Z printing backwards

I have converted a BFB 3000 printer to run on ramps 1.4. I use sprinter on the board and Pronterface and Slic3r as my slicer. I have the Z axis home to min (0). The platform moves head does not. So the platform moves to the bottom to home. When i start to print the xy home great and the z moves down hits the switch then goes to my desired z offset to be at the correct distance from the extruder. It prints the first layer then moves the bed up towards the nozzle instead of dropping like it should. in the g code it tells it to move up so it is not an axis invertion. Is there a configuration in slic3r That needs to be changed? this would work in a Mendel moving extruder style printer, not a fixed bed

The bottom is Z max not min. Think of the min as when the gap between the nozzle and bed is at its minimum.

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KesL , I also want to convert my BFB3000 to run on ramps 1.4. Can you help me?
Thank you

I am happy to help answer any questions you may have in converting your bfb3000. The printer was well worth the upgrade for many reasons. First, I can use the best software in my opinion for ease of use and speed which is cura by ultimaker. Second now i can use standard 1.75 mm fillament and have a finer nozzle for prints down to 50 microns with ease. I use ramps 1.4 running sprinter which is going to be upgraded to marlin to support the large lcd board i have for it. Second i use a mk8 extruder with an original high tork stepper motor from the original extruder from the bfb to replace the standard one you get which is still good. I laser cut some stainless steel plates to attach the new extruder as well as a laser cut plywood enclosure for the dell pc power supply which i might switch out to the original bfb one to save space. this was a very worthy printer for an upgrade as for it never worked as well as it could have.

Price:
Ramps 1.4 with arduino mega, stepstick drivers, lcd, and heated bed $90

Mk8 extruder $80

Endstops $15

Spool holder: printed

extruder mounting plates $0

old dell power supply free

Hi Kesel,

I'm very interested in your project and the way you have managed it.
I'm building (trying to) an UM2 like from a RepRap Ordbot Hadron (great printer but 2 Z motors a lot of vibration and not as compact and nice as the Ultimaker).
Could i see your modified firmware or wich one did you use as i have the same problem with my Z Axis. (And not sure how to tel that End Stop Mini is End Stop Maxi)
And also how to calibrate the Z.
I'm using a Arduino Mega With Ramp 1.4 and 4 line character screen (Unfortunatly not the full graphic one like the UM2).
I have a Bowden Extruder printed in PLA and a J-Head with some laser cut part to maintain it (i will install the original printing head soon).
I was using Cura with my Ordbot and I'm still using it even for upgrading the firmware.


If you can help that would be great.

Thank you

Jean-Luc

PS : Pictures of printer underconstruction