Maintaining the BB print core

To keep the BB print core in optimal condition it is necessary to clean it occassionally. If there is no material flowing from the print core for at least 10 minutes it could suggest that there is some burnt PVA material in the nozzle, leading to a nozzle clog. In this case, the BB print core should be cleaned by doing several hot pulls and a cold pull with PLA material, as described below.

Note: Make sure there is no material in the print core when you start this procedure.


  1. Go to Material/PrintCore > PrintCore 2 (BB print core) > Set temperature and set the temperature to 230 °C.
  2. Remove the clamp clip from the top of the print head.
  3. Loosen the bowden tube by pressing on the tube coupling collet and pulling the bowden tube out while doing this.
  4. Place the print head in the front right corner to avoid bending of the XY axles when applying pressure to the material during a hot pull or cold pull.


Hot pull

  1. Cut off approximately 30 cm of PLA with a straight cut and try to straighten the material as much as possible.
  2. When the nozzle reaches the target temperature of 230 °C gently insert the piece of PLA into the print head until you feel some resistance.
  3. Hold the piece of PLA with pliers and gently apply pressure to the material for ±2 seconds so that it extrudes from the nozzle.

    Caution: The use of pliers is required to prevent injuries on your hands in case the material breaks.

    Note: Applying too much pressure to the material is almost impossible, the Ultimaker 3 will not get damaged. If there is no extrusion, apply more pressure.

  4. Pull the material out with a quick, firm pull once the 2 seconds have passed.


  5. Check the color and the shape of the tip of the material that you have pulled out. Compare it with the pictures below to see if it looks as clean as the picture on the right.


  6. Repeat this hot pull process at least once and until the tip of the material is completely clean. This could mean that you have to do the hot pulls more often. After completing the hot pull process, manually flush some material through the print core with pliers and take it out again.

Cold pull

  1. Take a new piece of PLA and insert it into the print head by hand until you feel some resistance.
  2. Hold the piece of PLA with pliers and gently apply pressure to extrude some material.
  3. Lower the temperature of the print core to 75 °C. Keep pressure on the material with the pliers until the print core reaches a temperature of 120 °C.

    Note: The slight pressure on the material while cooling down is required to prevent air from entering the nozzle.

  4. Wait until the target temperature of 75 °C is reached.
  5. Grab the material with pliers and pull it out with a quick, firm pull. The material should now look like this.



  1. Insert the bowden tube into the print head.
  2. Re-attach the clamp clip and keep pressure on the bowden tube while doing this.