Starting a new design project

These notes are designed to aid those having some difficulty coming to terms with Computer Aided Design for the very first time.

 Don't jump in

It is important to resist the tendency to 'leap in' when asked to produce a CAD drawing. If you simply start drawing and place elements in the drawing editor without thinking too much about the construction of the whole design and the way in which you intend to produce (plot) your design, chances are as the design grows in complexity you will experience frustration.

The aim of this background paper is to show that a little planning in the early stages of a project and the adoption of a structured approach to design drafting will pay handsome dividends later. We will take you through a series of steps that we believe that you should take in the CAD environment, before you start the actual design.  

The design space

Your first step should be to think about your design area. In other words, how much space will you need to 'hold' your design.

For example, you wanted to create a design for a house on a conventional suburban allotment and were working in the metric environment (in millimeters), a design space 100000 by 60000 units (mm) would comfortably hold the design, together with any sections and details that might be required. This design space leaves plenty of room for details and even elevation take offs should they be required. 

This 'space' will be the example discussed in these notes.

On the other hand, a mechanical engineer might want a space 6000mm by 4000mm to design a piece of machinery and so on while an interior designer working in the US might use a space 240 inches by 240 inches for a room layout.

This is not to say that the design space is fixed. IntelliCAD and AutoCAD drawings can be any size.

Although AutoCAD and IntelliCAD do not require you to think about this design space area before you start drawing, we think that it is good practice because it gets you thinking about your design and its relationship to the real world - in the units that you use be they feet and inches, millimeters, centimeters, meters, kilometers or micrometers.  

Tick the box below when you have thought about your design space.

Other CAD programs such as MicroStation, actually force you to set a design space before beginning to draw.

Set LIMITS

IntelliCAD enables drafters to set a series of points  over the chosen design area (an electronic grid). You may not need to use such a grid, but unless you set the limits command correctly, you will not be able to get the grid to show. Grids are certainly used by electrical schematic drafters, ceiling lighting designers etc.

The grid is sensitive to the LIMITS setting. Its value 'out of the box' defines an area from coordinate 0,0 to coordinate 12, 9. This is not appropriate for anyone working in the metric environment. If you turn on the grid in the metric environment without adjusting the LIMITS setting it (the grid) is unlikely to be seen. In our example, the designer might set LIMITS to run from 0,0 to 100000, 60000. Set yours to an appropriate value.

Set limits checking on

Once the LIMITS area has been set, you might consider turning limits checking ON. This will prevent you placing any entities outside your design area. Beginners commonly copy entities well away from their intended position. A ZOOM extents will often show two dots at the margins of the screen and require that you zoom in on a dot to reveal the design again. The limits check on will stop this happening.

Create (and use) a DEFPOINTS layer

The layer DEFPOINTS is a special layer in the IntelliCAD and AutoCAD world. Any entities placed on it will not plot, so we believe that it is most useful to use LAYER command to create a DEFPOINTS layer. We make it the current layer and then use the RECTANGLE command to set out the 'design area'. In our example a rectangle has been drawn from from 0,0 to 100000,60000 (mm) as shown in the figure below.   

Setting up your design space

If at any time you want to show your 'design space', then all you need do is issue the ZOOM command and choose the E option. 

  It's a good idea to make your design area a ratio 3:2, the same aspect ratio as your screen.

Create a named view

Although you can get to the design area using ZOOM, E, we like to do this once only and then use the VIEW command to create a named view. We like to call this view 'ALL'. Then, at any time, we can move to the design area by typing the VIEW command and restoring the view ALL.

Setting up a view called ALL. The site boundaries have been drawn in yellow.

Set an appropriate grid

As mentioned, it is often useful to use a grid. Although it is likely that you will vary the grid setting as you work on your design, we like to set a 'reasonable' grid value at this stage. In our example, a 1000mm (1 meter) grid would be useful. Remember, the Grid works in concert with Snap.  If SNAP and GRID are on, then the cursor will jump from grid point to grid point. The figure below shows a 1000mm grid set over the design area. Note that the grid does not show outside the area defined by the limits command.

Setting up a grid. The cursor will snap to these grid points when snap is turned on (and the snap setting matches the grid setting).

Set SNAP

It is important to set your SNAP value appropriately. Most experienced drafters set the snap value to 1/5 of the grid. In our example, there would be 5 jumps (each of 200mm) as you move the cursor across the design area.

Draw the boundary of your design

Now accurately draw the extreme outside of your design. In our example, this is the boundary of the block of land on which the house sits. In a mechanical drawing, this may be the concrete pad on which the equipment will sit. The reason for this step is that once we have the design extremities accurately defined, we can switch to paper space and test some scales that we might use for our design.

Set up the presentation drawing sheet

Now that we have the design area set and defined the site boundaries, it's time to switch to paper space and use the INSERT command to import the appropriate drawing sheet. In the metric environment, A1 sheets are commonly used for working drawings. 

Use the LIMITS command again, and set limits to bottom left corner and top right corner of the drawing sheet. This step is necessary because AutoCAD and IntelliCAD allow different limits setting in paper space vs. tiled model space.

It is a good idea to set grid and snap appropriately (perhaps a 5mm grid). This will allow for accurately placed floating viewports (see under).

Setting up a grid in paper space. The cursor will snap to these grid points when snap is turned on (and the snap setting matches the grid setting). This allows floating viewports to be easily aligned.

It is possible to plot an A1 sheet half size to an A3 sheet. This adds extra versatility as the A1 sheet contains the full size design drawing, but if the drawing is required for a report, it can be plotted to A3, folded and placed in an A4 report. 

Create floating viewports

Use the MVIEW command to create a floating viewport of appropriate size. Set up additional viewports for all the details that you are likely to need.

Set up floating viewports with the MVIEW command. Commonly, a major viewport to hold the design and several smaller viewports for details. Since snap and grid are on, lining up viewports is simple.

Set scales

Use the MSPACE command to 'jump into' the major floating viewport. Use the ZOOM command with the XP option to set an appropriate scale.

Scale the major viewport. In the example above, we have use a scale of 1/100. Note that no design work has yet taken place.

The scale command does allow the use of values like 1/100xp as well as 0.01xp  

You may well decide (and we did) that the presentation on the A1 sheet would be better if we rotated the design (in tiled model space) through 90 degrees. This enabled us to use a scale of 1/50.

In the example above, we have rotated our model in tiled model space and returned to paper space and set a scale of 1/50. We have completed a little design work, but placed no explanatory text or used any dimensioning.

We are now in a position to begin the detailed drafting of our design. Use this same approach on all your drafting work.

Enrol in our distance learning program and learn about dealing with text heights, creating other layers and handling dimensioning styles. Click here to return to the IntelliCAD specification page.

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