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  1. #1
    So Iím looking at designing the spindle for my machine but Iím not sure of the best way to go.

    Ideally I need it to able to machine wood and metal so high speed and high load will be needed. I have considered just fitting an interchangeable plate on the z axis to fit a router when needed but I would rather use a 3 phase motor and VFD so I can control the RPM, which means a separate spindle is required.

    I bought the Spindle book from the Workshop series which covers small tool post grinders for Lathes. For the spindles in the book it says that Ďanyí type of bearing is suitable, even deep groove ones, but for higher loads then use Tapered rollers Bís ( I presume because of the relatively low grinding and milling speed required by a lathe). However after looking at the data from the Bearing manufactures and other peoples spindles then they use Angular contact bearings for the high speed designs.

    The biggest problem I seem to be facing is that spindle design is basically a compromise to make it fit for purpose, if space is limited and the tool holder is big then it will require a different layout to say a integral motor design so Iím not keen to just copy a design without understanding why.
    At the moment Iím only looking at what bearings to use and the mounting arrangement so the basic design parameters are

    1. High load (milling)
    2. High speed (routing)
    3. ER 32 collet holder
    4. Belt driven or end mounted motor

    So has anybody made something like this or used normal bearings in a spindle?

    Im initially looking an somting like the ones below from SKF web site, but I might be aiming a bit high

    http://www.skf.com/portal/skf/home/p...newlink=9_10_8



  2. #2
    Hi Ross,

    Ambitious!

    On this site they suggest bearing choice is down to the application, so no definitive 'right answer'. Ceramic bearings are sometimes used (silicon nitride).
    http://www.spindleservices.co.uk/Spi...ces_design.htm

    Can you machine it to hold the tight runout a spindle often has?

    What are you thinking of for balancing? Do you think building it all up and sending it off for balancing would be an option? Or do you think offsite individual part balancing, followed by offsite assembly balancing would be required?

    I went for the 3 phase and VFD option for the reasons you mention, plus nice and quiet!

    Here's another bit of info. Mentions bearing specs . . .
    http://henriksplace.se/cnc/new_machi...0_spindle.html

    And for bearing pre-load:
    http://machinedesign.com/article/how...-bearings-0919

    One from the skf magazine:
    http://evolution.skf.com/zino.aspx?articleID=20

    Best of luck . . .
    Last edited by routercnc; 01-08-2010 at 08:31 PM. Reason: more links
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  3. #3
    On second thoughts, maybe start with a die grinder as 2e0poz suggested in another post . . .
    Building a CNC machine to make a better one since 2010 . . .
    MK1 (1st photo), MK2, MK3, MK4

  4. #4
    Thanks Barry.

    Theres some good links that i didn't find, Thats why I like this forum...

    I did see the Henriksplace one and In all reality, design wise, thats what I will end up with, minus the hardening and grinding bit.

    What are you thinking of for balancing? Do you think building it all up and sending it off for balancing would be an option? Or do you think offsite individual part balancing, followed by offsite assembly balancing would be required?
    to be honest I hadn't thought about that, do you think it will that much of an issue? after all it i will be fairly small diameter stuff machined in one operation( if I can sus it out)


    Can you machine it to hold the tight run out a spindle often has?
    Probably not but I have plenty of AL stock and cheap bearings to practice on. and I'm willing to learn, if my lathe will let me.

    I went for the 3 phase and VFD option for the reasons you mention, plus nice and quiet!
    Probably another post in it self but what is the max speed you can get before its to noisy? Have you geared it?

    On second thoughts, maybe start with a die grinder as 2e0poz suggested in another post . . .
    Yeah I have concidered that as apparently they have a double A/C bearing in the nose but having looked at this site

    http://www.cncathome.com/spindles.html

    he reckons that they are are just up rated routers so the noise is a problem, but i would like to know if anyone has had any success with them?
    Last edited by Ross77; 02-08-2010 at 12:44 AM.

  5. #5
    Whats wrong with an induction motor being used?

    This one I have is heavy and I reckon its the motors body thats the bulk of the weight?

  6. #6
    lol that vid is awsome,I do like his tool changer method :clap:

  7. #7
    Hi George

    As you stated induction motors are heavy (not good on a z axis) and I believe are difficult to control the speed. :nope:

    The idea of using a 3 phase motor and Variable Frequency Drive (VFD) is that you feed it 240v AC at a set current and control the speed by "varing" the frequency of the AC supply. Therefore you get full (ish) power over the whole speed range. not to mention over speeding the motor to way beyond its rated speed if you dare........

    I'm by no means an expert on this so I plan to post a separate question on motors later if your interested?

  8. #8
    Just use a 750wLight dimmer. lollol

  9. #9
    Quote Originally Posted by GeorgeD View Post
    Just use a 750wLight dimmer. lollol
    That's a bright idea.
    John S -

  10. #10
    Just use a 750wLight dimmer. lollol
    Thanks thats really usefull (dont know why I bothered posting, 10 replies and only 2/3 serious ones)

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