Note: If you have been running only PLA in your machine, use can PLA for the Atomic cleaning. If you have been running ABS, nylon, or another material with a higher melting point, please use this material for your Atomic cleaning instead, or use Ultimaker Cleaning Filament. The instructions below are given for PLA. If you’re using one of the higher melting point materials, the printer should be set to 260 for pushing material through, and 145 for the cold pull for the height temperature material. Particularly with filaments that tend to burn, you may want to use a 29 gage syringe through the bottom of the nozzle while hot, to puncture charred remains. Below are instructions for performing the cleaning method with the Ultimaker 2 series printer. If you have an Ultimaker 3 series printer, follow the instructions here.
1. Remove the filament from the printer, and then remove the Bowden tube from the print head by removing the blue retaining clip from the white collet on top of the print head. Then press down the collet, while pulling up on the Bowden tube.
2. Using the Maintenance->Advanced->Heat Nozzle menu on the printer, heat the nozzle to 250, and then looking down through the print head, guide a piece of filament through the print head, through the white teflon piece and into the nozzle. Alternate pressing and pumping the filament back and forth in the print head for a few seconds, and see if you are able to get it to extrude.
3. Then reduce the set temperature to about 85 degrees (assuming you are using PLA), and wait for the nozzle to cool. You can then pull up sharply on the filament, and it should pull straight out of the print head. If the filament breaks off near the print head, just repeat the heating and insertion process.
4. You should be able to pull the filament out with a good impression of the inside of the nozzle, and possibly even the 0.4mm nozzle exit. Look for any signs of dirt removed with the filament, or apparent obstructions inside the nozzle in the shape of the mold that you pull out. Repeat the process a few times until the plastic you pull out is clean and the shape doesn't suggest any debris is left inside the head.
The gold filament on the left is an example of a clean nozzle pull. The dents visible on the red filament on the right show obstructions still in the nozzle. The Atomic Method may have to be performed several times to get a clean pull. Charred bits of filament may come out when you’re pushing, or attach to the filament during the pull.
5. Reattach the Bowden tube, pushing it down through the collet, and making sure that it seats all the way down into the white teflon piece that is held in place with a spring in the lower part of the print head. The tube should go into the teflon piece by about 2 or 3 mm. Then, while pushing the tube down, carefully pull up on the collet, lifting it up around the tube, so it locks it in place. Replace the blue retaining clip. When you are are done, the Bowden tube should be fully seated into the white teflon piece above the nozzle, and shouldn't move as you tug gently on it.
6. After performing the Atomic Method, check your printhead and make sure that none of the printhead components unseated themselves during the cold pull portion of the cleaning. The white Teflon coupler and metal isolator are most at risk to being pulled out of place. Properly seated, the printhead should look like this.
If the isolator nut does become lifted away from the metal plate, unscrew the 4 screws holding the fan shroud onto the top metal plate, and gently tug at the nozzle until the isolator is seated flush against the plate again.