I work for a transport trailer flooring manufacturer. We make floors
for your
typical box trailer and overseas shipping containers. These floor
panels are
generally 1 foot wide x 1 1/4" thick x 24-53 feet long.
These panels are made by gluing 1" x 1 1/4" hardwood sticks of varying
lengths
into panels.
These panels are pressed and cured in sections of 16' at a time. (@3
minutes per
press.) When the desired length is reached, the panels are cut to
length, and
fed through a profile planer.
During the pressing operation we get occassional bends (or waves) in
the length of the panel so that if you stand at the end of the panel,
you can
see that the edge of the panel may not be perfectly straight.
Our customers allow a 1/4" wave in the panel over the 53'.
We have previously tried placing a laser along the the length of the
panel after the press so that the press tailer could visually spot the
panel
wave.
This did not prove as successful as we would have liked since the
panels did not
remain as rigidly aligned as needed after the press, and the tailer had
difficulty monitoring the laser along the 50'+ span. Also as you are
well
aware,relying on human judement is never as consistant as needed.
I had hoped that we could put air gages after the tooling in the planer
to
detect if the panel pulls away from the fence. Unfortunately, there are
so many
rough edges and joints along the edge that I don't believe air gages
would
work.
Regardless, I would like to go to my boss with a solution to a problem
that has
plagued this company for years, has caused the loss of customers in the
past,
and is upsetting our current customers. It just seems that since no one
here is
able to come up with a solution, they are resigned to damage control
instead of
finding the solution.
Your advice would be greatly appreciated.
Aaron Palmer
hershal 7/30/2002
One last point.......hopefully your calibration provider is accredited to ISO/IEC 17025......helps you to have confidence in their competence.
Hershal
hershal 7/30/2002
Cscramuzza has a good answer. Monitoring the process with external (to the machine) gages will satisfy the ISO 9K requirement. There are two rules of thumb I suggest: (1) How likely is it that NOT calibrating will result in non-conforming product? If there is a significant risk of non-conforming product if the equipment gage is not calibrated, then calibrate it. And the second point, taken from a Metrology point of view, (2) is the measurement qualitative or quantitative? If it is a quantitative measurement, then calibrate it. If it is a qualitative measurement (only used as a state indicator, reading makes no difference at all), then no need to calibrate.
Hope this helps.
Hershal
cscramuzza 7/30/2002
I work for an ISO certified company and we have made a rule of thumb that we calibrate a gage if its reading result in a decision regarding the quality of our product. In other words we may calibrate it if its an important aspect of the process and a wrong reading would result in incorrect adjustments, which result in bad product, but for the most part, we rely on the the quality measurement gages to make all of our quality decisions on the in-process or finished products, rather than those on the equipment, since our processes do change and it doesn't matter how its set up, as long as we're producing good product. In a round about way, I saying that you have to decide how stable your process is and if its worth doing SPC the way its meant to be done in which case, calibrate your equipment gages, otherwise stick to the quality gages for calibration.