Optimal settings for detailed prints.

[Lodden 1]

Hello!

I work at an architecture office, and we recently invested in an Ultimaker S3. 

When making 1:200 models, we experience a lot of stringing, especially between collumns and in doorways. I have started to experience with retraction and retraction speed, and the results are getting better, but far from perfect. 

Are there some good standard settings for retraction, retraction speed, and heat(maybe something else?) when making small detailed models?

 

I am currently using PLA for models and PVA for support. 

 

Thanks in advance.  

 

 

[gr5 2,224]

PLA is usually pretty good about not stringing.  Unlike some other materials which need to be dried to avoid the stringing.

 

Are they extremely fine hairs that are hard to see?  Those are the hardest to get rid of by messing with settings but the easiest to get rid of after the print is done.  I get rid of most of those with a flame.  I use a butane torch - around $10 on amazon.  I give the strings a quick swipe covering maybe 5 inches per second so each spot gets only maybe 30ms of flame.  No.  Faster than that.  Maybe 15 inches per second.  The fine hairs are then gone.  If you move the flame too slowly you brown or blacken the pla.

 

You shouldn't get thicker strings.  Those are more likely for larger nozzles (so stick with 0.4mm if you want to get rid of them) and they are more common if you are printing faster.  For a really beautiful print I set all the speeds to 35mm/sec (infill, inner, outer walls, bottom, top speeds). But leave the travel speed as fast as possible.  300mm/sec travel speed is probably reasonable - I don't usually go that fast but it should help the stringing.  If you go too fast then you will miss a step on the stepper and the whole part will shift on some layer.  But 300mm/sec should be fine if you keep your rods oiled - just one drop only about once per month on the 6 rods in the gantry.  Any light mineral oil is fine.  3-in-1 oil.  Sewing machine oil.  Any mineral oil.  Even baby oil is probably okay.  wd-40 is not great - it's meant for cleaning - not so much lubricating.

 

Higher printing speeds means higher pressures in the nozzle.

 

I wouldn't mess with retraction speed or distance but if you mess with the distance:  The distance should be the right amount so that the filament is no longer pressurizing the nozzle but not enough to actually pull upwards and allow air into the nozzle.  So if you look at the bowden at the top of the arc while it's doing the retractions you can see the filament come down and rest on the bottom of the inside of the tube - it's easier to see what I mean if you watch it happen.  But if you look down where the filament enters the print head it should never move upward on a retraction.

 

Check your bowden to make sure it is not loose - pull up on the bowden and it should not move up.  Both at the head and the feeder.  If it does then it wasn't inserted properly - remove the horse-shoe clip - push down on the outer collet and then push down on the bowden and then while pushing down pull up on the collet and then insert the clip.  The bowden should not move up and down.  If it does you can add that movement to the retraction distance.

 

Did you mess with any other settings?  Lots of things can make it string - I'd stick to the profile where possible.

 

Lower temperature can also reduce stringing.  Some print as cold as 180C.  I use the default temps in the profile.

[MariMakes 204]

Hey @Lodden,

 

Welcome to the Ultimaker Community 🎉

Is there a chance that your doorways are placed less than 4mm apart?
For thinner models we've seen that they needed to be 6 mm apart before getting retracted. 

These dark blue travels indicate unretracted moves: 

 

We've seen that these tiny travels are not retracted in the more recent versions of Cura, eventhough we would expect them to be. We concluded that you can restore the retractions if you disable the setting: Limit Support Retractions

We actually plan to remove the setting in the next version of Cura, so the moves are retracted again. 

 

Was that the kind of information you are looking for? 
Would you be comfortable sharing a picture of your printed part quality?
That helps with troubleshooting. 😉

[Lodden 1]

Thank you for good responses. The gaps are indeed less than 4mm. 

This model was printed with recommended settings. 

[gr5 2,224]

If you look in PREVIEW mode at your sliced model in cura, set the view mode to "line type" and make sure the "travels" are checked (blue).  The travel moves come in two colors - light blue and strong/saturated blue.  Light blue is a retraction move.  darker blue (as shown in MariMakes photo)  is non retracting.  There are quite a few settings that can control which type is chosen so if you have this problem again, check the blue colors and then look at all the retraction settings.

[Lodden 1]

Thank you @gr5.

The Limit support retractions seems to be disabled by default, so unfortunately that doesn't solve the problem. As you can tell from the image, there is a lot of stringing. Is light blue then preferable? Do you know how I can make the small (>4mm) gaps in to retraction moves to prevent stringing?  

[gr5 2,224]

In cura, above the settings, there is a search box.  Enter "retractions" and there are various minimum and maximums and such.  I'd play with those until it's light blue.

[Lodden 1]

Perfect, the travels were new to me.

Thank you!

[gr5 2,224]

Yes.  Dark blue has no retraction and will string.

 

Dark blue travels are normal and fine for *inside* the walls of your building but those that span an air gap in a window or doorway you want light blue.  In certain cases you also want to disable retractions inside an "island" as cura thinks of it.  Inside of a wall in your case. Those are controlled with "combing" but I think you want to ignore combing because your issue is across gaps (windows/doorways).

 

 

[Lodden 1]

Hello again! 

After trying a couple of different settings, I still get dark blue travel lines in some doorways. Are any settings more useful than others in trying to eliminate these? can it be because the collumns on each side are to thin? 

 

 

[gr5 2,224]

Indirectly, yes.  I think it's:

 

maximum retraction count

 

This prevents you from doing so many retractions in the same spot of filament that you grind the filament to dust.  I think it defaults to 25.  Try increasing it to 100.  If you get a print failure where the filament is ground down and the feeder stops feeding - and if you remove the filament you see it has a big bite taken out of it - then you set that value too high.  You could reduce the feeder pressure a little but that might make grinding worse in other sections of the print.  I suspect if you only increase the 25 to 100 it will be fine.

 

In other words, the printer likes to advance the filament X mms before retracting more than Y times.  The defaults I think are 1mm and 25 retractions.  So if you do more than 25 retractions on the same 1mm of filament the software says that's the limit.  Y is the bold setting above.  X is the bold setting below.  Only mess with one of these settings.  Either increase the one above or decrease the one below.  Don't do both.  I would just mess with the one above but I'm showing that they interact for a fuller explanation.

 

minimum extrusion distance window

 

Alternatively, you might not want to mess with this setting and just live with a few non-retracting travels.  Personally I'd increase it to at least 50.

 

 

[Lodden 1]

Thank you again for a good response.

We turned off combining, and increased maximum retraction count to 100 to solve the problem in cura. We are crossing our fingers for it to work in the physical print as well! 

[gr5 2,224]

If this works great for this print.  And the next.  And the next.  But then a few months from now you have a print that keeps failing - remember that you set this to 100 and maybe lower that back to 25 just to see if it it's grinding the filament to dust at one particular spot when you actually have 100 retractions in just 1mm of extrusion.  You can indeed get this when you have tons of tiny islands like when printing the legs of the eiffel tower - there are many hundreds of tiny tiny girders and each one is a tiny point on a given layer.

 

I suspect 100 is safe enough but I really don't know where the problem occurs.  If my memory is correct (and it was like 10 years ago) I was able to do 60 retractions safely per mm but 120 retractions was too much.  but that was a different feeder (on the original UM2) and may grind filament more.  Or may grind filament less.  than the S5.

 

I do remember that I used "grep" to count how many retractions I had and it was something like 2 kilometers of retractions!  In one 18 hours print!  Wow.

[libertyhouseplans 2]

Hi, @Lodden. I work on architectural models, too. PLA as my main filament. I favor ColorFabb Semi-Matte White for my primary filament. It has a similar luminance to foam core and isn't finicky. You can order directly from ColorFabb's website, and if you order enough, delivery is free and fast. (Netherlands to NYC in 3 business days.) Their Vibers White filament is also nice for a wood look.

 

When I first started, I worked with ColorFabb's Woodfill PLA and got a lot of stringing. Reducing the Printing Temperature made the biggest difference. You might try that if the suggestions above don't work.

 

You can test whether Printing Temperature is part of the problem by making a small model of just the problem area and printing it repeatedly — reducing the Printing Temperature by 5 degrees each time in your Cura settings. (There are other ways to do this, but you get the idea.)

 

Once I got a printing temperature that worked well, the Speed settings made the biggest difference for me. I get no stringing between outer walls with the slower print speeds I use, but I do see some stringing in the infill area where there are fast travel moves. I don't worry about it b/c it's not visible; I just take it as a clue that Travel Speed can be implicated in stringing.

 

Here are my speed settings, in case it helps. I'm using a 0.4 nozzle and 0.2mm layer height. At that point, the layer lines are invisible when viewing a model at arm's length. Hope this helps.