What size stepper motor do I-need.

[IanParkin]

looking at zapps site I cant see any kits of parts but if i put together
4 dm856 drivers 4 nema 23 3 nm motors and one plc6x BOB and a 68v 6amp power supply
its £632 ish

Cnc4you's kit of parts is 356 plus vat 427 ish thats this kit ...Nema23 Stepper Motor Kit 4Nm x 4 Axis

will I notice any major difference with either of those over my cheapy ebay special ?

[Clive S]

I was looking at cnc4you's site but his drivers are only up to 50v with a 36 v power supply
Ian

Cnc4you is the best place to buy the steppers 3.1nm low inductance that I know of. But not the drivers Ebay is your friend for them like this one :- Leadshine AM882 Digital Stepper Motor Drive 80VDC 0 1A 8 2A Protect Function | eBay although I think there is a newer model you might find a better price as well. ..Clive

[JAZZCNC]

Don't go with the kits has they tend to be under spec'd on the PSU or have lower spec drives etc. You don't really save anything buying kits anyway if you shop around and to be honest if you build your own PSU you'll save more money.

Ian Check your PM's.

[tzar]

The calculations are contained in a Excel spreadsheet in the attached zip file

Thank you very much for this! But I have question.
For example I have 2 screws for X axis and 2 motors as a result. How I should make calculations in this case? I just need to double "Holding Torque", "Detent Torque" and "Rotor Inertia"?

[CNC Visions]

Thank you very much for a very informative explanation on motor selection.
I'm upgrading an older machine that had two motors driving X axis gantry. How do I calculate the motor size with two motors on the same axis? Is it a simple as dividing by 2?
Gecko recommends a 40% increase in motor size from base calculations, do you agree?
Thanks again
Mike

[Boyan Silyavski]

Thank you very much for a very informative explanation on motor selection.
I'm upgrading an older machine that had two motors driving X axis gantry. How do I calculate the motor size with two motors on the same axis? Is it a simple as dividing by 2?
Gecko recommends a 40% increase in motor size from base calculations, do you agree?
Thanks again
Mike

Not so simple. First you need to know the moving mass. Then the desired speed and acceleration. Then you decide the motors and the ratios. Then you check if your BOB can cope with that. Then you check what your resolution will be. Some back and forth between all that and a final decision. At least that's my logic.

[Clive S]

Then you check if your BOB can cope with that.

Do you mean the drivers?.
Mike But as Silyavaki has said there is more to it. How about posting some pics of the machine for a better answer. ..Clive

[CNC Visions]

I did the calculation, 670 oz-in/4.6 NM is required to move the axis with one motor. I would normally add +30% for efficiency loss and use a motor in the 850/6 range. With all that, I have a pair of NEMA 34 frame motors that are 420/3. Will I be ok with these or should I go with something bigger? I'm sure that a frame size increase to 34 will slow down my Rapids.
My drives are Gecko 203V, I have several power supplies ranging from 36 to 70 volts available. I upgraded to a Ethernet Smooth Stepper with a high end BOB so I should be able to handle most anything.
Thanks again for your help.
Mike

[Clive S]

Well are you using ball screws, pitch, size, direct drive, etc etc. Without full info nobody will be able to answer you. I take it you don't want to post any pics . Generally nema 23 are more than enough running at about 70V. ..Clive

[CNC Visions]

Ball Screws, direct drive, .5"/rev, 48"X48" table, 2.2 KW water cooled spindle with 10" of travel. The machine is totally in pieces but I will post pictures as it goes back together. I'm replacing the rails and bearings so most of the machine is in tote boxes or stacked in a corner.