Poor performance on overhangs

[jsanders 0]

Hi Ulti-makers!

I have been using my new Ultimaker 2 for a few weeks now.

I noticed that it performs poorly when printing overhangs.

To demonstrate the problem, I printed an Ultimaker 2 temperature test:

http://www.thingiverse.com/thing:696093

Compared to the two completed part photos on Thingaverse, mine looks like a mess:

 

 

The part was the "High quality print" with build plate set to 60C.

The print settings are already in the gcode file for that part, so I can't list them.

I am using the latest firmware, uploaded using cura just prior to this test.

The material was Ultimaker PLA (white).

I did an atomic method nozzle clean just prior to the print, and the PLA flowed vertically downwards on start.

I have never used ABS in this Ultimaker 2 - just white and blue Ultimaker PLA.

The same problem is visible in the small overhangs in the ultimaker robot (included on the SD card that shipped with Ultimaker 2):

Can anyone suggest what may be causing this problem?

Much appreciated!

Josh

 

[personal-drones 44]

The default quickprint high quality settings are not the best for dealing with overhangs. To get better results may I suggest you start from the "normal" quality in quickprint (layer height will be 0.1). Then switch to full settings and click yes when it asks if you want to carry over the settings.

Then you need to lower the print speed.

Go in the "Advanced" tab and set the infill speed and inner shell speed to 40 and the outer shell speed to 30.

These changes alone will yield much much better overhangs.

For an even better performance you could do infill 40, inner shell 30, outer shell 25.

The slower you go, the more you can lower the print temperature. So if you go slow you can also try to reduce the temperature from 210 to say 200-205. This also helps with the overhangs.

 

[yellowshark 153]

I have no idea what the settings are in High Quality Print but you also need your fans at 100%. This is sort of a guess but given the small size of the overhangs I am not sure that keep changing the print speed is going to help. Every time you do that you will get a change in pressure in the feeding system which will lead to short bursts of under and over extrusion. Personally I would go as slow as you need to get the finish. Sure try 30mm/s but be prepared to go to 20mm/s, which I think will remove any jerk too.

 

[yellowshark 153]

Oh and difficult to assess the size of the item but you might need to print two up concurrently to get a required minimum layer time

 

[gr5 2,173]

Everything the posts above say is basically all you need to know. Quick summary:

- Fan is incredibly critical for overhangs - make sure the 2 side fans are working ( they might come on slowly).

- Printing cooler helps a little with overhangs - 210C should be plenty cool enough though.

- Printing slower helps with almost every quality issue including these blobs.

Bed temperature is irrelevant to this issue once you get about 3mm above the bed.

 

[jsanders 0]

Thanks for the advice, guys!

I tried to build the model from .stl with Cura, instead of using the gcode (preconfigured with temperature changes).

I used the following settings:

-"Normal" in quickprint, then sent preferences to advanced mode

Basic

-Layer height: 0.1mm

-Shell thickness: 0.8mm

-Bottom/Top thickness: 0.6mm

-Fill Density%: 20

-Print Speed: 50mm/s

-Support type: None

-Platform Adhesion type: Brim

Advanced

-Nozzle size: 0.4

-Initial layer thickness (mm): 0.3

-Initial layer line width (%): 100

-Cut off object bottom (mm): 0

-Dual extrusion overlap (mm): 0.15

-Travel speed (mm/s): 150

-Bottom layer speed (mm/s): 20

-Infill speed (mm/s): 40

-Bottom/Top speed (mm/s): 15

-Outer shell speed (mm/s): 25

-Inner shell speed (mm/s): 30

-Minimal layer cool time: 10s

Cooling fan: enabled

Here's the result (the partially finished one on the right):

 

It's a huge improvement - far fewer globs and smoother surfaces.

But I know ultimaker can do better than this.

Any ideas?

 

Thanks,

Josh

 

[Labern 774]

Orientation can be important with overhangs like this. You will notice that one of the fans blows closer to the nozzle then the other. Rotate the part so the overhangs are on the side which has the fan closest to the nozzle. Also, what are the Temps you used?

Some of those default speeds vary alot, this restricts how much you can lower the Temps. Pretty much the slower and colder you go plus heaps of fan the better the finish you will get on overhangs

[yellowshark 153]

+1

 

[gr5 2,173]

EXACTLY what labern said. Switching speeds can cause blobs (but it depends where it happens so it might be unrelated) but keep infill same - keep all speeds the same if you want it perfect. I prefer to make infill faster but perfection is not so important to me. Slower. Colder. More fan. Different fan shroud (but some fan shrouds are *worse* so it needs to be well vetted).