Here's what I hear you descibing - you wnat to build a foam cutter with vertically mounted parallel X-Y stages at each end, and a hot foam cutting wire streched between them. A typical use is for cutting foam cores for model airplane wings.

Here's how I would set it up - One X-Y stage would be called X & Y in Mach and the other would be A & B. A is parallel to X and B is parallel to Y. A & B are both configured as LINEAR. And I am assuming the steps per inch are the same for all axis.

There are 2 ways of controlling the motion - if your parts have no tapers you could pprogram everything as X & Y moves and all motion is available, go to the Functin Cfg menu and select formulas and in the A line put X and in the B line put Y. The AB stage will copy the motion of the XY stage. If you want some other ratio (AB end 3/4 of the XY end then you would put x*.75 in the A line and y*.75 for B)

The other method has more flexibility - but is restricted to G0 and G1 - No changes in formulas, A =A, B=B, but you would have to program only in line segments. each line would look like this - G1 X___ Y___ A___ B___ F___ and would start and finish at the same time. As long as you used short line segments you would hardly notice them, and a quick touch with sandpaper would take care of that, BUT both ends of the motion could have completely different motin profiles. Airfoil 1 and the XY end, and Airfoil B on the AB end. You could even program a twist intothe profile, End XY is parallel to the X axis and AB is rotated 3 degress to the A axis.

Does this sound like what you are trying to do?