CAD Flashcards
What is top-down modelling?
One part of the model helps to make the next part of the model by projecting either features or sketches.
The Top-Down Modelling approach helps to ensure that all components fit together in the modelling stage.
Advantages of top-down modelling:
It is an efficient way of modelling because it is more accurate when complex parts are involved in the modelling.
It ensures parts fit together at the modelling stage without the need for constraints.
It speeds up the process of CAD Modelling.
When a size in a part is changed, the sizes in the components that share this sketch also change.
Top-down modelling allows you to project geometry from other parts.
Top-down modelling allows parts to be modelled in situ and will not need constraints to assemble.
What is bottom-up modelling?
Each part of a model is made individually and saved as an individual component.
All components made using Bottom-Up Modelling require to be placed into an assembly.
Constraints are required at the assembly stage for Bottom-Up Models.
Any changes to a component will need to be done by editing it individually.
Disadvantages of bottom-up modelling:
Geometry (including sketches and dimension) and features are not shared or transferred between parts.
It takes more time to model and assemble component parts using Bottom-Up Modelling.
When a size needs to be changed, the sizes in all the components using the sketch need to be changed individually.
What is the modelling tree?
The modelling tree shows the CAD Technician the process that has been followed to make their CAD Model.
Advantages of the modelling tree:
The CAD Technician can edit sketches and features already made, meaning they do not have to remake the model if a mistake is made.
It allows parts of the model to be suppressed to increate ease of editing.
What are CAD libraries?
CAD libraries are the backbone of 3D Modelling on companies. Most products are creates using ‘Standardised components’ that are saved into one large library. Any CAD Technician can access these to ensure consistency across all models produced by the company. It also speeds up production time as not all parts have to be made entirely from scratch.
Advantages of a CAD library:
Reduces time to model each component.
Reduces the chance of CAD Technicians making errors.
Represents actual standard component parts.
The same component parts would be used by all CAD Technicians in the company
Library of components can be used by CAD users worldwide.
Things to include in radial array:
Sketch of shape (with sizes)
Axis of Resolution.
Number of feature
PCD (Circle the Radial Array follows).
Things to include in box array:
Sketch of shape (with sizes)
Pitch (distance between shapes)
Number of Rows.
Number of Columns.
Advantages of vector file formats:
Scalable without pixelation/loss of quality.
Colour can be changed within DTP software.
Small file sizes.
Advantages of raster file formats:
High resolution images allow for photorealistic images to be saved as each pixel can be a different colour allowing for subtle changes in colour.
Allows for rich and detailed images due to use of pixels over shapes.
Do not require specialist software to open so can be used almost anywhere and on any device.
Explain the term sub-assembly:
Components create an assembly that is used within another assembly.
Types of sections:
Revolved (rotated 90 degrees)
Removed
Stepped Section (cuts through two planes)
Half Section
Part Section
Full Section
Sectioning of threads:
When hole is occupied: section to outside line
When hole is unoccupied: section to inside line
When bolt is half-inserted: section to outside line for the part that is occupied and inside line for when unoccupied
Things that aren’t sectioned:
Nuts
Bolts
Webs
Axels
Shafts
Types of constraints:
Mate
Align
Centre Axis
Orientate
Offset
Types of views:
Exploded, sectional, orthographic, detailed
Isometric, oblique, planometric, one point perspective, two point perspective
Purpose of a detailed view:
Gives a larger view of a specific area allowing for greater clarity in the view.
Purpose of an exploded isometric view:
Shows how the parts fit together.
Shows how many parts there are.
Allows someone to see how to assemble the object.
Allows someone to see the order of assembly.
How to answer a helix question:
Draw the profile and a centre axis. Set the distance of the profile from the centre axis.
Use the helix command, set the pitch, revolutions and taper.
How to answer an extrude/sweep along a path question:
Draw the profile of the shape.
Create a perpendicular workplane and sketch the path the profile should follow.
Use extrude or sweep along a path to make profile follow path.
How to answer a loft question:
Create a workplane and draw initial sketch.
Create new workplane and offset it required distance from first workplane.
Draw profile of new workplane.
Use loft feature between the first and second sketch.
Explain tangency:
When two circles/arcs connect at a single point.
When two circles/arcs connect but do not overlap.
The smooth transition from one arc to the next.
The smooth transition from an arc to a straight line (or vice-versa).
Advantages to the designer of using digital sketching instead of manual sketching:
The sketches could include realistic material representations.
Further illustration techniques can be applied to enhance the initial sketch.
They can be built up in a series of layers to ease editing.
They are automatically stored electronically and do not require scanning to upload to the website.
Sketches can be exported into other packages.
A wider range of tools/brushes are available.
Easy to share through cloud services or email.
Library of resources can be utilised.
Accept ease of editing as sizes can be changed quickly through the modelling tree rather than having to re-draw a full sketch manually.
Benefits of using rendered 3D CAD illustrations to show design concepts to a client:
Photo real image of how the product will look.
Realistic representation of materials.
Useful for users who cannot read or interpret 2D drawings.
Rendered CAD pictorials can be sent out to users via email.
Alternative versions showing different colours or finishes can be quickly and easily created.
Light sources can be simulated.
Purpose of a sited environment:
A rendered scene that places an object in a physical setting/environment.
A rendered scene that places the object in a specific context and gives a greater sense of believability.
A rendered scene that uses the surrounding environment to show how products appears in light/sunny/dark conditions.
Gives a sense of scale.
Can show DTP work in realistic setting.
To give an idea of the ease of readability/clarity in a sited environment.
No need to print full-size samples.
Benefits of using cloud computing:
Cloud computing gives the ability to work remotely which allows ease of collaboration.
Companies working on a project across different locations can give access to the same files which ensures they work from the most up to date versions.
Cloud computing allows employees to be more flexible in their work practices in terms of the ability to quickly and easily access data at any time.
Cloud computing systems are regularly updated making sure the latest versions of software is being used.
Cloud computing can allow access to more high spec. servers which will allow for a higher quality output.
Can be accessed on multiple devices or platforms.
Portable devices with less storage capacity can access the information as items will be saved in the cloud, not the device.
Benefits of using 3D CAD models in manufacturing:
3D models can be used to directly manufacture (CNC/CAM).
To enable dimensions to be extracted from the CAD model, without production drawings.
3D models can be used to show how complex items are assembled.
3D models do not need a manufacturer to interpret complex production drawings.
Production drawings can be created and fully dimensioned from the CAD model.
Allows for a range of tests to be undertaken prior to manufacture.
Why a drop cap can be used to enhance the readability of a document:
Highlights the starting point of a piece of body text so that the reader knows where to start reading from.
Emphasises the start of each piece of the body text which makes the document easier to follow.
Contrasts in size with the rest of the body text which draws attention to the paragraph.
Consistent use of the drop cap in each piece of body text creates rhythm which helps guide between sections.
