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  1. #1
    Join Date
    Oct 2007
    Posts
    179

    Nakamura-Tome TMC-2 Fanuc 3T

    Hi,
    I'm thinking of buying a Nakamura-Tome TMC-2 with Fanuc 3T(1982).
    Its like new and has an extended pc type key board too.(not sure what this is used for..)
    Does anybody know this machine and if its any good. I realise it will have Dc servos and I presume DC spindle motor too?
    What are the limitations with Fanuc 3T.. I imagine the memory space is only small by todays standards... otherwise i would imagine it works much like 6T with the same available G and M codes..?

    Thanks for any help guys..
    John.

  2. #2
    Join Date
    Jul 2007
    Posts
    60
    The Nak itself will be an excellent m/c - possibly a bit slow by todays m/c's but rigid and will turn with excellent results.

    but i don't fancy the 3T controller!!! - i never went back that far my self and started when 6T came out, which was 100% reliable i understand that 5T and earlier are somewhat..... quirky!

  3. #3
    Join Date
    Dec 2005
    Posts
    55
    Cnc-it,

    We have 4 Nakis here. I don't have much experience with the 3T control but you can't beat the machine.

    JK

  4. #4
    Join Date
    Oct 2007
    Posts
    179
    Thanks guys that's the info I was hoping to hear.

    Apparently it has a two speed gear drive too so should have reasonable torque!

    On the Fanuc side i read that the 3T came out at the same time as 6T and after 5T.

    It was meant to be a more affordable option to 6T and has Sram memory as opposed to bubble memory but uses the same 16 bit processor..

    Should be ok for the simple stuff I need to do

  5. #5
    Join Date
    Sep 2005
    Posts
    767
    You're right that the 3T has the same 8086 processor as the 6T. The 3T is very reliable, but it just doesn't have some of the optional features available on the 6T. If a simple, reliable control is what you're looking for, the 3T is it.

  6. #6
    Join Date
    Oct 2007
    Posts
    179
    Thanks Dan.

    Am I correct in saying that 3t can't be used with iductosyn scales either...? The one i'm looking at has a querty type keyboard so may have Fapt Turn ..?

    I have a spare 6T motherboard ...can I swap it with the 3T motherboard and swap the eproms /parameters etc too or am I way off base with this idea!!

    I think the 3T would be fine for what I need but thought i'de ask just out of interest!!

    John.

  7. #7
    Join Date
    Aug 2007
    Posts
    31
    Do you have fapt on the 3T ?

  8. #8
    Join Date
    Sep 2005
    Posts
    767
    There is no compatibility between the 3T and the 6T boards or EPROMS. You can not replace the 3T main board with a 6T board and still use the other components in the cabinet. The 6T had a separate I/O board for the machine interface, where the 3T had these components on the main board, and all those interface signals on the Honda plugs would be completely different. A 3T-to-6T conversion would have to be considered a "full retrofit", with a lot of new interface wiring.

    The 6M (for mills) had the ability to use resolvers and/or inductosyn scales by plugging in a special board for the feedback signals. I think the 6T has the same slot for the board, but the software (EPROMS) for that option are probably not available on the 6T. I don't think the 3T even had a slot for this kind of board. I've never seen a 3T or 3M with resolvers or inductosyn scales, so I tend to think that it's not an available option. If the control does have the slot for the board, I doubt that you could find one anyway. The 3T and the 6T both have pulse-coder inputs on the main boards, so you could at least plug in the same Fanuc pulse coder cables and use the same Fanuc servos. That's pretty much the limit of their compatibility.

  9. #9
    Join Date
    Oct 2007
    Posts
    179
    Thankyou Dan

    I can see unless the 6T was taken from an almost identical lathe complete with all the connection cables it would be like doing a complete retrofit.

    Am I correct in saying that the newer Fanuc controls ie 16, 18, 21 are easier to retrofit.

    I was told that if any of the eproms failed on my Hitachi-Seiki with 6T i would have a real job getting them duplicated where as the on the later Fanuc controls the cnc information can be easily reloaded without replacing eproms.

    John.

  10. #10
    Join Date
    Oct 2007
    Posts
    179
    On the subject of 3t I have seen machines with 3TF . I presume the F stands for FAPT.

    I have a Beaver machine centre with 6ML which has the full Fanuc conversational milling option. Never seen a 6ML anywhere else!

    John.

  11. #11
    Join Date
    Sep 2005
    Posts
    767
    I think the Fanuc 6 was probably the easiest control to retrofit. Back in the 80s, you could buy a little briefcase-size EPROM programmer for the PC (Programmable Controller). This would let you do all the logic for the machine interface and burn a pair of EPROMs for the PC board.

    The "Executive" EPROMs on the Fanuc 3T and 6T are easy to duplicate. If you have a set of good EPROMS now, then anybody with an old EPROM burner can duplicate them at minimal cost. Keeping spares is not necessary though. They rarely go bad.

  12. #12
    Join Date
    Oct 2007
    Posts
    179

    Talking

    Wow that sounds like it might be a way forward for me :idea: ..I was considering changing the servos on my Beaver which has Fanuc 6ML.

    It has Siemens Dc servos and drives which are a pain in the b*t!

    When the a drive card fails it tends to take the motor tacho and stack card with it costing me big bucks to repair!!

    I have a set of 3 yellow caps with drives that came off a Fanuc robot that had only done demo work in a college so they are mint.

    My only problem is the control has no PC board... Instead it uses a Siemens Sestep 400 micro processor controller.

    Maybe I will need to have this controller re programmed or can I fit a new PC board and get the eproms copied from my Bridgeport BPC320H which also has 6MB...?

    I've got to agree with you Dan though the 6t/m is so reliable ..never given me any trouble...I have 4 machine with Fanuc 6 and they are just solid day in day out.

  13. #13
    Join Date
    Sep 2005
    Posts
    767
    You shouldn't have to change the machine interface to swap out the servos. If you have a Siemens programmable controller, you should be able to leave it in place for all the M-codes, T-codes, etc. The Siemens servo amps are probably wired now to the 50-pin Honda plug on the main board labeled "CAV" The pulse coders would be wired to the 20-pin Honda plugs on the main board labeled "X", "Y/Z" and "Z/P".

    If you have a set of Fanuc servo amplifiers and matching motors, all you should have to do is make a cable from CAV to the three CN1 plugs on the bottom of the servo boards and supply the servos with the correct 3-phase voltage (you might need a 3-phase transformer for this).

    I'm not sure what kind of pulse coders you're using now with the Siemens motors, but it's likely that the Fanuc motors will have built-in encoders. If they're the right number of pulses per rev for the ballscrews you have, you should be all set. A 2000 ppr encoder is used for ballscrews with pitches of 2mm, 4mm, 8mm, .200 inch, .400 inch. A 2500 ppr encoder is used for a pitch of 5mm, 10mm, .250 inch, and .500 inch. You should also be able to make cables from the pulse coder plugs on the motors to the X, Y/Z, and Z/P plugs on the main Fanuc board. Wiring diagrams for these cables are in any Fanuc 6 Maintenance or Connecting manual.

  14. #14
    Join Date
    Oct 2007
    Posts
    179
    Thats great Dan. I can soon sort out a transformer and some cables.

    At the moment the Siemens Servos have seperate pulse coders on the back which are 2500 PPR and i'm on 10mm pitch ball screws.
    Also the Yellow caps are 2500 PPR (in built pulse coders) so i'm all set.

    I thought it might be fairly straight forward but wasn't sure if I was missing something!

    Looks like I have some work to do..

    Many thanks Dan.

  15. #15
    Join Date
    Oct 2007
    Posts
    179
    On a similar note Dan am I correct in saying that 6M/T cannot be used with AC servos although it can be used with an AC spindle motor...I seem to remember reading this in the manual...

    I have AC spindle motors on my mills with 6m but they won't do rigid/solid tap.

    I presume the 6m is not capable of matching the feed to spindle speed well enough or is it just down to the spindle encoder used...

  16. #16
    Join Date
    Sep 2005
    Posts
    767
    The 6T and 6M have a +/-10vdc analog output for the servos, so you should be able to use either AC or DC servos, but the control was never designed for the "digital" servo interface. If your servos have an analog input for the velocity (speed) command, then you should be OK. Back when the 6 control was popular, the most common servo was the 3-phase full-wave SCR type, but the 6 was aslo used with the PWM servos as well. I don't think the AC servo technology was quite up-to-speed back then.

    The 6T/M control also has a "F/V" converter (Frequency to Velocity). The pulse coder signals are used for both position feedback and for velocity (tach) feedback. The pulse train from each encoder is fed through an F/V converter circuit, which generates an analog tach signal for the servo amplifier. No separate tach is needed in the motor, which adds reliability to the system.

    The control of the spindle motor is different because it does not use a position feedback in the same way as a servo motor. On lathes, a spindle encoder is used for threading cycles. The 1-pulse per rev. signal is used to trigger the Z motion of the threading pass, and the pulse train is used to interpolate between the spindle rotation and the Z motion (for accurate multi-pass threading). I don't remember if the 6M had any internal software for rigid tapping. If it does, then it would only be on the later model 6MB-2 version. I've never seen a 6M do rigid tapping. Many machining centers of that generation did not have spindle encoders anyway.

  17. #17
    Join Date
    Oct 2007
    Posts
    179
    I see Dan thats made it a lot clearer to me ..trying to sift through the Jinglish in the Fanuc manuals can be a slow process!

    If I recall there was a reference to Rigid tapping in the 6MB-2 manual but I would have to find it again as I can't remember the details.

    I noticed the Siemens DC motors do have the Tacho and encoder seperate on my mill but I think the all in one pulse coder is a much nicer solution...a replacement Tacho cost me £800 recently!

    From what I read in the Beaver manual this seperate Tach/encoder set up makes it quite straight forward for fitting linear scales to the machine by removing the encoders and using the scales for position feedback and keeping the Tach for velocity feedback..

    All in all I still think the DC yellow caps work really well. I'm told AC's will give a slightly better finish on a part because there is less of a "cogging" effect as opposed to using brushes but the finish I get with the DC motors on my other machines is superbe so i'm happy to stick with them.

    Many thanks
    John.

  18. #18
    Join Date
    Nov 2006
    Posts
    925
    Quote Originally Posted by cnc-it View Post
    I see Dan thats made it a lot clearer to me ..trying to sift through the Jinglish in the Fanuc manuals can be a slow process!


    Many thanks
    John.
    I know it`s an old,old post,but need to know is this Sestep 400 still being used or is it available,in fact is any Sestep 400 (or info) available?

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