PLA, Fills yesterday, but not today....

Noob, trying hard.

Prusa Mendel using Sfact, Pronterface and Sprinter.

Two days ago, I was printing Stars and/or 20mm cubes to dial in the Extrusion width on my .34 nozzle.

All the prints were working fine, except seemed slightly over stuffed at .25 height and .40 extrusion width.

Today, I was going to try .42 and/or .38 width, but I can't get the unit to fill past the second layer. The PLA just stops coming out of the nozzle consistently.

Even going back to .40 it fails to fill.

I haven't changed the nozzle temp 200 on heater block. And .40 on bed. (Thermister is taped to glass top)

Now I've heard that printing in a cool basement can be problematic, and the only outside change, is we finally got snow here.

As a test, I tried extruding 50mm and other than it sticking to the nozzle at times, seemed to extrude fine. Although slower than the print.

Ideas, suggestions welcome.

Does ABS have simulator problems?

Try printing slower. Maybe extruder can't keep up.

Also check the hobbed bolt for clogged teeth, and extruder motor for loose gear.

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-Nudel
Blog with RepRap Comic

It might be useful to know which hot end design you are using.

You need to determine what the real culprit is.

1. Using too high a temperature, and/or thermal barrier hole too narrow.

PLA in particular expands quite a bit when heated near the melting point. It also becomes very soft long before it melts. If the thermal barrier tube diameter is too narrow, the filament can seize against the walls as it warms up.

To test for this condition, remove the hobbed bolt, and try pushing filament through by hand. If the temperature is OK, you should be able to push through with ease. If you cannot easily push the filament through, try pulling it back out. If it is stuck, then your filament has seized in the termal barrier. If you are brave enough, try drilling the barrier out in diameter increments of 0.5mm. You should not need to exceed 4.0mm diameter.

DO NOT proceed to adjust roller bearing pressure against the hobbed bolt until you can push filament through by hand. You will never solve the problem.

2. Using too low a temparature.

I don't think this is the case. Easy enough to check, right?

3. Bearing against the hobbed bolt too loose.

If you were able to push filament through by hand with ease, and if the hobbing is full of plastic dust, then your roller bearing is not tight enough against the filament. Tighten it beyond the point where the big gear can move, and slowly back off the pressure until the filament begins extruding.

4. Bearing against the hobbed bolt too tight.

If the bearing is too tight, the stepper motor should stall, and lash the big extruder gear backwards at regular intervals when you try to extrude. Slowly back off the pressure until the filament begins extruding.

brnrd Wrote:
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> Try printing slower. Maybe extruder can't keep up.


Wish I knew how! Too many variables in the Speed tab to play with.

Nudel Wrote:
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> Also check the hobbed bolt for clogged teeth, and
> extruder motor for loose gear.


We Have a Winner!!!

I love the reversed hobbed bolt I got with my Plastic parts. Nice open groves with good sized teeth.

However, After removing the plastic, I was surprised how much plastic had actually managed to get lodged in there.

I'm sure that was causing slippage.

Thanks.

Komb'

Answering this one because I like it.

jcabrer Wrote:
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> It might be useful to know which hot end design
> you are using.
>

MixShop design?

It's a PTFE rod with a threaded brass rod. both 3mm holed. Aluminum heater block threaded on then brass acorn nut with .34mm hole.
Hand assembled by myself.

> You need to determine what the real culprit is.
>

This is why I like this post.

> 1. Using too high a temperature, and/or thermal
> barrier hole too narrow.
>
> PLA in particular expands quite a bit when heated
> near the melting point. It also becomes very soft
> long before it melts. If the thermal barrier tube
> diameter is too narrow, the filament can seize
> against the walls as it warms up.
>
> To test for this condition, remove the hobbed
> bolt, and try pushing filament through by hand.
> If the temperature is OK, you should be able to
> push through with ease. If you cannot easily push
> the filament through, try pulling it back out. If
> it is stuck, then your filament has seized in the
> termal barrier. If you are brave enough, try
> drilling the barrier out in diameter increments of
> 0.5mm. You should not need to exceed 4.0mm
> diameter.

Had this sort of problem before. Had the rod too far up the PTFE and managed to get hot plastic stuck to the extruder.

Before I removed the plastic, I disengaged the motor and pushed on the filiment, the bolt/gear turned and plastic came out the print end.

Then I pulled the plastic out, without any trouble.

>
> DO NOT proceed to adjust roller bearing pressure
> against the hobbed bolt until you can push
> filament through by hand. You will never solve
> the problem.
>

Good advice, I'm sure.

> 2. Using too low a temparature.
>
> I don't think this is the case. Easy enough to
> check, right?
>

Right! Been there, done that.

> 3. Bearing against the hobbed bolt too loose.
>
> If you were able to push filament through by hand
> with ease, and if the hobbing is full of plastic
> dust, then your roller bearing is not tight enough
> against the filament. Tighten it beyond the point
> where the big gear can move, and slowly back off
> the pressure until the filament begins extruding.
>

I once thought I would be cleaver, and would leave the roller loose enough to push new plastic past it. (until I can print an accessible extruder...) I've learned that is Not the way to go. Wasn't sure how tight to make it though.

It is set much tighter now. Thanks.

Komb'