May 29, 2015, 05:22 AM
Joined Oct 2010
Specifically written as a 2D Tutorial (but applies to 3D for the most part), the cut and paste below is a small introductory part of a multi-section tutorial done some time ago that someone wrote for online participation.
It was offered as PDF sections, but the part I pasted below is just a small portion on the first part where the commands are discussed.
What's probably most interesting is that the author goes beyond just listing some handy commands, but explains what each of them does so that the newbie has an understanding going in.
Being a cut and paste, some of the formatting looks goofy, but it's very readable.
Also not terribly well written, probably so because it looks like it was intended for complete newbies.
The commands that are listed below are not all those that your CAD software should be capable of but are the most important and frequently used commands in drawing and designing your aircraft. If you can understand and use these commands, you will have no trouble with other commands that will be used less often . You should refer to your software documentation for specific use of these commands and make an attempt to understand how they work. However, you do not have to become a CAD expert to begin a drawing. If you only become familiar with the following commands, you will easily learn as you proceed with your drawing. CAD is a sophisticated drawing tool, and I am going to try to get you through the (slightly frustrating) learning curve as quickly and painlessly as possible. Don’t feel intimidated if some of this doesn’t make a lot of sense right now.
These are the most basic commands of which you should become familiar.
Your CAD software may use slightly different names for some of the commands (and terms) used in this manual because CAD programs differ from one another. You will find, however, that the function of the command is the same. It is important to understand the explanations of the functions of these commands. If you cannot find the exact command name within your software, you will be able to perform the function under whatever command name your software uses. Be sure to practice each of these commands until you become comfortable with them.
SAVE - is the most important command of all. Drawing with CAD is like flying
R/C airplanes. You are going to crash! It’s not a question of if, but of when. CAD
drawings will tax any computer system’s resources to it’s limits and at some point will create a conflict and quit responding. When a computer stops responding to your input, that’s a crash. To continue, you will have to re-boot your computer, restart the CAD program and open your drawing file again.
There are two things that you should do in order for a crash to be no more
than a minor inconvenience. First, use the SAVE command several times during each drawing session. When you crash, you will only lose what you did since your last SAVE. If you saved 10 minutes ago, you will have lost only 10 minutes worth of
work. If you saved 3 hours ago, you will probably lose your temper. Second, at the
end of each drawing session, either copy your drawing to a CD disk or save another
copy of it on your hard drive by giving it another name. You should always have a
backup of the drawing file with your most recent drawing information at all times. In the event of a major file corruption, you would then have another copy from which to continue. You may never crash, but you shouldn’t wait for the first one to teach you this valuable lesson.
VIEW - You are going to use VIEW or some sub-function of this command more often than any other command. It is how you navigate around your drawing. You should devote whatever time it takes to understand it’s many options (including the related commands PAN and ZOOM). Do not confuse VIEW with VIEWPORTS. We will not be using VIEWPORTS. Learn how VIEW commands can work “transparently”.
This allows you to change views while you are in the middle of performing some
other command without affecting the operation of that command.
Open up one of the sample drawings included in your CAD software and
practice using all of the VIEW related commands. You will immediately be using
VIEW when we begin our aircraft drawing. Having some prior experience with it’s
functions will prove invaluable.
SELECT - After you have drawn a number of objects (lines, etc.), there will be times
when some of these objects must be changed in one way or another. You may want to ERASE, MOVE, COPY, SCALE, or perform other operations on these objects.
Many commands ask you to make a “selection set” which is the specific group of
object(s) on which the command will act. You may pick only one object or hundreds depending on the operation. There are several different ways in which you can SELECT objects and you should be familiar with them all. (See OBJECT SNAP).
LINE - and PLINE (polyline) are the most used drawing commands. These are what
you will use to define the outline of almost everything you do. A LINE is always a
straight line with a start point and an end point while a PLINE is typically a curved
line that is made up of many segments that are connected to each other and form a
line that is not usually straight. You will better understand the conceptual difference between LINE and PLINE when we begin drawing. You will quickly learn when to use one or the other.
CIRCLE - should be mentioned because it will be used occasionally, but it isn’t any
more difficult to use than LINE.
OFFSET - is used in almost every part of the drawing. This command simply makes an exact copy of a line and places it parallel an exact distance (that you specify) from the original line. Many of the components that you draw such as ribs, formers, balsa sheeting etc., will have thickness as part of their dimension. This is the fastest, easiest and most accurate way to define and draw that thickness.
OFFSET is also handy for making cut-outs in the center portions of formers and other parts, done by using the outside of the part and OFFSETing inward.
MIRROR - is easily the most time saving command. With MIRROR, you are required to draw only one side of the aircraft. For example, when you are completely finished with the right wing, MIRROR will make an exact duplicate of it except that it will be opposite. In seconds, you will have a completed left wing, the exact MIRROR image of the right. Another example is that you will draw only one side of the top view of the fuselage. You will then MIRROR that side to end up with a complete fuselage top view outline that is perfectly symmetrical from the left to the right side. You will discover that very few three-views from which you will draw your aircraft have been drawn exactly accurate from one side to the other. Your finished drawing, however, will be perfect!
COPY and MOVE - are commands that are self-explanatory and will be used often. You will quickly come to understand when to use one or the other.
TEXT - is the command used to add notes into the drawing. If you are going to sell
your plans, you would use TEXT to document or explain anything that isn’t made
clear by the drawing itself. If you do not intend to sell your plans, you will still find
TEXT to be a valuable command for making notes to yourself as reminders of where you left off or to maintain a train of thought concerning a particular area of design.
TRIM - is a command that allows you to TRIM part of an entity that crosses another entity. Imagine two separate lines that make up the shape of a plus (+) sign. If you wanted to TRIM only the portion of the vertical line that is above the horizontal line, you would select the horizontal line as the “cutting edge” and then select the upper portion of the vertical line as the object to trim. That would leave you with a “T” shape. This is a very simple explanation for a simple command that will be used often throughout your drawing.
EXTEND - is an often used command and can be a real time saver. This is a command that EXTENDS an entity (e.g. LINE or ARC) to meet another entity that lies in an area where the intended EXTENDed entity could intersect. (I know. Just read that sentence again real slow.) Conceptually, it’s as if you are directing the object you want to EXTEND to continue drawing itself in the same direction until it meets another (selected) entity. It stops exactly at that entity to connect to, and form an intersection, with that entity.
ARRAY - is more of a convenience than a necessity in drawing aircraft. It’s sort of like OFFSET except that it produces multiple copies of the original entity in either a linear (rectangular) or circular (polar) pattern. Just read up on it for now so it won’t be totally foreign to you when we get to it.
ROTATE - is another self-explanatory command. One of the most useful purposes of this command is to verify clearances on moving parts. For example, after you have drawn the intended location for landing gear, you can use the ROTATE command to accurately place the gear leg and wheel in the retracted position. Then, when you draw other components that are near the retracted gear, you can easily verify that formers or other parts nearby are properly designed for clearance.
ALIGN - (ORIENT in some programs) is a distant cousin to ROTATE. When using ALIGN, however, you do not specify a rotation angle. You are asked to pick points on the two separate objects you wish to bring into perfect alignment with each other. You won’t use it very often, but it is an extremely important command for our purposes.
ORTHO - is not a command that actually draws anything. It stands for orthogonal
which means “perpendicular” or to “lie at right angles”. When you set ORTHO “on”,
you will only be allowed to draw a line or move something in an exact perpendicular direction. Specifically, you will only be able to draw or move exactly up and down, or exactly left and right. All you have to understand at this point is that failure to use this command when directed in this workshop will result in serious and progressively amplified mistakes throughout the drawing. Perfectly vertical or perfectly horizontal positioning of key alignment marks from the very beginning of your drawing is absolutely critical. I don’t mean to scare you but sometimes fear is a good thing. It keeps you on the “straight and narrow”. (Oh, I just did a pun. Forgive me.)
OBJECT SNAP - is a selectable setting, not a drawing command. Object Snap settings include ENDpoint, MIDpoint, INTersection, NEArest, PERpendicular, CENter, and others. Most of the entities (e.g. lines) that you draw will be intended to connect with a specific part of another entity. You will get unpredictable results if your Object Snap setting does not agree with the way you intend to draw an entity. If you want to draw a line that should connect with the exact end of another line, Endpoint should be your Object Snap setting. If Object Snap had been set to Midpoint, you could pick the end of the line but your intended operation will act upon the exact middle of that line.
Used correctly, Object Snap will be an invaluable time saver and will add greatly to the accuracy of your drawing. It allows you a little bit of “slop” in that you may pick only near the end of a line, but Object Snap knows that you want the exact end of that line and will make the connection there. Learn and understand all of it’s settings. In the beginning , I will specify Object Snap settings if the preferred setting is not obvious. I will insert Object Snap settings in the text with the format of (osEND), (osMID), (osINT) etc. Note that it is possible to select more than one setting at the same time.
Generally, you will find that ENDpoint and INTersection are going to be the most
commonly used settings throughout the drawing.
LAYERS - is another of several commands that doesn’t draw objects. The concept ofthe command is simple. Imagine that you have several sheets of clear acetate (the kind used with overhead projectors) and that they are stacked one on top of the other. If one of the sheets underneath has an image on it, you can draw right over it on the top sheet and add additional detail to the drawing. But if you remove the sheet underneath, you’ll see that the original drawing hasn’t changed at all. The additional drawing was “on top” on a different “layer” than the original drawing underneath.
You should learn how to create additional layers, how to select one of them to
be the current drawing layer, and how to “lock” a layer or turn it off. Locking a layer
allows the entities on that layer to be displayed but prevents any editing of the objects.
Turning a layer “off” prevents the objects on that layer from being displayed until you turn it back on.
DIMENSION - is a command that determines the exact distance from one point to
another and then writes that dimension on the drawing. There are many objects that you will want to DIMENSION but don’t get unnecessarily carried away or the
drawing will become cluttered. If unsure where to use this command, follow the
suggestions given throughout this manual. A good tip is to only dimension those
distances necessary to build the model. Also remember that YOU will have drawn your own design. The obvious point to that is if you find you really did need an omitted dimension, you can just go back into the drawing and do it.
DISTANCE - is just like DIMENSION except that the exact dimension is only shown on the command line and not written on the drawing. You will probably use this more often than DIMENSION to verify many of the important distances while you draw.
It’s easy to use so use it often for your own peace of mind in critical areas.
I cannot emphasize enough how important it is to frequently verify key distances
to avoid cumulative errors as you progress with your drawing.
BLOCK and EXPLODE - are related commands. Refer to your CAD program user’s
manual to see how they work. Using these commands is not difficult. It is important, however, that you understand the concept of these commands.
BLOCK - is the command by which you define (create) an entity made up of
many objects (lines etc.) as a single object. For example, if you draw a triangle using
the LINE command, it is still three individual lines even though it looks like a single
object (a triangle). If you then use the BLOCK command to create a “block” out of
those three lines, you have a triangle that is a single entity. You can use this entity in your drawing anyway you want, but you cannot edit the individual lines. Simple
examples of the benefit of this command are when you draw components such as
servo’s or the airfoil (rib shape) itself. You can also use these blocks in many different places without having to draw each one more than once.
EXPLODE - simply allows you to “un-BLOCK” a BLOCK. Applying this
command to an existing block allows you to again edit the block’s individual parts.
Last edited by Treeline; May 29, 2015 at 05:30 AM.