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IndustryArena Forum > CNC Electronics > Spindles / VFD > DC Servo for Mach3 spindle
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  1. #21

    Re: DC Servo for Mach3 spindle

    Be aware that most rigid tapping setups require an encoder that is 1:1 geared to the spindle and has an index pulse. For many machines that can be a problem.

    It still seems to be on trend to try to use servo drives on the spindle. However, most controllers are expecting to see a VFD in that position, so control of direction and speed control needs to be considered.

    Although rigid tapping seems like a rite of passage, a tension-compression head has a lot to recommend it. You simply need to achieve reasonable speed control in order to synchronise the Z axis feed to the thread pitch. Just saying.

  2. #22
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    Re: DC Servo for Mach3 spindle

    Quote Originally Posted by zvizdic View Post
    As you can see in the video I build my own spindle Cat/bt with spring holding pull stud that in the future I can add air or some other tool release.
    I'm looking at having a go at my own cat/bt spindle holder myself at some point.
    I want to have a go at an atc build but don't want to base it on TTS system for the R8 head I have at present.

  3. #23
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    Quote Originally Posted by dazp1976 View Post
    6nm or (600n-cm) constant. Peak of 18nm or (1800n-cm).
    Or 850 / 2550 oz-in.
    Voltage rated 220.
    See if I do 2 to 1 ratio I am going to have almost the same torque as your motor. Not that I’m compering apple to orange but my choice is clear considering lower power requirements and smaller size to give me power at lower rpms .

  4. #24
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    Re: DC Servo for Mach3 spindle

    Quote Originally Posted by dazp1976 View Post
    I'm looking at having a go at my own cat/bt spindle holder myself at some point.
    I want to have a go at an atc build but don't want to base it on TTS system for the R8 head I have at present.
    I took a big risk to base spindle on wheel bearings and it payed off .
    Like I mentioned I work in the machine shop. I can make stuff on my own time.
    I used SKF wheel bearing as a main bearing then I ground one inner race -.002" to give more preloading adjustment as needed,ordered G10 bearing balls to replace chip ones (way more precise) top bearing is a manual mill spindle bearing (beater one when replacing bearings on mill at work) took of top seal on wheel bearing so I can put oil to lubricate bearings (bottom seal holding oil no problem plus have spare).
    So happy with results.

  5. #25
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    Re: DC Servo for Mach3 spindle

    Quote Originally Posted by zvizdic View Post
    See if I do 2 to 1 ratio I am going to have almost the same torque as your motor. Not that I’m compering apple to orange but my choice is clear considering lower power requirements and smaller size to give me power at lower rpms .
    Downside is the loss of rpm's.
    Pay attention to the notes on page 17 in the U series section:
    Such as:

    B. The motor can be operated at any point on the graph below
    4000 RPM. Higher speeds can be obtained for short periods of time.
    Contact a Kollmorgen Sales Office for more details.

    Is it worth it?.

  6. #26
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    Re: DC Servo for Mach3 spindle

    Good point but I need this motor exactly for low rpm and high torque, spindle side up to 1500 motor side 3000rpm or less depending on tool size.
    For high rpms i have router 10000 to 30000 rpm fits 1/4 or lower diameter bits.Lock at my videos you can see.
    Planing to run at 24v power supply or less i can dial rpm to 3000 by supply voltage.

  7. #27
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    Re: DC Servo for Mach3 spindle

    Hi,

    If am correct brushless ac is a bigger in size but less torque then brush dc servo motor.
    Brushless motors have fixed windings around a permanently magnetized rotor, whereas a brushed motor has windings on the armature (rotor)
    connected via brushes to the power supply and permanent magnets around the outside.

    Both types produce plenty of torque and both are about the same size.

    Brushed motors were very common years ago and still work OK, but brushless motors are taking over. The brushes wear out eventually. Second,
    there is high current in the rotating armature in a brushed DC motor with considerable heat build up. In a brushless motor the high current is in the fixed windings
    and the heat can be conducted away into the servo housing which cannot be done with a rotating armature. On balance a brushless motor should produce more
    power for the same heat loss....but there's not much in it., both types are used for spindles.

    If you are interested in getting a more powerful motor then you might consider a DC motor out of a treadmill. They often come up second hand pretty cheaply.
    They are not common here in New Zealand but they are popular in the US on Ebay. I believe there are two models which are particularly common, one about 1.5hp and another
    about 2.25hp.

    dazp1976 has a 1.8kW AC servo, I think Lichuan brand, that was very well priced. A few years ago I bought a second hand 1.8kW Allen Bradley AC servo and drive for $600US
    for the pair. I still had to find/buy/make the cables and I paid for the set-up and tuning software, but it has made an excellent spindle motor.
    I mostly use it in velocity mode, that is the controller provides a 0-10V PWM signal and the servo responds from 0rpm to 3500rpm, its rated speed. Because the velocity loop is closed
    by the servo drive the revs don't change virtually at all with load, very handy. I use it sometimes in position mode and then it makes for a good rigid tapping spindle.
    Note that it has a rated torque of 6.2Nm and an overload of about 18Nm, so its pretty limited as to what size taps it can drive into different materials. I find that 8mm in steel
    is a safe max and 10mm, sometimes 12mm in aluminum. You also need to be VERY particular about the hole size drilled prior to tapping, if you try to drill a smallish hole
    resulting in a high engagement, 65%, or more thread then you are heading for disaster. To do rigid tapping well and reliably requires lots and LOTS of torque, more than you
    might imagine otherwise it all turns to s....t!

    Depending on where you are you may find a good servo and drive somewhere for cheap...grab it, you won't be disappointed, they make excellent spindle motors.

    Craig

  8. #28
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    Re: DC Servo for Mach3 spindle

    Quote Originally Posted by joeavaerage View Post
    Hi
    dazp1976 has a 1.8kW AC servo, I think Lichuan brand, that was very well priced. A few years ago I bought a second hand 1.8kW Allen Bradley AC servo and drive for $600US
    for the pair. I still had to find/buy/make the cables and I paid for the set-up and tuning software, but it has made an excellent spindle motor.
    I mostly use it in velocity mode, that is the controller provides a 0-10V PWM signal and the servo responds from 0rpm to 3500rpm, its rated speed. Because the velocity loop is closed
    Depending on where you are you may find a good servo and drive somewhere for cheap...grab it, you won't be disappointed, they make excellent spindle motors.
    Craig
    You are correct. My Lichuan seems a basic setup but feels well made.
    These things certainly have some balls in them!.

    Like Craig says, If you can find a good servo and drive somewhere for cheap...grab it

  9. #29
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    Re: DC Servo for Mach3 spindle

    Quote Originally Posted by zvizdic View Post
    For high rpms i have router 10000 to 30000 rpm fits 1/4 or lower diameter bits.Lock at my videos you can see.
    Planing to run at 24v power supply or less i can dial rpm to 3000 by supply voltage.
    You're not talking about lowering a router spindle to 3000rpm are you?.
    They're not really meant to go below 8k because of burn out.

  10. #30
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    Quote Originally Posted by dazp1976 View Post
    You're not talking about lowering a router spindle to 3000rpm are you?.
    They're not really meant to go below 8k because of burn out.
    No I was talking about servo motor .
    Router has adjustable speed on its own .

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