On Tue, May 30, 2017 at 10:05 PM, David Niklas doark@mail.com wrote:
Remember that as the weight and speed of the hot end increases the load on the z-axis motors and gears also increases (if temporarily), leading to (temporary), inaccuracies when using multi motor setups.
but you don't print at the time when z-axis motors are in motion: they're there purely to move the bed up (or down) for the next layer. thus the important thing to have for z-axes is precision and fine tolerances. fine tolerances can be achieved on lead screws with double nuts and a spring to prevent backlash.
ok so on to the next issue:
If I were to use multiple motors I'd not do it like this: M == motor H == Hot end
TOP SIDE M----M +-----+ | | |H | |H | -> | | M----M M-----M
But rather like this:
TOP SIDE +----+ M----+ | | H | | | -> | | M----+ M----+
Assuming I understand you rightly.
so you're advocating 3 lead screws instead of 4 i considered this as well, however i realised that if the printbed has even the slightest amount of twist it becomes impossible to correct that: you literally have to throw out whatever metal plate is being used and replace it.
if you have 4 lead screws, they may be used to place a twist on the plate to return it to dead-flat.
l.