You don’t have to do a linear Z axis but the bigger stepper doesn’t fit in the stock Z configuration. You could get a long piece of makerslide instead of the 200 mm piece and The acme rod length may come into play too.
I wasn’t really clear with what I meant. I was talking about upgrading to more powerful X and Y steppers, primarily. I was curious if there was anything to gain from bigger stepper motors, or if the sloppy Z axis would need to be upgraded first to see any real gains.
This is what I did:
I used a longer MakerSlide and rod.
Would I do it again? Not sure. Having the same motors everywhere is nice but not sure if the stronger motor on the Z is worth it.
I do enjoy the higher Z axis mostly for easier tool changing. More clearance for my hands and tools especially when stock is still underneath the spindle.
However bigger motors on the X and Y are totally worth it!!!
tell me why the bigger motors are worth it. What exactly are you gaining? Higher feed rates?
Higher torque which equates to the potential for higher feed rates and/or depths of cut.
I knew I upgraded for a reason!
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If you run a stepper motor at the voltage specified for the motor then you will get the current and torque specified for the motor.
For a 3.2 volt 2.8 amp/phase 140 oz.in stepper motor if you apply 3.2 volts to the coils then you will get 2.8 amps of current in each coil (assuming your power supply can supply 5.6 amps [2 x 2.8]) and the motor will have a holding torque of 140 oz.in.
When you have an inductor, ie motor winding, the voltage across the coil does not rise to the power supply voltage instantaneously when the voltage is applied. There is a DC resistance as well as an AC inductance associated with the coil of wire that impedes the current rise so the current through the coil is also not instantaneous.
You can get better performance from the motor if you can get the current up to the rated value faster. You can do that by raising the operating voltage which will cause the current in the coils to rise to the rated value faster. More voltage, faster current rise, faster attaining the rated torque.
However, if you let the current rise beyond the capabilities of the wire in the winding then you get a damaged motor.
To use a higher voltage you then have to turn the voltage on until the current rises to the limit and then turn the voltage off to prevent the current from rising above the current limit for the coil.
Hence the stepper motor driver which “chops” the current flow once the current limit is reached.
Now we have a frequency involved. If the “chopper” driver turns the voltage on and off faster than the motor can get up to the current limit then you don’t get all the torque that you would have had, had the motor been running with the specified voltage.
A very simplified view, but done, so that it is easy to understand.
Yes that’s why you generally have a torque to speed curve of a stepper motor.
Generally speaking, if you start at a higher torque level given the same ideal conditions, you’ll get more torque across the speed range. If the steppers curve drops off greater, then this obviously won’t be the case and different coil parameters will affect this curve.
Now, Inventables doesn’t post the torque curve of the NEMA 23 motors that they sell. Neither does StepperOnline of the 269 oz-in steppers so it’s hard to say with certainty but it’s semi-safe to say that the higher potential torque will most likely lead to higher torque at the same rpm than the lower potential torque. This assumes a lot of variables but it’s not an illogical assumption to make.
If you have more torque at higher speeds, you can generally run through materials quicker and potentially deeper because you have the available torque.
At least, that’s my understanding of how it works.
I think this is a good thread to ask something I was wondering about recently. Microstepping affects resolution & torque. Does it also affect max RPMs on a given motor?
For instance in the case of the 269oz.in StepperOnline motors, what is the max RPM that people who use them can get when not under load (i.e. rapids) before they start stalling? Mine stall between 500~600 RPMs depending on acceleration.
To measure you do not need a tachometer, just divide your max $110 (or $111 or $112 depending on the axis under test) with the mm/revolution (e.g. 60 for a 20T 3GT pulley).
One factor that affects this for the Xcarve (Arduino/Xcontroller) is that grbl is limited to 30000 steps/second.
Thanks, I had no idea about this.
Then (30000usteps/sec * 60sec/min ) / (200steps/revolution * X usteps/step)
X | max RPM
1 | 9000
2 | 4500
4 | 2250
8 | 1125
16 | 562.5
So in my case @1/8 ustepping I’m hitting the motor’s limit before the Arduino’s limit.
I’m still curious about what other people experience with their 269s.
I’m not using grbl (Mach3) with my 269 oz/in motors…how do I figure this…I am running 1250 steps per inch on the standard 20 tooth pulleys?
Phil, it doesn’t matter. You can still do the test while spinning in the air.
Set your $110 (if your broken belt is on the X) to something very high and send some G1’s 100mm (4in) left then right while gradually increasing the F by 500mm/min (20in/min) till you hear the motor stalling.
Don’t forget to switch back your $110 to your original setting. I’m not buying you more belts if you forget 
The resolution does not matter. If by standard you mean 2mm pitch, then divide the maximum feedrate (in mm) you can get by 40.
I am afraid to go faster…lol
mine can smoothly go 1000 IPM…I have not tried faster.
so that is 25400 mm per minute…and I am sure it will go faster, just not going to try 
This is 25.4*1000/40=635RPM
You must be very close to their limit. It won’t harm them to stall for a couple of seconds. This is Sonny’s recommendation in the GRBL Wiki for tuning your max feed and acceleration.
I may play with it later, but not sure I need to figure my max feedrate out since I have my rapids set to 500 IPM / 12700 mm per inch. But it is cool watching this thing cruise at 1000IPM
Mine is actually 1252 and some change…I calibrated the steps with mach3.
Not sure, but the travel distance is spot on…it is as accurate as I can measure.
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