3D Computer-Aided Design

Question 1

EXTRUSION

Answer 1

Extrusion is when you ADD or SUBTRACT material from a shape. An extruded shape can then be rendered to show materials, shadows, reflection and perspective.

Question 2

REVOLVE

Answer 2

Revolve is when a sketch is rotated around a central axis. You must emphasis how much the revolve is by.

Question 3

LOFT

Answer 3

Loft allows you to create a range of shapes with different cross sections joined together. You must use a work plane for each profile. If the loft has a twist in it, you edit where the corners lead to in the sketches.

Question 4

EXTRUDE ALONG A PATH

Answer 4

This allows you to form a solid along a sketched path. A sweep blend is when you use a combination of lofting and extrude along a path.

Question 5

HELIX

Answer 5

This creates a spring like solid. It can have an irregular path or angled path. It also has a pitch.

Pitch is the size between the helix gaps.

Question 6

INTERSECTING FEATURES

Answer 6

It is possible to create a solid by overlapping two solids. This idea of intersection is the point/shape where the two blocks cross.

Question 7

SHELL

Answer 7

Shell is used to hollow a solid object. You just mention the wall thickness. You can also remove faces.

Question 8

FILLET

Answer 8

A fillet will round of an edge of a solid. It can be applied to an internal or external edge. Measured in radius.

Question 9

CHAMFER

Answer 9

This will add an angled edge to a solid:. It can be applied externally and internally. You can set the size of the angle and size.

Question 10

MIRROR

Answer 10

It allows a component to be created with the exact same shape being on the other side. Symmetrical. Thus allows the company to edit the overall length of the shape whilst maintaining symmetry.

Question 11

ARRAY

Answer 11

Radial array - you can repeat a feature onto a shape in a circular pattern.

Linear array - you can set a feature to be repeated along a line with a set distance between them.

Box array - repeating a feature along the x axis and the y axis to give a box pattern.

Curve array - it allows a feature to be repeated over a curved path.

Question 12

CONSTRAINTS

Answer 12

CENTRE AXIS
This is when circular objects are aligned along a central axis. It is useful when inserting a circular object into another.

MATE
This makes faces touch each other.

ALLIGN
It places faces on the same plane. They are next to each other on the same plane, rather than meeting each other lined up.

OFFSET
This allows you to set a distance between two features.

TANGENCY
This allows for curved faces to touch each other at one point only.

Question 13

ASSEMBLIES AND SUB ASSEMBLIES

Answer 13

An assembly is when two or more parts have been put together to create a model of an object.. this are created from components. Exploded views can be created from these to show how pieces fit together. Parts can also be animated to further show how parts work.

A sub assembly is an assembly file which is placed into another assembly file.

Question 14

CAD LIBRARY - components

Answer 14

This is a collection of pre-made cad models which can be accessed through the web. They save time and effort and means the user doesn’t have to create all the parts. It also ensures that components are all identical.

Question 15

3D CAD VIEWS

Answer 15

Solid model : provides a realistic view of a CAD model. Any decals or colours can be added. They are poorer quality than a fully rendered final versions.

Rendered models : they provide highly realistic views of 3D models which can be used in advertising. It will often be placed in a suitable environment to enhance the look of it. Shadows, highlights, reflections and textures are all added to create a realistic graphic.

Wireframe : this can be useful when wanting to see the structure of the model. It can be more difficult to understand the shape in wireframe rather than solid objects, but it shows internal detail better. They can help the CAD user to build complex models and ensure all the parts fit together.

Question 16

RENDERING TECHNIQUES

Answer 16

Setting different light sources (brightness and colour can be edited), showing reflections and shadows, placing the model in a suitable environment. The material used in a model can affect how strong the reflections are and the lighting.

Question 17

WHATS A FACE, EDGE, AND VERTICE

Answer 17

A face is a flat or curved surface of a model.

An edge is where two faces meet at an angle.

A vertices is the point (corner) where two edges meet.

Question 18

BOTTOM UP MODELLING

Answer 18

When an object is created by, making the component pieces and then assembling them.

Question 19

TOP DOWN MODELLING

Answer 19

This is when different parts of a 3D model are built within an assembly around an existing part. This is useful when working with library parts.

When you build the main body then later add more, you used the project tool when freeing parts in intact as you can use lengths from the previous shape. When creating the new model within the previous model, you can grey out the other models when dealing with a new part.

Question 20

MODELLING TREE/ HIERARCHY

Answer 20

A modelling tree or hierarchy shows the different stages when producing a 3D CAD model. It is a useful tool as you can edit specific parts of the model without having to restart the entire things. This speeds up the process of developing graphic and provided the opportunity to make real time changes the product. It can also allow you to t to move some features so that they occur earlier or later in the model which is useful when dealing with the shell command.

Question 21

MODELLING PLANS

Answer 21

A modelling plan helps a user to create a 3D model. It should show the sizes used for the sketches and features and in which order the model was created.

Question 22

CAD FILE TYPES

Answer 22

dxf - this is a file extension used by AutoCad for drawings.

3ds - this is a 3DS Max file for renders.

STEP/IGES - they can be used in any 3D CAD package. This makes them useful when sharing files between other users. IGES are an older type of generic 3D CAD file formats. They don’t have the same features and information stored in them such as the volume of an object. STEP files have taken these over.

stl - it is a stereolithographt file.bit converts a mathematical file of the 3D CAD model into triangles. This allows the CAD model to be physically produced using rapid prototyping or CAD/CAM techniques.

Question 23

CAD LIBRARY - shapes and symbols

Answer 23

Is is a collection of commonly used shapes or symbols. They help the user in a number of different ways. They save time and effort as the user doesn’t need to redraw each shape. They also ensure that the British standard symbols are used. The ensure consistency of parts and drawings.