topic Re: Multi-body sheet metal parts and sheet metal rule in Inventor Forum

Multi-body sheet metal parts and sheet metal rule

steven.coxVCM6J — Wed, 24 Sep 2025 15:50:49 GMT

Hi all,

We have found a significant problem with having multiple solid bodies using different sheet metal rules in a single part.

When we create a solid that uses a different sheet metal rule (thickness) it works fine. When we Make Components and create flat patterns, most of the time it works fine.

However, (seemingly) if we change the solid body that is not the default sheet metal rule, ALL of the sheet metal rules do not unfold properly.

I have included examples. The attached file Sheet Metal Rules.ipt is the original part. 12ga.ipt and 10ga.ipt are the components created from Sheet Metal Rules.ipt. I did not include the 10ga.ipt because of the limit on uploads.

Notice in the 12ga.ipt flat pattern the distance from the edge to the bend line is 1.003. This should be 1.000.

The Single 12ga.ipt is a single body part and it works fine.

To fix this, it seems we have to delete the sheet metal rule and import it again. If changes are made to the non-default body, it adversely affects all the other flat patterns.

Thís does not seem to be rule specific as it happens across multiple different rules.

Has anyone seen this before or have some insight.

Thanks, Steven

Re: Multi-body sheet metal parts and sheet metal rule

johnsonshiue — Wed, 24 Sep 2025 21:10:03 GMT

Hi Steven,

Many thanks for sharing the files! I took a quick look. I think the issue is that the Default K factor in 12ga.ipt and the one in Single 12ga.ipt are different, leading to different unfold length values. Please make sure the two K factors are the same.

Thanks again!

Re: Multi-body sheet metal parts and sheet metal rule

steven.coxVCM6J — Mon, 29 Sep 2025 12:10:55 GMT

Johnson,

Thanks for looking at this. I agree this is likely what is causing the different unfolds. However, both 12ga parts were created with the same sheet metal rule. Something caused the default K-Factor to change in the rule (thereby corrupting it).

Also note that the default k-factor for the 10ga part is .42. (see attached).

It appears that Inventor is changing the default K-Factor of the 12ga part to match the 10 ga. When we purge and import the sheet metal rule again, the problem is fixed (until we edit again.)

Are we doing something wrong, or is there a way for us to avoid this corruption?

Thanks, Steven

Re: Multi-body sheet metal parts and sheet metal rule

johnsonshiue — Mon, 29 Sep 2025 20:56:27 GMT

Hi Steven,

I am sorry I am not aware of a workflow leading to the corruption. If you know how to reproduce it, please let me know.

Many thanks!

Re: Multi-body sheet metal parts and sheet metal rule

steven.coxVCM6J — Mon, 29 Sep 2025 21:09:08 GMT

Johnson,

Create a part with a 12ga solid body with a flange. Create a second solid body with a flange using a sheet metal rule for different thickness....in our example we used the 10ga rule. Save the part.

Modify the second body, then look at the flat patterns. I cannot say this happens every time, but in the example it did.

I attached the two sheet metal rules in a zip. Note that this happens with other rules as well.

Thanks, Steven

Re: Multi-body sheet metal parts and sheet metal rule

johnsonshiue — Mon, 29 Sep 2025 23:58:19 GMT

Hi Steven,

Many thanks for sharing the rules! I imported them to a sheet metal part and tried the above workflow. I also tried importing them to a sheet metal template file. Neither allows me to reproduce the issue unfortunately

You mentioned that it happens from time to time. I guess when there is more than one Derive node, the "Follow default" checkbox will be unchecked. You will need to explicitly assign a Sheet Metal Style to the body. I believe this is the original issue that was discussed earlier.

Thanks again!

Re: Multi-body sheet metal parts and sheet metal rule

steven.coxVCM6J — Tue, 30 Sep 2025 16:24:14 GMT

Johnson,

We specify the sheet metal rule in the Face command dialog box. We choose to create a new solid there as well.

Based on your observation, I believe we can avoid this issue by creating KFactor for each sheet metal rule as an unfold rule then reference that KFactor in the Sheet metal rule. This way, we do not use the "Default" KFactor in the unfold rule. I will test this and see if it helps.

Thanks, Steven

Re: Multi-body sheet metal parts and sheet metal rule

kacper.suchomski — Thu, 02 Oct 2025 19:54:26 GMT

Are you sure you're using the same templates/rules?

A K-factor can be assigned to a given rul

Check that they are all the same.

Re: Multi-body sheet metal parts and sheet metal rule

steven.coxVCM6J — Thu, 02 Oct 2025 20:00:19 GMT

Yes Sir, we use the same rules per material thickness / type. It appears that when we edit the solid that is not the default SM Rule, it changes the Default KFactor in the unfold rule. Because all of the SM Rules use the Default KFactor, this causes issues.

To get around this, I created KFactor rules for each material thickness / type and assigned that in the SM rules.

So far so good in testing. I will undoubtably put it to the real test in the next week or so.

Thanks, Steven