General Design and Manufacture Discussion

Phuncz

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I've mentioned this to Necere on [H] but how about Acetal and Delrin materials ? These are commonly used with waterblocks because of their excellent milling properties without using a metal (I would guess for corrosion reasons), but these might also be a worthy addition to custom case manufacturing where aluminium might be too expensive. I don't know if it actually is, but I'd guess Delrin or Acetal are much cheaper in material costs. Do you have any experience with these and can give your point of view on what it could have use for in custom SFF case design ?
 

EdZ

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The material cost may be much lower, but the machining cost of running everything through milling is dramatically higher.

Sheet Aluminium (and Steel) can be stamped, punched, spot-welded, bent etc. in a few fixed stages in a 'run'; i.e. you run a few hundred sheets through the same stamping operation in quick succession, then run those same few hundred processed sheets through another operation (e.g. bending) in quick succession, and so on. If you need multiple stamping operations, you can even use the same machine and reconfigure it once between runs.
If you needed to mill something, even if the actual milling step could be fully automated (i.e. your milling does not require someone to walk up to the machine, remove the part, flip it over, re-mouint it, and re-centre the machine) you can only process one part per machine at a time, and the actual processing take a LOT longer.
There are factories that use milling for mass-production by separating the milling stages and having a dedicated machine for each stage, but this means you can only ever build one part with that factory, which cost you a few million dollars to set up (better hope you're going to sell a several tens of millions of units!)

For cheap plastic-forming, injection moulding is king. But the startup costs of building the durable metal injection mould (which even with the best flow simulation may need one or more prototypes to get right) are so high that you need to guarantee that you are building a few tens to a few hundreds of thousands of pieces for it to be worthwhile.

3D printing might end up as a medium method, cheaper than milling but more expensive than injection-moulding, but at least for the moment it's still only marginally cheaper than milling due to the build-one-thing-at-a-time issue. There have been proposals to design SLS (Selective Laser Sintering) and FMD (Fused Material Deposition) machines with multiple parallel 'print heads' to allow a machine to build many parts at a time with one set of drive electronics and motion hardware, but so far I know of no company that has actually done so, let alone used it in production. There's also the issue that the surface finish of 3D printed parts isn't as good as moulded or milled parts yet, so you're limited to either internal parts only or adding an extra surface-finishing step e.g. tumble-polishing (which may break parts), chemical finishing (which will reduce the outer dimensions so needs to be compensated for in design), surface coating (e.g. painting with a thick paint) or finishing by hand.
 
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Phuncz

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Yes, all true but it would still have a use-case if a company like EKWB can manage just fine with maybe half their blocks using Acetal as a large part of their products. I'm not talking about using Acetal in replacement of aluminium for sheets or panels, but the more difficult parts that require milling anyway. Like for instance a button or a bracket.
 

PlayfulPhoenix

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Simple question: is aluminum generally more expensive to manufacture with, compared to steel? (Accounting for the fact that aluminum sheets tend to be thicker, to compensate for the additional malleability)
 
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EdZ

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Simple question: is aluminum generally more expensive to manufacture with, compared to steel? (Accounting for the fact that aluminum sheets tend to be thicker, to compensate for the additional malleability)
It depends on what you're manufacturing.

For cases, the assumption with Aluminium is that the Aluminium is going to be the finished outer shell of the case. This means you need to be more careful in your machining operations, cannot do some operations that would leave tooling marks on the exterior (or add a cleanup step), and this extra work costs money. The assumption with a steel chassis is that it will either be painted, powder-coated, or have an external non-structural plastic or Aluminium cosmetic shell applied.

Then there's economics of scale. When building many thousands of units, Steel is cheaper to buy than Aluminium for the same structural strength (because both by volume and by weight you need more Aluminium then Steel for the same strength element), so mass-produced cases that can afford dedicated tooling will generally be steel. When you're making smaller runs of cases (e.g. Lian Li) the materiel cost isn't all that much compared to the machining cost, so it makes sense to go for the 'nicer' material that has a higher value to the people buying the case.
 
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4RTEX

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Generally aluminium is no that easy to work with especially when welding. I see some good coded welders to struggle to TIG it. Not so much of a problem when you are not planning to weld. Aluminium has less tensile strength, so perforations de-form material, which then has to be rolled flat to compensate. Aluminium requires less tonnage to bend and there is a lot less spring back. Bending aluminium (depending on grade) with sharp tools is not advisable due to more chance of it to crack (not as dense as steel). Aluminium is easy to drill and in general fabrication behaves better. Imagine you overbend a 90 degree flange on press - it's easier to put it straight. Aluminium is lighter so handling is also easier. Modern CNC laser can cut aluminium assisted by compressed air (so does thin mild steel). Aluminium being softer also produces less tool wear when punched. You can buy plastic/vinyl coated aluminium for extra protection, not so much with mild steel.

Mild Steel (non structural) is generally a lot cheaper. Here is it's biggest advantage on huge scale. Bending mild steel is more consistent therefore easier (due to more resistance = tensile strength + density). You can spot weld mild steel which is useful in some applications. Majority of shops will charge a lower rate for laser cutting mild steel as it requires oxygen which is cheaper than nitrogen, gas used typically for cutting aluminium and stainless. Our shop for example charges £100 for 1h of oxygen cutting and £150 for nitrogen cutting. Generally mild steel is stronger but it is not rigid, there would be more flex in mild steel construction that aluminium (comparing DD11 mild steel to 1050 H111 aluminium).
 

Aibohphobia

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Thanks for all the input guys! Lots of good info here.

What options are there for tool-less panel attachment? I like the ball stud and clips that Lian-Li uses but they don't seem to be readily available anywhere I could find. I stumbled across these. Looks similar to what Caselabs uses, actually I'm almost certain it's the same thing.

Any other options I'm not aware of? Only one that comes to mind is magnets.
 
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PlayfulPhoenix

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=What options are there for tool-less panel attachment? I like the ball stud and clips that Lian-Li uses but they don't seem to be readily available anywhere I could find. I stumbled across these. Looks similar to what Caselabs uses, actually I'm almost certain it's the same thing.

Any other options I'm not aware of? Only one that comes to mind is magnets.

This! I'm a huge fan of toolless panels, so I'd be very interested in any possible solutions.

The Pencom ones you linked work functionally, but would go through to the opposite side of the metal that they are installed in. So they wouldn't work for aesthetic reasons.
 

Phuncz

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I also love the toolless panels on my Ncase M1, I am interested how the Caselabs work out in real life, with the metal clip. Won't it vibrate the panels and need dampening ? The clips also need two screw sockets and screws, which makes me think it will be more expensive than the plastic clips (although more fragile) that Lian-Li uses.
 

rawr

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Ok, say I have a case design in mind. I've got the layout sorted. It's going to be aluminum. What steps should I take now in order to turn it into a real thing?
 

Phuncz

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While I'm no professional or even amateuristic designer, I do pick up things. My comments below might not be entirely accurate, I expect that I'll be corrected when something is wrong :)

Depending on the design, you are going to need to find a suitable manufacturer. The materials dictate the possibilities and you need to make your design work with production possibilities. Not every manufacturer has the facilities or experience to work with everything you want. Lian-Li is very capable with aluminium for example, while Silverstone is more capable of SECC and plastic construction.

Like plastics injection molding is very expensive at the pre-production stage, the molds cost a lot of money, albeit each piece itself is very cheap. Aluminium and steel can be bent, pressed, perforated, milled and whatnot, but is very difficult to work with when it is a complex shape. This topic already has a lot of useful information on this.

If you can't figure out what materials you need and will work, let an experienced designer take a look at it. When it has been figured out what production process and materials are suitable, you need to adapt your 3D model to a production-ready file. This will also depend on the production process and the lesser you can do yourself, the more it will cost. At this point, you'll have an acurate cost estimate for your project.
 

Aibohphobia

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I highly recommend mocking something up. Use cardboard, wood, whatever you can do because fixing design issues in production is expensive.

Once you've verified the layout is physically sound then it's on to getting a prototype. If you find a willing manufacturer you could just give them a rough sketch but that'll be expensive because you can expect to pay anywhere from $30-$100 per hour for an engineer to design the case in a CAD program.
 

rawr

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Thanks. However this would be much smaller scale, I won't be pulling off an NCASE. The design would also be very simple. It would more or less be something like this:

http://hardforum.com/showthread.php?t=1769885

Obviously with differences though.

Production would thus be smaller, and probably in batches, like Lone Industries. Like them, I'll probably go for a smaller aluminum shop, rather than a big company like Lian Li.
 

Aibohphobia

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@KSliger I'd like to have some of the panels tool-less and was looking into these: http://www.pencomsf.com/ball-studs-and-clips/

The way CaseLabs does it is they use self-clinching male threaded studs and the female threaded ball studs, which I assume is the easiest way to do it.

Could you do something like this with the male threaded stud pressed into the inside of a hem? And if so, how close to the edge can the stud be and would it work in 20 gauge sheet?



Edit: Ok, after watching some videos on how hems are made I don't think this is possible.
 
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KSliger

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@Aibohphobia
Due to the way hems are formed it wouldn't be possible to make that without making a custom hard tool to avoid smashing the hardware.

But you're right on the money in regards to what CaseLabs is using for their ballstuds, however on the backside he's definitely using:
http://catalog.pemnet.com/viewitems...isplacement-head-studs-types-fhl-fhls-unified

These are through hole, low material displacement, so they won't leave a ring showing on the backside. And what they do have of a ring is completely hidden by the powder coat. Once the ballstud is threaded on you won't have the compressive weakness of through hole, or the tensile weakness of concealed head.

I actually have all these hardware in stock, if you'd like I'll make a sample tomorrow in both FH and FHL and send it your way.
 
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Aibohphobia

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Heh, I watched that exact video when I was double-checking how hems are made. I see now that what I'm asking for isn't doable.

So instead, how close can I put the stud to the hem edge?


I should be good with the CAD files from PennEng, thanks for the offer though!
 
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KSliger

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For edge of hem to edge of hardware I'd go with 0.05 ±0.005 as a very comfortable number.
Absolute minimum is 0.042.