NMM3540 Development of Dimensional Measurement
Metrology
Case Study Assignment
for MSc
Hand
–
in date:
See assignment cover sheet
Please read this assignment specification
very
carefully before beginning
your work.
It is also
recommended that you re
–
read it
once the report is nearing completion.
Aim:
This
assignment
requires consideration of the
issues relating to the
practical use of a measuring
instrument and the
use of metrology in a
hypothetical
production environment and how factor
s such as
measurement
resolution,
accuracy
, equipment, environment,
training,
costs and time
–
scales
,
etc
.
have to
be considered in the choice of measurement
equipment and
strategy
for its use
.
The Company
task
:
A
manufacturing company produces precision components for machinery
such as mining equipment
and
also for the railway industry
.
They
must
implement new
measurement
systems in a number of different
areas within the company. The
re is a need for increased quality and traceability to satisfy customer
requirement and reduce
sc
rap and
re
–
working
.
The company currently has a metrology room with good temperature control
of +/
–
1°C
which is ke
pt
clean
.
The room contains a
Coordinate Measuring Machine (
CMM
)
with a
large
working
volume;
however
i
t
has
limited additional
inspection
ca
pacity
available in its operation schedule. There are also two oth
er
areas
on the shop floor
that have basic inspection facilities such as steel flat plates, height gauges, callipers
and indicators. These areas
do not have temperature control and
currently
,
cleanliness
cannot be
guaranteed, however
they do have spare
capacity
.
Measurement tasks and
dimensions
This section details the various
components
and measurements that need to be included in the
Company
improvement regime:
1.
Analysis of captured data and
appraisal of the
measuring
instrument
.
D
uring the practical laboratory sessions at the beginning of the
Dimensional Measurement
course
,
you used a
measuring instrument to measure a simple component.
These are the items and the data
that must be considered
in this task.
Data analysis
, uncertainties
,
manual
calculations
,
plots and
discussions are mandatory to
explain
trends in
the
data.
2.
Regular batch measurement
of
20
bearing housing assemblies.
Each assembly ha
s
2
holes
with diameters
of 10mm, 16mm, 24mm,
and 50mm
. The diametrical
tolerances range from +/
–
1
0µm to +/
–
4
5
µm
.
It is not necessary to record the actual tolerances, just
know whether they are
IN
or OUT of
tolerance.
Comments on the selected equipment must be made
in order to estimate its suitabilit
y for long term usage.
3.
Regular batch
measurement of 5
long
cylindrical
shafts.
The shafts
are
800mm
in length and are used in high speed rotating machinery therefore they must be
straight along their length
to a
tolerance
of +/
–
36
µm.
The shaft diameter ch
anges in several places to
incorporate bearings etc. These distances between the
shoulders
also have a tolerance on the
dimensions
that is
1
6
µm/100mm.
Data from the measurements is to be used in statistical process
control charts
as part of predictive
main
tenance
strategy
on certain production pr
ocesses
.
Consider
that the existing CMM capacity is limited therefore provide
an alternative measuring
solution
(use
illustrations
where required
to describe any bespoke measurement setup designed
)
.
4.
Small quantity/
1
–
offs of high
value bespoke pump assemblies.
The assemblies are quite complex with a
r
ange of features
to be
measured.
All dimension
al
data
needs
to be recorded. Tolerances are all to the ISO standard
s such as ISO 286
–
2 (1988
).
The relevant data has
been
extracted from the standard and attached
.
Your assignment:
Imagine you have been appointed project manager for these tasks in the company. You must prepare a
concise
report outlining a suitable strategy to ensure that the stringent demands of measuring hig
h quality
components will be met in all respects.
For measuring task 1:
Provide a
detailed
analysis of the measured data to show the capability in terms of resolution and
repeatability. Include in your discussion the procedure for using the instrument, fac
tors that contribute to
uncertainty and how they may be minimised or controlled. Include an
appraisal
on t
he suitability of the
measurement device
, with reference to any alternatives where necessary,
for inspecting small batches
of
components against
speci
fied component tolerances.
For measuring tasks 2 to 4:
These are new measuring tasks for the company and a strategy is required to complete them.
There is
scope for investment within the company to ensure that
,
in the long term
,
the company can remain a
m
arket leader for precision manufacturing
and measurement
.
Care must be taken to consider cost
s
associated with purchasing new equipment
and return on investment.
Production
and inspection
timescales must be kept to a minimum but not at the expense of out
–
o
f
–
tolerance parts reaching the customer or excessive scrap during manufacture.