January 18, 2021

Replacing steppers for more torque options / Advice wanted

3 min read
Hello I’m looking to upgrade my machine to get more power onto my x and...

Hello I’m looking to upgrade my machine to get more power onto my x and y axis.

I already did a post about some 10A drivers, but did some more research on the steppers/servo/drivers and have some more questions.

At the moment i have an upgraded avid pro cnc with dual Z (7kw and 2.2kw spindle).
I mostly do cabinet work and when hitting 500ipm when cutting i feel like i’m running on the upper end of the stepper motors (x/y)ability.

I would like to upgrade the original stepper motors and did some research of different possibilities.

At the moment i have:
CRP8070 (leadshine DM870) drivers
960 OZ low inductance 2mh steppers running on a 48V power supply (wich is perfectly dimensioned for these steppers)
The belt reduction is 3.2/1
This translates to following numbers:
Ipm and motor RPM are about equal / this is the most used power/rpm band.

60 = 5NM torque
120 = 4,6
240 = 4
360 = 3,6
480 = 3
600 = 2,4
720 = 2
840 = 1.6

At the moment i see 3 possible options:

1 ) Stepper motors with higher torque
-Pro & cons:
If i go to 10 Amps models i need new drivers and a new power supply
I can gain some torque +20%
cheapest option, but not much less expensive than option 2 (easy servo steppers)
due to needing also a new psu unit.

2 ) Leadshine closed loop stepper Easy Servo High Voltage 3 phase
-easy servo motor es mh33480
-driver es-dh2306

-I do know that i do not need to expect too much form the closed loop system.
At best they will stop when there is an error
-The drivers are 230V and do not need an separate power supply
-The system has a good torque curve and can be fitted directly onto the belt reduction system i have
-They have 300 steps (1.2°) instead of the normal 200 steps (1.8°)

Things i don’t know any thing about:
-3 phase does instead of 2 phase
-They do have a high impedance, and i don’t know if this is a big problem in this situation vs the 2 phase low impedance
-This would double the amount of torque over the usable range 0 to 1000rpm . Only doubt i have is would my machine handle this well?

3 ) Servo System
-Are better than steppers
-Are more expensive
-Need an 110V power supply (230V standart supply here)

The main thing with the servo’s is i will need to replace the 3.2/1 belt reduction with a 1/10 gearbox to make it work.
Personally i’m happy with the belt drive and the accuracy of my system.
I’m a bit afraid of a gearbox setup due to price and maintenance. They wear out eventually and backlash is worse than a belt system?
Also there is less cushioning in the system, and with my light machine i think it’s best to keep it this way.

So at the moment i’m thinking to go for the closed loop high voltage system. Any thought on this system or other views are welcome.

There is some documentation attached for the system in use (avid) and the leadshine easy servo steppers

Keep safe & a happy year to come!
Adam

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