Astronomy and 3D Printers

Discussion and instructions for astronomy-related projects
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bluemax
10+ Years Member
Posts: 760
Joined: Thu Aug 13, 2009 5:00 pm

Re: Astronomy and 3D Printers

Unread post by bluemax »

Daniel,
I recently made yet another Dob using the concepts from the Stellafane club.
https://stellafane.org/tm/dob/index.html
Did not grind a mirror or anything so exotic, but got most of the parts off Cloudy Nights Classified site.
Frank N

12.5" F5 single arm Dob

"I'm a seeker too. But my dreams aren't like yours. I can't help thinking that somewhere in the universe there has to be something better than man. Has to be"

Taylor in "Planet of the Apes" 1968
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Pete
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Joined: Fri Jun 13, 2003 9:03 pm

Re: Astronomy and 3D Printers

Unread post by Pete »

CAUTION - THERE BE DRAGONS

My first experience with 3D CAD was in the design of a $2 disposable chemotherapy infusion pump that replaced a $200 device. AutoCAD wasn't set up for parametric modeling and the work was hugely awkward. These days SolidWorks is recognized as the favored 3D software, but even the student rental version is way costly. Mark put me onto FreeCAD in an earlier post and I've been struggling with its steep learning curve.

While 3D printers look like neat toys one needs to create a 3D drawing, and therein are hidden the dragons. While the price is right, FreeCAD has minimal documentation and my experience is that learning is arduous trial and error. There are a couple of astronomy equipment shops out there who are using 3D printing and it looks like a fit for my little niche business too. So I'm preserving. My design concepts are not simple and at the rate I'm learning FreeCAD I won't be able to justify purchase of a printer until the fall.

There are real limits to what one can do with 3D printing and there are real limits to what you can do with FreeCAD. If anyone has suggestions to alternative software please share them. And if anyone happens to have an extra copy of SolidWorks that's just taking up space I can help you there.

3D printing makes for an interesting playground. But there be dragons...
Pete P.
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Paul D
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Joined: Fri Mar 19, 2004 2:13 pm

Re: Astronomy and 3D Printers

Unread post by Paul D »

Mark,

How durable are things printed in a 3D printer? I have noticed a lot of items online made by 3D printers but never actually held one. Does the item degrade over time?

This reminds me of a primitive 3D printer and its kind of funny and this will be showing my age, but when I was young I had this car maker thing. You use to insert these plastic cylinders into what was essentially a hot oven. The plastic would melt and then you would push a little lever that would inject the melted plastic material in liquid molten form into a metal mold. You would let it cool off and then remove the car body from the mold.
Paul...

16" f/5 Night Sky Truss (Midnight Mistress)
10" f/5 Home built Dob with Parks mirror.
Pre-Meade PST
Celestron Skymaster Binos 25-125x80
Meade Travelview Binos 10x50

See that 16" in the sleek black dress? She is all mine. :)
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Pete
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Re: Astronomy and 3D Printers

Unread post by Pete »

Hi Paul, there are dozens of approaches to molding. And they can be very different technologies.

3D printers can be purchased with preprogramed software to fabricate a model of a cathedral of a ghost gun. But unless you can program your own parts they're nothing but a toys.

The technology is rapidly improving as new technologies do. But there are lots of constraints. A 3d printer is SLOW. It can take hours to fabricate even a small part. There are almost a dozen different plastic type materials that can be run, and the easiest to extrude fastest printing material degrades fairly readily while some durable materials are very hard on the printer. Printing large parts is difficult as the extrusion is very small and the process is slow. But the base material must be hot for the next layer to bond properly and if you're laying down material on one side the other side will be cool by the time you get back to that zone.

There are a lot of these things for sale. Lots of little garage based businesses have spring up. You can even buy one as a kit. But I doubt that there are that many people out there with serious applications and the ability to program and run 3D.
Pete P.
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mark.m
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Re: Astronomy and 3D Printers

Unread post by mark.m »

Hi, Paul:
Durability is kind of all over the place. The plastic material I've been using, PLA, has poor heat-resistance, but its fairly strong. I've had one PLA part fail in actual use. The failure looked like a brittle fracture, probably the result of fatigue -- it failed a year after being printed. (PLA is quite rigid, and the piece that failed was a moving part connecting two shafts that weren't properly aligned.) There are other materials that are available with other properties. (Nylon, for example, is not strong, but has better heat resistance than PLA and is not nearly as brittle.)

I've got a 3D-printed (PLA) adapter with a male SCT thread on it that I use as a fidget toy. I've probably threaded and unthreaded that piece well over 100 times. The threads are looser today than when I first pulled the part off the 3D printer, so there's clear evidence of wear. However, I wouldn't hesitate to use that exact part in an optical path, because the threads still engage well. Its long-term wear characteristics probably aren't all that different than what you'd see with machined brass parts.

Pete's correct that you have to learn to create 3D designs before you can effectively use a 3D printer, and it probably takes several hundred hours of practice designing things before you begin to feel confident that you can translate a rough sketch of a part into a stable 3D design that can be printed. I had the advantage of seeing 3D printers used at work to make exotic things that couldn't be manufactured using molds or machining. (A 3D printed rocket booster, 3D printed explosive charge, and 3D printed ceramics, for example.) As a result, I started off as "a believer", and just needed to remind myself to set aside a few months of practice with the 3D design tools before expecting to make anything useful.

- Mark
Mark M
Portsmouth, RI
Celestron 14" and Meade 10" SCTs
QHY268M + SBIG ST-9
GM2000 (10Micron)
American Association of Variable Star Observers (AAVSO) observer code: MMU
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