Custom 3D Printer Print-Head

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Why build it?

Why not?  For my first home-built CNC Mill/3D Printer, I wanted to design and fabricate custom components as much as possible, including the 3D print head.  I naturally like knowing how  everything works and extruders were no exception.  I've worked with a few 3D printers and one of the things I found most interesting is how each one does the same thing with their own unique design.


The job of the print-head is to take a specific amount of plastic filament, heat it to a specific temperature, and deposit it directly on the build plate or previous layer.  It must be light enough so that the machine could easily move it but sturdy enough to handle rapid direction changes.  It also must maintain a specific temperature without letting too much temperature bleed off or other components soak it up.

The goal really is to get the plastic in a molten state right before it enters the nozzle - no sooner.  Otherwise the filament that comes before it will not be able to produce sufficient force to push the rest through the nozzle and it will become clogged.  

A nicer looking print is also achieved by returning the molten plastic to a solid form basically as soon as it leaves the nozzle.  This will prevent sagging of the part and maybe more importantly, provide a sturdy support for the layer that follow it.  This is important for smaller prints in which layers get added very quickly.

The Design

I researched into other extruder designs and saw what they all had in common.  Of course there's a little variety but the major components were:

  1. NEMA 17 stepper motor
  2. Toothed gear to drive filament
  3. Filament tensioner 
  4. Heat sink
  5. Cooling fan for heat sink
  6. Brass heating block and nozzle
  7. Part cooling fan (optional)
  8. Bed leveling sensor (also optional)

As long as all of those components are in place, plastic should print.  How hard could it be?  Items 7 and 8 were optional because not every print head needs them.  The part cooling fan was a separate fan that blew air directly on the part as it printed.  This is to prevent the part from sagging since just a second ago it was molten plastic.  The bed leveling sensor was so you don't need to go use that ole post it note to level your bed before you print.  

I wanted my extruder to be durable.  I ordered a few extruders from Amazon and my biggest gripe was that they were all so cheap feeling.  On one of them, the hole where you load the filament didn't even line up with the gear that is supposed to drive it.  So quality was an issue to.  I wanted something that could be easily used.  

Anyway, here is what I came up with.

Parts List


1.5"x3.5"x.75" Block (for body)

1.125"x1"x.75" Block (for BLTouch/Fan mount)

Extruder cooling fan


Donor Extruder (this will give you the heat sink cooling fan, NEMA 17, extruder gear, filament bearing, and nozzle for only 30 bucks!)

Miscellaneous hardware - see drawing for details

Final Thoughts

Well, it works!  Its rugged but not too heavy.  It mounts nicely to my machine and does a good job printing.  Best of all, I've never had a jam so the cooling must be pretty sufficient.  It is made of a solid block of aluminum after all.

Here is a time lapse of a bracket I printed for my motorcycle.  The video is a little disorienting so beware.  I'm working on my GoPro skills.