re: Timing Belts / slaving axes motors by series wiring?

Doug,

Use three pulleys and the belt only bends 180 in the "bend preferred"
direction. Put the motor pulley(cogged) in the middle and use 2
smooth pulleys on the backside of the belt to achieve a 180 wrap of
the motor pulley.

So the belt is fixed to the x axis rail(teeth down) and then goes
under the smooth pulley, around the driven (cogged)pulley, and under
the second smooth pulley, then to the other end of the travel to
where it is again fastened to the machine structure.

If the motor drives a "crosshaft" with cogged pulleys and belts on
both sides the "canting" problem disappears.

There are several commercial machines which use 2 motors to drive the
gantry. Precis, AXYZ, shopbot and Vytek come to mind. Although it
seems to work(using 2 stepper drivers and sending the same pulse
train to both), I prefer the single motor with crosshaft design. Be
sure the crosshaft is large enough diameter to avoid problems with
torque windup.

Hope this helps.

Ballendo

BTW, if you use a short piece of the belt (under the fastening
point), you can tighten the holding screws more without distorting
the belt.