On 06/25/2017 08:48 PM, Jon Elson wrote:
On 06/25/2017 06:51 PM, andy pugh wrote:
On 25 June 2017 at 15:21, dave <dengv...@charter.net> wrote:
I suspect that this is a thermal problem
Whereas I consider the idea that it is a _Computer_ thermal problem
almost
inconceivable.
Yes, for a CPU to foul up ONLY the counting of one axis in ONE
direction seems implausible. I'm guessing possibly a weak encoder
that is losing counts when hot. I'd also check the power supply to
the encoder as close to the encoder as it is available.
I did have a problem with my mill some years ago. I did a couple
things wrong on one job and didn't notice the hole spacing was off
until the parts were used. One error was I didn't spot the holes, I
just drilled them with jobber's length drills, so all bets on accuracy
would be off, anyway. But, the holes were too widely spaced. Hmmm,
many errors in the machine would cause the holes to be too CLOSE
together. Then, I noticed the spindle speed display was fluctuating.
I started to investigate. On my PPMC system, the encoder board powers
the encoders through the encoder connector.
I saw that the encoders had about 4.0 V where it should have been 5.0
+/- 5% or so. The main DC connector to the PPMC motherboard was
making a poor contact, and the whole PPMC system was running on about
4.1 V! Amazing that it even worked at all, as that was WAY outside
the VCC spec for all the chips. Once I wiggled the connector,
everything returned to normal.
So, the error was due to one encoder losing counts, so the machine
moved farther than it should have. It was pretty repeatable, so the
error did not accumulate.
Jon
"Yes, for a CPU to foul up ONLY the counting of one axis in ONE
direction seems implausible."
I agree!
We have two separate issues. In my original post I listed too many
problems which leads to context confusion when replying.
The thermal issue is in reference to the out of limits when the part was
clearly in the middle of the workspace. The machine simply didn't know
where it was.
I suspected the shifting axis issue was a broken helicoil; it has
happened before. Not in this case...
I dismounted the encoder and old fumble finger dropped the mounting
assembly. One encoder ruined.
I did find a break in the encoder connection on the A+ channel so that
explains the shifting.
Will install a new encoder today so one problem should disappear.
Re': ppmc. The whole connector system was weak. IIRC I soldered the
power connections and that
fixed that! Also I constructed a solid Al bracket for the data
connector. Once it was bolted down I never had another problem...rock
solid. I could run the communication diagnostic for hours or days
without an error.
Back to the soldering station...........
Dave
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