Check out my motor specifications please

rdsmith24

Well,
I ordered before I looked closely at the specifications on my dual Z leadscrew motors (I concentrated on the current)

"Avoid motors with rated voltage (or product of rated current and phase resistance) > 4V or inductance > 4mH."

Mine have the following characteristics.
Model 17HS6401
Step Angle 1.8
Rated Voltage 5.1vdc
Rated Current 1.7A
Phase Resistance 3ohms
Phase Inductance 6.2mH
Holding Torque 7.2 Kg/cm

I'll be running a 24vdc power supply.

They seem to run fine on the bench under no load….should I sell/scrap them and buy new ones?

Thanks

elmoret

That's fine, especially for Z and with 24v.

dc42

Keep them. The inductance is a little high and could limit the speed if you run them both in series, but you are using 24V and you don't need high speed on the Z axis anyway. If you have only 1 extruder then you also have the option of driving one from the Z output and the other from the E1 output.

You can work out the maximum speed from https://duet3d.com/wiki/Choosing_stepper_motors#How_to_work_out_the_power_supply_voltage_you_need. I have put a spreadsheet to calculate the speeds at which torque starts to drop of at https://www.dropbox.com/s/5z66rgjc8gptn5o/StepperMotor.ods?dl=1.

rdsmith24

Thanks for the advise….I am connecting them to the Z motor connections ZA and ZB, I assume that is in series?

Only one extruder planed so if putting both motors through one driver is a problem I can resort to using E1. If I use this option, how do I make sure they work in tandem.

Thanks for a wonderful board (DuetEthernet) and the support....thats the main reason I went with this board.

dc42

If you want to drive the second Z motor from the E1 driver, use this line in config.g:

M584 X0 Y1 Z2:4 E3

Another advantage of driving them separately is that if you have a Z probe, you can auto level them - see https://duet3d.com/wiki/Bed_levelling_using_multiple_independent_Z_motors.

Martin_S

I've just discovered this datasheet, thanks David.
One thing I don't understand, the cell "Actual current (peak per phase)", this is the value that will be set in the config.g right?

If so, then why if you decrease the current, you can achieve higher maximum speeds? I tought that increasing the current gives you more torque. I mean, this cell "Speed at which torque starts to drop (mm/sec), low slip angle" gets higher values with a low current.

I'm a bit confused here. Yeap!
(sorry if I'm not explaing myself properly, hope it makes sense what I'm asking)

dc42

You can't really get higher speeds by reducing the current, it's just that at higher current settings the maximum speed you can get while maintaining that current is lower. For example, suppose you can maintain torque up to 100mm/sec speed when you use 1A current. If you reduce current to 0.5A then you will only get half the torque, but that torque will be maintained up to 200mm/sec. Had you left the current at 1A, the available torque at 200mm/sec would be much the same as at 0.5A.

Martin_S

Perfect, that makes sense. Thanks!