Re: [CAD_CAM_EDM_DRO] Encoders for the G320

Gecko's read the encoders in 4X mode so that if your encoder has 200 lines
it will yield 800 counts (which for a G320/340 is equivalent to a step) per
revolution. When picking encoders for a Gecko step and direction servo drive
you have to consider a couple of factors and more is not always better. The
first thing to look at is the expected maximum travel speed you are
designing for and what that translates into as steps/second. For instance if
you are using a 2:1 belt reduction on a 10 turns/inch screw with a 200 line
(800 count/rev) encoder that will give you 16,000 steps per inch. Now if you
plan to have rapids at 120 ipm you will need 32,000 steps/second. Is the
computer and controller package you are planning to use capable of that
pulse rate? If not you need to use lower resolution encoders (assuming the
reduction and screws are all ready fixed). The other thing to consider is
your calculated increment per step. in the above example it is .0000625". Is
that even sensible for your machine. Probably not as mechanical issues will
keep most machines from ever moving in that small an increment.

Hope that give you a little bit of an idea on what you need to do to pick a
good usable encoder count. I like to aim for a step increment of about
.0001" - .0002" and find it works out pretty well for me.

Tim
[Denver, CO]
Sherline products at Deep Discount
and Mach1 CNC controller
www.KTMarketing.com/Sherline

----- Original Message -----
Dear Sirs,

The doc´s from the G320 say I need an encoder of at leas 200 lines.
I'm unsure on how that relates to CPR, I guess it is the same. If
it is the case, I guess I should just go for the highest for better
resolution. Is this correct?

Thanks,

Arturo


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