Reprap Improvements – 3-point bed levelling

Nut rosette, printed in silver ABS. Not what I'd consider high-quality printing, but it'll do for now.

Nut rosette, printed in silver ABS. Not what I’d consider high-quality printing, but it’ll do for now.

As the proud owner of a RepRap 3D printer, I am very interested in making improvements to it.

One of the first modifications I have made is to re-kajigger the heated bed arrangement. I have oriented the PCB upside-down so that the heated traces are directly under the glass. I have also drilled another mounting hole in the center of one side: this way, I can mount the board to the Y-axis by three points, which greatly simplifies the process of making the bed level (something that happens quite often with an imprecise machine, particularly if you keep modifying it). To make it even easier, I created “rosettes” for the height adjustment nuts, which allow them to be easily turned without tools. I designed the parts in OpenSCAD as an exercise.

I have also made some custom macros and buttons for Pronterface, my current host software of choice. Basically, they are just buttons that call macros, and the macro simply says “Raise Z, move to corner, lower Z” so I can check the height. I am currently using a feeler gauge set to determine the actual height. The process looks like this:

Start with one of the two holes that are on a side. That is, NOT the hole drilled mid-way down the side of the heated build plate.

Lower the Z height to the first corner, so that the 0.10mm shim/feeler fits under the nozzle. Lower Z by 0.1mm increments until it is touching the feeler. Now you can either adjust the Z height manually by smaller increments, or adjust the bed height. To confirm your spacing, you can also try different shims like 0.12 or 0.15mm until you feel confidant about the amount of friction you get when the nozzle height above the bed ACTUALLY equals the shim thickness.


The grey ABS star is a “nut rosette” to allow the nut to be turned by hand, without tools.

Move to the second corner and adjust the bed height until it matches the first location. Move to the final location, the center/mid-way point hole, and repeat.

Once you are certain that your shim thickness represents the actual height of the nozzle above the board, you can set that with G92 Z0.1 (or whatever your chosen shim thickness is).

Oh, and here’s a link to the Thingiverse project if you’re interested in printing the same parts: Nut Rosettes. However, I would recommend downloading a copy of OpenSCAD and trying to design them yourself, because it’s a great learning experience. Or instead, you could choose a similar design made by someone with more experience. As with everything RepRap, the choice is up to you.

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One Response to Reprap Improvements – 3-point bed levelling

  1. Rog says:

    Well done, thanks for posting this 🙂

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