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I've attached the piece I'm using, it reduces the space available for the filament to buckle, and seems to have resolved my buckling filament issue.
It goes over the knurled nut on the bowden adapter, obviously the V shape has to be aligned with the rollers and the short end goes to the outside of the extruder.

As a warning It's not perfect and It's difficult to print, it requires support for the print, and the clearance is tighter than I would like.
I printed it in PLA, which has adequate bearing like properties, so even if the rollers rub on it slightly there is little friction.

Yeah- I need this!
After tightening up the extruder idler axle I am getting the kinking filament issue all the time. Hopefully this weekend I will have time to get it printing enough to print up one of these. I'm a little frustrated with it right now.

Also note if your filament is kinking often, your extruder alignment to the bowden tube adapter plate could be off.

Mine was. i ended up having to file down one end of the bowden tube plate to get it to shift over far enough to line up true.

lazerusrm wrote:Also note if your filament is kinking often, your extruder alignment to the bowden tube adapter plate could be off.

Mine was. i ended up having to file down one end of the bowden tube plate to get it to shift over far enough to line up true.

Mines aligned, all it takes is the abs to catch somewhere and it buckles.
It's a design flaw IMO,wouldn't matter with 3mm filament because it's so much stiffer, but with 1.75mm abs, it's soft enough that you can get this failure.
It should be noted I only ever saw this on agressive retract/resumes, but that's needed with the Bowden tube.
This part has resolved my issue, but it could use another design pass.

I had problems with filament bucking in the beginning.

After adjusting the extruder tension correctly, and alignment, i have not had a buckling issue in a long time, after probably 100+ hours of print time or so.

but i did have it happen alot in the beginning. it was due to the extruder being to tight, and poor alignment.

This cap worked for me, thanks!

I started with some white abs I bought from amazon. No issues. Then I bought some orange from seemecnc and the first few prints were better than I was getting with the white (fewer blobs & strings). But at some point, it started kinking and would not quit. I kept trimming off and refeeding it in but it would just do it again. Switched back to white filament and no problems.

So printed the this cap, and filed it until filament passes freely through the little hole right up into the bowden adapter and now I'm back in business with the orange.

I try to slice it with Slic3r and this comes:

23:48:29.265 : <Slic3r> Warning: The input file contains a hole near edge 1.000000-3.000000 (not manifold). You might want to repair it and retry, or to check the resulting G-code before printing anyway.
23:48:29.328 : <Slic3r> => Processing triangulated mesh
23:48:31.046 : <Slic3r> The model has overlapping or self-intersecting facets. I tried to repair it, however you might want to check the results or repair the input file and retry.

Why is that happening to me, what setting should I post so you can verify?
Here is some:

; layer_height = 0.2
; perimeters = 1
; top_solid_layers = 0
; bottom_solid_layers = 0
; fill_density = 1
; perimeter_speed = 20
; infill_speed = 20
; travel_speed = 100
; scale = 1
; nozzle_diameter = 0.5
; filament_diameter = 1.71
; extrusion_multiplier = 1
; perimeters extrusion width = 0.55mm
; infill extrusion width = 0.55mm
; first layer extrusion width = 0.55mm

You may have to run it through netfabb basic (it's free), it's beyond me why every CAD package I've ever used produces STL files with errors.
I sliced it with KISSlicer and it worked as posted.

Polygonhell, you are a life saver my friend!

I've been fighting with this issue for days and couldn't get anywhere. I managed to print it off in nylon (thinking it would cause the least amount of friction) and used some jewelers files to finish it off so it fits perfectly.

I still wish I knew what changed and caused this problem to start happening. It worked great for about two weeks then all of the sudden started buckling.

Sounds to me as though you are probably experiencing too much back pressure on your extruder, which could be caused by any number of things. If you are getting consistently solid infill's, you probably have the correct filament diameter and steps per e. If not, then those are your likely culprits. If your infill's look good, I would suggest either attempting to print slower or printing at the same speed with higher temp, thus allowing the filament to "liquefy" easier.

Would it be ok for me to post this piece on Thingiverse? I started printing flexible filament and this piece has helped.

Go for it, the original piece was designed for the original Steve's extruder, which hasn't been mad in a LONG time.
But if it's useful, bu all means repost it.