Designing furniture with 3D CAD

I have been drawing furniture with 2 dimensional CAD (Computer Aided Design) programs for many years and have always found 3D programs (where you draw the piece and rotate it to view it from any angle) intriguing. However, only in the last few years have I found any of the 3D programs affordable, easy to use and powerful enough to accomplish what I think they should be able to do.

I now use two 3D CAD programs. The easiest to use is Sketchup which was bought by Google a couple of years ago. Sketchup has a free version available (Google Sketchup) which is really quite amazing and easy to use. They is also a Pro version which currently costs about $500 and has some added features. One feature of Sketchup I found lacking was the ability to “stretch” things easily. For example, if you draw a raised panel door and then want to make it larger or smaller. With Sketchup I could scale it to make it larger or smaller but that would also make the door frame members larger or smaller in both dimensions. There was no way of making the panel larger or smaller and the frame members longer or shorter without also making them wider. I found this disappointing and started looking around for other 3D programs that could do this properly. (I should note that I believe Sketchup Pro now has the ability to do this.)

I had read about another CAD program Alibre Design at some point (perhaps even before finding Sketchup) and had download a free version of it but had found it too difficult to learn. Alibre design is quite different from any other CAD program I’ve used. It seems that most CAD programs I’ve seen are primarily intended for architects and builders. Alibre is designed more for engineers designing products. Parts of a product are built individually and then are assembled which is the same way furniture is built. Subassemblies (such as a frame and panel door) can have dimensions assigned base on the overall width and height of the door. For example:

Door width = 12″
Door height= 22″
stile width = 2″
top rail width = 2″
bottom rail width = 2.5″
panel width = door width – 2 x stile width + 1″
Panel height = door height – bottom rail width – top rail width + 1″

Once these dimension are defined all you have to do is change the door width and height and the assembled door size changes. This is the same math you do in your head when working from a simple drawing in the shop. For something like a bed design all dimensions can be defined as a function of the matress width and length. When you want to change the bed from queen size to king size just change the mattress width dimension from 60″ to 75″ and all appropriate dimensions change in the entire drawing. The number and spacing of spindles can be defined as a function of the width and more spindles added as needed. This type of dimensioning is referred to as parametric. Alibre can also generate cut lists for all the parts of an assembly.

Of course learning a program like this takes time but the results are worth it. Basically you can build the entire piece on the computer, figuring out all the joinery issues before you go into the shop and cut a single board. From a customers perspective they can view the finished piece from all angles in the wood of their choice and know exactly what they will be getting. For complicated pieces this is a very valuable tool.

Here’s a rendering (done with Alibre Render) of a sleigh bed design I have been working on:

Here is an exploded view rendering of the same bed:

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