Forming a perforated sheet

[wiengines]

Someone asked me an interesting question which I did not have an answer for. So naturally, I figured I would ask you guys (and gals).

We take a piece of perforated sheet metal (.149in holes on .1875in spacing), and draw it into a round shape. So the question is there an easy way to model this so that each of the perforations are (relativly) close to where one would expect them to be after the part is formed?

The attached image shows the cross section of the formed part.

Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5

 

[JohnRBaker]

Are you sure that this is the correct image?

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
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[wiengines]

I'm sure. Our current model was created by sketching that profile and revolving it. The attached image was just a cross section through the revolved part.

Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5

 

[SamSlivinski]

If I am understanding your question correctly you could model the round shape and then create the perforations in a sketch and as long as they are in some sort of pattern you could quickly pattern them and have what you want

Sam Slivinski
Using NX 6
Manufacturing/Aerospace

 

[wiengines]

In a nutshell, yes. Where the model is somewhat flat, it isn't much of an issue to just sketch a few of the perforations, extrude and subtract, and using patterns to finish it off.

Where my co-worker is struggling is how to model the perforations on the vertical drawn sections without much effort.

Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5

 

[JohnRBaker]

I still am not getting what it is that you're attempting to model. Could you provide at least an image of what the actual part looks like, and if possible, some idea of what the 'perferations' look like? if you're asking what I suspect that you are, you'll probably have to wait until you upgrade to NX 8.5 before you will be able to do this in a reasonable way.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
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[JohnRBaker]

On second thought, if the metal is being deformed in TWO directions, the potential NX 8.5 approach probably won't help much.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
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Siemens PLM:
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To an Engineer, the glass is twice as big as it needs to be.

 

[cowski]

Do the perforations need to be modeled? If you were molding the part, I could see the need for the model to drive the tooling definition; but since you are forming a perforated sheet, wouldn't you just need the finished shape? Is the modeling of the perforations being done just for a visualization, or is there more to it?

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[looslib]

Modeling the perforations could also be required for FEA and visualization reasons.
Basic weight of the part can be manipulated in the file.


"Wildfires are dangerous, hard to control, and economically catastrophic."

Ben Loosli

 

[JohnRBaker]

Forming the part will have no effect on it's weight. All you need to do is figure out what the pre-deformed blank looks like and the weight can easily be determined. The only thing that a perforated 'before & after' results will useful for FEA purposes since the perforations will most likely have on impact on the behavior of the metal during deformation and of course could also help to determine what the appearance of the final part would look like if that appearance was critical for aesthetic reasons.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[capnhook]

Is there an easy way to model this so that each of the perforations are (relativly) close to where one would expect them to be after the part is formed?


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[SamSlivinski]

If you make a sketch and wrap it around the already formed part you will know exactly where they are.

Sam Slivinski
Using NX 6
Manufacturing/Aerospace

 

[wiengines]

Sorry it's taken me so long to respond, I got tied up with other things.

Typically, we don't even bother to attempt to model the perforations. From a design standpoint, there really isn't any value in it.

The reason this question is being asked is because of a couple of reasons that others have pointed out. This part is a rotating screen that is at the inlet of the cooling system on a air cooled engine. The purpose of the screen is to block as much debris as possible, but still let as much air pass through as possible.

Our people that handle the analysis of the cooling system performance would prefer if the perforations were in the model. As it is now, they guess the locations. For their purposes, I'm not entirely sure how critical it is for them to have each perforation at it's exact location.

Also, our people that create the service literature from our models have been asking for more realistic models for some time.

Is it a show-stopper if we can't do this? Nah, not really. It would be nice, but I suspect that if it was possible, the model would become quite large and take up quite a bit of computer resources to handle.

Attached is a picture of a similar part.



Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5

 

[ewh]

In my experience with smaller perforations through a slightly larger, thicker composite panel (1/2"), NX bogged down very quickly.

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[Toost]

Can you provide more details ?
( possibly a sample of the perforated sheet and a sample of the shape to follow )
I did a quick and dirty test to see if the Global Shaping feature could do it , and it seems quite promising, See attached image. ( Note that i started with a square perforated sheet which was larger than the shape i wrapped to, i have not tried to wrap a solid in this case.)
The Global Shaping is probably in the "NX_Freeform_2" license which not everybody has.
I can later upload the model, if interest exists. ( This one NX 8.5)

Regards,
Tomas

 

[wiengines]

I'm currently trying to model up a perforated sheet, but my computer is struggling with it at the moment [sadt

I haven't had the need to mess around with Global Shaping much, so I will have to take a look at it. I'd like to take a look at your model, but I'm on NX7.5 at the moment...

Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5

 

[Toost]

Hm, probably the Meta Form Feature is the more proper tool for this operation. It should be able to bend the perforated sheet onto a die. The Global shaping might produce something which looks correct but isn't.
I will play around with the model i have and see what i can come up with.

Regards,
Tomas

 

[GuyFromDenver]

I haven;t done any sheet metal design in NX yet, but in SolidWorks I would draw a perforated sheet then bend it. It would then represent the part as it would be if you did it for real

 

[JohnRBaker]

You can do the same thing with NX Sheet Metal as long as the bends are 'Straight-Brake'. It's the curved bends which are preventing this from being a trivial task.

John R. Baker, P.E.
Product 'Evangelist'
Product Engineering Software
Siemens PLM Software Inc.
Industry Sector
Cypress, CA
Siemens PLM:
UG/NX Museum:

To an Engineer, the glass is twice as big as it needs to be.

 

[wiengines]

Hmmm, Meta Form looks promising...the bad thing is my computer must know that today is Friday, because it seems like it decided to cut out of work early today

Looks like I will try to tackle this next week!

Chris T.
Project Design Analyst
Kohler Co. Engine Division
Using NX7.5