26 Reply by CornGolem

  • CornGolem
  • Member
  • Offline
  • Registered: 2013-07-22
  • Posts: 18

Re: Temperature for extruding PLA filament?

I agree that humidity has a role since something changed during the night.
But still, when the extruded PLA filament is short enough (not enough weight pulling) it tangles right after extrusion, everytime and always in the same direction. Is that due to the molecular structure alone ??

27 Reply by CornGolem

  • CornGolem
  • Member
  • Offline
  • Registered: 2013-07-22
  • Posts: 18

Re: Temperature for extruding PLA filament?

Here's what I did today:

I suspected that because the nozzle's back is flat, previous polymers (ABS) never get completely flushed out (I could see lines and tiny bits of white ABS in the clear PLA) so I removed the nozzle and drilled its back in a funnel shape. I put it back on and set the temperature to 180°C so that any remaining ABS that didn't melt at 160°C would now melt and be evacuated.
I also carved out wood from under the fan so that more air would come to cool PLA.
I turned the motor on and a little while after extrusion started I saw some weird tangling patterns that could indicate that indeed tangling is due to molecular structure alone.
I lowered temperature to 150°C and this time for some reason it extruded fine (straight filament and motor didn't slow down too much) so I continued with this temperature.
Result:
extrusion speed: 80cm/min
filament diameter: 1,325 ±0,011mm
(I didn't pre-dry it)

28 Reply by torhav

  • torhav
  • Newbie
  • Offline
  • Registered: 2013-08-16
  • Posts: 1

Re: Temperature for extruding PLA filament?

CornGolem wrote:

I agree that humidity has a role since something changed during the night.
But still, when the extruded PLA filament is short enough (not enough weight pulling) it tangles right after extrusion, everytime and always in the same direction. Is that due to the molecular structure alone ??

I have read several papers/sites stating that the long polymer chains in thermoplastics "remembers" the cirkular motion from the feed screw. It is therefore recommended to use a breaker plate.

Google pitfallsinmoulding+extrusion and the second hit is an interesting read.

Will try to trace down the other papers soon.

I just finished my extruder today, and I only have PLA pellets avialible at the moment.
The extruder is based on both filastruder and the lymans extruder.
It has both a breaker plate and a cone shaped nozzle. It is a bit over engineered, but it might be rewarded...
Hopefully I will get good results during the next few days.

Do anyone know if watercooling at the end of nozzle will do harm to the filament? I have the equipment to implement this, but I am not sure if the filament will absorb moisture. We do have a climate chamber at work, so baking/drying of the filament is not a problem.