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3D Printer filament breaking in extruder? Answered

Several of my recent 3D printer projects have failed in the middle because the PLA filament seemed to break in the extruder and cannot be pushed out the nozzle. Has anyone had this experience?


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3 years ago

Yes, only too often...
That is why, for example I now try to avoid these small rolls in favour of the bigger diameter ones.
In many cases, especially if the filament is properly dried, you only have about 5 layers until the stuff starts to break.
I found a workaround due to the size and layout of my machine, maybe you can try similar:
Trick is to get the filament straight and a bit more flexible.
For a test you can place the roll so you can direct the filament over a heat lamp (or hair dryer for a small test).
Have the filament supported by rods, rings or whatever you have at hand to force it in a straight line over the heat source.
Does not matter if after that you have another meter to go to the extruder.
What you want is the following:
Filament is forced to get straight,
Filament goes over the heat source so it warms up just enough to loose this damn curl,
After the heat source the straight part should be long enough to allow the filament to cool down to room temp again - You don't want soft PLA to enter your extruder!

Why (I think) this works:
The twisted filament is acting like a spring and if the curl goes the wrong direction this spring tension plus the extruder mechanics can be enough to make it snap.
If the filament is straightened out before entering the extruder the forces are all much lower and won't change with the curl of the plastic.

What to check before trying this:
If breaking PLA causes a problem then usually directly at the pressure wheel causing the transport to stop as there is nothing left to grab.
If that breaking happens in other parts of your extruder you should check for free play, e.g. the diameter of holes and liners the filament passes through.
Once through the driven part it should not matter if the filament is broken or not as it will be forced into the heated part anyway.
If your extruder is away from the hotened and you use a tube where the filament breaks in then the straightening will definately help you.
But the same is true for reducing the pressre on the wheel to the minimum you can do without risking it to slip and grind.