Need Help!- TOOL CHANGER ON VMC NOT WORKING PROPERLY

[prash]

Hi, All.
Good day and greetings to all.
Basically I am in repair of CNC sheet metal machines ( press brake,turret punch press,Shearing ).
Currently I am attending a Chinese VMC with a Fanuc Oi mate .
The tool changer takes tool in absurd manner.
i.e. (for example) if we call tool no.6,it will get anything other than 6.
And if we try (say) 10 times for one particular tool;it will bring different tool every time but not the required one.
The seven segment display on Fanuc shows correct number ( i.e '6' if we call tool no. 6) but actually the no. of tool which is selected is different - other than 6.
In summery:there is no logical pattern in the error itself. It is quite random.

Thanking you all for a sure help coming from you folks.
Prash. psbhavsar@rediffmail.com

[Dave2962]

When you power up and reference the machine, the tool changer should rotate around and pick up tool 1 (when things are working properly). The way it finds tool 1 is usually a proximity switch in the tool changer that reads something on the tool carousel. There are usually 2 of these swithches. One picks up number 1 and the other one counts positions as the toolchanger rotates. It sounds like you have a problem with these. You may have a bad switch or they may just be dirty.

Dave

[prash]

Thanks Dave,
Actually it has got three proximity switches. One for reference and other 2 are for rotation sensing (cw or ccw )and counting.All of them are OK when checked manually.
In all there is no electronic problem.In fact during reference the turret does not rotate.I think the tool changer must take a reference.And because it is not taking reference;I believe that there might be an option in parameters for tool changer to take reference or not. Kindly let me know if such option is there.
THANKS FOR THE SUPPORT.
Prashant Bhavsar.

[Dave2962]

When you say the switches are ok when checked manually, what do you mean? Are you saying the light on the switch comes on if you manually make the switch? This may not always mean it is working. The light may come on but the signal may not be getting to the control. I do not have experience with the control you have, but I think there should be a diagnostics page that will show the condition of the switches. Usually a number that changes from 0 to 1 as the switch is made.

Dave

[prash]

THANKS DAVE,
You pointed the right thing.But here not only the LEDs on proximities glow ;I get signals in the panel also.Thus the cables of the sensors are also OK.
But I should try DIAGNOSTICS.I think your this suggestion will work.
But still I ask : Does the parameters of turret have an option for not taking the reference ?

[Dave2962]

I would not think there would be a parameter to tell it not to reference the tool changer. Are you saying that when you power up the machine and reference it, the tool changer does not try to index to tool 1? Does it move at all?

Dave

[prash]

Thanks Dave for taking interest.The programmer came and inform that it was a random tool selection program and you have to remember which tool you are putting in which pocket:the machine remembers tool positions.I do not know much of programing side of VMCs and my role was to remove short in 24v line for sensor supply.In fact it was a question of making just a program.
Any ways the machine works properly.
THANKING YOU AGAIN.
Prash.