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Thread: CNC wiring: how to intregrate on/off, contactors, e stop etc

  1. #1
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    Default CNC wiring: how to intregrate on/off, contactors, e stop etc

    I'm trying to get my long dormant cnc mill project finished (bport series I rigid ram CNC I'm changing over from steppers to AC servos). This thing has been lurking for eons and I want to get the darn thing finished!

    Each axis has a controller box (Yaskawa), with its own contractor, that has a 110/220 activating coil.
    There's a breakout board to PC
    VFD for the spindle.
    220 1P in to everything.
    I need 24V for the breakout, I thought I might hook up a 12V HD wallwart to the 240V. I've got some old Nortel ones that I could use.

    I want low voltage controls at the front, so I need a relay to turn on 220 to power the contractors to turn on the controllers. I want the VFD controls separate from the cnc controls and also low voltage at the front, on/off, direction, speed. There is a good mechanical speed control with a high/low range. I see some advantage in the cnc control turning the spindle on and off, but if I used that I want a front panel control that overrode it so I can turn it off for gearbox changes and to know it was effectively locked out for tool changes.

    I could probably figure all of that out, but I get a little confused integrating the E stop, which I obviously want to turn off the controllers and spindle motor. So the estop should interupt the VFD, and interupt the controller and if the controller is interrupted it there is some output signal I used to switch off the contractors?

    Any help to clarify how to come at this is appreciated, thanks.

    PS...BOB is below, I will probably buy an updated one so I can use USB instead of a parallel port, it would let me use an existing laptop



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  2. #2
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    Is that a low priced Chinese BOB & you're going to use Mach3 or LinuxCNC? If so, you really should consider some more serious ethernet based hardware, not parallel port or USB. Mesa for Linux, and at least a Centroid Acorn for Windows. The Acorn & software is proven & the wiring you want is already there: https://www.centroidcnc.com/centroid...ontroller.html Scroll down in the Acorn page to "Acorn CNC controller Hookup Schematics" & there's a .pdf schematic for exactly what you're wanting.

    (Edited to add USB...I missed your mentioning it. IMO USB is not stable enough for CNC.)
    Last edited by DICKEYBIRD; 05-25-2019 at 08:07 AM.
    Milton

    "Accuracy is the sum total of your compensating mistakes."

    "The thing I hate about an argument is that it always interrupts a discussion." G. K. Chesterton

  3. #3
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    There's many different questions in this one post. I'll tackle the VFD and Estop. Consult your VFD manual but most decent VFD's have a programmable input for this. It receives 24v in, it knows it is safe to operate. The 24v goes low, the VFD defaults to an error state, perhaps uses the dynamic brake or external braking resistor to stop the spindle. Also, I highly suggest that every safety related switch including stops are wired normally closed. In case a wire breaks, the mill stops, just like the safety air brakes on a train.

  4. #4
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    An E-stop should always be a hardware operated circuit, typically a N/C string of all the devices that activate the stop (NAND circuit) , ending up at the coil of the E-stop relay.
    The e-stop relay etc can advise your controller that an E-stop has taken place in order to stop the software control from continuing, also in the NAND string any controller watch dog timer or other charge pump etc can be inserted in order to achieve an e-stop in the event the controller crashes etc.
    All motive power should be disconnected via the result of any E-stop.
    A useful asset is a copy of NFPA79 for typical circuits etc.
    Max.

  5. #5
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    What MaxHeadRoom said... (also - the computer can be allowed to reset the estop loop after the fault has been corrected)

  6. #6
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    I converted a Series 1 Boss 5 BP to a PC based control a few years ago. For the spindle control, I kept all the BP wiring, switches, and contactors intact. There are only 3 or four wires on the terminal strip at the bottom of the power cabinet that need to be connected to the control; E-stop from the mushroom button, spindle enable, spindle acknowledge (might not be correct term, I wired it to Block Allow on the control). My spindle operates just like the original Boss control: the spindle has to be started manually, and the control can only turn it off.
    For the 24V power supply, I used the original transformer, bridge rectifier, and capacitor. I doubt a wall-wart would have enough capacity to power the spindle brake and speed changer solenoids. The only thing that uses 240V single phase is the RPC that supplies the 3 phase spindle motor.

  7. #7
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    Quote Originally Posted by DICKEYBIRD View Post
    Is that a low priced Chinese BOB & you're going to use Mach3 or LinuxCNC? If so, you really should consider some more serious ethernet based hardware, not parallel port or USB. Mesa for Linux, and at least a Centroid Acorn for Windows. The Acorn & software is proven & the wiring you want is already there: https://www.centroidcnc.com/centroid...ontroller.html Scroll down in the Acorn page to "Acorn CNC controller Hookup Schematics" & there's a .pdf schematic for exactly what you're wanting.

    (Edited to add USB...I missed your mentioning it. IMO USB is not stable enough for CNC.)
    I went quiet as Milton your post caused me to think more on this and that my assumption was wrong....slap a cheapo BOB in, fire up some CAM software and away I go isn't going to cut it. in reading through the functionality centroid offers as well as an RJ45 connection, it or something similar would be the way to go.

    I've heard some service and software complaints on Centroid (going to look at installation soon to get more familiar) and I really dislike that the BOB/controller is married to the software. Mach 4 otoh, I really dislike that you have register some PC ID to make the software work (I wouldn't buy it if I was a crook, but don't bloody well load up my life with future complexity if I want to change computers. I probably wouldn't even buy the final computer until some future point and initially run it on a temp one). i suppose I could find something not to like about all them, but those are really irksome.

    Question for anyone up on this stuff, what are the current best choices of software and BOB/controller board (I already have the servos and servo controllers)? I'd like a slick piece of software, pendant and full function board (like the idea of controlling the VFD through it, fixing an encoder for rigid tapping, possibly a probe, etc). The machine as a bport series I with 750w Yaskawa servos
    Last edited by Mcgyver; 07-30-2019 at 05:01 PM.
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  8. #8
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    If you want rigid tapping that works really well

    Linuxcnc + mesa. Linuxcnc is free and open source - mesa interface hardware is inexpensive.

    As far as a pendent goes.. I usually create a descent control panel. (mpg + a few rotary switches for jog increment and type (Feed override, Maximum velocity, Spindle override, Feed override, X jog, Y jog, Z jog)

    I do have an HB04 wireless usb pendant with when I have used it seems decent. A hardwired jog wheel hooked into realtime just works so much better.

    You could do full closed loop to if you wanted (assuming the yaskawa drives allows it..)

    sam

  9. #9
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    A lowly 750w spindle...

    https://youtu.be/E2t0y2EsSO8?t=485

  10. #10
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    I forgot I did a startup of the K&T to show how the estop loop works in this situation


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