After building a number of Prusa and MendelMax 3d printers, we recently decided to make a Rostock delta robot printer. While the Rostock design is quite cool, we were experiencing what appeared to be a weird firmware bug with the machine.
The Rostock would home correctly, with top+bottom or top only endstops, but as soon as it finished homing the print head would shoot for the right-rear corner of the print platform. This behavior occurred no matter what object we were trying to print. After letting the print continue despite the initial jump, we finally noticed the machine was actually trying to print the file in the wrong location.
It turns out that the Marlin firmware for the Rostock was setup to use 0, 0 as the center point of the build platform. While this makes perfect sense, it produces the above behavior when Gcode is created using the 100, 100 build platform center used by standard RepRap machines. Simply change the center point to 0, 0 in Slic3r, or your slicing programing of choice, and it should work correctly.
One More Thing…
While updating the center point will allow the Rostock machine to print correctly, the print preview in Pronterface now shows the file being printed in the lower left corner with most of the design off the screen. To fix this, we need to open Settings -> Options in Pronterface. Then update the build_dimensions from “220x220x100+0+0+0” to “220x220x180-110-110+0” (without the quotes) and restart Pronterface.
It is now printing like a charm.