Bowden tubes are a critical component in 3D printers that use a Bowden extruder setup. This guide will provide an in-depth look at everything you need to know about Bowden tubes, including how they work, the different types, tips for installation and maintenance, and how to choose the right tube for your printer.
What is a Bowden Tube?
A Bowden tube is a flexible tube that guides filament from the extruder motor towards the hot end in a Bowden extruder system. It essentially replaces the filament path through the extruder body in a traditional direct drive setup.
The tube needs to have low friction and be relatively rigid to cleanly guide the filament to the hot end. Bowden setups allow lighter extruder carriages by removing the weight of the filament drive motor. This improves print speeds, allows faster direction changes, and reduces ghosting artifacts.
How Bowden Tubes Work
In a Bowden system, the extruder motor is mounted separately from the hot end assembly. The motor feeds filament into one end of the Bowden tube, which guides it to the hot end.
The tube needs to provide low friction filament guidance to prevent grinding or skipping by the extruder. It also needs to be rigid enough to prevent excessive bending or compression under filament force. Poor tube quality can result in clogs, uneven extrusion, and print quality issues.
Properly constraining the tube ends is also critical for good performance. The tube must be anchored firmly at both ends to prevent movement or separation during printing. Failure to anchor it can allow the tube to come loose, resulting in leaks and clogs.
Types of Bowden Tubes
The most common types of tubing used in Bowden systems are PTFE, PEEK, and advanced composites like fiber-reinforced tubes. Let’s look at the properties and use cases of each.
PTFE Tubing
PTFE (polytetrafluoroethylene) is by far the most common Bowden tube material. Brand names for PTFE include Teflon and Chemours. The slick, low-friction surface makes it idea for guiding filament smoothly with minimal resistance.
The biggest downside is its tendency to soften and deform at temperatures above 240°C. For this reason, PTFE tubes should not be used with high-temperature filaments that require hot end temperatures above 240°C.
PTFE tubes suitable for 3D printing come in a variety of inner diameters, usually around 1.9-2mm. Thicker walls provide more rigidity while thinner walls allow tighter bend radii. Popular PTFE tube choices include Capricorn and TH3D tubes.
PEEK Filament Tubing
PEEK (polyether ether ketone) tubing offers better heat resistance than PTFE, with ability to withstand temperatures exceeding 300°C. This makes PEEK Bowden tubes suitable for printing high-temp materials like PEEK, ULTEM, and some nylons.
PEEK has excellent chemical resistance and low friction. But it is also much stiffer than PTFE. This can make installation more difficult in some printers, potentially kinking inside tight radii. Hardened steel tube couplings help overcome this.
Reinforced Composite Tubing
Reinforced composite Bowden tubes contain an inner PTFE or PEEK liner, surrounded by layers of fiber reinforcements like aramid fiber. The composite layers make the tubes extremely rigid and resistant to kinking or compression.
Popular composite tubes like the Capricorn XS tubing combine the benefits of PTFE with enhanced rigidity. The composite layers hold their shape better when bent and improve filament path consistency. They are more difficult to install however.
Bowden Tube Installation Tips
Proper installation is critical for getting the best performance from your Bowden tubes. Here are some key tips:
- Cut tubes to appropriate length. Excessively long tubes increase friction and can sag, while too short increases leaks.
- Install tube couplings carefully to avoid crushing or kinks. Ferrules help grip the tube.
- Insert tubes fully into the hot end and secure with clips. Prevent leaks.
- Anchor both ends securely. Use anchors that grip the tube, not just the couplings.
- Gradually bend tubes during installation. Avoid tight kinks which obstruct filament.
- Check path is smooth and unobstructed. Trim any excess length after verifying fit.
Maintaining Bowden Tubes
With regular use, Bowden tubes can wear out over time. Signs like reduced print quality, uneven extrusion, or leaks indicate a tube needs replacement. Here are some maintenance tips:
- Inspect tubes periodically for any cracks, deformations, burns or leaks. Replace if deteriorated.
- Replace PTFE tubes showing discoloration from overheating. Burnt spots increase friction.
- Clean tubes externally if they accumulate material debris and residue. Avoid internal abrasives.
- Replace tubes preemptively after extensive use. PTFE and PEEK both wear with abrasion over time.
- Lubricating tube internals is generally not recommended – it can attract contaminants.
Choosing the Best Bowden Tube
The optimal Bowden tube depends on your specific printer and use case. Here are key factors to consider:
- Temperature range – PTFE for <240°C. PEEK or composites for higher temps.
- Filament abrasiveness – More rigid tubes like PEEK better withstand abrasive materials.
- Bend radius – Thinner PTFE walls allow tighter bends. Composites hold their shape better.
- Rigidity – Stiffer tubes improve consistency but are harder to install.
- Inner diameter – Matched to filament for minimal slop. Around 1.9-2mm is typical.
- Quality – Precision manufacturing and robust design prevent issues. Buy from reputable brands.
With a quality tube properly installed, a Bowden setup can provide fast, reliable printing and expanded material compatibility. Pay attention to signs of tube wear, and replace them periodically for peak performance from your printer.
