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Author Topic: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)  (Read 25019 times)

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Offline Hood

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Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #40 on: March 30, 2011, 08:26:51 AM »
:D

Best to concentrate on the Z though as it has known values so we can work out where the issue is depending on what US Digital say.
Hood
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #41 on: March 30, 2011, 09:02:00 AM »
just for some more info: If i wanted to calculate my minimum step length.

1000 Line encoders (4000 count quad)
X: 1"/ 4000=.00025"
Y: 1"/ 4000=.00025"
Z: .1"/4000 = .000025"

250 Line encoders (1000 count quad)
X: 1"/1000= .001"
Y: 1"/1000= .001"
Z: .1" / 1000= .0001"

(if i changed to a 2000 line encoder (8000 count quad))
X: 1"/8000= .000125"
Y: 1"/8000= .000125"
Z: .1"/8000= .0000125"

Offline Hood

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Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #42 on: March 30, 2011, 09:04:36 AM »
Yes thats correct but keep in mind the limitations of the Viper, that is if it is 125KHz then it will limit your rapid speed the higher the encoder count you go.
Hood
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #43 on: March 30, 2011, 09:17:15 AM »
I remember sometimes seeing a .00025" deviation from zero or a position i commanded it to go sometimes on the mach 3 dro! Is that because it can only take that small of a step?

I would command say, X10" and sometimes it would land exactly @ X9.99975" Hopefully tomorrow will shed some light on this.

I wouldn't mind running a really high resolution encoder if i had a really small mill/table. My table is about 60" wide usable and 136" usable long. It would take forever to get anywhere haha. We will see! :D
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #44 on: March 30, 2011, 09:19:24 AM »
I will probably stick with the smooth stepper so i can take advantage of the 125khz. Might as well get as much speed as i can for free since i already bought it. I have yet to try out the new backlash plugin! Excited!!

Offline Hood

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Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #45 on: March 30, 2011, 09:21:45 AM »
Actually what you said above is not true as you have not taken gearing into consideration so X and Y would be 10 times smaller. for a min step.

It all depends what you need, on a wood cutting machine do you really need very high resolution?

Hood
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #46 on: March 30, 2011, 09:28:59 AM »
I will be machining aluminum sheet/plate.

OOO so take all those numbers then divide them by 10 i see. opps! :D

1000 Line encoders (4000 count quad)
X: 1"/ 4000/10=.000025"
Y: 1"/ 4000/10=.000025"
Z: .1"/4000/10=.0000025"

Since the Y axis has a 1.25" gear instead of the 1" gear how does that affect things?

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Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #47 on: March 30, 2011, 09:31:08 AM »
Actually you would also have to take into account the value travelled by one rev of the output so your step value on X and Y would be different than what I said in the last mail.
What you need is the step per inch, that will give you your min resolution. So really you need encoder counts, any gearing, any electronic gearing and finally pitch to work out what the min step will be.
Hood
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #48 on: March 30, 2011, 06:03:54 PM »
Support from US digital got back to me today. I have 1000Line count encoders, with 4000 quadrature counts.

"The "CPR" or counts per revolution is the number of lines on the disc. The "PPR" is the number of pulses in quadrature (x4) it gives per one revolution".

Regardless if i use a smooth stepper or parallel port my Viper drive max is 125Khz.

That means my servo speed max would be 125,000khz / 4,000 pulses per revolution x 60 =1875 RPM

My X and Y axis both have a 10:1 gear reduction so the output gear would turn @ 187.5 RPM.

The Z axis has no gear reduction and is linked to a .1" pitch lead screw: 1875 rpm x .1" = 187.5 ipm max.

My Y axis has a 1.25" output gear. 187.5RPM x 1.25" x 3.14 = 735.9375 IPM MAX.

My X axis has a 1" output gear. 187.5 X 1" x 3.14= 588.75 IPM MAX
-------------------------------------------------------------------------------------------------------
Max servo rotation speed: 1875RPM with 1000 line encoders @ 4000 counts per revolution in quadrature. 125Khz, limited by driver.
X axis: 588.75 ipm
Y axis:735.9375 ipm
Z axis: 187.5 ipm

These are my current mach setttings: They don't seem to match what i have calculated.
X axis: 3191.931756 steps per inch @ 700IPM (10:1 gear reduction) (1"output gear *i think*) (1000CPR encoder)
Y axis: 2491.704346 steps per inch @ 499.98IPM (10:1 gear reduction) (1.25" output gear *i think*) (1000CPR encoder)
Z axis: 10,040.73425 steps per inch @ 49.998IPM (No gear reduction directly linked to lead screw) (1000CPR Encoder)
Re: Mach 3 Driver test. Results for 3 computers, which is best? (PICS)
« Reply #49 on: March 30, 2011, 06:09:32 PM »
In the Viper manual it does state this:
125Khz max step rate.

"The viper can handle up to 625Khz
encoder frequency (assuming good cableing )"

Even more confused!!