Starting a New Filament?

One thing I've noticed is that, once you've run to the end of a piece of thermoplastic filament, starting a new one is a serious pain. If you just feed it in behind the last piece, it almost invariably jams when the gap reaches the top of the PTFE barrel. Right now, I have to take the extruder apart and manually push the old piece far enough down to start the new piece.

Anyone come up with a solution to this? I'm halfway considering making some sort of filament splicer or maybe creating an access panel that allows me to guide the new piece into the PTFE barrel. The only other solution I can think of is to use extremely long pieces of filament to avoid starting new ones.

If you keep an eye on your filament feed you will find that you can loosen the pump and easily pull the old filament out while the extruder is hot. Mind, you have to do this while you can still get a pair of pliers on the end of the filament sticking out of the pump.

Once you have the old one out it's a pretty simple matter to feed the new one in. As you say, the trick is in getting the filament to feed into the PTFE barrel. I've redesigned mine to where I have a copper slightly flaired feed assembly sitting on top of the PTFE block that I use for a thermal break. It makes life a lot easier.

I keep my filament on a reel that holds 2.5Kg which solves the problem.

I have managed to do in flight refueling though. I push the new filament with pliers until the screw bites. The idea is that you exactly line up the pump channel with the hole in the PTFE using the slots in the clamp and slightly taper the hole into the PTFE. That way it has nowhere else to go but into the hole.

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[www.hydraraptor.blogspot.com]

I might have to start using a reel. It's amazing how much filament you can go through, just running tests.

nophead--

How do you prevent your filament from twisting? Is the real able to twist in some way? Please explain because I have sorting through this dilemma right now.

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Jay

Hi Jay,
The details are here [hydraraptor.blogspot.com].

If I put a short piece of filament in the extruder then it does rotate. However, the reel does not let it and HDPE is pretty rigid it so it doesn't twist. I don't know if CAPA behaves the same way yet but I will let you know later this evening hopefully.

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[www.hydraraptor.blogspot.com]

I should also have added this mod for taking up the slack when my z-axis raises.

[hydraraptor.blogspot.com]

Probably not required for Darwin but needed for moving table like McWire.

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[www.hydraraptor.blogspot.com]

Vik has an alternative solution which is shown here:

[blog.reprap.org]

It looks nice and simple but I can't understand how it works!

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[www.hydraraptor.blogspot.com]

I think it's like pulling string from the inside of the coils as in the string boxes from an old tin box with a small hole in the middle of the lid (well I'm sure it was my granny that had one)

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Ian
[www.bitsfrombytes.com]