Max V2 no more extrusion

[peterk]

Last week my Rostock Max V2 skipped the last 10mm of a long print for emergency purposes at my university.

Looks like extrusion just stopped at some point.

Extruder works fine. Tried a test extrude but only got a trickle of filament. Filament was curling up as if temp too low.

Took out nozzle to check for obstructions. Didn't see any. Cleaned it anyway. No luck.

Measured resistance of hot end temp sensor at the board. ~113k at room temperature. Seems about right.

Measured resistance of heater resistors at board (4.8ohms for the pair of 6.8ohm resistors in parallel). Seems about right.

Did the Kp Ki Kd calibration which came up with only slightly different values than were in EEPROM.

Ran temperature check with temperature probe in the tip from top where the filament comes in.
Readings:
Set to 200C -> read 190.5C
220 -> 207.2
230 -> 216.1
240 -> 222.6

That's about 5% lower than the requested temperature. Might be due to probe inaccuracy.

Heated hot end to 235C and tried to push filament through manually but couldn't. Nothing coming out.

Since the barrel is clear and heated to melting temperature I would think that the nozzle tip is obstructed. I don't have anything small enough to poke through.

Any ideas or suggestions most than welcome. I may well overlook something important.

Peter

[geneb]

When you measure the resistors, you need to disconnect them to make sure the RAMBo circuitry isn't part of the measurement. You should get 3.4 ohms.
If you have a stock hot end, there's two things that can cause what you're seeing.

First, you may have an inner liner that has shrunk. The inner liner is a short bit of bowden tube and it can shrink over time. The simplest way to test this is to remove the nozzle and see how easy it is to feed filament through the hot end by hand. You'll want to disconnect the bowden at the top of the hot end and just run a length of filament through by hand.

Second, the nozzle may have a hard blockage to it. This could be due to burnt filament or foreign debris. If you've got a butane torch, you can "torch out" the nozzle - basically burns out everything in it. You don't want to make the metal glow however.

You also have the option of simply replacing the nozzle if you don't want to mess with the torch. I'm pretty sure SeeMeCNC still has the old style nozzles in stock.

g.