UM2+ material extruding before print question

[LePaul 312]

First, same gcode...no changes made between prints.

Print one, once Ultimaker 2+ reaches temperature, material extrudes prior to print. A good amount of filament comes out and the print starts. That's great.

Print two....Ultimaker 2+ reaches temperature, starts extruding sound...thin filament curls around the print head...and for a brief second, some material finally starts coming out. However, I have had many times where I wind up with a messy glob on the print head and it just plows over the skirt/brim my first layer is trying to make. I usually have to abort the print. SOMETIMES the flow normalizes in time for the blob to be picked away while the skirt is being laid down, saving the print.

But it's really mystifying why the priming works one time, but not the following time.

[reibuehl 40]

I see the same behavior with my UM2 since a while.

[neotko 1,417]

You could yank the lever while temp reaching and push filament so the first extrusion is ready.

Print one of this to have at hand.

https://www.youmagine.com/designs/the-wedge

[neotko 1,417]

Or this if you want to fix the feeder lever

https://www.youmagine.com/designs/um2-lazy-lever

[LePaul 312]

Is there something at the end of the print that makes this a problem for the next?

I really don't want to print parts to make the machine more reliable.

I'd really just like to troubleshoot the behavior first (but I appreciate your input)

[neotko 1,417]

Well the amount that the ultiflavor extrudes is fixed. It can be too little or too much but that depends on how much filament was left. Also the end sequence of the... I see the problem now...

This is the problem...

End sequence retracts too much, and that amount is 'almost' pushed back before printing. That means that, since you can't edit ultiflavor start/end (without using reprap or tinkergnome or making your firmware). Everytime the print finishe the filament will retract X amount. And when print starts Y amount is primed. Clearly to that we have Z dripping of filament lost. So when you prime Y - Z it isn't enough to reach X.

Just push some filament or do what others do, use a brim (I never do that). I do my own start/end sequences for my umo with um2+ hotend.

Edited November 4, 2016 by Guest

[reibuehl 40]

Does that mean that there might be a fix in an upcoming new firmware version?

[neotko 1,417]

Does that mean that there might be a fix in an upcoming new firmware version?

 

Don't think (don't know) also user could complain that it purges too much, since the printer can't remember how much was retracted on the last print. Or how much it dripped after the print. Ofc you could edit the firmware to increase the purge amount. Or just forget about ultiflavor and use reprap like on umo, that's also better (IMO). Who knows, is a matter of customizing the printer for your needs. No two users print the same way.

Edited November 4, 2016 by Guest

[neotko 1,417]

If I would had a um2/um2+ I would use this solution to have a start/end gcodes controlled by me, not the machine.

@ahoeben Posted this for other problem. But if you see the json he wrote, you can edit how much E extrudes to purge and how much E- retracts at the gcode end.

https://ultimaker.com/en/community/24598-no-print-to-3d-printer-button-not-available?page=last#reply-161912

[reibuehl 40]

I would rather compile my own version of Tinkergnomes firmware... do you have any recommendations on which settings for purge and retraction after would make sense as a start?

[gr5 2,002]

If you have a UM2+ definitely print that tool. I use it when I change filament. To do cold pulls (rare). And if I want to put the filament away for the night.

Often when done with a filament if you use the "procedure" or if you just yank it out there is often a string and often a blob at the end of the string. If you don't use the "wedge" tool that string and also blob end up inside the feeder or inside the bowden. It can be a serious problem - just that string can make it too tight for the next piece of filament. Plus you get the wrong color coming out 10 minutes into the print if you change colors because the thread is the wrong color.

[tinkergnome 924]

I would rather compile my own version of Tinkergnomes firmware... do you have any recommendations on which settings for purge and retraction after would make sense as a start?

 

It is related to the settings at the end of Configuration.h:

I read somewhere that 20mm for END_OF_PRINT_RETRACTION is perhaps a bit too much (material can get jammed in the PTFE coupler). I use 12mm most of the time.

The extra priming at start is 50 cubic mm (approx. 8mm for filament with a diameter of 2.85mm) . If this is not sufficient, you can try to increase this a bit.

And keep in mind, that this stuff depends on the material diameter of the current selected material on the machine.

In addition: at the moment i think, that a value of 5 for PRIMING_MM3_PER_SEC is a bit too high, but I have not (yet) made any further experiments.

[reibuehl 40]

I have compiled a version now with 100mm^3 and all other values standard.

[Yoter 14]

My solution is low-tech, but I always move filament through the maintenance menu before starting a print. That way I have the extruder primed and ready to go, and if I am going to have any problems, I am not trying to race the start procedure to shove a rag in to wipe a filament blob before it starts printing.

[LePaul 312]

Unless we seem this corrected in future firmware , that seem to be a good workaround