Woodworking with CAD

Woodworking With CAD Index

Getting Organized

One of Murphy's corollaries (of Murphy's law) states that "To do something, you have to do something else first." and this is certainly as true of CAD as it is in woodworking. Using some method of organization is as beneficial as knowing where all the tools in the shop are. Knowing in general what things are supposed to look like when drawing is also beneficial. This helps eliminate the "blank screen" syndrome where one just doesn't know where to begin.

Directories and Files
The place to begin is before one even starts. The CAD drawing files need to be stored somewhere and one method is to store them in subdirectories (folders) that reside in a central data directory. Putting all the data in this location makes it easier to find and easier to back up (which should be done periodically). Subdirectories can be made and grouped as desired so long as they are easy to find. I like to put all the files related to a particular project in the same subdirectory.

A typical project subdirectory might contain one or more CAD files, a spreadsheet bill of materials, a word processor document, a pdf file, or anything else that is uniquely related to that particular project. Somewhere further up the directory tree there might also be a symbol library of CAD parts and other files that are CAD related but generic in nature.

To the right is an example of a directory structure organized to store data.  The main directory is 0data.  In addition to several other sub-directories beneath it, there is a "Projects" directory where all the woodworking related project would / could be stored.

The current directory (bladebox) holds all the files related to that project.

Learning the System
CAD software has a deservedly bad reputation for requiring a lot of user effort before one becomes productive with the tool. The reason for this is due to the complexity and power required for the tool to do it's job; unfortunately there is no easy way around this. Many CAD systems have tutorials in the manual or on-line that can help a user become familiar with the overall concepts and tools used by a particular system. Even though most tutorials are pretty basic, it is worth a new users time to go through them.

Another invaluable learning tool is to have a CAD literate friend serve as a tutor on the operation of a system. Most literate users will be able to help a new user out quite a bit even if the software in use isn't the one they are familiar with. Many of the concepts of how tools operate will be similar if not the same and even when things aren't similar, a literate user will at least know what to look for. The most important benefit of tutoring is that the tutor can show a new user in very graphical terms generally how to operate the system. An hour of hands-on graphical illustration is worth at least 10 hours of frustration that will result from "going it alone".

After the tutorial, one of the key elements of teaching yourself CAD is to have a real project to learn on. One could draw circles, rectangles, and lines forever but until there is a real world application to complete, the education will be woefully incomplete.

Learning the system is so fundamentally important that I'll summarize it:

1. Complete the tutorial (if there is one)

2. Get a tutor, even an hour or two will help tremendously in getting you started.

3. Have a real project to learn on.

I would also add that if there is a users group or forum for the particular software one has it may be worth the time to join it.

When properly used, a typical CAD 2d drawing could look pretty chaotic due to overlapping lines and details. One primary operation of CAD software is to allow lines and objects to be placed onto "layers". Imagine layers as sheets of clear plastic that contain the lines of the drawing (usually organized by purpose). These layers can be made invisible, visible, editable, removed, moved and otherwise manipulated in a multitude of ways. A woodworking shop drawing example of this would be to have the dimensions, parts, border, and notes all on their own separate layers.

When an object is drawn, it is created on the "current" layer, there is never at time when there is no "current" layer. Layering a drawing allows the user to display or hide objects for printing or display clarity. In addition to editing, each layer may have associated properties such a color and line type. Depending upon the software, entities drawn on a particular layer are displayed in the color and line type associated with that layer unless these settings are specifically overridden. The associated settings for layers are controlled using the software's "Layer Manager". All the objects in a drawing can be edited at any time including which layer they reside on; just because line#1 was drawn on layer 6 doesn't mean it can't be changed to another layer later.

One common manipulation of a layer is to turn it "on" or "off". When a layer is "off", the entities drawn on that layer are no longer visible and they do not print. Turning off layers is useful if an unobstructed view is desired when working in detail or if there are objects that are not desired in printed output such as reference lines. Hiding a layer also eliminates those objects from being selected as "snap" points, this is useful on complex drawing with lots of "snap-able" objects in small areas. Depending upon the software, layers can also be locked or unlocked. The entities on a locked layer are still visible and will print, but they are not editable until unlocked. The reason one might lock a layer is to prevent it from being accidentally modified.

Layering is one of the most beneficial and powerful aspects of CAD over traditional manual drafting. Layering allows one to do more than DRAW, it allows one to DESIGN.

In the image at right, a very simple three layer drawing of a frame and panel door is shown.  The blue layer holds the door frame, the green layer is the door panel, and the black layer holds the dimensions.

By looking at the drawing this (normal) way it isn't particularly apparent there are any layers at all or if there are, what information they may contain.   The Layer Manager should help in this regard if meaningful layer names are used though.

Layers Viewed Normally
Layers Exposed  

In this image, the same drawing information has been rotated so the layering concept is more visible.  Note that this is not possible to actually see the information as presented here in this format on 2d CAD software, this is for illustration purposes only.

Now it can be seen that the dimension layer (black) is actually on a different plane than the other two layers.

This drawing sandwich allows the information to be organized in a more useful way which in turn allows the user to only view the information desired.   It also makes it easier to copy and edit selected drawing elements.

In truth, a user would not have to use different layers in a drawing but this would reduce the power of the drawing system greatly.  This will be made more apparent in a subsequent article.

A drawing needs to be laid out in a format that is easy for both the creator and anyone else who sees the drawing to understand it. There is a widely accepted method of showing the various 2d views of an object. If at all possible this method should be used. One does not have to draw every side of an object usually; only those that are required to get the information across to the viewer.

Most likely the drawings that will be created will be printed on 8 x 11 sheets of paper. Other sizes could be used but that is the maximum size most users will have access to so this must be taken into consideration when drawings are laid out as well.

Object and its Views

Where Views Come From

A Sample Print

Proper View Orientation

Since 8 x 11 sheets of paper are the likely printed size, woodworking projects of any complexity will need to be multi-page documents; when the project is laid out in software this must also be taken into account. Some software allows the printed output to be "tiled". That is, the drawing will be printed out 1:1 (full size) in 8 x 11 chunks that must be taped together to form a single big piece of paper. For drawings of patterns and such, this can be a useful output. Otherwise, it's a lot of work one would rather not have to go through.

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