Print quality issues with overhang

[mightybhwk]

Hi all,

I am starting to print out the pieces to the mostly printed CNC machine on Thingiverse and i am having some issues.

http://www.thingiverse.com/thing:724999/#files

Pictured below is Corner_Block2 and as you can hopefully see the overhang looks terrible. I've tried adjusting the temp up and down and slowing the speed. Nothing seemed to help. It looks like this on any inclining section.

I've had this issue on other pieces using different filament so I don't think it's that. I am using Makerware not sure if other software would be better. I could try supports but I don't think it should be needed.

Any suggestions?

20160127_073632.jpg

Here's what I used:

Times printed: 4
Printer: FFCP
Filament: Sainsmart PLA
Shells: 3
Infill: 40%
Software: Makerware
Speed: Default in makerware (The one pictured was at 90% in sailfish firmware)
Temp: 220 down to 205.
Active cooling: on 3 out of the 4.
Orientation: Default when preparing it in makerware. (Thought maybe turning it may help)
Resolution: .25

Thanks,

Randy

[djprinter]

Change the orientation, if you rotate it onto the other side you have a less steep overhang which will print better. The overhang you're trying to print is 45 degrees which is at the outer limit of what is possible. Rotate you only have about a 35degree overhang.

Printing on the other side will also remove the 90 degree support requiring overhang on the other side of the part.

[Sebastian Finke]

You could always try using support material. PVA works well with PLA from what I have read...

[curious aardvark]

okay three things :
1) NEVER use default settings in makerware. They print and move the printhead Much Much too fast.

2) for anything that needs to be structurally strong always use at LEAST 3 shells and layers (shelld are the outside and layers are the top and bottom) For parts of a cnc machine I'd probably use 4-5 shells and layers. that way you can drop the infill down to 25% and still have a stronger - but lighter part.

3) do you have active cooling fitted on your machine that blows on the area being printed ? This miraculously improves overhangs, underhangs and any curved or slanted surface. Always have iot on for pla - hell I always have it on for ANY filament type :-)

And yes you could also improve prints by buying simplify3d. Because of the way it slices models, curves, overhangd and underhangs print sharper and cleaner.

Also printing at resolution of 0.2 won't slow things dramatically but will give better angled printing.

Speed wise you need the actual printspeed to be between 40-60 mm/s and the travel speed to either be between 50-90 - OR the same speed as the print speed.
Having it the same as the printspeed cuts down on sudden changes of speed and direction which can pull the filament and cause 'spikes' that catch on the extruders.

The standard makerware settings are always much much too fast for any clone machine.

And has been said - print orientation is crucial - both for ease of printing and strength of final part.

Also try 210 for your pla. It's hot enough to give great layer bonding but cool enough for sharp precise prints.

[mightybhwk]

Thanks all for the quick responses.

I am going to talk a look again at rotating it. At first the angle looked greater than 45° so I thought it would be ok.

I haven't used PVA yet. Still fairly new.

I did use 3 shells. Don't know why I wrote 2. As for the infill, I was following the designers suggestions.

http://www.vicious1.com/blog/parts/

I do have active cooling (one of the first things I ever printed) and had it on for all but one. http://www.thingiverse.com/thing:537918

I usually print almost everything at .2 but his suggestion was .26

I will need to look at the speed settings when I get home. But I will slow it down. Still a little hesitant on changing the settings and what they do. Still learning.

Overall, I believe the part is still usable. I'll find out once I put it all together.

Thanks everyone for all the suggestions.

[curious aardvark]

well on makerware unless you want to slow the first layer down - pretty much just change the basic settings: temperature, layers, speed, resolution, extruders.

Pretty self explanatory really :-)

Makerware call it 'advanced' - it's not. That's reserved for editing the profiles :-)

[jfkansas]

.2 is where you want to be. As you approach .3mm layer heights you start having volumetric flow and squish issues. It is good to keep at least a 2:1 ratio between layer height and nozzle size. For example to do the .26 layers you should be doing it with a .5 or .6mm nozzle.

[mightybhwk]

I have gone back to printing everything at .2, slowed down the travel speed, and slowed down the inner and outer shell speed. (forget what makerware called it.) Also I increase the shells from 3 to 4 but kept the density high.

I have increased the temp from 205 to 210 but I'm noticing some warpage on the bottom of the prints. I read that with the increased density also brings increased heat retention. Which leads to warpage in pla. I'm trying to bringing the temp back down a bit to see if that helps. (My bed temp is 65°)

I haven't tried to reprint the piece in the pic yet but the overhang on the other pieces does look better.

Your suggestions have helped a lot.

[curious aardvark]

if it's warping with pla - it's not stuck to the bed well enough.

Try glue stick :-)

Can be a bastard to get prints off. So waht i tend to do is just heat the bed and you can usually wiggle a scraper underneath once it's softened a little.

And seriously 25% infill with plenty shells is just as strong as 40% - still a pretty dense matrix. But prints faster and shouldn't warp as much. Or at all if it's stuck to the bed properly :-)

[mightybhwk]

I've never had this issue before with PLA warping. I use Aquanet on a glass bed. Cleaning with IPA after each print.

But I never had done long prints (4-6 hours) with 60-70% density. I've gone down to 205° and left a small desk fan running by the printer. I haven't had an issue since then.

Here is picture of one of the almost completed roller assemblies.


20160202_074846-1.jpg