NX5 Sheet Metal - Outside Mold Line Display

Most questioners provide too little, so congratulations on being the exception who asks so much that I'm not sure what the question is.

Yes you can make a flat pattern in NX. You need an "NX Sheet metal" license to do so at the very least. There is an advanced sheet metal license at extra cost that contains a capability for much the same thing as a set of curves that may require less preparatory modelling, and which I actually prefer. If all you make are flat patterns then you might want to at least request a demo of it from your local sales guys.

Are flat patterns useful. Yes of course. The manufacturing shop generally needs the profile to cut and where to bend the part. We generally provide them with a DXF for the profile and dimensions to the bend centrelines shown on the drawings. We also dimension inside bend radii on separate views and sections as required. For straight up and down sheet metal that is I think about as much as anyone needs.

If the shape and design involve variable angles blends around curved profiles, (aircraft fuselage and wing sections typically have a lot of those), then you probably will need the advanced sheet metal. At that level of complexity you'll need tooling for the job, require accurate flat patterns and may describe the flange lengths a little differently in more detail on the drawing.

Some of the information that may have been carried on older drawings shouldn't be necessary in today's environment. The calculation of bend allowance neutral axis value etc may have been a cross check for those developing flat patterns manually. These days that information is contained/embedded within the CAD file and the development is 100% as reliable as you can ever make it, (obviously some very complex forming notwithstanding). So you could show less of that on the drawing. Instead I'd keep it simple clear and uncluttered to make it easier to read if anything and avoid OML's if they aren't going to be used in the bending shop.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum

While someone might wish to dimension to the outer mold-line, the truth is that for straight-break sheetmetal, the flat-pattern is laid-out, sheared/punched and then formed based almost always on the inner mold-line dimensions and specifications, such as the inside bend radius.

Looking at your parts, I can't see what the 'problems' are. The drawings look just like I would have expected them to be.

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Cypress, CA

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

Thanks for the responses.

The "problem" per se is that i'd like to see the Outer (or Inner) Mold lines on the flat pattern. I cycle through the flat pattern display to see what NX means and will display for Bend Center, Joggle, Interior, etc. When I have Inner or Outer Mold selected and Bend Tangent off, I don't have any lines displayed where I would expect them. If I wanted to dimension to the mold lines I have no way to see them and therefore I can't dimension to them.

What should I see for Inner (Outer) Mold lines in the flat pattern display?

I agree with Hudson that the flat pattern on the drawing is not needed in todays world. I tend to keep it simple and only dimension the formed part. I'll show a flat pattern as reference only on complicated bends to show what I was thinking when I developed the part.

Matt

I'm not sure what you mean you say that you can't see any lines on the flat-pattern. Below is a 'snapshot' of what I see when I open your drawing in NX 5.0.6.3:



John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Cypress, CA

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

Maybe I don't understand what the purpose of the mold lines (inner and outer) are. I hope that the attached PDF clarifies.

I change flat pattern preferenes to bend CL & tangent lines (slide 1) and I see them. When I turn off bend tangent lines and select inner or outer mold lines I see only the bend CL.

The attached shots are from the flat pattern in the model.

Thank you,
Matt

Those ARE the 'lines' which will be used to form a straight break sheet metal part, which is all that I have direct experience with, both in terms of the software and actually designing sheet metal parts (mostly machinery guards and enclosures as well well as some HVAC ductwork). Note that the ONLY time I've every heard the term 'Mold Line' used was when working with people familiar with Aerospace Sheet Metal applications (which I have NO direct experience with).

John R. Baker, P.E.
Product 'Evangelist'
Product Design Solutions
Siemens PLM Software Inc.
Cypress, CA

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

Spacecow,

What you're actually displaying is what most people usually display which is the Bend Centre and Bend Tangent lines.

I have created as you should a very simple example of a flat pattern. If you look at the attached PDF then you'll see that I've made a quick and dirty over dimensioned drawing that analyses everything about what is being produced in the flat pattern. The boxed dimensions for the purposes of this exercise are shown as such to indicate dimensions that wouldn't ordinarily appear on the drawing.

I would ordinarily show the left hand (or central) flat pattern view dimensioned pretty much as shown here. You need it because with bend allowance the overall length and 23 dimensions aren't shown elsewhere. So the workshop would otherwise have to make a calculation that they could get wrong.

As I said we'd often supply a DXF to cut the flat pattern profile to but that still need to know where the bends fall and the bend allowance calculation that determines it is something we prefer to take from CAD.

You might also want to change the settings in your customer defaults so that the changes you've made to the flat pattern display are set permanently.
Also
The right hand flat pattern view is the same as the left one except that I suggested a way of showing and changing the standard annotations to something I thing many would find more suitable. What I'm showing is something based on an older Aircraft style standard annotation which you might like to adopt since the system supports it quite nicely.

Best Regards

Hudson

www.jamb.com.au

Nil Desperandum illegitimi non carborundum