Problem- Keep replacing 2008 Mazak QTN450-2 Spindle cooling fan motor

[eric14779]

We had a Spindle cooling fan overtemp alarm back last spring, Maintenance replaced it and all was well until this week when it did it again, The operator opened up the end of the machine and put a floor fan blowing on the Spindle cooling fan and continued running.... It seems to be when we are making heavier cuts that this happens.

Now the alarm is the Spindle cooling fan itself not the spindle, there is a thermal switch in the Spindle cooling fan motor that is tied to a input. We have plenty of air flow to cool the spindle.... everything seems normal no other high temps.... just the little Spindle cooling fan

Myself and the maintenance manager think that something weird must be going on... There is no way we should have to replace the Spindle cooling fan again...


Has anybody else had this issue? I am thinking a power quality issue (internally to the machine) or a magnetic field from the spindle affecting the Spindle cooling fan.

Mazak said last year that they have not seen many of these Spindle cooling fan go bad...

thanks

[fizzissist]

This does seem odd...
Not familiar with this machine, but first thing..Is the motor a 3phase? Have you checked to see that the legs are even under load as to voltage and current?

I think the problem is internal to the machine electrics too. Out of habit, I always check all the connectors back to the source, then start with the voltages.

Something else to look at is to make sure the motor is in fact what's spec'd for that machine and not accidentally underrated, and there's no surprise flow restrictions.

....and the ubiquitous sensor itself....

[eric14779]

Fizzissist,

thanks for your reply,

My continued research has found that this is a single phase PSC type motor on this cooling blower.

And now the capacitor is suspect, if it is bad, it can cause the symptoms that we are experiencing.

I just am surprised that this problem comes and goes, usually when the cap goes bad it stays bad....

oh well, we will replace with a new one and see what happens, we may replace the motor as well as it could be stressed and could cause a repeat problem.