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profepaco

top and bottom layers

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I am printing a robot wheel and everything is ok except bottom and top layers. Please have a look:

gallery_34293_830_477985.jpg

I have a one week old UM2.

I have tried different settings. I have increased temperature to 230 (this is PLA from faderdashery and I have the same problem for whatever colour from them or with PLA for UM).

I have increased flow rate to 115%.

I have reduced the printing speed, I have increased the printing speed.

Even I have increased the printing speed of the first layer... just to try...

the result is very, very similar in all the cases.

Any idea to obtain a more uniform surface? Thanks in advance.

 

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For a mirror first layer surface.

Initial layer thinckness 0,1 on the Cura option

And most important a really good bed levelling, it's hard to make this perfectly, but with a little practice it is easy.

 

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For a mirror first layer surface.

Initial layer thinckness 0,1 on the Cura option

And most important a really good bed levelling, it's hard to make this perfectly, but with a little practice it is easy.

 

i'll try it tomorrow, thanks...

 

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If the first layer height is .1mm it will be very hard to get the leveling perfect. To get as good as you want you need levelling height accuracy about 10X better than layer height. So .1mm layer needs .01mm accuracy of levelling. The best way to do this is trial and error where you lay down a few brim lines (or skirt lines) and make sure they are squished to a .1mm by .4mm stripe (4 times wider than tall) and that 2 consecutive strips are perfectly touching.

I much prefer a .3mm first layer so then I only need levelling accuracy to .03mm. Much easier.

Changing flow to 115% was the right track but you get the same effect by lowering the bed by 15% of the first layer height (you have 15% less space to put the plastic between the nozzle and the glass.

 

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So I tried with 0.1 first layer, different temperatures, different flow rates and the surface has improved in some cases, but the problems is still there.

I think that I should move to slic3r. There is an option for top / bottom layer fill pattern: "concentric".

More later...

 

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First attempt with slic3r almost destroys my UM2. The head was hitting the glass... before printing I saw a message saying that the file to print will override machine settings....

the bed was very high before printing

:shock:

 

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Having a closer look at your picture I'm not sure what exactly you're talking about.

What aspect of the surface has to be more uniform? If I look at your picture, I clearly see the single lines of the print. Is this what disturbs you? You will always see the different lines when you hold the bottom surface like that and have some light reflected on the surface.

Could you please repost the picture including some arrows and/or circles and a clear statement what it's wrong on distinct spots?

However, please also state the print speed you used for the first layer in mm/s, the infill overlap and the bed temperature. These are important influences on the first layer quality.

Another important question: Did you print anything else than PLA before on your UM2?

A picture from the first layer of this print FROM TOP would also be very helpful (just print the first layer and then abort the print).

I use the very same filament from Faberdashery. Try to print the first layer at 20mm/s and 210°C. Together with a proper bed leveling this gives me a perfect first layer.

 

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yes, the problem is that you can see the lines of printing. For that reason I think concentric filling would produce better results. But I cannot use slic3r at the moment. Crashing with the bed!

Bottom layer speed: 30 mm/s

Bed temperature: 46 C

Infill overlap = 15%

head temperature = 220 (although I have tried many values here)

A picture of the bottom (first) layer from visible side:

gallery_34293_830_627249.jpg

A picture after some layers printing (from printing surface, after aborting):

gallery_34293_830_67809.jpg

Thanks for helping.

 

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On your last picture one can see some effusion of the first layer. That means you are overextruding on the first layer. If this happens, material is squeezed around the tip of the hotend which results in not very nice lines.

So please try it again with the 210°C or reduce the flow on the first layer. What filament diameter did you specify?

I don't know what the whole wheel should look like (if cross-section somehow changes) but if you want to have a concentric infill you can achieve this with Cura by setting the shell thickness to at least half the width of the rim. The result is a print with '100% infill' (actually a print with only shell and no infill). And maybe disable combing in order to get rid of the crossing lines.

 

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I have never gotten a perfect bottom first layer. When you hold something such that the light reflects perfectly off the bottom your eyes can see imperfections that your fingers can't feel. You can't see these imperfections at any other angle.

But if I were to experiment I'd want the bottom layer to not-freeze very quickly. I'd try 20mm/sec, 240C, heated bed at 70C. This will make it so that the PLA is more liquid as it is being placed down and flows better. But it's going to be hard to get every last bit of air out. I have some parts with perfect bottom *sections* but I'm not sure how I did it and why other sections are worse.

Regarding setting shell thickness to say 10mm, this will work but the downside is you get 100% infill for every layer so for a small gear that might be okay but for some parts this will 10X the print time.

Hopefully, some day, Cura will let you do per-layer settings. I know this is a very confusing feature to implement in the GUI (other slicers do it) but sometimes it's needed.

 

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It might not be possible to get a 100% perfect bottom layer but you can get damn close. The image I linked in below (linked to the fullsize version) shows a pretty darn good bottom layer IMHO. That print was with a 0.1mm bottom layer. With 0.2mm and 0.3mm bottom layers the spacing between the lines of plastic get a lot more obvious, at least in my experience.

When I don't want a "perfect" mirror finish on the bottom I go with 0.2mm layers as the bed leveling isn't quite as critical then. I've never used 0.3 for the bottom or layer height in general.

On this print I had to really look closely to see the imperfections.

http://ultimaker.ipbhost.com/uploads/gallery/album_83/gallery_198_83_81659.jpg

 

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I have had the same problem you have, I tried everything you have already consider, and I ended reseting the UM2 and leveling the bed to my best.

And now I have glassy finish on the bottom, printer settings are 210ºC, 75ºC bed, 20 mm/s first layer, first layer thickness 0.3 mm, layer height 0.1

Which are the settings cura give to normal printing in quick print mode.

Hope this helps

 

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I am still trying different settings...

in my case best results seem to be obtained when print speed is 20 mm/s (as yours) helps and of course a good bed levelling.

However, I am using 235 C for the first layer ( I change it for the second layer with twekatZ). I think the most fluid filament helps to obtain better surface. My bed temperature is 65, fist layer, 46 for second... and close to the end of printing I reduce it to 20C to cool the bed before prints end.

rest of parameters initial layer 0.2, rest of layers 0.15

 

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Isn't decreasing the heat of the bed so much risky? I would think that the print would detach a lot easier at 20°c??

 

No. Because when I decrease the temp it needs only about 5-10 minutes to finish. And,as you know, the temp decreases very slowly.

BTW, 20C here is Spain is heat bed = off :cool:

 

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LOL we hit 22c in the UK today, although it was less that that underneath my car. Do not forget guys with 3D'd plastic filament you are not going to match injection moulding- as far as I have ever seen

 

yes, but now the look is much better.

And this is the way to understand how setting works.

 

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