Centauri Carbon TL4980 - removing blobs from hotend

Issue

You've returned to your unattended Centauri Carbon 3D printer to find that it appears to have leaked filament from the nozzle and made a filament blob engulfing the hot end. 

This is known as a "Blob of death" and is something that you need to fix yourself - it is not a warrantable fault with your printer. It can be avoided if you check on your prints every so often and catch it early.

Cause

Most commonly it is due to incorrect Z-offset, lack of calibration, or poor build plate adhesion - the Z-axis offset was not calibrated correctly or the build plate is worn-out, or dirty and not sticky enough, causing the filament to fail to stick the first layer down properly. The result is that the print can lift off the plate at any time - it can then stick to the hot end, and if left unattended, forms a big blob that sticks to the hot end. A worn or blocked nozzle can also cause the filament to bend back as it extrudes and stick to the nozzle.

How to fix

Send the heated bed platform to the lowest position (On the Display: Prepare -> 30mm -> Z down).

Remove the cooling fan from the print head and unplug the cable.

Remove the bolts that hold the hot end to the print head with a 2.5mm hex tool.

Manually pre-heat the nozzle to 220 degrees.

Leave it for a while to see if that loosens the blob up a bit (Key word here is "Soften" - not "Molten"). Higher temp filaments like ABS and PETG will need a higher manual temp setting. 

Don't touch the metal parts with your fingers, as they will be very hot. Once you soften the blob, grip the metal part with a small clamp or an adjustable wrench, and use tools like needle-nose bent pliers to gently work at the blob to pry it away from the nozzle and hot end so as not to damage the wires of the heater and thermostat. Paper towel can clean up the residue. 

Once clean, turn the printer off, let the hot end cool, reinstall it, attach the cooling fan, test extrusion, & do Automatic Levelling. If the is fan unplugged, the display will show "error 703: Abnormal Model Fan".

If you require a new hot end, it is available as 001776. A hot end complete with nozzle is available as 001777. The full replacement walk-through is here.

Prevention

To avoid this happening, it is good practice to do the following in order:

• Clean the print surface before starting your prints.
• Use a gluestick or spray contact glue on your build plate to promote proper adhesion.
• Calibrate the Z-offset - this option should appear in the slicer at the last step of the print dialog.
• Watch your print and make sure that the first layer is sticking properly to the entire print surface.
• Check on the print occasionally - do not leave printers working unattended for hours at a time.