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Flywheel and rotozip physics help needed — Parallax Forums

Flywheel and rotozip physics help needed

metron9metron9 Posts: 1,100
edited 2010-01-06 04:19 in General Discussion
I am well on my way to finishing a 12 x 12 CNC machine that I plan to use a rotozip on.

My question to the physics people here is would a flywheel be a benifit for slower speed cutting.

Typically I cut 6061 aluminum at 500 to 1000 rpm on my Bridgport and it cuts like butter wit zero chatter.

My thought on the rotozip is that reducing its speed with a speed controller will also cut its power.

Using a 2 inch x 1/2 inch flywheel would allow more current (more power) to drive the motor at a slower speed and also help absorb vibration of the cut.

I have a guy that can make me a flywheel but do you think this might work, any merit to the idea or am I just thinking too hard.


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Comments

  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-01-04 08:19
    I doubt the flywheel will help. At speed, whatever it is, the power you put into it has to at least equal the power you want to get out, in order to keep the flywheel at a constant speed. If you can't provide enough power at low speed without the flywheel, you won't be able to provide enough with one. I would suggest a lower RPM motor if you plan to cut metal.

    -Phil
  • ElectricAyeElectricAye Posts: 4,561
    edited 2010-01-04 15:00
    metron9 said...
    ...



    Using a 2 inch x 1/2 inch flywheel would allow more current (more power) to drive the motor at a slower speed and also help absorb vibration of the cut....

    Generally speaking, a flywheel is used to store mechanical energy in a system but the flywheel can "output" that energy for only a short while. A flywheel is analogous to a capacitor in that respect. The flywheel is used to smooth out mechanical motion, so it might help with phenomena like chatter during a cut. But as Phil points out, the flywheel is not going to give you power "in the long run" if your system can't pump it in somewhere in the cycle. For example, you would not expect a capacitor to pull energy out of thin air: at some point the capacitor needs to get "recharged" during operation.


    hope that helps,
    Mark
  • CannibalRoboticsCannibalRobotics Posts: 535
    edited 2010-01-06 02:56
    Yep, and keep in mind that if it gets slowed down by a cut the motor has to not only spin up the bit again but the flywheel too.
    Flywheels are typically used to maintain constant speed, or to store up energy for impact.
    They don't do much for power.

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  • James LongJames Long Posts: 1,181
    edited 2010-01-06 03:28
    One problem that I think of which isn't mentioned here is gyroscopic effect. The bearings near the flywheel (if it is used) better be able to handle the gyroscope tendency to tilt if the head moves. Moving a mass in rotation will cause the mass to try to tilt.

    If the head is stationary, there shouldn't be many problems. The bit moving will do the same thing but in much less magnitude.

    James L

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  • Phil Pilgrim (PhiPi)Phil Pilgrim (PhiPi) Posts: 23,514
    edited 2010-01-06 03:57
    Moving a flywheel without tilting the axis of rotation doesn't introduce any apparent counteracting forces. It's when to try to tilt the axis of rotation that these forces come into play.

    -Phil
  • James LongJames Long Posts: 1,181
    edited 2010-01-06 04:19
    Phil Pilgrim (PhiPi) said...
    Moving a flywheel without tilting the axis of rotation doesn't introduce any apparent counteracting forces. It's when to try to tilt the axis of rotation that these forces come into play.

    -Phil

    Phil,

    Yes you are right. I was mistaken. The tilt of an axis will cause a offset movement 90 degrees from tilt.

    James L

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    James L
    Partner/Designer
    Lil Brother SMT Assembly Services

    Are you addicted to technology or Micro-controllers..... then checkout the forums at Savage Circuits. Learn to build your own Gizmos!
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