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- Dimension - Tolerances - Assemblies - Coggle Diagram
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Dimension
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Tolerances
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Assemblies
Dimension
How
Dimension text
units in mm, bottom conner of the drawing
Tolerance
(+-) is the tolerance, the dimension is allowed to deviate
Dimension Line
an arrowhead on each end
Extension Line
continue/extend from the surface of the object
establish the size of the dimension
do not touch the object line and extend slightly
Extension Line Offset
a gap between the object surface and the extension line, not confused with the visible lines of the model
Type
Parallel Dimensioning (Datum Dimensioning)
consists of several dimension originating from a common reference surface (also known as the 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 accumulation of the tolerances.
Combined Dimensioning
uses both chain and parallel dimensioning.
Dimensioning Small Features
Placing arrow heads between the extension lines may take the dimension very difficult to read. Arrow heads can be placed outside the extension lines instead.
Dimensioning of multiple Features
To dimension multiple same dimensions, use
N x Dimension
.
Dimensioning of Radius
Centre of the radius located on the drawing
do not need their centres locating
Dimensioning of Circle, Arc, and Hole
Dimensioning Angles
degree ^0 symbol
Rules
not be duplicated
exp same dimension should not be repeated on difference views/same information need not be given in two different ways
Avoid dimensioning to hidden lines and features
Dimension lines, extension lines and object outlines should not cross/overlap
Tolerances
Importance
parts cannot be manufactured exactly to the dimensions stated in the drawing
due to manufacturing variations
dimensions in engineering drawing to take into account these manufacturing limitations.
Why
If tolerance is not given, exact measurement of the parts must be made. Rejection rate will be very high and is not realistic
The range of the tolerance will translate into the manufacturing method needed, since different manufacturing method has different degree of tolerance.
Same parts can be made from different companies and they have to be interchangeable. Tolerances ensures good quality control for parts form different companies
Tolerance will unsure that mating, parts of an assembly interface and fit well
Type
Bilateral Tolerance
allowed to
vary in two directions
from the specified dimension. Both directions need
not
vary by the same amount
Unilateral Tolerance
allowed to vary in
only one direction
Limit Tolerance
the upper and lower limits of the dimension are specified
Calculating
Tolerance = Upper limit - Lower Limit
Assembling Multiple Parts
in order to bring a product to life, very often, multiple parts and components are needed
Clearance Fit
allowance for two parts to move, such as in a door hinge
2.Interference fit
difficult to move (or remove) the two interfacing parts. Usually, a lot of force is needed to remove the two parts.
What is Assembly Modelling
assembly model, multiple parts are brought together
collaboration among designers, engineers, manufacturing technicians and etc
different disciplines can work concurrently, resulting in faster and less costly delivery of products to market.
How
bringing in a base component
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 in Fusion 360
Rigid
Revolute
Slider
Cylindrical
Pin Slot
Planar
Ball
Rigid Joint
fixes two components to one another; it provides no degrees of freedom
Revolute Joint
has a single rotational degree of freedom, much like a hinge