by Zaggo, published

Z-Probe by Zaggo Sep 13, 2010

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This is a retractable Z-Probe.
With a Z-Probe your Makerbot is able to "auto home" not only X & Y but also the Z axis. This is done by mounting the endstop on your Makerbot in a way it senses the build platform directly (and nearby the real nozzle).
In order to get out of the way during printing, the sense-pin is retractable.

Although this is a working thing, especially the software changes are still beta. Both, firmware and ReplicatorG/host software, need to be updated. The extended versions are available as source code on GitHub.

For more information (and a sample video), see


The design is for use with a Futaba servo S148. That's the servo I found in my junk box. I guess each servo has a different size. So the design might be more a draft for your own design. I plan to try the same thing with a smaller (and cheaper) "micro servo" in the future. I hope I'll find the time to create a parametric OpenSCAD design until then.

Since it's still a prototype, the servo is currently glued to the base plate with some hot glue.

Both, the new extruder firmware as well as the extended ReplicatorG host software, are available on GitHub. I forked both projects from Makerbot:

G3Firmware: http://github.com/zaggo/G3Firmware
ReplicatorG: http://github.com/zaggo/ReplicatorG (ZProbe branch)

This is all still in a very early stage, both hardware and software.

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Combining this with coordinate-transformations like nophead did for hydraptor


could be awesome.

Move the bed around, do multiple meassurements and not only home the z-height

but also adjust for the bed not being perfectly level.

Few months ago I played with the idea in my mind how to home the z stage reliably and one was a electrical connection with the nozzle and the heated build platform. Both are metals so it should work but not with normal acrylic one. Sadly never got around to test that...

There are people using titanium and steel -belts for the ABP. So this will work too.

When Cupcake or RepRap is on continuous manufacture with ABP, I anticipated that the Z-axis jammed and stepped out. But good news first! :)

this is awesome. one of the biggest problems i have is not getting the z height perfect before each build thanks for making such great things and posting them here