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  1. #1

    Am i crazy or will this work?

    So im not new to building machines, i retrofitted my onefinity with a ATC spindle and got 2.5 cubic inches MRR in aluminum.

    Now im ready to move into steel(i dont have a need but I'm sure i could get work pretty quick and i have some parts i personally would like to make.)

    I bought a second machine, a HDM. I bought it because i run my onefinity lights out and i could fill it with more parts machining aluminum.

    https://shop.carbide3d.com/products/...39378702532669



    That saidddddd, i love the idea of these cheap machines running and mistakes being cheap.
    Im thinking what if i convert this thing with servo spindle and use it for steel.
    Ill probably use Masso like my Onefinity and i definitely want ATC. so im wondering if this configuration will work. Keep in mind, i made this model in 20 minutes and its for nothing other than concept.

    My Main concern is speed on the Z axis as thats part of the equation of MRR.

    The idea would be to use a belt to drive from the Servo to the mounted spline linear bearing, this turns the shaft down to the spindle cartridge and allows the spindle to move up and down with the spline bearing moving along the shaft.
    There would probably be another bearing to capture the shaft above the one transmitting power and rollers to prevent the spline linear bearing from moving up and down when the spindle cartridge moves.

    Then for the ATC, i would also keep the air cylinder off to the side and making a lever to transmit the power down onto the spindle cartridge, just to keep the weight off the Z axis.

    Im sure its not this easy and im missing stuff so help me see the light if im crazy.



    https://www.mcmaster.com/61145K172/
    https://www.mcmaster.com/61145K115/
    Attached Thumbnails Attached Thumbnails Capture.PNG   spindle.jpg   servo.jpg  

  2. #2

    Re: Am i crazy or will this work?

    Very creative, looking for your update.
    http://cncmakers.com/cnc/controllers/CNC_Controller_System/CNC_Retrofit_Package.html

  3. #3
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    Re: Am i crazy or will this work?

    Hi,
    how much current does the 3.8kW servo draw? 2.2kW is considered a practical maximum for a domestic single phase supply.
    Even with a power factor of 0.6, which is optimistic for a servo, 3.8kW suggests 27A at rated power and potentially 54A at 200% overload.

    Craig

  4. #4

    Re: Am i crazy or will this work?

    @joeavaerage

    looks like they are only pulling 13.5 amps so my guess is you just caught them lying.

    https://www.aliexpress.com/item/3287...50244776%22%7D

  5. #5
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    1441

    Re: Am i crazy or will this work?

    Hi,

    13.5 x 230 =3105 W, well short of 3.8kW. My guess is that the current stated is the output current per phase.

    Single phase input current can be calculated:
    3800 /230 = 16.9A, but this assumes unity (1.0) power factor whereas 0.6 power factor is optimistic:

    16.9 / 0.6 = 27.5A.......and remember the power factor could be lower, lets say 0.5....then:
    16.9 / 0.5 =33.8A.

    With a 200% overload your 3.8kW servo could draw as much as 67.6A.....and that will trip most, if not all, domestic circuit breakers.

    Low power factor is a plague of servo drives and VFDs. It can be improved but at some expense.

    Craig

  6. #6

    Re: Am i crazy or will this work?

    Quote Originally Posted by joeavaerage View Post
    Hi,

    13.5 x 230 =3105 W, well short of 3.8kW. My guess is that the current stated is the output current per phase.

    Single phase input current can be calculated:
    3800 /230 = 16.9A, but this assumes unity (1.0) power factor whereas 0.6 power factor is optimistic:

    16.9 / 0.6 = 27.5A.......and remember the power factor could be lower, lets say 0.5....then:
    16.9 / 0.5 =33.8A.

    With a 200% overload your 3.8kW servo could draw as much as 67.6A.....and that will trip most, if not all, domestic circuit breakers.

    Low power factor is a plague of servo drives and VFDs. It can be improved but at some expense.

    Craig
    Thanks Craig, you're the man.

    ill go with something more along the lines of this, unless you have a better suggestion.

    https://www.aliexpress.com/item/3305...48bd4177qZxbOX

  7. #7
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    Re: Am i crazy or will this work?

    Hi,
    the smaller unit you linked to will demand less current from your supply, and that may help.

    What most people don't realise is just how much current a servo drive or VFD can draw. If you are aware of the power requirements and are prepared to have an electrician fit a larger
    cable/breaker/and socket then no trouble. If however you plug your machine into a regular 10A or 15A socket when your spindle digs into some heavy going the breaker will trip.

    We shifted our business premises last week. We had an electrician install a new three phase circuit, three new 20A single phase circuits and run a 16mm cable in preparation for
    my new 2.8kW servo based single phase spindle motor It will have a 50A D curve breaker when equipped. I will still have power factor correction, as much for electrical noise abatement
    as input current reduction. I've yet to decide whether I'll go for a line reactor or build my own active power factor correction module.

    I have not used Lichuan servos, they have abysmal documentation and have no set-up and tuning software. I use Delta B2 series servos, they are about 25% more expensive but well
    worth it in my opinion.

    Craig

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