Stitch Cutting Sheet Metal

[Anonymous]

We fabricate cylindrical steel tanks and are beginning to use Inventor flat patterns to generate CNC burns for tank shells. This works exceedingly well and saves tons of time in the weld shop but we ran into a problem. When we pre-burn a large hole in the tank shell (for manways or large pipe etc.), the flat plate will "kink," roll too tight of a radius, in the vicinity of the hole because of the lack of metal to dissipate the pressure from the rollers. We solved this problem by stitch cutting large holes so the material stays in place for the roller, but can be quickly removed by the welders. 

Right now we copy the flat pattern into autocadd and trim sections of the holes out then generate burn files using ProNest. This is tedious and inconsistent. Does Inventor currently have any tools to accommodate perforated cuts in flat patterns?

Example shell attached.

[Curtis_Waguespack]

Hi ascott_shipco, 

I think a Punch created like in the attached example might be the way to go.

Note that you might set up the punch a bit differently than my simple example ( maybe you to specify the tab width not the stitch cut width, etc.), but this might give you an idea to work with.

I hope this helps.
Best of luck to you in all of your Inventor pursuits,
Curtis
http://inventortrenches.blogspot.com

[Anonymous]

WE use Vault so copy design would be simple for us.

My method would be to add the center of the hole and the slots for stitch cutting in the flat pattern.

Then use copy design for tanks going forward, if sketching correctly the flat pattern changes should stay in place.

[Anonymous]

Using an unfold becomes more time consuming than the autocadd transfer because we'd have to recalculate locations by arc lengths. Not hard, just... time. We also use these hole locations to constrain all the fittings that go into the tank and produce weld drawings. 

We do have vault and we use design copy but we are constantly moving fittings for custom designs.

To make it more interesting, we don't give these stitch cuts any depth. They are just lines because the plasma table doesn't need to cut sections, just trace pieces of the hole's outline. 

[IgorMir]

Hi Ascott,

Another idea is to edit the flat pattern itself. That way the plasma cutter gets what is needed yet the model itself represents the final item.

I have attached your file with the flat pattern modified. But it needs some more work on it. 🙂

Cheers,

Igor.

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@Anonymous wrote:

We fabricate cylindrical steel tanks and are beginning to use Inventor flat patterns to generate CNC burns for tank shells. This works exceedingly well and saves tons of time in the weld shop but we ran into a problem. When we pre-burn a large hole in the tank shell (for manways or large pipe etc.), the flat plate will "kink," roll too tight of a radius, in the vicinity of the hole because of the lack of metal to dissipate the pressure from the rollers. We solved this problem by stitch cutting large holes so the material stays in place for the roller, but can be quickly removed by the welders. 

Right now we copy the flat pattern into autocadd and trim sections of the holes out then generate burn files using ProNest. This is tedious and inconsistent. Does Inventor currently have any tools to accommodate perforated cuts in flat patterns?

Example shell attached.

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