Getting Started in CAD

Introduction: Is it time to abandon the trusted paper and pencil? If I begin to depend on the computer to assist in my design work will I face all sorts of issues such as corrupted files and lost drawings? After all, a pencil drawing on paper can be stored in a file cabinet and will stay put. Paper is compact, it is cheaper by far than the cheapest computer, lasts for years, it can be dropped into a file drawer and accessed days or years later without an expensive terminal. I have all the knowledge I need about drawing already and will face having to buy "programs" costing hundreds and even thousands of dollars before creating even a simple sketch. I will face having to learn a whole lot of skills I do not now have. My work will be compared with lots of people who already have these skills. How is drawing with a computer accomplished? What is the best software to begin with, to stay with for the long haul? Should I learn the standard drawing programs like AutoCAD, Corel and Adobe? Can my current computer handle the special requirements of CAD? These and other questions for the CAD student will be answered in the following article. Why Start in CAD?: There are five reasons why people start using CAD: 1. File Sharing: Clients, equipment suppliers, contractors, lenders, regulators and others may have requested that drawings be sent to them over the Internet. Scanning hand drawn designs with a scanner for transmission has limitations. Bitmaps resulting from scanners reduce the detail of drawings so that information may be lost. Pencil drawings and blue-prints are particularly hard to scan due to the large amount of background information that clutters up the final image and may require long sessions of editing before the image is clean enough to send. Also, the bitmap image, depending on resolution, may become a huge file that takes forever to send and receive and takes up too much storage space. All good CAD programs have convenient file sharing utilities that will translate drawings into standard formats such as DWG and DXF and others that can be easily and conveniently sent and received on the net. 2. Design Efficiency: Designing in the real world often requires the use of repetitive images and standard drawings. These standard drawings may be yours or commercially available drawings such as available here. Believe me, the computer can store, manipulate and manage your graphics much better than a metal file cabinet. Also, as government regulations increase each year, officials often want only small changes to a series of complex drawings. The computer makes creating and changing drawings relatively simple with a series of standard drawings and mouse clicks rather than starting from scratch each time a new drawing is needed. 3. Organizing Work: At some point in your business, searching for a certain drawing or a special detail begins to take up time. Having ten years of drawings fit on one or two CDs has some advantages. Computerized drawings force the designer to constantly backup, organize and simplify the products of the design process. Believe it or not, the computer can help in the organization and storage of drawings, for both the compulsive saver and the impulsive artist. 4. Just Keeping Up: As time goes on, the computer, the Internet, the cell-phone force themselves on us and we give in. To keep fighting may help one's image as an independent thinker, but it will not help a bottom line. When tools such as CAD become industry standards, avoiding their use may isolate the holdout designer from others in the marketplace favoring the competition. 5. Improving Job Skills: Many schools offer classes in CAD. There is a vast range of teachers and programs available. Many are not very useful. A term of several weeks of study will not be enough to prepare you for a job, but you will get to experience what CAD drawing feels like. Many new graduates from qualified CAD schools are not useful in a tech position without a lot of practical experience. You will have to learn a lot in any CAD job that is not taught in any school. The diploma may just get you inside the door. Time spent at the computer, solving problems on your own develops the skills you will need quicker than classes in my opinion. Drawing Basics: The most important difference between CAD drawings and other computer graphics is the way the drawing is saved and used. Computer images (non CAD images) are bitmaps. Bitmaps are a grid made up of thousands of dots. Bitmap images lend themselves to computers because the monitor screens and printers already talk the language of bitmaps, a map made up of tiny bits. The smallest bits on the screen you are viewing is 72 pixels (picture elements) per inch. There is no point in providing images on your website that has more than 72 pixels per inch because the screen will not be able to show the larger detail. When you encounter a slow loading photo on a website it probably is saved on the server to a higher resolution than 72 pixels per inch. The CAD drawing, however, is like a pencil drawing made up of lots of lines. This is a vector image. Each line in the vector drawing is a mathematical curve. When you click the mouse to start and finish a line, the resulting line becomes a mathematical formula with a point of beginning, an end point, a thickness, a color, and a style (dashed, solid, dotted etc). CAD drawings being made up of vectors are saved as a list of mathematical formulas for each line based on a point of origin. Resolution or scale of the drawing or the details of each individual line or point can be changed without altering the other objects in the drawing. This is why this type of drawing is more useful than a bitmap. Take a look at the drawing below. It is a jpg file downloaded from the eco-nomic server and is a bitmap file as are all images on internet WebPages. It is 72 dots per inch for optimum viewing on your computer screen. DXF of the DRAWING (webmaster note: DXF and DWG files can be difficult to download on some computers - we recommend right clicking on the underlined links to the left and saving them first (choose "save target as. . .") before opening.) DXF is a universal drawing exchange format developed by AutoDesk for sending vector files. Fortunately this idea for drawing exchange has endured. Once you download and click to open this file, your drawing program should display the CAD drawing. Experiment with the drawing by turning on and off (see and hide) separate layers in the downloaded file. The exterior features of the car and the interior and motor are in different colors and on different layers. This is how CAD drawings can combine information for reference or extract certain views for printing, viewing or other reasons. The car for instance can be viewed and saved as the body only (red lines) without the motor and the hidden interior details (blue lines). DWG of the DRAWING in AutoCAD® 2004 The AutoCAD business model will not easily allow older copies of the software to open drawing files created in newer versions. That is, if I have AutoCAD 2004, and someone sends me a drawing created in AutoCAD 2008, I will not be able to open it easily. AutoDesk claims that it would be too hard to constantly make newer drawings compatible with older versions. They may have a point. However Adobe has not claimed this restriction and have managed to make all PDF files mostly universally readable in all versions of their software. PDF of the Drawing Most computers can now open Adobe PDF files. This will give you the general appearance of a vector drawing especially when you zoom in. However Acrobat files by nature discourage editing and altering. PDF files are sort of half way between vector drawings and bitmaps. Your computer if it can read this image has downloaded a reader from Adobe that creates a "posterized proxy image" that can be scaled and printed like a vector image, but unlike a vector file, this format is not for editing. GCD GENERIC CADD DRAWING File Just for fun, here is a GCD file of the car created in the program I used to use every day, Generic CAD. See if your software can recognize it. More About Vectors: Vector drawings are used for mechanical drawing and design because the shapes of the objects being designed, being exact mathematical shapes, can be modified and duplicated with very few commands (keystrokes). Lets say you have a drawing of a tank and you want to stretch it out a little to make it longer. With a CAD drawing you can grab one end of the tank with the mouse and pull. The dimensions shown on the drawing will automatically change to reflect the new dimensions. Also, the area and volume of the new tank size can be instantly calculated. Try that with a bitmap. Also text in the drawing can be edited even if it runs over parts of the drawing. Also parts of the design can be grabbed, erased, flipped, changed and copied without disturbing or changing the basic drawing. Designers always have favorite parts such as pumps, tanks and plumbing fittings that appear in all designs. The CAD operator can create standard parts called components or blocks which can be easily dropped into a drawing when needed with a few mouse clicks. This cut and paste feature is a great time saver and applies to such ordinary things as north arrows and title blocks as well as drawing parts and entire pages of details. The Drawing Process: Drawing in CAD is not exactly like drawing with a pen or pencil. The mouse is used to drag a point across the screen where you click to finish a line. If this sounds awkward, it is. However, certain features make up for the awkwardness. You can, once the line is drawn, tweak and twist it to suit your needs. A line can be started by "snapping" it to connect to another point. Note the drawing above where smooth curves connect to straight lines without a bump. Car bodies are generally composed of compound curves and gentle arcs. Cad drawings create these complex forms from lowly straight lines, arcs and the occasional spiral. In the same way that a word processor is, lets face it, a lot of ways, better than a typewriter, CAD programs also allow changes to already drawn objects. You may move, copy, bend, trim any line or set of lines in the drawing. Drawing tangents to circles, angles and geometric shapes of all kinds are done with a few clicks. CAD programs have special commands that shortcut operations. Multiple trims, rotary copy and move point are three examples of this type of command. Every good CAD program has dozens to hundreds of these shortcuts. The operator is free to make objects in the long way or discover a time saving command. I find cool shortcuts in even the oldest programs. Experience develops special short-cuts and tricks that will increase your speed. The CAD program understands geometry in ways that will impress you as a new user, guaranteed. One word of caution: You will lose an important drawing more than once as you learn how to prepare and organize your work. This will happen under a stiff deadline, and your drawing will either disappear, become hopelessly corrupted, or revert to a few stray lines. The CAD thing has never been a priority of Windows which is essentially a word processing and business operating system. CAD developers are aware of this and work around this constraint as best they can. You will wind up in conversation with a special club of nerds who are often at odds with the computer industry. You will probably demand special attention from your computer tech and sales people and hopefully you will get the help you need from time to time. I have been fortunate in my area to have found sympathetic support. Layers: Drawings can be built up with several layers. Layers are like transparent sheets that build up to form the final drawing. Each layer can be changed, printed or edited without changing the other layers. The drawing can show the top and the interior of a pump chamber, the electrical wiring, survey lines, easements, the plumbing etc all on the same drawing. Certain layers can be turned on or off for printing or display depending where the emphasis is to be placed. Most CAD programs can handle several hundred layers. Scale changes are simple to make: CAD drawings can be shown at any scale. When creating a septic design, the drainfield details can be created on the same drawing as the site plan. The final results can be cut out of the overall plan for separate sheets such as the site plan, the drainfield, the tank and pump chamber, etc. It is possible to zoom in to fill the screen with a single screw head from the control panel and zoom out to show the entire county that the system will be built in, all at an accuracy of six decimal places of an inch. How Much Computer Do You Need? When I started in CAD about 1990, I think the hard drive had twenty MB (Megabytes) of space. After drawing each line, I had to wait for a second or two for the computer to recalculate the vectors in the drawing. The screen would blink off for a second. Drawings had to be saved on floppies to keep space on the drive to run the program. As the drawing grew, the computer ran slower and slower. Sometimes it ground to a halt and another sheet was required. After about 1993, computers began to catch up to the CAD programs following the invention of the math co-processors, modular ram and larger hard drives. Today, the playing of video games and movies on computer and the Internet have pushed computers beyond the needs of any small design firm's CAD program. Any decent Internet computer will work for CAD. Windows XP is a good operating system for a CAD computer. If you have an older computer, do the check below. You may have to upgrade to the minimum required system. Most CAD operators avoid new operating systems. Windows Vista and 7 have shown problems running some older CAD programs. Buying a new computer will sometimes force you to visit compatibility limbo. Minimum Clock Speed: Older machines used to run at CPU CLOCK or CPU TYPE of 200 Hz or 533 Hz etc. This is the speed of your processor. Any computer bought in the last seven years should have enough speed for running all CAD programs if it is healthy. Hard Drive Space: Most CAD programs need a few hundred MB of free space or more before loading the CAD program and this does not include the space required for the drawings themselves which could be as much as a 5 MB or much more per drawing. To check your free space, go to your desktop or Control Panel and double click on My Computer. Right click on C: drive and click on "Properties" on the bottom of the list. The pie diagram that opens shows your Free Space which is where you load and run your CAD program. Do not attempt to run CAD if you do not have at least 25% free space on the hard drive following the installation of the software. Hard drives are cheap. A business program may not experience the same kinds of weird problems as a CAD computer running out of resources. So, don't take the advice of someone without CAD experience even if they are a qualified nerd. RAM: To check your RAM, at the bottom of your screen, Click Start, Settings, Control Panel, and double click on the System icon. The bottom line on the General tab will state your RAM in Megabytes or Gigabytes. You should have at least a Gig of RAM. Upgrading your Ram today is cheap but it must match your computer and your existing RAM. If your machine is a few years old, this may not be a simple upgrade. The software manufacturer will tell you the minimum required for your CAD program. Choosing Software: There is an array of drawing programs out there. Although Corel and Adobe have a good ability to create and modify vector drawings, these are drawing programs, not CAD programs. You will become frustrated marching endlessly through the menu maze in a simple drawing assignment. The goal of the CAD program is to allow the operator to create precision plans in scale, often in large format drawings to be plotted into drawing sets for the construction of structures. The bulk of drawing programs are used to create graphic images, usually bitmaps, for graphic presentation on screen or in print. Most web artists and graphic designers would find the graphic possibilities of CAD software quite limited. However for a designer of structures, a precision hand drawing or CAD drawing has no substitute. What About AutoCAD and AutoCAD LT? I have the latest software available from AutoDesk Retail and never use it. AutoCAD is the standard in the building, mapping and manufacturing industries. If you aspire to a job in this area, then spend the time and the four plus thousand dollars and learn all the details of the latest release. However, the capabilities of the program are too vast in my view to meet the simple needs of a small design office. The same applies to AutoCAD LT, the stripped down version. For CAD drawing, I personally use an old DOS based CAD program called Generic CAD which was bought up by AutoCAD in the mid 90's and put to death. There are still many loyal users out there. The beauty of this program is that all the drawing commands do not require the use of drop down menus. Simple two letter commands with the left hand on the keyboard control all drawing functions. The mouse in the other hand never leaves the drawing. This simple setup has never been embraced by the industry. Alas, the simple way is simply not enough. In most standard CAD programs, the rampant menus either clutter up the drawing screen when not needed or slam shut prematurely. So What Is Out There? There used to be several programs out there that would do a good job for $100 or so. My personal favorite, Generic CAD sadly has expired. I have made it run on everything before Windows XP Professional. Because printers and plotters must talk to the CAD program, staying loyal to older programs however good will eventually let you down. Visual CADD 5.0. emulates many of the great features of Generic and even opens Generic GCD drawings. Although I yearn for something better, I use this software every day. There will probably never be a drawing software as intuitive and nimble as Generic, but Visual is close enough for now. However they are long overdue for any upgrades and their website has more than a few tumbleweeds blowing around. Drawing exchange between computers and programs is happening more all the time, particularly over the internet. PDF's are simply the universal format for drawing exchange. Drawings in PDF format can be saved in scale for large format printing. Quality is only good enough for print quality and the PDF file can not transmit precision values, but most communication, particularly to clients or regulators for general discussion, these drawings are more than adequate. Your CAD program must be able to print to PDF. I am rewriting this section and trying out some new software - more on this important topic later. The Learning Process: Go ahead and install the software on your machine. Then create a folder and a file for your work and constantly save to that folder and file. Once you start drawing, your files will grow and multiply. I recommend that you create a file system by year that uses short file names of no more than 8 characters. I start each file with the year and designate the jobs in sequential order followed by the sheet designation, aa ,ab ,ac ,etc: i.e. 03000aa. In this way, you can usually identify a stray drawing, or find a specific job by doing a search of your storage drive. Next, Start Drawing: Learning CAD drawing takes about as much time as learning to drive a car. You will get places as you learn, but don't do rush hour. The basic drawing is created first with dimensions and text added after. You will become frustrated while trying to do simple things. Changing line width or style, customizing drawing settings and choosing options from vast menus can take forever as you learn the system. The books that come with the programs seem to be mostly useless, except for the exercises in some. The help menus never seem to have specific answers. You are guaranteed to have crashes, blue screens, black screens, lost files etc. I once created two identical files connected with a line. Technical support for AutoCAD asked me to send it to them for their private collection. It could not be opened and that day spent drawing was lost. It helps to have a specific job to do in CAD, a floor plan for a house to build, a pattern for a fabricator to cut, or some other "real" project. Attempting to learn CAD on your own, simply to enhance your attractiveness to a potential employer is unlikely to bear fruit. Remember, if you are job hunting, you will be competing with experienced operators with books of work samples. Your objective should be the same as someone learning a new language. You must become conversational. Be prepared to create a dozen drawings. By that time you will be proud of your work, and a potential employer, or client will see value in the results. If you are stuck for a project to start with, reconstruct the floor plan for your own apartment or house. Get out your tape measure and a note pad and pencil, and measure everything about your space including the toilet, sinks and furniture. Now get on the computer and produce a scale drawing of everything. Note wall widths and drawing details such as door swing arcs and railings. This will require the knowledge of trimming lines to exact length, parallel lines, scale, arcs, and other basic operations. Name and save every drawing to your hard drive. Just play around and see what you can do. Use the help menu as you go. If you become stuck, find a friend who is literate in CAD. Cook them dinner and ask for support. Community college classes will probably only teach AutoCAD and are likely to be of limited help in your work. Dinking on your own and one-on-one help are the quickest ways to learning the language. I make available here a CAD drawing as an example. Click here to get an example of a typical CAD septic design drawing. The drawing shows a tight site on a lakefront. This drawing set contains over 1,500 separate lines and parts and the file contains about 200 KB of data. This drawing is an example only of the septic designs for sale on this site in both the PDF and DXF fully editable CAD drawing exchange format. How to Print Your Work In Scale: (Editor's note: There are a lot of questions about scale and printing - we will expand this section soon). When you print your drawing, slap a ruler on it to make sure your printer is giving you the right scale. Trial and error is the best way to resolve errors of scale. Each software will have a slightly different approach to the scale problem. If your scale is 1/4 inch = 1 foot, a ten foot wall should be 2 and a half inches on the print. If this turns out not to be the size, then the scale is something different than you thought, and you must adjust the print scale, the paper size, or the drawing scale. The scale of your print must correspond exactly with the stated drawing scale. This is where you may wind up spending your time. Resist the temptation to change the scale of the drawing. Instead, adjust the size of the border to control the printing scale. You may need to chose a different scale entirely to fit everything on the page. Once you start printing, all this will make sense if it doesn't now. And with computers, once you get it right, it usually stays for good. Start a note book to jot down tips and operations as you go. Understanding Scale: Working in Generic, or any of the open scale software, keep your note book handy to jot down scales for different sizes of paper (letter size, 11 x 17, 2ft x 3 ft, etc). In your book, include standard blocks, type styles, macros and other bits and pieces of info helpful to the drawing experience. In Generic, one can start drawing in real scale without setting any parameters. Start a line and define the length from a millimeter to half way to the moon. "Zoom All" and the drawing fills the screen, no mater how small or large your project. AutoCAD on the other hand demands a finished paper size before drawing one line. Repeated adjustments are required as you draw to fit everything in. Starting in AutoCAD is hard, but printing is easy. In Generic, the opposite is true. I must throw a border around my drawing and arrange the layout before printing to get the exact scale. I must also scale the drawing to a known printer. I chose to load all my possible borders on one layer and find the one that fits my drawing. Throw all the others away and hit the print button. Easy. Again, this may all sound like gobble-de-gook, until you get into the drawing process. Don't give up. Push through the learning curve and experience the pleasure of creating clean accurate beautiful drawings for your business or pleasure. by John Glassco © 2001-2008