Re: [Emc-users] Cable drive for a gas torch pattern follower?

[Gene H. <ghe...@wd...>]

On Saturday 30 March 2013 17:32:05 cogoman did opine:

> On 03/26/2013 01:21 AM, Gregg Eshelman wrote:
> >> I am not sure you will see good acceleration. In fact, it is
> >> 
> >> >always
> >> >going to be less than 1g. This is because for any faster
> >> >acceleration
> >> >the strings go slack as the weighs don't fall fast enough.
> > 
> > No need to go anywhere near that fast because an oxy-acetylene torch
> > or plasma cutter can't cut that fast. This rig is most often used for
> > cutting steel 3/4" thick or thicker.
> 
>    Since counter weights are often used on Z axes on servo machines, I
> once decided to calculate how much of a limit the acceleration due to
> gravity would be.  The metric calculations are left for you folks across
> the pond.
> 
> Acceleration due to gravity = 16 feet/second/second
> 

Uhh, when I went to school back in rural IA, in 2 feet of snow, uphill 2 
miles both ways, gravity's acceleration was 32 feet per second per second.  
Did I go to the wrong school?

> After 1 second the velocity can be 16 feet per second
> 
> times 60 = 960 feet per minute (I love spreadsheets!)
> 
> times 12 = 11520 inches per minute
> 
> divide that by two, so half of that force can be applied to your cable =
> 5760 inches per minute
> 
> HERE'S WHERE I AM MAKING ASSUMPTIONS THAT MAY BE OFF BY A LITTLE.
> 
> If I recall properly 1500 inches per minute is a FAST servo system.
> 
> 1500/5760 = .26 ( assuming linear acceleration it should only take .26
> seconds to reach 1500 IPM)
> 
> 1500/60 = 25 inches per second
> 
> at 25 inches per second that servo system would travel 6.5 inches at
> full speed while the gravity system would be accelerating to 1500 IPM.
> Of course the servo system wouldn't be able to accelerate
> instantaneously, so the counter weight would only slow a 1500 IPM servo
> system down a little bit.
> 
>    I thought gravity would be much more of a limit too.
> 
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Cheers, Gene
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