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eduardas-afanasjevas

Calibrating filament diameter settings

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I've been using a Faberdashery PLA 3MM filament for my Ultimaker 2. When printing layers sloping outwards (or mild overhangs), the printer seems to feed too much material. Excess starts to add up with every layers until the surface gets messed up. I tried tuning the material flow settings (reducing to 95-97%) while printing, however, the results are not always consistent. Sometimes, the Ultimaker leaves tiny gaps when printing with reduced flow which then leads to further errors.

I suspect I need to calibrate the filament diameter settings or the feed rate (i.e. related between feed speed and filament diameter). Any advice how to do this properly?

UPDATE. Image attached.http://imgur.com/lAf7k5e

 

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I think by printing at thinner layers you solve a big part of this problem.

Lower temperature may also effect it.

Are both your fans working?

I don't think you have to tune the material flow, it is an overhang-thing.

 

Yes, both fans are working. I tried printing at 60-100 microns with pretty much the same results. I did notice that PLA doesn't cool down fast enough and gets quite flexible.

What temperature would you recommend?

 

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This is simply because that little froggy has a very shallow angle for its belly and the filament strands are having trouble adhering to their neighbours. Quite a bit of the filament is sticking out into thin air, just barely attached to the model, then the next layer comes along on top and pushes the filament down making things look messy.

Like Sander points out printing thinner layers will help here as the displacement between layers will be reduced. IIRC there's also an updated model of that frog where it's sitting more upright which helps quite a bit.

 

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This is simply because that little froggy has a very shallow angle for its belly and the filament strands are having trouble adhering to their neighbours. Quite a bit of the filament is sticking out into thin air, just barely attached to the model, then the next layer comes along on top and pushes the filament down making things look messy.

Like Sander points out printing thinner layers will help here as the displacement between layers will be reduced. IIRC there's also an updated model of that frog where it's sitting more upright which helps quite a bit.

 

Can you post a link to the updated model?

 

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Overhangs are tough to get "perfect". This is actually pretty good for this kind of an overhang. I would print slow, cool and thin layers and with as much fan as possible.

Going below .1mm tends to make it worse but I would try it. Thin layers helps because that way more filament is touching the layer below and less filament is hanging over thin air.

So set your flow back to 100%.

Try 0.1mm layers, 20mm/sec, 190C.

Now overhangs also have a problem where the plastic shrinks and lifts and then the print head hits the part you are printing - did you notice that at all? If you have that issue then keep things warm: 70C heated bed. Keep things warm by lowering fans possibly to 50% and maybe cover the front of the printer to keep the air warm that is close to the frog belly. If this isn't a problem then better to keep the fans at 100%.

After you do that, try .05mm layers or .03mm layers to see if quality is better or worse. The limiting factor here is the Z drive. If you ask for .05mm layer but get .07mm on the movement of the bed, then you will be underextruding by a lot (and overextruding on the next layer where it corrects itself). So the lines can get *more* prominent when the layers are too thin. But the UM2 is pretty amazing so you might have no trouble going down to .03mm.

 

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Now overhangs also have a problem where the plastic shrinks and lifts and then the print head hits the part you are printing - did you notice that at all? If you have that issue then keep things warm: 70C heated bed. Keep things warm by lowering fans possibly to 50% and maybe cover the front of the printer to keep the air warm that is close to the frog belly. If this isn't a problem then better to keep the fans at 100%.

 

This is exactly what I noticed. Why would I need to keep things warm if this is happening? I noticed that the part that lifts becomes very wobbly and eventually spills out.

 

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The plastic shrinks when it gets cool, by keeping everything warm until the print is finished you limit its impact on the print. Personally I haven't had good results with a bed that hot though, I found overhangs became worse. But, that isn't necessarily an absolute truth and will also depend on the model.

 

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It depends what you mean by "overhang". If the overhang is too steep then heat makes it cool slower and it can droop as it is printed and make it a little uglier but at least it prints. For slightly less steep overhangs, the heat keeps it from shrinking and lifting up and keeps the head from hitting your print.

PLA shrinks linearly based on temperature. Another way to say that is the density of PLA versus termperature is (mostly) a straight line. But the pulling doesn't kick in until around the glass temperature (50-60C) so if you can keep PLA above 50C it shouldn't shrink so much until the print is over (where it all shrinks at the same time and isn't as serious).

 

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