Welcome to Our Community

Some features disabled for guests. Register Today.

Belt Driven Spindle?

Discussion in 'CNC Mills/Routers' started by Joe Eagar, Feb 5, 2018.

  1. Joe Eagar

    Joe Eagar Well-Known
    Builder

    Joined:
    Feb 5, 2018
    Messages:
    3
    Likes Received:
    1
    I'm trying to build a CNC machine that can mill steel. After a bunch of reading, I've come up with some design ideas based on a steel-reinforced cement frame. Here's an unfinished prototype I made to test vibrations:

    20180204_235737.jpg

    By the way, I don't plan to use a corexy setup. Anyway I think the cement frame will work, but after watching a bunch of YouTube videos of homebuilt CNC routers I think I've spotted another problem: the spindle drive.

    Most people seem to be using spindle motors that spin really fast and are directly attached to the collet (either a dremel tool or a special-purpose spindle motor). I can see two problems with this approach: first is the side load put on the motor bearings, and the other is just the problems you get with high-speed brushed motors.

    Industrial milling machines are belt-driven, as are prosumer "Mini Mills". What I'm thinking of doing is something similar to the Mini Mill: have the motor on the spindle head, but connected to the spindle via a belt and a stepped pulley (to get different speeds). The motor itself would be a three-phase induction motor driven by a variable frequency drive.

    Anyway, let me know what you think. One decision I've not made yet is how big this machine is going to be. Obviously it won't be as small as the test prototype, but I would like a reasonably small machine.
     
  2. David the swarfer

    David the swarfer OpenBuilds Team
    Staff Member Moderator Builder

    Joined:
    Aug 6, 2013
    Messages:
    916
    Likes Received:
    414
    a - build a big machine, you need space for the tool and the clamps/vice.
    b - research 'SFM' and 'feeds and speeds for steel' so that you know the range of spindle speeds you will need.
    Also research how much horsepower you need for cutting steel.
     
    Peter Van Der Walt likes this.
  3. Joe Eagar

    Joe Eagar Well-Known
    Builder

    Joined:
    Feb 5, 2018
    Messages:
    3
    Likes Received:
    1
    That's a good point about the tools and the vice. For the motor I was thinking I'd start at 3/4 hp and go up from there. I'd like to be able to run this on less than 1500 watts if at all possible.
     
    David the swarfer likes this.
  4. Rick 2.0

    Rick 2.0 OpenBuilds Team
    Staff Member Moderator Resident Builder Builder

    Joined:
    Dec 20, 2013
    Messages:
    1,720
    Likes Received:
    754
    Steel reinforcing doesn't do anything for concrete until it cracks. But once it cracks the system won't be of much value anymore as now you'll have vibration in the system. If you're only looking to do small pieces, I suggest converting a Harbor Freight Mini Mill to CNC.
     
  5. Joe Eagar

    Joe Eagar Well-Known
    Builder

    Joined:
    Feb 5, 2018
    Messages:
    3
    Likes Received:
    1
    I admit I have trouble believing that too, which is why I built the prototype to test. I've not done so yet, but I can already tell that just the mass and stiffness of a concrete frame is going to help, even if it turns out not to dampen vibrations like people said it would. On the mini mill, I may end up doing that, but what fun is that :)
     

Share This Page

  1. This site uses cookies to help personalise content, tailor your experience and to keep you logged in if you register.
    By continuing to use this site, you are consenting to our use of cookies.
    Dismiss Notice