Highend filament guide for Ender 3

The lead times of the Prusa Mini are still painfully long. So despite the fact that I have one on back-order since quite while, I decided to get an Ender 3 Pro, in order to have a backup to my Prusa i3 Mk3S during the Pandemic.

For those that are interested in my take on comparing the Ender 3 Pro to an i3 Mk3S, here it is:

Well, they certainly play in different leagues. Especially when you need very precise fittings into other parts, the Prusa is well ahead. But the Ender 3 does develop well usable parts es well, if a few tenth of a millimetre are not of importance. The biggest difference in my take is that the Prusa works out of the box and there is basically nothing that I would dare to try and improve, because it is extremely well tune already. In contrast to that, I had to do quite a bit of changes on the Ender 3 Pro to make it usable for me (but with these changes it is a very reliable workhorse for non critical parts now):

• I had to adjust and tighten basically all screws. Especially the excenter screws on the wheels were adjusted much too tight, causing the rather soft wheels to have a flat spot, so they rumble on the rails (fortunately that goes away over time after you adjust it correctly)
• The stepper motors were much to loud, making a horrible noise in the room, so I purchased and installed a Creality board with quiet drivers
• The fans also created unbearable noise, so I had to replace them with Noctua fans, which make a hell of a difference. To do that on the power supply required some heavy metal work, because there is no 60x10mm Noctua fan. The fact that the hotend fan runs on 24 volts required me to add a 12V switched voltage regulator for the 12V Noctua fan. With these changes, the Ender 3 Pro feels even quieter than the Prusa now, thanks to its (not so precise of course) rubber wheels.
• The bed was not flat but bent, so all attempts of manual leveling had to fail. The only sensible solution was to add a BLTouch sensor to correct that in software. Since switching on the BLTouch code in the Marlin Firmware compile did cause the code size to exceed the memory size of the 8 bit board that I had just installed for the quiet drivers, I changed again to a 32 bit board which works perfectly well now (after I had finally succeeded to build Marlin 2.0 for that board with all the settings that I wanted, which is not complete rocket science, but also not for the faint of heard)
• The plastic extruder mechanics is said to fail early, so I replaced it by a metal one right away.
• The filament guidance from the spool into the extruder mechanics is just one big design flaw. And this is where the printed parts come into the game that I publish here. The following is the original text that I published on Thingiverse:

Many of us Ender 3 users have noticed that pulling the filament into the extruder from the side, while the spool is mounted on the top, is one of several design decisions from Creality that leaves room for improvement. A number of users have reported they have seen significant under extrusion caused by this design, as the filament is not sliding into the extruder willingly, if it is bend sharply around the edge of the extruder inlet.

There are a number of fixes for this problem on Thingiverse and I am sure they help to do the job better than the original Creality design. But with filament not sliding very well over these static filament guides (especially PETG has a quite rubbery surface), I have decided I want a high end solution for this problem. My design spec says that there shall be no need at all for the filament to slide over any kind of surface. So the only mechanical solution that seemed appropriate to me was by means of a nice big pully with a metal ball bearing.

Here is my design, I hope you like it. If you print and use it, please be so kind to post a picture.

Happy printing and stay safe everyone!

Print instructions

This is what you need to do get it printed and assembled:

Print the axis and the spring washer at 100% infill and with a small layer height for good detail quality (Frankly, the axis did not come out of the Ender 3 perfectly, so it will need a bit of sanding to fit the ball bearing over it. I have cheated a bit by simply printing this part on my Prusa i3 Mk3S, which did the job flawlessly. My guess is that the cooling of the Ender is insufficient for such small parts with their very short times per layer.)

Print the base lever and the pulley at 20% infill, that makes it tough enough. As layer height 0.2mm is fine.

If you have a M3 thread cutter, use it to cut a thread into the two smaller holes of the base lever. If not, drive in a M3 carefully to cut the thread (having the part clamped into a wise typically makes sure that the part does not crack and worming up the screw with a hair dryer can help as well). Then use two M3x6 screws and screw them in from the thicker side of the U-shape, but hold short before they reach into the gap part of the U-shape.

For the axis, also drive in a M3 thread into the hole at the bottom with a thread cutter or a screw. Then mount the axis to the base lever with a M3x10 screw. Have it sitting on the long flat backside of the lever, the screw head sticks out towards the front (where the smaller part of the U-shape sits). Have a look at the pictures if you are still unsure how to mount the part together.

Press a 11x5x5 standard ball bearing into the pulley hole. If that goes too hard, use a file or some sanding paper to slightly widen the center hole of the pulley.

Simply put the pulley with it's ball bearing on the axis and snap the spring washer on to the axis to keep the wheel it in place.

Now put the base lever on the backwards facing outer edge of your left Z-axis cart and clamp it tight with the two M3 screws from the back.

You are all set, your filament will be guided very gently around this 90° bend from now on and does not need to slide over any kind of surface.