I first thought of buying a pre-made 19-inch rack mount case, 3U high, 19 inches deep, but those were unavailable locally, and shipping such a large item would cost a fortune. Even if one was available, I’d still have to cut out holes for screws and air vents, which would take too much time.
Instead, pwf suggested I order a custom-made one, cut out with a water jet and folded at a shop that specialises in doing just that.
The shop needed an AutoCAD .dawg file for their machines. I don’t have AutoCAD, so used FreeCAD instead. It went better than last time, especially since this time I used its sketch feature and constraints a-la SolidWorks.
But it doesn’t export directly to .dwg, only .dxf. Draftsight can handle both, though, so I exported to .dxf in FreeCAD, imported that in Draftsight, moved things around to coloured layers, exported to .dwg and sent the file to the shop. A little convoluted, sure. The files are available here.
The shop didn’t quite do it by-the drawing, since I didn’t include a 3D view of what I was expecting. (DraftSight is essentially AutoCAD for 2D, at least the free version.) Also, I made some poor design choices in my drawing, so there was more work to do on the case than initially anticipated.
First, I didn’t specify the bending radii, and didn’t account for the thickness (1 mm) of the sheet metal in the cutout. Then, I went for the bottom-and-four-sides being one piece, instead of bottom-and-two-sides, so the shop couldn’t fold the box perfectly. I had to align it up before welding two adjacent sides.
Also note that had I gone the bottom-and-two-sides + top-and-two-sides route, no welding would have been necessary. Maybe I’ll fix that in some future revision of the drawing, if I ever need a 19” rack again.
Sheet metal doesn’t dissipate heat so well. To prevent warpage, I clamped in a brass “heatsink” on the backside:
Clamps are good arm rests, too:
I also didn’t include two mounting brackets for the DIN rail holding the circuit breakers, so had to hammer those out and plug-weld them from the front side of the case:
Then, I forgot to include screw holes for the top, so had to drill and tap those. Here’s how it looks:
Bent a few pieces of 6 mm rod, tapped their ends, cut out a front plate from 2 mm sheet metal, drilled two pairs of holes on either side and welded the rods in as handles. Also drilled two pairs of holes for the rack mounting screws, and cut out rectangular pieces for the front panel stuff:
Cleaned the case, covered in primer, painted black. Got no photos of that.
Mounted the electonics inside. The bottom looks screwed:
Those rectangular holes are for air flow, they’re right beneath the triacs’ heatsinks.
The wires were a mess, tidied them up with zip-ties, attached to these neat little adhesive zip-tie holders:
The original Sherlock Holmes Pipe is included for size comparison.
That’s almost it! Once I get to run a final power test, with the top lid screwed in place, I’ll do a final rant, promise to update the schematics, PCB layout and case drawing, conveniently forget all of that, and move on to other extremely time-consuming stuff.