RE: [CAD_CAM_EDM_DRO] Positioning

You know, I think all of this needs a dose of reality.  Most people building DYI CNC machines don’t put enough strength and mass into the base to warrant any positioning closer than +/-.0005 and most should be in the range of +/-.001.

Without a strong, rigid and massive base on which the machine is built, the machine will deflect more than the scales will vary.

High speed and heavy cuts will move the Z axis more than that.

So, if you think about it, to get to anything less that +/-.001, you need to make massive, stable equipment.  Be sure nothing deflects.  The temperature in your shop doesn’t vary much and your fixturing doesn’t allow movement of the part.

After all that, worrying about using glass scales that are good to +/-.005, +/-.001 or +/-.0005 seems to be moot.

Seems to me that people are worrying about the wrong thing.  Most pictures of DYI CNC machinery have weak frames and weak axis connection points…I haven’t seen any that featured press fit cross keys to maintain axis orientation and position nor have I seen any that had massive steel frame work with ground and scraped pads for mounting surfaces.  None of the discussions about frames have even mentioned stress relieving or how to mange to square the frames except with a tape rule (+/-.015 at best).  And no where have I seen an discussion about how to level that frame except with a carpenters four foot level…no precision level or layer system.

The position of the carriage being +/-.001 or .0005.  LAUGH OUT LOUD.  There are other issues that need to be dealt with first.

R. Wink