AutoCAD® commands EXTRUDE, REVOLVE, and REGION are the three musketeers—you will encounter this trio at every corner of 3D lane. These commands use 2D objects as the base, hence even a user without 3D knowledge can feel confident enough to adopt them. I won't discuss REVOLVE in this article, but will attempt to describe how the blending of 2D, 3D, and AutoLISP® can create the stairs of your choice using the other two commands, EXTRUDE and REGION. When you view a traditional staircase in plan, only lines showing the tread of the stair are visible; this is not a proper UCS view to create stair. Look at your house map and browse through front/back/side views to find out which view will show your rise and tread clearly. If you align your UCS with this view, stair creation will be easy.
- Draw a BOX representing your wall in default World UCS using Dimensions 5.0 in X-direction, 0.23 in Y-direction, and 3.0 in Z-direction. The length always runs toward current X-direction, the width toward Y-direction, and the height toward Z-direction.
Command: BOX
Specify corner of box or [CEnter] <0,0,0>:
Specify corner or [Cube/Length]: L
Specify length: 5.0
Specify width: 0.23
Specify height: 3
- Use the VPOINT command to view the object from the third quadrant. Change UCS to UCS>G>Front and move UCS at the corner of wall as shown in figure.
- Use the command PLAN to view the plan in current the UCS setting. Now you are facing wall height as the working plane. Draw stair shape using the LINE or PLINE command.
- The 2D stair drawn in the previous step will look like this if viewed from the third quadrant using VPOINT.
- Use the REGION command to convert the 2D stair into a region and then EXTRUDE it to the required width.
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|  SHADEd view |
Command: REGION
Select objects: Select all 2d objects representing stair
Select objects: Press Enter
1 loop extracted.
1 Region created.
Command: EXTRUDE
Current wire frame density: ISOLINES=4
Select objects: Select region created in previous step
Select objects: Press Enter
Specify height of extrusion or [Path]: 1.5
Specify angle of taper for extrusion <0>:0
AutoCAD 2007 features an enhancement called DUCS or Dynamic UCS. When a command supported by DUCS is active and DUCS is ON, the working XY plane is automatically aligned with any face of solid to work. The alignment of UCS with solid face is temporary and UCS returns back to its previous location as soon as the command finishes.
Spiral Stair
Spiral stairs are basically rotating around a cylindrical support. The steps of the stair are designed in such a way that tread is minimum towards the center support and moving up as per rise in a circular angular pattern.
In a plan view, the center support is represented by a circle and the outer circle represents the end of step width. A line connecting the center point and quadrant at 270 is drawn and polar array is performed on it to divide the circle in 12 parts or as many parts as your design requires. The island between the inner circle, outer circle, and two consecutive array lines will form the shape of the step.
- Draw 2D circles and line as shown.
- Perform polar array on line.
- Create BOUNDARY by picking point at A.
- EXTRUDE this shape and also EXTRUDE the center circle representing the circular column. Result is as shown in figure when viewed using VPOINT.
As you can see in the last figure, the extruded shape is clearly visible resting on the ground. Move this step in Z direction as required by the rise. For creating other steps, you can repeat the steps narrated above or create polar array of the first step and lift each step as required by the rise.
You will have to use MOVE 20 times to lift 20 spiral steps in the upward (Z) direction. Every step will be lifted with a new value for the second point of displacement in the MOVE command. But I don’t want to do a doctorate on the MOVE command. Is there any way to do it fast and in a simplified way? Yes. Use this AutoLISP program to make your life easy.
This program can be written in Notepad or Visual LISP editor by invoking the VLIDE command at the command prompt. Save your program with .lsp extension. Use (load “liftstep”) on AutoCAD prompt to add a new command LIFT in AutoCAD. While drafting, you can write LIFT on AutoCAD prompt to use this program. As a user of this program, you need to supply step Rise value once and then simply go on selecting steps in logical sequence. This program will lift steps in Z direction.
If you are using Visual LISP editor as shown in the figure, Press “Load active edit window” button to load this program in AutoCAD.
Command: LIFT
Step RISE value: 0.15
MOVE
Select objects: Select First Step
Select objects: Select Second Step
The Select objects prompt will continue, unless you press the Esc key.
Dreaming something different?
The stair we are going to draw is attached to a wall on one side while the other side is nicely curved. The main consideration in this type of stair is how to cut the stair per the required curve.
The above views clearly define what type of stair we need. As you can see, the stair is nothing but BOXes stacked per rise and tread requirement. The stair side touching the wall is straight. The other side of the stair is to be cut as per the defined curve. We will create a NEW SOLID having one face as per our curve requirement. If you subtract this dummy object from BOXes stacked as stair, the nice curved stair is ready to climb.
I am taking the liberty of assuming that you are well versed in BOX creation and the placement of it in Z direction. You can create one BOX as step and array it on the XY plane to lift it at a later stage to show as a ladder. You can use same Liftstep.lsp program for lifting steps in Z direction. The blue dummy object created can be of any shape except a well-defined required curve on one side. The height of this dummy object may be determined in such a way that it extrudes beyond the height of top step. This height selection will ensure the cutting of all BOXes in one go.
- World UCS PLAN showing BOXes representing steps.
- BOXes-Steps- as visible from PLAN view in UCS>G>Left.
- Create 2D objects with one side as per exact requirement of curve. REGION it and extrude beyond top step.
- View from the third quadrant clearly shows the intersection of steps and the dummy solid.
- SUBTRACT the dummy object from steps and BOXes/Steps are cut as per the defined curve.
In this case the dummy object is acting as a cutting tool! On the same line you can create stairs of various fancy shapes. HELIX and SWEEP commands introduced in AutoCAD 2007 can be used for creating railing handles of any shape and curve.
The perspective view of this stair will be something like this. It's time for you to step up!
Many professionals avoid programming in routine drafting tasks, but my experience reveals that AutoLISP is among the easiest languages to learn and master. You can join my ATP course (ATP164) “First Step in AutoLISP Programming” scheduled for December 2006 and give a nice program to your dear one for Christmas!
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Submitted by Mohmed Zuber Shaikh. Mohmed is Civil Engineer in Bharuch & employed by Sardar Sarovar Narmada Nigam Limited, Gandhinagar (India). He can be contacted via email at mzyshaikh1@yahoo.co.in
