Neptune 4 TL4970 and Neptune 4 Pro TL4972 - removing blobs from hotend

Issue

You've returned to your unattended Neptune 4 or Neptune 4 Pro 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.

What causes this to happen

Most commonly it is due to incorrect Z-offset, lack of calibration, or poor build plate adhesion - the Z-offset height 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 it

See an overview of the disassembly process here. 

Remove the gantry cooling fans from the rear of the gantry using the 2.5mm tool.

Take the printer tool head off the gantry - leave the data cable attached.

(Neptune 4 has only 1x 2mm screw below the gantry)

Remove the side cooling fan assembly from the print head (2 Philips screws each side).

Turn the printer on and heat the nozzle to 210 degrees in Prepare->Temp.

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 the blob softens, 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, reattach the side fans, reinstall it to the gantry along with the gantry fans, test extrusion under Prepare->Extruder, and calibrate the Z-offset with a piece of paper under Levelling.

If you require a new hot end, an assembly complete with nozzle is available as Cat No. 001640. A video covering the replacement process 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 - do this in the Level menu.
• 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.