Re: motor sizing vertical slide EDM

Mariss,
Your's are alway more complicated ;-)
(math & physik challenged here )

>Message 7
> From: "Mariss Freimanis" mariss92705@...
> Date: Thu May 11, 2006 8:54am(PDT)
>Subject: Re: motor sizing vertical slide EDM
>
>TomP,
>

i f a = v/t then the 40 mS is the t
and i was just looking at the linear acc of the driven axis
never looked much at the motor ( rotary) itself

>Not quite sure how to reconcile "15Krad/sec^2" with "40mS response
>time" and "8X acceleration that I stated".:-)
>

arrg radian ( tomp looks up radian... think it's like 56 degrees or so yeh?)
yeh 57.295, angle subtended by circumference equal to the radius....
so 15000rad/s^2
is near 262 revs/sec^2
meaning, a blurr, and a real kick when it accelerates... ok

>I use 15Krad/sec^2 as very respectable acceleration goal on a
>servomotor. This reflects a very good motor torque to inertia ratio.

ok, so it's a cap

>This value is motor-bound in that all mechanism acceleration rates
>will be limited to or below this value.
>

2"/sec = 120"/min ok
I'm thinking I can direct couple now
looking at R+W http://www.rw-couplings.com/

>You said the goal is 2"/sec on a 5TPI screw (600 RPM) reduced from
>the motor's 3,000 RPM via 5:1 reduction.

no more 5:1 see above, just truncate the top rpm and take the slow
speed response and full torque at lower velocity range ( whatever's
left over after getting the best slow speed response )

>

Yep, the acc time would be 1/2 my design limit ( thats good )
(I hoped for 40 and you say 20, kewl )

>Using that accel rate, the motor will take 21mS to reach 3,000 RPM.
>The linear velocity will go from 0 to 2"/sec in the same period of
>time if I understand your mechanism correctly.
>

this math is all new to me..
v = 120"/min
t = 21ms = .021S
a = v / t
= 120 / .02
no, in seconds.. ( inches per seconds and acc time in seconds.. )
= 2 / .021
= 47.61904761904762 ???
anyway, the same magnitude area where you were..

>Solving for "a" (a = v / t) gives 95.5"/sec^2 or 0.249 G (G =
>384"/sec^2).
>

but it seems to be .126G ( 47.5"/S^2 / 384 )
huh? what happened to the 9G slam we had yesterday??

>The power needed to accelerate a 700lb mass at 0.25G to velocity of
>2"/sec is only 39.5 Watts, the energy invested is only 0.83 Joules.

0.83 joules! ???
1 joule = 1 watt second
= 100V at 1 amp for 10mS
ssome magnitude problems here (likely on my end )
but the jist is
the motor I suggested before is WAY outta line, right?

>
>Mariss

thanks
TomP