help motor tuning

[wilkies]

Need help with this table setup, Im running nema 23 motors with 1 1/4 gear 20tpi with 1meter rack 6tpi from ebay,im having a heck of a time trying to tune this setup in mach 3,hope some can help an old timer out with this. thank dave

[acourtjester]

Motor tuning is simple with Mach 3 what you are going to do is set your table so you move the 3 axis. Drive each axis to the minus end of travel and then go to the "settings page" (alt 6) just above the reset box is "set steps per" click on that this will bring up a menu called "Axis selection" this is where you select which axis you are going to calibrate. It is set for X to start, click on OK This will bring up another menu "Answer This" Place a mark on the rail to show the starting point (for you to measure from. Put in a distance for the axis to travel say 2" or 50 mm. Click on OK the axis will move in a positive direction measure from you starting mark (be sure you have set inch or mm in the lower right side of the setting page). now enter that distance in the box where it asks how far did it go. Mach 3 will calculate the steps per for you click on OK after that is done. Now repeat that about 3 time but travel a greater distance each time to better refine the calculations. Now do the same for the other 2 axis that same manor.

[wilkies]

ive tried that,it gets it close .05 to .010 once once or twice,thought some one could calculate it for me,also makes lots of noise on slow speeds 24ipm. fine on fast speeds of 220 ipm.thanks dave

[tcaudle]

The type motor drivers you have can help and if they are direct drive to the pinion gear will help. At 6 teeth per inch and direct drive your resolution will be .166" ! So then its up to microstepping to try and smooth that out but it can only do so much. That could explain why it rough at low speed and smoother at 200 IPM. Without micro stepping if you can get .010 /inch at low speed then consider it good. The BEST resolution you could hope for at low speeds with 10X micro stepping is .002 per step and probably a lot worse. With no micro steeping it drops to .02 per step.

[wilkies]

ok so would the .166 be the steps per for motor tune? or? dave

[wilkies]

would changing to a smaller gear with less teeth be of much help.

[tcaudle]

The ONLY way you can calculate the Steps per Unit is to know:
Microstep number (if any)
Any belt reduction ratio (if any)
DP (diameter of the final drive gear at the pitch radius. Just measuring the diameter of the gear will get you close

What we DO know is that the steppers are 200 FULL steps per rev.

You have to calibrate in steps per unit meaning "how many steps from the computer does it take to move the axis linearly by one UNIT (inch or mm)
On the gear size=tooth count Probably not although ti will raise the resolution and torque some. The problem with course teeth is the teeth are futher apart so you have fewer of them engaged (or partially engaged) as it turns. A smaller pinion and a finer pitch (say 20 TPI ) will help on the slow speed cogging SOME but if your drivers are not microstepping it still will run pretty ragged. I have used a lot of 20/20 rack (20 TPI and 20 deg pressure angle) and paired with good drivers you can get some really smooth motion .