What is Computer aided design?
Computer aided design, is the use of computers to create, analyse, or modify a design. In addition, 3D digital files can be emailed to any CAM manufacturers, for instant fabrication. 3D CAD files can also be used for product visuals and rapid prototyping. Furthermore, it can even be used to conduct force simulations. That is to name a few applications.
CAD is mainly used for detailed engineering of 3D models, or 2D drawings of physical designs. A CAD file is a blueprint design file which drives computer controlled machines (like a 3D printer or injection mold press). A typical computer aided design file will include 2 vital elements. Firstly, a 3D shape of your object, accurate to a fraction of mm. Secondly, in the 3D software you can preview the design in the 3d environment, rotate it, zoom in, view cross sectional and so on.
Above is a picture with a CAD model on screen being developed by our CAD designer.
On the right is that same 3D file but you on your screen.
Hold down click on mouse to move and rotate the models perspective.
try scrolling on your mouse wheel to zoom in and out.
How does CAD design work?
2D shapes are used with the primary feature forming operations. Generally, 3d forms are made up of, or start as a 2d shape. With most parametric solid modelling, forms are built from 2d sketches using the 6 primary forming operations as shown below.
Extruding is the primary forming operation. It involves taking a flat 2d sketch and extruding it up so it has a thickness.
Cut extrude is the opposite of boss extrude, it involves using a flat sketch to cut material from a thickened shape.
Revolve boss allows us to take a flat sketch and rotate it around a center to create a solid shape.
Sweep boss takes a flat sketch and extrudes it along a path. Can include guide curves to manipulate the uniformity
Loft emboss takes 2 separate flat sketches and joins them together with a often curved and unique surface.
Boundary boss is very similar to loft boss however it can join open open paths as well as closed flat shapes.
The model below was built using all 6 primary feature forming operations…
join the 2d circle
and square base
using a single
2d sketch and
sweeps it along
spiral path to
create solid bar
takes a sketch split
vertically down the
center. the 2d sketch
is revolved around
the center axis to
create solid shape
a solid body joins
the 3 separate 2d sketches in the stem of the design
Added guide curves
can manipulate the
outer surface profile
for a more freeform
This is the inverse operation of boss extrude. Cut extrude is cutting material away to create a circular array of holes the base platform of the model
Computer aided design for 3D printing
CAD design gives great freedom, in the design stage of product development. However, design for 3D printing carries rules which must be followed. likewise with injection molding draft angles, or CNC path considerations. Otherwise, you will experience printability issues. Generally, The most important elements to consider are: layer height, shrinkage and warping, supports and fillets. You can find descriptions of each for FDM, SLA and SLS on thier respective pages.
There are also a range of common 3D printed features. Each of these, are affected by the above elements. Also, each feature has differing minimums and maximums depending on the printing method used. Furthermore, not all features apply for each printing method.
Common 3D printed features
Minimum thickness for walls that are connected on two sides, to lower the chance of warping.
Minimum for walls that are connected to just one side, is higher. Due to higher chances of warping.
The minimum angle that a wall can be printed without the need for supports.
The minimum feature height or depth, imprinted or recessed into the model. There is a chance these details will fuse with the rest of the model if they are too small.
Connected/ moving parts
The maximum bridge length that can print succesfully without supports.
The minimum hole diameter that can be succesfully printed.
Recommended clearence based on a required fit.
The minimum size of an escape hole, to allow removal of build material.
The minimum thickness of any feature in order for it to be printable.
The minimum diameter a pin can be succesfully printed.
The maximum length of overhanging features.
The expected dimensional accuracy of a specific printing technology.
The maximum ratio between a prints vertical height and the part cross section, to ensure stability on the build plate.
CAD design and Product development.
To begin with, you draw a computer aided design model, to visualise its form. Afterwards, 3D Printing is used, to carry out form fit and function tests. After a few back and forth amendments, to the computer aided design file, a functional prototype will be the result.
In the later stages, the CAD design file is used to make 3d art work for marketing. Furthermore, it is the file you send to a manufacturers, to receive quotes. In addition, CAD files are used to communicate building works to a contractor. You see where I’m going with this, making almost any product these days requires a CAD file at literally every step of the way for hundreds of different reasons.