Scad help

[paul Meynell]

SCad help can anyone change an Scad design?

Bottle cap Co2 the pic on thingyverse is the first version the new version you screw in connectors

I made this and it is great, but I want to pressurise a coke bottle to 4 bar I'm finding the cap is splitting from that thread section.
Is it possible to make this part thicker?
And possibly extend the threaded part by another turn or two as the O rings I got are quite thick.

https://www.thingiverse.com/search?q=Bottle+cap+Co2&dwh=35c4767d06b7da

[paul meynell]

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[Dan Spencer]

Hi Paul, 

Try this out. Its a quick and dirty model but it should work. 

https://www.thingiverse.com/thing:3374901

[paul meynell]

Brilliant thanks dan 

I will print off and let you know how it goes 

Cheers p

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[paul meynell]

Hi dan 

Thanks for this , I am going to the space tonight to print this.

I see it says design tool fusion 360 ?

How did you import the original into 360 ?

On Wed, 23 Jan 2019 at 00:56, Dan Spencer <danspe...@gmail.com> wrote:

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[Dan Spencer]

No worries.

I can put together some screenshots/ a screen capture video after work tonight but from memory heres how to do it.

If youre in the modelling environment:
Press S (Search)
Type "Insert Mesh"
Select your STL File, press ok
Select mm for the units
Model should be visible

[paul meynell]

Screen shots would be brilliant

I have used fusion a little but could not work out how to import , this will be extremely usefull 

Many thanks

 Paul

[Dan Spencer]

I dont really like modifying STLs, Modifying the original cad is always better, but here's how I did it:

https://www.youtube.com/watch?v=QE0e3pYOzPA

[paul meynell]

Thanks Dan, great video.

I only have one problem, when I insert mesh it brings it in as a mesh, not a solid bodie you can push/ pull

Found a YouTube video that says  you need to save mesh to brap. But this says 8000 surfaces aborted!

Your fusion seems to import as a body?

Any ideas

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[Dan Spencer]

Mine does bring it in as a mesh. 

If you split the mesh, you can drag around the split parts. 

It may look like I was doing a Push/ Pull operation but it was actually a Copy. I then reunited the 3 parts of the mesh after the move along one axis. (The two original parts and the new copied part)

Ive never had much luck with converting STLs to solid bodies. 

Hope this helps

[Michael Erskine]

Can I suggest a bought product to avoid all this trouble? Caps like
this are about a quid and quite reliable (we used them for barbot)

https://www.ebay.co.uk/p/Aquarium-Bottle-Cap-for-DIY-Plants-Co2-Diffuser-Air-Generator-System/1063419752?iid=311016709160

Regards,
Michael.

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[paul meynell]

Thanks Dan

It's harder than it looks!

Michael I have order 5 from China to see if they will work

Looks like a bigger diameter tube but no harm in having a look. Cheers

[paul meynell]

Update time

The 3d printed caps leaked air out of the top layer , maybe having a 100% fill would help but I bough the caps from China.

The bottle went bang at 9 bar , although I had held it around 6.5 bar for approximately 30 before the final push.

[dan3...@googlemail.com]

Just out of curiosity, what's the project that needs so much pressure in a pop bottle?

[paul meynell]

I’m making an air gun target 

Fill a 2L bottle to about 6 bar and when your shoot it it goes with a fantastic bang!

You can buy caps you pump up with a hand pump.

I wanted to automate it with four bottles on a rack with a small filling compressor.

On Sun, 17 Feb 2019 at 13:17, dan300891 via Nottingham Hackspace - Nottinghack <notti...@googlegroups.com> wrote:

Just out of curiosity, what's the project that needs so much pressure in a pop bottle?

[Matthew Gates]

6 bar is a lot! I bet that's fun. I wonder if you could get bottle caps with bicycle valves in...

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[paul meynell]

Yes the bang is immense 

Here is a couple of videos.

https://youtu.be/Dg7ohbT9O2o

https://youtu.be/Ijeo-zzhyjU

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[paul meynell]

Turns out when it exploded at 9 bar the cap cracked

So I took the opportunity to see how it was made.

It says it’s printed in ads plastic and it appears to be printed solid.

Still surpriseingly thin for the pressure 

[Dan Spencer]

Cool project Paul! Shame the 3D printed ones didnt work. 

Those bought parts look injection moulded to me. 

You can see a witness line on the top where the two die halves met and very generous draft angles on the ribs indicating a 2 part split. 

I suspect the internal thread has been formed by some sort of core than unscrews once the plastic has been injected. 

You can also see ejector pin witness marks on the underside. I think you will also find a sprue witness mark too if you look hard enough (Usually a small bump somewhere that is functionally unimportant). 

[paul meynell]

I did wonder , but at £1.03 each and no time they are a bargain.

Although I did enjoy trying on thecprinter, and if I did 100% fill I’m sure it would work but would tak 4 hours to print!

[paul meynell]

Had this at six bar for over 24 hours ! 

[paul meynell]

So after 72 hours at 6 bar I increased to 7 bar no problem.

But when I blew up a few 2L bottles I des overhead the caps don't like it!

Not sure if it is violent movement during the explosion?

Have ordered 10 more caps from China.

Looking ar encasing in resin to increase strength.

Here is a link to me shooting one of these , filmed in slow motion.

https://www.zlvr.co.uk/about-zl/

[paul meynell]

Sorry posted in wrong link!

Here is the correct one

https://youtu.be/Vx3_gLfEGhs