Current Research Area
Product
Complexity
During the manufacturing analysis of a product, special
attention must be paid to the shape complexity. Current analyses
require the designer to follow manufacturing process charts, but
these are mainly subjective.
Complexity
Part
count reduction vs. Complexity
Current DFA methodologies encourage part count reduction, but
care must be taken to ensure that benefits of reduced part count
are not outweighted by manufacturing costs of the new
components.
Shape Complexity
Classification of parts during the DFA/Manufacturing
Analysis
ANALYSIS OF SHAPE COMPLEXITY
Shape complexity overview
The starting point for the redefinition of shape complexity is an
appraisal of the fundamental purpose of the DFA Manufacturing
Analysis. The written definitions and terminology used to describe
shape complexity offer more insight into this purpose than the
shape complexity categories themselves. These definitions,
extracted from the Lucas DFA methodology are as follows:
Basic Features – Straight forward processing
where the operation can be carried out without a change of setting
or complex tooling. Usually parts are uniform in
cross-section.
Secondary Features – As above but where additional
processing or more complex tooling is necessary.
Multi-Axis Features – Parts require to be
processed in more than a single axis/set-up.
Non-Uniform Features – Parts require the development of more
complex processing techniques/set-up.
Complex Forms – Parts need dedicated tooling and
the development of specialised processing techniques.
Single Axis – This is usually the axis along the
components largest dimension. However, in the case of cylindrical
or disc-shaped components, it is more convenient to consider the
axis of revolution as the primary axis.
Through Features – Features which run along,
across or through from one end or side to the other.
Although still somewhat vague, these descriptions highlight the
fundamental principles of the Manufacturing Analysis, which relate
manufacturing difficulty to the number and complexity of the
manufacturing processes required.
Manufacturing factors
The difficulty of particular manufacturing processes is related
to the shape complexity of a component. The number of additional
processes required to achieve a specified tolerance or surface
finish is then dependent on the primary manufacturing process. The
difficulty in producing a component using a particular
manufacturing process is also dependent on such factors as the
component material and the minimum section thickness.
In DFA, these factors, together with other factors relating to
material cost and the scale of production, are combined in the
calculation of a ‘Manufacturing Index’ to enable a simple
comparison of alternative designs.
Computer-aided complexity classification
In summary, the difficulties and costs associated with component
manufacture are directly related to the number of types of
manufacturing process required, the number of faces requiring each
manufacturing treatment and the number of tool or orientation
changes required during each phase of the manufacture. The
following rules can be inferred, which correspond to this premise
and can be implemented in an algorithm:
Shape complexity is related to the number of...
- Types of face,
- Different face orientations,
- Levels in the face hierarchy
Figure 1. Shape complexity approach