Hi! I’m a hobbyist that’s pretty new to Rhino but has some experience in 3d modeling/CAD… I’m no engineer by any means. My main interests are woodworking and CNC machining which is the reason for my use of Rhino. I have a question that requires a lot of explaining in oder to describe it properly so I’ll try to be as clear as possible.
My goal: To create wooden sunglass frames.
Method: By pressing 3, 1/16" layers of veneer together in a curved mold, where the holes for the lenses in the middle layer are the exact size of lenses and the 2 outer layers are offset (smaller), just enough to hold the lenses in place and so the lens can be inserted by hand without breaking the frames. Each of these layers are cut on a CNC.
Progress so far: I’ve created DOZENS of prototypes. The middle layer of veneer is the most important, as it has to fit the lenses just right. I’ve done this successfully in rhino and there are no issues with that. I then duplicate that layer and offset the lens’ curves 1 mm or less to hold the lenses in. I now have a middle layer to cut, and an out layer to cut twice to make 3 layers total.
The next step is to glue the 3 layers together and press them in a mold. The mold is just a basic curve.
The Problem: This part is a bit hard to explain. When the layers are bent on top of each other, they offset. To be a bit more descriptive: When the 3 layers are stacked up flat before being bent, the outer edge of all 3 layers are exactly the same, meaning they’re all flush. However when they are bent, the outer edges aren’t aligned anymore. Most importantly the inside edges where the lenses sit are not aligned. Here are a couple simple visual representations of the problem.
These images are a representation of a top view of one side of the sunglasses. The red rectangles represent each layer of wood. The blue lines represent the edge of the where the lens goes.
This first image is what the layers look like when they are flat:
This second image shows the offset that happens when these layers are bent in the mold. Notice how the blue lines are offest:
And this is what it SHOULD look like:
What I’ve Tried: The closest I’ve been to getting this corrected is by using the stretch tool to stretch the top layer from the center of the layer to the left and right between .2 and 1 mm. And the opposite procedure for the inside layer(shrinking it). The middle layer does not get altered in any way. This has been done with trial and error and I’ve gotten pretty close but the problem is still the offset that occurs where the lenses are inserted and held into the frame.
If you’ve made it this far into this post, thank you! Any advice or ideas on how to solve this issue would be greatly appreciated.
Here are a couple videos that show what I’m trying to achieve:
