Once heated up, my Prusa Mendel oozes filament before I start a print - is this normal? If not what can needs to be done to stop it?

I tried the pyramid print and got a result similar to the initial picture in this thread

Similar result

I too am getting the thin strands of PLA between the corner 'struts' of the pyramid.

I assumng likely the oozing & the stranding are linked.



What can be done to correct the stranding problem?

Thanks in advance

Mike


Using PLA. Brass nozzle 0.5mm for 3mm filament.

When left heated and idle the hotend will drool out the molten filament in the nozzle, there is no way to prevent this. You counter it by priming the nozzle before you start the print, and/or by printing a skirt.

Stranding is fixed by dialling in retraction and temperature perfectly.

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-Nudel
Blog with RepRap Comic

Ok thanks Nudel.

Looks like the pronterface is already printing a skirt.

Pronterface has the reverse (= retract?) default as 1mm/min. I upped it to 2 & the quality got a lot worse(insufficient filament)
very 'whispy' print. Presumably 0 = no retract, not a good idea.

I'll have a go with the temperature settings.

Mike

As you found out, pulling back too far is bad. It's better to increase the speed of retraction than increasing the distance retracted. I think I saw nophead say elsewhere that 1.8mm is about the most you would want for a bowden cable, so I suggest you consider that an absolute upper bound. The plastic parts for my first working Mendel came from him, and I consider the quality of his prints to be the bar I try to meet. I usually have the retraction distance between 0.8 and 1.0 depending on the spool of filament I'm using...

I think from memory using SF41 and Repsnaper I use 30mm/sec and 2mm of retract, can't remember exactly and not at home to check the settings on my desktop

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Experimenting in 3D in New Zealand