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.