convex printer bed

I have a Prusa Mendel for a couple of years now and I still haven't succeeded in getting a really flat printer bed. (I am not spending too much time on this project anymore ). Now, instead of optimising the printer even further I though of measuring the z position with a pressure sensor attached to the extruder and scanning for the same pressure at different x/y positions, registering the corresponding z position.

With this I can then build a flat surface that I use to start printing... So far the idea...

Did anyone already implement something like this? Are there any software solutions out there for this or do I have to implement it myself?

Or is there a better solution ?

Thanks for any feedback

The problem may not be a concave bed at all, it may be that the X axis sags under the weight of the print head when the print head is near the middle.

Most if not all 3D printer firmwares support mesh-based bed compensation, which can compensate for both of these problems. You need a Z probe in order to use it.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].

Alternatively, you can lighten your print head perhaps. It seems an odd design that failed to take this into account. If the rail is truly sagging then the mesh leveling firmware will not perfectly solve the problem because it likely isn’t exactly repeatable. One test of your current bed flatness might be to get a borosilicate glass plate to put on your bed, that will likely be quite flat, see if that then gives you a good bed.

It is possible that the mesh leveling firmware will get you close enough. I use it on my delta printer to great effect.

DLC