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bob-hepple

What Defines the Length of the Bowden Tube

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Hope someone can shine a light at what defines the Length of the Bowden tube..

Reason My Um 2 has a Bondtech and the bowden has a nasty habit of going nearly flat not upright,, this makes the entry into the top of the head and the exit from extruder, under pressure, and I would think cause more friction pushing the material through...

So I thought as long as the tube was NOT being stretched by the head moving across the med to all 4 corners that would be fine...

Any thoughts before I cut...

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Pull the tube out of the hotend, take it to the front right corner (the furthest corner), see how long you can stick it under the height of linear rod without too much bending.

The next thing you need to concern is the fast forward filament run while loading filament. You need to make sure the extruder doesn't outrun your Bowden tube, otherwise the filament is going to shove into the nozzle and be grinded by the extruder.

In the 2.1 Marlin firmware, default Bowden length is set to 705mm (set as FILAMANT_BOWDEN_LENGTH in Configuration.h tab).

And the fast forward length is FILAMANT_BOWDEN_LENGTH-50mm (set as FILAMENT_FORWARD_LENGTH in UltiLCD2_menu_material.h)

If you cut the Bowden tube, better subtract 705 with the length you cut off.

With your problem of Bowden tube not being up right, you could also try a Bowden tube hook to restrain the position. I made one before: http://www.thingiverse.com/thing:2154124

Edited by Guest

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yyh1002

thanks for the reply you made some points that I didn't think of ?? which is exactly why I asked the question?? thanks..

I will look at the Boden again.. The Ums 2 is not what it started life out as std.. and I guess I replaced the tube 2 or 3 times.. so I doubt it is std length I will look at the fast forward and check..

I also have another printer Not Um (sorry) which is heavily modded and I suspect that machines bowdens are well out, I will check the H files for the length before I cut 25mm off...

Thanks

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