Re: [CAD_CAM_EDM_DRO] Re: setting up the CNC mill

> snip
> > Do you mean that if you execute G01 X-1 and G01 X+1 once it returns to
> > almost 1.000 but is off by some small delta, but if you repeat this many

The other possibility (other than missing step) to consider is that a

> sprocket or coupling might be slipping on a shaft. Set screws are simply
> not reliable...snip

I have had one common predictable variance in movement that happens every
time I do one thing, the amount it shifts is exactly the same each time and
it took me two years to finally just sit for four hours and repeat it enough
times to measure the amount, the cause and figure out an solution.

When I get a reason to stop my machine for more than a minute or two but do
not want to hassle reloading the program, maybe I had made a edit to it and
have not saved it yet and the phone rings or some one comes by, I don't want
to quit in the middle of a run of parts, I usually work fours hours straight
then stop for rest and maybe do another two. I am using an Emco CNC5 lathe
for all my production runs and have been for several years. So here is what
happens. I enter G64 which makes the steppers go currentless, no need
burning them up, they may be junk motors I have heard it from more than this
group too, but they work flawlessly for me. But after the visitor leaves or
the phone call ends or whatever the interruption was...if I just start
making parts again and it could be two minutes or forty five, the part will
be predictably .002" smaller. If I before running the part first time adjust
it out .002" it also will invariably be .004 to big!!!! What the hell is
that all about??

Well I once thought it was the cooling off of everything and once it got
back running it sort of warned back to right size. Nope it would ton all
these rest of time .002"undersize. So I just manually move the tool post
with the manual move button i the Z axis. I don't touch the X axis, somehow
a mystery to me but I can make the motors under current again, not adjust
the undersize issue .002" but just get into power mode by moving the
carriage +Z a few thou, back to 0, hit the play button(start, sorry I get
mixed up when I am rocking and rolling if this is the boom box or the
heavily beefed up CNC5, more later if anyone wants to know how to make a
standard CNC5 better without a full conversion) and sure enough it will be
on the money and I finish the run. Any ideas from anyone why this occurs?? I
thought as I said it was a cooling off thing, I even tried having a lamp I
put on the work/ways/toolpost til I got back but it was not it. I spent four
hours testing it again and again and it just "creeps" when I go currentless.
Johnno