Jewelry design strategies

 From:  Michael Gibson
754.2 In reply to 754.1 
Hi Jesse, cool project, it's already looking great!

I have an idea for a different way to build the cutter, I think it's several fewer steps.

Looking at the final cutter result, it primarily has a cylindrical shape but ending with a rounded cut on the ends. So the idea behind this different approach is to follow the "big picture" of that shape and literally build a cylinder and cut rounded parts off.

Your method is a very incremental approach. I think that a lot of times this is a great method to use because it is just easier in general to make forward progress by small steps that build a piece at a time. It's kind of a more guaranteed way to finish any particular model. It doesn't always make things happen in the fewest number of steps, but a lot of times it will take more time to worry about the fewest number of steps than to just make incremental progress and finish it up! (anyway, I'm sure you're aware of this, just mentioning for others as well). So there is absolutely nothing wrong with your approach, it's kind of a real life approach. But of course it is nice to optimize things for a tutorial though too.

Anyway here is a more "big picture", "create it like the final thing looks" approach. I took the curves from your second step, used Edit/Separate on the semi-circle to throw away the straight line part, and mirrored that arc over, to get this curve setup:

Create the main body part by selecting the 2 large circles, and using Construct / Extrude, turning on "Both sides", and using a distance of 0.85 (the radius of your arcs there), then I deleted the 2 large circles which gets the main body piece:

Now select the cylinder, and run Construct / Boolean / Difference, and select the 2 arcs as the subtracing/cutting objects. Each arc will project all the way through the ring and you will end up with 4 solid pieces. Delete the 3 pieces you don't want, and you are left with this:

This sequence leverages MoI's auto-extrusion of planar shapes inside of the booleans to avoid extra steps.

You method kind of follows a "defensive" approach where your booleans are clearly pushing all the way through each other. That tends to guarantee successful booleans which is nice. The way I show above has booleans where the cutters and the objects to be cut skim right along each other, sometimes that can cause problems although MoI's geometry engine seems to handle this type of stuff pretty well especially with simple shapes, so I'm getting less hesitant as time goes on to try those types of things. But things definitely have to be snapped together nicely for this type of boolean to work well.

Another possible approach would be to focus on just the outside single surface of the cylinder, and trim that to the 2 arcs and then thicken it using Shell.

Hope this helps!

- Michael