Please help: overhangs printing badly

[slimbolino]

Hi folks,

I've been fixing someone's CubeX printer. A couple of years old. One extruder. The filament ran out after a while so rather than spend a fortune on a Cubify replacement cartridge I've chosen to set up an external reel. Now I'm using 1.75mm white PLA branded by Beeverycreative. This step led me to discovering KS (Win64_1_4_5_10 and CubeItMod491) which I've enjoyed setting up, following the tips & tricks on http://www.cubexupgrade.com

Prints are quite neat at layers of 0.2mm, except overhangs which are a real mess. I've attached some photos to illustrate. Can anyone's experienced eye suggest the factors that could correct this, please?

Overhang test piece OK with Cubify white PLA.

The following print with 3rd party filament was aborted early because the overhangs actually warp *upwards* during the printing which causes the nozzle to clash with these unwelcome raised bits, re-melt them and squish the newly laid material.

The overhangs warp upwards during printing.

I've tried changing extruder speed, PLA temperature, infill and solid %, but nothing really seems to make this problem go away.

The Ultimaker robot model looks like this! What a mess...

Overhang quality mystery (Ultimaker robot)

Any assistance you can offer will be hugely appreciated

Thanks in advance,
Slim

[Hugues]

Hi Slim,

Thanks for following my website !

I will try to help you:
Did you active your fan in material tab ? setup them to 100 in your material tab.
Your print seems a little overextruded have you check the 1 wall thickness matching to your nozzle ?
The cubex is not the best to active cooling a small part, you can try to decrease the layer height, so there will be less plastic to cool down.

Did you try to setup a really low temperature like 180° ?

[slimbolino]

Hi Hugues,

Many thanks for your help.

I have the fans running at 100%.
I have tried temperatures from 185 to 220C.
Upon your suggestion, I did run at 180C. No significant improvement
All at 0.2mm layers.

Here are the settings from KS:

KS_Style.jpg (45.94 KiB) Viewed 4489 times

KS_Support.jpg (39.59 KiB) Viewed 4489 times

KS_Material.jpg (54.92 KiB) Viewed 4489 times

KS_PrinterHardware.jpg (47.8 KiB) Viewed 4489 times

KS_PrinterSpeed.jpg (49.69 KiB) Viewed 4489 times

I will be most grateful for your expert advice!

Do you have a PLA brand to recommend that has produced good results for you?

Thanks again,
Slim

[Hugues]

Hi !

Got it !

Your speed perimeter/ infill/ sparce are too low. Setup 30 in all of them.

Otherwise, you can try the last version of ks and cubeitmod. Links are in previuos thread.

[Hugues]

I have some nice result with white reprapper and colorfabb. For PLA the best i have is the 3dsytem brand, really expensive but amazing...

[slimbolino]

Thanks, Hugues.

I'll try those settings and let you know how I get on. I agree that it's time for some different PLA.

Today I discovered the 3DBenchy test piece, so I'm going to try that as my benchmark for comparing settings.
http://www.thingiverse.com/thing:763622

Best regards,
Slim

[slimbolino]

Hi Hugues,

Printing the 3DBenchy test piece has raised another issue that I hope you can help me with. The chimney on the top of the model means that a thin pipe must be produced in the last few minutes of the print. I find that these final few layers of PLA all remain molten while it is being built, so the chimney is very messy. This looks to be because each layer only takes 1 or 2 seconds to lay, then the next layer begins and the PLA has almost no time to solidify before the hot end runs over it again and again.

I'm running at 180C and at 16mm/s (because the Cubify slicer ran my Cubex at this speed).

I tried setting Min Layer [s] = 10 on the Fan/Cool section in the hope that the hot end would retract for ~9 seconds between layers and let the PLA cool before applying the next layer. It seems that this is not the result of this setting. Instead, I find that the hot end simply slows down so that it takes the full 10s to lay each layer of the narrow chimney. This means that it still has no chance to cool at any time.

DSCN2075.JPG (92.19 KiB) Viewed 4448 times

Is there a way to build a tall, thin pipe and let each layer cool properly as it progresses, please?

Your wisdom will be greatly appreciated

Thanks,
Slim

[jonny.m]

Hi Slim

Use the Prime Pillar you can find under the Support Tab. This basically adds a second object (Cylinder) to be printed. While the prime pillar is printed the "real" object has some time to cool down.

With the newer Kisslicer Versions you get more Prime structures to choose from.

Regards,
Tobi

[slimbolino]

Thanks Tobi,

I tried that last night. It is improved. I set each layer to 15 seconds but will try slowing it more because some melting was still apparent.

BTW, the beta version crashed when saving the sliced model (with pillar and coarse supports). Pleased to say the last stable version did it ok.

Many thanks,
Simon

[Hugues]

Hi Slim,

Don't use a slow speed neither than a min layer time with your cubex. Both of them will give you some hight overextruded print.
But it's really interesting that the cubex slicer setup a speed of 16mm/s for the chimney part because at this speed your rpm should be near or under 0.1 and the precision is really low. Avoid speed where rpm result are under 0.2 to have a good print.

Usualy when printing small model i prefer multiplying them on the bed. I printed one of this ship one time without issue on chimney.
My printer is setup between 30 and 40 mm/s in all speed. And with them you can print some 3mm cylinder without overextruded part.

Speed is a real problem with our cubex as you cannot go to fast and cannot go slowly...