PSA - Check your PTFE tube length!  

RE: PSA - Check your PTFE tube length!

Length is important, but also you need to chamfer the PTFE tubing.  

PTFE Chamfer tool

RE: PSA - Check your PTFE tube length!

I designed this chamfer tool: https://www.prusaprinters.org/prints/34035-ptfe-multitool

This allows you to cut to length and apply exact 60 degree inside chamfers and 90/120 degree outside chamfers. I'm using it all the time for my printer/mmu2 and never had problems with loading/unloading filament due to sharp PTFE edges.

RE: PSA - Check your PTFE tube length!

@karl-herbert

I will give it a try.  

RE: PSA - Check your PTFE tube length!

https://www.thingiverse.com/thing:3121653

RE: PSA - Check your PTFE tube length!

I was having loads of problems after a couple of days of putting the kit together,Clicking,Not flowing  properly,Thankfully i found this thread and checked the length of the tube,It was 1.4mm too short!!  

I have no spare so they are posting some out to me.

After reseating everything on the old tube it's printing again but i am waiting for it to fail,I send the link to this forum post to the tech guy @ prusa,They said they didn't know about it...

This thread should be pinned!

This is pretty poor show,I was really impressed how the kit went together but was thwarted by the only bit i didn't build myself,Very annoying.

RE: PSA - Check your PTFE tube length!

Both of my tubes were the same length - 42.5mm.

RE: PSA - Check your PTFE tube length!

In my case both tubes were to short. The installed one hat something like 42.8 mm (after about 2 hours of use), the spare had 43 mm. But however: I figured out that the exact lenght does not matter. The important part is that the tube has to be constrained between heatbreak and bowden fitting. So I helped myself out with pushing the heatbreak a bit (-> abut 0.5 mm) more upwards and thats it. Since then I had no issues on the hotend side. (The extruder is another story..)

RE: PSA - Check your PTFE tube length!

Interesting, I've been having problems with under extrusion, and have practically taken my entire MINI apart more than once to try and fix it to no avail.  Quick question though, if a PTFE tube gets shorter or damaged in any way, how would this cause the huge decrease in extrusion?

.

When printer is retracting it pushes PTFE around.

Gap appears winch slows filament down, instead of going straight to the nozzle, its semi-melted inside heatbreak.

Maintenance Item

As described before, I also now just consider this a maintenance item and replace it when things are not printing correctly. Note that if it is stuck in the hot end and you pull it out with anything like tweezers or pliers, it is deformed on the top and should be discarded anyway. I just ordered a few from Prusa to use in the future. They are not expensive if bought along with other things to include the shipping cost.

Regards,

Mark

RE: PTFE tubes

When you place an order, I would just order a handful.  I have 8 Mk3 variants and 4 MK3S.  I order 10 annually of each type.  I do recommend you label the bags when you get them.  Labelling is invaluable if you have multiple printer types.  I have 2 Mk3S with Bondtech and Mosquitos, 1 Mk3S with a Dragon, 5 Mk3/Mk3S with V6, 2 Minis with standard hotends, 2 Minis with V6, and a Mini with a dragon.  It can become a nightmare to know what is each baggie if they are not labeled.  I guess you could just use a set of calipers and measure them.  

RE: PSA - Check your PTFE tube length!

Posted by: @talos

I'm hearing more and more reports of people getting their mini with the installed PTFE tube being too short by a millimeter or more (myself included).  This can eventually lead to the dreaded underextrusion issue.  The spare PTFE tube is often the right size.  The tube should be 43.4mm +- 0.1mm.

Thank you so much for your PSA. This fixed and saved my Mini+!