Reverse Bowden Tap

My first “thing”; a 360 degree adjustable and stackable reverse bowden system designed for my Prusa MK3s frame. It swivels and looks like a tap, so I'm calling it the "Reverse Bowden Tap" 😊

Design

I designed this for my custom dehydrator dry box which can hold 3 spools. I wanted something that could hold my filament and allow for easy switching without needing to back the filament out and this led to my stacking concept.

You can extend this design further if you like, but I have also provided bolt lengths to accommodate for stacking 3 or 2 Bowden tap arms.

BOM

You just need 2 x PC4-M6 and a length of 4mm OD PTFE tube per arm.

OR; My 3D printable PC4-M6 print, Locking bowden connector

Versions

There are two version of the tap arms, standard and short body. The short body might be preferred in a stacked scenario. There are also two versions of the base, one inserts into hex fitting on either of the stock Prusa MK3 Z Axis tops. The other uses a customised Z Axis top to replace the stock part and simplify installation.

Standard Hex Base

There are two parts in this design, the body and fastening nut. The body slots into the top of the Z Axis top and the nut is fastened from below to keep the base firmly attached. The nut can be hand tightened, but there is also a 4mm hex fitting so you can use a hex key from the top through the base. If using the hex key, remember to reverse your direction 😊

Unfastening standard base

Custom Z Axis Top Base

For all intents and purposes, it is the same as the stock part, but updated to accommodate for the arm and bolt. The STL file is for the left, but you can use your slicer to mirror the file if you want a right hand base.

Custom Bear 2.0 Z Axis Top Cap Base BETA!

I do not have a bear 2.0 frame so I am unable to test the fitting. I have modified the part to accommodate for the arm and bolt and the clearances look good, but it is untested. If you do try it and it works then do let me know so I can update this description.

NB: I had to increase the height to 4mm so it will be a 1mm higher than the Z Top. I can update this model to have a matching height if people request.

Arms and Bolts

The bolt is used to fasten the arm to the base. To reposition, simply loosen the bolt, adjust each arm and then re-tighten. The bolt length will vary on the configuration, i.e. short body vs standard or stacked.

Adjusting arm and base

Part Configuration

First, select your base

Standard Hex Base:

• Standard Hex Base.stl
• Standard Hex Base Nut.stl

Custom Z Axis Top Base:

• Custom Z-axis Top Left.stl

Custom Bear 2.0 Z Axis Top Cap Base BETA:

• custom-bear-20-z_end_cap-v1.stl

Then, select your arm setup

Short Body:

• Short Arm PC4-M6.stl
• Short Arm Top Bolt.stl

Standard Body:

• Standard Arm PC4-M6.stl
• Standard Arm Top Bolt.stl

Stack combination 1:

• 1 x Short Arm PC4-M6.stl
• 1 x Standard Arm PC4-M6.stl
• 1 x Stacked Arm Top Bolt 1.stl

Stack combination 2:

• 2 x Short Arm PC4-M6.stl
• 1 x Stacked Arm Top Bolt 2.stl

Stack combination 3:

• 2 x Short Arm PC4-M6.stl
• 1 x Standard Arm PC4-M6.stl
• 1 x Stacked Arm Top Bolt 3.stl

Notes

• Remember if you want a Custom Z Axis base for the right, just mirror the part in your slicer.
• The nut for the standard base has a 4mm hex fitting so you can tighten it from the top (just remember to move in the opposite direction :-P)
• There is an inner chamfer between the two PC4-M6 fittings that should guide filament through when loading.
• I'm also using the standard hex base.

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Tips

I’ve spent a bit of time developing the design and printing for trial and error fits. I do not expect anything, but If you did find this helped and saved you time then do feel free to buy me a coffee or beer, it would be appreciated! 😊

Print instructions

• Threads work well using 0.20mm layer heights using either PLA or PETG. I left the PC4-M6 threads a little tight.
• You won’t need any supports, but it might result in a flatter base if you printed the Customised Z Axis Top Base with supports as there will be bridging around the fitting insert.
• 2 to 3 perimeters with 30% infill is what I am using.

Optimal part print orientation.