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  1. #1
    Good evening All
    I have just bought a chipmaster to convert to cnc. The first challenge is the 1.5 hp 440v motor. I know I can rewire it for 240 and run off a vfd but I'm not sure it is worth the hassle and I'm looking for other options.

    My goal is to cut accurate threads so I have been looking at a closed loop vector VFD for the spindle. Is this the best option or am I OTT?

    Ive been out of it for a while so not sure of the latest tech. any suggestions welcome.

    Thanks in advance

  2. #2
    If the motor is dual voltage and can be rewired 240 then that and a drive would be the quickest option, vector drives do a good job of stabilising motor speed.

    - Nick
    If you will not be swayed by logic or experience simply pick the idea you
    like best, but ask yourself why you sought advice in the first place and,
    for a simple life, perhaps consider not doing so in future

  3. #3
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,703. Received thanks 176 times, giving thanks to others 5 times.
    Accurate threading is far more dependant on what motion controller you'll be using, than how the spindle is powered.

    A basic VFD will drive the spindle good enough to thread.
    For the most accurate threading, a motion controller that will accept a spindle encoder signal is the best option. Something that uses a single pulse can produce acceptable threads, but it'll depend on the level of accuracy you're aiming for.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  4. #4
    Hi Ross,
    Long time no hear! Have a look at these -

    Setting up Mach3 for lathes:
    https://www.youtube.com/watch?v=ZSbljHlBgaY

    Fitting an index ring to give pulses to Mach:
    https://www.youtube.com/watch?v=yY_4HwmZEaQ

    Thread cutting:
    https://www.youtube.com/watch?v=6yzrMNjGVDA

    And my favourite manual thread cut video:
    https://www.youtube.com/watch?v=Lb_BURLuI70

    My understanding is you don't necessarily need a special VFD / motor combo for CNC thread cutting, just a good pulse feedback to Mach3 (through an interface card I believe) so that the feeds are synchronised to start at the same point on each pass.
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

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  6. #5
    Thanks Guys.
    I have been going back and forth on the open loop vs closed loop vfds. some say that a closed loop vfd will keep perfect time and then mach only needs the 1 pulse per revolution.


    The existing motor is the original 1.5hp so would be looking to switch up to a 3hp, its the vector vfds that jump up in price.

    I'll have a look at the cards. as I want to do fine threads. I have just got two pci card encoder controllers but they are absolute and not incremental so probably no good. any motion controllers you can recommend?

    Thanks for all the Links Rcnc, I will have a look later.

  7. #6
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,703. Received thanks 176 times, giving thanks to others 5 times.
    Unless you're going to replace the v-belts with a toothed belt, a closed loop motor isn't going to be much benefit, as the belt will cause slight speed fluctuations as load changes.

    You also need to consider gearing, and how much torque you're likely to need at the spindle. Are you going to continue to use the gears, if so you need to factor that in, at which point you need to use a spindle encoder, as you'll struggle to get threading to work in multiple gears without a spindle encoder.

    Off the top of my head, the following motion controllers spring to mind-

    PoKeys 57CNC something or other (I think it supports encoders)
    PMDX have a couple motion controllers, but they're Mach 4 only, and you'd need to check they support lathe (I think they do, but not 100% sure)
    CS-Labs CSMIO/IP-A or S along with their threading module.
    Dynomotion KFlop either on it's own, or with any of their add-on boards (Mach 3 only, or use their own KMotionCNC software)
    SmoothSteppper, however I'm not sure if they have implemented full encoder for the spindle yet.

    There are also the UC100 and 300, however I'm not sure if they support turn/threading.
    A key thing to consider, is if the boards support turn/threading. Not all boards do.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

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  9. #7
    Without getting a load of flack. Linuxcnc with a mesa card is what I use on the lathe with a 60 slot encoder disc on the spindle.
    ..Clive
    The more you know, The better you know, How little you know

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  11. #8
    m_c's Avatar
    Lives in East Lothian, United Kingdom. Last Activity: 17 Hours Ago Has been a member for 8-9 years. Has a total post count of 1,703. Received thanks 176 times, giving thanks to others 5 times.
    Quote Originally Posted by Clive S View Post
    Without getting a load of flack. Linuxcnc with a mesa card is what I use on the lathe with a 60 slot encoder disc on the spindle.
    Get the pitch forks sharpened! ;-)

    I've got a Mesa card sat on my desk just now, which is on my list of things to try, as I want to have a play with PathPilot. Got no intention of fitting it any machine, as I like my KFlops.
    Avoiding the rubbish customer service from AluminiumWarehouse since July '13.

  12. #9
    Quote Originally Posted by m_c View Post
    Get the pitch forks sharpened! ;-)

    I've got a Mesa card sat on my desk just now, which is on my list of things to try, as I want to have a play with PathPilot. Got no intention of fitting it any machine, as I like my KFlops.
    I take it then you have read the posts from cncbasher on the other channel.
    ..Clive
    The more you know, The better you know, How little you know

  13. #10
    Wow, information overload. Going to take a while to look over all those options.

    The pokeys looked quite good but is a bit pricey and not sure it dose threading. Thanks for the heads up, seems a lots has changed since I last dabbled with cnc.

    Might have to go over to the driver section and catch up.

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