Dust mesh and alternative alloys for the S4Mini

[Minipiman]

I was wondering if anyone has used some kind of dust mesh on the Skyreach 4 mini ventilation holes. Could it be a good idea to sell it as a separate product on the NFC website?

On the other hand, I was wondering if Josh considered building the 4 Mini on magnesium alloy rather than aluminum (~1.7g/cm3 vs ~2.7g/cm3). That would bring the weight from 1.1kg to ~0.6 approx (maybe the reason not to do it is economic...)

 

[Josh | NFC]

@Supercluster might be able to help answer the possibility of a sheet metal magnesium chassis. He seems to be a wiz when it comes to material science.

I would love to do a frame in magnesium. I don't know much about it other than it looked like quite the undertaking. Kinda off topic but I have wanted to do a pressed magnesium frame ever since heard about these machines:

 

[Supercluster]

My physical experience with magnesium is limited, though I have rebuilt a ThinkPad T61p from two wrecked ones:

During that process I have had the opportunity to inspect two unibody magnesium alloy endoskeletons which enabled the ThinkPads with their "mil-spec" certification. The "roll cages"(as they were called) are remarkably light and stiff with most of the material being under 1.5mm thick.

The touch and flex feel of cast, non-coated, environmentally passivated, magnesium is somewhere between aluminium and a carbon-composite. I am not sure about the alloy used in making the skeletons. For concrete UTS, Young's modulus, temper availability, and other material properties values you should look up the certificate for the specific alloy. The two commonly used (and relatively easily sourced) are AZ31 for wrought and AZ91 for cast alloys (the AZ stands for Aluminium Zinc).

I am able to confirm one of the main downsides as the frames were cracked in a few places. Alas, I have no images of my own so the internet ones will have to do the illustration of what I am talking about:

Spoiler: T500 & W540

What can also be observed is the comparative cost cutting in case of the ThinkPad T500 (upper image).

It should be noted that cast alloys as a rule have a lower tensile strength, and are generally inferior, than the wrought ones. They are also appropriately less expensive to produce. If you want to delve further or know more about this topic, you should do so on your own, as higher understanding of crystal lattice structure is required than I currently possess.

The above mentioned downside of using magnesium alloys is their brittleness at room temperatures. This makes them inherently unsuitable for sheet metal bending, at least in the "industry standard" terms (I doubt that Lian Li has temperature regulated break presses).

This publication refers to wrought alloys and summarizes with the following:

"The sheet metal forming of magnesium alloys requires an adaption of the forming processes utilized. Due to limited formability at room temperature, heating above a temperature of 200 to 225 °C is necessary in order to activate additional gliding planes. By the example of roll forming, the temperature regime and implementation of heating equipment into the forming process is illustrated."

The AZ31 alloy is commonly rolled and extruded, and the consensus is there.
Reference for a cast magnesium alloy.

To make the post more complete I will mention the "witchcraft" of alloy production that is extrusion of rapidly solidified powders, which essentially doubles the material properties values, even compared to commonly used wrought methods.

As for the machining of magnesium.. Well, magnesium is a reactive alkaline earth metal and the chips produced during machining are flammable so it makes an additional hazard (expense) in the production chain.
It does, however, machine very nicely:

Spoiler: D800E

To round up, I will reiterate that magnesium is naturally passivated, hence, the oportunity to be anodized similarly to aluminium, as a reference to the finishing options.
Much else is there to be said about magnesium as it is truly a remarkable material, to which the future belongs, but I will end the main post body here.

When transitioning into the scales of economy we should be aware that the global magnesium industry is still over an order of magnitude smaller than the aluminium industry.

Summa summarum:

A magnesium case is certainly a possibility, though unlikely in the current production budget and market maturity constraints. As I have understood @Josh | NFC mention somewhere (Kind words. Thank you), he is looking for something able to be produced with greater volume, as well as be more price-competitive than the current setup. Although it will undoubtedly be more represented as we go further, today, the magnesium industry is immature for such an undertaking.
This is, naturally, only an opinion and I would enjoy to be proved wrong by the NFC (anyone, really) with the release of a (for example) extruded, magnesium, limited, edition of the Mini.

 

[Krauthaus]

https://www.amazon.com/dp/B01JKVP1G2/?tag=theminutiae-20 <- I got a few of this from a earlier project; when I am finished with my build (about 4-6 weeks; depending on part delivery) I will cover the case in one of these and measure the temperature under load. (It will make them worse; of course. But it would be interesting to see if it is acceptable or not. Since I will use my build for work under dirty conditions I will further investigate what kind of fabric could be thin engought with a good airflow. I also thought on some non permanent sprayglue and some stretch cloath. (Like strech it as hard as you can and apply it on the sprayed case; cut the acess.)