The all-ceramic body of Mi MIX4 solves more than just the hand feeling problem

If you have passed by Mi Home recently, then I highly recommend you to play with Xiaomi's newly released MIX4, not because of the full screen with an under-screen camera, but to experience the wonderful feel of the ceramic Unibody body.

From the book data, the 225g, 6.67-inch MIX4 seems to be another "fitness artifact", and the hand feel should not be much better.

But after getting started, you will find that the MIX4 has a great improvement in the hand feel compared to the other "heavyweight king" 11 Ultra (234g).

MIX4 not only has a more balanced overall weight, but the integrated ceramic back shell can bring a smooth transition without seams and faults, making people unable to stop rubbing its smooth frame.

Xiaomi calls this process ceramic Unibody. Will this be the next optimal solution for "one-piece molding"?

Aluminum alloy, the former "god"

In 2008, Jobs released the world’s thinnest and lightest notebook computer in a very interesting format. He slowly opened a briefcase on the stage and took out the MacBook Air with the thickest thickness of only 19.4 mm to the world. Show its slimness.

Later, when Jony Ive shared the secret of MacBook Air "slimming", he mentioned the processing technology of "Unibody" for the first time.

Unlike the intricate splicing frame of previous notebooks, the palm rest of the MacBook Air is processed from a complete aluminum block, which not only ensures the strength and consistency of the frame, but also forms a closed and simple shape.

This is a design concept that spans eras and categories. Notebooks, MP3s and even remote controls will use Unibody to achieve a nearly perfect and seamless shell shape, and mobile phones are no exception.

Apple first applied the Unibody process to the iPhone 5. The shell of the whole machine was cut from a whole piece of aluminum alloy, and two hollow sections were reserved for the glass cover on the top and bottom to place antennas and other components.

Subsequent iPhone 6, 6S followed the concept of one-piece aluminum alloy formation, and on the bright black version of iPhone 7, the integration of the whole machine reached a peak.

The premise is that you are looking at it in a shop window or a craft museum, not playing with it.

Aluminum alloy has good machinability and ductility, so it can produce many desired shapes through CNC machining. It is a very ideal one-piece housing material, but it has many problems to be solved if it is used in mobile phones.

Metal has a natural shielding effect on wireless signals, so whether it is Apple or other manufacturers that make a metal one-piece shell, it is impossible to be truly seamless. The glass cover of iPhone 5 and the leucorrhea of ​​6 are both giving way to the antenna.

Secondly, there is a trade-off between strength and corrosion resistance. iPhone 6 used to use a low-strength 6000 series aluminum alloy, and there was a "bending door" that could not put the phone in the back pocket.

Later, the iPhone 6s used a higher strength 7000 series aluminum alloy to solve the problem of being "bent". However, due to the higher content of magnesium and zinc in the alloy, it is in a relatively humid environment (for example, sweaty hands). Prone to oxidation to produce unsightly "worm-eaten" patterns.

In addition, aluminum alloys also have problems such as difficulty in coloring and inability to wirelessly charge. In terms of vision, touch, and functionality, it is difficult to balance aluminum alloy materials.

As a result, mobile phone manufacturers represented by Apple have abandoned the aluminum alloy Unibody design and replaced it with a sandwich structure of back cover, middle frame, and screen.

In this way, the need for wireless charging is solved, but the seams and texture created by the splicing of materials also make the unity created by Unibody in the past gone forever.

Distinctly different ceramic Unibody

Ceramic is a "non-mainstream" material, but with its unique warm feel, mobile phone manufacturers have always been fond of it, and often use it in the high-end versions of their flagship models.

Compared with aluminum alloy, ceramic material is like its opposite.

Ceramics will not fall off the paint, will not corrode, are not easy to obscure the signal, and can be charged wirelessly, but the disadvantages are also obvious. The processing of precision ceramics is more difficult.

Different from directly processed metal, if you want to process ceramics into the back cover of a mobile phone, you need to "make porcelain" and then "process" it.

Zirconia and microcrystalline zirconium with fine particle size and good dispersibility are the mainstream materials for making mobile phone ceramic back cover. In order to sinter a precise ceramic structure, it is often necessary to grind the material into ultra-fine nano-powder before sintering, and then press it. Into the shape of a mobile phone shell.

Don't underestimate the molding step, the choice of molding process determines the final effect of ceramics.

The mainstream molding processes generally include gel injection molding (Huawei P7), tape casting (Xiaomi 5), etc. However, to obtain a complete Unibody ceramic body, dry pressing molding processes are often used.

The pressing process is generally divided into two steps. First, dry pressing is used to press the powder into a plain embryo of the backplane, and then a period of static pressing is used to form a dense embryo.

▲ Artistic effect, please do not put your head into the furnace

Before it is sent to the boiler for firing, it needs to go through a very critical step-degumming, because a large amount of forming agent is added in the process of making the embryo, and it needs to be preheated before firing to discharge the gas that may be generated, otherwise it will burn out. Ceramic bubbles will appear to affect the appearance.

The firing process is not like baking at home. It is necessary to pay close attention to the pressure, atmosphere and heating curve in the kiln to produce a perfect back cover. An abnormal parameter may cause defects and cracks in the ceramics. .

After firing, the ceramic can be further processed by CNC grinding, polishing, etc., and finally a perfect transition and integrally formed back cover can be obtained.

Compared with the aluminum alloy Unibody process, you will find that each process of ceramics is interlocked, and any error in any link in the middle will directly affect the yield rate.

And the waste in the process cannot be recycled like metal, which keeps the cost of ceramic materials high.

At the MIX2 conference, Lei Jun revealed that the cost of the ceramic Unibody reached 1,300 yuan, and the high cost hindered the popularization of materials, making ceramics have been high and low.

In addition to high cost, weight is also one of the factors that limit the development of ceramic materials. In recent years, whether it is Xiaomi or Huawei's high-end ceramic version of mobile phones, the weight has gone by half a catty.

▲ Picture from: XYZONE

The Xiaomi Mi MIX4 this time announced that it has adopted a new lightweight process, reducing weight by 30%. From the perspective of the structure of the disassembly, it may be that plastic has replaced some ceramics to form a composite structure.

From MIX2 to MIX4, the same is the ceramic Unibody craftsmanship, but the maturity and precision of the craftsmanship have been greatly improved. These advancements may mean that we can soon bid farewell to the sandwich structure and return to the beauty of the unibody. .

Can glass be used as Unibody?

What will the mobile phone of the future look like? Vivo built a bold vision two years ago-vivo APEX 2019.

This is a conceptual mobile phone. The whole machine has no holes and buttons. It is composed of a front screen and an integrated glass on the back. Vivo calls this process Super Unibody.

Indeed, compared to metal and ceramics, the glass Unibody brings the smallest sense of material splitting. From the screen across the frame and then to the back cover, all the fingertips touch are glass.

The ductility of glass is higher than that of ceramics, so theoretically it will be less difficult to process, except for this integrated "water drop" glass.

In order to ensure that the frame of the mobile phone has a high enough strength, the glass of the frame part of APEX 2019 is thicker than the back cover, and there is a continuous transition from the frame to the back cover. The traditional hot bending molding alone cannot meet the requirements. .

Vivo chose to use a full CNC integrated molding process on such a fragile glass, and through the combination with hot bending processing, to polish this piece of Unibody glass with different thicknesses and curved surfaces, which is extremely difficult to process.

In addition, coloring is also a problem. Coloring on the back cover of ordinary glass is not difficult, whether by coating or spraying paint to achieve a variety of effects, but on the glass with such a large curvature span, it is difficult to ensure the uniformity of the coloring.

Various difficulties make the design of the glass Unibody hard to find after APEX 2019, just like the streamlined design of the "Three-Body" water drop spacecraft is destined to belong to the future design. It should be a handicraft in a museum, rather than being held by people. Daily use.

"It's not just a seam, just wear a shell."

The discussion about Unibody is not only about the feel, but also about the future concept of product design.

We like a seamless product, not only because the hand feel of seamlessness is more friendly, but we see a new product form, we see the future of a product through seamlessness.

This is a DV from 20 years ago, and the gaps in splicing are everywhere.

Back to modern times, compared to this AX 100, it is much more refined.

This sense of exquisiteness is the change brought about by the continuous progress of design, materials and assembly technology. As the most used electronic device in our daily life, the technology of mobile phones is currently at the forefront of all electronic products.

We pay attention to the seamless advancement of mobile phone design, but we are actually expecting this seamless design to spread into the electronic products in our lives.

Seamlessness will not be the reason for us to buy it, but we can appreciate a product through these simple beauty.

In the era of handicraft industry, we can touch the ink marks on the scrolls and the nicks on the carvings to establish emotional resonance with the craftsmen, and feel this "texture" that is constantly polished through labor.

The advancement of modern industry allows mechanical cutting to replace manual polishing. Micron-level precision-controlled machine production ensures the uniform quality of each product, but it is easy to cover the "texture" formed by human sweat.

The essence of the "texture" of craftsmanship comes from overcoming difficulties. A stone has no texture at all, but the unremitting polishing and carving of a hard stone makes it a handicraft, and the texture emerges spontaneously.

The Unibody process of different materials is the era when machines replace manual production and overcome new difficulties. Unibody craftsmanship minimizes the sense of splicing of materials and creates a sense of natural growth. Behind these erased seams is a new interpretation of "texture".

Apple published a book called "Designed by Apple in California" in 2016, which records Apple's product design from 1998 to 2016. In the introduction to this book, Jony Ive says:

I am sure that human perception of care is the same as our perception of carelessness. I think that what we perceive and perceive-maybe not consciously-is far beyond the object itself, we can perceive the object The group of people behind, what they do is not just to make something work, they sincerely care about the invisible details, but also care about the big ideas and primary functions.

Unibody, seamless design, hand feel, these mysterious and mysterious discussions are destined not to be a topic that arouses public discussion. They can't use exaggerated numbers to attract people's attention, but when the mobile phone has competed with all the functions, these The interactive experience design directly related to people will undoubtedly be the last point of struggle for flagship phones.

Higher, higher.

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