Newbie- Stepper motor size for X3 mill

[WindyMiller]

Hi - I need help sizing stepper motors for my new Sieg super X3, my intention is to convert to cnc using cadmonkey's design for inspiration, most of the parts that I make are in aluminium or engineering plastics so I feel that using motors rated at over 3nm are a bit over the top, your valued comments would be appreciated.
Regards

Paul

Sieg X2, Sieg X3 Super, Sieg C4

[ataxy]

my opinion 465oz to 495oz nema23 for the x and y and 600oz for the z nema34

[WindyMiller]

Thanks for the info Ataxy, seems that i was light on the sizes as the conversion to metric would make them around 360Ncm (3.6Nm) for the X & Y axis and 450Ncm (4.5Nm) for the Z.
the conversion i am undertaking is loosely based on cadmonkeys design but my Z axis will be similar to Syils inasmuch as the stepper will have direct connection to the ballscrew shaft, this in my opinion gives a nice compact drive without having external mounting brackets, also when i bought the mill i asked for a set of ballscrews and shafts - these came ready finished similar to the Syil ones (well the Z axis anyway)

Regards

Paul

[Crevice Reamer]

Hi Paul!

You really shouldn't pick your motors until you know what drivers and PSU you will be using. Everything has to work together. You will want to wire the motors Bipolar Parallel for best results.

Voltage = power and power = speed. Formula for best motor voltage is 32 times the square root of motor inductance. Try to get as close to that as possible.

Many drivers restrict max voltage. In that case, you should try to find a motor with best voltage equal to or slightly above that restriction.

ON my SX3, I used Keling 425s for X and Y. Their best voltage is 85V, so I used G203s and a 72V PSU. These give good performance--250 IPM rapids, But there are better motors available now.

Today, I would use $49 65V Keling KL23H284-35-4B 387s (back in stock by 2/10/09) for the X and Y, and a $89 640 OZ KL34280-45-8A for the Z axis. I would power these with the $129 KL5010 power supply. I would again go with the G203Vs because there is no better driver anywhere.

If there were a 640 oz N34 motor that would fit it's parameters, I would definitely go with the much less expensive G540, which is a Jr set of 203Vs.

http://geckodrive.com/product.aspx?c=3&i=14460

http://kelinginc.net/KL23H284-35-4B.pdf
http://kelinginc.net/KL34H280-45-8A.pdf

http://kelinginc.net/SwitchingPowerSupply.html

When you are buying the N34 motor, remember that only a single stack motor will fit in the space under the column.

CR.

[ScrewLoose]

Wow...

Great post.

I'm buying a Grizzly G0463 mill and am planning to convert it.

Been pouring over this forum, Cadmonkey's and Hoss's sites....

Let's say, it has been a bit of information overload.

Cheers, Bob

[Crevice Reamer]

Never mind.

[project5k]

i went with nema 23 495oz-in on all 3 axis, 48v supply, cncfusion ballscrew conversion kit, and gecko 203v's.. very happy combination. motors dont heat up too much, and thats why i went 48v rather than something higher, i just didnt see the need, and haven't yet.

[neilw20]

You really don't need FAST rapids.
Who wants to cut air above 100 ipm (2500mm/min) anyway.
Well written G code won't be full of wild random seeks anyway.
I leave mine at 60 ipm (1500mm/min). I reduced mine so that my brain reaction time could save on crashes.
If it was a router with a big table, then the rapids may be of more use.

[project5k]

this is true, but i figure it this way. a properly written set of code, shouldnt cause crashes, and secondly you should have an estop button handy thats tied into your control software.

not to mention that this mill is acting as a sort of test bed for the router i'm building.. and it will be big, well, bigger than the mill anyway... so with what i've learned with this about speeds, and whatnot, when i get back to my router, i'll have that much more figured out. I'm also planning to use the same computer, and drivers, to run both my mill and the table router, at different times ofcourse, but i dont see the need to duplicate thoes components right now, i'll never need to use them both at the same time.

[HimyKabibble]

Originally Posted by project5k this is true, but i figure it this way. a properly written set of code, shouldnt cause crashes, and secondly you should have an estop button handy thats tied into your control software. not to mention that this mill is acting as a sort of test bed for the router i'm building.. and it will be big, well, bigger than the mill anyway... so with what i've learned with this about speeds, and whatnot, when i get back to my router, i'll have that much more figured out. I'm also planning to use the same computer, and drivers, to run both my mill and the table router, at different times ofcourse, but i dont see the need to duplicate thoes components right now, i'll never need to use them both at the same time.

"you should have an estop button handy thats tied into your control software" - Actually, that's very bad practice. The E-Stop should act as directly as possible on the motor drives themselves, and NOT be dependant on software. It's a good idea to *also* feed an E-stop signal to the software to notify it that the drives have been disabled, but you do not want to be dependant on software (which may have crashed and be the reason you NEED to E-stop) to be required to actually stop the machine.

Regards,
Ray L.

[neilw20]

I have wired the E-Stop to the enable line on the stepper drivers.
If the spindle stops dead due to tripping over-current, it needs to issue and instant e-stop so that the feed stops when the cutter is not moving.
This requires a low-speed comparator from the hall sensors on the spindle motor.
Using software to control this safety issue is NOT AN OPTION that should be considered.
The best thing is a safety relay that drops out. That's how the big end of town do it, and then some still do not sense spindle stall.
A cutter not turning, with feed will shatter, and the fragments can become unguided missiles. You won't see it coming!

[project5k]

both are valid points, and i agree, but an estop, weather tied to software or directly to the drives, is still better than no estop. its better than fumbling with a mouse in a panic trying to stop the thing... (yes i made that mistake and learned a lesson)

my one saving grace in that situation was that the way i built my driver box, and where it sits in relation to where i am when i'm running the machine, makes it very easy to kill all the power.