Rough edges on overhangs

[samhenderson27 0]

Hi there i am after some advice on printing this piece. It has a really steep angle and i am not sure if i will be able to print it or not. Take a look at my test piece which didn't go so well.

Maybe i just need to get the temperature and speed just right?

Using UM2 with Ultimaker PLA

Many thanks.

 

 

 

 

 

[pm_dude 27]

Hi Sam,

Can you provide a bit more info about your print settings? Speed, layer height, nozzle temp.

Try printing slow and at low temp. With a layer height of 0.1mm and speed of 30mm/s you can put the temp around 195-205C.

If you have the default UM2 fan mount I suggest you turn the model 180 degree so the overhang part get better cooling (the left side cool bethe than the right side).

[gr5 2,172]

You have an incredibly steep overhang there on the edges. The UM2 can handle it fine but it's "ugly". Typically perfect (visually) overhangs can only be up to about 45 degrees. Is this your design? Can you change the angle overhang on the sides? Certainly more fan helps - make sure the fan is at 100% before it gets to the overhang. But I think you may already have that.

 

[samhenderson27 0]

Hi guys,

Thanks for your reply. I had it printing at 215C as i have been having trouble with the PLA under extruding at any lower temp. I had the speed at 50mm/s and a layer height of 0.1. As you suggest, i will try slow it down and lower the temp as well, perhaps even print with a 0.06 layer thickness. The fans are at %100 after 2mm.

I understand it is a very steep angle (around 30 degrees) - yes it is my design, i could change the angle but then the part wouldn't really be fit for purpose unfortunately.

Im thinking i may have to split the part into 3 individual pieces and lay the sides over 90 degrees so the slots face upward.

 

[yellowshark 153]

Personally I would have approached that piece wanting to print vertically rather the horizontally. If the other side is the same as the facing side then I would just slice one side off and stick the two parts together, or maybe just slice it down the middle. Probably strength and visual looks requirements may determine if the approach is suitable. Actually I am starting to suspect that those sloping planes are also sloping inwards so a slice down the exact middle to get a flat printing base may be the better option

 

[gr5 2,172]

Im thinking i may have to split the part into 3 individual pieces and lay the sides over 90 degrees so the slots face upward.

How will you attache the 3 sides? Glue? Melt?

Try sticking some 3mm filament into some hot water (boil water in microwave first - then insert filament for 10 seconds) and then bend the filament as it cools.

Now consider printing the entire phone case flat and then heating it in hot water and bending it around your phone. This is how Aaron made his glass frames - he printed them flat, then heated them and curved them to fit his face. I've seen this done with 3d printed clothing also. A jig might help also with the glueing/melting/bending phase. Perhaps made out of ABS, UPET, XT, or Nylon so it can withstand higher temps.

 

[8BitKid 0]

I'm also experiencing an issue where the upward sloping planes are rough.

Does anyone know why this would occur when printing with "Low Quality" but does with "Ulti Quality"?

[gr5 2,172]

Photos of the 2 different prints please. Layer height, print speed, fan speed, nozzle temp and brand of PLA make a difference on overhang quality. In general you want to print slow, cool and with fans at 100%.

[8BitKid 0]

The one on the left was printed with:

Layer height: .15

Print speed: 60

Fan speed: 100%

Nozzle temp: 210

The one on the right was printed with:

Layer height: .06

Print speed: 60

Fan speed: 100%

Nozzle temp: 210

Both were with Ultimaker's green PLAN

[gr5 2,172]

Nice. I recommend you move your glass closer to your nozzle. Simply turn the 3 leveling screws about 1/3 turn counter clockwise from below. Stay away from the automated procedure. I say this because your bottom layer is a bit underextruded due to nozzle being too far from glass. The rest of your print of course is unaffected. If you don't do this your parts won't stick well either.

[gr5 2,172]

I really love this color by the way.

[8BitKid 0]

Thanks for the advice and compliment!

As someone who is relatively new to the world of 3D printing, can under-extrusion cause the overhang roughness?

I've been testing today, and found that if I print on a raft I can bring the temperature much further down (currently at 180), which helps dramatically. I've also slowed the print to 15.

When I tried similar settings with a brim, the model would get proper adhesion to the bed, which is why I switched to the raft.

Edited June 14, 2016 by Guest
wrong details

[gr5 2,172]

Raft is old technology. You shouldn't need it anymore. The 3d community mostly stopped using rafts and have moved on to better. But for a few years it was the best we knew how to do ABS.

I've never heard that underextrusion hurts or helps overhangs. Certainly these green lizards don't look underextruded. There is a huge discussion on why overhangs don't print well and do strange things while printing (they lift up) along with great slow motion video but it will take you a long time to find all the jewels of information among the bad guesses of whats going on:

=========

What causes raised edges and crappy quality on overhangs.

http://umforum.ultimaker.com/index.php?/topic/4094-raised-edges/

Skip right to "page 2" and look at foehnstrum's video and read all the posts after that possibly. It's not until around post #39 and later that we really begin to understand what causes the issue.

The problem has to do with the fact that liquid PLA is stretchy like melted mozzarella cheese or like mucus. The liquid plastic is pulling like a rubber band as it goes down and creates a lip or raised edge where there is an overhang. The effect gets stronger on each succeeding layer. It is what causes the lower quality "look" of overhangs. Sometimes the part will actually rip free from the bed because of this (which is easily fixed by making parts stick like hell - another topic).

[StephanK 30]

Reminds me alot of the problem I was having with the bow of my benchy with some PLA, incl. the Ultimaker Silver one that came with the printer or the bright green from Innofill - but not with other brands of PLA.

I managed to make it go away by:

 

a) printing hotter (220-240 instead of 200-210)

b) or increasing layer heights (problem did not occur at 0,2mm, but does occur at 0,1mm) or

c) using some other manufacturers PLA