What causes this weird problem in sheet metal bends?

[HDEAR]

Hi all,

I was screwing around with different bend designs for a project and happened upon this weird ( IMO ) effect.

Whilst the Mitred Corner feature in sheet metal is a very useful and clever tool, I find it a bit limiting because all the subsequent folds cannot be edited or changed and they must obey the master or else 

Often I use bend with no stock length, manually alter the reliefs to give me the desired effect plus a gnat's whisker gap to avoid clash and 'add stock', then edit the drawing to make 45 degree corners. The problem with that is if the sheet metal stock length changes, then my 45 degrees on the 'add stock' goes skewiff ( maybe I have to learn how to keep the 45 degree angle plus the parallel edge under control so it doesn't do that - another day ) so that makes me grumpy as well.

Anyhow, referring to the video, I made a normal bend on a piece of 1.5mm sheet, gave the corner reliefs 0.1mm rake to avoid clash, added a vertex chamfer and it looked great. If I changed the stock length, all was good. The I did the same in the 90 degree directional bend and the fun started. I pulled the bend away from the corner, added the relief and the vertex and when I pulled the bend back, as soon as the vertexes touched, they were at war with each other. If I have vertex fillets on add stock, the same phenomena occurs.

Is this normal behaviour? What's the cause of this?

I know there's probably better ways to do this sort of stuff, but I was curious as to why vertex fillets give each other grief.

My play file is also attached.

Harley

 

Vertex fillet play file.ics

Edited January 14, 2020 by HDEAR

[Jonas@Solidmakarna]

Hi Harley,

Have you tried the Miter Flange tool? Just select the Bend on one side, then select the edge to miter with.

The Miter Flange feature will still contain the first bend, which can be modified and the Miter updates. You can also choose to create the other Bend individually by selecting the "Create miter flanges only".

 

[SSIMMONS]

I would definitely use the Miter Flange with "create miter flange only" turned on. This tool is fantastic and will save you a ton of time. Any weird or odd reliefs that are required (for instance to avoid overlapping geometry) can be done manually by editing cross-sections, but i think the miter flange tool will take care of most of the situations that come up. 

- Spencer

[HDEAR]

Thanks Jonas and Spencer.

Yes, I do actually use the Mitre flange option at times, but I found that I couldn't do anything with the 'slave bends'. Your showing me the use the Miter Flange with "create miter flange only" turned on is something I completely overlooked, so thanks for that and the Mitre Flange feature is now more useful to me.

However, it doesn't completely solve my problem. 

If I have a box shape whereupon the long stock piece finally ends up being either pop-riveted or spot welded to itself, miter flange doesn't solve the problem, but it does help a wee bit.

Here's what I mean 

 

So how I get around it is shown in my video, still a little tedious as you can see. I have completed the box how I would present it to the sheet metal shop at the start of the video. Then I removed the flanges and showed you the process. I am sure  there's a simpler way though. I used 1.5mm stainless only because it's easy to make the relief calculations for the purpose of this exercise. 

I have also attached the ics file so you can have a play

Cheers, and once again thanks for taking the time to help

Harley

Folded box play file.ics