PTFE, or Polytetrafluoroethylene, is a synthetic polymer commonly used as a coating for non-stick pots and pans. It is the slipperiest substance known to man, and is said to be the only surface to which a gecko cannot stick. Although Bowden tubes can be made from several different polymers, PTFE is generally considered the best because of its high melting point and low coefficient of friction.

1.75mm Bowden tubing, because of its small diameter, is made with an expensive paste extrusion process. Very precise equipment is needed to obtain a consistent shape and internal diameter. Additives such as colorant are difficult, because the PTFE doesn’t readily want to mix with anything. Plain white PTFE is the cheapest and most common.

Capricorn tubing is manufactured using the most sophisticated equipment currently available. It always comes out perfectly round, and the diameter stays as consistent as possible.

Just like filaments, Bowden tubes vary in their real-world diameters. Tubing is often labeled as having an inside diameter of 2.0mm. The measured diameter may vary, however, anywhere from 1.75 to 2.15.

Capricorn XS Bowden Tubing is made from the highest quality pure virgin Japanese PTFE, and formed using the paste extrusion process. However, we have added a “Secret Sauce” which lowers the coefficient of friction. This additive also makes the tubing opaque.

XS tubing has a nominal internal diameter of 1.9mm, running from 1.85 to 1.95. This smaller diameter makes it ideal for printing flexible filaments, because there is no room for the filament to bind up inside the tube. The low friction coefficient allows any filament to glide through the tube with ease.

Important Note regarding interpretation of these specifications

Generally it is not safe to bring any PTFE above 260. The somewhat arbitrary melting temperature listed in this table is an indicator of stability of the material and is not indicative of a safe use temperature.

	Opaque White PTFE	Translucent White PTFE	TL Series Light Blue	XS Series Dark Blue
Additives	None	None	Blue Color	Blue Color and Secret High Performance Additive Mixture
Best For Chunky Filaments	No	No	Yes	Maybe
Best For Flexible Filaments	No	No	No	Yes
Can See Through	No	Yes	Yes	No
Pulling Friction^♠	1.0	0.9	0.8	0.8
Color	White	White, Translucent	Blue, Translucent	Dark Blue
Density (kg/m3)	2100-2200	2100-2200	2100 +/-100	2300 +/-100
Hardness	58-62	58-62	55	60-65
Inner Diameter (mm)	> 2.0	> 2.0	2.0 +/- 0.05	1.9 +/- 0.05
Linear Thermal Expansion at 250 °C	3.4-3.6%	3.4-3.6%	3.4-3.6%	2.2-3.3%
Material	Cheapest PTFE	Better PTFE	Highest Quality Pure Virgin PTFE	Highest Quality Pure Virgin PTFE
Melting Point (°C)^♥	as low as 220	around 260-327	around 340	around 340
Outer Diameter	about 4 mm	about 4 mm	4.075 +/- 0.025	3.995 +/-0.025
Roundness (ϵ)	Variable	Variable	< 0.1	< 0.1
Stiffness	High	High	Medium	Medium High
Thermal Conductivity (W/m-k)	0.25	0.25	0.25	0.25
Wear Rate (gm/s)	0.01	0.01	0.01	0.01
Young’s Modulus (GPa)	<0.50	<0.50	0.50	0.532

^♠Pulling Friction is calculated as the average force required to pull 1.2 meters of 1.75mm PLA filament through 1 meter of tubing at a constant speed, relative to 1 meter of cheap white reference tubing. Note that although we observed the friction of the TL series to be about the same or even slightly lower than our XS series, it also has a larger internal diameter.

^♥PTFE does not transition quickly from a solid to liquid, but acts as a glass, slowly softening. Temperatures were approximated by heating samples of all tubing simultaneously, observing how quickly each one began to deform.

Full specsheet: Here.

Capricorn XS Reduced Friction Bowden Tubing 1.75mm

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