I've got an old Fanuc AC Spindle drive A06B-6044 on a Fanuc 6M controlled machine. The spindle motor is a Fanuc 3.
I can't figure out why this machine has low spindle "power" compared to it's sister machine sitting right next to it. It's been this way for the 2 years I've owned it, but lately I've been using it more and more and noticed this is a problem and not just the way the machine was made. For instance, the load meter stays under 10% all the way up until just over 4,000 RPM, Then as it gets faster RPM the load gets higher. At max 5,000 RPM the load meter creeps up to about 75%. On identical cuts from each machine, this machine is always about twice the load at the spindle compared to it's sister machine. Lately when the sister machine spins up it's spindle, this machine will alarm out because of excessive speed deviation. Basically the spindle has a hard time keeping up speed when the voltage in the shop dips a bit from the sister machine spinning up it's spindle. I've tuned up the logic top board for the encoder feedback signals to be the proper square wave height and offsets, so I don't think it's a logic issue. It seems to be related to power.
Also when the sister machine spins up the spindle it can get up to 150% load while accelerating. This machine pegs the meter at 200% while accelerating. I thought it was just the load meters themselves being different, but you can hear this machine bog right down when it's doing a medium heavy cut, where the sister machine performs the same cut with ease.
I tested the amperage on each leg going to the motor. The three wires are within 1 ampre of each other, this is consistent with both machines. This happens at all RPM speeds, slow or fast. Does this indicate anything?
I've just started reading about replacing transistors and capacitors in the Spindle Drive which seems easy enough. But I'm not sure if the problem is that, or the motor windings, or something else. I've checked all the fuses that I can find in the drive and they are all good. I also checked the 220V vs 200V switch.
I'm about to swap the entire spindle drive from one machine to the other to see if the problem moves. What do you think is causing the low power at the spindle? Anyone run into this issue before? Thanks for your help in figuring this out.
Benjamin
Barch Designs
877-201-9771