USE OF AIDES: DIGITIZING TABLETS
The digitizer tablet is sort of a large specialized electronic drawing device which gets connected to the wall and your home computer at the serial port. It is a two part hardware assembly which operates in combination with specialized software inside your CAD software or within Windows. The tablets are commonly used in the engineering offices for tracing lines or for commands. This later is a specialized operation having little to do with copying parts but will be brought up later herein. The other persons who often use a tablet are into electronically drawing for graphic illustration purposes. Although the actions of the graphic artist and the CAD operator are similar, the optional pen concept to which they are familiar, will not be further considered herein.
The hardware consists of a hand held puck which emits electromagnetic waves and a receiving instrument, called the tablet. The tablet has internal electronics built in around the borders and it is to the edges where power and signal cables are attached. This border area of the top surface generally cannot be used, as only the center area has the electromagnetic grid. The horizontal and vertical measurements of the grided area is used as the basic reference as to size/type of tablet.
The puck is the other main portion of the digitizer, and it emits a low level signal when idle. When you place it upon the tablet surface it will cause the cursor on your monitor to act much as the common mouse does. The puck also has buttons which when depressed causes a beep to act like a button on the mouse does. This coded beep is picked up by the tablet grid and causes softwares to react much the same as which you would expect a mouse to do. Within CAD software it quickly converts to coordinates, then sends the signals on down the wire to your computer port. What is of interest here is that this magnetic signal has a strength good enough to penetrate paper or wood up to 1/2 inch thick. Then, as you will read leads to a fast and accurate way to create parts.
At the business end of digitizer usage is the hand held PUCK. They come with different button setups, and as either corded or battery operated, but each has a clear plastic reticule. Across the face to the reticule are two black lines etched in which represent the aiming point of the accurate signals. As you swing the puck like in the motions of a mouse, the cursor or crosshairs on your monitor move also. Around the reticule are wires placed in a precise loop which produce the non-coded and the coded beams. Through technology, the magnetic waves are controlled to a very narrow beam width about the width of a sewing needle. The positions are measured very accurately and recorded within your CAD software. Thusly, when the puck is swirled over the tablet it becomes a substitute for the mouse, and when one of the buttons is depressed a coded message is sent down the wire.
For our purposes, the CAD operator will mainly be interested in using the digitizer for tracing purposes. This tracing begins by moving the crosshairs over a piece of paper taped to your tablet. And the lines you create while tracing will be picked up by the CAD software and written to your hard drive.
The small thing to be concerned about is the driver software which has to be loaded onto your hard drive in order for everything to operate. When you bring home a digitizer a handbook will generally tell of numerous complicated set ups for a host of Microsoft operating softwares, plus several non-Microsoft operating systems. Do not be scared when thumbing through the booklet accompanying the tablet, as a whole bunch of noted setups will not pertain to your interest. The documentation as to your usage is minimal due to the simplicity and because most of the action is taken care of by the CAD software. Methods and things done by CAD have changed over the years, but the documentation booklets keep referring to abilities way back to the earliest. The operations, drivers, set-ups, specifications and designs produced by elderly tablets are well within the needs by the home CAD operator. It is a good bet that the installation of a tablet, no matter the brand or cost, in most instances it can be configured to work with your computer. Remember, so far here, it is more confusing to read than it will be to operate. 'just covering the basics.
The tablets generally are referred to as from three sizes. The large sized models due to their size weigh of up to 200 pounds are most often mounted on a table or pedestal. The small personal sized models are generally light enough and small enough to lay on top of your computer desktop. The third type which will not be further investigated is often referred to as a pad. These are quite small (about the size of your mouse pad), and most are generally used by graphic sketch artists, whereas the low-cost Crayola types are mostly used by children.
No matter the size, the tablet is generally connected with a cord to the serial port on the computer. The idle signal and the beeps from the buttons are sent down the wire to the serial port and then the CAD software looks at the port and sorts out the information to become electronic lines in conformance with your command. Within the Microsoft computer operating system, there are two types of drivers which assist the tablet. One for older CAD systems which run in DOS and one for those CAD systems operating in Windows 95 and later. As there isn’t much change in technology concerning the tablet, you generally have to match up only two types of drivers. The most common driver for Windows 95, 98, ME, etc. is the Wintab driver which is available on the web for free at your tablet manufacturer’s web-site. For those CAD operators operating in DOS or with Autocad, completely different drivers are required. Autodesk supplies their own ADI style of drivers with the purchase of Autocad which isn't too often compatible with lower cost CAD systems. Furthermore, if operating within the DOS file structure, you need to be familiar with how to alter or create an AUTOEXEC.BAT file showing the placement of the actual driver file.
The installation of any driver in Windows is rather quick. The Wintab driver results in an illustrated window which works with a number of modern or elderly tablets with equal accuracy. It is installed by the use of the RUN or INSTALL command. By far, the most popular digitizing tablets are those most commonly known or made by Calcomp and most of the DrawingBoard types made after 1985 will conform to the driver. Tablets made by other manufacturers like Summagraphics, Kurta, Hitichi and H-P often followed the operations and setup established by Calcomp. The most popular drivers have a DP-5 mode that depending upon brand, use a series of DIP switches or magnetic command steps such that the tablet will then run. If you obtain a used tablet from an old industrial firm, it may be still set to their format and will thus not run immeiately. If it came off a Windows system, it may still be set for DP-5. It may take five minutes to locate the chapter on changing the tablet settings in your documentation, then two minutes to revise, but once done is seldom needed again. After installing the hardware and software, doing the set up, there really isn't much more to do as the digitizer will take off and run immediately when booting up into Windows. If you are in a DOS based environment, you have to tell the CAD software to turn on/off the tablet, but then again only one time. Either way, the tablet is going until you unplug from the wall or uninstall it.
The initial category of tablets to look at are the once standard large size digitizing tablets which had been made by Calcomp, Summagraphics or Hewlett-Packard. Although around for decades, they represent just a step in the CAD operation by their measurement and translation process. They are also rather heavy items and generally cost some firm several thousands of dollars. Their size made it possible to readily hold an entire drawing of 24" by 36" or 36" by 60" overall size. If you locate one, it possible comes with an adjustable stand, or was at one time custom mounted onto a wall with a computer within arm's length. Some years ago, a "Roll-UP" type of tablet was designed which enabled offices to essentially get the large object out of the way, and placed into the cloak closet. These are currently often used by engineering firms and difficult to locate on the used market.
The operation for a large sized tablet is about the same as for the smaller tablets. Their resolution is not as fine, but it is well within the accuracy that the budding CAD draftsman will need. I have used a few of these large types (like the Calcomp 9100 and 2500 series) over the years, and find them to immensely speed up the process of going from lines on a plan, then to parts or to another plan. As with any new item, it will take you an hour to set it up, but once you get used to the operation it will take only 5-10 minutes to digitize a large plan. You can speedily lay up the exterior of the wings, fuselage or stabilizers, spot out lines as to where the positions of ribs or fuselage bulkheads may be. In minutes you are really close to being finished with a set of rudimentary drawings.
The best situation for owning a large tablet is to dedicate a room to your CAD and other computer operations. The secondary way is to use one still remaining at some downtown business.
The large size tablets now days are set back into the cold dusty storage room of some engineering firm, or maybe now sitting under a pile of plans from past projects, becoming a table instead of a tablet. They are seldom used now due to changing technology. They were often used by civil engineering firms for tracing contours from some map and then graphically placing the work into a site development plan. If you have an interest into using one, contact your local old timey engineering firm for a demonstration, or perhaps for occasional use. Take an example of your plan and an empty floppy disk.
In the hands of a graphics creator, the computer monitor became a large electronic sheet of paper on which to sketch upon. The work of a graphic artist is similar in respect to some of the work by a CAD operator. Just as the graphic artist finds the common Microsoft mouse is infeasible to use for drawing purposes, your copying the lines on a model plan, even with a pointer glued onto the side, will be equally bad or difficult. With the mouse, the X-Y proportions vary with the surface quality of the paper media and thus cause distortion. Even the small low-cost tablets can perform some of your tracing, but this requires you to know of the limitations. As you will find, the surface area of the smaller digitizing tablets is just large enough to tape up a horizontal stabilizer, rudder and wing ribs shown upon a plan.
Just like with the large tablets, you begin the calibration. What goes on here are tablets are bit stupid, and the 30 second calibration (not the set-up) process must be completed in order for it to know how big of an object you are going to trace. This generally is to hold the puck over an X on the surface with known set of coordinates, and then over another X at some other place on the tablet and entering the coordinates for it. Most often this is at a 1:1 ratio and tells the computer and tablet what lengths are in the real world. However, if you are smart, you can take a set of manufacturer's plans no matter the scale, then tell the computer at calibration the full sized lengths. Then as a second step much later you just do a scale down to the proportion of the model. If all you can find on a particular airplane is that from a book, just Xerox copy it, and calibrate the paper to an easily recognized length such as a wingspan. The CAD software will immediately adjust thinking, and you then begin tracing the airframe outlines. Know of some obscure jet to which no one has made plans for yet?
Many folks who own small tablets try to do what the big ones can do, but in squares until the whole project is on the hard drive. In use, the operator will tape a section of the plan onto the tablet surface just as with a large sized tablet. Then begin the CAD session, ask the software to calibrate, and begin the tracing which will take about 2 minutes. You can tape up copies of a few ribs, or maybe an end section for the fuselage. Anything which can fit the general limits of the small tablet can then be digitized. The electronic beam will pass through the paper to the grid, and immediately show up in the drawing editor for the CAD software. If you are tracing an item such as the lines to a rib, the exterior surfaces, slots for spars, lightening holes, and leading/trailing edges will be roughly defined. From there, you need to use the editing portions of the CAD software to smooth out or make more accurate. If you ganged up several ribs onto one sheet of paper, then they have to be separated into their appropriate file names based upon part numbering. This whole phase of creating a rough drawing from the digitized lines of a plan generally takes about 10 minutes to complete. A real time saver and accurate too.
The other situation here is copying of die cut parts from a kit.
As with the large tablets, the smaller ones working within Windows use a (hardware) configuration known as DP5. This is a system which sets the correct codes down to the correct pin numbers. Tablets are very flexible and if last used on a Wang, SUN or some non-windows computer like a Macintosh, it will hold that configuration until changed. You then need to reconfigure the tablet for meeting the operating system or the CAD software. This is explained in the manual, or at the manufacturer's web-site. In doing the hardware set-up, there is yet another sneaky switch that may have been left on or off. It is referred to as the Point Mode and the Tracing Mode. By all means this has little relation to your thinking of intended uses, but set for POINT MODE. The difference being is that quantity of point/numbers added to the hard drive once you mearly touch the puck buttons. Most CAD software will not operate commands in TRACE mode either.
With some of the older large sized tablets, a special straight through or "twisted" cable will be required to connect into your serial port, or no communication will occur. This is of little concern by tablets made in the past ten years, but most times the manual will show you how to make one yourself as locating one may cost more than the tablet did. One other major development, is that no matter what you do, some of the 1970's and 1980's era Calcomp tablets cannot configure nor communicate with Windows era software unless certain hardware modifications are present. These tablets were manufactured for nearly 20 years, and all look the same externally. To be safe when purchasing one of the older 9xxx or 25xx numbered large tablets, first verify via serial numbering of which era it was built in. Don't obtain one of the early era, unless your computer or software is old enough to talk to it. Their tracing ability/output is still excellent, but they will not otherwise configure into any Windows operating system. Much of this warning applies to elderly equipment which can be found at near giveaway prices. If you are working with more modern equipment such as of the Calcomp Drawingboard series, the warnings do not apply and do not need to verify serial numbers.
After which, the operator then will need to initiate via a software driver yet the communication system. As mentioned Autodesk has their's and the WinTab driver will meet the requirements of most other CAD systems. Generally a special menu will occur during the installation, which can be hid afterwards. Most tablets will not operate without a hardware set-up, proper cabling and a software driver. The initial set-up routine may consume an hour for the neophyte in going through the manual, and dissolving the terminology. It only has to be done once, but you are not done yet.
The tablet will in general be running in the background. As readily seen, it also can be used for most any other Windows software which requires a mouse. Next is to coordinate this running with the CAD software operations. For your tracing purposes, this is referred to as the tablet calibration. It begun with turning on the tablet or turn off the mouse operation with a software switch as explained in the CAD software manual. Usually some typed in command like TABLET, ON will suffice. The tablet mode will remain in place until turned off. The CAD operator will need to turn on/off the tablet whether it is plugged into the wall or not.
After you then have sticked up the plan onto the tablet surface, the tablet needs to be calibrated as mentioned earlier. The CAD draftsman will then align and establish a scale ratio by the insertion of the coordinates, usually one to one for the input of line work, and then go-go-go points setting lines and points into the CAD system. Also, using a tablet and wrong sized plans (like from a three-view) it is also a simple matter to alter the ratio. It is a ten second alteration to lie to the computer by telling it different coordinates. If you have a miniature plan of some large aircraft, tell the CAD software that one wingtip is at coordinates 0,0 and the other tip is at 89,0 and the adjustments will be taken into hand. The 89 can represent 89 inches away from 0,0 for model scales, or 89 feet for prototypes. There is no scaling or proportioning here. It is all taken in as a matter of fact by the tablet.
After which the operator can trace around the lines of parts shown on the plans by looking through a clear glass reticule with cross hairs in the center and beeping out points. If a slab of die-cut wood parts is taped upon the surface, the cross hairs center over the cut line, and tracing begins. Once sheet 6 is completed, then sheet 7 gets taped onto the surface and tracing continues without exiting the CAD set up. This last phase of tablet set-up is repeated each time there is a need for tablet operations and usually takes ten minutes beginning to end to get more than enough points to go to a normal drawing session.
Going back a bit to the hardware warning of TRACE MODE and POINT MODE. You can trace around unusually shaped parts in a flowing point mode in the way that numerous points or lines get set at a rate like 100 per second as you push one of the puck buttons while trying to trace over a line. Each manufacturer may refer to this mode a bit differently. Basically, there is the instant flow of points in through your CAD program and on to your hard drive to represent lines seen on your monitor as one type. This is at a measured rate of X amount of points per second. A figure which can range into the thousands per second which only late model computers can handle. Another type being that when you push a certain numbered button, out come the points at a certain rate per inch of movement. The safest system is the one point per push of the button style. The latter is generally preferred, as you generally only need end-points or several points on a line to establish the general arrangement of the part. You can quickly pop the button as fast as you want representing the TRACE MODE while slowly moving it along and get a nice copy of the shape. As you pop the button in any of these methods in the LINE mode, the computer monitor will quickly connect lines into the shape you actually trace. In a matter of seconds, you will very quickly create a drawing without using any measurements. In the one point at a time mode, you can slow down and take it all at your own pace. One touch on the end to one line, a touch to the other end and you have a nice straight line between the two. More beneficial than trying to trace a perfectly straight line by hand.
Your resultant image will be on the crude side when using TRACE MODE. If you twitch a bit while tracing a long arc it will show up very well upon zooming in later. If you run it in the endless stream of points mode you will get a drawing with numerous criss-crossed lines as you go from part to part. The end result will still require a bit of hand interpretation and manipulation to become a part or drawing that meets the needs. The digitizing method once you are familiar with it, should enable you to obtain the general outline/configuration of a full set of plans within a 10 minute session. Whereas, using the scanning method outlined earlier, entails much electronic picture taking, alignment, tracing, scaling, conversions, and further interpretation. The digitizing method will not permit stretching or distortions sometimes required when you get ahold of a poorly drawn plan. You cannot alter the height versus width ratios, as the points you pick will be exact.
There is yet another more popular use of the small sized digitizing tablets. This is referred to as the COMMAND MODE and can only be used with higher priced CAD software. Using a special plastic sheet overlay, these small sized tablets became popular with CAD operators. The tablet overlays had numerous boxes containing set commands and when CONFIGURED these became shortcuts for the typing or going to pulldown menu with the mouse pointer.
It was a simple matter to swing the puck reticule over to a box, and get an immediate reaction. When set up for the configured command mode, each of the boxes contain coded instructions from the CAD software menu which can eliminate 2-3 steps in the structure, thus saving a few seconds here and there. The tablet was installed in the hardware/driver manner as explained. However, once entering the CAD drawing editor, instead of issuing the TABLET MODE, ON, CALIBRATE, you instead typed in TABLET MODE, ON, CONFIGURE. This in turn told the CAD software to enter a different set of instructions.
After taping on the standard tablet overlay like which is used for Autocad, generally a rectangular area remains near the center which represents the drawing window. After a bit of practice, these small sized digitizing tablets when combined with the special software, will speed up the development of CAD drawings for the professional. Instead of swinging the mouse pointer here and there, up and down the visible area on the monitor to enact commands, or manually typing is a command, you just swing the digitizing puck over a certain box, push a button and the command is instantly run for you. It is then a matter of continuing the inputs for the command, like for inserting the proper endpoints for line work. As an example, 1, 2 or more of the little boxes each can issue the ZOOM-IN, or ZOOM-ALL command at the touch of a button over the proper box.
For a while custom menus were widely distributed, often along with custom secondary software. This created a dual use for the digitizers, and in many circles the tablets are moreover known for the command operations instead of the tracing operations. If you have the know-how, a box can contain a specialized command often used over and over again, like to place a circle of 1/4" radius and an endpoint with only one button push instead of several.
The drawback to the custom menu rage was one of environment. Offices were getting more crowded, desktops were getting smaller. These 12 by 12 digitizing tablets tend to take up a good amount of desktop space however, and almost therefore require the CAD drafter to work off a large drafting table. The tablet had to share that same crowded space with a set of plans which tended to tumble onto the floor. If you wore eyeglasses, this also created yet another problem for senior engineers. That of focusing the eyeballs first on the bright monitor and then on the tablet surface an arm's length away.
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The size and availability of tablets were originally based upon the intended use by the original purchaser. If the purchaser wanted to digitize a large plan, it was a large tablet they got. In practice, the large amount of hand work involving tracing all the lines on a plan, made for use by lower paid and low-tech employees. Large sized tablets are considerably more expensive to purchase and thus when the firm was converting a paper plan to CAD the purchase was only for a tablet large enough to tape up and fit their standard plan sheet. In civil engineering offices, the most common use was to have a person digitize or trace over contours such that the information could then be added to a project computer file. That computer file was then added into design drawing files and plotted out. Civil engineering offices became the preferred haunt to computer salesmen for large sized tablets. Whereas, in graphics offices they had little use for large tablets, and more generally bought smaller tablets. All of these thoughts have to be considered when you begin a search of the city to get a demonstration or time to use for your benefit. As technology has evolved, many of the hand traced efforts are not needed anymore, and thus the tablets sit unused in a small room at some office.
Let us look at the two main types of tablets and their operations.
SMALL TABLETS
