Life after SketchUp?

A few years ago I found Google SketchUp when I was looking for some cheap CAD software to design a shop building.  After a little bit of playing I was amazed at what could be done with this tool & even more so given that Google made it available as a free download.  I saw that there was SketchUp Pro, but it didn’t seem necessary for what I wanted to do.  At the time I was using both Windows and OS X machines, so the fact that SketchUp was available for both was an important bonus.  I have since left the Windows world entirely and Google has sold SketchUp to Trimble.

With time and use I began to see why there was a Pro version available.  I had a credible 3-D model of my shop, but I also needed to provide my builder with 2-D construction drawings.  I could make do with a section plane slicing off the walls just above floor level, but this felt like a bit of a hack.  Placing the dimensions in the model made sense initially, but was cumbersome working with the model over time.  LayOut (which seems to be the main reason to get the Pro version) is the companion tool to produce construction drawings & is capable of solving the problem elegantly by linking the 2-D and 3-D representations.  Nonetheless, I persisted with the free version and created the 2-D drawings; since my building was fairly straight forward, they served the purpose nicely.

A couple of the things that I really love about SketchUp are its simple interface and inference engine which make model construction a fairly intuitive process.  I also found the tape measure tool which allows quick measurements of the model’s elements to be extremely handy.  While I have some training in mechanical drawing, it dates back to the era of the drafting board.  In the current era, being able to create models with actual dimensions rather than constantly doing scale conversions is an enormous time saver, to say nothing of the corresponding reduction in errors. After using SketchUp for a while I was totally sold on using modeling software for sketching and making “blueprints”…time to consider the Pro version to get LayOut!

Modeling a building sized object was my introduction to SketchUp, but I also wanted to use it for smaller objects with higher precision dimensions.  An example is a chunk of aluminum 6x4x1 inches with features (arcs and holes) drawn to standard shop precision (.001).  A task like this begins to quickly expose design limitations in SketchUp.  First the issue of size and precision.  While SketchUp appears to be able to handle .001 or .0001 precision, some research yielded a post by one of the primary SketchUp developers explaining that SketchUp and LayOut do not work properly at these precisions.  Both tools are apparently targeted more toward the architect and furniture maker rather than the machinist.  The second significant issue for me was how SketchUp handles curves.  At its heart SketchUp is a polygon modeler, so curves are represented as polygons along with everything else.  Normally this isn’t much of a problem, but it can become troublesome when one is designing something via sketching it out and expecting to make accurate measurements.  For example, if I have a circle, then slice off a portion, and now want to measure the corresponding chord length…well, all I get is a rough approximation.  This makes accurate measurements and dimensioning either very difficult or impossible.

SketchUp and LayOut are excellent tools for their intended purpose, unfortunately with experience I discovered that my needs were different.  The moral of the story is to have a clear understanding of goals prior to selecting tools (doh!)–I had leapt at the chance for “free” and had not thought clearly about what I really needed.  After my initial trial of SketchUp, I was hoping to find that it was a generalized 3-D modeling tool that did everything, for free.  Well that is a fairly unreasonable hope, particularly in light of what the professional CAD packages cost.  That cost difference makes SketchUp all the more impressive.

After this experience and having refined my goals, the two packages on my short list to evaluate are FormZ and Rhino.  Having spent a few hours working with Rhino, I really miss SketchUp’s sparse simplicity, but equally I can see the benefit of a far more comprehensive tool when it comes to modeling and producing shop drawings for parts.