Re: [CAD_CAM_EDM_DRO] abrasive grit on machine ways

Carlos:
I spent almost two years straight in the Moore Tool factory during 92 and 93
integrating a custom CNC control for Los Alamos on an 18 axis machine for
machining High Explosive for nuclear weapons. We were required to have 10
millionths total global deviation including control position hystersis and
mechanical deflections in a 24 inch working cube for these machines. Moore
spent over two years straight scraping in two of these machines. Their
craftsmanship is beyond comprehension. The reason that you don't see covers
and so forth is that they create a minute amount of drag on the system.
That drag can amount to a deviation of a few millionths of mechanical
deflection in the machine. A few millionths here and a few millionths there
and you have exceeded your .0001 accuracy standard. By the way. The final
lapping of the lead screws (actual lead screws, not ball screws) is done
completely by hand in a temperature controlled room. The technician laps on
the screw for a few minutes in the morning and then the screw is placed in a
special rack to prevent it sagging. The accuracy of the few lap strokes is
checked the next day after the "heat" of the lapping has been removed by
resting the screw for 24 hours. The process is then repeated. This can go
on for a month or more until the screw finally meets specs. Also, you will
never find cleaner machines in a medical operating room. They deserve their
reputation for being one of the most accurate machines in the world.

Dan Symonds