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Author Topic: Nema23 velocity and acceleration  (Read 14734 times)

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Offline kiark

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Nema23 velocity and acceleration
« on: August 15, 2014, 10:29:27 AM »
Hi!

im a little new to mach3 but very happy about me buying it! im also a little new to cnc machines and plz forgive me for my newbie questions but i couldnt find anything about this somewhere.

So:

im building a 3-axis eshapeoko with double Y axis. i can jog the machine just fine. Now i have the basic problem of tuning the motors.

im using this name23s:

 Form factor: NEMA23

Motor length: 51 mm

Motor weight: 560 g

Shaft diameter: 6.35 mm (0.25 inch)
Step angle: 0.9°
Rated current: 1.7 A
Rated voltage: 6.8 V
Phase resistance: 4 ohm
Phase inductance: 14 mH
Holding torque: 9000 g·cm (0.88 N·m, 125 oz·in)
Rotor inertia: 240 g·cm2
Detent torque: 260 g·cm
Wiring: bipolar (4-wire)

as im using 1/4 steps and have 400 per turn i set the steps per to 1600 for my x and y axis.
for my z axis im using an tr8 X 2 trapezoidal lead screw which means im making 2 mm per turn, so i set the axis to 800 (is this right?)

but now to my basic problem. i can adjust the the motors so they just sound fine with acceleration and velocity settings, but as i want to optimize my machine between a good accuracy and speed, what would be good settings for the motors stated above? i heard it has something to do with the oz-in but i just dont know what exactly.

hope u can help me,

kiark

Offline Davek0974

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Re: Nema23 velocity and acceleration
« Reply #1 on: August 15, 2014, 10:45:47 AM »
I think it's all down to what they will take, I had the same issues when I built my table with 23's, I have the same Z screw too. That is the same motor I have on my Z axis, on the X & Y axes I have the larger 4A nema 23's, my table is all belt drive apart from the Z which is direct.

My machine is a small plasma(600x600 cut) and found i could put the speed up to silly values which i thought was great until i started cut-testing in and found the weak spots - stability, belts, torch wobble etc.

I had to slow her down a bit but push the acceleration up to get good corners.

I used the auto-setup to fine tune my steps-per figures, it works very well when used across a large distance.
Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline 1Acnc

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Re: Nema23 velocity and acceleration
« Reply #2 on: August 15, 2014, 12:20:25 PM »
One of the things I did was to see how fast I could run my Y & X axes to see where the motor would stall, was not cutting. I am direct drive and my systems, with smaller motor then you have, would run at 170 ipm. I do mostly wood so I do not run more then 70 ipm, so feel safe that I will not lose steps.  As motor increase in RPM they lose power to drive the screw. So once they are stalled and you back off the speed they pick up more power to turn the screw, that is why I feel safe at 50% speed, I am new to this also but that is what I can up with.
Re: Nema23 velocity and acceleration
« Reply #3 on: August 15, 2014, 08:19:40 PM »
Your motors are relatively high voltage and high inductance so it will require a high voltage to drive them fast. If your drives are not currently on a power supply close to their rated voltage consider getting a higher voltage supply.  If you drives are say 40 volt rated and you have a 24 volt supply currently then a 36 volt supply would make a big difference.


Offline kiark

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Re: Nema23 velocity and acceleration
« Reply #4 on: August 16, 2014, 07:11:30 AM »
Hi!

first of all, thanks for the help!

im running every motor on a 100 velocity and a 70 acceleration which seems to work just fine and the motors also sound nice!

im using a 36v supply and the motors get 2amp which i set up to that value by using th dip swtches on a tb6600 5A controller i bought.

one thing that makes me curious is, that im having a 1000mm x 1500mm table but when i jog the machine to the coordinates for Example 30 on my x-axis (which should be in mm, right? - i set the native units to mm) the machine jogs way more than 30 mm.

davek: u stated that u made these adjustments with a wizard. i went through all the menus but couldnt find any :/ how did u do that?

is it possible to measure the distance between homing and limit and tell the machine how far it actually went? i have a laser measuring device here that would work fine that way i guess.

kiark

Offline Davek0974

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Bridgeport Mill, Mach3 V062, CSMIO-IP/A controller, AC Servo Drives

Offline kiark

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Re: Nema23 velocity and acceleration
« Reply #6 on: August 18, 2014, 08:10:32 AM »
hi,

thanks for the link!

somehow my steps per unit dont make alot of sense! following alot of calculations i get to this:

i set up my machine the following:

1/16 microstepping
0.9 degree motors
belt driven

when i calculate this using machs3 own calculato, i should have a step per of 6400! using mm btw.

using this throws my machine completely off calibration!

when i move my x-axis for example for +10.0000 the machine moves 250mm instead

when i set the steps per to 160 i get about a 1 to 1 ratio. but the machine moves really slow, even when putting up the velocity alot.

does mach3 axis movement even show in mm or is it cm?

thanks, kiark

Offline Fastest1

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Re: Nema23 velocity and acceleration
« Reply #7 on: August 18, 2014, 10:09:22 AM »
Typically steppers are 1.8 degree or 200 steps per rotation. If you are using 1/4 micro stepping, it should have been 800 steps per unit (200 x 4). If you did reset it to 1/16 (which would give you an unachievable resolution) it would need a 3200 steps per unit. This does not take into account any additional gearing.  

Sorry just noticed on your last post that your steppers are .9 degree, so that would make the above calculations need to be doubled. If you are at 1/16, 6400 steps would be correct.

« Last Edit: August 18, 2014, 10:12:11 AM by Fastest1 »
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