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drafting in plan _ tutorial 07 .
 

Drafting details is an exercise in communicating a design as clearly and unambiguously as possible. While the drafting itself is not particularly creative, there is considerable skill required to include the relevant information in an ordered way that can be understood by a range of people. Normally your starting point will be sketches done by your self on site, or given to you by an office senior.

The standard of drafting and level of information will vary greatly; your challenge will be to turn documents like this.

 
 
 
 

Into documents like this:

 
 

It is very important to understand that an autoCAD drawing is an editable transferable, and interchangeable digital document. So it is very important that you set up and draft documents using an appropriate quality assurance system as described in the first part of this course. Students who set up and draft properly save time and effort in the long term, have fewer panic moments, emotional upheavals, unprovoked assaults on keyboards, and generally produce better work in less time.

For the purposes of this weblog, there are a number of abbreviations for common commands: (for example RC means click the right button on your mouse), these are designed to help you to learn the language of autoCAD as well as introducing you to the commonly used actions of the keyboard and the mouse.

RC = Right click
LC = Left click
LCH + Left click and hold the button down while dragging the cursor across the page.
Esc = press the escape button top left corner of the keyboard.
F3 = turn the object snap on/off
F8 = turn the ortho projection on/off
F1 = turn the Help function on/off
Enter = the enter key
PS = paper space
MS = model space
Cons = use a construction layer which can be seen on the screen but not on the printed page.

To begin you should take the chance to indulge in a little self learning. So familiarise yourself with the screen in front of you by doing the following exercises:

Drafting tools

Hover over each of the buttons on the tool bars above and to the right of your screen to see what their function is.  Try a few of the shapes buttons to draw shapes on the screen. LC to select the icon, LC to start the shape/line and LC to select the next point RC and enter to finish (if it is a multi point tools such as polyline).

Many tools appear on your screen as part of a default set up for your program. If you hover over any of the tools and RC you will notice a long list of other tools bars available to you. The ones to fiddle around with include; (those ticked are default on the screen) Dimension, Draw, Inquiry, Modify, and Object snap, Properties, Standard and Zoom. To find out more use F1.

Ortho and Osnap functions

Read the tabs at the bottom of the screen and go to F1 to find out what they do. Note at this stage OSNAP and ORTHO are the most useful.

Zoom control on your screen.

The best way to zoom in and out on your screen is to roll the wheel on the top of your mouse. If you can’t find your drawing on your screen use zoom extents (F1 to find out how to access the various zoom functions including Zoom extents)

Construction lines

Use construction lines (in a construction layer) to create guidelines on your image to make sure you accurately draft your shapes. Note construction lines are infinite straight guidelines that are not designed to be used for drafting.

Practice using OSNAP (F3) and ORTHO (F8)

It is most effective when you are familiar how to control the OSNAP blue “grip” squares. RC over the OSNAP tab, and select settings (LC) you will notice a toolbox with a range of types of “grips” can be activated. Turn some on or off and hover over your title block and see where the blue “grips” appear. Also use the osnap tool bar, to be able to select individual osnap commands.

Ortho is much easier, if ortho is on your cursor is restricted to moving in four directions (up, down, left, right). This is very useful for ‘measuring line lengths by entering the exact starting and finishing coordinates of a line.

Selecting items on the screen.

If you hold the cursor on top of an item LC you will select an item. If you LCH from the top left to the bottom right over the black screen you will create a square with a solid line which is blue in the middle. This will allow you to select a item that is entirely within the selecting (blue) square.
If you LCH from the bottom right to the top left over the black screen, you will create a square with a dotted line which is green in the middle. This will allow you to select an item that is partially within the selecting (green) square. Practice selecting items on a square.

Using the RC drop down list.

After you select an item and RC, a drop down short cut box with a list of commonly used commands appears. They are categorised into 5 sections. Familiarise yourself with the various actions available to you, however the most useful are repeat last action eg: if you have just drawn a polyline it will show repeat polyline. The second most useful is the copy selection command (half way down). The other one is the last one which brings up the properties tool bar. This allows you to view the properties of any element on the screen. These “properties’ can be modified from this tool bar.

Tutorial 1: Drafting in plan

1. Drafting the rectangle (The footing)
The footing will be a concrete slab which is 1200mm x 1200mm which will be represented in plan view by a rectangle.

 
 

Using the cons layer select the polyline tab mand specify your start point at 0,0 by typing it in. Make sure your ortho is on (F8), you will notice the cursor is restricted to moving up/down, left /right. Move the cursor to the right and type 1200 then enter. Move the cursor up the screen and repeat the action, and press RC and select enter. (Note the polyline has an infinite number of points so you will need to RC to bring up a list of commands to modify the line including enter which finishes the command.) You should have a backwards L shape on the screen.

 
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(Use a build layer green) Select the rectangle tab and making sure OSNAP (F3) is on and ORTHO (F8) is off. Allow the cursor to hover over the top of the backwards L, (when the blue square appears the line will automatically “grip” to that point, then LC and move the cursor to the bottom right of the backwards L then LC. (Note the rectangle requires only two commands so it doesn’t require a right click to complete.)

You should have a yellow square that measures 1200 x 1200 when you finish.

 
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2. Drafting the circle (The oven floor)

The oven floor, which will sit on top of the base, will be a circular concrete slab which will be represented in plan by a circle with a 565mm radius.

Create construction lines (use cons layer) that make a diagonal cross on your square. Select construction line (under line button or xl on keyboard) and hover over the top right of the square then LC and move to bottom left of the square (LC) and RC to finish. Repeat the action to create a cross. Repeat the action to create a vertical construction line to dissect the rectangle by selecting the intersection point and moving your mouse vertically then LC.

 
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In the build layer select the circle button (or c on the keyboard), and LC where the construction lines cross to specify a starting point. Move the cursor to the top of the rectangle and type 525 in the command line to specify radius of the circle and hit enter.

 
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3. Drafting a polyline (The oven base)

The oven base will be made of concrete blocks (200x200x400), it will have a 200mm wide opening at the front to store wood. It will be represented by a complex polyline, which will show the thickness of the block walls (200mm) and the width of the openings (also 200mm). You will need to use construction lines and the offset tool to set up guides so that you may be able to accurately trace the base shape in plan view.

Offset the vertical construction construction line by clicking the offset button (or o on the keyboard) and then enter 100 as the offset distance. Click the construction line and then click on a point on its left and then click the central line again then a point on the right. These lines create the 200mm wide gap in the base for the wood store.

 
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Select the polyline button (or pl on the keyboard) and draw a rectangle inside the circle formed by the four points where the circle interesects with the diagonal construction lines. After selecting the last point of the rectangle RC and select 'close'. This forms the outside wall of the base. To create a 200mm wide wall you will need to offset this rectangle in by 200. This will provide you with enough “guides” to trace your base accurately.

 
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Make sure OSNAP and ORTHO are on and using the build layer select the polyline tool. Using the yellow osnap grips as a guide, create the base shape in a single polyline including the opening for the wood store and the inside face of the block wall, when you get back to the first point RC and select close.

 
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So far you have really only created three shapes. A square 1200mm x 1200mm and a circle with a radius of 565mm, and a polygon representing the base. However the construction lines and polylines in your construction layer are essential to ensure your shapes are the correct dimensions and are drafted accurately in relation to each other.

You can use the functions shown above to daft and position the cowling and flue (chimney). The cowling (bigger circle) has a radius of 100mm, and the flue has a radius of 30mm. The centre of the chimney is 255mm above the front of the footing and 420mm from the right side of the footing. Hint draw the two circles on the bottom right corner of the footing, and when you have finished move the two circles together by using the move button (or m on the keyboard) and move them up by 255 then by repeating the command across to the left by 420.

When you have finished your drawing should look like this.

 
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