Fusion 360 Help Solid Model Combine Woes

I’ve got a 3D model I’d like to “engrave” into some aluminum to use as a heatsink. It’s a PCB that I have some thermal pads for, and I’d like to essentially make a clam-shell case for it, and then mill fins into the aluminum and maybe add a fan to keep the PCB cool.

I found that the manufacturer of the PCB has exported it as a step file (found here )

I imported that into fusion, deleted a couple RF cans that they removed (assuming FCC didn’t require them) and ended up with a combined model that looks like this:

So far so good. I saved that, and then created a new design, extruded an Aluminum billet, imported the combined model, lined up the origins, and then combined using the “cut” option which should “emboss” my model into the Aluminum, making a mold of my part (that I can line with the heatsinking and electrically isolating thermal pad).

Now I’d love to start worrying about toolpaths etc, but the issue is this (model hidden):

Notice the connectors, it looks like my model has some internal voids, and those, of course, aren’t being subtracted from the mold. Also, look for the large box that you see in the first photo, it exists, it’s just underneath the void which is now Aluminum in mold.

Any idea on how to tell fusion that I’d like my model to be my model but without any overhangs or internal voids? Or tell the cut command that I’d like an emboss instead of a subtraction? If I have to, I can remodel this manually instead of using the Altium export, but it won’t be nearly as accurate as the PCB model, and will be quite tedious getting the tiny components into the right locations.

I’ve tried Boundary Fill, and it doesn’t appear to be doing what I want. Same with liquid fill.

@nicksilva Feel free to laugh, I realize I’m in the weeds of 3D engraving/mold making, but eh, if you don’t start off on a hard project you’ll never learn.

Here are a couple zips of the files I’m messing with if anyone wants to help me out.
LimeSDR_Mini_1v2_Rounded_real v1.zip (742 KB) LimeSDR_Mini_1v2_Rounded_model v6.zip (3.7 MB)

If you want to help me with it in person, I’ll be up at DMS Saturday the 31st (August 2019) around noon messing with it, and if time permits, maybe cutting air on the HAAS.

How about creating an offset plane, create a rectangle on it and extrude the rectangle to the model surface.

At a high level, you should be able to export your pcb as an stl or clone it into a mesh… it’s always good to have a backup if the change is not desirable…
You basically want to take that step file and make the part a whole, solid object without voids… then that stl/mesh should work as a ‘cutout’ tool.
I’ll be at the space today(Friday) through most of the afternoon cutting parts on the haas, if you happen to stop by I could give some help. Otherwise if I decide to drive down on Saturday we can meet and work on it.

Instead of trying to mate everything when you remodel, you could just make general pockets for the small features? Should speed the redraw process up significantly if it will still function as a heat sink with minimal gaps around the smaller features. As long as their board is to the model, mating around those larger features should give a good fit. I don’t know fusion well enough to help you with the CAD but why not use 2017 Solidworks to design the mold and then import into fusion to tool path?

You mean for every large component on the PCB? They are all different sizes (X,Y, and Z), and their locations are not trivial (ie, if I mess up the location it won’t pop into the heatsink). If that’s what you mean, then that should work, it will just be a ton of time doing it for every feature on the PCB, which I’d like to avoid. That’s the backup plan at least.

Yeah, that’s what I was going to try next as the tools to get it to a mesh should kill the internal voids, and the tool to get it back should assume it’s a solid. I hate to lose the resolution, and it seems hacky, but if it works I won’t complain too much. It does still leave me with the problem of the connectors (both the SMA and the USB) as they will have overhangs, but I can work around two defects in the mold by cutting some larger pockets for them anyway.

If you happen to have a video on that, that’s exactly what I want done, but it’s easier said than explained to the CAD software as the old saying goes :slight_smile:

Just let me know, I won’t be up there Friday, as I have work.

If I have to remodel, that’s what I’ll be doing. I know which parts need the most heatsinking, I’ll make sure those are tight, and the rest I’ll just leave general cutouts.

I’ll be honest though it seems like with all of the tools that exists, I should be able to “press” a model into a solid instead of just subtract or whatever. I realize I’m using the budget CAD stuff here, but it seems like a normal workflow.

Looks like F360 to STL, import into F360, then convert from mesh to brep wasn’t a success. It’s still smart enough to float the parts off the PCB:


Amazon sells the Fusion 360 Basics Tutorial book for only $16.60. Search for ISBN 9781725611337. There are 152 pages of great examples.

Stop by the Expansion Group Conference Room, off the Common Room, if you wish to look at it first.

You could try export to STL with lower resolution or use the push/pull tool to ‘fill in’ the voids one at a time… if I have time tonight I’ll download your files and have a crack at it.

My 2 cents–it’s going to be far easier to get what you want manually, perhaps with paste for the large components and then foam for the smaller components. Working back from this inverse form is going to be much more work. On top of that, the sort of pocket, 5 sided contact it seems like you’re going for is going to be a negligible increase in thermal performance which also isn’t realistic to achieve.

What are your requirements here? Understanding that is going to help us help you most. My feeling is that what you are going for is far too complex for the goal.

I tried that, didn’t seem like it was the right path, I still ended up with voids up until the model had lost so much detail that I didn’t feel like the part would still fit.

Feel free, I’d appreciate it.

Have some fun trying to find the limits of Fusion 360, and figure out enough of it I feel comfortable doing the CAD portion of teaching the HAAS class. I milled this thing out on the bridgeport the old school way as a proof of concept and the main pain points I had there was it took forever to get all of the pockets in the right place and the right depth to still mate, used a lot of blue fluid, and the final part fitment was “OK” if I put enough clamping force with some screws on it. All in all, it was just OK, so I figured kill two birds, play with CAD, learn, and maybe improve on my homemade design.

So, This is kind of what you’re looking for?
You did say clamshell, so I assume you’d want a bottom half, and you want to mill cooling channels/fins, but this is essentially what you’d be looking to mill out from billet? base heatsink v3.zip (3.8 MB)

I hope that file is openable and all has all the dependancies/sub-components etc.

Whoops, just realized I missed one of the ‘pockets’ for the smaller chip. I’ll be around the space at noonish so just lmk where you set up.

Looking like 1ish for me, I’ll either be at the Bridgeport, the HAAS, or the welding bay, depending on what’s in use. Wearing a grey t-shirt and jeans.

I’ll be there1:30ish

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