UM2+ Pause and change material issue

[monkeycmonkeydo 0]

Good afternoon, I've been using a UM2 (upgraded to 2+) with Cura for a few years now and have a problem whenever I pause a print to change the material, either to a new colour or to replenish material that's almost out. Basically after changing the material as normal and allowing the material to come through to the nozzle fine when I click resume the extrusion starts immediately, with maybe 50mm of material being extruded before the print head makes it to the model and continues the actual print. This then creates a messy patch at the resume point and has a couple of times resulted in a failed print as the nozzle has caught on this erroneous 'lump' and pulled the print off the bed. This isn;t my video but it's the exact issue I have: Pause/resume video

 

Any help or advice would be much appreciated. I'm just off to see if there's a firmware update for my machine that I haven't applied yet but in teh meantime let me know if I'm missing something in settings etc.

 

Edit: Just updated the firmware and it still does exactly the same.

 

 

Edited November 1, 2018 by monkeycmonkeydo

[tinkergnome 927]

4 hours ago, monkeycmonkeydo said:

Basically after changing the material as normal and allowing the material to come through to the nozzle fine

 

What does this exactly mean?

How do you initiate the pause (manually on the printer?)

How do you change the material (with the menu function on the printer or...)?

[monkeycmonkeydo 0]

Just now, tinkergnome said:

 

What does this exactly mean?

How do you initiate the pause (manually on the printer?)

How do you change the material (with the menu function on the printer or...)?

It's a UM2+ and just using Cura software so I hit 'pause' on the machine, select 'change material', change as normal letting the material flow smoothly through the nozzle for a few seconds before finishing the material change process and then hit 'resume print'.

[monkeycmonkeydo 0]

No one? I take it it's not just my machine and this is a standard 'issue' with all UM2s?

[Smithy 1,144]

I don't know, so just an idea, but could it be that the printer retract when you click on pause? 

Then you change the material and due that you have the filament ready at the nozzle, click on resume, the printer thinks he did a retract before and must now bring the filament back to the nozzle and thats what you get.

[monkeycmonkeydo 0]

Seems a bit of a schoolboy error if so! I guess if the firmware doesn't do anything differently between a pause and resume and a pause, material change and resume it could be the case... Surprised the issue hasn't been picked up before and fixed in a firmware update. I've emailed the query to UM direct so if I get anything useful back from them I'll post up here.