Nozzle Blockage ~ Or is it?

At some point in time you may experience a failed 3D print scenario, the “Air” print as some like to call it.

Just when it seems that your print is going well and you will soon have your amazing 3D printed model in your hands, the filament stops extruding from your nozzle, or another scenario is that you have arrived to remove your 3D printed model from the printer bed and all is not as it should be.

The print has completed but the printed object feels sort of spongy, like intermittent layers are missing, or the filament hasn’t extruded properly whilst printing.

We don’t know about you but when we first started on our 3D printing journey and this happened, we immediately thought that it was a nozzle blockage.  So off came the nozzle and we checked to see if is was blocked, but no, all was fine.  We would hand push through some filament and it extruded beautifully out of the clear nozzle.  We would then run another print only to find that after a short while the print would show signs of failing again.

Ok, so it must be a hotend intermittent temperature issue, or a filament diameter problem.  Though having ensured neither of these were at fault, we were then at a loss to what it could be and that it must be something more technical and we would now have to strip down the printer, re-flash the firmware, recalculate the e-steps take the 3D printer back to default etc..you know, the extreme measures!

It is only when we came to strip the hot end right down that we came across the tip of the Bowden tube, i.e the PTFE tube that runs into the hotend/nozzle.  Now some 3D printers you may look at and think the tube wouldn’t really matter when it comes to the filament extruding and all the “work” is done at the nozzle end.  That is when we became enlightened through poking around the hot end setup on our machines as to the significance of the “tube”.  A selection of some of our own “tubes”….

As you can see there are many different PTFE setups, Bowden and Direct Drive, some are easier to access than others.

What we found when the white/blue PTFE tube was removed from the hotend, because of a failing print, the end of the tube would invariably look like this…

When the end of the tube should actually be clear and debris free, or at least like this.

Too much debris building up at the end of the PTFE tube can reduce the diameter inside of the tube and create friction against the filament being pulled/pushed through, causing an intermittent flow rate.

Now because the end of the tube is hidden within most hotends you do not immediately think this would be causing your flow problems.  Well guess what, this is now one of the three things we always look at first, when we have an extrusion flow problem.  Now all you need to do is just take a sharp blade and slice off a slither at the end of the tube and voila you are good to go!

We have found Wood like and carbon infused filaments have a tendency to degrade the end of the tube, or at least gunk it up.  So as part of your regular machine maintenance you may want to clean out your “tubes” once in a while, before the intermittent failed 3D prints make you want to scratch you head.

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