Denford Software & Machines

I have a triac pc , which i have had for many years ,and has been great .
on occasions it has missed steps on the x drive , which i have put down to too heavy cuts etc .
also when i bought the machine the x didnt work at all , which turned out to be the connector box on the back of the machine was full of coolant .and so was the stepper motor , (a good clean out and all was well ).
Now i am doing a standard repeat job ive done before with a 2mm cutter ( not big echh) . the job takes about 8 minutes , the machine when i came back to it had emergency stop up , having hit the hard end stop on the x drive.
some where along the programme it missed out steps , and the when told to go to home . it hit the end stop.
I the used the over ride button to back it off the stop to rehome it . but the drive buzzed (like moving ) but did not move, so i undid the motor mount to manually wind the table off the stop . while the motor was off i pressed the drive x button to check the motor . it buzzed but didnt rotate , so i spun the shaft , after 2/3 attempts it slowly started to rotate , and slowly built up speed . after about 20 seconds it stabilised and all seamed ok, so i put it all back and it works ok .
question is the motor shot ,and this is why it occasionally misses steps ?
if i need a new motor what is it .
peter.

It sounds more like a mechanical problem..something is tightening up and you've managed to free it temporarily by giving the motor a helping hand.
I'd look at the gib strips to see if they are loose, then remove the motor and try everything by hand - is the motor hard to spin or is the ballscrew pulley ?

Hi i've striped down the x drive and checked the table for tight points a have found none.
so i power up the triac , homed the machine and took of the stepper motor to check for power.
I did expect not to be able to turn the output shaft , while under power , but found no resistance .
i count spin it either way , no difference . and no change to the readings on the screen . so i pressed
X+ the motor went round , until i put my finger on it , very little torque . and the motor stopped ,but
the readings carried on changing ,but the shaft wobbled like something was going round and bent ,
so tried various things all did the same . it looks like the shaft has
come detached from the rotor . . I'll having the motor checked .
good ?? .
peter.

Are you sure it is not a bad connection or broken wire?

Try measureing the resistance of both pairs of wires goining to the stepper motor.

You should have around 2 ohms resistance when not connected to the drive,

hi ive checked the resistance of each coil and it measures about 2 ohms each so all looks well .
and i checked the connections for a broken wire , but found none . so
i changes the motor to a new one , which came from (Motion Control ltd , in Poole )
they took a look at the old motor provided a suitable replacement .
the wiring was a bit different though , ( 8 wires instead of 4, so put the coils in parallel).
and now its great better than its ever been . much more positive .
just for info . my machine uses Parker drive boards .
and i checked the resistance to keep the new motor load as close as i could to the old motor.
peter.