Unblocking Nozzles: The Atomic Method aka. The Cold Pull

Blocked nozzles are an annoying but common issue with 3D printing and can result in under extrusion or messy prints. The Atomic Method, also called Cold Pull, should always be your first step when tackling this issue. Here’s a compact guide on how it works!

  1. Remove the filament from the printer. To do so, simply pull the filament back out through the feeder.
  2. Remove the Bowden tube. To do so, remove the little horseshoe clip around the coupling that connects the tube to the printing core. Then simultaneously hold down the coupling while pulling out the Bowden tube.
  3. Turn up the temperature to 220°C for PLA or even to 250°C – 260°C if you have printed with other materials (Settings > Printing Core 1 or 2 > Temperature)
  4. While the nozzle heats up, cut off a 20-30cm long piece of filament (e.g. from a leftover filament roll) and straighten it out as much as possible (using either your hands or pliers).
  5. When the temperature has reached its high, insert the straightened piece of filament and push through the printing core until you see filament coming out of the hot end. Depending on how clogged your nozzle is, you may have to apply some force here. (If no filament comes out at all, no matter how hard you push, your nozzle is probably too badly clogged to be cleaned using the atomic method. Have a look at this post instead.)
  6. While the filament piece is still inside the printing core, lower the temperature to 90°C and wait until the printer has reached this temperature.
  7. With a sharp yank upwards, pull the filament piece out of the printing core. If you notice some debris stuck on the filament piece, repeat steps 3 – 7 until it comes out clean. Now your nozzle should be ready to go!

Unblocking an Ultimaker 2 Nozzle - Atomic Method

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