Modeling tip request

Tim Neumann

 Attached you'll see a drawing showing a 3D layout of a conical section for a pressure vessel. Welded to this are four platform supports with reinforcement pads, which took me forever to create hence my post. Can anyone come up with a easy/quick method(s) to model the pads? I ended up revolving the profile about the cone a full 360 degrees and then creating to solids to trim it to correct width (by subtraction). This created (2) pads which I then used the separate command so they wouldn't be linked. This took me over an hour so surely there is a quicker method. Thanks for any comments/advice!

Joe Dunfee

 The only alternative approach I can think of is to copy the original cone to the side.  I would typically just choose a round number, such as 100 for the distance, so that I can move it back to the original position.  Or alternatively, put the copy on a new layer, and turn off the layer of the original cone. Then, offset the outer surface the thickness of your pad, and offset the inner surface the same amount inward.

There is actually another, potentially simpler, approach.  Remember the purpose of your drawings is for the fabricators   Are they going to curve the pad or leave it flat?  If it is going to be flat, then model it that way. If curved, how are you going to tell them to make it?  Will you tell them an inner radius, and they will fabricate it, not as a cone, but as a cylinder with that inner radius?  However you intend to instruct them, be sure to model it that same way.  This way, you may be making it easier to model, but most importantly, you are testing the manufacturing method, and seeing how that approach fits on the model.

-Joe

Richard Webb

 Joe has a good point. My first attempt just involved making an 8 x 20 x 3/8 flat plate and inserting it as a block using dynamic UCS to place it on the midpoint of the quadrant-quadrant line. The original has it a bit farther down than the midpoint but that's a quick target and the whole operation just took a few moments. But that doesn't match the fit-to-face of the original.

"Shell" the original cone by -.375 to get a 3/8 thick entity, extrude the inner face of the flat plate just a bit and then intersect the two solids sort of does the trick. Challenging to machine, though. 

Tim Neumann

 Thanks Richard and Joe. Our shop processes are not modern by any stretch but mostly use "blacksmith" methods - cut plate to shown size then put in press brake for multiple breaks, then beat with hammer to suit. Anyways, I tried to use the project sketch command but being unfamiliar with it that approach bombed, though on a regular cylinder was able to project a circle to the surface and then extrude that to whatever thickness. With a cone success eludes me, anyone want to take up the challenge?

Joe Dunfee

First, let me say that I have no idea of your level of experience, and I have no exposure to pressure vessel industry. So, all my comments are somewhat speculative. But, I know there are rollers for manufacturing cylindrical tanks to curl the metal plates. So, I imagine there is some way to roll your cone from plate material. But, in actual practice, the approach may vary with the situation and plate size.

As a young CAD guy, with absolutely no exposure to manufacturing processes, I soon realized that the shop guys were my main customer.  My job was to make their work easier. And I learned that some of the stuff I was drawing was just being ignored.  So, learning their needs even made my job easier, since I was more focused on what was needed. That is why I made the statement that you might model it based on the manufacturing process.  Though, even that may not be necessary.  

Drafting is really a simplification of the real world. And sometimes even the simplification is more than what is necessary.  You sometimes put a leader pointing to a spot and say, "Add mounting plate here", and don't even draw it.  This is for when the shop already knows what to do, either from established practices that are not documented, or preferably in a printed book of "established practices".  Though, I am sure the pressure vessel industry has to be very detailed in their documentation.

-Joe

Joe Dunfee

 It seems we were both typing responses at the same time.

Anyway, it seems that you are over-modeling the part for what your shop does. And your CAD model is still not an exact match for what the shop will do, since it is a craftsman's work to do it right.  And I do value the true craftsman, since I know that they know their own work better than I do.

At one company, I used to do bend calculations and create flat patterns for thin sheet metal parts.  But, I later learned that the guy making the part was a local Amish man, who ignored my flat patterns. He just fabricated the part based on what the finished dimensions should be. He was a craftsman who knew his work.  My more technological approach would be better if the flat pattern were being cut by laser, and then bent on a brake with dies.   By the way, there is a local shop owned by some Amish guys, and they do have a laser capable of cutting 1" steel plate.  They are not anti-technology. Just more limited in how much technology they adopt.

-Joe

Patrik Sparrman

If you are serious about 3d You really need tp be on V16 check the vessel tutorials. https://www.bricsys.tv/#3d-modeling Way more useful than earlier versions.

Patrik Sparrman

OK this is my take on this. in all appr 8 minutes. BUT I did not use your dimensions and did not drill the holes and only made one copy.

https://www.dropbox.com/s/6902mj3wprgf3yg/SNAP1.mp4?dl=0

Patrik Sparrman

crap wrong video https://www.dropbox.com/s/c3vu44wh1gmvklv/Screen%2009-26-2016%2017-21-50.avi?dl=0

Tim Neumann

 Thanks for the video Patrik! It would be nice if they could add (2) options for revolving into a solid: extrude in both directions and specify the width instead of just in degrees. All in all they're making it easier to model in 3D. 

Patrik Sparrman

What 2 options do you want? Extrude in 2 directions feels a bit odd. The only reason I did that was that I wanted to keep it centered to the cone. I created the cone by revolving as it seemed easier especially for the plate.

Tim Neumann

 For what it's worth, a different approach:

1. Draw 3D cone

2. Draw 2D profile of pad

3. Orient profile "normal" to cone surface (draw a line quadrant to quadrant on cone for reference)

4. Extrude profile with limit being o.s. cone surface

5. Freeze cone layer so it's hidden

6. Use thicken command and pick "backside" of extrusion. Thicken outward per whatever it needs to be

7. Delete extrusion

8. Unfreeze cone

See result per attached image.

cone pad.jpg

Joe Dunfee

 I am on ver14, and I am not aware of all the additions to modeling. But, if it is not already there, I personally would like the ability to extrude a profile in both directions.  This is because it is common to need to make part that is at least partially symmetrical. I also suspect it is an easy feature to add.  Just extrude the solid the full amount, and then move it the opposite direction by half the full amount.  I suspose the only challenge to doing it as LISP, is that you must first set your UCS to the polyline to be extruded.

-Joe

Patrik Sparrman

Not a bad idea the more I think about it I will post a request.