HOW TO DO A COLD PULL (ATOMIC PULL)

Cold pulls clear partial nozzle clogs - carbonised filament, dust, and switching residue inside the nozzle bore. The technique exploits a property of plastic: at certain temperatures it's stiff enough to grab debris but soft enough to deform around it. Pull at exactly the right temperature and the filament tip comes out shaped like the nozzle interior with all the debris stuck to it. It's the cheapest, fastest first-step for any clog or partial-clog symptom. Takes 2 minutes, costs zero, often fixes the problem entirely. Always try cold pulls before disassembling the hotend or replacing the nozzle.

Use cold pull when: extruder is clicking or grinding, extrusion is thin or inconsistent, prints are starting fine then degrading after a few layers, you've just switched filaments and the new one isn't extruding cleanly, or as preventative maintenance every ~200 print hours. Don't use cold pull when: the nozzle is fully blocked (no extrusion at all even when manually pushing). At that point the clog is in the wrong physical location for cold pull to reach - you need to disassemble or replace.

1. Disable the part cooling fan so heat stays in the hotend. 2. Heat hotend to print temp for the filament currently loaded: - PLA: 200-210C. - PETG: 230-240C. - ABS: 240-250C. 3. Manually push filament through the nozzle until clean plastic is extruding consistently. Use the LCD's 'Move E' or extrude function. 4. Drop temperature. - For PLA-loaded nozzle: drop to 90C. - For PETG / ABS / TPU: drop to 100C. - Wait until the displayed temperature settles at the target. 5. At target temperature, pull the filament out firmly in one continuous motion. Hold the filament with pliers if it's hard to grip; pull straight up, not at an angle. The pull should feel like firm resistance giving way - if it feels stuck, push down 1 mm to break the seal then pull. 6. Inspect the tip. Should be shaped like the inside of the nozzle - a small cone with a fine point. Debris (carbonised black flecks, colour from previous filament, dust) should be visible on or just behind the cone. 7. Cut the dirty tip off and repeat. Reload, push fresh filament until it extrudes, drop temp, pull. Repeat 3-5 times until the pulled tip comes out clean (white or transparent for PLA, no visible debris). 8. Re-enable the part cooling fan and resume printing.

Pulling at the wrong temperature. Too hot (above 100C) and the filament stretches without grabbing debris - comes out as a thin string, no cone shape. Too cold (below 80C) and it snaps off inside the nozzle. Pulling at an angle. Bends the filament inside the heat break - can cause future jams. Always pull straight up. Stopping after one pull. A nozzle dirty enough to be clogged usually needs 3-5 pulls before the tip comes out clean. Cold pull with no manual extrusion first. You need to push fresh plastic into the nozzle so it has something to grab debris with. Skip this and pulls come out empty. Cold pull with the part fan running. Cools the hotend unevenly. Disable the part fan during the pull procedure. Using nylon for cold pull. Some old guides recommend nylon for cold pulls - works but unnecessary. Whatever filament you're already running pulls fine at the right temperature.

If cold pulls don't fully clear the clog, try a needle clear (0.4 mm acupuncture needle from below). For full clogs that won't budge, replace the nozzle - see how-to-change-nozzle. For diagnosing whether you have a clog vs heat creep, see how-to-diagnose-clog.