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Strick9

UM3 + Cura 2.4 Nozzle moves away then back into initial prime extrude

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We are having an issue of the nozzle moving back into the prime piles and picking them up and dragging them around. This has been happening with both nozzles sometimes on the PVA even when printing a single material part without PVA. I have had some luck modifying the GCode to move away from the prime pile then come back down close to the build plate to let any extra get attached to the build plate before moving on. However, if i miss any part of the gcode mod it picks up the prime pile or rolls it around while printing causing other issues or making it so we have to watch the print for the first 10-15 mins.

It happened even more often before i moved the nozzle 1 and nozzle two prime piles to opposite sides of the build plate. Every now and then it would prime nozzle 1 just fine then when it went to prime nozzle 2 it would pick up the nozzle 1 prime.

The link below shows the nozzle moving back and picking up the prime pile.

 

It would be nice if Cura resolved this or maybe another UM3 firmware update? It is frustrating to have to edit the Gcode for every print, esp since it is different depending on whether we use a brim or not.

-Danny

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Happens every time I print support with PVA. I've never printed any other material in core 2. I've simply resigned myself sitting by the machine waiting for the material change to core 2, watching the prime process and at the proper time, I grab the prime pile with a pair of really long tweezers and hold it in place.

Not very high tech, nor elegant, but beats the hell out of ruining a print in the first 3 minutes and having to start over.

This has been going on since firmware 3.5 and Curs 2.3. I keep hoping it will be remedied with each release. Alas, no joy . . .:(

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It was definitely worked on, I just loaded 2.5 beta today. Now it comes down and squashes the prime prime pile with the carriage.

Here is the unmodified GCODE around the prime extrude for nozzle 1 which in the case of this print was after the prime pile and brim was printed in PVA from Nozzle 2:

(Please note I moved the Nozzle 1 prime location so that I could see it better on the camera)

T0

G92 E0

M109 S245

M104 T1 S0

G0 F5000 X213 Y207 Z0.27

G0 X162 Y6

G0 F15000 X162 Y6 Z2

G280

G1 F1500 E-6.5

G0 F5000 X162 Y16 Z0.27

It is the last line shown above that moves the carriage in the Y direction 10mm from the prime pile and sits the carriage back down in it. if it just would have gone to X112 before sitting back down to Z0.27 it would have been fine, It'd be even better if they put a 2 second dwell in there for the nozzle have time to ooze onto the build plate.

So the Gcode would then be:

T0

G92 E0

M109 S245

M104 T1 S0

G0 F5000 X213 Y207 Z0.27

G0 X162 Y6

G0 F15000 X162 Y6 Z2

G280

G1 F1500 E-6.5

G0 F5000 X112 Y6

G0 Z0.27

G4 P2000

I CAN edit the GCODE but it would be awesome if there was no edit required to trust printing without having to run to the machine if a prime pile gets picked up.

Also adding a short dwell after the nozzle 2 prime would be awesome too. I even added a move to z30 then a -50mm Y move then move to z2.27 with a 2 second dwell, this worked awesome to get the ooze of PVA to attach to the build plate.

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Hello,

Something that may be interesting to notice : I'm currently testing some dual color PLA prints, and I don't have the issue at all with PLA. It seems to occur only with PVA. Since flow control is not exactly the same for PVA and material "glues" more to the print head, that may deserve a special treatement in the slicing / printer init ?

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G0 F5000 X162 Y16 Z0.27

That's 1cm from the starting position of the prime! That should never catch the prime poop.

I can't imagine that that gcode catches the prime poop.

 

You don't have to imagine it catching the prime poop, watch the video above :)

The problem is it goes from Z2 to Z0.27 before before it goes from Y6 to Y8 or so.

Cura 2.5 helped but it still sits down and catches the prime pile with the fan shroud sometimes. It mainly does this on the nozzle 1 prime pile.

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I had the same issue.  Updated the firmware about a month ago which has solved the problem for me.

 

we updated our firmware about 2 weeks ago things were better but still have to at least watch both nozzles go through prime sequences. It happens a lot less with new firmware and cura 2.5 beta but when it does happen it ruins the print.

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