If the GBX is underextruding and you suspect something may be stuck in the extrusion screw, one option is removing the extrusion screw. However, removing the extrusion screw should be a last resort after all other methods have been tried, including:
- Adjusting printing temperatures
- Adjusting extrusion settings
- Confirming material flow into the extruder block
- Flushing out the extrusion screw with a purge material
- The purge material will depend on what material was previously in the extruder. You can use a purge material formulated for the temperature range and material type of what you had been printing with.
- Dyna-Purge F2 is a purge material with a large operating temperature range, which is great for GBX since it works with a lot of different materials.
- ASA Clean's glass fiber purge material is another option to scrub out carbonized contaminants and degraded material from the extruder screw.
- Removing and inspecting the nozzle for clogs
To remove the extrusion screw, these are the basic steps at a high level:
- Disconnect the feed system from the extruder to stop material flow into the extruder
- Purge as much material out of the extruder as possible
- Remove the components at the top of the extruder to access the extrusion screw
- Remove the nozzle and nozzle adapter at the bottom of the extruder
- With the printer heated, push the screw down and out through the bottom of the extruder
Removing the Extrusion Screw
- Disconnect the feed throat from the extruder by removed the 4 M5 mounting screws that connect it to the extruder block. Use a bucket to catch any material that flows out of the feed system.
- Heat up the extruders (either via the Viki or USB) to the printing temperatures of the last material loaded into the extrusion screw. Warning: Do not attempt to remove the extrusion screw without first heating it to melt any solidified plastic.
- Purge as much material as possible from the extruder using one of the following three methods:
- Connect to the printer over USB and extrude through Simplify3D’s Machine Control Panel
- On the Viki, purge using "Prepare">"Move Axis"
- On the Viki, purge using "Prepare">"Purge"
- Turn off the printer and unplug the extruder motor. Warning: Always switch off the GBX before connecting or disconnecting any electrical components.
- Remove the Extruder Cover Cap by removing the 2 M3 screws at the front and 1 M3 screw at the back of the extruder cover cap.
- With an 8mm wrench, loosen the 4 screws that hold the motor spacer to the thrust bearing plate beneath it. Once loose, the entire motor assembly, including the motor, motor spacer, and top shaft collar of the shaft coupler assembly can be lifted away. A photo depicting this step is shown below:
- Remove the black Motor Coupler Insert from the motor coupler assembly at the top of the extruder screw shaft.
- Use a 3mm allen wrench to loosen the set screw on the lower shaft collar of the shaft coupler assembly. Once loose, remove the shaft collar from the extruder screw shaft.
- Turn the printer back on and heat the heat zones to the temperatures of the last material printed.
- Once the extruder has reached the set temperatures, use a 5/8" wrench to remove the nozzle adapter from the bottom of the extruder barrel. It may be necessary to use a vice grip at the top of the extruder barrel to provide leverage.
- Lower the bed to at least 200mm below the home position. Place some cardboard or sacrificial material on the bed to protect it in case the screw drops.
- Put on a welding glove to help catch the screw.
- With the extruder still heated, firmly push down on the screw from the top until it drops out of the bottom of the extruder.
Cleaning the Screw
The screw can be cleaned using a brass brush in combination with a heat gun.
Reinstalling the Extrusion Screw
Follow the same steps for removing the extrusion screw, but in reverse. This means inserting the screw through the bottom of the extruder barrel.