Stuck on how to start a particular drawing?

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Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Stuck on how to start a particular drawing?

Postby Lazlow » Fri Apr 03, 2020 2:38 pm

Hey Guys

Been using FreeCAD for a little bit and I am slowly getting the hang of most thing. Half the time I do a 2d draft and wind up starting over because I cannot pad it the way I drew it (learning curve). Most stuff I can stumble along and figure out. But now I am trying to design an air flow nozzle and I am stuck.

Picture a cylinder 25mm in dia and 5mm tall. On top of and concentric to it, is a cylinder 20mm dia and 10mm tall. On top of that is a 20mm(at base)cone. So far so good. Now, I want to add a series of 1mm wide by 5mm tall "fins" separated by 2mm running vertically on the outer skin of the cone and the upper cylinder. Think a round heat sink except the fins running virtically rather than concentric to the cylinder.

I am suspecting that the start is to draw the profile and spin it, but then how do I add in the fins or the slots between them? Can you "shape" a pocket?

Thanks

In concept this will be a three part assembly. An outer hollow cylinder casing that the above part drops into. Followed by a cone shaped lid that drops into the casing but over the above part.
drmacro
Posts: 3536
Joined: Sun Mar 02, 2014 4:35 pm

Re: Stuck on how to start a particular drawing?

Postby drmacro » Fri Apr 03, 2020 3:27 pm

Not sure I fully understand how you envision the fins...but something like this?
Nozzle.png
Nozzle.png (42.72 KiB) Viewed 393 times
Or:
Nozzle-1.png
Nozzle-1.png (47.41 KiB) Viewed 393 times
Attachments
Nozzle-1.FCStd
(67.1 KiB) Downloaded 8 times
Nozzle.FCStd
(63.22 KiB) Downloaded 7 times
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

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chrisb
Posts: 35953
Joined: Tue Mar 17, 2015 9:14 am

Re: Stuck on how to start a particular drawing?

Postby chrisb » Fri Apr 03, 2020 3:30 pm

I cannot exactly imagine what you describe, perhaps a handmade doodle can help or a link to something similar in the internet. From what I understand for the fins: you may consider a DatumPlane which you place where the fins end, and then you pad up to first face.
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Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Fri Apr 03, 2020 3:35 pm

You could use a pad and polar array feature, like this:-

EDIT Too slow :lol:
Attachments
FinCone.FCStd
(103.76 KiB) Downloaded 5 times
FinCone.jpeg
FinCone.jpeg (60.65 KiB) Viewed 385 times
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Fri Apr 03, 2020 3:37 pm

drmarco has it pretty close to the mark. The only thing a see off is that I wanted to maintain the skin to fin height constant. Which may just be an excess constraint placed by the concept I have in my head.

Thanks you

Now I have to tear into your example and learn how you did it.

Edit: Bance too.
drmacro
Posts: 3536
Joined: Sun Mar 02, 2014 4:35 pm

Re: Stuck on how to start a particular drawing?

Postby drmacro » Fri Apr 03, 2020 3:45 pm

Lazlow wrote: Fri Apr 03, 2020 3:37 pm drmarco has it pretty close to the mark. The only thing a see off is that I wanted to maintain the skin to fin height constant. Which may just be an excess constraint placed by the concept I have in my head.

Thanks you

Now I have to tear into your example and learn how you did it.

Edit: Bance too.
Yes, because I was guessing I didn't constrain completely or necessarily where you may want constraint. ;)
Star Trek II: The Wrath of Khan: Spock: "...His pattern indicates two-dimensional thinking."

My beginners, written treatise: Learning FreeCAD
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Fri Apr 03, 2020 8:05 pm

Made some changes along the way, but this is getting closer. Did a rethink and I am planning only two parts now.

The small holes are not correct(as in not holes). Is there a way to tweak the start point of the Polar Pattern?(other than the way I did it on the small holes). This is the first drawings that I have made that makes my Pi4 squeal. For whatever reason it is only using one core.

I did not understand why you put the fins "inside" the cone stucture the first time I drew this. Now I know.
Attachments
Nozzle-test.FCStd
(189.99 KiB) Downloaded 7 times
Nozzzle-Test#1.png
Nozzzle-Test#1.png (155.06 KiB) Viewed 337 times
Lazlow
Posts: 23
Joined: Tue Mar 10, 2020 4:52 pm

Re: Stuck on how to start a particular drawing?

Postby Lazlow » Fri Apr 03, 2020 9:00 pm

Still do not like the way I had to get the holes but at least they are actually there now.
Attachments
Nozzle-Test#2.png
Nozzle-Test#2.png (142.87 KiB) Viewed 331 times
Nozzle-test#2.FCStd
(187.96 KiB) Downloaded 9 times
Bance
Posts: 2030
Joined: Wed Feb 11, 2015 3:00 pm
Location: London

Re: Stuck on how to start a particular drawing?

Postby Bance » Fri Apr 03, 2020 9:10 pm

You need to change the position of the sketch, using attachment offset.
Attachments
Nozzle-testbance.FCStd
(199.27 KiB) Downloaded 7 times
freedman
Posts: 2016
Joined: Thu Mar 22, 2018 3:02 am
Location: Washington State, USA

Re: Stuck on how to start a particular drawing?

Postby freedman » Fri Apr 03, 2020 9:42 pm

Looks good! You can put both rotational features in one polar array, if you like.
Attachments
cone11.JPG
cone11.JPG (62.43 KiB) Viewed 322 times