UM2 start procedure??? (Dip in the puddle)

[restinpieces 3]

Some time ago the start procedure on my UM2 changed. Unfortunately I don't know which update it was.

Now the printhead moves to the front left side and extrudes a hole blob of material into the air (printbed is 2cm beneath). Then the nozzle dips into the blob and after that, the whole mess moves to the actual print.

I learned that start.gcode is not used by the UM2 but where is this behavior coded then? I would really like to change it.

 

[zaski 0]

It is in the gcode. It happens only with Cura.

[donmilne 2]

"then the nozzle dips into the blob". Hmm. I'm not sure that's what I see: I see a x-y move to the approx center of the bed while the bed is being raised. I believe the idea is to lay the priming material in a run along the glass where it hopefully starts the brim.

In practice the xy-move leaves a wisp of material hanging loose. I've had occasions when the print head catches this and peels part of the print off the table. So, I prefer to be there when the filament is priming, allowing it to fall between the points of a pair of tweezers. When the xy-move starts I pinch off the primed material and dispose of it. Seems to work ok.

 

[swordriff 119]

I had this too!! after priming in the SW corner ca 2cm above the glass, it first dips into the blob and tries to carry it

to print start. I swore at it and needed to have a print ready and it was a mess and I chased it with tools and tried to

remove it "in situ".. NO luck.

I fixed it by renewing the FW, I updated the FW again, I also installed Cura.

I also re sliced the part.

I cannot say what fixed it.

Daid: If the bed could stay lower when priming, ie 5cm or more, then it would work better ( not for THIS particular snag), but it would work better always! The gravity would help a lot.

Thank you.

 

[IRobertI 520]

It is in the gcode. It happens only with Cura.

 

Unless you've changed the Gcode flavour to RepRap in the machine settings, it is not in the Gcode. This behaviour is set in the firmware for the UM2. That said, I can't remember seeing that behaviour before (where the nozzle goes straight down into the priming blob). I would try re-flashing the firmware and see if that helps.

 

[restinpieces 3]

Thank. I should have the newest firmware. I can't think of any use to reflash??

Does anyone know where this procedure is located? So that I may see whats going on?

I try to make a short video next time i start a print.

 

[gr5 2,167]

Someone else complained of this recently. I've never seen the behavior.

You can look through Marlin (the firmware) if you want - it's pretty easy to read and shouldn't be hard to find this code but if you make your own custom firmware and new features come out... or you can do a pull request. Let us know if you figure out if this is a Marlin thing and which version has the bug.

If, in Cura, you choose "rep rap" flavor then it's controlled in Cura and in the gcode. You can customze the "start.gcode" setting in cura (only visible in "rep rap" mode - change this in machine settings) and set any damn start procedure you want. But I really prefer utligcode mode.

Marlin source for ultimaker 2 is here on github:

https://github.com/Ultimaker/Ultimaker2Marlin

 

[restinpieces 3]

Thats the problem. I don't find that code easy to read that why I asked where this code is located so that I may change it.

 

[swordriff 119]

I reset the Um2. Then installed Cura a new. Then flashed the firmware from inside Cura.

It worked for me

 

[aviphysics 9]

Hmmm. I remember that my UMO used to do that, but at some point there was a change in the order of the start code and now it lifts and primes after homing. It then goes directly to the start of the print. I can't remember why I had problems fixing that behavior at the time. Seems like it should all be in the startup gcode.

[Dim3nsioneer 557]

Those who suffer from the dip bug and use the RetractWhileCombing plugin: please make sure you have the newest version because it was a dip bug there...

 

[restinpieces 3]

Thanks thats one confirmation that reflashing changes the startcode. I reset my UM2 recently because I tryied out my custom firmaware. I still dont understand how reflashing changes the startup behavior if nothing else is changed.

 

[aviphysics 9]

Retract while combing plugin would affect the gcode, not the firmware.

It really doesn't make sense for it to be a firmware issue. I guess you could try seeing how your firmware handles g0 and g1 moves that travel in all 3 axis. If it goes up or down before traveling along the xy axis that might explain it.

[restinpieces 3]

Well.... this is the strangest thing ever. It seems to depend on the thing that is printed. The print I started a minute ago produced the blob but then moved to the start of the print instead of dipping first.

As soon as the print is finished I try again and see if this is consistent. This might be a bug in the end.

 

[donmilne 2]

Both prints sliced with the same version of Cura?

 

[restinpieces 3]

Same version, same preferences, nothing changed expect the model. And I confirmed it second start with this model it did not dip. I have the suspicion that the behavior depends on the distance to the starting point, maybe?

 

[donmilne 2]

I suppose if you have a skirt or brim that extends right to the corner then that might be a problem.

 

[gr5 2,167]

@aviphysics: The UM2 is strange in this way - normally we use cura in "ultigcode" mode which doesn't specify the start sequence anymore - so the homing, priming, warming up is all done in firmware now. Unless you export to a gcode file in "reprap" mode. In that case it is all done using gcodes. Supposedly the advantage is you can slice once for an ABS and PLA part and separate the slicing process from the material used. So on the UM2 you select the material which sets approximately 5 settings (bed temp, nozzle temp, retraction distance, retraction speed, fan speed multiplier (if at 50% then all fan commands do 50% of what gcode asks for)). I don't really think that's much of an advantage as I never print the same part in 2 different materials.