess anyway, using support may make it better.

 

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Hi Yellowshark and Gr5,

The infill is 15%. And I don't think it is the infill issue here so much. Because I see similar things happening at the bottom layer. It does not matter there at all since I don't see it when the print is finished. The first layer is squashed into the bed so perfect. Then the next 2 3 layers are fine and then slowly the small holes appear just the same as the top layer. I increased the top and bottom thickness to 1.2mm. Is that still to little? To me it more sounds like under extrusion when using 0.2mm layers. Could it be that I have missed a setting in cura when increasing the layer hight from 0.1 to 0.2mm?

Or could it be that the platform is not lowering with 0.2mm but more. On the other hand the hight of the models look ok (I only have data for the first 1 or 2 cm, haven't printed higher).

 

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OK well you are changing the problem now!! Can you clarify a point please. You say "Because I see similar things happening at the bottom layer". The you say " The first layer is squashed into the bed so perfect". That is contradictory.

We need to know precisely what is happening so we can help.

If you are running 20% infill then in my experience at .200 3 top layers should give you an OK finish. It certainly will with .300 so I suggest you take your top layer fill to 5 layers at .200

Then lower your speed to 30mm/s or 20mm/s. . Take flow back to 100% and drop your temp to a max of 220. Personally I would use 210 or lower but I will not argue that point.. Run the print and then let us know what the result is. We can then consider what is happening. Actually at the same time change the model. Just take a test cube off the Ultimaker site or Thingiverse.

 

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Okay - I'm wrong again. Not pillowing. Not sagging. That leaves normal underextrusion. I didn't see any signs of underextrusion on the sides of the part so I assumed the problem was something different.

You have .2mm at 50mm/sec with .4mm nozzle which when you multiply those 3 numbers together (can you do 2X4X5 in your head? You shouldn't need a calculator) give you 4mm^3/sec of filament. I can do that without much trouble at 230C but with a bit of underextrusion. You can improve things by either reducing the total volume or increasing the temp to say 240C.

So for example if you go to .1mm layers you will be cutting the volume of PLA going through that nozzle in half from 4 to 2 cubic mm/sec. Or you can cut the speed back to maybe 30mm/sec. Or you can just slow it down (or heat it up) on the top most layers.

 

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Ha we nailed it down!

It is just a form of under extrusion. It is apparently not able to push more filament through the nozzle. I just reduced the printing speed to 40mm/s and let the temperature back to the original 220 and the print comes out fine. I don't have to increase the flow anymore. So with the blue default ultimaker pla I am not able to extrude much more then 4mm^3/sec and at 3.2mm^3/sec it seems fine. Just as Gr5 said he is able to extrude at 4 mm^3/sec but with a little bit of underextrusion and that is exactly what happened here. You can't see it on the sides but you do see it on horizontal surfaces. The reason why the very first layer was fine was just due to the fact that the default there is bottom layer speed = 20mm/s. :mrgreen:

Nice, thanks for all the advise I learned a lot as newbie.

 

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Great news Zoev89. A learning experience there. No doubt some will vehemently disagree with me. But my view is that if your printer does not have a fault then really you should rarely needed to push you printer beyond 220c for NORMAL PLA at anything up to .300 and 60mm/s (I never go faster than that so cannot comment). I said rarely because I did have one filament that I could not get right without going to 225-230 - never used it since.

And to me changing the flow % is just masking a problem,either you have a printer problem or duff filament or your temp is wrong - never used it! Although I have never experienced it, I suppose there may be a particular geometry where a change in flow would be beneficial but I am not convinced.

 

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Hi George I did not know you can specify different thicknesses for top and bottom layers

 

Not really, no. The command line slicer (steamEngine) does it but Cura does not. Yet. What I meant is to ask for a thicker top layer and just accept the fact that you also end up with a thicker bottom layer.

 

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