HELP.....Motor Tuning Question

[NardisAmps]

Hello,

My X-axis has been a little off ever since I built my small
router, I just never fixed it because it wasn't enough
to worry about (like 1/16" on a 29"span)

So finally I decided to fix it because I need to
machine some close tolerance aluminum parts. So I got
it accurate within a few Thousandths over a 29" span.
I figured the closer I had it over the longest span,
the smaller the margin for error on a shorter
distance. Right?

That's not proving to be the case though. Its actually
MORE off on a 17" span now (like maybe a 32nd) than on 29" (few thou). How can that be? Any idea?? In reality I need it closest on the
smaller parts. Thanks in advance for any help! I'm using a Ballscrew with Zero backlash by the way.

Best Regards,
Nardis
270-576-7030

[jdbaker]

We're having this same problem, did you (or anyone else) ever get this figured out? It's very frustrating that we can either have it tuned for small parts or large parts, but not both (it seems like tuning it to one would tune it to the other). Any help with this would be appreciated (we too are using ball screws on our machine).

[SORCHEROR]

it shouldnt matter small or big parts if your setting the motors up correctly,need more info,what size motors?i assume they are steppers,and what drivers at how many volts?more volts better top speed power,maybe your running they faster than they can be and thats why the larger parts are not coming out right,let us know more info,and ill ponder upon it,i had similar problems and finally gave into gecko drivers and 54 volt power,worked the nuts

steve

[Coogrrr]

I just setup Mach3 for the first time and watched all the videos and RTFM'd, all of it. I am a computer programmer for nearly 20yrs now and I know how to follow instructions and setup software and most certainly get it right after 2 days, here is my problem...

I setup mach3 for the steps I am supposed to use and tell X or y to run off 4 or 10 inches in the + direction when I run it back 3.5 or 9.5 inches toward home or - direction it hits the limit/home switch with either 1 inch left on the 4" run or several inches left on the 10 inch run.

I am confused on how it can move perfectly in the + direction then on the exact reverse go farther than it is supposed to not come up short but run too far???


help???

EDITED:
forgot to put this in.
the motors and steppers and power supply are all surestep bought brand new from Automation Direct and all bought to match for voltage driver and step.

got a double recheck on the wirring and all is good.

[ger21]

Try changing the active low setting for the step pins, and increase the pulse width.

[jdbaker]

Our machine has 2 1200oz motors driving the y-axis (one on each side), and we have Gecko G202 drivers for both motors (same setup on the x-axis, except only 1 motor and gecko driver). We have a few computer power supplies powering all of the motors (including the 300oz z-axis motor with a G201 driver).

All of the motors are from http://homeshopcnc.com/, the 1200oz ones are specifically Model # RHT34-1200 (not the dual shaft ones).

[ger21]

JDbaker, seems like it may be due to screw lead error. You ght want to look into playing around with Mach3's screw mapping feature.

[jdbaker]

I played some more with this over the weekend. I don't think it's scew lead error, because then it would be innacurate on both small and large parts, not one or the other (right?).

We finally tuned the machine to cut more accurately on the larger items, and then changed our tool paths to use bigger cuts than we wanted (terribly inaccurate and time consuming with trial and error, but worked for a sort-term solution as I needed to cut a few parts).

It's odd that someone else complained about this exact problem, I wonder what it is. We just recently upgraded the drivers to gecko and added the extra motor, and we were really looking forward to the advantages of that setup, but this has really been a pain to get correct.