Very large bend radius in sheet metal

bill_daniels

I'm having a hard time imagining how to do this in the sheet metal feature:
https://cad.onshape.com/documents/c906a6bdcf50136ee9dbb9e1/w/9f6d794f5ac613eb6ba6aa67/e/46b04f2749c981d246970793

The part is to be made of several sheets of 1/8" steel welded together.  I can easily see how to model the flanges but the large 9" bend radius is not clear.  There will be alignment tabs on the sheet parts to make the welding more accurate.

konstantin_shiriazdanov

for now only possible approximate solution
https://cad.onshape.com/documents/c9557f3e5ba998390a3ba684/w/9fda3d90ee14408120113961/e/201ae0ce628c588ca2aa9eb0

bryan_lagrange

Hey Bill

To create this part we create it two ways in the shop.

1) bend the 90 degree tabs then make slight bends at the tangent of the large radius. The slight bends indicate a start and stop point when we bring the part to the slip roller to roll it.

2) we use what is called a bump bend method which is to make incremental hits until the large radius is achieved.

If you want to gage bendline dimensionally and the angle to hit I have use the method of creating a polygon with large amounts of sides. The more sides you have in the polygon the smoother the radius will be. 

Here is an example I quickly did.

https://cad.onshape.com/documents/6d8dd61c55bb52c67c801026/w/70d3460e1114046d5a0674ca/e/4572cd1dd62c7697d7c36d82

Hope this helps

bryan_lagrange

@bill_daniels  Check out part studio 2. I did a tighter ploygon to smooth it out. If you had the time you could smooth it out even more but making more sides to the polygon. 50 is the limit I see for the polygon tool in Onshape so you have to go manual to go further than 50. 

https://cad.onshape.com/documents/6d8dd61c55bb52c67c801026/w/70d3460e1114046d5a0674ca/e/37ae4a93e995b4501d125517

konstantin_shiriazdanov

for now only possible approximate solution
https://cad.onshape.com/documents/c9557f3e5ba998390a3ba684/w/9fda3d90ee14408120113961/e/201ae0ce628c588ca2aa9eb0

bill_daniels

OK, I guess this is a future "Roll machine operation" on sheet metal in addition to bends.

bryan_lagrange

Hey Bill

To create this part we create it two ways in the shop.

1) bend the 90 degree tabs then make slight bends at the tangent of the large radius. The slight bends indicate a start and stop point when we bring the part to the slip roller to roll it.

2) we use what is called a bump bend method which is to make incremental hits until the large radius is achieved.

If you want to gage bendline dimensionally and the angle to hit I have use the method of creating a polygon with large amounts of sides. The more sides you have in the polygon the smoother the radius will be. 

Here is an example I quickly did.

https://cad.onshape.com/documents/6d8dd61c55bb52c67c801026/w/70d3460e1114046d5a0674ca/e/4572cd1dd62c7697d7c36d82

Hope this helps

bill_daniels

Bryan, I was confident an excellent sheet metal guy like yourself could manufacture the part.  I was just hoping to model it in OnShape's sheet metal feature.  I think bending it many-facet polygon would work if the facets were small enough but I'd rather have a smooth bend.  It's going to have a tight tolerance.  It is an 804mm ID enclosure for an 800mm diameter winch drum which leaves just 2mm of radial clearance.  This necessary because the line on the drum can be as small as 3mm and I don't want it to be able to escape.

bryan_lagrange

@bill_daniels  Check out part studio 2. I did a tighter ploygon to smooth it out. If you had the time you could smooth it out even more but making more sides to the polygon. 50 is the limit I see for the polygon tool in Onshape so you have to go manual to go further than 50. 

https://cad.onshape.com/documents/6d8dd61c55bb52c67c801026/w/70d3460e1114046d5a0674ca/e/37ae4a93e995b4501d125517

david_cook325

Please tell us that onshape is going to be able to extrude rolled parts with large radius in the future and be able to accept the existing radius in the sketch or existing part.  I need to make simple parts like this in in most of my projects and currently in  Solidworks it is easy.  These workarounds are OK for the next few weeks, but not for long.  Get the rolled cylindrical parts soon and we'll want cones not long after.

At the moment going from rolling the part or bump forming the curves is something the shop I send these to has a conversation with me on a case by case basis.  Allowing us to model the rolled parts with bump forming would allow us to simulate the bump forming and pass that on to the shop as an option with us deciding ahead of time what bump steps sizes are acceptable to us.