Re: um, is the (Chinese scale) dro acting wierd?

This is indeed a problem with the Chinese scales.
They are quite sensitive to noise (poor grounding, long unshielded
cables...)
A jump of 0.200" is just one bit flipping in the scale, since they
count 0x5000 (hex) counts per inch. I have seen this as well on
several occasions.
It's quite annoying, but at 0.2" you at least have a chance of
noticing it.
There is a good chance that it skips other distances as well that you
might not notice, but that will still ruin your part.
Is there any correlation when it jumps to something you are doing,
like turning on the spindle?
This stuff is hard to deal with, since you don't know if it's fixed
for good after you add lets say a cable shield or change the routing...
Klaus

--- In CAD_CAM_EDM_DRO@yahoogroups.com, fignoggle <david@f...> wrote:
>
>
> i just noticed this the other day when drilling a series of holes in a
> plate.
>
> all measurements were spec'd, i just had to read off the dro to get my
> locations.
>
> after the second hole going onto the third, i noticed that what i was
> about to drill did NOT match up with the dro reading. it was off. so i
> stop and check my math, etc.. this happened all throughout the
operation.
>
> same operation yesterday and noticed it again after zeroing x and y.
> knowing that something was wierd, i ran the axes to random points to
check
> before i started drilling.
>
> and then the strangest thing. i saw the dro literally jump by .200" by
> itself. WTF? it happened all over the place and ONLY in the y axis.
from
> 1.000 to 0.800., etc..
>
> so, is this my scale? dro? cable?
>
> you can see the setup at my site. it's the chinese scales and dro
like you
> see at lathemaster.com.
>
> thanks!
>
> --
>
> here's the hf mini mill dro/cnc mod!
>
<http://www.fignoggle.com/~fignoggle/hFCn66Ghejx8Jwia3Kl32ReQ/themachine/>