How to clear the remainder of filament in the extruder?

My Prusa build has made some progress, with my first plausibly decent print tonight!

Working in PLA to start.

I was left with just a few inches of filament to feed in so to clear it I thought I'd run another small print
until it ran out. I stoppped when no more was being extruded

When i look into the top of my Wades geared extruder I can still see some of the filament.

How do i clear it ?
heat up the hot end & reverse extrude in pronterface?
push in some new filament to poke the old through?

Also do I loosen the wing nuts on the extruder & re-tighten after?

I've gotten in the habit of leaving the filament in the extruder between prints for a few days - presumably
there's no problem doing that?

Thanks in advance,

Mike

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Prusa Mendel /Parcan Mk 2/1280 RAMPS 1.4/PC XP OS/Pronterface/Slic3r

In the UK, down south & over to the left you'll find the West of England RUG.
For details, visit tiny.cc/woereprap or tiny.cc/woerug

I just snip the old off as low as I can get and use the new colour or new reel to push the old stuff through if done properly you don't need to release the Idler tension, never been a problem so far and I have run over 1000m through mine now.

Other thing I have done but not very often is heat up the hot end, release the tension and pull the old filament out while hot

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Experimenting in 3D in New Zealand

If it is totally jammed, you can heat some hot ends up with a torch, and burn the plastic out.

ABS will dissolve in acetone, but it may take a day or two.

Here is what I do under normal conditions.

If I am continuing with the same material, I cut the current filament about an inch from the top of the extruder, and make the filament as straight as I can, by bending it. The cut must also be straight and flat. I use a razor. If I have my soldering iron handy, I make a small dimple into the top of the filament. Now I take the new filament, and sharpen the end into a short cone. This does two things: It helps keep the new filament centered on top of the old, and it helps to align the filament further down in the extruder, should it slip off of the dimple, or if no dimple is made.

If you are going from PLA to ABS, run the extruder at the lower end of the temperature range, even as you begin to extrude ABS. The reason being that if you run at the higher temperature, the PLA will begin to act as a liquid lubricant on the walls, and you will find bits of it coming out several days later. This depends on the hot end design of course, but it works for me.

Best of luck

-Wildseyed-

If the remaining filament is still touching the hobbed bolt, just heat up the extruder and reverse the filament until you can remove it. If not, heat up the hot end, insert some more filament, and engage it in the teeth of the hobbed bolt. Then advance it using pronterface so that it pushes down the old filament into the hot end and out the nozzle.

I put nuts on the screws between the wades block and the idler that stop it closing completely. That makes it easy to feed in a new filament after reversing out the old one.

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[www.hydraraptor.blogspot.com]

Ok thanks to you all.

Looks like you can either reverse it out or poke through the new filament.

I was switching from blue to green PLA. I extruded some more of the blue & found I could poke in the new green PLA.
Contining with extruding after a while the green came out.

Mike

NelsonRap Wrote:
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> I just snip the old off as low as I can get and
> use the new colour or new reel to push the old
> stuff through if done properly you don't need to
> release the Idler tension, never been a problem so
> far and I have run over 1000m through mine now.
>
> Other thing I have done but not very often is heat
> up the hot end, release the tension and pull the
> old filament out while hot


This.

You should be able to trail the old filament as it drives down with the new reel. If the filament is below the hobbed bolt--and it's being finicky (it can sometimes) we've had success using a long thin hex key, inserted from the top. Lightly apply some pressure and the old filament should spew right out. At temperature, of course.

When changing colors or types of filament it sometimes takes a while of flushing the new plastic through the nozzle before it stops looking like a mix of the two, even if I backed out the old filament. A trick I've been using is to pull back my idler and shove a small (2.5mm thick) screw driver down into the hot end while its hot. It pushes out a large amount of the old plastic out without wasting my new plastic. Both PLA and ABS do a poor job of sticking to most metals, so when its done and my screw driver has cooled off I can easily peel any plastic off that came out with it.

When I want to change colours and the hot end has cooled down, I start it heating, and keep trying to tug the old filament out. With pla, the temperature is about 100C when you can pull the entire thing out with a cast of the hot end at the end. This was, you don't leave much spare pigment to mess up the next colour.

I use a standard Wade's Extruder. I find that if you try to empty all the old filament out of the extruder before shutting down (e.g. by pulling the filament out while it is still hot, or by cutting of the filament and extruding until it won't extrude any more) and then let it cool down, there are almost always some "hairs" of old filament left in the extruder body, and / or the filament will soften and then jam just above the top of the heated zone. These tend to cause grief when trying to load new filament, because they cool and solidify in the extruder body, and don't always pull through cleanly when you fire up again and try to load new filament.

My preferred method is to always leave the end of the old filament in the extruder when I shut down. I never seem to have any trouble re-starting from cold with the old filament left in the extruder. For transport, etc, I cut the old spool off, leaving a few cm protruding from the top of the extruder.

To change filament, I heat up to operating temperature (so that it can extrude properly), then pull out the end of the old filament (which inevitably leave some old molten filament in the melt chamber), and IMMEDIATELY insert the new filament before the old filament has a chance to solidify in the extruder body, and extrude 50 mm or so, so that the new filament is fully loaded down to the melt chamber. Extruding another 50 mm or so if necessary will fully purge the old filament so that you are ready to go with the new filament.

This works almost 100% of the time. If I get a jam, I remove the idler and pull out whatever hairs of filament have accumulated around the hobbed bolt, or in the bottom of the extruder body between the hobbed bolt and the heated zone, then re-install the idler and load the new filament.

Hope this helps!

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Follow my Mendel Prusa build here: [julianh72.blogspot.com]

james glanville Wrote:
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> When I want to change colours and the hot end has
> cooled down, I start it heating, and keep trying
> to tug the old filament out. With pla, the
> temperature is about 100C when you can pull the
> entire thing out with a cast of the hot end at the
> end. This was, you don't leave much spare pigment
> to mess up the next colour.

I do something similar to James with PLA: at the end of a print, I let the hot end cool to around 80C, then reverse the extruder for 10-20mm. Then I pull open the idler and pull the filament out, which usually pulls out all the filament down to the nozzle. I leave my hot end empty until the next time, and heat it up with no filament in too. I find I get sticking if I leave the heater on and filament not moving for a long time, though this is with a mendel-parts v9 hot end. I haven't printed with ABS, so don't know if this will work with that.

The problem with running the heater with nothing inside it is the plastic residue will burn and form a hard glaze if it is exposed to the air at extrusion temperature for long. That is why the outside of the nozzle soon becomes black but the inside stays clean.

The hot end must have a design problem if you can't restart it with filament in place. Generally it means the plastic is soft too high up at a point where the bore is bigger than lower down.

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[www.hydraraptor.blogspot.com]