Fanuc Repair Gurus - Brain teaser of the week... 21iT tale of woe..

[Milacron]

Certainly sounds as if.

An 'interface' is a general concept first, specific function second, some form of hardware eventually, but not necessarily SEVERABLE hardware at even now fairly old levels of integration.

Could be a row of buffers, level-shifters, IR fibre to CMOS levels on the edge of a multi-function PCB or even a corner of the die in a multi-function single IC. Or even just an ignorant DIP connector as 'meeting point' AKA interface.

Further, the designer(s) of any of several general-purpose modules would not know in advance the nomenclature of all possible future modules it might one day be used with. 'General' term would have had to serve. More especially if (s)he wasn't even an in-house Fanuc staffer.

A good Tech Writer would have cleaned that up for each bespoke manual to reduce service costs and

Bill

Well, I've looked at the boards that might be the mysterious servo interface module and damned if I still don't know for sure what I'm looking at.

Candidates include -
A20B-2002-047
A20B-2002-052
and the board in the CPU box that the fiber optic cable connects to, which I can't make out a part number on.... But it is interesting that rather than "axis card" as it is known in the manual, on the actual board it is labeled "servo card". Still the all important word, INTERFACE, eludes me...but I am cozying up to the "servo card" as the prime candidate for now.

 

[Ox]

Well, I know that HMI was still used in the 90's.
Not sure that I have seen it refered to as anytihng but an "interface" or "opertaint panel" since then?


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Think Snow Eh!
Ox

 

[metaltech]

Don,

The i controls in my customers' base have been so reliable that I've never needed to take apart any of that stuff. I'm ignorant on what's inside. (I'm assuming you have the whole compact control right behind the display.) But, I might be able to answer one of your questions that possibly has relevance.

I was just troubleshooting a 16TTA (not an i model), (just a 5-axis, dual post lathe). On the MAIN board, in the yellow CNC rack with a power supply unit to the right, there are modules mounted. These are very similar to a DIMM memory module in a PC, and clip in the same way. There are AXIS CONTROL modules, and there are SERVO INTERFACE modules. The MAIN board has these words printed in yellow next to the slots the modules mount into. I've had a couple of occasions when one failed in some manner, and by exchanging the position of like-part-numbered modules, seeing which axis the alarm then moved to (on the display) narrowed down the culpret. I believe the base AXIS CONTROL module can support 1 or 2 axes, depending on what complement of chips are mounted. But, I've often seen 3-axis machines that had a pair of 2-axis modules, making an exchange possible. Note that the SRAM memory module for params, programs, everything is also on the MAIN. There is a supercap to hold the memory, since the battery itself is part of the power supply unit. As such, I like to do what I need to do and get the MAIN back into its slot in a few minutes, just to be conservative. Don't know how that applies to your situation.

Now, I realize the above (much larger) architecture is not what you're dealing with, but it may have a similar arrangement with the modules. I know that the 16/18/21 Maintenance Manual shows the MAIN board with a layout of all the modules. It also has tables of all the modules that can be fitted, and their part numbers. I think the last time I bought an AXIS CONTROL module, it was about $400 exchange from TIE.

 

[Milacron]

Just got off the phone with a tech at Fanuc. I now know the "servo card" is indeed the "servo interface module". The depressing part is the failure rate on those cards... .001%...heck, he may have even said .0001%...can't remember now...whatever it was, it sounds to me like a bad servo card is highly unlikely. And yet if it's not that, what the hell is it at this point ??

Excess RF from the Phase Perfect is still a slight possibility, but the tech had never head of excess RF being an issue except in cases where the cable insulation had deterioated from coolant, etc.

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(on edit) Called back with some more questions, got another tech this time. He also thinks the servo card is the most likely culprit in this case... reseating it might help. However the new depressing possibility is if the card is not bad, the motherboard could be the culprit !

As an aside, he confirmed that the last alarm numbers are always at the top of the list.

 

[Ox]

Well - I had to change one of those daughter boards last summer.
They doo go out.

I think it was more than $400, but I don't recall for sure.


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Think Snow Eh!
Ox

 

[Milacron]

Well - I had to change one of those daughter boards last summer.
They doo go out.

Do any of the suppliers of those offer return possibilities if the new card doesn't fix the problem ? I don't mind spending some money for a new card or board but my nightmare is spending it for nothing.

In all my decades of repairing CNC machines I've only had to buy one board (that I can recall anyway) Was on a Charmilles EDM where the morons soldered the backup battery to the board, which years later leaked and ruined internal traces. (although if that were to happen today I think I could even fix that myself now) I did have to send out a spindle drive once for repair. (actually twice since the first shop didn't actually repair it...another story...) Oh and there was an ancient Anilam M that needed new boards but I had an identical sister ship control to swipe those from.

 

[John Welden]

Fanuc is so great.

 

[Milacron]

Fanuc is so great.

Where is that rabbit with a pancake on his head when I need him ?

 

[WILLEO6709]

how many of the same part number board are present? If there is 2, swap them around and see if it follows the card or the axis

 

[Ox]

..and if it is like most such goods, was probably less-costly to buy new than the published flat-rate board-repair fee of any of the many independent service outfits.

Aside from the service folks having to amortize test gear and technoid training costs, keep the bench on standby in slow times, they have to USE the gear and skills to find the fault, know where to get not-always-common components to repair it.

Costs for mass-produced-new PCB's OTOH can be rough estimated with fair accuracy simply by knowing their surface-area. All the brain work was done once, the rest is a stored program to spec component tapes, QC them on arrival, populate the board, test it. All of that done to an even higher degree of functionality and automation than the CNC devices those boards will eventually control.

Troublesome? Soon as the volume is proven, cram more functionality into fewer and fewer bespoke IC's, reduce the board real-estate. Rinse, repeat.

We'll know it has reached end-of-days when code is fed to a 'networked' CNC machining centre, it parses it, 'sesses out the market at the moment, sez "F**k you that won't sell!" ...then goes off on its own to cut deals, order tooling and stock, and make some other part that WILL sell. AR-15 variants in their infinite flavours, for example..

.. and puts the proceeds into its OWN bank account..

Don't ever put blind faith and trust into a machine smart enough to know where ITS goolies are with greater precision than you know where YOURS are.



Bill

I think at that point - a pr of sidecuts will have more street value than an AR.


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Think Snow Eh!
Ox

 

[Milacron]

Unless I've forgotten (again) ALL axes are (being seen as..) AWOL.

Yep. One remote possibility....the two servo amp units are daisy chained together in some respects....FO (fiber optic) for example loops between units and then one FO runs to CPU. So one imagines a senario where if one servo unit is down it effects communication from the other one as well. I mentioned this to Fanuc Tech 1 and his says maybe. Fanuc Tech 2 says, nope. (no. 2 sounded a little more impressive)

 

[James Lederer]

This probably won't be helpful, as I have no Fanuc experience. I do have a Yaskawa 4-axis servo system that runs a digital communications link with daisy-chained servo amps. In my case the battery packs for the absolute encoders are located on the encoder cables. If I unplug an encoder cable, the system will recognize that absolute position data was lost and will throw an alarm on the amp at next power up until I run a function to reset the absolute encoder.

Maybe something similar is happening in your case? Is there a way to reset the encoder?

 

[Milacron]

This probably won't be helpful, as I have no Fanuc experience. I do have a Yaskawa 4-axis servo system that runs a digital communications link with daisy-chained servo amps. In my case the battery packs for the absolute encoders are located on the encoder cables. If I unplug an encoder cable, the system will recognize that absolute position data was lost and will throw an alarm on the amp at next power up until I run a function to reset the absolute encoder.

Maybe something similar is happening in your case? Is there a way to reset the encoder?

Yes, encoders need to be reset (error 300) due to low voltage on encoder backup batteries when I received the machine. However they are impossible to reset until I clear the 301 error. At first I thought like you that the 300 alarm might be causing the 301 alarm but after much tech talk and real world tests I now know that isn't the case. For all practical purposes my servos and encoders are dead (even thought they appear quite alive... servo/encoder leds on, fans running, etc)

 

[James Lederer]

Maybe I missed it in skimming over the thread, but have you charged up/replaced the batteries before you did the reset? Maybe it's a requirement to have charged encoder batteries before it will allow you to zero the axis.

 

[James Lederer]

Can't see any good reason to place an all-optical device on (whichever) board accepts TWO FO and onpasses ONE to the CPU, so I call foul on tech #2.

I he is correct, that board could be pulled out of its socket or otherwise fully de-powered and still onpass the signal from its mate.

I'm from Missouri on that point. Show me.



Bill

On my Yaskawa daisy chained setup, I can leave an amp fully unpowered and it will still pass the signal for the remaining amps.

 

[James Lederer]

I should clarify, my amps are separate self contained units. I can leave one unpowered at it's dedicated circuit breaker, and still have full function of the other amplifiers. They use the Mechatrolink II bus for communication between the amps and the PLC, it appears to simply be passed through the socket. I could see an optical link being different in that it might require a powered repeater to pass the signal.

 

[WILLEO6709]

do you have any alarms on the drives? the 9 segment led puts out number codes.... many times a simple explanation is inside the terminal cover.

 

[Ox]

Did you check the power comming accrost the top leads from the Power Supply?
Compare the two leads to each other and see if you get similar V and ohms.


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Think Snow Eh!
Ox

 

[WILLEO6709]

Fanuc is still a japanese product and sometimes instead of 230 vac in the cabinet they want 200 vac..... and at times that can throw devils in the works too...

 

[Milacron]

Maybe I missed it in skimming over the thread, but have you charged up/replaced the batteries before you did the reset? Maybe it's a requirement to have charged encoder batteries before it will allow you to zero the axis.

Yes, replaced batteries first thing.