I am very new to cnc, and have recently built a Phlatprinter MKII from phlatboyz.com  I am using a Mechatronics bi polar 3 axis micro step motor driver, with 3 nema-23 stepper motors.  The machine is all belt driven.  The x axis is a large belt driven roller similar to that of a large format printer.  Y and Z are on a gantry below the cutting surface, and the cutting bit protrudes from below.  When I run a cut file X and Y do not finish where they start.  Y drifts progressively farther and farther in the + direction, and Z does so as well.  To help diagnose the problem I rewired coil 1 to coil 2, and coil 2 to coil 1 reversing the steppers, then in mach I reversed settings so everything ran in the right directions again.  After reversing the steppers I still have the drift but in the opposite directions.  The drift is very consistant.  The same cut file ran over and over leaves the cutter the same distance off.  I have tried lowering the feed rates and acceleration, with no changes in the drift.

Is it possible that one coil is working better than the other in the steppers?  If I could set steps per unit in the + direction, and then in the - direction independantly couldn't I compensate for this drift?

Jeff

Sometime, board can miss step because of the optocoupler that are not fast enough. In motor tuning, try to increase the step and direction duration, if you have one in both , try with 5.

What breakout board are you using?

Regards,
Ray L.

Ray L.       I am using a mechatronics bi polar 3 axis micro step motor driver, from www.easy-cnc.com  , 

ostie01    I have already tried increasing the step and direction pulse

It could be mechanical?  Have a VERY close look at your belts/pulleys when you are running your program.  Are you slipping a tooth on your pulleys?  Sometimes this will happen if your belts are not tight.

FAOMLVR,
Are you steps per units correct?
RICH

sshneider     belts and pulleys are tight, been through this thing with a fine tooth comb,  also checked set screws, all stepper shafts have flats ground for the set screws.

RICH    Steps per unit are as close as I can get them, with a 6" digital vernier calipers.  Regardless of whether they are right or not shouldn't zero be zero?

Have you tried changing the Active state of the Dir signal?

Hood

Hood    If you mean "dir lowActive"  Ports & Pins,  Motor Outputs,   then yes I have tried it.

I may have found something,  I don't know what video card I have.  The system is fast enough, and has enough memory, but I don't know what video card I have, or how to find out.

Another thing I found,  today I was listening to the radio,  when I powered up my machine I got a lot of static on my radio.

Jeff

Is it an onboard card or is it an AGP?
Right click on desktop, choose properties then settings tab then advanced tab then finally adapter and it will tell you the card make/model etc you have.
Hood