3D Design and Printing meets Astronomy

[mark]

Of course!

I recently learned how to do parametric design and drafting along with learning enough Fusion 360 and 3D drafting to be able to realize this project. Then I had to shit can the Fusion 360 project because I cannot justify $500 / year to use the program because I happen to design something that I want to sell. And that sales activity might generate a grand total of $100 or less. lol

I downloaded FreeCAD. Which, as the name indicates, is free! YAY! Now I had to learn a new 3D CAD program. Not so yay. But I plowed through. I started learning it late last night. And by 5:00 tonight I had my design finished and debugged.

I was getting restless. Not even taking a look through a telescope in almost 5 years. Something had to give. After selling off almost everything astronomy related over the past few years, including my only mount, my 130 GT refractor sat it the case all this time and it needs to be used! Picked up a budget mount, the iOptron GEM28. I am looking forward to being under the night sky in 2022.

So, a problem arose in that the included counterweight was insufficient to balance my telescope. I happened to have a very nice Astro-Physics 18lb Stainless counterweight leftover from my previous mount. Problem is, the shaft diameter is almost twice the diameter of the new mount counterweight shaft.

So I started out in TinkerCAD (freebie, rudimentary 3D CAD) and made this donut that was half the depth of the counterweight.

It worked but was to fiddly getting it to line up with the pin that tightens it to the shaft.

So, I designed a full depth version with a small base that stops it from sliding out. It also has 4 triangles on the top and one has a dimple in it to indicate the location of the pin. It is much easier to use.

None of that was done using parametric design. It was all fixed dimensions and locations.

Parameteric design allowed me to create a 3D model that uses the parameters listed here:

I can change any combination of those parameters to create custom counterweight shaft adapters for any size shaft.

Here is the first example I am printing currently.

I decided to simplify the top and just use a dimple to indicate the location of the pin shaft.

I also printed the base 17mm (added 1mm after I took the screenshot above) thick after measuring the thickness of my fingers and determined that 17mm would prevent a whole lot of pain if an 18lb weight let loose and my fingers happened to be in the way.

I intend to offer these for sale for the very few people on the planet that would ever need one. I am thinking about letting them configure it online during the order process.

I am still figuring out out to emboss some lettering and a logo on the bottom. It will have to auto size with the diameter of the base. That is going to be tricky.

The new mount with the 18LB AP Counterweight.

[taiwan_girl]

Just curious, how good are the tolerance with the printing machine?

[mark]

@taiwan_girl it is very good. The printer I am using can print .05 mm layers and when I tell it to print something 20mm, it usually measures within .05 - < .10 mm