Z axis doesn't move during print?

Ok I have built a printer similar to an Ord bot, but on a much larger scale. I have the mega and ramps 1.4 and gadgets3d LCD . I can move all axis manual in pronterface and with LCD. But when I try to print x and y move fine but z doesn't move up during print. I have checked g code and it has z movements. Any suggestions would be greatly appreciated !

you could try reducing the max speed of your z motor, either in your slicer program or firmware.

if the speed is far too high you'll just hear a quick 'beep' from your motor instead of it moving, because it can't step that quickly