UMO not putting out enough material at start of print

[LePaul 321]

As the subject says, it seems like I have to crank on the extruder wheel to get some additional flow at the beginning of a print.

I usually start (PLA) at a temp of 215-220, while i get a good amount of flow coming out of the nozzle. But when the very start of the print, when the print head moves from the autohome, that's where it lacks the material flowing out. By the first pass, material is coming out at a normal rate and all is well.

Its usually a bigger hassle on brings I do not wish to use brim or raft.

I really don't want to mess with GCODE and wondered if there is a setting in Cura (latest, non-Beta) to extrude a bit extra at start?

[neotko 1,417]

You need to change the gcode start gcode to make the e+X higher. On the wipeout curas I don't know how to change it (I don't use it) on old stable cura it was just as easy as editing the start gcode (and it it's commented so you know what line to edit).

[neotko 1,417]

Now that I think about it. I think new cura has a 'minimum' extrude for skirm/brim. Changing it should do the trick.

[LePaul 321]

I've looked around the current release and don't see how to do that for the skirt....at least not thru the GUI.

But looking at the Start/End-GCode I see this...

G1 F200 E3 ;extrude 3mm of feed stock

Would it be advisable to change E3 to E5 and see if that helps? Or greater?

[Dim3nsioneer 557]

Priming the hotend is certainly not a bad idea. The UM2 primes with 20mm iirc. I use something like 80mm3 on my UMO.

About the hardware: Do you have the same effect if you preheat the nozzle and wait e.g. 30s until you start the print?

[neotko 1,417]

I purge 7 but I use smaller filament 1.75 so that might be quite a lot on 2.85. Try 5-6 and see how it goes.

[LePaul 321]

Priming the hotend is certainly not a bad idea. The UM2 primes with 20mm iirc. I use something like 80mm3 on my UMO.

About the hardware: Do you have the same effect if you preheat the nozzle and wait e.g. 30s until you start the print?

 

I pre heat to 225 and then start the print. What messes things up is when the print begins, the bed autohomes, squishing the filament to the print head...and it seems to take a few seconds for the flow to resume.

[neotko 1,417]

Ups correction. I do push 15mm

G1 Z15.0 F500 ;move the platform down 15mm

G92 E0 ;zero the extruded length

G1 F200 E15 ;extrude 15mm of feed stock

G92 E0 ;zero the extruded length again

[LePaul 321]

Ups correction. I do push 15mm

G1 Z15.0 F500 ;move the platform down 15mm

G92 E0                  ;zero the extruded length

G1 F200 E15              ;extrude 15mm of feed stock

G92 E0                  ;zero the extruded length again

 

That's interesting. And you have the Original + (heated bed)

[LePaul 321]

Well 15mm was way more than I needed....but it shot out a nice pile of melted filament and the first layer went on perfect! I'll have to tinker on how much is just right...I may take it back to 10 mm and see how that is....either way, its a step in the right direction! Don't fear the GCode!

[DidierKlein 729]

you can print a skirt of 5 passes to be sure that the filament is well primed after de bed auto home maybe? I always add at least a small skirt to be sure it's flowing nicely before printing the first layer

[neotko 1,417]

Indeed 15 on 2.85 might be way too much. I really recommend you make at least 1 skirt. Because I don't know why without it the first time it starts to print the object the first touch with the bed always wasn't really well stick to it. So after the puege I do at least 1 skirm.

[LePaul 321]

you can print a skirt of 5 passes to be sure that the filament is well primed after de bed auto home maybe? I always add at least a small skirt to be sure it's flowing nicely before printing the first layer

 

Not a bad idea, where do I add more passes for the skirt again?

Just having the extruder prime more material made a huge difference. I just need to scale it back a little. The default setting wasn't enough

[DidierKlein 729]

In legacy Cura you can find that in the expert panel.

To activate the skirt you have to select none in the platform adhesion dropdown