I just reread through the post to make sure that I remembered mach3 as being the cnc control software. And I believe that is still the case.
Khalid can correct me if I'm too far off.
lmlamb,
If you haven't find it already, your steps, acceleration and velocity should all be fixed. You'll need to do the math to find out your stepper motor resolution etc, to find out how many steps you need per unit of measurement that your running in. After that, you never touch those settings again. At least that is my understanding from my cnc mill.
You will need to actually adjust the gcode in the patterns. I'm working on a peice of software for my wife on that front. Writing it in c# so I guess I'll be bumping head's with Khalid's VB mother language has he put it. Unfortunately, I may have to change it to VBS to work with Mach3. I need to research that a little more. As I believe that you can use custom buttons to make calls to vbscripts. If that is the case, the gcode could be resized/rotated/skewed etc from inside mach.
Then you would adjust your feedrate through the code. i.e. 5 inches per minute etc...
N10G00X0.000Y0.000F5
I'm planning to devote a few brain cycles to this over the next week and see if I can come up with a "quilting" friendly interface for Mach.
Khalid, I'm assuming that you scrapped the idea of using the arduino. If not, I had a lot of heartache using the same product to attempt an build a stitch regulator. I used an Arduino with us digital quadratic encoders, which fed to PWM signal then to a n-channel mosfet. I was attempting to vary the duty cycle of the motor, so that it would slow down or speed up according to feed back from encoders. Unfortunately, it lacked responsiveness and the power at the low duty cycle would stall the machine. Before I ended up buying a new machine, my plan was to replace the motor with a servo and use a gecko fed by the arduino. I never got around to that, but I have reservations about the responsiveness. If the machine doesn't respond at the first sign of movement, the needle will drag in the cloth. An analog system might be a better approach, but I lack the core electronic skills. My thought was to use some type of timer. I.e. 555 timer, to send x number of steps to the gecko for every pulse of encoder. However, you have to monitor both axis encoders and figure how which one is faster etc...
Either way, when the machine is cnc controlled. You can make the machines speed to motor speed and end up with a happy median. If your wife ever manually controls the machine. i.e. free hand motion. You may want to revisit the stitch regulator.
Enough ramblings from me... going to bed... Zzz