Opening the case

Software
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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. :smiley:

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.

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On the subject of re-assembly:

I had a strange issue getting the roof panel back in. The rubber edging on the left and right sides of the roof panel slide into slots machined into the right and left sidewalls of the Nomad. I didn’t have any trouble getting it out, it took me half an hour of struggling to get it back in. I just couldn’t get the slot on one side to accept the rubber edging – partway in, the slot just grabbed the rubber so hard that it starting stripping it off of the roof panel. Eventually, I resorted to smearing a small amount of lubricant into the slot, and that made it slip enough that I just barely got it in. Still strange considering how easily it came out…

Also, when you’re putting the roof panel in, do not slide it all the way to the front of the slots. The slots are cut a bit longer than necessary. What you want is for the back of the square aluminum tube that’s mounted to the beck of the roof panel to be “level” with the fan mount. The back panel bolts into the fan mount and this tube, so you need them to be in the same plane. So be careful when you get to the last inch or so of the slots when re-installing the roof panel – I overshot badly and had to wriggle the roof back carefully, which was not easy thanks to the aforementioned issue.

I should mention: the screws going into the fan mounting block are metal screws threaded into plastic – a reasonable choice for something that’s not intended to be opened often (if ever), but you’l want to avoid putting too much torque on them, or else you could strip the plastic. Just a little past finger-tight, I’d say. The other back-panel screws are threaded into aluminum, and so can take more torque, but you don’t won’t to apply so much torque that the head of the screw starts burrowing into the plastic of the back panel. I would torque them a little tighter than the fan-mount screws, but not much. A bit of light-duty Loctite would probably be a good idea, but I wouldn’t use the heavy stuff.

The Nomad plainly isn’t intended for a lot of user servicibility, but compared to, say, an iPhone, it’s a wonder of accessibility. Basic service tasks like swapping out the fan, or replacing a fried circuit board, should be well within the reach of your most users.

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Thanks for posting this to help others, and sorry for the fan problem. That whole area of the machine is getting a lot of attention right now since it requires way too much time to assemble and the only support problems we’ve had have come from there.

My only warning to others is that once you open the electronics enclosure there are 110V wires that can hurt you if you’re not careful. Don’t dig that deep into the machine with it plugged in and don’t do it at all if you’re not comfortable around AC wiring.

Regarding the bends in the aluminum composite panel, the bend points are machined to specs given by the material manufacturer so it will survive a few bends but it’s not meant to be a hinge, it’s meant to be bent a single time and then left alone. There is a debate within Carbide right now about changing that to a sheet metal part but it’s not clear that would be objectively better.

We are changing the PCB layouts to reduce wiring, eliminate one board, and use the frame itself as a heat sink with the hopes of eliminating the fan completely. As it is now, the fan should not be necessary but we didn’t want to take chances with lost steps on a thermal overload.

Regarding the switch mounting, that is the Omron-recommended way of mounting it. There is a 3mm post on the switch going into the aluminum in addition the to 3mm screw. The screw holds the switch down (locked with Loctite), and the post and screw prevent shifting and rotation. One other thing to note is that the frame prevents the switch from ever bottoming out and acting as a mechanical stop for the Z assembly. That means the switch never be subjected to more that a few grams of force (from it’s built-in spring). These are actually fairly expensive switches compared to generic microswitches but they were the only thing that met out requirements and came with a datasheet that guaranteed all of the parameters that we needed.

Rob

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(They do say, the fastest way to get a correct answer on the internet is to post a wrong one :stuck_out_tongue_winking_eye: )

Electrical safety: Yep, should have mentioned that.

Okay, so, less of a hinge than I thought.

The homing switch: ah, hah! I wondered if it had a hidden dowel pin of some sort, but I wasn’t about to take it apart to find out.

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Don’t take the limit switches out- the positions are calibrated before we ship them. (not sure how much they’d shift but it’s not worth finding out)

-Rob

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Just wanted to thank you for this post, it is invaluable to anyone opening the case and electronics enclosure.
I did end up using the bend like a hinge, if you are careful it should not deform much more than it would just being taken out.

I did a spindle motor swap which is also fairly straightforward (assuming it doesn’t all come apart in a few days). The only procedural trick that might not be obvious is that the spindle motor pulley needs to be put in place as the motor is lowered into position, so don’t screw the motor mount screws in until you have the pulley at least located on the axle.