Bending Modeled FFC Cable

[george]

I downloaded a vendor's STEP model of a LCD screen and I added a capacitive touch screen on top of it. I want to now bend the FFC cable portion of the model around to the back side (so the FFC cable is parallel to the back of the LCD).

I've been messing around with some of the operations and I can't seem to find a way to do this so I'm hoping that I'm just missing some function that will help me do this. Ideally the finished model will have a joint so I can insert this into a case design and fold the FFC cable so it ends up something like this:

But that just cut off the FFC cable and doesn't show a bend

[hamid.sh.]

@george I don't think you can bend the FFC in your file directly with a Fusion command, but can think of two options (I would personally use the first one):

1. Draw your own FFC, simply with a side sketch using spline to imitate the real bend, something like this:

Now I have done it with Offset inside sketch and Extrude, but it's even better with Surface Extrude and then Thicken. Also, if you want the lines and text cosmetically, you can apply a Decal:

2. Use Sheet Metal features, with modified rules (increase bend radius). Using this you can actually bend together with lines and text, using Unfold/Fold sequence, like this:

But as you see, this one results in circular bends which might not resemble the reality. There are tricks to make spline bends in Sheet Metal but doesn't worth in my opinion.

I have attached the file for the second method.

[george]

Hi Hamid,

Thank you very much for taking the time to show me some options. Since the FFC wasn't a simple rectangle I wasn't sure how to use the side view spline along with something to give me the actual shape of the FFC. I have components that I wanted to check for clearance so mimicking the actual shape would allow me to check that as well as determining where I needed to place the FFC connector on my board that this will plug into.

I was curious on the sheet metal design why you projected up to a different plane. Was that just to better show what you did?

[hamid.sh.]

Hi George,

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Since the FFC wasn't a simple rectangle I wasn't sure how to use the side view spline along with something to give me the actual shape of the FFC.

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Fair enough. On a second thought I think spline together with sheet metal is even better, so I am going to show you how. But before that, to answer your question:

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I was curious on the sheet metal design why you projected up to a different plane. Was that just to better show what you did?

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Yes, exactly. It was just for the sake of better visibility (it can be simply changed by setting Plane1 distance to -0.1 mm instead of 10 mm). Also because it's a component you can use joints to fix it on the connector and/or PCB. 

And now how to do it with spline bend and sheet metal features:

The key is to think of FFC initially as a simple rectangle; you can cut it out to shape afterwards. First draw the cross section spline. Here there is one important point: the length of spline must match the length of your FFC (using measure tool it's 30.91 mm). Fusion doesn't let you to put length constrain on your spline, but with a bit of moving control points you can get that length (approximately). When you select the spline alone, its length is displayed at the bottom corner:

You see I have matched the length with that of your FFC, and assuming it goes into horizontal connectors I've set its two ends to be horizontal. You might want to adjust the shape to your situation, just don't forget to match the length.

Next I Extrude this profile as Surface, then Thicken.

Surface Extrude, Thicken

Now in order to be able to convert it into Sheet Metal you need to Extrude to one end of it (you'll eliminate it later):

[dummy] Extrude of one end

Now you can convert it to Sheet Metal, apply Unfold, cut it into the final shape and add text and feature extrudes:

Unfold, Cut Extrude, Extrude texts

Once you've done adding features Fold it back, and finally remove those dummy extrudes with another Extrude:

Extrude (to eliminate dummy ends)

I have included only few surface features because they slow down the process and make the model heavy. If they are not needed totally avoid them and instead use a Decal (e.g. from screenshot of your FFC):

Decal

Hope it helps.

File and decal image is attached.

[george]

Hi Hamid,

Thanks again for all of the details, it is extremely helpful! I did some playing around today and found that I could convert the existing FFC into sheet metal directly. The issue I ran into was that the original model included all of those features are bodies and the sheet metal tools need your body to be the same thickness, or maybe it just needs to be the same thickness just where you want to bend?

Since that grey portion of the model (the capacitive touch screen) is separate I tried to get it bend the same but my model is a bit of a mess and I couldn't do it properly.

The only feature I'd like to keep are the 50 pads at the end of the FFC cable but they can be just part of the decal.

I'll work with your new model tomorrow and see if I can improve my skills!

Thanks again,

George

[hamid.sh.]

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The issue I ran into was that the original model included all of those features are bodies and the sheet metal tools need your body to be the same thickness, or maybe it just needs to be the same thickness just where you want to bend?

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That's true. This is why it's easier to make a new sheet metal from projection of your imported FFC, so you can control its thickness. Also keep in mind, even if it was possible to directly convert imported FFC into sheet metal you couldn't bend it into spline cross section. If you thick spline resembles your real FFC better you have to make the model (well, I almost did it, just change the spline to your liking).

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Since that grey portion of the model (the capacitive touch screen) is separate I tried to get it bend the same but my model is a bit of a mess and I couldn't do it properly.

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In the recent file I sent you I already separated FFC and display (because I wanted to hide display only). I used Split Body and Combine. You'll understand once you check my timeline.

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The only feature I'd like to keep are the 50 pads at the end of the FFC cable but they can be just part of the decal.

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 That's good idea. I included only one of the pads. You just edit "Text and features" sketch to project others and include them in extrude.

[george]

Well I'm beginning to feel like a failure as I've tried to modify the spline and it just doesn't seem to work for me. If I move the spline shape then the length changes and that breaks the sheet metal operation. I must be doing something wrong because it seems that I what I want to do shouldn't be that hard.

In the end I'd like to play with where and how the FFC cable bends. The reason is because the FFC cable has some components on it so you can't just bend it anywhere. Then the bend can be almost any distance away from the LCD frame and that impacts where the end of the FFC cable will be which is the critical part of wanting to do this. I'm trying to find the position of where the FFC connector on my board should be.

Would you mind trying to help me change the spline so it stays at the fixed length needed but allows me to them change the shape and position? Hopefully this is something easy that I haven't been able to figure out on my own.

[hamid.sh.]

Do not feel bad, this is not really something Fusion is made to do, so things can easily go wrong.

I don't mind at all and will be happy if I can help. But first I am going to list some points that might help you:

1. My wild guess is something went wrong with that extra (dummy?) extruded section. I should have emphasized that when you want to convert to sheet metal or use Unfold you select one the surfaces of this section.

2. You should never loose the dummy extrude section during Unfold/Refold sequence. For example it may happen you Unfold, then when trying to cut extrude the unwanted area, you remove that part as well. If this happens Fusion cannot fold it back. Your sheet metal body must have at least part of that flat surface for any Unfold/Refold sequence.

3. In fact length of spline is not that much critical for successful Unfold/Refold. It can be for example longer than your FFC, but after Unfold it becomes longer than your FFC, but then you can simply cut it to shape and size. Think about that spline as the cross-section of raw material for making real FFC; it can be totally different size, then you spread, cut and then fold it. I insisted on matching size so you'll be sure that final FFC will look like that.

4. Make sure all of the projected sketch (these purple lines) fit over the unfolded sheet.

5. Use of spline is not strictly necessary. I just thought it can match a bent FPCB well. Of course you can use straight lines for part of it, as you mentioned, for parts of FFC that won't bent because of soldered components.

I am looking forward to see your file with your spline, maybe I can find what went wrong.

[TrippyLighting]

First of all, in this particular case where you want to parametrically modify imported geometry, you should enable the timeline.

Then, to maintain proper assembly structure, both components should be inserted into a new design file. You should not have a bodies folder at the same structural level with components in the browser.

While the workflow is a little tricky, you can bend the existing FPCB. The model is attached for study. I'd be surprised if you would not have any questions:

 

[george]

First, thanks Hamid and Peter. 

Peter, Your initial operations are the offset face and untrim which I'm not clear what they're for. Perhaps splitting the FFC from the LCD body? (BTW, this was a downloaded STEP model from the manufacturer, not my original design). Is there a reason why you didn't just use that face as the splitting tool?

I saw that you then split off the extruded features on the FFC and collected the bodies in non-SM stuff component which was nice. Yesterday I was working on completely removing those and did something similar and then I created a sketch which had more accurate placement of the contacts in the 3 locations. I was trying to eliminate all the bodies and maybe just use faces and color them differently but I wasn't successful in doing that.

You both have used unfold, is that just so you have a step in your timeline to move the FFC back into the flat position or is it necessary for something? I see that you used it to combine back all the "non-SM" bodies. I hadn't thought of that and maybe that help ease the calculations that F360 has to do behind the scenes?

Hamid, I like the spline tool since I think it allows me to create the bend to better mimic reality but it seems like I'm fighting a loosing battle. I'll have to study you notes again and see if I can get it to work. At least I'm getting close to what I want to do:

[TrippyLighting]

Here is a screen recording that explains the process:

[george]

Wow, thanks so much for going through that and recording it with comments, that was extremely helpful! 

I'm not sure if you're familiar with these electrical components but in my screen shot I show some terminal blocks on the right hand side of my PCB. These are through hole components so that means that the pins go through the board and protrude through the bottom of my PCB. That means that this LCD cannot sandwich directly onto my PCB because it will short out the components.

That was what I was trying to model so that I could bring this LCD model into the enclosure design, along with my PCB, and then move the FFC of the PCB and determine the correct position on my PCB. Since this FFC is not a simple rectangle I also was going to use this model to determine clearances from the terminal blocks or other parts on my PCB.

Once I convert the FFC into a sheet metal body and import this model into my enclosure model will I be able to adjust the FFC shape as easily as you showed at the end of your video?

For instance, I know my PCB thickness is 1.6mm and I'm going to leave 3mm of clearance between the bottom of my PCB and the LCD for the (through hole parts). Based on this I know that the FFC will need to be 4.6mm (plus a little to make it into the FFC connector) away from the LCD. I've played with the bend line and have achieved that with a little experimenting but it would be nice to just bring this LCD model in and move the FFC so it clears what I need and then determine the final position of the end of the FFC cable.

Thanks also for the tip to change the K factor to 0!