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Dimensions,Tolerances and Assemblies - Coggle Diagram
Dimensions,Tolerances and Assemblies
Dimensions
Types of Dimensions
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Chain Dimensioning
Should only be used if the function of the object would not be affected by the accumulation of the tolerances
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Dimensioning of radius
'R' states Radial Dimensions.
shows a radius dimensioned with the centre of the radius located on the drawing.
Shows how to dimension radii which do not need their centres locating
Dimensioning of Hole, Circle, Arc
A circle is dimensioned by its diameter
An arc is dimensioned by its radius
Holes are located by their centrelines
Dimensioning Angles
It is marked with with a curve dimension line, has degree symbol.
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Tolerances
Importance of Tolerances
Tolerances are included with dimensions in engineering drawings to take into account of manufacturing limitations.
Types of Tolerances
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Bilateral Tolerance
vary in two directions from the specified dimension. Both directions need not vary by the same amount.
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Assembly Modelling
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How does it work?
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.
Types of Joints
Slider
a single translational degree of freedom. It is used for components that slide along one another. Options are similar to revolute joint options, except that components slide along the selected axis rather than rotating around it
Cylindrical
provides two degrees of freedom: one translational and one rotational. Components joined with a cylindrical joint always rotate around the same axis.
Revolute
a single rotational degree of freedom, much like a hinge. This joint can rotate around the standard X, Y, or Z axis, or around an edge in the model (a custom axis).
Pin slot
allows two degrees of freedom, but components can rotate around different axes.
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Ball
has two degrees of rotational freedom: pitch and yaw. Pitch allows components to rotate around the Z axis. Yaw rotates components around the X axis.
Planar
allows three degrees of freedom. It allows two directions of translation in a plane and a single rotational direction normal to that plane. It is useful for joining two components so they can rotate while sliding across the plane.