Rough surface

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Legion 2.3
Posts: 84
Joined: Sun Apr 20, 2014 6:23 pm

Rough surface

Post by Legion 2.3 »

Dear community

I had some problems with a rough surface at some prints i did recently.
As you see on the picture, the surface is rough at some (random?) spots, not only at overhangs (even if they appear there more often).
20140712_193354.jpg
It only seems to appear at more organic-like prints.

Am I the only one who has these problems? Do you have any ideas how to fix that?

- printed at ~190°C
- extra 120mm fan pointing at heated bed (switched off in the middle of the print, no difference)
- colourfabb pla/pha

cbensch
Posts: 54
Joined: Fri Jan 24, 2014 9:52 pm
Location: Simsbury, Connecticut US

Post by cbensch »

That's a neat print! I have a few thoughts here:

1) Am I safe to assume you don't have a filament filter in place? If prior prints printed well, it almost seems like maybe you're having dust issues. With dust in your extruder you'll have low flow rates when compared to your speed as a lower volume of filament gets pushed out of the extruder. I use the below filter stuffed with air conditioning insulation (this sheets made by Duck available at Walmart) and it works wonders since filament is naturally charged with static: http://www.thingiverse.com/thing:190118

1B) Just adding the filter isn't enough. You have to clean your extruder. If you don't have a .3mm drill bit (.35 scuffs the extruder walls too much) then crank up your extruder temperature to 240 and loosen your tensioner. Force about 10 inches of filament through to clean it out.

2) Up your temperature a bit. I lay my first two layers at 220 (both solid) then the consecutive layers at 210.

3) Slow it down. I recall reading somewhere that the fellers over at Felix recommend 30-40mm per second for the highest quality prints.

4) Consider your z-lifting settings when the extruder is traveling to new layer points. Don't go too high. .2mm is sufficient if you're using it at all.

5) Don't do what I did and buy cheap filament. There is a lot of quality filament out there but eBay is not the place to get it unless it says it's made by a reputable manufacturer. If you're in the US consider Makezine's PLA. The stuff is awesome. http://www.makershed.com/products/1-75m ... filament-1

cbensch
Posts: 54
Joined: Fri Jan 24, 2014 9:52 pm
Location: Simsbury, Connecticut US

Post by cbensch »

Delete #5 above. I checked Colorfabb and see they're in the Netherlands and seem to produce quality products.

Something to consider however about the filament. I too have had issues with a tan PLA even when it was quality stuff. The best prints come from the darkest PLA colors as the process of creating polylactide acid naturally turns the material dark. Black, dark browns and dark grays apparently print the best.

Legion 2.3
Posts: 84
Joined: Sun Apr 20, 2014 6:23 pm

Post by Legion 2.3 »

Thanks for the fast response.

For #1:

I used the filament filter that´s delivered with the V3 DIY-Kit (I mean these small cleaner disks), i never printed without them. After the filament leaves the filter, it directly enters the teflon tube until it reaches the extruder, so there is no spot were dust could reach the filament.

Furthermore, it´s not the whole print that´s rough, only some spots.
If it´s a flow rate problem, wouldn´t it be visible on the entire print?
It only seem to appear at more complicated shaped spots, even if they´r not overhanging.

Nevertheless, i´ll try the trick with the high-temp cleaning. I don´t have the necessary drills.

For #2: I get stringing problem at higher temps, that´s why i prefer lower temps.
I´ve read in the manual (or somewere in the forum, I´m not sure) that you shouldn´t print pla hotter that 200°C or it would decompose and could clog the nozzle. So i´m a bit confused at this point.
I prefer to print at 0,1 mm layer height, I thought a lower temp should be better because there´s less filament extruded.

For #3: I use Simplify3d to slice, my main printing speed is 80 mm/s with 40% underspeed for the external shells, so i have only 32 mm/s for the outermost shell. I think that´s not too fast at all.

For #4: I´m currently using 0.4 mm z-lifting. I did this because i had curling issues a while ago and if the z-lift is too low, the nozzle could collide with curled up edges which makes it worse.
Could you explane how the z-lifting-height affects the print? I don´t really comprehend how this value affects the print quality.

For #5: I had this issue with other filament, too (bronze FormFutura PLA).

Maybe the temps are the right track, but i worry a bit because thought >200°C is too much for PLA.

cbensch
Posts: 54
Joined: Fri Jan 24, 2014 9:52 pm
Location: Simsbury, Connecticut US

Post by cbensch »

Lots of good input here.

Not all PLA is the same of course. The stuff I use by Makezine/Makershed seems to do best at higher temps. I also found more often than not I would have issues with the z lifting (not filament specific). In my experience, since the lift separates the extruder from your print you'll lose just enough of filamnt flow on each new layer or extruder movement to cause problems. It seems that in the time that it is lifted, enough filament drips out of the extruder for the filament feed to delay just enough where I'd have several millimeters of a layer with no filament or for that matter, a glob from the "drip." Repeat that enough times and you can see where I'm going. The caveat here of course is that lower temperatures shouldn't make the PLA liquid. It should be more jelly-like and not drip. But if a filament brand requires hotter temps for better adhesion to the prior layer then it just may drip a bit. :roll:

It almost seems like your print has the slight "too much filament" look to it in the delicate spots. Could it be the z-lift? Sure. Could it be the temperature? Possible. Your speed seems spot on so I'm not really worried there.

What is your infill (honeycomb etc.?) and what percentage is the infill?

cbensch
Posts: 54
Joined: Fri Jan 24, 2014 9:52 pm
Location: Simsbury, Connecticut US

Post by cbensch »

Almost forgot - how many exterior shell layers are you printing? I experimented with this on delicate prints quite a bit. I found that two exterior shells provided a stronger barrier between the outside of the print and the infill. Regardless of what you're using for an infill that extruder bounces off that wall many times and you'd want a little distance between the infill layer and the outside wall.

2) Are your belts tight? That z-wobble thing might be doing this too. They need to have strong tension on them so the print bed snaps in the appropriate direction without delay.

Legion 2.3
Posts: 84
Joined: Sun Apr 20, 2014 6:23 pm

Post by Legion 2.3 »

cbensch wrote:Almost forgot - how many exterior shell layers are you printing?
I´m printing with 4 shells and 15 % infill.
cbensch wrote:2) Are your belts tight?
Yes, they are ( at least I think they are, it already takes a little effort to move the bed, I think tighter belts would seriously damage the bearings...).
cbensch wrote: It almost seems like your print has the slight "too much filament" look to it in the delicate spots.
I´ve calibrated the extruder some weeks ago (the 100 mm-trick). Could it be that you generally need less flow for pla?
I´ll try this print with a lower flow (0.95) this weekend again, if it´s the flow, i´ll see it.
I did a small print with 0.9 flow, which was too less (poor adhesion/holes in the perimeters of a 6 mm-hole), so it can´t be far too much flow at the moment.

Here´s another print with another filament (bronze pla, FormFutura) I did some days ago:
20140716_201526[1].jpg
Maybe it helps to get more ideas what causes this problem.

190°C, 4 Shells, 15% infill

There is no Z-lift between the shells, so this can´t be the reason. The perimeters are printed inside out, if the z-lift would cause any trouble, then it shouldn´t be visible at the outermost shell, or am I wrong?

Could it be that damaged linear bearings could cause this? I did a quite large print (a larger version of this head, about 200 mm tall) a while ago, which had an entire weight of about 350 g. Could it be that the fast print moves with this load already damaged the bearing?

seaton
Posts: 291
Joined: Tue May 14, 2013 9:04 am
Location: Bunbury, Western Australia
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Post by seaton »

Try printing sone calibration pieces at different locations on you bed. I had similar problems and couldn't work it out until I printed a cibration piece at a totally different location to where I normally print. Low n behold it was perfect. Turned out that my belts had stretched/worn where I do all my prints. Replaced the belts all good
Stephen...

Felix 2.0 -> Felix 3.0 dual
Simplify3D Slicer, Kisslicer
Have you added your Felix to the Map? http://goo.gl/maps/HajnZ

http://blog.strobotics.com.au

cbensch
Posts: 54
Joined: Fri Jan 24, 2014 9:52 pm
Location: Simsbury, Connecticut US

Post by cbensch »

I'm stumped. But hose bearings are really strong. Even if you loaded up the print bed it was designed to take the weight.

On a separate note you did make me curious about printing my PLA at lower temperatures and what do you know, my prints are cleaner. I went down ten degree intervals from 220 all through 170 using the original Felix test print in their download section and each print got better and better as I went lower. 180 was the right spot for me. 170 and the layers didn't stick well. So as to increasing the temperature, I was wrong and I admit it.

Dreide
Posts: 176
Joined: Sun Sep 29, 2013 12:32 am
Location: Lausanne, Switzerland

Post by Dreide »

Legion 2.3 wrote:It only seems to appear at more organic-like prints.
In case you are using Repetier firmware and adjust the flow rate not in the slicer but via the control program, you might want to read this: http://forum.felixprinters.com/viewtopi ... 1013#p6211.
As organic-like models are probably sliced with shorter segments as compared to more technical models, the described flow rate problem might become quite relevant in your case, even if your prints seem to be relatively large.
Felix 2.0->3.0dual * Repetier (host+firmware) * KISSlicer Pro, Simplify3D * Cubify Design

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