5.25 ODD UpCycling

[ElMech_Proto]

5.25 ODD UpCycling

Making an aesthetically acceptable enclosure for our current hobby project without a basic machine room of Blondihack, or the dexterity of Clickspring, or that vast expertise of Joe Pie , it has proven a hard nut to crack. It is kinda impossible unless we start with something almost good. Especially if we want it in the foreseeable future with no infinite checkbook. I think the proposal next will fulfill at least some of the criterias above. I am not claiming, this is an outright livingroom-worthy design, but at least points toward that direction.
My weapon of choice is the good ole 5-1/4in ODD whose natural habitat nowadays is in every attics in the First World.


Fig.1

It has been made out of sheet metal, what is thick enough to be self-supported, but thin enough to be easily tailored by handtools. Its original zink plated finish helps to prevent corrosion before we give it a nice topcoat. To fulfill our demands as a suitable enclosure, we expect considerable amount of uninterrupted space inside as well.
Anything that comes free usually have downsides too. In our case it is the deepdrawn features facing inward, the variable bending strategy at the front and rear and its non-uniform overall length.
On the positive side: the front and rear X-Y dimension is restricted by standards, plus its 2x 4pcs mounting holes are also. Access to a harbour-freight mini-lathe is advisable, though it is not mandatory. Alternatively to my proposal,  you can tie the PCB-frontplate to the side of the Top Shell of the ODD with brackets. You may consider a monocoque building style, using the bottom tray as a mounting plattform for your electronics (instead of my convoluted inner chassis) if you do not mind those pesky fasteners on the bottom. Just out of curiosity I have tried the more complex way in order to see what we are up against, but feel free to muntz out what you consider as a show stopper and not a building block.


Fig.2


Fig.3

Ball-park dimensions of available inner room:


Fig.4

Do not underestimate engineering time:
This contraption does not represent an actual assembly, my intention was only to show you, how quickly we can run out of space with just one wrong move, such as placing a 40mm fan in the most convenient way, or using connectors on both side of the wire harness, or using PCB-size what cannot play well with other elements. Actually it occurs frequently, as we try to overcrowd our enclosures. Just throwing a small SBC with some periphery under it, and an additional PSU are plenty enough for this ODD shell.
The space what connectors may consume at the frontplate:


Fig.5

…and at the backplate also:


Fig.6

That caveat is also true for front and backplate design. In general we should leave enough space to every participants. Cramming them may lead us into an endless source of frustration, unless we put a vast amount of effort ensuring all will fit to each other in every aspect. Though that is not a hobby project for half a dozen unit anymore, but rather hardcore product engineering with all its investments.


Fig.7

At the 2ch Fan-Controler, I used the tactiles as they are without additional  buttons (ie protruding via PCB Front Panel),  while the PC/OnTimer got extra PMMA buttons,  whereon the PC-ON/HDD and TimerStatus LEDs can shine through well.
The front and backplate is 62mil thick 2ly FR4 copper clad. I learned that placing components directly on its bottom layer is not the best idea (one exception is reverse mount LEDs); a decent circuitry cannot be achieved without many GND-VIAs and their random pattern would be visible on the front (aka Top Layer) as well. Those elements serve only as mechanical mounting plates with the necessary graphical elements on silkscreen layer, and to hide the mess behind them.
LEDs can shine through only if we do not forget to remove the copper on both side. Plus, many solder resist can block the light completely (do not ask how I know that). Black, red, blue, white solder masks are usually totally opaque; green and olive (and violet?) are semi-transparent, therefore it can place an extra shade on the meagre colour palette as they appears differently whether dielectric or copper are behind them. The glass-fiber/epoxi core disperses the light source pretty evenly, but on the same token, it can easily bleed into any nearby aperture as well. To avoid this on a close-knit bargraph-like pattern, PTH is a suggested solution with glued-in light-pipes. The plated barrel and an additional layer of mask between the LEDs will block the ’fringe-light’ efficiently.
Bending sheet-metal without press brake or of that characteristic hammer indents:


Fig.8

If you ease the metal out with a nice hole pattern, even by hand it can be bent.
I have started with 1.5mm thick anodized ALU sheet, since it is stiffer than bog standard AlMgSi.
I think they call the first one AlMg3 E6EV1 and sold in Europe widely. To make it bent where we want, a pattern of holes should be drilled as a relieve what will divert/direct the bending force into a specific area. On this test vehicle the anodization was sanded-off and the bending was a bit off-the-center-line in the machine-vice, hence the strange look.
 Be aware, when the web is less than 1.25mm, the feeling of that bending is like  Al99.5 (~EN AW1050A). Though 2mm web is plenty enough to keep up its structural rigidity. Its sweetspot is somewhere around 1.5mm. Hole diameter should be 3mm. Under 2.5mm the bending radius could be uncontrollably high.
(A nice semi-gloss topcoat can eliminate that original, half-baked appearance of electro-zink coating)

credit:
mikeselectricstuff has shown many years ago his frontplate solution without tooling cost. I have borrowed the basic idea from there.

bonus:
Clamping Collet, aka 4 to 3-jaw converter.
The design above calls out drilled M2 threads on both ends of those 6mm alu square-rod. But many mini-lathe owner has no four-jaw chuck for square stock. Find below the drawing of a simple collet solution. The jaws could be the same 1.6mm thick FR4 material as the frontplate/backplate, so you can order them from the very same supplier. I have tried it with glued-together wooden thick-veneers instead of fiberglass, cut out by laser engraver. Not being a precision tool, worked surprisingly well. It is also useful for off-the-center holes on bars and rods.
Because of PCB manufacturing constraints (diameter of routing bit), the inner corner of the square cutout will have a fair amount of radius. That should be square again with the help of a diamond file and a drop of elbow grease.


Fig.9

Alternatively you can utilize rundown set-top-boxes as well, but they are even more diverse in terms of dimensions and formation:


Fig.10

(You may notice the retrofitted panel meters with new scales and backlight)

Thanks for reading,
ElMech_Proto

[ElMech_Proto]

Set-Top-Box UpCycling

During the last couple of years I have ventured on various direction, to come up with ’less-tool-intensive’ home brew enclosures, though many ended up as a one-way road.
I found that one of the easiest method is reusing old enclosures and creating only the front bezel and an additional rear cover.
The next example will provide significant benefits without imposing undue machining hardship.
In this attempts I took a run down set-to-box. It is sturdy enough by its own right, which is a good starting point.


Fig.21

Avoiding plastic-bottom-tray type enclosure is advisable. Inherently to the nature of plastic mould, they just simply build too many features into, devouring otherwise desirable space inside. To a certain extent, it is the same with standard hi-fi size full-sheet-metal equipments too. For structural stability they are using deep drawn features extensively and were able to place them exactly the spots we would intend to use for something else.
Set-top-box where top and bottom halves are sheet metals are the best compromise IMHO, a 30-50VA toroidal transformers, half-of-a-palm-size heatsinks, or even 40mm fans can be shoved into them. The front and rear surface area are usually enough for basic functions, displays, buttons, PWR and I/O connectors. Many of them can accept a grounded IEC receptacle as well.


Fig.22


Fig.23

In order to achieve the desired robustness, jog-fetures are common building blocks of any mass produced sheet-metal enclosures utilizing plastic bezel at the front. We have two major problems with that:
a, They are protruding too long, hence we need more layers to incorporate them.
b, The replacement part, as being wood, it is not that strong compare to the original plastic item. Therefore the new front  should be a few mm wider, consequently it will not be flush with the top and side surfaces of sheet-metal shell.
(The bottom tray coloured in orange, it is actually almost a complete box itself, only its top lid is ’missing’. (see more: fig.25))


Fig.24

The only labour-intensive section is the layered wooden front bezel:


fig.25

To make it easier to comprehend, just imagine it as a multilayer PCB. In our case it is a 5 layer stack-up, ~2.5mm individual thick sheets glued together. This system can accomodate many 'flush to surface' components, hide fasteners, swallow up unwanted features of the enclosure.
This front bezel is akin to layered wooden sculpture. Because of easy to access material, I normally start with 2...4mm thick-veneer. With caution during material selection, after the gluing process, it can appear as one solid block (...well, from a couch distance). This layered approach can accomodate the sheet-metal shell front jog-features, plus you can utilize it to create sittings for front panel components and hiding their mounting hardwares.
The quickest way to get those sheets manufactured is laser-cutting. On the same token, on the most outer layer, you can make your logo and other text-like features produced, using this very same technology. If you really want to proceed to professional outlook, UV-print is sensible. Most of the time on many wooden surfaces, normal size laser engraved features are not crispy/contrasty enough for easy reading at every type of ambient light situation. Smudging coloured wax into finicky lettering do not help also and later can cause issues with certain type of surface finishes. For bigger legends it is acceptable, but not for fine inscriptions.
Surface finish on wood:
Typical coating system consists of three layers, namely the sealer, filler and topcoat.
Normally I roll with two-component sealer, filler if it is required, and something semi-gloss water based laquer with hardener. A few times I have tried french-polish, but it takes ages and easy to destroy a week worth of effort with just one wrong move. Though many times shellac can be utilized as sealer.
Issue almost always arises with oak and many other exotic woods during finishing. Its acid content commonly seeps through the not-yet-dried coating, causing miniature puncture holes, when you try to cut corners during the initial surface treatment process. With those type of woods, as an alternative, you can skip the traditional steps, and use solely wax or hard-top-oil. Sadly, those two usually  demand  some preventive maintenance in every 6-18 months.
Be aware, the final appearance will be driven by the surface preparation and primer/filler layers, not the clearcoat. If you mess it up, you will easily find yourself cornered with a 'can of Bondo', what may lead you to the sad conclusion: the only thing it has left is its calorific value...
For whatever your reason is, bound and determined applying dye, try something what can be mixed into the clearcoat, instead of applying directly onto the bare wood surface, what can end up easily as an unrepairable blotchiness.
LEDs might not be built into directly, but rather their emission should be channeled through light pipes, for eg D1.5mm PMMA rods. Using laser cutter, apply a fair amount of tolerance for those holes, their dimensions will be all over the shop. Epoxi or 10s glue will keep those light-pipes in bay as you make them flush with the front surface using sand-paper.
Usually the top sheet-metal part cries for repainting, but with materials available nowadays, it is not a big challenge. Just try to avoid already damaged or rusted units, they are a pain in the back preparing them for repainting.

’Full-Wood’ enclosures:


Fig.26

It is the hardest to make it right in every aspect. From aesthetic perspective it is OK, but it frequently ends up either too flimsy or too bulky to work with. The inner temperature management is a complete  disaster, plus you will have a hard time facilitating any electrical and mechanical components, because the whole contraption could become an inbreed, as it could have many hard to reach places, like a boat in a bottle. As many mountains from a distance, it looks so temtping to climb, but even before reaching the base camp we may realize, we should be more prepared for that.

Thanks for reading.

[ElMech_Proto]

AnySize Enclosure


Fig.11

We can somewhat combine the two types, I have mentioned in my former entries, to create various size of enclosures using off the shelf ALU flat-bars and additional whatnots forming the side panel sub-assemblies, that will serve as the main load-bearing framework. The only machine we need is a drill press, besides some  completely ordinary hand tools.

Right now, its form factor is a double-height 5-1/4in ODD, however we can create it much deeper and wider. Till circa half-width Hi-Fi size, it is simply a  matter of taste. For bigger overall dimension than in my example, a wooden front bezel could give a better oomph.


Fig.12


Fig.13

The caveat with this approach is avoiding untidy hole pattern on the side, whether their purpose are structural, or thermal, as they can succesfully destroy any aesthetics. Utilizing a 'blank' FR4 PCB as drill template can alleviate the pain of centerpunching thousand times in a well-organized and controlled way. Even in small production run it is worthy to have helping us ensuring consistent hole pattern.


Fig.14

Something between diameter 1.0 to 1.5mm drill bit can be used  as 'marker/center drill'. It is not as accurate as a cnc router, but definitelly better and quicker than using the traditional caliper/machinist blue/center punch troika. Aiming at a +/-0.2mm overall position tolerance, do not forget to place 3 datum holes at the tangent of flat bars (kinda fiducials).


Fig.15


Fig.16

Utilizing the datum holes, with D1.0mm drillbit and double sided adhesive tape you can temporarily attach the drill template onto a given workpiece. To ease its removal, apply some heat to the ALU flat bar.
In order to compensate the inherently not-too-tigth dimensional tolerance of flat bars, there are some additional datum holes shifted from the theoretical value by 0.25mm each, allowing to meet the preferred height of side panel assembly.


Fig.17

Using PPE is strongly advisable during drilling process!


Fig.18

Those Dewalt drill bits works quite well on thin sheet metal, the hole will be considerably circular and precise. Unfortunatelly they do not sell smaller than D4.8mm anymore (D4.2 was super useful for M3 Pemzerts back then).
On the right, aluminium bobbins are a big help keeping the smaller tapping tools perpedicular to the surface. Even as small as M2 you can manage many hundreds threads without get one broken into.
For small scale manufacturing a drilled-through wooden/plastic block are equally appropriate.

Contrary to my assumption regarding M2 threads in 'ordinary' aluminium alloy, the contraption turned out pretty robust. If you deem that M2 fasteners are too frail, the design will accept M3 far and wide as well. Maybe the horizontal 10x2 angle bar (ALU L-Section) has a second thougth about it, but you will see how to circumvent that bottleneck when you are there...


Fig.19

On the middle flat bar I applied sand blasting, hence the totally different outlook, though it is the same base material as anything else in this frame (AlMgSixx). Just try not to place it where can be easily touched, because its surface extremely sensitive on its natural form, even by fingernail it can be scratched. The other, "polished' alu components are more scratch resistant, but definitely woud last longer with proper surface finish. Sending any of your components to an anodizing plan, containing any press-in steel (or non-ALU) part, is a big no no!


Fig.20