Ender 5S1 Filament Cutter

This mod upgrades the Ender 5S1 Sprite Extruder with an integrated filament cutter, enabling clean filament removal without complex tip  tuning.
It’s a simple mechanical solution that improves the reliability of filament unloading and swapping.

Compatibility

• Designed specifically for the Ender 5 S1 with Pugwash’s Linear Rails Upgrade
• it should work the the stock gantry setup but i did not test it and highly recommend the LR upgrade first
• Stock Ender 5 S1 hotend

Additional Hardware Required

• 1× #4 Exacto knife blade
• 1× M3×3 mm grub screw
• 1× M3x22 mm BHSC
• 1× M3 heated insert (length 4 mm)
• most of the original screws
• 3× 683ZZ ball bearings (3 mm × 7 mm × 3 mm)
• 1× Compression spring (Ø 4 mm wire 0.4 mm, free length 15 mm)
• about 70mm of PTFE-Tube* (od 4 mm, id 2 mm)

* if you don't want to shorten the original one

Printed Parts

• Extruder Cap – Covers the extruder and houses the cutter block.
• Cutter Block – Holds a shortened #4 Exacto knife blade.
• Cutter Arm – Lever mechanism for cleanly severing filament.
• Fan Shroud – Encloses the part‑cooling fan.

Print Settings

• Material: PLA or ABS/ASA/etc. - PETG is not recommended
• Layer height:
  • .1mm for Extruder Cap, Cutter Block and Cutter Arm 
  • .2mm for Fan Shroud
• Infill: 20–30 % Gyroid
• Orientation: All STL and 3mf files are preoriented to the correct print orientation
• Support:
  • Enable supports for the Fan Shroud.
  • All other parts print well without supports.
    If the bridging on the Extruder Cap appears imperfect, you can manually add supports in the area for the Cutter lock if necessary.

Assembly

Step 1 - Assembling the  Cutter Block

1. Shorten the #4 blade to approximately 26 mm in length.
   Ensure it is not longer, otherwise it might block the filament path.
2. Insert the heated insert into the Cutter Block.
   (Tip: You can place the blade inside the slot first to act as a depth stop, ensuring the insert doesn't get pushed too far.)
3. Place the spring into the Cutter Block.
4. (If not already done) Insert the blade into the slot with the flat side facing upwards.
   Secure it lightly using the M3 grub screw.
   Do not to overtighten it, to avoid damaging the Cutter Block.

Step 2 - Assembling the Extruder Cap

1. Ensure that the filament path is clear.
   If necessary, carefully use a 2 mm drill bit to remove any obstructions.
2. Insert the one 683ZZ bearings into the designated slots in the Extruder Cap.
3. Install the Cutter Block into the Extruder Cap.
   Make sure that the spring properly seats and locks into its position inside the Cap.

Step 3 - Installation of the Extruder Cap

1. Remove the existing fan shroud from the extruder assembly.
2. Unscrew the two main bolts that secure the extruder to the gantry.
3. Gently lift the extruder slightly out of its mount to disconnect the PTFE tube from the hotend.
4. Loosen the screws holding the stock extruder cap in place, including the side screws on the Bowden feeder section.
5. Replace the old cap with the new custom cap.
   Make sure:
   • The extruder gears can rotate freely without binding.
   • The tensioning lever also has enough clearance to move properly.
6. Reattach the cap using the two screws removed earlier.
7. Reattach the Bowden feeder 
8. Shorten the old (or a new) PTFE tube to approximately 70 mm and fully reinsert it into the hotend.
9. Reinstall the extruder by pressing it onto the PTFE tube and securing it:
   • Use one of the previously removed bolts through the main gantry mounting hole.
   • (Optional but highly recommended for LR-Upgrade users):
     Secure the stepper motor additionally using two side-mounted M3 bolts for improved stability.

Step 4 - Assembling and mounting the Cutter Arm and Fan Shroud

1. Insert the remaining bearings into the designated slots of the Cutter Arm.
2. Attach the Cutter Arm to the Fan Shroud using the M3x22mm screw on one side.
   Important:
   • Before assembly, press the Cutter Block into the Extruder to ensure correct alignment.
   • Do not overtighten the screw — the Cutter Arm should still move freely without binding.
3. Secure the other side of the Fan Shroud to the extruder using one of the original screws removed earlier.

Final Adjustments

After the mechanical installation is complete, a few additional steps are needed to fully integrate the filament cutter into your system:

• Actuator Design:
  You will need to design or add a small actuator for the gantry to press against, which will trigger the Cutter Arm. This ensures reliable cutting action during filament unload operations. The shape and placement will be highly dependent on your setup.
• Macro Updates:
  Update or modify your printer’s macros, especially the filament unload macro.
  The unloading process must now include the cutter activation to properly sever the filament before retraction.

The Happy-Hare Wiki on GitHub provides an excellent graphic explaining how the cutting process should work.
You can easily adapt some of their macro examples to fit your own setup and needs.

Troubleshooting

• Blade gets stuck in Extruder Cap:
  Carve or drill a little hole into the Blade at the position the grub screw is pushing against. That way the grub screw can really lock the blade in place

Changelog

Version 1.1 - Fix wrong diameter for heated insert in cutter block

Version 1.0 - Initial Release

Sources

Full Ender 5S1 model used for rendering the instructions by Hoon
Fan shroud inspired by Pugwash