1575
« on: June 22, 2014, 08:10:53 AM »
Keith,
Just some more info for what it's worth as this pertains to resolution.
RESOLUTION
Resolution is just an indication of how fine the A axis system will turn the spindle per step.
Typical stepper is 1.8 degree ( 200 pulses for 1 rev ), most folks micro step ( say a value of 10 ),
and then it is a matter of how much gear reduction takes place ( lets use 72:1 ).
Steps in one revolution= 200 motor pulses X 10 micro steps X 72 = 144000 steps per revolution
Steps in one degree = 144000steps per rev / 360 degrees per rev = 400 steps per degree
Theoretically with just a single pulse sent to the motor you would have the following:
Resolution = 1 / 400 = .0025 degrees ( which is equal to .15 minutes = 9 seconds )
Practically speaking, due to backlash, variances in the gears / belts / motor or whatever, you will not get that kind of movement in one pulse / step.
The following is an example of different combinations:
+ - RESOLUTION
# MOTOR MICRO STEPS GEAR RED STEPS / DEGREE DEG = MIN = SEC
1 200 -NA- NONE .5555 1.8
2 200 10 NONE 5.555 0.18 10.8
3 200 10 72 400 0.0025 0.15 9
4 200 10 135 750 0.00133 0.08 4.8
5 200 10 200 1111.1 0.0009 0.054 3.24
Here are some angular to linear relationships:
ANGLE PER INCH PER 3" PER FOOT
1 SEC .000005" .000014" .00006"
30 SEC .00014" .00044" .0017"
1 MIN .00029 .00087" .0035"
Here is just one aspect of resolution to linear positioning and can be envisioned by the following example.
Lets assume that you are going to index the spindle and drill some holes out 3” from the center of the plate.
So if you were to drill a hole out from the center 3", then index 3 min, and drill another hole,
the distance you have between the holes would be approx 0.006” for no gear reduction.
RICH