bottom layers not printing correctly

[ikymagoo 0]

i'm having an issue, the bottom layers are not printing correctly, i'm using an ultimaker 2 with colorFabb PLA, nozzle at 200 Cº and bed set to 60 Cº, is the bed too hot? see photo, not easy to see, but you can see the difference in shininess

any help would be great

thanks

 

[gr5 2,229]

It's an overhang thing. Overhangs are tough. The only help I can give you is to suggest the fan comes on sooner. By default it comes on 100% at 5mm. Better to have it come on at 100% by 1mm. If the fan comes on *too* fast then you have a different problem: you might get underextrusion because the head will cool to something like 190C if you go from zero fan to 100% instantly.

The heated bed for PLA helps the PLA flow better and therefore stick better to the glass (the PLA cools just slightly more slowly and so it flattens better onto it getting good surface contact. There is a sudden threshold where below a given temp (around 30 or 35C) you get bad adhesion to the glass and above the threshold you get good adhesion. 50C is well above that threshold. No need to go to 60C for "stickiness" reasons. There are other reasons to go >= 60C but not for this particular bowl.

 

[gr5 2,229]

Oh - having said all that - although the fan will help a bit I don't think it will help your issue enough to make you happy. You could get one of those butane torches and reheat that area of the bowl. That can make a huge difference in just a few seconds. You have to be very careful though as you can burn the red pla black if you linger too long.

I have this one for $7 (plus $10 for can of butane). It is a "must have" tool for 3d printing:

http://www.amazon.com/BBQbuy-Pencil-Welding-Soldering-Lighter/dp/B007A9YSPW/ref=sr_1_1?ie=UTF8&qid=1422549200&sr=8-1&keywords=butane+torch

 

[IRobertI 521]

If at all possible, keep the bottom angle to 45 degrees, that will make a very big difference in quality. There's also a sweet spot to hit when it comes to layer height. Too thin and it starts looking worse, too thick and it starts looking worse. Experimentation is key here as it differs between models and filaments.

If you go with the "45 degree rule" you can combine a chamfer and a fillet to get a fairly nice roundness of the bottom edge. See here:

http://support.3dverkstan.se/article/38-designing-for-3d-printing#chamfers

The 45 degrees isn't set in stone as such, but it's a good safety value.

 

[ikymagoo 0]

i did another bowl, with blue filament at the low fast setting and it didn't do this, (see photo)

the red one was done on normal, which i thought would be better

i'm baffled

 

[gr5 2,229]

1) What the hell! Why don't you print it with that flat spot down - that ring with the 4 holes - make that flat on the glass. This will make all overhangs on outside surface of the "ball" less than 35 degrees from vertical (much better than 45!). Of course there will be some ugliness *inside* the "bowl/ball" but hopefully that's not as important.

2) Dyes significantly change viscosity at a given temperature. Consider lowering the temp for red pla.

 

[chrisr 18]

i did another bowl, with blue filament at the low fast setting and it didn't do this, (see photo)

the red one was done on normal, which i thought would be better

i'm baffled

 

Ummm.... from the photo, I'm not really getting what the problem with that print is ? :???:

Edit: Ditto for the photo of your red print.

 

[ikymagoo 0]

i will post better photos soon,

thanks everyone!

 

[ikymagoo 0]

See better photos below,

 

red one

bad bottom,

colorFabb Traffic Red PLA

210 Cº

60 Cº

UM2 Quickprint: Normal Setting

blue one

good bottom, Ultimaker Blue PLA

210 Cº

60 Cº

UM2 Quickprint: Fast/Low Setting

do you think it's the heated bed, is it too hot?

thanks!

 

[chrisr 18]

Ah! clearer now :smile:

I don't think that's anything to do with the heated bed. I think it's possibly a couple of other things. I think you need to go hotter with your head for the red print and a little bit hotter for the blue as the layers near the base look as if you may be getting a little underextrusion there. The blue print doesn't look that bad apart from the "blobs" As well, some of the settings in your slicer may need tweaking. Are you using Cura ? If so, one setting you could look at is "spiralize" and perhaps as well your % of 'infill overlap' which if set too high I've found, can create 'blobs' in thin walls.

What layer height are you printing at and at what speed?

DIfferent colours can require different settings. White generally seems to be "fussy" I use Faberdashery for my PLA and I've found the settings between colours to be very consistent with little or no tweaking required.

Some other slicers let you alter the order in which the perimeter gets printed, i.e the outside of your vase (if your perimeter thickness consists of more than one pass of the print head) The order is switchable between 'inner to outer' or 'outer to inner' which one you select has an impact on the surface quality. Both KISSlicer and Simplify3D have this option, I think Cura defaults to inner to outer, it was certainly using that order in the last print I did.

Post the settings you're using and I'm sure you'll get some helpful advice! :smile:

Edit: Ah. I see you are using Cura.

 

[dodgrr 27]

I've had the same issues with underhanging curves, solved by tweaking temps (both bed and head,) and print speed. Might be one of those thats needs to be tuned on the fly and babysat unless you want to brave plug-ins to fine tune it. Nice bowls BTW!