Hi,

Here is the motor I am using-
[www.lulzbot.com]

and here are the exact specs-
[download.lulzbot.com]

I need to get some more of those, but I am not able to compare if I am looking at the correct one.

For example, is this ok-
[www.3despana.com]

or this-
[www.aliexpress.com]

If someone could point out, or explain in short what I need to compare. Since everyone shows specs in their own way

Thanks!

My humble opinion on this.

SY42STH47-1504A
Inductance too high (4.8mH) the motor's torque will quickly decrease with rotary speed (rpm).

17HS8401
The inductance is still not the lowest, but pretty acceptable (3.2mH). It's actualy what I choose for my machines, but for the last 10 motors I bought, 1 was not acceptable, it does not spin properly. So check well when you recieve your motors.

For lazy people : the lenght of the motor is linked with available torque, your required torque depends of the efforts the motor will hold. Then look at the inductance, the lower, the better.

The choice of the motor is the result of a calculation for a specific situation. I won't explain the calculation procedure here. A lot of manufacturers give stepper motors selection guides. (It's easy if you try). So all depends of the machine itself and of what is expected. My advice, don't ask for someone to do your shopping, ask for knowledge (or where to get it). Get some skills.

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Collective intelligence emerges when a group of people work together effectively. Prusa i3 Folger (A lot of the parts are wrong, boring !)

IMO either of those should be good. The lower inductance of the second one should allow slightly higher speeds, however the higher inductance of the first one is to some extent compensated for by the lower current it needs to provide the same torque. If you are aiming for really high speeds, you should be looking at using a 24V supply for the stepper drivers anyway.

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Large delta printer [miscsolutions.wordpress.com], E3D tool changer, Robotdigg SCARA printer, Crane Quad and Ormerod

Disclosure: I design Duet electronics and work on RepRapFirmware, [duet3d.com].