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Finished v2 of my 3D-printed 6" (153mm) f/5 Newtonian

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#26 rfiol

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Posted 11 January 2021 - 01:24 PM

The $2.5K printer I have is the FlashForge "Creator 3"

https://www.flashfor...roduct-detail/1

 

The best price I found was on B&H Photo and Video for $2.7K.  I emailed them and asked for a discount and they offered $2.5K (which I snapped up)

https://www.bhphotov...ndependent.html

 

I became a big FlashForge fanboy after buying their much cheaper "Creator Pro".  It was a great machine, but the print volume was too small for what I wanted.  Before that, I owned a Creality CR-10.  



#27 cucubits

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Posted 11 January 2021 - 01:45 PM

For comparison and for fun, I'm quite on the other end of the spectrum - printer wise.

 

Still using an extremely heavily modified Ultimaker classic. I must have the most ghetto hotend ever seen, with an E3D extruder held by zip-ties smile.gif))

It does work reasonably well but for nice parts I need to be very hands on and keep an eye on it. Currently I can print only 17x17cm limited by the flexible PEI coated sheet I am using. It's great for PETG.

 

I am going to look for an upgrade this year but so far none of the printers out there caught my eyes. I have high hopes for the Prusa XL, a possibly upcoming CoreXY printer with a very large volume, most likely under $2k.

 

Screenshot_1.jpg

 

Screenshot_2.jpg

 


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#28 rfiol

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Posted 11 January 2021 - 01:50 PM

Nice!  Love the mods.  The Ultimaker S3/S5 was on my want list, but decided (because of price) on the FlashForge C3.  The FlashForge has been very reliable, and their customer support on FB has been amazing, actually.  Very responsive and engaged with their community.



#29 orlyandico

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Posted 12 January 2021 - 01:26 PM

I'm also aspiring for an Ultimaker, but probably won't get one due to the cost.. Taz-6 seems to be my leading contender at this time.



#30 cucubits

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Posted 13 January 2021 - 09:55 PM

Short update! Finally finished printing the mirror cell puzzle. Each part took about 6 hours but I did have a couple failed ones until I figured out the proper settings for this new material. It's a simple black PETG.

 

The puzzle pieces all fit together, I just need to clean up all the edges and glue it together... tomorrow.

 

It was good to see the 8 inch mirror actually fit inside, I was worried about the measurements and scaling of the parts but it turned out great.

 

Next I have some more work on the mirror box design. Here I will have to make some more modifications, not just resize: different angles for the truss tubes and will most likely fill the holes with thin walls, to keep light out. Also I don't think I need to have it square as it will not use altitude bearings. I'm still working on how to mount it on an equatorial ...mount.

 

mirror-part-print.jpeg.jpg

 

mirror1.jpg

 

mirror2.jpg

 

mirror3.jpeg.jpg


Edited by cucubits, 13 January 2021 - 09:56 PM.

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#31 rfiol

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Posted 14 January 2021 - 11:44 AM

Very cool.  I like the jigsaw puzzle approach.  I assumed you used Starbond or some such similar adhesive?



#32 cucubits

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Posted 14 January 2021 - 12:57 PM

Very cool.  I like the jigsaw puzzle approach.  I assumed you used Starbond or some such similar adhesive?

Haven't glued it yet. I'm testing options currently:

 

- CA glue (the one you mention) works great with all plastics. The one I have at hand is very thin and wicks in easily but is not gap filling at all.

- two part epoxy - glues everything and it's strong, most likely this is what I'll use. I have some slow curing one which would allow me to set the part properly.

- I discovered that liquid plastic cement works with PETG. It's a very thin liquid and seems to melt the surface it touches, almost like welding PETG parts. To use this effectively I would need very clean and perfectly mating surfaces. Also, this does not work with PLA.



#33 brave_ulysses

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Posted 14 January 2021 - 01:20 PM

hi cucubits,

 

do you prep your pei build sheet for petg? my 2 attempts to print petg on unprepared pei led to the petg not releasing from the pei sheet. maybe there is a seret sauce i don't know about...

 

thanks,

 

clay



#34 cucubits

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Posted 14 January 2021 - 01:52 PM

hi cucubits,

 

do you prep your pei build sheet for petg? my 2 attempts to print petg on unprepared pei led to the petg not releasing from the pei sheet. maybe there is a seret sauce i don't know about...

 

thanks,

 

clay

I'm using a flexible textured PEI coated sheet. It's the one from the Prusa Mini (I actually bought it from Prusa's store from the EU). All I do is clean it with alcohol and heat it up to about 85C (anything lower, it will warp). As soon as it cools down I have no issues at all to release even large surface area parts like the ones above.

 

I did have problems before, this is the reason I bought this sheet. I used to print on a clear, flat PEI sheet over my aluminum bed. While for PLA it was awesome, as you said, it was completely impossible to get PETG parts to release. The parts would break first and still sections stay fused to the PEI.

 

btw, to hold the flexible Prusa sheet on my bed, I drilled holes and epoxied neodymium magnets. So far they hold it well and the heat didn't kill them.

 

 

The textured sheet makes for a nice surface in the prints, I didn't expect this but I like it more than shiny/clear:

 

surface.jpeg


Edited by cucubits, 14 January 2021 - 01:55 PM.

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#35 MichaelBrock

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Posted 15 January 2021 - 10:37 AM

I just discovered this thread and it has been a great read.    I love my 3D printer (Hypercube Evolution) but even then it's a special project to print as much of it as you have.


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#36 cucubits

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Posted 18 January 2021 - 09:11 PM

Another short update on the 8 inch. I've been tinkering with the lower section a lot these days. I ended up re-designing it almost from scratch (kept the base section so the printed mirror cell will fit). It's still work in progress.

 

I was constrained on sizing by the focal length and the 500mm carbon fiber tubes. Anything longer would've been too expensive and these ones from amazon will work well, just that I need to make the printed parts a little larger.

Also I needed to account for the mounting options I will have. With this design, I will be able to attach a longer dovetail bar for an equatorial mount.

 

 

BTW, I probably should've started with this, I don't mean to take over this thread, I hope it's ok with the original author that I post updates from time to time. If any issue with this, please let me know and I will stop. Maybe we can open another thread once the project is complete.

 

 

mirror box wip1.jpg


Edited by cucubits, 19 January 2021 - 11:48 AM.

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#37 rfiol

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Posted 19 January 2021 - 11:43 AM

BTW, I probably should've started with this, I don't mean to take over this thread, I hope it's ok with the original author that I post updates from time to time. If any issue with this, please let me know and I will stop. 

Perfectly OK!  


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#38 grzesznypl

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Posted 21 January 2021 - 12:43 PM

Very cool project. I do not know anything about 3D printing whatsoever so my question will sound a bit noobish but how does the weight/strength/durability of that material you printing with compares to more common materials like Baltic birch or aluminium, most common building materials ATM-ers use today?



#39 cucubits

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Posted 22 January 2021 - 11:47 AM

Very cool project. I do not know anything about 3D printing whatsoever so my question will sound a bit noobish but how does the weight/strength/durability of that material you printing with compares to more common materials like Baltic birch or aluminium, most common building materials ATM-ers use today?

I'd like to share my view on this. Hope the OP will share his as well smile.gif

 

I can't find any specific studies which compare the two main plastics used here (PLA and PETG) with other "regular" materials but I can tell you about some advantages of the printed parts.

 

- even though printing is very slow, it's not actual work time, you just leave the printer alone and it does it's thing. Designing the parts does take time but I think it's still faster than building the traditional way. For example, the primary mirror box which I'm working on now, will take about 40 hours total print time.

- you are free to make (almost) any shape you can imagine. This takes some time to get used to and realize you don't need to abide by "rules" from manual DIY work.

- I would also put weight as an advantage here but I don't know how heavy regular builds are. For the parts I'm drawing up and printing with PETG, I can use quite thin walls (1.5mm) but a lot of strength comes from the design shape and from the infill. This is important, the whole prints can be filled with various patterns from straight lines, 3d shapes, honeycomb, etc. This doesn't use a lot of material and adds strength.

 

This is an example, a quarter of the mirror box to be printed. The whole part when complete (all 4 glued up) will weigh about 800g (a little under 2lbs). Most likely I could've made it even lighter but I don't want to spend more time optimizing and I don't know at what point I take away from the structural strength.

 

Keep in mind that others with newer/larger printers have it even easier, they don't need to cut up parts, most can be printed in one go.

 

slicer-pic.jpeg


Edited by cucubits, 22 January 2021 - 11:49 AM.

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#40 grzesznypl

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Posted 22 January 2021 - 12:57 PM

Thanks cucubits. To weight/strength/durability I forgot to ask about the cost of this entire adventure. I do not mind working with wood or even aluminum, I would go as far as to say that I enjoy it. Just trying to get more data about process. Maybe this is the way telescope will be made in the future, who knows.
BTW what would be size and estimated weight of your telescope?



#41 cucubits

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Posted 22 January 2021 - 01:09 PM

Thanks cucubits. To weight/strength/durability I forgot to ask about the cost of this entire adventure. I do not mind working with wood or even aluminum, I would go as far as to say that I enjoy it. Just trying to get more data about process. Maybe this is the way telescope will be made in the future, who knows.
BTW what would be size and estimated weight of your telescope?

Well, we do this for the fun of designing and printing mostly. Cost-wise, at these sizes, I'm fairly sure it would be less expensive to buy a retail telescope.

 

For this 8 inch F5 mirror set, I'm going to end up with a scope about 75-80cm long. Weight is hard to estimate at this point, I don't have all the parts drawn up. I would guess well under 10lbs.

 

- the 8 inch mirror set from Agena was $265, I think.

- truss tubes: $80

- 2in focuser: $175

- big roll of printing material: $60 (not sure. maybe less).

- design time - priceless smile.gif

 

This is just a work in progress preview. I'm still considering my options how to mount it. With the dovetail bar as shown below, I'm don't know how far from balance it will be.

 

preview.jpg


Edited by cucubits, 22 January 2021 - 01:11 PM.

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#42 grzesznypl

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Posted 22 January 2021 - 01:23 PM

Ok so it seems from drawing this is going to be some sort of astrograph scope maybe with occasional visual observing, yes?



#43 cucubits

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Posted 22 January 2021 - 01:44 PM

Ok so it seems from drawing this is going to be some sort of astrograph scope maybe with occasional visual observing, yes?

Yes, in my case the plan is to use it with an astro camera but as you said, for some visual too.



#44 rfiol

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Posted 22 January 2021 - 02:02 PM

The longest print for the OP 6" scope was 35 hours.  As cucubits noted, it's not a big deal because you send it to print and go do other things. 

 

I would also like to echo the important point he made: "you are free to make (almost) any shape you can imagine."  That is what I love about 3D printing.  I'm working on a 12" Newt now that will be mostly CNC'd aluminum, but I'll use 3D printed carbon fiber (CarbonX) filament for unique parts that would be too difficult to machine.  


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