Create a rolled Ring

[sandroVJ8CB]

Hello everyone

I am trying to do something that I thought would be simple but is turning out to be pretty complicated. 

I simply want to create a "Ring" that will be bent at a uniform radius. This part is to slip over a branch pipe and then conform (roll) to a larger header pipe. I will flatten the part and then export the dxf to have the proper profile cut and sent to our rolling supplier. I have attached a couple attempts to show this. 

What I can not figure out how to do is get a UNIFORM ring width. I can create the right radius to match the header pipe but if I create a sketch on a flat plane of the ring, the sides are elongated. 

If I create the ring in 2D first, and then bend the part to the right radius, the hole in the middle will be oval and will not slip over a pipe. This hole must be perfectly round on the bent part but when flattened would be oval. The problem with this method is now the sides are narrower. 

Essentially on a flattened model, both ID and OD would be oval but there would be a uniform width between them. 

Please help!

[CCarreiras]

Hi!

I believe it's this:

Note: the sides should always be slightly elongated due the curvature.

Note: both cuts as Normal.

Check the part attached, and give your feedback.

[johnsonshiue]

Hi! Another way to do this is to use Cut Normal option. In your case, you may want to thicken the half cylinder first. Then use Cut command in Sheet Metal (turn on Cut Normal) to cut the sheet. The result should be quite similar but not identical. Cut Normal might be what you are looking for.

Many thanks!

[SBix26]

Here's your file with a little different solution.  Since a uniform width of the ring is important to you, I trimmed the cylindrical surface first to the ID size, then used Extend Surface to extend it outward by the Side_Mat amount, then used the second trim operation to remove the ID (leaving only the extended surface).  After thickening, I think this is what you are asking for.

The attached file is Inventor 2022 format.

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Sam B

Inventor Pro 2024.2 | Windows 11 Home 23H2

[kacper.suchomski]

Hi

1. Should the ring be bent in one direction? Is it cone-like in all of them?
2. How will the ring be cut? On a 3-axis or 5-axis machine?

This is key information for the created model to be technologically advanced.

[IgorMir]

Hi Sandro,

To create what you are after is not exactly a one click away process. Depending on what accuracy do you require - here are two models. IV2020 format. On a top of what Sam and Carlos have offered.
Part1 is simpler to model. Pipe reinforcing pad.ipt is a bit more elaborated.  Both of them would require a weld preparation, depending on a thickness of the pad.
As for the accuracy of modeling itself - I would have evaluated cost/benefit first. The item is nothing but a ruff pad. I would imagine, that the tolerances within +/- 2mm. should be more than sufficient enough for this particular design. 

Having said that - I am not advocating for a lousy designs. Only for a common sense. 🙂
Cheers,

Igor.

[sandroVJ8CB]

Thank you everybody, I really appreciate the help. Your models are all making me feel far less advanced than I thought I was with this program! You all seem to understand what it is im trying to do but when I create a drawing of the flattened model and dimension it, im still not getting the result I want of a uniform width, or on the folded part, the ID is not a perfect circle that a pipe can slip through. 

Igor, your "Pipe Reinforcement Pad" may be what I am looking for. There are so many steps and features in this part that I dont think I could ever personally replicate it. You are right about the tolerances, I can accept +/- 2mm no problem as this part will be welded anyway, as long as it actually fits over the pipe without grinding the ID. I dimensioned your flattened model and I think it is what I am looking for however I have one concern. It appears you used a pipe size of 300mm for the ID, but the flattened model dimension shows 320mm top to bottom. I do not beleive the top to bottom dimension should change at all from folded to flat part and 20mm is too much of a gap for weld. If that issue can be eliminated than I think this is the way I want to go. I feel like I cant perform half the methods you used on this model so If you would be so kind could you PLEASE use the following parameters?

Header (main trunk) Diameter = 44in

Plate ID (branch pipe OD) = 18in

uniform ring width = 8in

I greatly appreciate the help!

Thanks, 

Sandro

[kacper.suchomski]

From the moment you start this topic, you've been struggling with math all the time.

And you can't win this 🙂

You cannot expect tangency for the bent part (section) and at the same time equal length with the straight part (section). These requirements are mutually exclusive.

The way to model such parts isn't always intuitive, but a lot of this discussion stems from a misunderstanding of basic math, not Inventor.

And as I mentioned, the discussion should start with the manufacturing technology - because it determines the geometric requirements.

Below is an example of modeling for cutting machines (laser, plasma, etc.), taking into account the machine specifications - a variant for a 3- and 5-axis head:

In both cases, you can add the diameter offsets mentioned in the discussion at the end, using the Thicken tool (cut mode) for "cylindrical" surfaces. This way you will build tolerance.

There still remains the issue of circular holes, if they are required - but here we come back to the point - first, we need to determine the manufacturing and connection technology (the role of the holes) - the modeling process is secondary; it is a resultant, not a condition.

Good luck

[SBix26]

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@sandroVJ8CB wrote:

You all seem to understand what it is im trying to do but when I create a drawing of the flattened model and dimension it, im still not getting the result I want of a uniform width, or on the folded part, the ID is not a perfect circle that a pipe can slip through. 

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??  When I create a drawing of the model I provided, I see a perfect circle through the center (same as the Cut_Out_Size parameter in your model), and a nearly uniform ring width, which will vary a bit because of the rolling operation.  Is a difference of 0.077 inch too much?

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Sam B

Inventor Pro 2024.2 | Windows 11 Home 23H2

[IgorMir]

Hi Sandro,
You have to accept one axiom: The arc is always longer than its chord. 
Here is a model you have asked for.
Cheers,

Igor.

[IgorMir]

Hi Kasper,

I can't open your model but I think the way you do it doesn't deliver a uniform width of the reinforcing pad all way around. Could you please check it out? To see the discrepancy the model should be measured at different cross-sections - not just at quadrants.
Cheers,

Igor.

[sandroVJ8CB]

Sam, I appreciate you taking the time to try to help me. Your model is very close to what I am looking for however when I opened it and tried it out I realized the header diameter was set as the radius so it was double the size. when corrected the bend it more dramatic. when this was flattened, i got the result in the picture below. Now the sides are over 1/4" smaller which to be honest still may be acceptable for this application however I am planning on using this model for the future which includes all different parameters for the header, branch, flange width, and thickness. If I had a crystal ball and could see no matter what the configuration the worst it would be is 1/4", id probably accept this model. However since I am just starting to try to get this figured out and it seemed relatively easy (at the start) I figured id try to get it as close to perfect as possible. Thanks Again.

[sandroVJ8CB]

sorry forgot to mention, not sure if you can see it in the picture i posted but for some reason the centerline on the flattened model is skewed which causes some difficulty dimensioning. I cant explain this.

[sandroVJ8CB]

Igor, 

Thank you so much for building this model for me, This appears to be perfect for this specific application. I also appreciate the other models showing how it will be used. This is exactly what it will be used for. 

I only have one problem that is not making sense to me. As I just explained to Sam, I was planning on using this model for all future applications that require this design with the same parameters but different values. I thought it would be as easy as changing the values in the model but I am quickly met with tons of errors. Your Header diameter wasnt exactly 44", it was something like 42.5" and even just changing that small value created all kinds of errors. Do you think what I am looking to do is possible?

[kacper.suchomski]

@IgorMir  you wrote:

I can't open your model

I didn't include any model, so I'm not sure if this comment is directed at me.

So I recorded a video presenting one of many potential solutions, the development of which takes 3 minutes with a coffee break.

I think the way you do it doesn't deliver a uniform width of the reinforcing pad all way around.

Yes, because it is mathematically impossible if the washer is to be tangent to a large pipe around its entire circumference.

This whole discussion is wrong. The topic should be approached in the following way:

1. Determining technological requirements - if you use a specific plant (machine park), you must adapt to it. The designer's duty is to serve the technologist.
   And this was not defined in the content of the post.
   
2. Determining functional (and geometric) requirements.
   These, in turn, were defined contradictorily.
   
   1. If we keep the width constant, we will not get contact with a large pipe around the entire circumference.
   2. If we want to maintain contact with a large pipe - we will not keep the width of the ring.
      
      This is math. You can't fight it because you can't win it. This must be understood, acknowledged and taken into account in the process. Avoiding and insulting will not solve the problem.
      

I want to be well understood - surely one of us will eventually be able to help the student. But it will be a matter of lotery, not meritocracy.

We still don't have consistent requirements, so all our proposals (mine too) are a product of chance, our own experiences and interpretations; rather than a substantive approach to a specific case study.

And we won't get past this without specifying clear requirements.

This will result in a third day of fighting the three-minute topic.

In addition, if anyone accidentally provides a good solution, the student will not understand the source of the problem and will make the same mistakes in subsequent projects.

Since we have a platform for sharing knowledge, let's focus first on exchanging knowledge, not wishes and pats.

[sandroVJ8CB]

Sam, Quick Update...I have been going through each step over and over again and this method seems to be the easiest and make the most sense to me. I dont understand why when I changed your header radius there was a 1/4" discrepancy so i tried to replicate your model. I must be doing something wrong because i get to the stage in the picture below, ready to "extend surface". when I go to extend the ID, it will only allow me to do this inwards whereas yours only goes outwards (ideal). Any ideas?

[CCarreiras]

All the people are increasing the complexity to create this model.... to get all the same final result.

As @kacper.suchomski said, it will be always a small discrepancy between the flat and the bended part.
In real world, if the the flat is a circle, the bend model will be an ellipse and vice versa... 

... and... Creating a complicated model will make it difficult to create a simple working parametric model...

 

[kacper.suchomski]

@CCarreiras

Chris, I managed to meet the equal width condition in flat pattern. Descriptive geometry is the key.
But I still think it's a whim and doesn't make any sense.

@SBix26 

Samuel, the key is the neutral surface. When you create a model based on the dimensions of one of the boundary surfaces, it will happen that the size in the straight direction remains constant, but in the arc direction it increases; this creates an unevenness in the flat pattern.

This model can be freely parameterized and a configurator can be created for all values - inner pipe, outer pipe, thickness and radius.

I actually made the same extreme model as in the first video, only this time I included a second set of requirements - an equal width flat pattern.
Of course, this resulted in the loss of adhesion to the pipe, because these requirements are logically contradictory and cannot be reconciled.

But we're still back to square one.

A circle in a projected section = an ellipse in a flat pattern.
A circle in a flat pattern = an ellipse in cross-sectional projection.

There is really no escaping it. Dear friends, please, we should not fight with mathematics.

At this point the contact is linear with the large pipe and point-like with the small pipe.
In my opinion, this doesn't work.

Additionally, there are unnecessary (and maybe even harmful) empty spaces.

At this point, the person asking still:

1. did not specify the required implementation technology
2. did not improve his expectations, even though I repeatedly explained that they were mutually exclusive and could not be met simultaneously
3. focuses on unimportant details instead of usability and technological features

I'm starting to suspect that this isn't a production topic, but a homework assignment that can't be discussed.

[IgorMir]

If you bend a standard washer - it won't provide an equal gap around the adjoining pipe. It will have to be trimmed to fit over. Thus - making the final width of it uneven.
The object of the exercise has always been to create an item with the equal width all way around while it is fit to the job. I think - it has been achieved successfully. The minimum gap will be transferring from top face to the bottom face. Which is understood. To get the inner face tangent all way around to the adjoining pipe (small one) - an extra machining step got to be taken. But I doubt - it is feasible for this particular application.
I have provided an example of it. To get even more accurate item - the model should be Thickening symmetrically. But that's up to a designer which technique to use.  
Cheers,

Igor.

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@kacper.suchomski wrote:

@IgorMir  you wrote:

I think the way you do it doesn't deliver a uniform width of the reinforcing pad all way around.

Yes, because it is mathematically impossible if the washer is to be tangent to a large pipe around its entire circumference.

[kacper.suchomski]

If you bend a standard washer - it won't provide an equal gap around the adjoining pipe. It will have to be trimmed to fit over. Thus - making the final width of it uneven.

Dear @IgorMir , You don't have to explain the basic principles of geometry to me, because from the very beginning I have been vocal about following them.

To get even more accurate item - the model should be Thickening symmetrically. But that's up to a designer which technique to use.

Not completely. It should be bolded asymmetrically, according to the value of the K factor. Symmetrical bolding will only be OK if the K factor is 0.5. But this will be a special case, not the rule, as you wrote.