Trick Cura to change print path

[DidierKlein 729]

Hi all,

I'm not sure if anything new here or anything that the Guru's don't know but as i wasn't aware of this myself i think it can be usefull to share.

Long story short, i'm doing the FairPhone Case test print for 3DHubs at the moment.

It's a phone case that needs to be printed vertically. With the instructions there is a profile for Ultimaker with something odd in it. Nozzle size: 0.6mm.

At first i thought that this was probably a mistake or only to be used with modified nozzles. So i tried to print with my profiles, the result wasn't very good (a lot of stringing mainly).

So i analysed a bit more the 0.6mm nozzle profile and did a research on the google group for fairphone, this is what i came accross:

 

Brief answer... The nozzle size is only for calculating the print path. The nozzle 'shoulder' [the flat part] is more important. That defines the maximum line thickness.

A smaller nozzle causes more pressure though, so it is possible that you have to print slower to prevent skipping.

If you want to widen the shoulder, place some fine sandpaper on the bed and wipe gently the head 3-4 times.

A bigger problem is the cooling. Since you place more material, you need to cool more. An external fan works, but on my machines i have two radial fan attached.

Please feel free to ask more questions...!!

Cheers \ Joris

 

So i checked and compared the layer views:

Shell thickness is 0.8mm and layer height 0.15mm

With a 0.4mm nozzle:

 

You can see that the head does two passes for the shell

 

With a 0.6mm nozzle:

 

 

There you see that the head does only one pass like a Spiralize move.

 

So i printed it and it went very well.

 

Speed was 30mm/s

 

So the UM2 can do 0.8mm shell in one pass in 0.15mm layers.

 

Is this a known trick? I like the result very much and it prints faster too.

 

Is this dangerous material-wise? I guess it applies a lot more pressure in the nozzle but i didn't have any underextrusion

 

[cor3ys 28]

Hi Didier

Yes i have been using this little trick as i have done my fair share of fairphone cases now, i have also used it on other prints also since discovering it.. must admit i use this little trick using simply3d and not cura on fairphone cases so i can control where the z scare goes and also so i can print the bottom of the case really fast then set up a second process to slow it right down at then end to do the tricky bit...

 

[solid-print-3d 30]

+1

 

[ultiarjan 1,223]

Just tried how far I could take this

Took a solid test file, print at 0 infill, 1 wall, 0.2 layer.

Have a 0.6 nozzle mounted atm. First tried tricking cura into 1.2 mm nozzle & wall (note: if my math is correct 1.2 is 400% more volume than 0.6 ...)

started at 30mm/s, turned up speed to 125% and 150% (>10mm3/s), extrusion is no problem at all, printed at 230c, which is to hot. The actual wall printed is around 1.2 mm, I call it a succes.

Then tried 0.6 nozzle, tricked cura into 1.6 nozzle/wall, 25 mm/s speed. (8mm3/s)

Started at 230 celcius, moved down to 215 c, extrusion was never a problem, lower temp shows better quality.

Actual wall thickness printed was around 1.5 mm (so a bit less than the set 1.6)

 

 

***

not related to this test, but cura created a small bulge at the point of the zseam, does this also at 0.6 nozzle setting, so unrelated to this test. Anybody an idea why ??

 

[pm_dude 27]

Interesting. The inner bulge is weird. You might have an open edge maybe?

Note that your math is wrong. 1.2 / 0.6 = 200%

 

[ultiarjan 1,223]

Ha ha.... include PI and try again ....

[jameshs 42]

I think that the bulge is because you have a higher pressure in the nozzle - that small z lift allows a bit of a bleed. In s3d you can specify a random z - more like a spiralize, and you get the same benefit with no blob.

James

 

[ultiarjan 1,223]

sounds strange to me, don't think its normal for z lift to move the nozzle inwards by 4 mm or so ... I think its a cura issue ??

 

[pm_dude 27]

Can you share the model? I'm curious to see what this is about. Random z changes the starting point of the next layer to prevent the blomb caused by consecutive z changes at the same xy position. Its not related to the inner line the toolpath is performing. The mesh has something that confuse cura

[ultiarjan 1,223]

mailed you the file, it's just the simpelest basic shape .... solid from DSM, printed with no top/bottom, 0 infill.

 

[pm_dude 27]

Its a bug with Cura. If the settings have no infill it will move inward for no reason. If you use Only Follow Mesh Surface you wont have that issue.

 

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[pm_dude 27]

Funny fact. I just got poked on 3DHubs to print 2 FairPhone cases.

 

[Dim3nsioneer 558]

Today, I tried the 0.6mm profile for a fairphone case. I stopped the print after the first cutout. The lines were sagging so much that half the lower cutout was closed by a curtain. So I stay with my own Cura settings...

 

[ultiarjan 1,223]

Just did a big vase, 0.6 nozzle (drilled out UM2) cura set to 1.4 nozzle & wall. Spiralise.

Real nice and fast result. Like the 1.4 mm walls in one go very much ! (actual size turned out to be around 1.3)

Started a litlle to hot, but at 205c quality is real nice.

 

[pm_dude 27]

nice!!

 

[pm_dude 27]

So I tried this little trick on the blue FairPhone case. I wasn't really happy with the result so I did another one with my normal settings:

 

0.1mm layers

real nozzle size: 0.4mm

 

Left Nozzle set to 0.4mm, Right Nozzle set to 0.6mm

 

 

So I stick to 0.4mm. I do have to say that there are a few strings to remove but nothing I'm not used to handle...

 

[Titus 170]

Joris told me about his idea to call the flat part Shoulder, and how it could be used. I believe it is a very useful description and that people should get to know about it! I wonder what the standard shoulders are for UMO and UM2 nozzles

Is the vase waterproof

 

[pm_dude 27]

I dont get it. What flat part are you refering to?

[ultiarjan 1,223]

The bottom is not waterproof, the walls are, 1.4mm on a 0.6 nozzle is pushing it to much for this... lines are not 100% matching, but the sides are very good. The bottom leaking is easy solved with a little PVC glue on the inside.

Maybe I'll try sanding my 0.6 nozzle a little to make the "shoulder" a bit wider.. I would also like to experiment more with even bigger nozzle sizes.... but the UM2 is just not very practical for swapping nozzles ....

 

[ultiarjan 1,223]

I dont get it. What flat part are you refering to?

 

he's talking about the flat part on the extrusion side of the nozzle, the area around the extrusion hole touching the model being made.

 

[ultiarjan 1,223]

I found a way to also print the bottom waterproof ....

just lower the wallthickness and increase the material flow.

so when printing with a 0.6 nozzle, and walls of 1.4 mm, just set the wall to 1mm and overextrude using material flow.

this test turned out very nice.

https://www.youmagine.com/designs/vase-the-wall

 

nozzle size & wall thickness 1mm, flow 140%

Used UM PLA, speed 30, layer 0.2, temp 215, fan 40%, bed 60 celcius.

 

[pm_dude 27]

Looks pretty good

[ultiarjan 1,223]

Tried the same trick with colorfabb XT, at 250 celcius... disaster, the 140% flow was to much.... caused a big leak at the top of the heaterblock... took at least and hour to clean (burner) and rebuild. Think with XT a much higher temp is needed to get a waterproof bottom using a high flowrate.

Tried later with homebrand (10 euro less vs UM/Colorfabb) PLA from "makerpoint.nl", worked perfect again. nice waterproof. This cheaper material is from a dutch producer and a bit softer than regular PLA, just like the colorfabb stuff.

 

[solid-print-3d 30]

@ Arian, does that printed cooling fan housing work better than the stock steel?

 

[ultiarjan 1,223]

Yes. I think it does. Did a before and after ultibot... with this fan setup the right ear was clearly better... this thing is more symmetrical.

And its more silent. Had some vibration noise on the metal one.. could not realy get some screws fixed properly... but ill save it ofcourse incase we someday get a dual nozzle setup