Bad print results

[Biem1000 0]

Hi all,

Recently I got the opportunity to use an Ultimaker 3 in my classroom. Before I start printing with my students (6th grade), I want to familiarize myself with printing and slicing. And since I DM for our D&D group, what better than to print some enemies?

I have some limited experience with 3D printing, but the problems I encounter now are too much for me to fix. As you can see in the attatched images, I get a lot of spaghetti and overall bad results. The Ultimaker 3 printer is used by a lot of other teachers so maintenance was probably not really number one priority. So firstly I did hot and cold pull. My supports with PVA were really bad so I bought a new spool of filament (I read that moisture is really bad for PVA quality, picture no. 1 is done with the old spool). Still, my results are mediocre and I'm not satisfied with the results. 

I use Ultimaker Cura 5.6.0 with fine settings (0.1mm), retraction on and with prime tower. What settings could I try to get better results? 

[gr5 2,224]

Printing PVA is another whole learning curve.

 

Yes, PVA can get water in it and it only takes a few hours on the back of the printer.  Certainly a week on the back of the printer and it has completely absorbed water.  I don't think this is the problem in your final print but we have to talk about it.  It's not ruined - you just have to dry it.

 

When storing PVA I use a 2 gallon (8 liter) zip lock bag for each spool and about 1/2 cup (1/8 liter) of desiccant per bag.  Get color changing desiccant (buying a liter of desiccant is quite cheap).  Sometimes you can get 2 spools in one bag.  The desiccant needs to be recharged when it changes color which for me is once every month or so.  I do it in a paper towel lined ceramic bowl and put it in the microwave for a minute or so and then let it sit out and cool for 2 minutes and repeat about 5 times until it stop getting lots of condensation.

 

To dry PVA, unspool enough for the next print (cura shows you this amount in the bottom right corner) and sit that on the heated bed with the spool on top and cover the filament and spool with a towel (or similar).  Heat the bed to 55C (if you go over about 75C you will soften the PVA too much and deform the portion touching the bed).  Leave it like this for at least 3 hours - I like to do overnight to get much of the still-spooled filament but usually just 4 hours is plenty for the unspooled portion.

 

This is the ordeal with using PVA.  Having said all that I don't think your issue is with the PVA this time but perhaps it was in the first photo.

 

Please post your project file - I think we might have to tweak your support settings.  The project file will contain your model (your STL) and your machine profile, the profile you chose, and any overrides you changed.  Also the position you placed your model and how you scaled it.  Do "file" "save project" and post that file here.  Certain models need certain tweaks to get the support to work well.  PLA usually prints pretty well on top of PVA but not nearly so well the other way around and this is related to the "support horizontal expansion" parameter which helps the PVA reach a path to the glass bed.  I want to see your project file before I make any suggestions.

 

Leveling is critical - I haven't used active leveling in so long that I forget if it even does  left/right core calibration.  I do manual leveling on my UM3 (and active leveling on my S5).  When doing manual leveling you need to get the exact same pressure on the calibration card (or use an ordinary sheet of printer paper) for the left and right nozzle.  If the left nozzle is tighter when leveling, then printing PVA onto PLA will not squish as much as desired.  If the right nozzle is tighter to the paper when leveling, then the PLA will not squish very well onto a lower layer of PVA.

 

 

[Biem1000 0]

First of all, thanks for your elaborate reply!
I checked the usb-stick that I used to transfer the .stl file to my Ultimaker, so that I could post the exact file that I used. However, when I load that specific file in Cura it says 'Make sure the g-code is suitable for your printer and printer configuration before sending the file to it. The g-code representation may not be accurate.'

Because of this, I sliced it again. If I'm correct, all settings are the same as when I tried to print. In the attachment are both projects.
Also, I will do the levelling as you suggested, but that has to wait until the weekend. After that I'll try again!

1st Cura Project.3mf 2nd Cura Project.3mf

Edited February 6 by Biem1000
Pressed enter too soon...

[Slashee_the_Cow 409]

5 hours ago, Biem1000 said:

when I load that specific file in Cura it says 'Make sure the g-code is suitable for your printer and printer configuration before sending the file to it. The g-code representation may not be accurate.'

It always says that because there's no way it can 100% sure the gcode is for your printer on its current configuration. "The representation may not be accurate" has mostly to do with how Cura can't 100% accurately draw a representation of what a printout will look like, i.e. it can't guarantee that a section with low flow will show lines as wide as they will end up in the print, or if you're using support layers thicker than normal layers it'll end up drawing them as a fat layer every two layers in the preview).

 

I had a quick look at your files but since I'm not familiar with PVA or using dual extruder printers I'll leave a thorough review up to @gr5 (although I will say that I hope you can get rid of all the support around Raichu's bum or it'll be hard to plug his tail in).

 

As well as storing your filament in bags with desiccant you can also buy filament dryers - I still keep my filament in sealed bags, but before I use it, I stick in the dryer for an hour two (depends on how long I've been since I've last used it and the weather - it can get pretty damn humid here in the downunderverse). Some dryers also have openings you can use to feed filament out so it can stay in the dryer during long prints. I don't know how well they work for PVA though because my printer can't use it 😞 

Edited February 6 by Slashee_the_Cow

[gr5 2,224]

DISABLE Z-HOP

 

I saw you have zhop enabled. This causes most of your issues I think.  Certainly the stringing on object 3.  This feature is usually only used for delta printers which are difficult to describe - google image search for delta printer.  They are as similar to your printer as a fish to a fork.

 

Anyway, zhop may be your primary issue in all the prints.

 

 

In the first photo above we have 2 objects, second photo 1 object, 3rd photo 2 objects. I'm going to number them:

1 2

  3

4 5

 

I was most curious about object 4.  You didn't send that file.  object 2 looks fine but it's hard to tell as this before you soak it in water.

 

Object 1 failed I assume but I don't know what it is supposed to look like so can't comment.

 

Object 3 has an insane amount of stringing.  As though you didn't do any retraction.  The file you sent me does retraction (light blue moves are retracting moves in PREVIEW in CURA, dark blue are non-retracting moves).  So I think you probably had retraction yet it still did stringing like crazy.  Are you sure this is PLA?  

 

I think you should just slow it down a bit.  Or more importantly have consistent speeds.  So if you type "speed" in the settings search box it pops up about 20 settings.  Set the first 8 all to be 35mm/sec (nice and slow).  And I think you will get better results on those 2 hammers (if that's what they are).  You want all the printing speeds to be slow and travel speeds to be fast (>150mm/sec) to minimize pressure in the nozzle and hence leakage and fast travel speed to minimize leaking strings.  So: print speed, wall, infill, skin, top, bottom, prime all should be 35mm/sec.  I'd increase initial layer speed to 20mm/sec.  10mm/sec is crazy slow and not necessary.

 

Object 4 is the most intriguing to me - it came out so bad - something obvious must be wrong.  Possibly just the zhop issue but I wanted to see how the support is placed

 

3mf files

 

Every time I print something I save the project file both so I can go back to see what I did years later and also to be able to use the same settings I did on a previous print.

 

Object 2

 

This model is not designed well for 3d printing.  The ears alone - there is no way to print that curl and they get so thin they aren't printed at all at some point and it looks kind of ugly in PREVIEW.  I suspect the person who designed this never tried to print it.  They probably don't even own a printer.  This is a challenging model to print.  It can be done but easier after you've done a few hundred prints yourself.  I wouldn't start with models like this.
 

enable prime tower

 

If you are printing with pla and pva, I recommend you enable prime tower - at least for prints that you want to look nice like these.  My prints can usually be ugly as they are meant to be functional, not interesting or pretty to look at.

 

In the first 3mf file you sent me you had support set for material 1 instead but your print had it set to material 2.  No big deal - I just changed it but it makes me slightly concerned there were other differences.