Wet Plastic Purge



  • Glue stick
  • Scraper


About the Wet Plastic Purge

The Wet Plastic Purge routine is designed to purge any plastic from your print head and extruder that may have absorbed water from the air. Some amount of absorption can happen over time because the extruder and Bowden tube are not a fully closed system. Plastic filament that sits in the extruder or print head for more than four hours can absorb water from the air and have a negative impact on your print. Therefore, the Wet Plastic Purge routine purges your Bowden tube of any potentially wet material to help ensure successful, high-quality prints.

The wet plastic purge line will automatically print at the beginning of every print job, unless it has already printed in the last four hours. Note: The purge line takes only five minutes to print and uses less than $1 worth of material.

In addition, if you are printing with nylon, you can use this routine to gain some insight into whether your nylon has absorbed moisture. Below, you can find some examples of what a well-formed purge line should look like and what would be expected of a purge line printed from wet material. Please note that this is not a useful utility for identifying wet Onyx; we suggest running the Onyx Pillars test print for that purpose.

Note: If necessary, you can enable or disable the automatic purge line print by selecting Menu > Settings > System Info on your touchscreen, selecting the gears icon at the bottom of the screen, and toggling the Wet Plastic Purge switch on or off. To avoid printing issues, we recommend that this routine be enabled at all times.

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Run the Wet Plastic Purge Utility

Note: The print head will become hot during this process. Exercise caution when working near the nozzles.

  1. Apply glue parallel to the far edge of your print bed as you would for a purge line on a normal print.
  2. Select the menu icon from the dashboard.

  3. Select the Utilities tile from the available options.

  4. Select the Test Prints tile from the available options.


  5. Select the Wet Plastic Purge Print tile.

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Diagnose Wet Nylon

When the purge line finishes printing, inspect it for rough spots. The rightmost end of the purge line should have about an inch-long section of rough finish; this is the section of nylon that was sitting in the nozzle. The next six inches of the purge line should have a smooth finish; this material was sitting in the Bowden tube. The remaining material should be rough again, then transition into a smooth finish; this is the section of nylon that was sitting in the extruder and the drybox. See the picture below for a visual representation of a well-formed purge line.

If your purge line appears to have more rough patches than described, consider running the utility again. Doing so will ensure that nearly all the nylon in the second purge line will come from the drybox. If the second purge line also has a rough finish, then the nylon in your drybox has likely been exposed to moisture.

The image below shows the purge lines from three different spools of nylon:

  • The topmost purge line was printed from a spool that was properly cared for and stored in a drybox
  • The middle purge line was from a spool that had been exposed to air for a short period of time
  • The bottommost purge line was from a spool that had been exposed to air for several hours

On each purge line, the rough patches are outlined in red. If your purge line resembles either of the bottom two examples, it may be time to replace your nylon spool.


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