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3D printed 10 inch mirror Cell

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#1 Dale Eason

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Posted 17 April 2018 - 08:40 PM

I'm building a 10 inch F3 DOB scope.  I decided to try a 3D printed mirror Cell.  If it fails to hold collimation for what ever reason I can replace it with something better.    It is printed in PETG and is 1/2 inch thick with a hollow grid structure inside as is usual with 3D printed parts.  It has about $20 in stainless Steel hardware  some used to hold it together.  It was too big to print as one piece on my printer.  Took about 8 hrs to print all parts.  However there was an incremental design process so parts where printed many times through each iteration.

 

The 3 collimation bolts (springs not shown) move the whole thing so the lateral mirror supports move with collimation and always touch the mirror in the same spot at the center of Gravity of the 10 inch 1.1 thick mirror.  The top radial arm hold the collimation bolt.  A separate finger at the top of the mirror box will keep the mirror from falling forward.  

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#2 moshen

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Posted 17 April 2018 - 09:13 PM

Wow, very nice. Would love to hear how it works. Normally I use PETG for anything mechanical but I wonder if PLA might be good for this because of its stiffness. 

 

Nice design!



#3 Andy Tucker

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Posted 17 April 2018 - 09:26 PM

snoopy2.gif I'm really excited to see someone try this, particularly in PETG.  Since I got up and running with 3D printing a few years ago, I've been doing a lot less machining, and very little fabrication of small parts from wood. I'll be working on a 10" mirror project this summer.  Hopefully you'll test it before I get around to making a new mount :-)  I like PETG for its strength and high melting point.  What was your % infill for the parts?


Edited by Andy Tucker, 17 April 2018 - 09:27 PM.


#4 Dale Eason

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Posted 17 April 2018 - 10:47 PM

 What was your % infill for the parts?

Sliced with MatterControl.  Infill triangles at 30%.   When made 1/4 inch thick it was too bendy.  PETG seems to be a little more bendy than PLA but I worried about the temps PLA would be subjected to.



#5 Dale Eason

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Posted 08 June 2018 - 01:02 AM

I added wiffle tree edge support and now have it mounted in the final mirror cage.  Cage will be enclosed eventually.

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#6 Dale Eason

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Posted 08 June 2018 - 01:04 AM

Side view.

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#7 nashvillebill

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Posted 08 June 2018 - 08:06 PM

....PETG seems to be a little more bendy than PLA but I worried about the temps PLA would be subjected to.

I just spent 11 hours printing a part in PLA today.  Got done and set it down....where the sun hit it.  Shrinkage and warping almost immediately, and into the trash it went.  PETG is now on its way.....



#8 markrbriggs

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Posted 08 June 2018 - 10:58 PM

It might be worth it to try PETG with carbon fiber. Another option, if your printer can get hot enough, is nylonx. That’s the nylon with carbon fiber. I printed a secondary using nylonx and it’s fairly rigid if it’s thick enough.



#9 spokeshave

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Posted 09 June 2018 - 07:53 AM

NylonX is great stuff. It is my favorite filament. But it can be a challenge. It needs to print hot and a heated bed is a must, otherwise it will warp like crazy. Even with a heated bed a brim is necessary for larger parts. But once you get it dialed in, you won't want to print with anything else.


Tim

#10 brave_ulysses

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Posted 09 June 2018 - 10:46 AM

anyone tried covering a 3d printed structure with carbon/fiberglass cloth?


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#11 robertasumendi

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Posted 09 June 2018 - 06:45 PM

Cool mirror cell!

 

I've been printing my mirror mounts in Markforged Onyx with embedded continuous carbon fiber reinforcement. The continuous carbon can make a part nearly as rigid as aluminum (but lighter). The other positive for a mirror mount is that the embedded CF basically cancels out thermal expansion of the whole part. Markforged does not publish a CTE, but their own tests suggest most parts have a CTE around 0.

 

Fiberglass and Kevlar are other embedded continuous fibers you can do with Markforged printers. These printers cost in the 5-figure zone to own, but you can upload a part to 3dhubs.com and instantly get a couple dozen competitive quotes. Some hubs are significantly cheaper than average.


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#12 slowflow

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Posted 10 June 2018 - 01:57 AM

Fantastic, watching with great interest.



#13 rfiol

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Posted 20 September 2020 - 08:31 PM

I know this is a bit dated, but I'm curious... what are the red "wing" things shown in the first photo?  What purpose do they serve.  My guess is to lock the cell in place after collimating.  



#14 Lognic04

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Posted 20 September 2020 - 09:40 PM

I know this is a bit dated, but I'm curious... what are the red "wing" things shown in the first photo?  What purpose do they serve.  My guess is to lock the cell in place after collimating.  

Those are the mirror supports themselves, notice the small dots on each - the mirror rests on those. A bit uncommon being a 6 point cell

Cheers



#15 Dale Eason

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Posted 20 September 2020 - 11:30 PM

Those are the mirror supports themselves, notice the small dots on each - the mirror rests on those. A bit uncommon being a 6 point cell

Cheers

I don't think you have that right.

 

Those red things are the rocker arms of a typical 6 point mirror cell.  They have nylon screw where the mirror rests against their heads.  In the pictures of the real cell one of those rocker arms is upside down.

 

The edge of the mirror rests on whiffle tree levers seen in the top photo of message #5.


Edited by Dale Eason, 20 September 2020 - 11:33 PM.


#16 rfiol

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Posted 21 September 2020 - 06:39 AM

 

Those red things are the rocker arms of a typical 6 point mirror cell.

Ah, got it.  Makes sense.  Thank you.  




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