Mellanox ConnectX-3 3D printed brackets (WHL #42F1)

Looks like I got a project out of the 10GbE card thing

I have to admit that I was wrong in that post – the 3D model of the bracket over at servethehome doesn’t entirely fit the ConnectX-3 MCX311A. It’s for the higher-end dual cards (that I knew) with QSFPs (that I didn’t check). These are larger in physical footprint, so the bracket does fit by chance, but there’s empty space towards the PCIe connector. Also, because of the dual port architecture, these have their second mounting point shifted up higher, which means the second mount doesn’t even meet the PCB.

Don’t get me wrong, if I was able to get two metal brackets of that type at a reasonable price I would happily ignore the shortcomings, install it and forget about it. But…there are none.

Funny thing is that Mellanox IS selling brackets at very competitive prices. MCX311A full-size brackets are $2 each. Great…unless you need them shipped. They charge for example $40 for shipping to Germany. Thanks, but no thanks. The two cards itself were 45 USD at the time… :roll:

Going forward, I still had a try with the model from servethehome to get a feeling for the challenges of 3D printing. I do not own such a printer, but a work colleague recently purchased a cheap 200€ unit. He was happy to help me out and so I modelled something based on the experience of the first print. Luckily Mellanox offers 3D models of most cards on their website, so I didn’t need to start from scratch or modify the existing one.

As a 3D noob, I had to convert quite a bit because I don’t have any workflow ready to handle these files. Mellanox offers STP files. Well, 3DTransform will convert such files to STL if they do not exceed a certain size. The Mellanox ones do, but only ever so slightly, so they got accepted. They will mail you a link to the converted file.

STL is fine and dandy, but I couldn’t get FreeCAD to work with it. It’s loading correctly, but I cannot modify individual components. FreeCAD does nice color coding of smaller parts, but I couldn’t separate them. Maybe that’s some conversion issue, too inexperienced to judge that. So…FreeCAD can export to DAE. And Sketchup (unfortunately Windows / Mac only) is able to import that. Aaand I already did lasercutting models with Sketchup, which worked fine. And indeed, the DAE does work well with Sketchup. It’s a huge CPU load at first, but when you cut away the majority of the board, it’s getting much easier ;)

From the first print I knew that material thickness was an issue. So wherever possible, I upped the default 1.0mm (which does work well with metal) to 2.5mm, like the servethehome example. Some careful carving later, I had a Sketchup file that I needed to get back to STL to print. So the first step, export to DAE, was pretty obvious, and can be done with Sketchup. DAE to STL was done via Meshconvert. DAE/STL files are tiny in comparison to the original files, so the 15MB size limit is no problem at all.

via ViewSTL: (excellent for a quick check of your file!)

Hand it over to your printing hobbyist and let’s go:

Original low profile, servethehome (without the second port) and my bracket if you didn’t realize it ;) I had to play with color levels a bit in here because the black PLA appears black in the photos as well. Damn you, physics…

So…needless to say, it’s not perfect yet.

First of all, printing quality isn’t top notch, which is to be expected from a cheap printer that just arrived and is operated by a novice. That’ll pass for him (until printer limitations are reached) and YMMV for obvious reasons.

Second, the part of the bracket that passes the main board is too thick. I spared the lowest part that is clearly below the board and inside the case, but I didn’t check how much of the angled part needs to pass the board as well. Turns out: All of it. And some more of the straight part. Basically until the notch, which I (for some reasons) still have in the design. So the final print will have material removed at that part of the bracket down to 1.0mm. This might not actually be necessary for your board/case combination, but for mine (Asus M5A97 LE 2.0 + Chenbro RM41300) it is. Also, I found it interesting how there’s a separation of layers when filing it down. Don’t think that is how the print should look like, but again, this is a new printer in the hands of someone who hadn’t operated one before. I certainly wouldn’t do any better.

Card mounting flaps are also a slight issue. My 2.4mm holes (for M3 screws) were not honoured and instead the pads are solid. Which isn’t exactly an issue, get a drill and just add them. Getting the drill ready takes way more time than the actual process of removing tiny amounts of PLA. Stability is sufficient for handling, but you wouldn’t want to assemble and disassemble more than five times. I set my soldering iron to 270°C and melted a bit, which should do the job with the more fragile one. They’ll be a bit thicker in the final revision to mitigate the problem.

Other than that, the bracket does fit nicely. The thickened part above the PCB was set perfectly and has a snug fit. The LED cutout (from Mellanox) works well, even at the thickened edge. SFP cutout is perfect. The thicker top mounting flap for the case also works, but might require longer screws than usual. Not a problem for anybody that has come to the point of 3D printing mounting brackets for 10GbE cards :mrgreen:

DAE, STL and SKP files are attached – the final revision will get an updated version:
bracket5

That’s it for today, enjoy the sweat dripping down your butt crack until the summer lasts. I certainly would prefer being in e.g. Dublin right now… :evil:


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