This is a filament guide for a Tevo Tornado if filament is coming from above, for example by using a filament spool holder that sits on top of the frame like https://www.thingiverse.com/thing:2336783 or https://www.thingiverse.com/thing:1213419
If you don't use a filament guide in front of the extruder in this case, you may experience your filament grinding into the plastic entrance part of the extruder - therefore I designed this guide. It attaches to the extruder mounting brace and uses the original hex nut.
You will only need a 608 ball bearing.
I will probably add an optional dust cover in an update so the bearing stays mostly dustfree.
Might work on CR10 as well, but as I only have a Tornado, I cannot compare the mounting situations.
Update 1: Added a horizontal version by request - this means the filament is coming from behind the printer - not tested in real world, waiting for feedback.
Update 2: Added another horizontal guide for filament that is coming from in front of the printer.
Update 3: Added Fusion360 files so users can download and modify easily
Update 4: I added an untested "sensorbase.stl" which is a fusion of my design and thing https://www.thingiverse.com/thing:3011383 - you have to print the lid from the other thing and test if that will all work together for you...
Recommended printing orientation is the same as the one used in the final usage.
If you want, you can add a support to the area above the hex nut drill hole that overhangs - but it is not neccesary, depending on your print settings and used filament regarding overhang ability.
Just add a bearing of type 608 (inner diameter 8mm, outer diameter 22, width 7mm) by gently pushing it between the two side walls until it snaps to it's fittings.