[kewl_cat]

I just acquired a Pratt Whitney lathe with a 6T control on it. When I power it up the Machine alarm is lit on the operators panel. The operating manual says this is a problem on the machine side. I can use the jog button and the digital readout indicates motion while there is physically nothing happening. I am not new to working on CNC stuff but a total noob on a 6T. Any suggestions of what to check or things to do. I have wiring diagrams but no maintenance manual. Any suggestions appreciated.

[tc429]

sounds like 'machine lock' or 'program test' button is on, lamp may be burnt out... signal is called MLK in the signal list, most OEMs use similar naming on their schematics

[kewl_cat]

Yes the machine lock was on. Now I can jog the machine, home it, and enter other commands via the mdi. I cannot get the spindle to turn on. I can enter S500 and a M3 command and only the op stop light comes on. The way lube reservoir is full and it has full air pressure. The transformer on the spindle drive unit is not powered. It is getting power to the magnetic switch but it doesn't look like anything is siganlling the switch to turn on. Does anyone know what signals this switch to come on?

[yardbird1969]

I don't have any idea about the transformer issue. If it is that then maybe someone else can help. Way back when I was on 6T machines. while in manual mode there were just 3 buttons on the control panel CW, CCW, Stop and a dial to control RPM. In MDI (with the chuck clamped) you might have to call a gear range with a M41; or M42; then the mext line a G97 S500 M3;. You say your no stranger to NC so im pretty sure you already know this but since didn't know about the machine lock I figured I'd type this just in case you by chance you didn't. Good luck...


Brent

[Al_The_Man]

Did you check the O/L (over load) for tripped condition on the spindle contactor?
Al.

[Al_The_Man]

Did you check the O/L (over load) for tripped condition on the spindle contactor?
Al.

[kewl_cat]

The M41 did not change anything.
I just checked the overload on the spindle contactor and it is ok.
I checked the thermal switch on the DC motor and it is ok.
The spindle will not do anything either by the operators panel or the MDI. The only thing that shows anything is the spindle meter that reads that it is at 100%. Also when the machine is on it makes a high pitched whine when you rotate the spindle but absolutely no motion. This is a DC spindle unit with 2 Honda plugs so I am assuming this is a binary unit based on some previous reading here on the forum.
Does anyone have a manual and or schematics for this unit? It sure would help diagnose this thing if I understood how everything is supposed to work together.

One other thing. Based on some reading on the forum. Someone previously said that parameter 003 should be 00001000 for digital or 00010000 for analog drive unit. My parameter 003 is 00000000. I don't know if this info is correct for a 6T but I thought I would throw that out there. I did change the parameter but nothing happened.

[kewl_cat]

Anyone have any recommendations on where to send a board to get checked/repaired? I would like to send out my spindle pcb to get checked by someone trustworthy...

[tc429]

if it comes to that, tennessee industrial electronics is my favorite, guessing they *may* want the whole drive for testing...I got a feeling you wont need/want to ship that drive though, lock it out, pull the motor covers, check the brushes/holders(sometimes the fans will build like a stalagtite of dirt on the brushes, after setting they solidify/short out). I dont even recall on dc if they had a dc tach or a pulse generator- pulse generators an fanucs are notorious for dying in storage- the little magnet simply demags over time and the sensor has to be swapped...

checkout your brushes/feedback, and if you cant find issue, I think you should call and lv a msg at TIE for Tim(615 449 2848 if i remember right- been a while), describe the issue completely, if he cant find likely culprits in his notes, he can ask Bobby...IMO Bobby down there knows more about fanuc than fanuc, and they are really great people in my book.

[kewl_cat]

The motor brushes looked very good. This was a low mileage machine that came out of a school.
I talked to TIE today and they will only do an exchange on my board. $4754.00 if mine is is rebuildable and $8060 if it is not. $282 to test it.

[tc429]

ouch.

I cant remember drive numbers like some of these guys, what part number is your drive? we *might* still have some old DC stuff in our storage area, could ask the boss if he wants to part with any of it...

seriously, you might consider a AC motor/drive from a old machine...aside from the mag sensors dying, they are very reliable compared to DC. we had some new daewoos back in the 80s that had so much warranty trouble with the dc spindles, they actually changed to ac under warranty, never had any other failures except the mag sensors every 7~8 years.

just for the heck of it, power off let it bleed down a while, pull the top board off and check the transistors(scrs if REAL old) for shorts, swollen capacitors, cracked or loose big white ceramic current feedback resistors, simple stuff like that... i remember one series of drives, often one of the current shunt resistors would have a leg crack off from years of machine vibration. often when it would open/arc it would take out a transistor module...early 6066 servo amps suffered molten solder causing resistors to fall out if overheated, blowing the 6pack transistors...hated those drives- now we are running out of others and going to old robot 6066s for some machine servo drives, we'll see how they work out. some of our zero controls are probably on their 5th or 6th rebuild/rewire/retrofit... bet some will still be running in another 20 years...great little controls.

anyways, newer ac stuff, half the time the IGBT module just fails (often the little optocouplers are too old/misfiring once takes them out), fixed many (like 100) with just a spare stripped drive or used 50 dollar ebay IGBT, maybe new optocouplers... the old ac spindles often used a bank of darlington pair transistor modules, they are cheap, the FETS on the firing card often blew with them...often just a ohm meter for comparisons can lead even a idiot like me to a simple failure/fix...if by chance you swap a darlington pair module (5 or 6 inline screws), BE CERTAIN not to put it in upside down...saw a guy do it once(no, wasnt me) and when he booted it up, it exploded quite impressively, the firing card looked pregnant, like a balloon after the thing blew...big DC power in there, be careful

[kewl_cat]

The drive unit is A06B 6041 H105
The PCB is A20B 0008 0375/02

Thanks, that gives me some stuff to check. I will keep you posted.

[kewl_cat]

I checked all the above and have not found anything.
I was wondering how much of a project it would be to convert this machine to an AC spindle? I have another machine with a 6T control on it with an AC spindle. Should I try to go Fanuc motor and drive route or some sort of aftermarket drive like an Hitachi VFD? Any ideas or suggestions of a best route to take?

[tc429]

old hitachi and fuji drives you couldnt give me...just my opinion... the fanuc ac were generally pretty reliable except for the stupid magnet in the mag sensor going dead over time...been thru hundreds of them over the last 25-30 yrs, ALL fail same way- weak magnet... think they shoulda had a 'keeper' in the device, or maybe some eddy current shielding. have seen a similar sensor on a mits and a okuma do the same thing (weak signals- a screwdriver will barely stick to it, new ones are strong as heck for ~8 yrs... most seemed to die in storage, which I thought was odd

[crasher455]

When I first purchased my 1982 Hitachi Seiki Fanuc 3TF It did not come with a set of manuals and I had exactly the same problem as you and thought something was wrong with the machine spindle

Turns out it is required that you specify four things in the program or in MDI mode before it will let you start the spindle at all even in jog mode.

First, the spindle must be put into gear with either M40 for low range or M41 for High range.

Second, the hydraulic tail stock's position must be programed M25 for extend, M26 for retract.

Third, the spindle max speed or sometimes refereed to as clamping speed must be set G50 S2000, This sets the maximum speed the spindle can turn during Constant surface speed mode.

Fourth, set the spindle rpm S1000 M03.

Also required on my machine for the spindle to start is that the chuck needs to be clamped and and the door closed or the door switch disabled.