topic Re: Flat Stack Sheet Metal Extent in Inventor Forum

Flat Stack Sheet Metal Extent

phoenixwahoff — Thu, 01 Jun 2023 00:56:35 GMT

Hi Inventor Users,

I have a question regarding the sheet metal extent for NON folded parts.

I have a part made with an arc length of 2000mm as a surface extruded to 500mm in height. Now i thicken offset the surface to gain a solid body from it. Then i convert to sheet metal and pick the ,,base face,, so Inventor grabs the thickness of the part. Then by creating the ,,flat pattern,, i should get the extend length to be 2000mm and the extent width to be 500mm - But it seems not to work... I tried playing around with it and i cannot figure out why or even if its possible for inventor to do such.

I use the flat patterns to gain width , length & thickness for flat pieces all shapes etc, but curved parts i have the issue that it doesnt flatten it proper,..

Does anyone have an idea to lead me in the right direction?

Re: Flat Stack Sheet Metal Extent

pcrawley — Thu, 01 Jun 2023 02:03:06 GMT

Steps I followed:

Create a sketched arc of 2000mm length (unspecified centre/radius)
Extrude arc 500mm as a surface
Thicken - unspecified thickness (I chose 5mm)
"Convert to Sheet Metal"

I lost my way at "...and pick the ,,base face,, " - I'm not sure which function you are referring to?

To achieve the "Flat Pattern Extents" of 2000x500mm, I set the Sheet Metal style Thickness = 5mm (to match the "Thicken" feature) and created the Flat Pattern - which all worked as expected.

Can you let me know what I missed?

My model attempt is attached - up to converting it to sheet metal.

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Thu, 01 Jun 2023 12:35:59 GMT

Hello Peter,

Thanks for your reply. When you press the button convert to sheet metal the mouse pointer is asking for ,,select base face,, which in our case is the face it suppose to grab the sheet metal size from. That way it knows which way to put it on its flat.( does that make sense? ).

It does flatten it proper , but for some reason it either allows KFactor or some what bending allowance. Im wondering if i can somehow turn that allowance off so i can have a curved part to be flatten to grab the size off from it to then add them into my parameters for further operations...

Re: Flat Stack Sheet Metal Extent

johnsonshiue — Tue, 06 Jun 2023 21:45:57 GMT

Hi! This could be due to flat pattern orientation or the flat pattern coordinate system. Please share the file here so that the forum experts can help take a look.

Many thanks!

Re: Flat Stack Sheet Metal Extent

kacper.suchomski — Tue, 06 Jun 2023 23:10:04 GMT

There can be many reasons and scenarios, so it will be easier if you attach your file and describe the goal you are aiming for.

At the moment, I can see several potential scenarios:

Want to get a 2000x500 dxf file. If so, there's no point in opening Inventor. It's just a simple rectangle that you draw in any 2D CAD program. Why work 2 minutes in Inventor when you can do the same thing in 15 seconds in AutoCAD or any similar program.
However, if you want to do something more, remember that:
The dimensions of the development will correspond to the dimensions of the neutral axis (surface). So if you sketched an arc and made it thicker in one direction, the expansion will have different dimensions.
The proportion of the location of the neutral surface is defined by the K factor.
With small dimensions, the difference is practically imperceptible, but with large sizes, the differences are visible and affect the matching of details to the rest of the structure. Be sure to include this.
Paweł's case works without a problem, while there were plays that Inventor had a problem with interpreting arcs as a base. Then a small flat piece less than 1 mm long can be made to make the surface flat as a basis for identifying the thickness and direction of side A.

Re: Flat Stack Sheet Metal Extent

pcrawley — Wed, 07 Jun 2023 02:39:24 GMT

@phoenixwahoff - you are right - there is some 'phantom-k-factoring' at work here:

2024 model attached (in pre "Convert to Sheet Metal" state) if anyone else wants to test.

I now understand your workflow thanks - but I don't have an answer ☹️

Re: Flat Stack Sheet Metal Extent

johnsonshiue — Thu, 08 Jun 2023 19:45:19 GMT

Hi Folks,

By default, sheet metal K factor is 0.44, which means the neutral layer (the unfold length equals to the folded length) is at 44% of the thickness from the inner side. In order to have the unfold length equal to the folded length, the K factor has to be 0 (inside) or 1 (outside). In this case, simply change K factor to 1. The unfold length will be 2000mm. I am not seeing a bug here.

Many thanks!

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Thu, 08 Jun 2023 19:54:14 GMT

Hi there,

Yes thats the exact thing i do as well - (At least for this example) - Since its a bend rolled piece there should be no bend allowance nor other allowance included as the part remains at its ,,2000mm,, in this example. It should be treated as a flat stack material - which it doesnt. I actually ended up setting the k-factor to 1 and saved it as a template. That works for most of the cases i have , but does not work with out a mistake.

It would be nice if the drawn part and the sheet metal flat pattern could match - since i use ,,make components,, to go from a solid body model to my components - then i convert to sheet metal and ,,lay these parts flat,, to be able to get the cut width & cut length of from it. it works for all components we have )mostly rectangular pieces - but curved parts it doesnt. Though i had it figured out in Inventor 2019 as far as i know - ill take a look at that tonight and will keep you posted.

It seems like that there is a hidden factor somewhere as the width and thickness are correct - length (or the ,,rolled side) doesnt show up correct

Re: Flat Stack Sheet Metal Extent

Frederick_Law — Thu, 08 Jun 2023 22:55:34 GMT

Please attach your file.

First did you setup Sheet Metal Rules with 500mm thickness?

Which direction did you thicken it? Away from center or toward center?

I'll thicken midplane and k = 0.5

For round part, k=1 is OD, k=0 is ID.

Re: Flat Stack Sheet Metal Extent

pcrawley — Thu, 08 Jun 2023 23:13:08 GMT

**** - I missed that! The @johnsonshiue genius strikes again.

Of course - the Kfactor should be 1, not 0 as I showed.

If you pick the original 2m face as the "Base face" and have Kfactor=1, it works perfectly:

Can't believe I missed that sorry - hope it works for you @phoenixwahoff

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Fri, 09 Jun 2023 15:38:32 GMT

Yes thats true - But as soon you do the thicken offset to the other direction it results in error again. I plaid with the K-Factor a lot and even one doesnt work as far as i know. Yes for this example it does - but if you switch the thicken offset it wont give you the 2000mm.....

Any ideas?

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Fri, 09 Jun 2023 15:43:38 GMT

No the sheet metal rule i have is with no k factor and when i convert a standard part to sheet metal i select the ,,base face of the component. I made the experience that picking the concave face works well. Then Inventor picks up on the thickness what the part is drawn at (which could be realistically anything). After that is done i create the flat pattern and inventor tells me what the sheet extents are which i then import into my parameters for further operations. It works well with flat stack parts - and i think i had it once working that it wouldn't matter which face you would select it always gave me the correct size. I may do something wrong over here im still investigating ...

But yea K-Factor =1 is the way to go with it - ill draw an example for you so u can see what my work flow is. I use it mainly to grab X- Y Z of a panel regardless of how it is drawn

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Fri, 09 Jun 2023 15:53:16 GMT

Thank you so much for this info. My workflow is as follow: I draw millwork items in solid body style and then i wrote with the help of the forum some code to generate me the components from the ,,mastersolid,, into ,,panels. With the help of the appearance column i was able to apply multiple ,, panel codes,, as material to the solids as i can have this way my material applied at the solid stage (similar to solid works i belive). Once the components are created i run a script which grabs X Y Z of each panel and adds them into my parameters which drives now width , length , and thickness. The sheet metal template i use for curved / complex parts such as our example bu ,,converting that component into sheet metal then select the face of it and flatten it. Via an ilogic on safe it overwrites then the XYZ from the script.

I dont know how i can explain it differently but i may should upload a quick video file for this type of work flow. It still has a few bugs but it basically spits out the BOM for hundreds of components in a matter of minutes which we send then to a panel optimizer and then to a beam saw.

I use inventor for millwork items mainly and we dont use any bending factors...

Re: Flat Stack Sheet Metal Extent

phoenixwahoff — Fri, 09 Jun 2023 15:55:01 GMT

Hi Johnson,

Thanks for the clarification on the K-Factor. I wonder if i can come up with some ilogic to determine if i need K-Factor 0 or 1. Can i access the Kfactor via ilogic somehow?

Re: Flat Stack Sheet Metal Extent

Frederick_Law — Fri, 09 Jun 2023 16:10:31 GMT

k = 1 when thicken toward center.

k = 0 when thicken away from center.

To me it should be k = 0.5 thicken midplane.