[stevo1]

Hey guys I need some help.

I have a Monarch VMC with a Fanuc 15MF model B control. Last night they were running a part taking a heavy cut and the machine kicked out. They Zero Returned the machine. Every Axis homes fine except the table rotarty axis. It alarms out with PS200 PUlSE CODER INVALID ZERO RETURN ERROR.

The description says that the grid position could not be obtained because no one-revolution signal was applied before leaving deceleration dog in grid zero return using a digital position detector.

Any ideas? Would grid shifting the machine clear the problem? Or is it something like home has to be refound?

Stevo

[molland]

how badly did it give up. i had a problem on a lathe turret encoder after an ex employee hit the chuck hard, really hard. as a result, the encoder took such a shock that it was no longer able to read. we didn't replace the encoder, we switched to using a ring with 12 proxy switches, 1 for each station. i think you first need to check the diagnostic status of the encoder and its pulses. i dont know what to look for on your particular m/c, but thats definatly where i'd start, also is there a proxy or limit switch to say "your nearly home, slow down and seek" somewhere in the mechanics of it all, like you get on all axis x,y,z. that could've moved

[Al_The_Man]

I remember having this error when setting up a 15TT once, IIRC it was something to do with the motor rate when it leaves the dog searching for the marker.
Al.

[stevo1]

Molland,
I was not here but when it happened the operator called me and said that it was cutting when it happened. He was facemilling an uneven part taking off about .02" and when it got to a high spot it was removing about .1" and kicked out on him.

Al,
Should I look at the feedrate off the decel switches? I would not think it is a parameter issue as they shouldn't change. Is there a way to slowdown the rate it is coming off the marker?

I read some other posts that was somewhat related to this and it talked about the motor not being able to reach the 1/4 or 1/2 revolution after it comes off the dog. I was a bit lost trying to follow the diagnosis.

Stevo

[CHAD LAWSON]

ON THIS STILE OF HOMING USUALLY YOU WILL HAVE TO MOVE THE AXIS ONE PULSE OFF THE HOME POSITION OR ONE PITCH OF THE SCREW BUT SINCE IT IS A ROTARY TABLE YOU DONT KNOW HOW FAR ONE REVELUTION OF THE WORM SHAFT IS. MOST ROTARY TABLE USE A PROX SWITCH RATHER THAN A MECHANICAL LIMIT SWITCH. I WOULD ONE VERIFY THE SWITCH IS WORKING ALSO NOTING WHETHER IT TURNS OFF SLOWLY OR NOT. SOMETIMES THEY USE A PIN THAT THE PROX WILL READ OFF OF AND IF THERE IS ANY HESITATION COMING OF THE DECEL SWITCH YOUR ENCODER WILL ROTATE RIGHT PAST THE PULSE MARKER. THAT BEING SAID IF YOU GO PAST THE FIRST MARKER AFTER THE SWITCH THE MACHINE WILL NOT BE HAPPY. I WOULD TRY A GRID SHIFT SIMPLY TO SEE IF THE PROBLEM GOES AWAY AND TO ME THIS WOULD RULE OUT THE ENCODER. I SEE THIS A LOT ON OLDER MACHINES USING ROLLER SWITCHES. IF YOU HAVE A O SCOPE I WOULD DIFINETLY CHECK THE WIRES FOR THE PULSE MARKER TO SEE IF YOU ARE GETTING A READING. THE MAINTENANCE MANUAL SHOULD GIVE YOU A BREAK DOWN ON THE WIRES.

[samuel196803]

kitamura bridgecenter 8 .... has a PS 200 Pulse coader Invalid Zero return on the X-axis... when it go to home ... it goes to the switck ... slows down then goes to the secound switch and over travles ....machine shuts down with error....can u help????

[stevo1]

Samuel,

I have responded to your thread over in the PM website CNC forum. You also posted the same question twice over there. Below was my response at that forum. Also this thread is almost 2yrs old. Probably better off starting a new thread.

Did this all of a sudden start happening? Or did something happen with the machine?

A few things it could be. The machine is not seeing the marker in the pulse coder. You will need to put a scope on the encoder to see if the encoder is bad.

If something happened to the machine like a crash or replacement of a motor then you may have to do a gridshift. If the switch is too close to the marker on the encoder you can have the same problem.

What kind of control is on your machine?

Stevo

[samuel196803]

sorry 4 that.... but it has a Fanuc 11... and as far as i know.... nothing has happen to tha machine....but when i looked at the encoader it look like its the origanial... also troubleshooted the wires from it and i have continunity...(there good) drive board is good also....

[stevo1]

If nothing happend to the machine then it would lead me to think that the encoder went bad. If you have a scope you can check for the marker on the encoder to see if it is working properly.

Stevo

[hitachibos]

Both of you Stevo and Samuel,

find your grid shift parameters and write down thier values then change them by half 1/2 power off the control and power back on. see if your axis zero return.

If they do you can leave them like thet but all your zeros and offsets will need to be re-done

[stevo1]

find your grid shift parameters and write down thier values then change them by half 1/2

What if they are 0? Should he change them by half of zero??

I agree if he does not have a scope then this is worth a try. However considering nothing has happened to the machine then there would be no reason that the grid had shifted causing him to not be able to zero return. If this had been happening intermittingly then I would assume yes grid shift because the marker is too close to the switch.

Stevo

[hitachibos]

Stevo

what i have seen is most of the zero return switches are mechanical in nature. they get depressed as a angled trip dog goes by them. when the switches wear they need to be pushed in a little deeper meaning they travel further up this ramp on the front side of the dog. now when they trip and start counting the gridshift amount the machine will hit the overtravel switch before it reaches grid shift amount.

i hope i explaind that well enough .

[Al_The_Man]

Trip the home limit manually well before the O.T. limit, if it still errors out then could well be the Z marker, when checking, make sure to observe both Z & /Z.
Al.

[samuel196803]

Thanks... i will look into both... i will respond to what i find.... Thanks

[stevo1]

I know exactly what you are saying. I was just being sarcastic

My experience with the encoders and homing positions has been if it is working 1 day and the next it stopped all together it is not typically something wearing out like a switch. I was just suggesting that it may be most probable that the encoder went out. You could very well be right as well.

Stevo