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Bowden friction stops PVA


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Posted · Bowden friction stops PVA

Hi all,

I've just received and installed the dual extrusion kit on my UM1. Great support for the building (it was a lot of fun, too) but I'm now trying to use some PVA filament in the new bowden tube and I can't even get it half way through the tube before the friction stops it going any further.

Has anyone else experienced this?




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    Posted · Bowden friction stops PVA

    P.S. Just had a go at pushing it through the original UM1 bowden and it goes through with no issues whatsoever - super smooth.

    Has the material changed since UM1?


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    Posted · Bowden friction stops PVA

    When you have friction problems with filament inside the Bowden tube, it's always a good idea to measure the diameter of the filament. If the diameter is larger than 3.00mm, you most probably will never succeed.

    edit: I don't know what happens to the diameter when PVA is stored in a non-dry environment, it may swell.


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    Posted · Bowden friction stops PVA

    Normally I'd say put some sewing machine oil in it, as more often referred to in this topic, but I don't know how PVA reacts to that. You could test it on a little piece first.


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    Posted · Bowden friction stops PVA

    Thanks for the thoughts.

    A bit of an update:

    - The PLA fits through the new bowden tube fine.

    - The PVA fits perfectly well through the old bowden tube that was supplied with the UM1, it only gets stuck in the new tube that came with the Dual Extrusion Kit. I'm thinking of replacing the new tube with one like the old one.

    - The feeder mechanism on the DEK seems quite unreliable. I'm going to tweak it some more today but at the moment it is hit or miss as to whether it pushes/pulls the filament at all (even the PLA).


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    Posted · Bowden friction stops PVA

    Further update:

    Decided to walk before I try to run and got the UM1-DE working with PLA running through both extruders. The first print went well, although I'll need to tweak the feed settings (or something, as it wasn't pumping out quite enough PLA to keep up with the head movement) for the second (new) extruder. The first (old) head worked perfectly though.

    I'm going to do a bit of PLA printing with different colours, etc, before I try rushing on to PVA tests. Still looking forward to them though.

    Does anyone know if it's possible to buy the old bowden tube anywhere, or its specs so I can buy a generic piece?



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