Metal bending ..how best can this item be made?

Rhino Rhino for Windows
1

Hi,
V5

What I am after is being able to bend metal in rhino, as opposed to creating plans of how a bent metal item will look and getting the S bends to look correct.
I would like to see how that item (file was attached) for example could be created by just creating the sheet of
metal then putting in that 90 deg twist into it and the lightening holes and their radiused edge.

Skyg said… If you have a well lofted wing using the method I outlined above, turn on the control points for the surface, and delete all the control points (there will be two rows of them) between the root and tip. In fact this is a good idea for anything that is being modeled as sheet metal, since unless it’s a hydroformed part or such, it’s sheet metal and can only be bent in one direction. So you now have a surface that is degree 3 in the direction of the chord of the airfoil, and degree 1 in span. This is perfect - this actually models the way sheet metal is bent.

Skyg has a way here of making a surface that is as metal bends.

Anyone care to show how that edge could be twisted following where on the plan it occurs. The S bend there was purely suggestive on the original 70 yr old plan and only by bending a solid or surface will we see the true shape and length of bend, I am after the solid and not the plan. I dont want to find myself trying to create how it looks in ortho
so as to then use that to bend it, I havent a clue if the actual bend would be 3mm or 5mm or 7mm, not knowing how it would actually bend given the physics of metal. I saw the turbocad user do it in 10 secs.

any links to tutorials on metal bending in rhino welcome.

ItemForMetalTwists.3dm (73.4 KB)

Steve

2

Steve, a physical example of this part cannot be made entirely by simple bending of sheet stock. Some stretching/shrinking is required. The exact shape of the transition area would depend on the details of how the physical part is made; the operations used and the sequence of operations.

What is the purpose of your Rhino model of the part? If it will be used to make tooling for the part then you should consult directly with a metal forming expert. If it is for “packaging” or illustrative purposes then any reasonable shape should be sufficient.

3

Hi,
V5
I am creating these solids then assembling them in Rhino to build a 3D solid model of an aircraft showing the actual structures, folded lipped edges, lightening holes etc, I see such done in solidworks and the parts look like they should on the real thing. I also need to show others what it should look like without apologising for the fact that all metal radiused bends are missing.

To form all edges as sharp 90 deg bends, to ignore twists, it would look so primary schoolish, and make me look like I need to use a decent CAD prog !

yes when metal bashing is done some stretching of metal occurs, such parts are easily created in solidworks etc. To see the TurboCad chap when asked to twist a part do so in a few clicks without having to figure out how the twist would look, versus Rhino user create the S curves, do a sweep or two etc, 10 secs versus an hours work with conjecture mixed in and knowing how metal twists etc.

I bought Turbocad for the bending but it wont open Rhino with points as the points are microscopic and not visible.

Steve

4

As someone suggested elsewhere, leave the gap and rotation you want between your two surfaces and use the BlandSrf command. A couple of clicks and you have a result a lot better than with SolidWorks or TurboCAD.

5

not sure I see that ?

Anyone care to show me what rhino can make of this item using methods suggested ?

any articles or vids on this anywhere ?

I cant see myself doing it in a couple of clicks though. I attempted an S twist once and it took hours to work out where the twist went etc.

Are we saying position the metal before and after twist then let BlendSrf show me the path ?

I dont know the extent of the twist. Like if one takes a 5mm wide strip of metal and twists one half through 90 deg, what length is the twist ?

Steve

6

[quote=“Steve1, post:5, topic:17120”]…

I dont know the extent of the twist. Like if one takes a 5mm wide strip of metal and twists one half through 90 deg, what length is the twist ?

Steve
[/quote]

With a physical piece of metal that depends on how the metal is “twisted”.

8

I hope you’re not suggesting Rhino isn’t a decent CAD programme Steve, the tools are all there to create your part pretty quickly, maybe not 10 secs but 10 mins will do it… that’s to create the model not the twist… oh, and use blendSrf for the twisty bits.

ItemForMetalTwists(BM).3dm (1.2 MB)

9

No :slight_smile: I am saying that without the twists others might think I am using a more elementary free prog !

I wish I could see the making of that frame as a video, that would make my week if not month, maybe year in fact, as its puzzled me from day 1. I even bought Turbocad because of it.

To see that twist formed, using BlendSrf. I need to see the steps taken, how did you decide on the start and end of the twisted area ?

I have exploded your frame, and selected the edges either side of the twist, BlendSrf gives me similar but not same isocurves. Did you simply decide on where the twist would start and end then leave the open gap and BlendSrf between the two edges ?

Were radiused edges all round a sweep ?

10 mins…I would love to see that in real time vid …truly I would.

Steve

10

My guess is Brian used on or more of the Rhino filleting commands to create the radiused corners. These commands include Fillet, FilletEdge, FilletSrf and FilletCorners. Steve, if you are not familiar with and comfortable using these commands you should immediately spend time learning about them. They are fundamental in creating models such as this part.

It appears that Brian first created an outer surface as a polysurface (Single skin item layer) and then used OffsetSrf to create a solid based on the outer skin polysurface. Steve, if you are not familiar with and comfortable using OffsetSrf take some time to learn about it. It is a fundamental tool for creating solid models of objects made from sheet material.

11

Sounds like a challenge so this is for you Steve, it’s all a bit scrappy as I’m new to video screen recording but will give you the idea. There are some bits I’d take more care with if it wasn’t just a demo and I’ve used a wire which is out of alignment to generate the handle? part. The command line will tell you what’s going on… hope it’s useful to you. :confused:

12

Brian, quite interesting. Good to see how others create models.

13

Hi BrianM,
Brilliant MANY THANKS FOR THE VIDEO…to see a subject that means something to me made , makes the world of difference. . video is the way to understand…and to see your approach. I used projection but projected the teardrop shape onto a surface extruded from the bent two lines.

I would like to compare this to how solidworks and turbocad and autocad makes it.

Much use of pause to follow the commands being used, I see Techsmith in use , any reason you opted to nuke all but command box ? (and layer palette ) ? the only insight as you say into what is being used is the command window. Jing does entire screen but 5 mins, so I end up doing episodes ! Camtasia will do a crisp sharp entire screen capture. I would like to see McNeel adopt a quality screen capture. This is the first video I have ever seen of metal bending objects recreation.

I see you used fillet to get the radiused profile then sweep for the first radiused edge then much later when the base edges needed radiusing, fillet was used, chopping out the small portions and sweep those.

I also see that the start and finish of the twist used my start and finish of my S bend. What I am trying to figure out when using Rhino for such things is this…for this example I had traced over a plan, and that part of the plan with the twist was sketchy at best, it didnt look like that decent S curve but it looked definitely wrong, so where that twist started and finished was not indicated on the original paper plan, and I just plumped for an arbitrary location and made it look decent with a start and end tangent curve. In real life given the physics of the metal and the 90 deg twist at that angled area, how would I know where to start and end the twist ?

I can see that BlendSrf then helps create the twist, and later on offset makes the solid. I have found that for more complex projects which are a real patchwork quilt of surfaces, offset causes artefacts that I cant get at , and naked edges appear that I cant fix. Here though is a nice structure to Offset.

I would like to know why after the BlendSrf at 08:45 you used _pause then _isocurve then toggle and split the underside and deleted it out in the area of the BlendSrf section then swept it ?
Also splitting surfaces for the two small S bend transitions and joining the areas without the S bends transition. Would not filletSrf have tackled those areas as they were ?
Of course without a vocal to say why, I need to ask. Hearing why this or that is being done is good, but just so grateful for this silent movie, truly useful.

It is that Rhino is used to form the shapes that metal bending would make, then makes the solid, whilst Turbocad for example bends the solid.
Knowing where the twists start and end is the tricky bit.

Steve

14

Pausing to work out the next step I guess. I started recording with jing before realising the 5 min limit - that would be pushing it on this wee job. I used Camtasia instead and roughly edited out pauses and other bits and backtracks, (and trying to meet the 10mins :grin: ) - hence the scrappy finish.

The recorded area I used was around 2/3 of the viewport so I dragged the 2 dialogs into view and allow the command dialog to do the explaining.

The small portions were swept because ‘filletedge’ couldn’t handle the s-surfaces cleanly - the radius at the start of the S on the input curve is less than the 2.5mm desired radius (see image), so the base curve would need to be cleaned up for ‘Filletedge’ to work - so I decided to sweep2 for this exercise.

I think that the curves on your working plans would be an approximation and the fabricated item would be quite different in the twisted zone, maybe with buckling and stretching. If the finished shape in that area is not critical, an approximation on the model is probably acceptable. Otherwise a scan or accurate measure of the part followed by an as-built drawing would be required (or some very hard maths…)

The model did have naked edges after the offset, at the swept s-surfaces, which would have probably been avoided if the previously mentioned radii were attended to - so I used ‘ExtractSrf’ with Copy=No option to remove the bad surfaces and put new surfs in there with ‘sweep2’, first checking that the corners of the surfaces being used all met nicely. Good input can prevent frustrating mismatches later.

That step was uneccesary, however, there are times when it helps to have surfaces aligning cleanly with their neighbours and redrawing messy areas.

No mic - words can be a distraction sometimes (especially with an Edinburgh accent…)

When I mentioned before about the curve I should have aligned:

At around 4.20, the red j-curve should have been rotated to end up perpendicular to the sweep path. ‘sweep1’ is used instead of ‘ExtrudeCrv’ to result in a single surface for blending, otherwise a 3-surface polysurface would be created.

Hi @davidcockey I enjoy seeing what others are working on too, and always a few different ways to approach a model.

15

Hi BrianM,
Och, I am sure an Edinburgh accent would have been fine for my wee ears :smile:
Certainly compared to all those I get to hear and cringe sometimes at on YouTube.

I will when I get into my training (and now my laptop has gone sick on me having just had the new tower fixed after 10 days during which it saved my day)… follow this and make the part, and it will sink in even more that way .

Anyone know of any other ‘metal bending’ videos out there ?

Steve

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