So, finally got time to open up the back of my Nomad while trying to address my fan noise issue (as detailed in the “my startup experience” thread). And while not hard, it’s a leeetle bit tricky, so I thought I’d chronicle the odyssey for posterity.
First: removing the back panel. The thing to watch out for here is that all the screws are holding the back pane on. My first assumption was that the fan sub-assembly was attached to the back panel, and so I left the four screws around the fan in place. Nope – gotta remove 'em all. Then the back panel comes loose easily, just watch that it doesn’t snag on the lower motor cable. These bolts take a 4mm Allen wrench.
Second: the “roof.” This is clever: the entire “Roof” panel simply slides in/out the back, once you remove the back pnael. It’s a bit of a tight fit, but it’ll come. Make sure to fold the front clear panel up over the top first, though. The square aluminum tube that the top edge of the back panel bolts to, turns out to be part of the roof assembly, so it slides out with the roof.
Third: the electronics cover (this is the part that the fan is mounted to). This one got me. It’s held in at the top by two socket-head cap screws (I used a 5mm Allen wrench), but they’re a little frustrating to get at unless you have a long wrench, or a ball-end wrench. My good wrenches are at work, so I had to spend some time working them out with my short little square-end wrench, turning ~60deg at a time.
What got me was the bottom three bolts, which took a 5mm Allen key on the front side, and a 8mm socket on the back. I took them out first, since they were the easiest. But when I finally got the top two Allen screws out, I discovered that the bottom rear edge of the electronics box is a hinge. I only need to remove the top two screws, and should never have removed the lower ones. In my defense, it’s not obvious. But if you need to access the electronics bay, you only need to remove those upper two screws , after which the top and back of the cover should simply fold down towards you with a modest tug.
Note: the hinge is just bent metal – flexing it too many times will probably cause it to fail, so be gentle. On a side note, the electronics cover is made from the same material as used in the Wrench Tutorial – looks like it was machined out down to one layer of aluminum at the bend points, and then bent to fit on a metal break. The “hinge” is simply that one layer of aluminum (maybe milled extra-thin).
Note: the top edge of the electronics box has a piece of black rubber edging fitted to it, holding it to the top edge of the X-axis rail. This is there to protect the spindle and Z-axis motor cables from the metal edges (which, while not sharp, are certainly not cable-friendly). You will need to remove this in order to open the electronics bay, and make certain to put it back.
Fourth: the fan. The fan is bolted to the back of the electronics cover from inside. I wasted some time trying to pry it out of the plate from the outside, thinking it was press-fit in or something. Nope. Once I got the electronics cover to swing open, the fan mounting became obvious.
Observations: everything is fitted snugly, but not jammed together. Once you figure out the screws, things should come apart with gentle persuasion, but neither fall apart nor require any brute force.
Wires are not routed with the obsessive neatness of German industrial machinery, but are generally neat and well-secured away from anything they might interfere with – the obvious exception being the wires around the E-stop, which were getting into my fan. Those wires really need an extra tiedown or something to ensure they can’t impinge on the fan blades. Wires that are exposed to potential abrasion or chips have been covered in protective jackets. The way the Y-axis motor and cable stick out through the back panel is a bit awkward, but that’s really a minor item.
Loctite is used in several places, which is probably a good idea for a high-vibration machine. I didn’t have any handy to re-goop my screws, but I’ll take my chances since none of the screws I removed was structural.
Opening up the machine did not result in any “gotchas,” things where removing the wrong screw would wreck the machining tolerances, or let loose a spring to fly across the room and vanish forever. Removing the panels does not appear to compromise the machine’s structural integrity in any way, unlike some machines where cost is reduced by using “unibody” type construction.
The X-axis limit switch is held to flat metal by just one screw, on one end, which seems a bit weak. But I’m guessing that it’s Loctite’d (I didn’t test that assumption). And maybe the ability to pivot on that screw is used to fine-tune the X-axis Home position, before the (assumed) Loctite is added to fix it in place?
All in all, a very solid piece of kit. While some cost-saving decisions are visible, they’re not in places that would compromise structural integrity or build quality. The hinge of the electronics cover is a good example: a weak point, but really, how often is that box ever going to be opened/closed? As long as you’re not flexing that hinge on a regular basis, it’ll easily last the lifetime of the machine.