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I will share about the my findings from samples made of different aluminum, i.e. Alcoa Mic 6, 6061 and 7075, some comparisons and why I decided to use 7075 for the next batch, some major improvements over the last run (such as the wrapping issues, the gap, the finishing of the brass, etc.), changes in design, price of the kit and delivery period.
The groupbuy should start next week if nothing goes wrong, in order to have the board delivered before Christmas. Stay tuned!
Material selection 
from top: 6061, Mic 6, 7075
6061 is one of the most common aluminum alloys used for Korean keyboard, being economical, reasonably high strength and easy to machine. While 7075 does offer a much better mechanical properties compared to 6061, but many do agree that the additional strength is not needed for the usage of mechanical keyboard case. Alcoa Mic 6 on the hand, is best known for its good stress relieving properties, commonly used to machine parts that require high accuracy.
tl;dr
- stregth
7075 > 6061 > Mic 6
- price
Mic 6 >> 7075 > 6061
To determine the aesthetic appeal of different materials, all 3 materials went through the same process of machining, sandblasting and hard anodizing (35 micron). The major differences in the final products are the color and surface smoothness.
- Color
from left: 7075, Mic 6, 6061
- Surface smoothness
7075
6061
Mic 6
Taking aesthetic appeal, price and strength into consideration,
7075 will be used in the next groupbuy.
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Improvements- Gap
It is much more appealing than round 1. Although no one has made a complain about the gap, but it does bother me a lot.
- Brass finishing
mirror finish
normal buffing
electro nickel plating
The brass for CE will be electro nickel plated. I have not decided on what kind surface to go for thought (sandblast or mirror polish)
- wrapping issue
As you can see form the photos, the top part lies flatly even though it is not screwed to the bottom case.
- Anodize color variation
As much as I want a perfect anodize for CE, unfortunately it is not possible. What I can do is only to minimize the color variation.
mic 6 sample. To give you an idea, the above variation in color is not acceptable.
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Changes in design 
thinner border
the usb hole
this is something i learnt from the OTD board. The mounting point of the plate. The plated is mounted at an very small angle, to reduce the contract surface with the case for maximum "thock"
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Specifications: - Full aluminum 7075 case
- 8 degrees slope
- Electro nickel coated brass weight
- Plate material: aluminum
- Support 84 and 86/87 layout
- ISO and ANSI
- A87U PCB
- Fully Programmable
- Full LED backlighting
- Controller parts are pre-soldered
- Only 25 sets
Color options: Blue grey, pink, black(hard anodize) and olive green(hard anodize)
blue grey
pink. photo by filphil
olive green
Price:
