Bend back fails between 20.47" & 20.48"

[Dale_Rosema]

I have a sheet metal bin that was initially 26.69" from side to side. I want to reduce that by 7". At 19.90", Bend_Back_1 fails. I found that @ 20.48" and larger the bend back works and @ 20.47" and smaller the bend back fails.

I cannot find a reason why things are failing when they do. Please find the attached file in a .zip file.

[StephenW]

I took out the bend relief holes and it seems to work???

[Dale_Rosema]

Specifically Hole #3 & Hole #4. Why?

If I change Hole #3 from .400 to .500 it works and so does hole #4 and the bend back?

0.407 works (but not .406)

[Patriot_1776]

'Sup Dale!

I haven't looked at the file, but it sounds like an accuracy issue maybe?  I don't play much with sheetmetal, but it might be something to look into.

Best of luck!

[sacquarone · Accepted solution]

Hello @Dale_Rosema 

Most of the time, as @Patriot_1776 said, it's enough to modify acuracy in this kind of situations. In this specific one however, i't'e not enough (even with accuracy_lower_bound 1e-5). Better than a long explanations, I registered a little movie showing that:

1. Issue is reproduced as per your guidance
2. A kind of "partial workaround" could be the redefinition of the Bend Back Feature and select the bends in the "good order" (instead of using the automatic way)
3. Above "partial workaround" is nevertheless not enough (because issue then occurs on the successive Unbend feature, and produces a kind of note very far from model, causing "extent  issue" leading in graphical issues on screen)
4. Root cause is pointing to the 2 lateral Flange Wall features 4 and 5
5. Using Flat Walls instead seems to setup a stable situation in this context

Consider this just as a guidance with a willingness to help you getting rid from the current issue, but for sure not as a "resolution". In my opinion, I do not see any valid reason to justify why it's not stable in original conditions (with the Flange Walls 4 & 5), so that:

• If it's an isolated use case, and what I propose here is enough to consider this as a resolution, I think we can just stop investigations here
• Otherwise, if use case is more global, or if you have any concern (even with my approach, or with the fact it just should work in original conditions), I suggest you to open a case to PTC Technical Support for probable SPR creation purpose

I attached also in this post the result (bin_ts.prt) of what I did in the movie fo your reference. Just be careful with this model, as I did the dimensionning very quickly, so that you may need to modify slightly some positionning dimensions of the holes (supposed to be the corner reliefs).

Regards,

Serge

[Dale_Rosema]

Since I found a work around with the hole size and since this is critical, I am calling your response the answer, but just living with a slightly larger drain hole.

[Dale_Rosema]

Hey.

Since this isn't rocket science and just a drain hole on a fixture bin, I can live with it at a slightly larger drain hole. So I am not going to pursue it further. Just another quirkiness of Creo popping it head up every now and then.

Thanks,

Dale

[Patriot_1776]

Creo quirkiness???  Say it ain't so!  LOL  🙂

[kdirth]

I think part of the issue is how you are using the program.  Specifically  Flange 4 and Flange 5 have a 0 inside radius.  A better way to achieve the box would be to create the bottom, create a flange around bottom (Shift selecting all fore sides) defining the corner relief, extend the back, flange the top and sides, and extend the top.  Attached is a quick example in 7.0.

[Dale_Rosema]

I have to take a look at this later since we are on Creo 4.0.

Thanks.

[Dale_Rosema]

I created a new bin.

I used the shift key to do all four sides.

I extended the back.

I create the top three flanges and extended the top.

Bin will not "Bend Back" no matter what I tried.... that is because I was suppose "Unbend", which once I did, worked fine.   🙂

A lot simpler model tree thanks to the shift key and selecting the (4) side and then learn to extend one of those side.