--- In mach1mach2cnc@..., "mlaws1172" <mlaws1172@...> wrote:
Seeing how i haven't asked any stupid questions for a while, i thought
it was time
What would best amount of steps to go for on a servo driven table
(Plasma) as far as Mach is concerned. Is there an amount that mach
does best at?
mike
Your (current) number should be based on the highest target speed (in
IPM) calculated to how many pulses per second it takes to do that.
It's a function of the "gearing" and the line count of the encoders.
Encoders with higher line counts require more pulses per second to go
a certain speed. Run the numbers and plug in the max 45,000 pulses
per second that the parallel port version does.
Wildcard: Gecko's and Rutex have built-in step multipliers that can
be used to get around the limits.
Basically the raw resolution (not particulary the accuracy) of a
machine is the smallest distance one pulse will move it. Obviously
the smaller the distance the better the resolution HOWEVER unused
resolution is just wasted money. A plasma tabel with .005 accuracy
(considering all the mechanical inaccuracies) is sufficient. A
resoltuion of greater than 10 times the final accuracy is plenty.
Most builders find that motors with 250 to 500 lines (1000 to 2000
pulses per rev with any level of belt reduction gives them plenty of
resolution. Encoders with higher counts quickly make the math such
that either faster pulse rates than parallel can generate OR step
multipliers have to be introduced.
Example. A servo with a 1000 line encoder puts out 4000 pulses (in
quadrature) each rev of the shaft. If we use rack and pinion and a
gear that moves 1" per rev (easy math). If the belt reduction is a
common 4:1 the pulse count per inch is 16,000. Lets say our target is
300 Ipm (5 IPS) then we have to put out 80,000 pulses per second to
get there....well past what we can provide with a parallel port. With
the above system your resolution is .00000625 inches. Lets say the
motor is rated at 3000 RPM so a belt reduction of 4:1 makes that 750
PRM and since it moves one inch that equates to 750 IPM.
I won't go further but you have several choices and each one effects
other parameters.
