Parametric PTFE Tube Guide for Filament Sensor

The Problem

You're feeding filament from a dry box, a wall-mounted spool holder, or any location not directly above your printer, and the filament enters the runout sensor at an angle. This applies lateral force to the sensor's input hole, causing friction, binding, and unnecessary drag — especially with stiffer filaments such as PETG or nylon.

The Solution

This adapter fits onto the filament runout sensor and adds a guide tube that keeps a PTFE tube aligned perpendicular to the sensor input face. The adapter captures the filament well before it reaches the sensor, straightening its path and eliminating side-loading that causes friction and jams. The filament glides smoothly through the tube and enters the sensor cleanly on-axis, regardless of where your spool is located. It can also be used on the sensor output if desired. 

Features

• Fully parametric — every dimension is adjustable through MakerWorld's built-in parameter editor, so you can adapt it to other sensors or setups without touching OpenSCAD
• Friction-fit sleeve slides onto the sensor body with no hardware required
• Adjustable guide tube with configurable length, bend radius, and rotation angle to route the PTFE tube in any direction
• Entry chamfer funnels the PTFE tube into the guide for easy assembly
• All values are adjustable via the Customise panel.

Default Dimensions (Creality CR-10 Smart Pro)

• PTFE tube OD - 4 mm - Bore diameter for the tube
• Sensor face width - 31.6 mm - Inner width of the sleeve
• Sensor face height - 20.3 mm - Inner height of the sleeve
• Fit clearance - 0.15 mm/side - Tightness of friction fit
• Hole position - 15 mm × 8 mm - Filament hole location on the face
• Wall thickness - 2 mm - Adapter and guide tube walls
• Overhang - 15 mm - How far the sleeve grips the sensor
• Guide length - 20 mm - How far the tube extends from the face
• Bend radius - 0 (straight) - Curved guide for tight routing
• Guide rotation - 0° (up) - Direction the guide points
• Entry chamfer - 1 mm - Funnel at the guide opening

Printing Tips

• If you are using the bend radius feature, allow a small tolerance in your PTFE tube size for easy insertion.
• If a bend is used, the guide tube may require supports depending on the rotation angle.
• When adding supports, consider how they will affect the inside of the bend radius feature. A bent pipe is hard to clear, so printing with the tube facing up is likely optimal. 
• Perform a partial-print test fit on your sensor and adjust `fit_clearance` as needed — increase for a looser fit, decrease (or set to 0) for a tighter grip.
• PLA recommended – not much strength needed.