3-D Modeling for Woodworkers3/1/2013 12:25:33 PM
| ||Article by John Howell |
|I think that most of us became woodworkers for reasons other than to be on the leading edge of technology. We’d probably rather compete solely on the virtues of aesthetic sensibilities, craftsmanship and ingenuity. |
In reality, however, we’re in a highly competitive economy where efficiency in manufacture is essential to our survival. An integral part of this efficiency is how we handle the information necessary for manufacture. In custom woodworking, our shop drawings are the primary tool for conveying this information to all concerned parties.
Modern 3-D modeling programs now provide such an advantage in efficiency that they can’t be ignored. Three-dimensional modeling saves us time in the drawing process, helps us visualize products clearly before fabrication begins, and allows us to create models of parts that are ready for CNC machining.
I plan to write a series of articles that I hope will help show the benefits of 3-D modeling clearly and, at the same time, help you avoid some pitfalls in finding the right program for your company. As an introduction, I’d like to give a brief history of technical drawing as it applies to the woodworking industry. This will serve to illustrate how the method of drawing can impact the efficiency of manufacture.
Up until the last quarter of the previous century, all drawing was done by hand. Since it was the only choice available, the playing field was level. Then, in the 1970s, Computer Aided Drafting came on the scene. The uncontested market leader was, of course, AutoCAD. It started out as a strictly 2-D program, a direct translation of hand drafting. The concept was easy to understand even if adoption was a bit more challenging. CAD was a substantial improvement since it could handle changes more efficiently than hand drafting. As we all know in this industry, handling change is an inescapable part of the job.
The major shortcoming of 2-D drawings is that they are not complete representations of objects. They consist of lines and shapes drawn on a flat plane. When a human looks at these lines, he or she needs to interpolate the information in order to visualize the objects that they represent. This is okay for simple, rectilinear objects but more complex objects are prone to misinterpretation, especially with people less experienced in woodworking and reading drawings.
Another issue is that the missing information about the 3rd dimension must be entered by a CNC programmer before a part is ready for CNC machinery. Manual entry takes time and provides an opportunity for human error.
In the 1980s, 3-D CAD programs became affordable to companies with limited resources. These programs allowed the draftsman to create 3-D geometry in the computer in such a way that it represented objects in all three dimensions. The problem was that the representation was still somewhat abstract since it didn’t show surfaces or solids.
Finally, in the 1990s, 3-D modeling came on the scene for PC users. With these programs, solid models could be accurately and clearly represented, not only for human interpretation, but for CNC integration as well.
When you use a 3-D modeling program, you actually build products electronically. This may sound a little detached from reality until you realize that a 3-D printer can actually create a physical object directly from an electronic model created in one of these programs. In the same manner, Computer Aided Manufacturing programs can read all the three-dimensional geometry from 3-D models of parts and even select the appropriate tools for CNC machining. No dimensional information needs to be added by the programmer.
Since the 1990s, 3-D modeling programs have become much more user-friendly and functional. They help us to be more productive by performing redundant tasks for us behind the scenes. Even inexpensive 3-D modeling programs can now generate 2-D layouts automatically while the model is being created. These layouts can contain elevations and sections taken from any direction you want. When the model changes, the layout updates automatically.
Two basic types of 3-D modeling programs are available for PC users today. The first we’ll call a direct modeling program. With this type of program, you create the model directly and manipulate it freely without constraint. Let’s look at a model for kitchen cabinets as an example. The first thing you do is build parts such as side panels of cabinets. You then arrange the parts to create an assembly which in this case is the cabinet box. And finally you arrange the assemblies into what we’ll call a project; in this case, it’s the kitchen. Once you build one assembly, you can copy and modify, it as needed to create additional assemblies
The other type of modeling program we’ll call an engineering program. With this type of program, you build relationships between features in parts and between parts in an assembly for the purpose of automation in manufacture. A feature is any geometry applied to a part such as a rabbet in a side panel to receive a back panel. The automation works at the assembly level. Once you’ve created the first assembly you can use it as a prototype to create similar assemblies by simply entering a new value for the overall height, width, or depth. All details update automatically. In this way, you can create a similar assembly of different size almost instantly. It comes complete with updated parts ready for machining and an updated cut-list ready for cutting.
I know I’ve touched on a lot of concepts in this article. In upcoming articles, I’ll go into each concept in more detail and clarify the benefits of 3-D modeling as well as the potential pitfalls in finding the right program for your company. Putting in the effort to learn about 3-D modeling is time well spent considering the time and error saving benefits it can provide.