PLA extruding problem

Hello,

I'm using Adrian's geared extruder and PLA. From the videos I've seen melted PLA appears to be very fluid.

The problem I have is that in my case the PLA is coming from nozzle very slowly and is already quite hard. I think the gears' speed is ok (perhaps a bit slow but not that slow) and when I heated the barrel even more (I think I even tried 220 C) is was more fluid. And this is the heater I'm using:
[www.iprint3d.org]

Please, does anyone know where the problem could be? 220 C for PLA seems to be a bit too high, perhaps my thermistor is too close to the Nichrome wire. Or, perhaps the wire is too far away from the nozzle? So the melted PLA hardens again, before it comes out of the nozzle? Should I mount the wire and thermistor as low as possible? Maybe should I mount just the thermistor at the very bottom? This is how I built the heater:

  ____
 /    |________|||||
<     |___////_|||||
 \____| ^      |||||

< nozzle
^ thermistor
//// wire
|||| thermal barier

  ____
 /    |________|||||
<     |___////_|||||
 \____|        |||||
   ^

< nozzle
^ thermistor
//// wire
|||| thermal barier

Your thermistor should be on the nozzle (especially if you are using a big head nozzle as your diagram would appear to indicate).

I extrude 4032D Black PLA at 210° C (215° C for the first layer).

---

Bob Morrison
Wörth am Rhein, Germany
"Luke, use the source!"
BLOG - PHOTOS - Thingiverse

A quick fix would be to insulate the heater barrel and most of the nozzle (just leave the tip clear) with some fibreglass insulation - that should keep the tip from cooling too much. If you put 5 mm or so of insulation on, you can wrap it with some electrical tape.

It wouldn't hurt to calibrate your thermistor either - those things are notorious for being the wrong value or having the wrong table loaded in the firmware.

Wade

Thanks all for the suggestion!

I rebuilt the heater - I moved the thermistor all the way down (close to the nozzle), and I put the wire also a bit lower (away from the barrier).

However, it exhibited similar behavior as before and when I tried to speed up the extruder stepper it teared off the barrier from the reprapped part, i.e. the glue bond broke.

Right now I'm waiting for the glue to harden (24 hours).

Wade, by "calibrating the thermistor" you mean to measure the actual temperature of the nozzle by proper thermometer, right?

Correct; try to measure the temperature with a known temperature. The best way is to insert a thermocouple down the barrel and measure the temperature there.

It seems that the PLA I was using was a bit weird. Now I'm using another type and it flows quite nicely and is very sticky.

I have another problem but as it is not related specifically to PLA, I'll start another thread.

Thanks a lot!

Do you have details on the non-working PLA and the new one that you got to work ?

I have relatively similar issue so I'd appreciate if you can give more details

thanks