[Justintro8487]

I have a 97 hurco Hawk 5 with ultimax ii control. The machine runs 3 baldor dc servos rated at 40 in-lb holding torque with a max rpm up 4500. Drives are made from servo dynamics. I’m looking into upgrading all the electronics on this mill to possibly a centroid set up and I’m trying to decide on whether or not to change to ac servo and drives or keep the dc Motors and drives. The motors I have now which are the original could probably use being rebuilt which I have priced and is not exactly cheap. The drives are getting old and I have already had to replace one. Any affordable options out there? Does anybody have any experience with the 1.8kw ac servo and drives sold on ebay? Anyways suggestions and idea are welcome!

[Justintro8487]

I also wanted to include some pictures of the machine just to give an idea of what i'm working with.
Attachment 429848

[Jim Dawson]

I kind of like the old SD drives, I have them on one of my machines. But there are options. I don't know about the 1.8KW servos on EBay, but a better choice might be the ones from DMM Technologies. https://store.dmm-tech.com/ Not sure how the price compares but their after sales support is fantastic. I have 4 of their 1.8KW units on my lathe, and have installed them on another machine build. Have had very good luck with them, and I know others have also.

1.8KW might be a bit of overkill, a 1KW would be about a direct replacement for your existing motors.

[Justintro8487]

thanks for reply, as far as AC servo motors go, how do you compare a.c to d.c as far as sizing? Do you just go off of holding torque, inertia, rpm etc... or is there something else to consider when going to AC? Are DC motors still being used in new machines? I know the mazaks we run at work are running A.C. servos and they are all fairly new machines. Do A.C. drives still need to be tuned to motors? I know with my current D.C. drives and motors I have just tried to tune them by ear and feel going off of a basic starting point from manuals I have found online but not perfect obviously without the proper equipment and know how.

[Jim Dawson]

Servo motors, both AC and DC are rated by torque and rated RPM. Unlike a stepper motor torque curve which drops off very fast as the RPM increases, servo motors have a much flatter torque curve from 0 to the rated RPM, almost flat through the operating range.

I am not aware of any new machines using DC servos, AC servos are the norm today.

Yes, AC servos need to be tuned, but many have auto tuning software. Even with the autotuning function, they still normally require a bit of manual tweaking.

Tuning by ear and feel is the way I do it also. I need to adjust mine one of these days.

[Sencillo]

Where can I find manuals for this machine?

[cncmakers001]

I also wanted to include some pictures of the machine just to give an idea of what i'm working with.
Attachment 429848

From the photos you sent, our experience for the similar size machine
The X and Y axes could use 6Nm, 2500rpm AC servo motor
The Z axis could use 10Nm, 2500rpm AC servo motor with brake
But I am not sure the spindle motor, does it need to be replaced too? what is the required motor power for it? and need to note the flange size for installation.