Material pushed during cool head lift

[mevander 0]

Hi!

We've recently installed an Ultimaker 2 at work and I'm currently working on getting it set up and learn how it works. I was testing the "cool head lift" feature and also the "pause at height" plugin the other day and noticed that the nozzle keeps feeding material through the nozzle during both the cooling pause and when waiting for user input during the height pause. This created a large blob of material that was moved back into the model with not so very pretty end results.

Is this supposed to happen, is there a setting that might help me here or what might be going on? If I look at the layers in Cura, it looks as if it is supposed to perform a retraction during the cool head lift but it didn't seem to happen?

I must also thank you all for providing so much useful information in the forum. I've learned a ton by just browsing subjects and a don't believe our setup would have run very smoothly without all the collective know-how available here!

Cheers

/Mikael

 

[IRobertI 521]

The retraction will relieve the pressure in the print head but will not empty the chamber completely. Since the print head is still up to a temperature where the plastic can flow, gravity will eventually cause the material to drip out. Personally I just use a bit of tissue paper to quickly wipe the nozzle clean before resuming the print.

Retractions work well to prevent drippage during an actual print because there's just not enough time for the plastic to drip out during the rapid travel moves.

 

[gr5 2,270]

What robert said. Except that I believe it is caused not due to gravity but thermal expansion of the filament. It happens if the printer is upside down also.

Cool head lift is a huge improvement over not using it but even better is to print a tower or two objects side by side. But only if you want showcase quality.

 

[mevander 0]

Thanks. I was suspecting it was something like that but was surprised by the amount of material that was pushed. We tried this feature on the robot and ended up with a rasta robot. Funky but not what we had expected