The UP 3D Printer extruder has the following components

  • Stepper Motor: Used to drive the plastic material into the hot end.
  • Drive Gear: Bites into the plastic and pushes it down with some force into the hot end. 
  • Bearing and Cover: The bearing is to allow the filament to be passed through easily. 
  • Heat sink & fan: This keeps the top part of the silver column cool, to ensure the filament remains solid and rigid in order to push down onto the molten filament below. 
  • Silver Column: This is attached to the heat sink and guides the filament into the nozzle. 
  • Nozzle: Screwed into the Hot End / Extruder Block 
  • Heater Block/Hot End: Heated up to 270c and monitored by the temperature sensor. 

Theory of plastic extrusion 3D Printing
  1. The filament is pushed down by the drive gear, pushing the filament into the hot end. 
  2. Because the extruder gets very hot, the heat easily travels up the silver column and would soften the filament. However we don't want that to happen.  
  3. The fan blows cold air onto the heat sink, so the heat sink deflects the heat from the upper part of the silver column and the filament stays rigid.  
  4. The rigid filament pushes down on the molten filament and also creates a pressure or force on the molten filament, thus extruding it out of the tiny hole in the nozzle.  
  5. Without this pressure or force, you would not be able to print. You would be able to extrude as there is no model or platform in the way when you do this. e.g. The model or platform slightly blocks the nozzle during printing, thus a fair amount of force is required to extrude during printing and hence the filament is squished out flat onto the model or platform. 
The concept is like icing a cake, you need to put pressure on the bag to extrude out of a tiny hole. 

Air Printing Causes
The term air printing comes from when the printer is performing the action of printing but nothing is coming out of the nozzle. The biggest cause of air printing is NOT a blocked nozzle, but rather a build up of plastic dust around the drive gear.

Causes and Solutions

Dust around drive gear

Watch this video on how to clean the drive gear  

Parts warping

A warping print can create a blockage against the nozzle and will cause the flow of plastic to be blocked.

Platform to close to the nozzle

If the nozzle is scraping on the platform it's too close and will cause the flow of plastic to be blocked.

Broken piece of plastic in the silver column

Open the head up, as per above video and check for a broken piece

Carbon build up on inside walls of silver column

Remove nozzle, then use a 1-1.5mm drill bit with your hand and try and scrape out the walls of the silver column.

Carbon build up inside nozzle

Remove the nozzle and soak in acetone or burn with a flame.


Last updated on 3/03/2014 by Bruce