1. #1
    I have been asked by one of my friends how I intend to counterbalance the spindle.
    as when another Axis is travelling it may drop and leave ribs showing.

    Has anyone done this Or do you rely on the drive to hold the spindle in position.

  2. #2
    Quote Originally Posted by ramsbury View Post
    I have been asked by one of my friends how I intend to counterbalance the spindle.
    as when another Axis is travelling it may drop and leave ribs showing.

    Has anyone done this Or do you rely on the drive to hold the spindle in position.
    No doesn't happen and if you have the correct size motors the holding torque is enough.

    If you have a very heavy Spindle then having a counter balance will help the motor but it's still down to the motor to hold it unless you have a break on the motor.

  3. #3
    Having a counterbalance can reduce the required holding and lifting torque & current but increases the mass which the motor must accelerate for downward motion and so increases lowering torque & current.
    Ideally any counterbalance should be about tuning the system, as Jazz said the motor should be up to the job of holding if correctly rated.
    Counterbalancing is a widely used technique in industry to allow systems to deal mainly with motive forces, to minimise static forces and to improve safety by ensuring a system doesn't move out of control in the event of power loss,

    - Nick

  4. #4
    Quote Originally Posted by JAZZCNC View Post
    No doesn't happen and if you have the correct size motors the holding torque is enough.

    If you have a very heavy Spindle then having a counter balance will help the motor but it's still down to the motor to hold it unless you have a break on the motor.
    Once upon a time, many years ago I worked at a place which had a large vertical boring m/c, the spindle weighed 7 tons and was c/balanced with a large iron casting via a rack and pinion system. Apprentice left in charge wound the spindle up past the end of the rack. Felt the earth move a quarter of a mile away.

  5. #5
    Quote Originally Posted by johnsattuk View Post
    Once upon a time, many years ago I worked at a place which had a large vertical boring m/c, the spindle weighed 7 tons
    Just to illustrate why worrying about the spindle dropping when the motor is powered, on your average CNC router - with a 5mm pitch ballscrew and 1:2 ratio you'd only need 28Nm holding torque to support that 7 ton spindle.

    It's fairly typical for people to use a 3Nm motor on their Z-axis, with a 5mm pitch ballscrew and 1:1 ratio, in which case the motor can support about 370kg (T=F*L/2pi). This also demonstrates why setting the stepper motor to 50% when idle is generally acceptable - half of that holding force is still plenty.
    Last edited by Jonathan; 06-01-2014 at 04:02 PM.
    Old router build log here. New router build log here. Lathe build log here.
    Electric motorbike project here.

  6. The Following User Says Thank You to Jonathan For This Useful Post:


Similar Threads

  1. Chinese 300W DC spindle - is the spindle shaft grounded?
    By HankMcSpank in forum Spindles & Drive Motors
    Replies: 44
    Last Post: 26-11-2016, 07:25 PM
  2. Replies: 0
    Last Post: 13-11-2013, 07:50 PM
  3. Spindle lock mechanism for 2.2kW china spindle
    By Jonathan in forum Generic Chinese Spindles
    Replies: 8
    Last Post: 13-08-2012, 08:39 PM
  4. WANTED: Spindle holder for 1.5kw Chinese spindle.
    By jcb121 in forum Items Wanted
    Replies: 19
    Last Post: 14-10-2011, 02:07 PM
  5. DIY Spindle - What type of bearings are best suited for a spindle.
    By 8iggles in forum Spindles & Drive Motors
    Replies: 18
    Last Post: 09-02-2011, 10:15 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •