r&p motor tuning/accel rates

[groomden]

Hi,

I'm using Ahren's r&p system and I've just now reached the point to enter the motor tuning info in Mach3.

I have the Probotix stuff and I'm running 1/8 microsteps on 200 step per rev steppers.

Ahren has a 1" pitch circle pinion gear, and a 3:1 pulley reduction.

Any help would be really appreciated getting this set up, i'm confused.

The nearest i've figured out is 1600/3.14159 for 509.3 steps/per rev but this isn't even close to equaling an inch of travel on my machine....


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as a second question i'd like to know what settings to use on a 1/2x10 acme threaded rod with 5 starts using 1/8 stepping?

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and as a third question what accel should i set for my r&p drives at:
100in/min,
200in/min,
400in/min... at least as a sane starting point.


thanks!
dennis

[CarveOne]

I hope you get the answers to your questions soon. I am also working on the same r&p conversion as hard as I can go.

CarveOne

[tulsaturbo]

Is there any reason you can't use the (Settings alt6), Axis calibration (Set steps per unit) on Mach3 to configure the correct motor/steps for your particular setup?

[ger21]

Try (1600 x 3)/ 3.14.......

[calgrdnr]

As for steps per inch, the pitch circle on the pinion gear is 1", and the reduction is 3:1, so with 10x microstepping you have 200 steps x 10(microstepping) / revolution, 1 revolution per 3.14159 x 1 inches, and a 3x multiplier for the gear reduction. This comes out to 1909.86 pulses per inch. Ahren www.cncrouterparts.com

Off the JoesCNC forum hope this helps

Kent

[groomden]

Originally Posted by ger21 Try (1600 x 3)/ 3.14.......

I wound up with (1600x3)/3.14159=1527.8887, or 1527.89 steps per inch in Mach 3. Thanks as usual!

Now if you could also help with changing my screw settings to 1/8 step as well, I would be very much obliged;-) i currently have 400 steps for 1 revolution = .5 inch, so 800 steps per inch. so would the new number be 3200?

@tulsaturbo -- you could do it that way too, but I wanted to know the math behind the number as well, someday i'm determined to 'get' it.

[groomden]

Originally Posted by CarveOne I hope you get the answers to your questions soon. I am also working on the same r&p conversion as hard as I can go. CarveOne

if you are updating a slaved router setup where one of the motor's is reversed, make sure you do the opposite when you set up the new system... i'm not saying i had 'my' axis trying to go in opposite directions, but you never know;-)

[ger21]

Originally Posted by groomden Now if you could also help with changing my screw settings to 1/8 step as well, I would be very much obliged;-) i currently have 400 steps for 1 revolution = .5 inch, so 800 steps per inch. so would the new number be 3200?

If they are 1/2-10 5 start, then yes.

[CarveOne]

Originally Posted by groomden if you are updating a slaved router setup where one of the motor's is reversed, make sure you do the opposite when you set up the new system... i'm not saying i had 'my' axis trying to go in opposite directions, but you never know;-)

Mine is a new build. Two pinion drives on the X axis. Me, get it backwards? Ha! Just watch me.....

CarveOne

[tulsaturbo]

For optimum torque performance of the stepper do you try and calculate the gearing to where it come closest to the motors (steps per inch). I'm at 1/8th step (1600). Do I try and gear it to where I get the ratio as close to the 1600 as possible for maximum torque of the motor?

I run a drive belt system directly off my motor. Running a 15t pulley puts me at 533.29 steps which tells me that I'm at 1/3 the torque available at 1600 steps. This gives me 3" of travel per motor revolution.

At around 200+ ipm my machine starts messing up on its cuts. I'm assuming its losing step because of the available torque at that speed. My goal is 350 ipm.

The smallest pulley I can get is 10T. I'm ordering them tomorrow from Mcmasters. This would put me at 799.522 steps which is roughly half the torque available at 1600 steps. This gives me 2" of travel per motor revoltion. I'm trying to see if I can get to my goal without going to any sort of gear reduction.

I don't know how to calculate the motors max rpm into these calculations so I don't know how it will be affected when trying to go 350 ipm.

What do you guys think? Am I calculating this correctly?

[ger21]

If you want 350ipm, and you move 2" per revolution, the force available is 1/2 of the pitch diameter, times the motors torque at 175rpm (motor speed at 350ipm). You'll need a torque curve to calculate the force.

You probably want to get closer to 1" of travel per motor revolution.

[tulsaturbo]

Originally Posted by ger21 If you want 350ipm, and you move 2" per revolution, the force available is 1/2 of the pitch diameter, times the motors torque at 175rpm (motor speed at 350ipm). You'll need a torque curve to calculate the force. You probably want to get closer to 1" of travel per motor revolution.

Yes, I agree.

The 10 tooth XL pulley (.637 pitch dia) is the smallest that I have been able to find so I guess I'm stuck with the 2" per travel per motor revolution for now unless I can find another source to a smaller XL pulley. I guess I'll order the 10 tooth pulley and try it out to see what happens...