CAD Commands, Components and Conventions

Designing on screen

Computer aided design has replaced the drawing board across the construction industry. Learning the tools once lets you draw accurately, edit freely and share work with ease. This module works through the toolkit: - Why CAD: speed, accuracy and easy editing.\n- Commands: the draw and modify tools you use most.\n- Components and hatching: standard building parts and material fills.\n- The workspace: working full size, and model space against paper space. Producing the scaled drawings and sections themselves is covered in a separate module. Here the focus is the CAD commands, components and conventions.

Words for CAD

Five terms you need before you use them. Learn what each one means.

Match each CAD command to what it does

A draw command against a modify command

Every CAD tool falls into one of two groups. Knowing which is which helps you find the right tool quickly.

Which is a modify command?

In CAD, which of these is a modify command rather than a draw command?

• Trim, which cuts an object back to an edge
• Line, which draws a straight segment
• Circle, which draws a round shape
• Rectangle, which draws a box

Tap the two modification commands

Tap the TWO commands that modify an object rather than draw a new one.

• Trim
• Stretch
• Line
• Circle

Showing materials with hatch patterns

A CAD drawing is not just lines: it also shows what each part is made of, and that is the job of hatching. A hatch pattern fills an area with a standard fill so a reader can tell the material at a glance. Different patterns stand for brickwork, blockwork, insulation, concrete and hard core, and using the agreed patterns keeps every drawing clear and consistent. It also helps to know your workspace: you build the drawing full size in the model area, then lay it out ready to print in the paper area. Keeping the two separate keeps the work tidy and accurate.

Pick the true facts about CAD

Select the TWO statements that are true.

• A hatch pattern shows which material a part represents
• Modify commands change objects that already exist
• CAD drawings must be entered at half size
• The line command is a modification command

Order how to set up and start a CAD drawing

Put the steps of setting up and starting a CAD drawing in a sensible order.

• Open the software and start a new drawing
• Set the drawing environment to full size
• Use draw commands to create the shapes
• Use modify commands to edit them
• Add hatch patterns to show the materials

One wall detail on screen

Follow how a student built a cavity wall detail on screen.\n\nSetting up: she opened a new file and set the workspace to full size, so every measurement was entered at its true value. Building the shapes: she used the line and rectangle tools to lay out the two leaves of the wall and the gap between them, then the offset tool to add the wall ties at even spacing. Tidying up: where lines overran she used trim to cut them back cleanly, and move to nudge parts into place. Showing the materials: she filled each part with the correct fill, one for brickwork and another for the insulation in the cavity, so anyone reading it could tell the materials apart. Working full size on screen, she could zoom in to check the fine junctions before laying the sheet out to print.

Complete the CAD facts

Using software to create accurate drawings is called _____. A command that creates a new object, such as a line, is a _____ command. A command that changes an object already there, such as trim, is a _____ command. A fill that shows which material a part represents is a _____ pattern.

Build a CAD point

Choose the words that complete this statement about CAD commands.

The CAD run

Five questions on CAD commands, components and conventions. Three lives.

Choose the right command

Read each situation and choose the best CAD command, then think about why.

• You need to shorten a line so it stops exactly at another line. Which command?
• You need several parallel lines an equal distance apart. Which command helps most?
• You want to show that an area of the drawing is insulation. What do you use?

Explain how CAD is used in construction

A classmate is new to CAD. Explain how it is used in construction using what this module has covered.

• Explain what CAD is and why it is used in construction
• Explain the difference between draw and modify commands, with examples
• Explain what hatch patterns are for
• Explain what it means to work in the model area at full size
• Finish by explaining one advantage of CAD over drawing by hand