UM Original Bowden tube inner diameter?

[foehnsturm 969]

Until today I assumed the inner diameter of the bowden tube delivered by Ultimaker to be 0.125". After some issues with optimum retraction settings I took a close look. Mine is 1/4" (6.3mm) OD but 4.0 mm ID (I know this size is produced as well).

As I'm not fighting retraction length (easy to increase) but retraction lag (small bumps which are produced when the nozzle sits still and waits for retraction to start) this might be the reason.

Did Ultimaker occasionally sell 1/4" - 4.0 mm tubes?

[SandervG 1,521]

If I am not mistaken the ID of the bowden tube should be 3.16mm

We have had some experiments with larger ID but we found the 'normal' works better.

I do not think they were ever sold with larger ID.

 

[foehnsturm 969]

Hi Sander,

Thank you for your instant reply.

As I never managed to find a source for imperial sized PFA tubes here in Europe I'm quite sure it's the one supplied by Ultimaker. Don't get me wrong, I've been very happy with overall print quality. But never got rid of considerable stringing with PLA/PHA so started to investigate.

My understanding is that 4.0 ID mm gives about 1.8 mm bowden lag ((4-2.85) * Pi /2 ) vs 1/8" gives about 0.5 mm. This defines the timespan until the filament actually starts to retract at the print head and the nozzle happily oozes.

 

 

[jonnybischof 60]

Got two bowden tubes laying around atm:

One which was purchased in August 2013, and one just recently.

They both have about 3.2mm ID (somewhere between 3.15 and 3.3, it's very flexible material...)

Note that one end of the bowden tube is widened slightly (actually, to about 4mm ID) to make a better fitting for the entering filament. That's why the tube is marked with blue tape...

But that's only for a few millimeters, the rest of the tube has the 3.16mm nominal ID Sander described. You can see that if you look closely.

 

[foehnsturm 969]

@ JohnnyBischof,

Very good advice! I measured the other end: approx 3.3 mm ID . Apologies for my hasty conclusion Sander!

So I will mount the original tube to my new printhead and see if retraction improves.