dimensions, tolerances, assemblies
parallel dimensioning
originating from a common reference surface
superimposed running dimension
simplifies parallel dimensions to reduce space used on a drawing
chain dimensioning
combined dimensioning
used if the function of the object would not be affected by the accumulation of tolerances
uses both chain and parallel dimensioning
why must include tolerance in dimensions
if no tolerance, there must be exact measurement of parts. rejection rate will be high and not realistic
ensures that mating parts of an assembly interface and fit well
types of tolerances
bilateral tolerance: vary in two directions from specified dimension. directions need not vary by same amount
unilateral tolerance: vary in only one direction
limit tolerance: upper and lower limits of dimension are specified
assembly modelling
multiple parts brought together to define a more complex product representation. facilitates the collaboration among designers and engineers to ensure a product assembly works, able to work concurrently, resulting in faster delivery of products to market/
how assembly modelling work
each component brought in are oriented and located relative to other components in assembly. assembly joints are used between elements of components.