Neil's News

Binocular Caps

24 July 2023

I picked up a great pair of TELEMAX 5 binoculars at a neighbourhood garage sale for about $20. The image quality is really impressive. The only problem is that there aren't any caps to protect the optics. So I designed some.

For the past 15 years I've been using SketchUp for 3D design. While it is great at building an object from scratch, it is nearly impossible to go back and revise an object. Want to change the radius of a curve? Start over.

Parametric CAD solves this problem. Everything is specified with numbers, any of which may be changed at any time. I'm using BlocksCAD; our seven year old daughter and I are learning it together. She makes Swiss cubes and Christmas trees, while I make binocular caps.

[STL Sources: Binocular Big Cap.stl & Binocular Small Cap.stl]

TPU 95A is a flexible 3D printing filament that produces objects that bend like rubber. Each cap took about an hour to print and cost about 50¢. As always, I'm thankful to be able to use Google's workshops for personal projects.

The finished caps fit snugly and should provide good protection for the binoculars. On the end of the large caps I inset a Celtic heart knot.

I originally designed the knot for Beverly so she could paint them onto her closet doors.

Since the result looked quite nice, the knots have started showing up on lots of other projects.

And finally, lest ye think that everything works according to plan, here are the five failed caps that came out of the printer. These specimens are either slightly too large or slightly too small. 3D printing with TPU is unlike other forms of manufacturing. One can't creep up on the final dimensions or sand down a slightly oversized finished part. If one needs a close fit, it's all or nothing.

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