ProtoXtruder NX with IR filament presence sensor

This is a remix of @nhchiu's brilliantly simple ProtoXtruder with a lever like @Prusa3D Nextruder and @Prusa3D IR sensor.

The extruder has less axial play in the gear area. I redesigned the extruder looking from the axis of the filament towards the lever and socket where the filament is fed from the spool.

ProtoXtruderNX v4, featuring an interesting filament sensor filament presence sensor in the extruder design that does not block the filament path with a ball or similar mechanism. In this model, the sensor reacts directly to the movement of the extruder’s idler lever. The IR sensor is connected to the lever optically, not mechanically.

The mounting dimensions are the same as in the original ProtoXtruder, only the 24.6mm dimension will change to 24.8mm and therefore the 6.3mm dimension will change to 6.4mm.

  To build the ProtoXtruder NX you will need:

1. HGX lite kit (affiliate link)- kit parts needed for ProtoXtruderNX:
 - MR63ZZ bearings x 2pcs
 - 3mm shaft (16mm length) x 1pcs

Instead of one original 3x16 shaft from the HGX kit, I recommend the following solution DIN 6325 3x16 mm m6 steel cylindrical mandrel as an axle for the large filament wheel.

 - 3mm shaft (24mm length) x 1pcs
 - large filament gear with pin bearing x 1pcs
 - reduction gear x 1pcs  
 - heat inserts (M3 x D4.5 x H5) x 3pcs
 - M3x8mm BHCS x 1pcs
 - M3x20mm SHCS x 3pcs
 - M3x14mm SHCS x 1pcs

2. Prusa IR sensor (not affiliate link) or a similar clone from Aliexpress (affiliate link).

3. Other parts needed for extruder and lever system:

 - M3x6mm SHCS x 1pcs
 - M2x12mm SHCS x 1pcs
 - M2x8mm SHCS x 1pcs
 - M5 precision shim 7x0.1mm x 1pcs (affiliate link) you can use a properly cut shim from 0.08-0.1mm thick paper
 - Tubular spacer 4x3x8.5mm x 1pcs - I made one out of a brass tube that I have(affiliate link)

 - pin 3x7.5mm x 2pcs or pin 3x8mm x 2pcs (I cut a free pin 3x16 from the HGX gearbox)

 - 683ZZ bearings with U-groove x 2pcs (affiliate link)
 - M3x20mm BHCS x 2pcs
 - M3 nyloc nut x 2pcs
 - spacer 6x3.1x8mm x 1pcs (affiliate link)

 - M3x55mm SHCS x 2pcs trimmed to M3x41.5mm

- Spring 5x15x0.8mm x 2pcs (affiliate link)- I made two from the long one I bought earlier(affiliate link)

Most of the parts are modelled on those needed for the Nextruder lever assembly from Prusa.

4. NEMA 14 36mm pancake motor with 8T gear or 10T gear (affiliate link).

Klipper settings.

I recommend the settings suggested by Bondtech for the LGX (HGX is a clone of the LGX). Bondtech recommends:

rotation_distance: 5.7 #calculated rotation distance - the rotation_distance needs to be adjusted
#rotation_distance: 55 #use this with gear ratio 
#gear_ratio: 44:10, 37:17 #use this with rotation_distance 55  

you can also enter (the previous way is recommended):

#rotation_distance: 5.7 #calculated rotation distance
rotation_distance: 55 #use this with gear ratio - the rotation_distance needs to be adjusted
gear_ratio: 44:10, 37:17 #use this with rotation_distance 55

You need to figure out the Klipper settings for the IR sensor yourself—let us know what settings you have on your printer.

   Print settings.

Nozzle 0.4, layer 0.2, infill 40%, 4 perimeters.

We print without the supports on.

ABS/ASA recommended.

The design considers a print with a layer height of 0.2mm.

However, in order for the parts to fit correctly, the back of the case (newBACK) and both halves of the lever arm (idlerAlever, idlerBlever) have the highest surfaces in multiples other than 0.2mm.

Therefore:
- idler Lever A and idler Lever B should be printed on a separate printout with the 'Precise Z Height' option enabled.

- The newBACK should be printed on a separate print with the 'Precise Z Height' option enabled.
I have added the swivelLever to this print as it is lower than the newBACK and will not interfere with the precise printing of the last surface of the newBACK.

  After printing

After printing the idlerBlever, the integral support (the grey part in the photo) must be carefully removed. 

  Assembly.

Assembly guidelines and instructions will be included in the PDF file.

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Updated 10.10.2025

I have add the assembly manual v0.