Re: Encoders: on servo or on guideway?

Hi Peter,

If you look at the machine you are using, you should be able to see
the difference. The drive system, no matter how precise has a number
of "interfacing" points; couplings, drive screws, and slides. Each
one of these can add an error, no matter how small. If you use a
linear encoder on the machine axis you will be after all the
accumulative errors in the system; assuming the spindle or tool
holder do not have any slop. What you are doing is increasing the
precision

Obviously if you can afford it, you want the most precise machine
available, and on some machines you will find both rotary encoders on
the servo motors, and linear encoders on the machine axis.

Another way you could look at the problem is manual machining using
the dials to position a part or cutter, as opposed to using a digital
readout (or direct measurement). If you have a brand new Hardinge
toolroom lathe you can be pretty sure the dials will be more precise,
but if you have an old worn Atlas, you might not want to trust them.
If both have a set of good linear encoders, and you read off of
them, the chance is you will have a more accurate part. With my old
worn Atlas (no readouts), I will use more hand measurement, and can
still make a part as accurate as the Hardinge, but it will take me
longer.


In CAD_CAM_EDM_DRO@yahoogroups.com, "peterboutakis" <peter@b...>
wrote:

> Which is better? An encoder that is incorporated into the linear
> guideway or one that is part of the servo motor?
>
> There is a company called Hiwin that sells an "intelligent" linear
> guideway system which has the encoders built into the guideway

rail.

> Is this better?
>
> Thanks, Peter.