How do I make the flat piece meet cylinder smoothly?

cleeve_breen

Hi there,

I am attempting to teach myself beginner cad by finding mechanical drawings and trying to model them and I feel like I am stuck on a rookie technique. I cant get the 'wings' to meet with the cylinder at the top of the model without a little piece sticking out of the circle, I hope that makes sense.
When I initially tried to extrude the cylinder I got the 'boolean operation would result in non-manifold bodies' error which after googling is possibly because it only meets on one edge of the 'wings', so I added an extrusion on both sides but they didnt wrap around the curve.
Again I hope this makes sense and feel like its a beginner issue I just cant figure out. 
Help would be greatly appreciated, cheers.



https://cad.onshape.com/documents/8ae0c4d0a56c7e3dc0dd9574/w/05ac87d926fb67f148ada234/e/5d42eb2493459f7c66a92bac

rick_randall

I agree with glen, in addition I have a couple of modeling solutions you might want to consider (it's all about design intent).

https://cad.onshape.com/documents/e8102715b095e8e1756d7f14/w/aec35d21769220425e76c498/e/76397e547fad7dd91900a7cb

at the top of the feature tree, you can toggle between two different configurations

Option 1) inset profile - by altering the profile of the web slightly, you eliminate the issues caused by that tangent point at the top cylindrical edge. Or

Option 2) crowned web - by creating a crown on top of the web, this blends the edge of the web to  the circular edge of the cylinder (but will create new issues at the other end - this is not shown).

These solutions are just food for thought, remember it's all about getting what you want.

Keep it up - your stuff looks good so far ( Hint : try modeling the same part several times and try to simplify the feature tree each time).

glen_dewsbury

Your question does make sense because of the non manifold condition. I tried to use the rib tool and had the same issue. I made a rib profile (wing) with a small over lap then extruded. 
https://cad.onshape.com/documents/6b242e8ad414ef0048f1af5b/w/18e48b804276b5b1abfb7a16/e/0f49b514b6a40ebc651a1f1d
You may want to go through the intro basic courses. They're free and could save a lot of time in the long run. Notice the reduction of features between yours and my versions. Also more robust and simpler to update.
https://learn.onshape.com/catalog?labels=%5B%22Self-Paced%20Courses%22%5D&values=%5B%22All%22%5D

rick_randall

I agree with glen, in addition I have a couple of modeling solutions you might want to consider (it's all about design intent).

https://cad.onshape.com/documents/e8102715b095e8e1756d7f14/w/aec35d21769220425e76c498/e/76397e547fad7dd91900a7cb

at the top of the feature tree, you can toggle between two different configurations

Option 1) inset profile - by altering the profile of the web slightly, you eliminate the issues caused by that tangent point at the top cylindrical edge. Or

Option 2) crowned web - by creating a crown on top of the web, this blends the edge of the web to  the circular edge of the cylinder (but will create new issues at the other end - this is not shown).

These solutions are just food for thought, remember it's all about getting what you want.

Keep it up - your stuff looks good so far ( Hint : try modeling the same part several times and try to simplify the feature tree each time).

cleeve_breen

rick_randall said:

I agree with glen, in addition I have a couple of modeling solutions you might want to consider (it's all about design intent).

https://cad.onshape.com/documents/e8102715b095e8e1756d7f14/w/aec35d21769220425e76c498/e/76397e547fad7dd91900a7cb

at the top of the feature tree, you can toggle between two different configurations

Option 1) inset profile - by altering the profile of the web slightly, you eliminate the issues caused by that tangent point at the top cylindrical edge. Or

Option 2) crowned web - by creating a crown on top of the web, this blends the edge of the web to  the circular edge of the cylinder (but will create new issues at the other end - this is not shown).

These solutions are just food for thought, remember it's all about getting what you want.

Keep it up - your stuff looks good so far ( Hint : try modeling the same part several times and try to simplify the feature tree each time).

Thank you for your advice and kind words, much appreciated Rick.

cleeve_breen

Cheers for the advice Rick and Glen.

cleeve_breen

@rick_randall @glen_dewsbury

Hi again,
I have been going through your suggestions and while your help on work flow and simplifying the feature tree is absolutely fantastic and have taught me quite a number of things I feel like my original questions is still open and unanswered. 
Rick in your option 2 as you say it works great at the top of the cylinder but then continues the curve at the bottom which as you pointed out creates new issues. 
I have included an image of the drawing that I was working from (random image from the web) and have circled the area which is causing the issue, as you can see the top of the rib (wing) meets the cylinder curve evenly and the bottom meets the straight edge, is this possible to achieve? 

 

I hope I dont seem ungrateful, I just feel like I am no closer to solving the problem. 

eric_pesty

cleeve_breen said:

@rick_randall @glen_dewsbury

Hi again,
I have been going through your suggestions and while your help on work flow and simplifying the feature tree is absolutely fantastic and have taught me quite a number of things I feel like my original questions is still open and unanswered. 
Rick in your option 2 as you say it works great at the top of the cylinder but then continues the curve at the bottom which as you pointed out creates new issues. 
I have included an image of the drawing that I was working from (random image from the web) and have circled the area which is causing the issue, as you can see the top of the rib (wing) meets the cylinder curve evenly and the bottom meets the straight edge, is this possible to achieve? 

 

I hope I dont seem ungrateful, I just feel like I am no closer to solving the problem. 

I think the issue is that this is a drawing that was created by hand and it's actually not "correct", it's like one of these impossible perspective drawings from MC Escher. In the real world if your rib is tangent to circle in the section view, there has to be a small straight section at the top away from the centerline.
You could do a lofted cut so that the top face of the rib is curved at the top and straight at the bottom but that's not how it would be manufactured (and would also look incorrect on the drawing). The only other option to get rid of these edges without making the top of rib non-planar is to have a flat in the circular boss from the top view but that won't match the drawing either...

_anton

Thanks for the speed CAD practice, I now have a greater respect for those people.

@eric_pesty is right, of course - the part is straight-up geometrically impossible without very small edges or faces or some lofting magic. I'd personally do it like this so that the top face is actually circular: https://cad.onshape.com/documents/700d1091ef0c460201d3cc9c/w/3bec45ffc404644d0462ee87/e/fa33f7319fb0de159ee09679

eric_pesty

@_anton
That would be hard to manufacture!
I think this is probably how it would be made in practice, deleting the little bit of the circular boss the way you had it: 



This way there are no "small edges" anywhere, just a little flat spot in the circular boss profile. Of course the height of that face is only about 0.16 mm at its highest so in practice it doesn't really matter (hence when it was drawn by hand this kind of small detail was ignored!)

_anton

Anton is not a mechanical engineer, just trying to orient by what the convenient geometry in CAD would be.

cleeve_breen

@eric_pesty & @_anton

Cheers for taking the time lads, Im learning so much from this little exercise

john_lopez363

@cleeve_breen ... You can have both the top and bottom of the gusset be flush with their respective faces/planes...but to achieve that the top surface of the gusset will end up with a slight crown to it, starting at the top and then blending to a flat as it approaches the very bottom.

john_lopez363

...and a section view

cleeve_breen

john_lopez363 said:

@cleeve_breen ... You can have both the top and bottom of the gusset be flush with their respective faces/planes...but to achieve that the top surface of the gusset will end up with a slight crown to it, starting at the top and then blending to a flat as it approaches the very bottom.

Hi John, as I have said to the others thank you for taking the time to answer my problem, would you have an OnShape link for you solution, as I am a complete rookie it would really help me understand what you have done?  
I very much appreciate you help.

john_lopez363

@cleeve_breen.... happy to share.  First thing to keep in mind is that there are usually many ways to model an object in OnShape...not so much with this gusset feature though.

For the main body and the top boss of the model it does not matter how you get there, as long as it is the result you want...just save the gusset(s) as the final feature to create.   

For the gusset, you will need to create it using a Loft feature.  This is the only way (as far as I know) to get the gusset to meet the cylinder face of the top boss fully flush.

Of course the Loft needs at least two profiles to work (a sketch and a split face in this case).

• I created the bottom profile (called Bottom Loft Sketch) as a simple rectangle on the face of the flange, paying particular attention to ensure the sketch intersects the outer edge of the flange and vertical wall of the main body (be sure to look at the constraints I've used).
• I created the top profile (cleverly enough called Top Loft Sketch...lol) again as a simple rectangle on the Front plane. This time paying attention to ensure the bottom edge of the rectangle is coincident and mid point to the center point of circle sketch of the Boss. 
  
• The next trick was to use a Wrap feature using the Split boolean operator with the face of the boss cylinder as it's Target.  This creates a new face on the cylinder that will be used for the subsequent Loft feature of the gusset.
• At this point, just simply Loft between the "Split Face" on the cylinder and the Bottom Loft Sketch.  This creates your gusset. There will be some "extra" geometry on the inside of the U-Shape of the main body that needs to be removed.  This is done with a simple Extrude remove once you've created the necessary profile.
  
• Lastly, and for efficiency sake, I used a Mirror Part feature to create the second gusset and boolean everything into a single part.

Happy learning!


Here's the link:
https://cad.onshape.com/documents/b967cb3d7366964c4501c3c0/w/e384397e707f5316d5527451/e/71f5227ebcc0f28cbe1bcee7

cleeve_breen

john_lopez363 said:

@cleeve_breen.... happy to share.  First thing to keep in mind is that there are usually many ways to model an object in OnShape...not so much with this gusset feature though.

For the main body and the top boss of the model it does not matter how you get there, as long as it is the result you want...just save the gusset(s) as the final feature to create.   

For the gusset, you will need to create it using a Loft feature.  This is the only way (as far as I know) to get the gusset to meet the cylinder face of the top boss fully flush.

Of course the Loft needs at least two profiles to work (a sketch and a split face in this case).

• I created the bottom profile (called Bottom Loft Sketch) as a simple rectangle on the face of the flange, paying particular attention to ensure the sketch intersects the outer edge of the flange and vertical wall of the main body (be sure to look at the constraints I've used).
• I created the top profile (cleverly enough called Top Loft Sketch...lol) again as a simple rectangle on the Front plane. This time paying attention to ensure the bottom edge of the rectangle is coincident and mid point to the center point of circle sketch of the Boss. 
  
• The next trick was to use a Wrap feature using the Split boolean operator with the face of the boss cylinder as it's Target.  This creates a new face on the cylinder that will be used for the subsequent Loft feature of the gusset.
• At this point, just simply Loft between the "Split Face" on the cylinder and the Bottom Loft Sketch.  This creates your gusset. There will be some "extra" geometry on the inside of the U-Shape of the main body that needs to be removed.  This is done with a simple Extrude remove once you've created the necessary profile.
  
• Lastly, and for efficiency sake, I used a Mirror Part feature to create the second gusset and boolean everything into a single part.

Happy learning!


Here's the link:
https://cad.onshape.com/documents/b967cb3d7366964c4501c3c0/w/e384397e707f5316d5527451/e/71f5227ebcc0f28cbe1bcee7

Wow, this is fantastic information, many thanks to you for taking the time and I'm looking forward to going through it.

Again much appreciated