Re: [CAD_CAM_EDM_DRO] Measurements to compare machines

Agreed a Ballbar test result would be very interesting. Unfortunately not everyone has one of these $4000 - $9000 devices. Heck they cost more than many peoples entire workshop.

On the other hand, a dedicated home shop machinist could actually
MAKE a ballbar tester fairly easily.  You need an encoder for one of the
ends to pick up the rotation angle, and a ball and socket end for
the other.  You need a bar that can slide in and out, just a close-fitting
rod in a tube.  And, you need to hack up a tenths-reading dial
indicator that attaches to the rod and tube, and put a tiny encoder
where the dial pointer goes.  Then, connect the two to a computer
interface with two encoder counters.  Another way to do the length
measurement would be an LVDT with a board to read that in.

Jon