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  1. #1
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    Keling servo as Taig spindle motor replacement?

    I've only changed the belt on my Taig a couple times, and every time it's a PITA. I hate the idea of having a computer controlled machine but having to change the belt manually if I want the tool to spin at a different speed... I'm a nerd, I want my computer to do the work.

    I get a little long winded at times, so I'll keep this post as short as I can...

    (1) If cost was not an issue, would a Keling KL34-170-90 (NEMA 34) motor (w/ encoder), and a Gecko 320/340 make a good replacement for the stock Taig 1/4 hp motor? Motor spec sheet (PDF), other Keling servos
    -To me it looks like this servo is a little more powerful than the Taig motor
    -It's maximum speed is close to the constant speed of the Taig motor
    -I've never used a servo before, and I'd like to experiment a little (I'm a kinesthetic learner)
    -I'm planning to get a Taig lathe in the near future - seems like I'd really want a servo on there. If I decide it's overkill for the mill I could move it to the lathe. If I want a servo on both I'll have gained first-hand experience, which is always good.

    (2) On a CNC lathe a servo is required to cut threads, right? (3) Would a servo offer any advantages over a normal DC motor when used on a mill? I can't really think of anything myself... tapping comes to mind, but I don't really see doing any rigid tapping (I may be using this term wrong, sorry) on the Taig.

    One last question: (4) Since I plan to only use a single pulley ratio between the spindle and the motor should I look into getting a couple timing pulleys to replace the 6-groove Taig pulleys?

    Hmmm... That's not too long.

  2. #2
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    Hmm, no responses.

    I wrote a very long post, but I've shortened it. If anyone is curious about the reasons behind these decisions; send me a PM.

    While writing the long version of this post I pretty much talked myself into going this route and I placed the order. I've decided the 6000 RPM Keling servo is better, it's not quite as powerful, but it's much faster. Also, it looks like the Gecko g320 wont really allow me to run the motors at full speed, so the g340 is what I'll get. I'm also going to pick up a 72v unregulated power supply... Probably the 12 amp one from Keling.

    I'll be sure to post what I do with it all somewhere (probably here, maybe I'll start one of those "blog" things too... we'll see).

  3. #3
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    Quote Originally Posted by Hirudin View Post
    Hmm, no responses.

    I wrote a very long post, but I've shortened it. If anyone is curious about the reasons behind these decisions; send me a PM.

    While writing the long version of this post I pretty much talked myself into going this route and I placed the order. I've decided the 6000 RPM Keling servo is better, it's not quite as powerful, but it's much faster. Also, it looks like the Gecko g320 wont really allow me to run the motors at full speed, so the g340 is what I'll get. I'm also going to pick up a 72v unregulated power supply... Probably the 12 amp one from Keling.

    I'll be sure to post what I do with it all somewhere (probably here, maybe I'll start one of those "blog" things too... we'll see).
    I am considering something similar and I will keep an eye on your progress.
    Although I was just considering going with a dc motor and controller, the servo option/step and direction will allow for rigid tapping and other cool stuff.

    Mike
    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.

  4. #4
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    I did consider a servo to run a lathe spindle, but went with a DC controller and motor.
    I may change that up in the future to a servo. I'll see how this works out first.
    I will also keep an eye on your progress.
    Lee

  5. #5
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    Some where on the net I saw were a guy put one of the Axi Burshless RC airplane motors on his Tiag. For what I remember he was happy with the performance. I like the idea due to it being light compared to other electrical motors.

    http://www3.towerhobbies.com/cgi-bin/wti0093p?&C=GHG

  6. #6
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    Quote Originally Posted by lovebugjunkie View Post
    Some where on the net I saw were a guy put one of the Axi Burshless RC airplane motors on his Tiag. For what I remember he was happy with the performance. I like the idea due to it being light compared to other electrical motors.

    http://www3.towerhobbies.com/cgi-bin/wti0093p?&C=GHG
    I have one, but can the computer control its speed or even on and off. I know that I could use a servo tester and drive it that way, but I like full CNC control. I guess I am spoiled since the big mill retrofit started producing results.

    Mike
    Warning: DIY CNC may cause extreme hair loss due to you pulling your hair out.

  7. #7
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    My last Keling order took a pretty long time to get here (more than a week I think). But I guess that might actually be for the better since I'm also trying to put together an enclosure and set up flood cooling. I told myself I wouldn't dive in head first... oh well, it's fun.

    Here's that long post I mentioned in my last post...
    Quote Originally Posted by me
    The stock motor on the Taig CNC-ready mills is 1/4 horse power and spins at 3450 RPM.

    Horsepower = Pound force feet * Rotations per minute / 5252
    0.25 = Ft-Lbs * 3450 / 5252
    1313 = Ft-Lbs * 3450
    1313 / 3450 = Ft-Lbs
    Ft-Lbs = ~0.381
    ~0.381 Ft-Lbs = ~0.516 N·m

    So, it looks like the Taig 1/4 hp motor has ~0.52 Nm of torque.

    After looking at the Keling motors again I've decided the smaller, lighter, and faster KL34-150-90 (NEMA 34) is a better choice. Its constant torque is 0.84 which is roughly 58% more powerful than the 1/4 hp AC motor. A decent jump, but nothing crazy. Also, it's top speed is 6000 RPM, which will allow a smaller pulley to be used on the motor, which will allow it to be moved closer to the spindle, which will probably reduce the strain on the Z column.

    Keling only offers 2 encoders (a 200 and a 500 CPR quadratic). 6000 RPM is obviously 100 rotations per second. At 100 RPS a 200 CPR quadratic encoder will be pumping out 80,000 pulses per second! (100 x 200 x 4 = 80,000)
    80,000 is already pushing the limit of what my Mach3 install can handle (100,000 pulses per second AKA 100Khz). So, that means I'll have to use the Gecko g340 servo drive (or find some other drive, which I have little interest in doing) so I can reduce the pulses by 10, bringing the new total pulses per second down to 8,000. Well, that give me a lot of working room. Using the same math I can now step up to the 500 CPR encoder that will put out a maximum of 20,000 PPS, a number I'm comfortable with.

    The g340, motor, encoder, and cable are $324.50. The only 72v power supply I see for sale anywhere is the Keling KL- 7212, which is $149.00. Total for this setup: $505.34 shipped. I'm pretty much going to jump unless
    I've been tossing the idea of using timing belts between the motor and the spindle. I guess the biggest thing that's stopping me is an unavailability of small pulleys with a 0.625" bore (for the Taig ER16 spindle). I don't have any tools that would let me accurately expand a 0.500" hole. But, I think I've decided the ratio I'd like to use: 3:2. I figure this'll give me 0 to 9000 RPMs at 0.56 Nm. If I'm calculating it correctly this is more torque than the 3rd pulley (from the bottom) with the 1/4 hp Taig motor and almost as much as the bottom pulley with the 1/8 hp Taig motor.

    I don't see myself using less than 3000 RPMs very much (I'm not sure how I came up with that conclusion... after all, in my illustrious machining carrier I've successfully milled one whole entire piece). But if the need for higher torque arises a 1:2 reduction seems like a good idea (more torque than the 1/4 hp motor + bottom pair of pulleys between 0 and 3000 RPMs).

  8. #8
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    Small update...
    Keling was out of stock of the KL34-150-90s so they're going to send me a KL34-170-90 instead (for the same price). It actually looks like these 2 motors have the same power so by using a different pulley ratio I should be able to get the same RPM and torque as the other motor... I think. I'm not thrilled about the additional size and weight of this motor, but I takes what I can gets.

  9. #9
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    Another tiny update... I've weighed both motors, the Keling servo is almost 3 lbs lighter than the 1/4 hp Taig motor.

    Taig (without mounting plate or screws): 11.55lbs
    Keling KL34-170-90: 8.70 lbs.

  10. #10
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    Smile

    Hirudin,

    I know you want to experiment with the servo however this is a very cost efficient alternative.

    http://tinyurl.com/7fwceo

    http://tinyurl.com/82p7ty

    http://tinyurl.com/7ejzex

    About $100.00 for a motor and speed control.

    Jeff...

  11. #11
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    Not sure what the weight is for those motors and belt drive, but I swear by that motor controller.
    It is fantastic. It let's you fine tune every aspect of motor operation. It actually is a motor controller that gives the operator some input on how it does it's job.
    That would be the best $70 you spend on the project IMO.
    Lee

  12. #12
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    Quote Originally Posted by jalessi View Post
    Hirudin,

    I know you want to experiment with the servo however this is a very cost efficient alternative.
    ...
    Most of the stuff is already here*, so I may as well proceed. I will not be surprised if I later decide to use the servo somewhere else and go with a setup using one of the motors and the controller you posted though.

    *Everything except the Gecko drive, which is being drop shipped (I hate drop shipping). The shipping method I was charged for was UPS, so far everything from Keling has come via USPS. I don't know what method Gecko is using (since I haven't got a tracking number) but I have a suspicion that they used FedEx. I'd normally take this opportunity to go off on FedEx, but I wont. Suffice to say I'm not happy with them.

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