584,327 active members*
6,557 visitors online*
Register for free
Login
IndustryArena Forum > MetalWorking Machines > Okuma > Okuma LB-12 Spindle Deceleration
Results 1 to 12 of 12
  1. #1
    Join Date
    Feb 2010
    Posts
    0

    Okuma LB-12 Spindle Deceleration

    First time poster so some quick background - I'm a small, one-man shop that does work on the side for various self funded projects as well as some decent paying work for local companies. I have a regular day job at the moment but hope to make the fabrication business full time some day.

    I have a few questions: I recently acquired an LB-12 with OSP-500L-G control (green screen) that I'm running off of a 25 hp phase converter. I haven't done much work with the lathe yet but everything seems to work okay with the exception of deceleration. If I'm running the spindle at a given RPM then command a spindle stop, I get large voltage (don't have the numbers with me here) spikes in the line voltage as measured at the disconnect switch. I understand that some newer machines feed the power generated during braking back onto the grid, but I can't imagine that my 1988 vintage machine would have such a feature. I'm wondering if there are some braking resistors or other electronics that may be burned out? FYI there aren't any control or spindle drive errors.

    Along the same lines (and maybe this would be enough to solve my problem), is there a parameter or adjustment that can be made to limit the spindle acceleration / deceleration to some lower level? The lights dim somewhat when I start the spindle and I'm not trying to make thousands of parts with the machine, so if I loose a little bit of my efficiency having to wait for the spindle that's fine with me.

    Any help or feedback/comments would be greatly appreciated!

    Thanks!

  2. #2
    Join Date
    Mar 2009
    Posts
    1981
    command a spindle stop, I get large voltage (don't have the numbers with me here) spikes in the line voltage
    it's normal. Motor works as a generator
    I can't imagine that my 1988 vintage machine would have such a feature
    yes, it has. Okuma was very progressive at that time. Who told You it's feature?
    is there a parameter or adjustment that can be made to limit the spindle acceleration / deceleration to some lower level?
    It depends. Only authorized representative can answer if it has. You need to provide OSP data management card asking such a question.
    having to wait for the spindle that's fine with me
    You don't need to wait while spindle stops fully. Use M63, M64, M66.
    The special subprogram with decelerating spindle speed can help also:
    S1000
    G04 F1
    S800
    G04 F1
    S600
    G04 F1

  3. #3
    Join Date
    Feb 2009
    Posts
    6028
    Voltage spikes-normal on early okumas. They used a line regen system on the drives, i've seen computers blow up and lights get bright. A filter is the only way to solve this. $$$$

    Accel speed well, since you didn't specify what drive you have, since some early Okumas use a Fanuc drive. From your regen issue, i'm assuming its a blue type A okuma drive. There is a jumper on the front board to control this. I can't remember any more what number the jumper was, but get in touch with rick deiden at gossiger service in LA. He would know.

  4. #4
    Join Date
    Jan 2010
    Posts
    96
    Yes Algirdas is correct. I used to be in field service for an Okuma dist and can confirm the regenerative braking. OKuma led the way in a lot of areas, so your voltage spikes are normal. I would question the 25HP phase converter. That size is probably pushing it in size and phase converters aren't generally very efficient anyway unless you have a VERY expensive one.

  5. #5
    Join Date
    Feb 2010
    Posts
    0
    Thanks for the replies - I'm surprised to find out the machine has regenerative braking so it seems that I'll have to slow the spindle down in steps via the program.

    underthetire - I do have a blue A type drive and there are several dip switches on the first board - I assume that one of these may be the one you were referring to.

  6. #6
    Join Date
    Feb 2010
    Posts
    0
    Does anyone have a copy or know where I can find a manual for the VAC A type drive? ebay has several manuals for the newer drives but not for the older ones.

    Thanks.

  7. #7
    Join Date
    Feb 2009
    Posts
    6028
    Quote Originally Posted by sunmach View Post
    Thanks for the replies - I'm surprised to find out the machine has regenerative braking so it seems that I'll have to slow the spindle down in steps via the program.

    underthetire - I do have a blue A type drive and there are several dip switches on the first board - I assume that one of these may be the one you were referring to.
    Yep. those are them. You can set them for a slower ramp up/down. Just don't remember what was the correct ones anymore. Maybe if i was still in my 30's......

  8. #8
    Join Date
    Feb 2007
    Posts
    54
    I am in a similar situation to underthetire, there is an LB12 OSP500l-g sitting in the shop next to me that nobody knows how to use.

    I can put programs on from mastercam
    No leaks
    Powers up fine etc...
    unit is in great condition


    But I have questions on simple concepts:

    getting the spndle to turn in manual mode? no luck after using MIDI comannds and the normal procedures I used for other machines...

    getting tool offsets especiially for ID tooling (no tool sensor)

    If you would prefer I start on another post let me know

  9. #9
    Join Date
    Mar 2009
    Posts
    1981
    that nobody knows how to use
    You need some manuals or training material
    spndle to turn in manual mode?
    spindle will run in manual mode only after S command from MDI or auto. Othervise speed is not defined.
    no luck after using MIDI comannds
    You have alarm message on MDI. You have diagnostic message, sure.
    It can be door interlock or chucking fault.
    getting tool offsets especiially for ID tooling
    You touch a surface and key in "Calculate 20" in tool offset X. Here "20" is the ID diameter what You touched.
    Z offset:
    You take "zero" tool - the one You use for rough facing and You place it where Your program zerro is according part drawing. There You calculate user Z zerro.
    Then You place there next instrument and you calculate Z offset of this instrument is zerro there
    If you would prefer I start on another post let me know
    Actually, it's quite different subject

  10. #10
    Join Date
    Feb 2009
    Posts
    6028
    Quote Originally Posted by roger_e View Post
    I am in a similar situation to underthetire, there is an LB12 OSP500l-g sitting in the shop next to me that nobody knows how to use.

    I can put programs on from mastercam
    No leaks
    Powers up fine etc...
    unit is in great condition


    But I have questions on simple concepts:

    getting the spndle to turn in manual mode? no luck after using MIDI comannds and the normal procedures I used for other machines...

    getting tool offsets especiially for ID tooling (no tool sensor)

    If you would prefer I start on another post let me know


    An Okuma will not start the spindle unless it has a part clamped in the chuck and a clamp signal from the switches on the back. I was just offered an Okuma LB12, or a LB9, my choice for 4K. I really want the LB12, just wish I had somewhere to put it.

  11. #11
    Join Date
    Apr 2011
    Posts
    0
    You need regenerative frequency drive to run this size of CNC on a single phase, but I don't think anybody makes them. You can try dynamic breaking option for that drive as well. When You stop the spindle, spindle drive goes into "regenerative mode" essentially putting the inertial energy of the motor+spindle and any other rotary parts through motor and drive to the mains source. In normal installations You would have a low grid impedance and You wouldn't see voltage rise (that voltage rise equals regenerative current times equivalent series grid impedance). Drive has line reactor built in and on the machine side everything is OK. The problem in Your case is that the drive You are using for power source doesn't have regenerative capability to transfer that energy to the electrical grid. It ends up in the capacitor bank of the source drive causing it to fault on over-voltage alarm. Sometimes You can get by installing capacitor bank to the drive (either one that has pre-charge circuit). The energy gets pumped into the capacitor bank causing the voltage to rise less than the over-voltage threshold point. Too much theory in one post, but this is the explanation in brief.

  12. #12
    Join Date
    Nov 2015
    Posts
    17

    Re: Okuma LB-12 Spindle Deceleration

    Old thread, but always good for me.

    I have an LB300-M with this type of problem.

    Filter is too expansive for me.

    Change my lathe... mmm... work good, no

    (i have LB3000EXII and no problem in deceleration)

    With OSP-U100L is possible change the time of deceleration? maybe this is a solution for me. Thank you!

Similar Threads

  1. Fanuc 10M Spindle Deceleration Rate
    By thanks! in forum Fanuc
    Replies: 1
    Last Post: 05-13-2013, 06:58 PM
  2. dx-32 Spindle Acceleration/Deceleration Problem
    By cybermachineman in forum Bridgeport / Hardinge Mills
    Replies: 4
    Last Post: 05-22-2011, 07:01 AM
  3. Spindle Deceleration Problem
    By Hash01 in forum Okuma
    Replies: 4
    Last Post: 04-01-2011, 05:16 AM
  4. Replies: 3
    Last Post: 01-10-2011, 08:09 PM
  5. Replies: 6
    Last Post: 12-21-2010, 07:36 PM

Tags for this Thread

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •