What would cause this on the Rep 2 Extruder?

[Bryon Miller]

I can't get my extruder to work properly.  It just started to fail earlier today.  The plate is leveled properly and i have cleared the clogs.

I clear out the extruder so I can see the light from a flashlight shine up through it like these pictures show.

The extruder is cleared so I can see the detail inside the barrier tube, you can see the light shinning through in the pictures.  The picture of the tardis I was attempting to print shows what it looks like when the extruder starts to clog, The last picture shows the noodle coming out at an angle during a filament load after the print failure.  When I first cleared the extruder and loaded it, the plastic came out straight like it is supposed to.  I dip my filament into a little canola oil before I load it.  The plate is properly leveled.  I have tried several different filaments with the same results every time.  I've been using this printer for the last two years every day so I'm pretty familiar with how to clear the clogs and level it.  It has thousands of hours on it so I'm sure something is prone to failure because it is being used so often.  Both fans are working, the active fan didn't turn on before the failure in the picture shown because it didn't even get the first layer down yet.  The temperature on the bot reads consistently but I have no idea if there is an actual problem with the heat because I don't have anything to actually measure the heat, I have no idea if this is something that might be happening because of heat.

Does anyone know why it would constantly fail with clogs after being cleared as shown above every time?  I'm not sure what else to try now...

[Ryan Carlyle]

Did you replace the nozzle, or reassemble with the old one?

[Bryon Miller]

No, I've never removed the nozzle itself.  The whole thing looks so basic, I don't understand why it does this if I can see straight through the hole.  I'm having to use a flashforge dreamer right now and I really don't like it in comparison to this machine.

[Ryan Carlyle]

It's not basic because extruders are viscosity pumps, and getting super-precise volume control out of a viscosity pump is hard. Think about this: why doesn't molten filament squeeze out the top of the thermal barrier tube (through the annular gap between the filament and tube), instead of squeezing out the tiny nozzle orifice? The melt pool has a few thousand psi of pressure in it when the stepper clicks. That pressure should be pushing all sorts of molten filament up the thermal barrier. The only thing preventing that is viscous shear created by the filament moving downward. 

Frankly, it's a miracle they don't jam more often than they do.

You may have some junk inside your nozzle, or stuck at the interface between the nozzle and thermal barrier tube. Pop off the nozzle and see how it looks. Then replace the nozzle to see if that helps. They're cheap.

[Bryon Miller]

Wow.  I'm just a simpleton that bought a 3d printer I happen to love and use every day.  I didn't know it was that involved.  I believe you were right about junk stuck in the nozzle/barrier tube.  I worked at it again, this time the light shinning through the hole was so bright it gave me temporary retina burn.  Once my vision was back, I put it back together and it seems to be working great now.  Do nozzles have "milage"?  Should they be replaced after so many hours?  I still have the original nozzle and this machine is in constant use.

[John B]

It depends on the filament that you are using. I was printing last Christmas with some glow in the dark type filament, it is so gritty after 1 roll the nozzle was shot!

 Don't buy a Makerbot nozzle  there are many better ones on the market at 1/2 the price.

These are $5 a piece    http://store.quintessentialuniversalbuildingdevice.com/product.php?id_product=38 

These are $14 a piece and work well  http://www.p3-d.com/low-friction-mk8-extruder-nozzles.html

Hope this helps

[TobyCWood]

How well does the extruder grip the filament between the stepper's hobbed gear and the bearing?... you pinch it while it is loading and you should be able to make it stutter. The spring can weaken over time or the arm it self (assuming it is plastic) can deform,

The other possibility is your nozzle may not be as clear as you think. Your filament flow is not directly downward. Over time the stuff builds up along the walls of the nozzle... towards the tip where you are actually beyond the melt zone... EVERY bot I have ALWAYS eventually needs to have this removed... cleaned out... I swap out the nozzles then eventually clean them with a blue flame torch, but many do not like to do that... It works for me.