Unless you have a higher-end printer with a direct drive extruder, your FDM printer likely has a Bowden Tube.
But what is a Bowden Tube? How do they work? How do you install them correctly?
What is a Bowden Tube
FDM 3D printers take filament from the spool and feed it into the hot end using a stepper motor. Direct drive printers have stepper motors built into the extruder head, but cheaper 3D printers have the motors off to the side. You can find the motor attached to the printer’s frame.
The long tube that delivers the filament from the stepper motor to the extruder is called a Bowden tube.
Neither method of delivering the filament to the hot end is perfect. Buth comes with their advantages and disadvantages.
Pros and Cons of Bowden Tubes
- Lighter Printhead Carriage: Mounting the stepper motors to the printer’s frame reduces the weight of the print head. Heavy print heads require more time to accelerate and decelerate the print head when tracing corners or rounds, a problem the Bowden tube solves.
- Faster print speeds: Since the carriage is lighter, the x and y motors can accelerate and decelerate faster. Bowden tubes make it possible to print at faster speeds and reduce total print times.
- More accurate prints: When the stepper motor is mounted to the print head, the movements of the motor can create vibrations that carry through the extruder nozzle producing less accurate prints. Bowden tube configurations have less vibration in the extruder carriage, making layers smoother and more accurate.
- More stringing and blobs: Internal friction within the Bowden tube can produce a delayed response from the stepper motor. The delayed responsiveness can result in stringing between parts or zits and blobs from over-extrusion. To reduce over-extrusion between transitions, you can fix stringing by adjusting the retraction distance and speed.
- Nozzle Clogging: Improper installation of a Bowden tube, or high retraction settings, can clog the printer’s nozzle.
Types of Bowden Tubes
If your 3D printer uses a Bowden tube configuration, it likely comes with a standard plastic Bowden tube. The stock tube is good enough for most PLA printing, but it won’t stand up to the high temperatures of other filament types.
If you want better performance, you’ll want to upgrade to a PTFE, such as the Capricorn Bowden tube.
We’ll cover the pros and cons below to help you decide whether upgrading is right for you.
The stock Bowden tubes found on most budget-friendly 3D printers consist of a basic tube made from heat-resistant fabric. Sock Bowden tubes work for most 3D printing, but they have their drawbacks:
- They aren’t as heat resistant as you think: Stock Bowden tubes can resist the temperatures from printing with PLA. However, the stock Bowden tube will fail if you print with a filament requiring higher temperatures, such as PETG or other more extreme materials. After printing at a higher temperature, the end of the tube that feeds the hot end will soften and deform. The deformation leads to clogging and inconsistent extrusion.
- Aren’t very stiff: The standard Bowden tube is not very resistant to external pressure. While installing the tube, it’s common for people to crimp it, causing it to deform.
- Bad surface finish: An inconstant surface finish creates friction, which drags the filament during extrusion and retraction. Low-quality Bowden tubes can result in print imperfections from over or under-extrusion or clogging the printer nozzle.
If you’re printing with PLA, you may not have any problems with the stock Bowden tube.
But replacing the Bowden tube is recommended if you want to print more challenging filaments or upgrade your 3D printer.
Upgraded PTFE Tube
One of the most popular upgrades on FDM printers is upgrading to a Capricorn Bowden tube.
This tube is considered the gold standard of Bowden Tubes. Here’s why:
- It is lubricated: Capricorn tubes have a very accurate interior diameter producing a smooth interior surface finish allowing your filament to flow freely without getting snagged. Because of the smooth finish, many people refer to it as a lubricated tube.
- High-temperature resistance: Capricorn Bowden tubes are made from PTFE with a temperature resistance of 500°F. The high-quality tube allows you to print several filament materials without worrying about damage to your printer.
- High stiffness: The stiff tubbing allows you to cut the tube at a right angle without crimping the end. Not only is it better for performance, but it’s easier to install.
Replacing a Bowden Tube (Step-by-Step Installation Guide)
Below is a step-by-step guide to replacing a Bowden tube on a 3D printer. I
- Remove the old Bowden tube: Using a wrench, unscrew the hex nut on the top of the extruder and the hex nut on the print head.
- Heat the hot end to 210°C: We will need to partially remove the nozzle in the next step, but before that, it is essential to ensure that the hot end is warmed up to prevent damage to the threads. Heat the to between 200°C and 220°C.
- Loosen the nozzle: Loosen the nozzle between half a turn to one and a half turns. Loosening the print nozzle helps relieve any pressure in the print head, allowing for proper seating of the new Bowden tube.
- Cut the Bowden tube to size: Cut the tube to the desired length. You can use the old Bowden tube as a reference. Cut the tube at a 90° angle. Any other angle can create a clog. Tip: It is a good practice to cut it a few inches longer so that you can cut it back if needed. If you make a mistake, you can always cut it shorter, but you can’t make it longer.
- Install new fittings onto the ends of the tube: It is a good practice always to use new fittings. The jaws on the old fillings could be worn out or broken and will not seat properly to the new tube.
- Screw in the fitting on the extruder: Thread the new fitting to the extruder, tightening it snugly with the wrench.
- Install the fitting to the hot end: Feed the Bowden tube into the hot end until it cannot go in any further. Once it stops, move the fitting 1-2mm down the tube and seat it into the tube. Then begin threading the fitting into the hot end until it’s snug. Take care not to over-tighten the fitting because it can damage the threads.
- Tighten the nozzle: Tighten the nozzle back to its original position. Again don’t over-tighten, as this will damage the heat block.
- Level the Bed: It’s good practice to level the print bed after making modifications to your 3D printer. Changing the Bowden tube shouldn’t impact bed leveling, but checking the leveling before wasting filament on a failed print is better.
Now you have successfully swapped out your Bowden tube.
Over time you may notice that the tip in the hot end will begin to deteriorate (even the Capricorn Tube). To save money and extend the life of your Bowden tube, simply cut the tube back and reinstall it into the hot end.
A Bowden tube is a simple yet vital part of your FDM printer. It is responsible for delivering the filament string from the extruder motor to the Nozzle and significantly impacts retraction.
If not installed correctly, the Bowden tube can cause many headaches as it may be responsible for clogging, stringing, and other surface defects.