Automatic bed level issues

I've just finished my Kossel Mini and build it exactly the same as Johann Rocholl's one. It works out of the box and manages to make a decent print. Sizing is a bit off on the first prints (height is spot on but xy is to small). But the main issue is the bed leveling. It goes through it's paces but it appears to not do anything with the data. Here's a picture of a fairly large outline:


As you can see it's perfect in the center, lifts at the front and burries in the tape at the back. You can also see it dips again in the frontright corner.
Do you have any idea what this can be? I've attached my config.h as well.

It is a long time from when I looked at Johann's code and I do not have Kossel. But IIRC, the bed leveling data are always applied (you cannot disable this), and the bed leveling data are not stored in EEPROM, so you must level (G23) before each print.
Also bed leveling will not really help you if your printer geometry is too different (lets say more than 2 mm ... I do not know just a guess) from the actual geometry of your printer.

I'm fairly imbarresed right now. I switched marlin branches and Johann changed one of the geometry settings from 145 to 139 and i didn't see it.
So changed it back and now it prints perfect flat. I'm impressed.

What was the geometry setting you had to adjust? I'm having a similar problem with my mini kossel. The level is perfect for negative X and Y values. But positive values are way too low on Z. Some insight would be really appreciated

The geometry setting that needs to be adjusted is DELTA_SMOOTH_ROD_OFFSET in Configuration.h. Depending on which branch of Marlin you are using these values may be different. Originally the value in the branch I had, was set to 137, and I was having a similar problem to Vinculum. I changed that value to 145 and everything started working very nicely.

The differences seem to be in which branch is for Kossel Mini. Here is the Kossel branch of Marlin: [github.com]
located on Johann's github. This branch has the correct DELTA_SMOOTH_ROD_OFFSET value and appears to be for Kossel Mini. If you checkout the main Marlin branch on Johann's github make sure to make changes for Kossel Mini.

Tearabite I hope you figured this out, but I was having a similar problem recently as I just finished my build and wanted to save others some time.

Happy Printing