Re: [CAD_CAM_EDM_DRO] Re: Solid coupler from motor to ball screw?

In a message dated 2/24/2003 8:06:13 AM Central Standard Time,
davemucha@... writes:

> motors, at least the ones surplus and e-bay are not designed for axial
> loading of the forces for even small tables.
>

Further: SURPRISE! Regardless of catalog-text, the "GRANDFATHER" of stepper
motor manufacturers in USA does NOT use SEALED ball-bearings for their
expensive new steppers! In a dusty operation such as wood-turning, these
steppers will "freeze up" in short order, and one must either VERY CAREFULLY
replace the bearings with DCC types, or buy all-new motors, so the fun can be
repeated! We ALL know opening a stepper in the "home shop" often means its
demise! I once wrote that firm, asking how much more $$ to get DCC bearings,
and they replied about how much of an impostion this would be on their
routine, and all that, and it nearly would have DOUBLED the cost-per motor,
even if I supplied the desired bearings! (Keeping track of serial-numbers in
process is beyond the mentality of the folk they hire up there, I guess?).

In small CNC machines with these steppers, I have used "deep-groove" bearings
on the opposite end of lead-screws where I have depended upon the actual
motor-bearings as support for the "motor end" of the screw. This works for
SOME applications, but much better would be "angular-contact" bearings at
BOTH ends of the screw, preferably SEPARATED by about three
bearing-thicknesses with a precision-turned spacer between the bearings'
inner races. Then, of course, one would HAVE to use some kind of compliant
coupler such as Helical spiral or Servometer SS bellows, etc.

Just work carefully with as much "common sense" as you have at your disposal!
Lotsa hard-won Experience helps!

Jan Rowland


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