Help on printing thin supports (Meshmixer style, UM1)?

[johanw 0]

What are your experiences -- and recommended settings -- printing thin supports on the UM1?

I'm trying to print a cellulose molecule from a model that has thin support beams: http://www.thingiverse.com/thing:301575

I feel I'm getting close. Many parts of the model come out with sufficient quality. However, after five tries I still can't quite get through the print. Some supports always get knocked over, resulting in lots of plastic spaghetti (see pictures).

I've been reading the http://www.extrudable.me/2013/12/28/meshmixer-2-0-best-newcomer-in-a-supporting-role/. Seems like the UM2 is the machine of choice there. Is it worth trying to do similar things on the UM1?

These are the settings I used for the print in the pictures, after some trial and error.

- Layer height: 0.1 mm

- Shell thickness: 0.8 mm

- Filament: off-white PLA, from Ultimaker

- Temperature: 190 C. (It's possible to print at 180 C, but then the filament is so sticky it hardly moves during retraction)

- Speed: Print speed 20 mm/s, Travel speed 150 mm/s

- Combing: Off

- Retraction: On

- Speed 40 mm, Distance 5 mm

- Minimal extrusion before retracting 0.01 mm (i.e., always retract as you move from pillar to pillar)

- Z hop when retracting: 0.1 mm (should this be increased, perhaps?)

About the breaking pillars: They tend to break below the base, but sometimes they break somewhere higher up. I have checked that the model gives two circular passes for each layer. In fact, the quality of the pillars varies a lot, with some coming out really well and others full of warts.

Clearly it would be possible to change the model here, to make the pillars more sturdy and so on. I still think it's worth trying to figure out how to make the print as it is. Looking at the result so far, many parts do come out really well.

What do you think, can the UM1 handle this challenge? Maybe someone can spot what I'm missing?

 

[pm_dude 27]

Looks like your using raft. If you are try using brim instead or put the air gap to 0. You want those supports to be super tight o the build plate.

In Meshmixer there is a setting for the base of the supports. The one that touch the build plate could have a way bigger base.

Having Combing off add a lot more retraction while it may not need to. The ZHop is good but if I have read properly in the forum there are a lot of indications that the z screw on the UMO is not really precise unless you have the new build plate upgrade. Maybe you should remove zhop.

Good luck

 

[johanw 0]

Many thanks for these suggestions!

Re. making the supports stick: I forgot to mention that I had already set the air gap to 0 here. I have tried using brim, but actually found that to be less sturdy than the raft. The brim comes out with just one layer, which isn't very solid. I agree that the 3D model here could really be improved. For one thing, the supports are much taller than necessary. Then again, that's the challenge

As for the z-hop: My machine is from 2012, with no build plate upgrade, so indeed that might be a problem source -- imprecise repositioning in the vertical. As far as I can tell, the results are still somewhat better using z-hop than without.

My hope is to find some sweet spot of settings that will allow for the print to go through. I'll try some variations and post updates I make any progress.

 

[johanw 0]

Ok, here's an update after another attempt.

I edited the model (which is not actually flawless, having lots of little holes etc.) in Tinkercad, to make the support beams a bit shorter. Then I changed to 0.2 mm layers and z-hop of 0.2 mm. Following pm_dude's advice, I put combing back on.

Good news is, this printed with only a single support breaking off. Following the print inbetween cooking dinner, I even applied a little superglue to put that broken part back on, resulting in a molecule print that is at least usable for its chemistry teaching purpose. It will have to be painted in color, after all, so tiny errors are acceptable.

However, I also had a surprise:

- I cut out a detail of the model that looked particularly prone to failure, containing just four beam supports. The result was a really good print, with straight pillars and great detail. But,

- printing the entire model, which has 40 support beams, many layers are displaced horizontally, giving really ragged edges and a much lower quality overall.

It seems that my printer can't cope properly with precise repositioning when the extruder needs to move across a long distance. Surprisingly, the columns at the outer extremes of the print -- far left, far right, back, front -- are smooth and precise. The ones in the middle are ragged and rough.

I'd of course appreciate any hints as to why this is happening

(New images of the latest print + the detail cut-out with good quality, added to the album:)

 

[pm_dude 27]

That is a great improvement!

You can probably play a bit more with retraction settings to see if it can help to reduce the small blobs here are there.

For the support that have shifting layers this could be due to loose belts. Make sure they are all tight.

http://support.3dverkstan.se/article/23-a-visual-ultimaker-troubleshooting-guide#leaning

Otherwise it could be due to acceleration being too high and its now stopping to far. On the UM2 the acceleration settings are on the LED control. I don't know where they are on the UM1. Mine have been reduced from 3000 to 1000 for x/y axis.

You can post the picture directly instead of posting the album. This way we dont have to look for which picture your posts are referring to.

 

[johanw 0]

Yes, I feel I'm learning something here -- thanks a lot for the further suggestions. I will certainly try them out as soon as possible. This is helpful advice, easily tested on my machine.

I thought the belts were ok, but I guess these pillars are much more revealing than the boxy things I've been printing before.

Tbc.. (will look into the picture posting too)

 

[johanw 0]

Success! I made some very minor changes to the setup, and finally the print went through with all pillars intact.

(I also tightened the belts on my UM1 a bit, but believe that that didn't make a lot of difference here.)

 

 

Here's my settings in Cura, in case others would like to try a similar print.

- Layer height: 0.2 mm (impatient)

- Shell thickness: 0.8 mm

- Top/bottom thickness: 0.8 mm

- Fill: 10 %

- Filament: off-white PLA, from Ultimaker, set to 2.90 mm diameter

- Flow: 90%

- Temperature: 190 C. (I tried 185 C, but 190 seems better)

- Support: Raft, with air gap at 0 mm

- Speed: Print speed 20 mm/s, Travel speed 150 mm/s

- Combing: On

- Retraction: On

- Minimum travel 2 mm

- Speed 40 mm, Distance 5 mm

- Minimal extrusion before retracting 0.01 mm (i.e., always retract as you move from pillar to pillar)

- Z hop when retracting: 0.2 mm (tried larger values for no discernible effect)

 

[johanw 0]

PS. The problems with horizontal displacement certainly remain in the print. I would like to look into acceleration settings, as pm_dude suggested. (Requiring a firmware change? Will need to investigate that..)