Preventing Clogs with Your Ubis 13S Hot End

If you're having trouble with clogging in the 13S, this will solve it.



There are a few reasons for a clog in the hot end; an old nozzle full of char, out of spec filament, dirty/dusty filament.  One cause that is specific to a metal hot end (Ubis 13S or Ubis 13), rather than a ceramic, is too much heat in the heat sink.  Filament needs to stay solid ...until it doesn't.  That is to say, for filament to extrude properly, it has to remain cool and hard as it travels down between the drive gear and pulley, into the top of the hot end, and on into the melting zone.  Molten filament can only be pushed out of the hot end if there is solid filament behind (above) it to force it down the line.  So, you can see why semi-melted filament could be a problem.  If heat from the heater core creeps up into the heat sink, extrusion can be a lot like pushing rope.


With this in mind, it becomes apparent that one needs to keep the heat sink cool while the heater core is hot.  Follow these steps to keep your Ubis 13S hot end cool.


Simple/Plus users, add a fan to your hot end.  

Add a fan to your Ubis 13S heat sink or simply place a small personal fan on your desk to keep airflow around the heat sink. 

Click here for instructions on adding a 30mm fan to your Ubis 13S Hot End.



All Ubis 13S users: If your bot's ON, you should be cooling that heat sink.

As soon as you power ON and connect via USB, open the Pronterface UI in Cura (P for Mac) and enter the command "M106" to turn your fan on.  It's easy to get distracted in the middle of getting a print started.  So, go ahead and get that fan going first thing.

It almost goes without saying, the best thing to do is to load the model and get to printing right away.  It is not recommended to just let your hot end (metal or ceramic) sit at temp without printing for an extended length of time.



See below additional tips for printing jam-free.


  • Review the Ubis 13S User Manual
  • Use our filament. While Printrbot is non-proprietary when it comes to filament, we have printed many hours with our PLA and exotics and can only recommend using filament from
  • Recommended temps should be the lowest possible that still prints well. 210C max for PLA, we have had good results printing at 190C
  • Recommended print speed is 40mm: This is for PLA as well as most filaments found on our store, exceptions include flex, ABS, PETG and Nylon
  • Extruder spring tension should be the lowest needed for the filament to be pulled in, but not so loose as for the filament to slip. We have had good results with the M3 nut from 4 to 6 mm from the bottom of the extruder base.
  • Check drive gear alignment by looking down into the top of the extruder, the hole that the filament goes in should be matched with the gear's teeth and the curve of the drive gear.
  • If you are printing with certain exotic filaments such as carbon fiber, the abrasion from the filament will wear out the hot end leading to jams in the hot end tip.
  • Change the tip of the hot end: The tip may have a buildup of charred filament and will need to be replaced.
  • Make sure that your hot end is tightened at the heat break and heater cartridge
  • If you do have a jam, please go through our guide on how to do a cold pull.
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