[Mimas]

Hi All,

I have a Hitachi CNC with Fanuc 6M. When starting Spindle, a LED comes on and "Overload" is displayed on the Spindle display board and my machine hangs. I was wondering if anybody can tell me what is creating this error. I also get this error even when going from one RPM to another (lets say when going 2000 to 1500).

[planar39]

im only a machinist(20 years), if you have a maintenance man, have him look into your variable speed controller, (you may have gear changes instead i dont know) if maint cant identify, call a service person.
its likely a board has gone bad

just my 2 cents

[debco99]

First thing is take the belts off if there are any, run the motor if it seems to run ok rotate the spindle by hand to ensure there isn't any binding.

You need to isolate the motor from the machine if it still does it I would start looking for another motor.

The fact that it runs at all is a pretty good indication the drive may be ok.

The reason it does it on rpm changes is the motor draws more current when slowing or speeding up.

Good Luck

[Dan Fritz]

You probably have a 3-phase full-wave DC servo amplifier on a machine of this vintage. If so, there is an overload sensor on the DC lines going to the motor. If the motor has lots of carbon dust inside (from worn brushes), or if there is an unusual load on the motor, you'll get an overload. Also, if any coolant has gotten inside the motor, that would make a mess and could short out the windings.

I'd check to see if you can rotate the motor easily by hand first. A bad bearing, a spindle brake that's not releasing, or a dirty motor are the most likely causes for this.

If you have a gearbox, check the lube level. Most smaller machining centers have a belt drive to the spindle, and some have a 2-speed clutch with 2 sets of pulleys and 2 belts. A leaking air valve can try to engage both clutches at once, making an effective brake.