This is an upgraded filament guide for TEVO Titan extruder. I am not sure whether this fits original e3d Titan.
This solves problems with extruding flexible filament.
What is different:
The original guide has a 5mm diameter conical entrance for the filament, which is some 7mm deep and then meets your PTF bowden. This is a perfect place for your filament to curl up and get stuck. My upgraded version is designed so that your bowden gets all the way through the guide and meets drive nut and guide pulley. As soon as the filament leaves the drive nut, it is trapped in a tight bowden tube, which is perfectly smooth all the way to the hotend.
- The filament guide in my Titan extruder was originally not in a perfect line with the guide pulley. To solve this, I made the new one slightly off-set. You can see the difference in the photo (the photo is showing a prototype which was misaligned slightly too much).
There are two versions, the difference is the hole diameter. If your printer prints holes smaller, the 4,1mm will probably need drilling. The 4,5mm should be fine right away.
After getting the bowden through, trim it as seen in the photo.
For easy installation, load the bowden with both the guide and the "one-way lock nut (or what you call the part)" into the extruder body from a side, while the transparent extruder part is still off.
The spring that pushes the guide pulley likes to shoot out while the extruder body is open, so get it out at the begining of the installation and put it back right before you screw the transparent part back on.
- Reloading a filament gets a little bit more difficult as the entrance is now much smaller than before, but it was not a big issue for me.
EDIT: I updated the design for even better fit. I uploaded two versions, one with 4,1mm hole which will probably need drilling if your printer prints holes smaller and a 4,5mm one, which should be usable right away, even if your printer makes holes smaller.
This version is also longer than the previous one, the gap between the pulley and drive wheels is now less than 0,5mm.
The new version is slightly off-perpendicular to the print bed, which is made on purpose for a better alignment (the original TEVO was also not perpendicular).
In one picture, I highlighted a bolt which is not originally in the TEVO extruder. I added it because I found out that the release arm of the extruder has a really bad wobble to it, due to the fact that its axis is plastic and only attached on one side, which causes it to bend. First, you have to drill the hole in that axis a bit bigger for the bolt to fit freely (but without wobble). If the bolt goes in tightly, it stretches the whole plastic axis and prevents the release arm from moving freely. The bolt head then fits exactly into a mould which is in the translucent part of the extruder and stiffens the axis. This also allows you to tighten the tension spring of the release arm, so you get better grip of the filament.
Please, let me know how it works for you, this is my first upload and any feedback will encourage me to make more useful things.