New Build 1000x600x200mm (newbie)

[Jonathan]

yes machine is already setup to just do that, as I mentioned speed is fine, motor stalls If I increase acceleration to higher than .5m/s^2 range

If you take the belt off the Z-axis and give it a slight push, does it start moving down by itself due to gravity? If not then your ballscrew and or rails may not be aligned well.

To increase the acceleration capability the easiest way is to change the drive ratio. Make the pulley on the Z ballscrew larger, or the motor pulley smaller. The torque required for acceleration is proportional to the inertia reflected to the motor. This inertia scales with the drive ratio squared, so if you make the ballscrew pulley half the size, the motor will see about 1/4 of the inertia as before and the torque goes down by the same ratio. It's not quite as good as that as the larger diameter pulley will have a higher inertia, but you'll also reduce the torque required due to friction and lifting the axis (though that is already small).

Once you think the motor tuning is correct, I recommend running random g-code rapid moves for say half an hour, as that will stress the system to give confidence that the machine will not stall. I've made a spreadsheet here to do it:

http://www.mycncuk.com/threads/5843-...g-motor-tuning