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L06 Dimensions, tolerances and assemblies - Coggle Diagram
L06 Dimensions, tolerances and assemblies
Dimension
How to dimension
Dimension text: Base dimension (mm) Units usually not indicated on every dimension text, but at the bottom corner of the drawing
Tolerance: +/- 0.2 is the tolerance, it defines how much the dimension is allowed to deviate
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Extension line: It continue or extend from the surface of the object and establish the size of the dimension. They do not touch the object lines and extend slightly past the dimension line.
Extension Line Offset: A gap between the object surface and the extension line, so it is not confused with the visible lines of the model.
Types of dimensions
Parallel Dimensioning(Datum Dimensioning): Consist of several dimensions originating from a common reference surface(Datum)
Superimposed Running Dimensioning: Simplifies parallel dimensions in order to reduce the space used on a drawing
Chain Dimensioning: Should only be used if the function of the object would not be affected by the accumulatio of the tolerances.
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Dimensioning small features: Placing arrow heads between extension lines may make the dimension very difficult to read. Arrow heads can be placed outside the extension lines instead.
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Dimension of circle = diameter, Arc = Radius, Holes are located by their centerlines.
Rules of Dimensioning
Dimensions should not be duplicated, i.e. same dimension should not be repeated on different views, or the same information need not be given in two different ways
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Dimension lines, extension lines and object outlines should not cross or overlap
Tolerance
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Types of tolerance
Bilateral Tolerance: allowed to vary in two directions from the specified dimension. Both directions need not vary by the same amount.
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Clearance fit: there would still be an allowance for two parts to move, such as in a door hinge.
Interference fit, it would be difficult to move (or remove) the two interfacing parts. Usually, a lot of force is needed to remove the two parts. Examples are shafts that are fitted through bearings, so that the shaft does not slip.
Assembly Modelling
In an assembly model, multiple parts are brought together to define a larger, more complex product representation. Assembly modelling facilitates the collaboration among designers, engineers, manufacturing technicians and others to ensure a product assembly works. Individuals in different disciplines can work concurrently, resulting in faster and less costly delivery of products to market.
Constructing an assembly normally begins with bringing in a base component, selected because of its central role. Each component brought in needs to be oriented and located relative to other components in the assembly. Assembly joints are used between elements of components.
Joint
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Revolute Joint: Has a single rotational degree of freedom, much like a hinge.