spindle problems

[hofer]

I recently bought a second hand feeler ftc280 lathe. The spindle makes me troubles. If I switch from automatic mode to edit, the spindle turns backward. Then suddenly it started, if it runs above 1500 RPM when an M05 is commanded the spindle slows down rapid to about 200 RPM, from there it runs out without brake. Only when it stands, about 15 seconds later the nc-program continues.

Somebody ever experienced this or something similar before?

Your help is greatly appreciated

[HuFlungDung]

I'm sorry, I'm having trouble understanding exactly what you've described.

My question would be, what kind of cnc control does this machine have? Does it involve PLC ladder logic? If so, it sounds as though something has been corrupted in the PLC ladder, or else, it never was right to begin with.

Part of the problem involving a rapid slowdown, then coasting for 15 seconds would be considered "normal", except that its not ideal. The spindle drive parameters are incorrectly set, the deceleration time is too short, so the spindle drive does not have enough time to absorb the energy required to stop the spindle. The drive then "cuts out" before the spindle has stopped, so now it has to coast. The PLC ladder logic watches for a very low or zero speed signal from the spindle drive, before it then allows further execution of the nc program.

[Al_The_Man]

Like Hu says it would be an advantage to know what controller you have, What I would also do is if the Spindle controller has a +-10dc analogue signal, see what is happening to that when you switch to MDI, if the spindle is supposed to stop at that point, either the control is outputting a reverse analogue signal or, if the control does in fact output zero then it may be offsets in the drive, causing a run condition when zero is input, these drives can usually be trouble shot by disconnecting the analogue input, at this point the drive should stop, You can test the drive by disconnecting the analogue input and rigging up a 0-9vdc battery and potentiometer for signal and wire it to the analogue input, you can also use this to tune the drive if you have to.
Al

[hofer]

It's a fanuc 0t controller. What you said Hu, it's "normal", makes sense. But it happend all of a sudden, before the drive always slowed down "rapid" to almost standstill. Also the switch to mdi during automatic mode causes the spindle to run backward.

Could it possibly be that some cooling water got onto the break and it's not breaking strong enough anymore?

[Al_The_Man]

Is the Spindle control/motor Fanuc or other make? Do you have a spindle stop button? and if so does it stop the spindle when it reverses in MDI?
If you have the right bit set on the '0', you can display the ladder and this may help in trouble shooting, if you have a print out of the ladder with functions etc, you can go to the spindle output and see if it is activated, Spindle braking is usually done electronically.
Al