Re: [CAD_CAM_EDM_DRO] Re: machine inaccuracies fixed by software compensation

That calculates out to +/- 2.77777...% per step (based on a 1.8 degree
movement per step). If movement is taken from the starting point each time
the motor moves then operating the motor one step at a time for 200 steps
(360 degrees) it appears to me the total error would be much gtreater than
2.777.% Plugging the figures into X cell for 200 steps gives a total
movement of 360 +/- 10.0 degrees...which also just happens to be +/-
2.7777...% per revolution. This would represent a loss or gain of 5.5555...
steps per 360 revolution at max deviation if the motor were operated only
one step at time (not ususally done I'm sure).

However, if the theoretical stopping point is always based on one of the
stopping points dictated by the 1.8 degree step division, then the maximum
error deviation over 360 degrees would only be .0138888....%. (3 minutes
deviation /360 degrees). Obviously this figure would be reduced even more
for movements greater than 360 degrees.

Does this muddy the water even further? :)

Smoke

> "STEP ANGLE ACCURACY
> Under no-load conditions the stepping motor can maintain a step angle
> accuracy within +/- 3 minutes (.05 deg). This slight error arises from
> difference in the mechanical precision of the stator and rotor teeth and
> variations in the electrical precision of the DC resistance of the
> stator coil.
>
> STOPPING ANGLE ACCURACY
> This refers to the difference between the rotor's theoretical stopping
> position and it's actual stopping position. A given rotor stopping point
> is taken as the starting point, then the stopping angle error is the
> difference between the maximum (+) value and the minimum (-) value when
> measuring each step of a full rotation.
>
> <actual stopping position>
>
> .745 1.425 2.17 2.885
> 0----------|-X-----X-|--------|-X-------|X-------(etc)---360
> .72 1.44 2.16 2.88
>
> | = Theoretical Stopping Position
> X = Actual Stopping Position

>
> Jon