Stepping problem Too

[dakenskys]

Hi Everyone,

I have a problem that I can't figure out too!

I'm running DeskNC with a Camtonics 3 axis homebuilt.

I was running 1.8 deg steppers on microstep, so .9 deg which is 400 steps per revolution.
My leadscrew is 2 turns per inch, so I set the steps per unit at 800 and no problem.

Now, I put in 2 gears to increase torque which works fine, but I can't seem to get the proper steps per inch now.

On the motor is a 12 tooth gear and on the leadscrew is a 36 tooth gear. So I figure 1:3 ratio and set the steps per unit to 2400 instead of 800.

When I try to cut a 1 inch line, it looks like maybe 1/3 that. Ok so I set it for 266.6 steps, and no change.

What am I doing wrong? I've tried all kinds of numbers and I get wierd results, from 1/3 inch to about 7".

HHHHEEEEELLLLLLPPPPP? Please.

Ken

[HuFlungDung]

Hi Dakenskys

Did you double check the pitch of your lead screws? 2 turns per inch is a pretty coarse pitch unless this is a really big machine, or you bought some special ball screws.

Are you using any kind of feedback system on this machine, such as an encoder? Where is it mounted if it exists?

Does the axis travel quite easily? Maybe you are losing steps due to loading?

[dakenskys]

Hi Hu,

Nope...it is a 2 turns per inch screw. They are precision leadscrews with anti-backlash nuts. My machine is about 16" x 24".

No feedback system...and the screws turn fairly easily, so no drag or undue loading.

[HuFlungDung]

If I recall correctly, some of the other guys were remarking that their stepper motors lost a lot of power when they decreased the step angle. This will cause you to loose steps. This is also the problem with an openloop system (no feedback): the control has no way of knowing that the machine has not reached position because it is just pushing out so and so many steps.

Try going back to full step mode and reduce your accel/decel and top speed settings to see if you can make it work at low speeds. Then, you can work your way back up to where it begins to misposition. This is something you can try at least until the more experienced stepper guys can post an anwer here for you

[dakenskys]

Well, I went back and instead of editing my usual machine setup, I created a new "machine". And now it works! Don't know what I did to make it work? I did increase the max steps per second from 500 to 2000. Anyway, I'm just happy that it works now.

I'll see about playing with the other settings. This is what I have it at now, and if you see any suggestions, would be glad to try them:

Max steps/sec= 2000
Start velocity (sps)= 300
Accel (sps*s)= 10000


Thanks

Ken