5. Comparison of CMM & UMM
CMM UMM
It is useful for rapid inspection
of production parts.
It does not inspect that much
fast.
It does not inspect Geometric
features of the part.
But UMM does it.
It is not accurate. It is more accurate than CMM.
Reveals the failure but not
reason.
UMM useful in this regard.
It is useful for Quality control. It is capable of resolving the
exact nature of the error of all
part features, regardless of
complexity.
6. INSPECTION ON UMM
Essential that the work piece should be
mounted carefully on UMM.
Measuring the location of hole.
Measuring of awkward shaped work pieces.
Use of Microscopes for measuring small size
holes.
7. MECHANICAL ACCURACY
Attainment of “cubic concept” of accuracy in
the UMM requires the individual mastery of
four mechanical arts- Geometry, Length,
Dividing of Circles and Roundness.
These are truly the “Foundations of
Mechanical Accuracy”.
8. Geometry
Flat plane.
Meehante cast iron(close grained).
Elastic deformation-minimised-design and
support.
Temperature differentials affects the accuracy.
Localized heating and cooling causes
unpredictable distortion.
9. Standards of Length
Internationally acceptable standards.
Accuracy of derived length-standards such as
gauge blocks, precision scales, step gauges,
lead screws, and laser interferometer
depends in large measure on how truthfully
they represent the ultimate length standard.
10. Dividing the Circle
Authority of “angles” of angle gauges, rotary
tables, or the angular relationships in
mechanical parts and assemblies is derived
from the self-proving principle of dividing the
circle
11. Roundness
Precision machine tools must achieve
roundness and especially with their spindles.
Location, effective size and fit between mating
parts are all dependent on the ability to
measure and define the conditions of
roundness.
