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One thing I’m learning quickly about Sheet Metal product design is that coming up with a sheet metal part or assembly in SolidWorks (or even a hand-drawn pattern for that matter) is only the first part of the story.  The interesting part is now figuring out how it is going to be fabricated! This means that, besides a pattern, we also need to come up with a sequence of operations that takes into account the kind of tools or equipment we have at hand. Jeff Cox has some very interesting thoughts about it in his blog. Check it out! It’s really an eye opener for those of us that are just learning.

And now, let me tell you a bit about the sequence for fabricating that little tote tray I told you about in a previous post. Take into account that all that’s available is a small leaf press and some hand tools, like shears, hammers, a pop-rivet gun, etc. Not really a big shop… but still good enough to learn!

Anyway, once the stock has been cut out to size according to the pattern, the question that comes to mind is “What do we bend first?” I was under the impression that we simply had to do it in the same order as the flanges and hems were added to the part in SolidWorks, but it turned out to be quite the opposite.  In my SolidWorks model, for instance, the hems are the last thing to be added, but as it turns out, hems should be the first thing to do, since it would be very difficult to fold them after the sides of the tray are bent up. Also, we are supposed to look for ways to make several operations at the same time, rather than one by one, to make it more economical. There are also operations that won’t be possible with the kind of equipment at hand. I was told we can bend the sides using the leaf press, but not the ends of the tray; those will have to be bent by hand. We could bend them if we had a press brake, although I’m not exactly sure what the difference is, and why the press brake could do it while the leaf brake can’t.  I sure would love to see a press brake in action! This is a fascinating area that I wish I could learn more about!

Back to the example… It is possible to convey information about the sequence of operations to bend your part simply by creating a few configurations and suppressing a few bends.  Here is how. In the feature manager, locate the feature Flat Pattern. This is usually suppressed when the sheet metal part is folded.  Click on it to expand it and you’ll see a list of all the bends in the part.

Create a new configuration for the part and name it Flat, make this configuration active and unsuppress Flat Pattern. This will be our starting point.

Next, we need to create a new configuration and name it STEP1. We can simply make a copy of FLAT, since most of the model will be flattened, except for a few of the bends. In the Feature Manager, we expand Flat Pattern (which should be unsuppressed in this configuration) and look for the bends that correspond to the hems in the part to suppress them. This can be a little tricky when you have bends that have been mirrored.

Now we need a new configuration for the following step in the sequence, STEP2. The easiest way is to make a copy of STEP1, since we’ll just continue suppressing more of the bends in the list, in addition to those we already suppressed.  For STEP2, and according to the pattern I had originally, we should  find and suppress the bends for the sides and tabs, so they could be folded together in one operation. However, I wonder if the sides and tabs can really be folded in one operation, because the bend is not exactly located on the same line for both. See?

Assuming they could really be folded together, this is how STEP2 would look like after suppressing the bends.

The last step is to bend up the sides, which leads us back to the default configuration of this sheet metal part, which I’ve renamed FOLDED.

Like I said before,  I think Sheet Metal design is very interesting and I really want to learn, so I would appreciate if those out there reading this that may have more experience than I do  would take some time to explain how they would approach the sequence of steps for the tabs and sides… one step for both? Two steps? Which one would go first? Your advice and expertise is always welcome and greatly appreciated!

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