Last of 10 Things I Wish I Had Known About SketchUp

Components Can Be Redefined

SketchUp is a powerful tool for designing furniture and other woodworking projects. In the design phase, you can quickly make objects, copy and compare variations, and see how things will look in three dimensions. But that’s only half the battle. Between design and building is another phase, detailing all the parts so you can head to the shop with information about the exact size and location of all the parts and all the joints. SketchUp also shines here, because you can add details with a few techniques that don’t take much time. One of my  favorite techniques is redefining components. Here’s an example:

When I design a project, my  main interest is in the overall proportions and the appearance, so I model the parts in place without sweating over the details. I started with one leg, made it a component, then copied and positioned the other three. As I made the copies, I used “Flip Along” to orient them properly. The legs taper on the two inside faces. When the legs are in place, I draw the aprons by snapping on existing points on the legs, making the aprons into components, then moving them back from the edges. When I’m happy with how the structure looks, I add the details. To give myself room to work (and to avoid losing the position of the aprons on the legs) I make copies of the apron components out in empty space, open each copy for editing and add the tenons.

The tenons will appear on the other apron components, because they share the same definition names, “long apron” and “short apron”. In real life I wouldn’t throw away two perfectly good pieces of wood, but in SketchUp editing a copy, then deleting the copy is a great technique for adding detail. Turning on the X-ray face style shows the tenons, and it looks like all the joinery is in place. But the mortises aren’t really in the legs. When I get to the shop, I will need to know exactly where the mortises are, but I don’t want to spend all day (or even more than a minute or two) drawing mortises. The tenons contain all the geometry for the mortises, and they are in the right place, but that geometry is locked in the apron components.

The principle for moving geometry is basically the same, I make a copy out in empty space where I have room to work without interfering with the rest of the model. This time I copied the leg and both aprons. I picked the parts closest to the model origin, and when the copies are in position, I right-clicked and selected “explode” from the menu. That returns all the bits and pieces to loose geometry, what I do to the copy off to the side won’t affect the components in the rest of the model. I had to do that to get the tenon geometry out of the apron components. Now I can erase everything except the tenons from the copied aprons, and that geometry becomes the mortises in the legs.

It may seem that I’ve painted myself into a corner. I have all the geometry for the mortises in position in my copy of the leg, but this copy isn’t a component any more. Obviously I can make this a new component, and I could then move my new leg component into position after erasing the old leg components. That works, but it’s kind of tedious, and there is the danger of not getting everything perfectly lined up.

What’s not so obvious is an option I have when I make this copied bunch of edges and faces into a new component. When I do this in class, I’m always tempted to say “Hey Rocky, watch me pull a rabbit out of my hat”.

What would happen if I gave the new component exactly the same name as the old component?

The first time I tried this, I was a bit afraid of ripping a hole in the space-time continuum, but all that happened was this box popped up, asking me if I knew what I was about to do. If you select “no” it takes you back to the “Create Component” dialog. If you select “Yes” wonderful things happen. All of the other components in the model, that have the original name automagically change. All of the legs now have mortises, all in the right spots, and it takes longer to explain how to do it than it takes to do it.

There’s always a question when making a model of “how much detail”. It’s really nice to have the detail, if it doesn’t take too much time to add it. This method makes that decision an easy one.

–Bob Lang

This post is last in a series of 10. Click Here to Read the Other 9 Posts

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