Encoder at fault or not?

[Adee]

Hi
Sorry if this is not in the right forum group for my question, but seemed a good place to start.

I have a Emco vmc 100 with tool shop attachment (tool changer)
I am getting a error/fault with the the main drive motor for the spindle, And was wondering if it could be the main spindle encoder, do they degrade slowly or do they just died and stop working?

Symptoms:

Turn on m/c and leave for roughly 10-20 mins, before you can get spindle active in manual mode, and then only can you run at lowerish rpm until warmed up for about 5-10 mins.
Then the m/c would normally run fine for about 1-1.5 hours, then would start playing up and stopping/alarming out. the most comon alarm I get is related the the main drive unit and pulse corruption.

I have notice recently the the higher the rpm the spindle is run at the sooner the problems will occur.

Any info or help would be greatfully received, thank you.

Adee

[Al_The_Man]

Sounds more like a problem with the spindle drive, what kind of spindle is it? DC,AC 1ph 3ph?
The encoder is often only active on some functions, you could have a tach or pulse generator on the spindle motor itself which could cause some similar symptoms, but more info is needed on what you have.?
Al.

[Adee]

Hi thanks for getting back to me.
All I know about the spindle motor off the top of my head, is that its rated at 800 watts and is DC, not direct drive to tool spindle, but runs a toothed belt & pulley system.
It has 4 armture brushes and have been recently replaced.

What other info would be required?

kind regards

Adee

[Al_The_Man]

For spindles of that size, usually simple SCR DC drive is used, an maybe no tach.
So if you are sure the motor is OK, then probabally the drive has a problem.
Two simple thing to test roughly is to run the motor on a separate DC supply, two auto batteries in series should make it spin pretty good, and for the drive, if no feed back is used use a large wattage lamp in place of the motor, see if it can be varied in intensity.
Al.