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  1. #1
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    Spindle Orientation with PICO Universal Stepper Controller

    Hi, I've recently decided to gut one of my fully working Fanuc Controlled CNC machine and go with a PICO Universal Stepper Controller and LinxCNC as a retrofit control system (my first FULL retrofit by the way). I'm in the process of bench testing a lot of the stuff before I start the actual retrofit, however, I seem to be lost when it comes to how to do spindle orientation.

    The CNC machine has a 24 tool magazine. The spindle must be orientated to a specific position in order to do the tool change. From what I gather, it seems I will need an encoder on the Spindle Shaft (and possibly the Spindle Motor shaft as well). The machine has a low and high gear for spindle speeds. (apx 0-1,200 RPM in low and 1,200-5,000 RPM in high)

    I'm in the process of selecting a new Vector VFD Spindle Drive to run the Spindle motor. I'd like it to be a closed loop system and have found a few drives that can do this. However, should the spindle shaft encoder go back to the VFD? Does the PICO Universal Stepper Controller have inputs that I should be using instead? Is spindle orientation normally done by the Spindle drive, the PICO Controller, or by LinuxCNC?

    I found this DISCONTINUED GPD515/G5 Yaskawa Spindle drive that did spindle orientation itself. You would just send the it an Orient command and it would send back an Orientated signal once it had the spindle in position...but this doesn't seem to be what I am finding on newer drives and it confuses me as to why.

    I apologize if my questions have simple answers....I've been looking at VFD's for 2 days straight and I seem to be just confusing myself more as I keep looking. I am hoping someone here can point me in the right direction. Here are some pictures just for reference.
    Attached Thumbnails Attached Thumbnails yaskawa.jpg   IMAG0369.jpg   IMAG0368.jpg  

  2. #2
    Super Moderator Al_The_Man's Avatar
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    The type of spindle drives that have spindle orient built in are usually expensive and often out of the realm of the average VFD, even with encoder option.
    You might find a Mitsubishi spindle drive that would do it, but again, $$'s.
    With many modern spindles, there is pulse feedback from motor to controller but also the spindle itself has an encoder for final accurate positioning, but this requires a drive with servo like capabilities.
    It may be cheaper in the long run to use a stepper with an index mark, or a servo with an encoder to to do the final spindle rotation and perform the index.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

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    I guess I should have given more details. It's a Fanuc AC spindle motor and the machine is from 1981. Right now Fanuc uses a magnet and sensor for spindle orientation. It's an antiquated system and expensive to fix (had to do it once already). I've been finding vector VFDs for roughly $1,000 - $1,500 with the encoder feedback option which I feel is the only way to also do true rigid tapping or to sync the Z axis and spindle speed. I'm at a loss though on how Linux CNC, PICO controller, and the VFD are all supposed to or intended to work together for orientation of the spindle. I don't mind putting $5k to $10 into this machine to replace the Fanuc system with a more modern one. It's also challenging to find examples of others doing this to a machine of this size. This machine has a 5 HP motor and the other machine I intend to do next has a 7.5 HP motor. Thanks as always Al. Your knowledge astounds me.

  4. #4
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    doable with a normal vfd and linuxcnc.. I have not done it but know others that have.

    https://www.youtube.com/watch?v=UlW1s2BNixo

    https://www.youtube.com/watch?v=D6dGYsXAPIU

    and rigid tapping just requires a encoder (3 channel - ABZ) back to linuxcnc. I am pretty sure pico boards have a spindle encoder input. I am sure Jon Elson will be by to explain

    sam

  5. #5
    Super Moderator Al_The_Man's Avatar
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    I would think that even with a 'normal VFD' to get servo control of a VFD might require more than an encoder on the spindle?
    I would be interested to see how it was done?
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  6. #6
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    Quote Originally Posted by barchdesigns View Post
    The CNC machine has a 24 tool magazine. The spindle must be orientated to a specific position in order to do the tool change. From what I gather, it seems I will need an encoder on the Spindle Shaft (and possibly the Spindle Motor shaft as well). The machine has a low and high gear for spindle speeds. (apx 0-1,200 RPM in low and 1,200-5,000 RPM in high)
    There are several ways to do spindle orient, and it partly depends on how accurate the alignment must be for the tools
    to drop into the spindle. The only machine I've seen running EMC with spindle orient was the Mazak at Cardinal
    Engineering. It was done with an early version of Classic Ladder, and part of the job was handled in the PC.
    I think the scheme was that the DC motor drive was set to a very slow speed, and the ladder logic waited for
    a sensor to detect the spindle was close to the desired position, then it fired a pin into the spindle to lock
    it in position, and when the pin sensor showed the pin was fully engaged, the spindle drive was shut off
    and the rest of the toolchange was performed. Does you machine have a locking pin for the oriented
    position? If so, then all the spindle drive needs to do is get close to the desired position, then the pin
    does the final orient.

    If not, then you really do need a servo drive to hold the spindle when the tool is inserted. I suspect this
    can be performed by Classic Ladder, which you will likely want to use anyway for all the toolchanger
    functions.

    The universal stepper controller probably doesn't have enough I/O for such a complex machine,
    do you know how many sensors and outputs you need? You may want to make a custom HAL
    component for the spindle speed/orient function, so as not to burden Classic Ladder with
    that. Running it at the servo rate should be fine.

    The Classic Ladder setup for the "demo mazak" is on your distribution, so you can see how
    Ray Henry did this setup, it may be similar to your machine. It had an arm that rotated 90
    degrees to swing the tools down from the tool carousel which was on the side of the
    machine, so they were parallel to the spindle, then a transfer arm lowered both the
    new and old tool, rotated 180 degrees to swap them, and then raised them into
    the opposite places.

    By the way, why are you using a stepper controller on a servo machine?

    Jon

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    Thanks Jon, and I suppose I left more info out again that was probably needed. Here is an explanation of what we are doing. Hopefully this will help fill in the blanks on what our full intentions are to retrofit this machine.

    The machine uses 3 DC motors for axis movement (2 @ 151VDC, 1 @ 213VDC) and one AC motor for spindle rotation (240VAC). We intend to use (unless you tell me this is a bad idea) an external Arduino or custom built electronics IO board for handling all the automatic tool change stuff. There are quite a few 24V relays that control the 110V hydraulic valves which run the whole ATC system (they rotate the tool magazine, tool pot down/up, swing arm 90/180 degrees, swing arm in/out, etc...). Definitely more I/O than what is on the stepper controller which is why we wanted to use a separate board for this.

    The Pico universal stepper controller is connected to the DC Viper Servo Drives (ViperServo.com) running the 3 axis DC motors with 1,000 CPR encoders on them. We use Viper because I haven't been able to source another servo drive that can go to such a high DC voltage. You can see that Viper Drives use Step and direction input. That part works great and we have bench tested it with a spare Fanuc motor to make sure it all works before we start the full retrofit (see picture). We are feeding back the encoder from each Axis motor directly back to the Pico board for closed loop operation.

    The spindle currently uses a magnet on the spindle with a sensor on the housing. Fanuc has an "orientation" board connected to their VFD using this technology. After I had to pay $500 last year for a used 1980's sensor I definitely want to use an encoder system back to Linux CNC or Pico somehow instead of relying on the magnet and antiquated sensor.

    Thanks for taking the time to talk with me this morning. From what I understand then I can use a standard "Vector Drive" and feed the spindle shaft encoder right back to the Pico board. No need to send the encoder to the Vector drive itself as LinuxCNC and Pico will handle holding the drive still when doing orientation. Since Pico will know the spindle shaft position this will also allow for syncing the Z axis and Spindle speed for true rigid tapping. (Something the machine currently doesn't do).

    I liked the idea of mounting the "index encoder" (Aa,Bb, and Z index channels) so that the index mark of the encoder lines up with the orientation of the spindle for tool changes. Sounds easy enough to do.

    I've still got lots to learn as I go through the process of retrofitting, but I have the time and am willing to learn. I'm in my shop running "Thing 1" CNC about 12 hours a day. "Thing 2" is the CNC machine which will be getting retrofit first. The two machines are almost identical so once "Thing 2" is finished and I run it for a while I will be retrofitting "Thing 1" as well.

    The whole idea behind retrofitting these machines is that I want to make long term repairs less costly and breath new life into these machines so I will be able to use them for years to come. I work for myself and develop aluminum products in my garage and sell them on eBay and through web stores online. It's my full time gig and I don't take on any outside work as I'm not a job shop. I like the idea of being able to interchange parts or use different less costly parts to retrofit the machines when they go down vs having to pay expensive repair bills to Fanuc only to get a repaired board that still has 1980's parts on them.

  8. #8
    Super Moderator Al_The_Man's Avatar
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    What I have used in the past when using Galil Motion cards which although handle the CNC side beautifully, lacks a useful on board PLC, the basic card comes with a 8bit in & 8 bit output port, what I have done is used the output port to transfer a M or T command (decoded binary 8bit) over to a dedicated PLC, which then does all the logic required for the M or T process.
    When the M/T command is complete, a FIN(ish) bit signal is sent back to the Motion card which tells the controller to continue, this method is pretty much an industry standard where a PLC handles the general machine control.
    The advantage to a off the shelf PLC is not only ease of programming but all the I/O are conditioned for the type of I/O components you are using, generally 24dc input and optional relay or Transistor output for relays or solenoids etc.
    Al.
    CNC, Mechatronics Integration and Custom Machine Design

    “Logic will get you from A to B. Imagination will take you everywhere.”
    Albert E.

  9. #9
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    Quote Originally Posted by barchdesigns View Post
    Thanks for taking the time to talk with me this morning. From what I understand then I can use a standard "Vector Drive" and feed the spindle shaft encoder right back to the Pico board. No need to send the encoder to the Vector drive itself as LinuxCNC and Pico will handle holding the drive still when doing orientation. Since Pico will know the spindle shaft position this will also allow for syncing the Z axis and Spindle speed for true rigid tapping. (Something the machine currently doesn't do).
    Well, the only detail is the Pico Systems USC board doesn't have any smarts. So, it will depend on LinuxCNC to command the vector drive to move as needed to hold position. You will have to either code this in ladder logic or a HAL module. There are modules that have been written to do closed-loop speed control, and you can incorporate that. But, you will also want to switch from spindle mode to something like axis mode for the spindle orient function. The way it will work is the spindle slows to a low speed and triggers the spindle encoder counter to go to index mode by raising the ppmc.0.encoder.03.index-enable HAL pin. When the USC detects the next index pulse, it zeroes the encoder counter, the PPMC driver detects this and lowers the pin. Now, the encoder count is synched to the index mark, and your spindle PID calculation drives the motor to keep the encoder count at zero.

    making your own designs is a much better business model (in my opinion) than a job shop.

    Jon

  10. #10
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    linuxcnc has integrated plc and i/o is pretty inexpensive... It seems - and again - I have not tried it. People are using current vfd's with a encoder through a PID loop within linuxcnc for positioning a spindle. (that is what the video's above show)

    sam

  11. #11
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    Quote Originally Posted by barchdesigns View Post
    The spindle currently uses a magnet on the spindle with a sensor on the housing. Fanuc has an "orientation" board connected to their VFD using this technology. After I had to pay $500 last year for a used 1980's sensor I definitely want to use an encoder system back to Linux CNC or Pico somehow instead of relying on the magnet and antiquated sensor.
    I think all you need is a spindle encoder (necessary for rigid tapping anyway) and a VFD with vector control.
    The development version of LinuxCNC has spindle orient outputs now, see the spindle.orient pins:
    MOTION
    You use them to bring a PID component in to play in HAL.
    As it is just an alignment it probably doesn't need to be nearly as stiff as a true servo axis.

    As for the toolchanger, there shouldn't be any need for offboard processing, LinuxCNC ought to be able to handle it, either with the PLC, a lot of standard HAL components, a G-code subroutine or a custom HAL component.

  12. #12
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    Quote Originally Posted by barchdesigns View Post
    I'm in the process of selecting a new Vector VFD Spindle Drive to run the Spindle motor. I'd like it to be a closed loop system and have found a few drives that can do this. However, should the spindle shaft encoder go back to the VFD? Does the PICO Universal Stepper Controller have inputs that I should be using instead? Is spindle orientation normally done by the Spindle drive, the PICO Controller, or by LinuxCNC?
    i would def try and go the VFD route that can do a position stop this would be the fastest way to get it going plus the quickest spindle position stop and tool change.

    i know there are a few on the market that can do it, you need a drive that can do closed loop vector it seems, but you will need an encoder board for the vfd i would say too not many come with it built in probly an extra $50-100 USD. i dont know how big your motor is KW and Amp etc? and speed

    i know Yaskawa do a drive and they do sell it as a CNC replacement afew tech docs for CNC use on the USA website worth a check over.
    Look at the A1000 model, if u go look on USA site you will find a CNC spindle orientation manual under support area.
    it shows u how to do it with encoder input, or magnet switch(hall effect) mounted on spindle side, plus afew other options.
    also i think they put a custom firmware on the drive from reading the manual so you need to check with a sales person.

    gives you a drive that can do to around 12,000rpm (with base speed of 1500 @ 50hz)

    there are other drives that can do it all the same also now.
    control techniques i think could do this also on there Unidrive. but not cheap drives but very good.
    Hitachi i am not sure but iv seen the newer VFDs used alot for spindle drive replacements now cant renumber the model but a good search will soon put you on the track..

    don't forget to check the amp for the motor as a 7.5Kw VFD might not run a 7.5Kw spindle motor, you might need next size up drive to cope with the overload rating....

    the 2nd option is..
    you can also do it with a VFD and control it from linuxcnc with a PID loop iv not done it with a closed loop vector drive but i bet it would be quite easy though compared ot Hz mode and would be as good or better than the old spindle drive.
    i did it with a VFD in Hz mode it works but you need to spin the motor like the old spindle drive did and then put it into a PID loop (ill not go in the tech of why )

    samco put the vids on here above from my work of doing it, it takes abit of messing around with the PID loops etc but it does work , but you do need an encoder on the motor/spindle output but you probably have one for rigid tapping right
    then you can dump that mag pickup also on the side of the spindle.

    with linuxcnc your options are wide open over the old fanuc control in terms of replacements etc....

    i take it you did something to give the tacho feedback for the fanuc ac drives (yellow cap motor drives) as it used to be done on the motherboard...

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