Let’s first watch the videos about the Apple Watch CNC machining process, with detailed explanations after the video.
Although this videos explaining the Apple Watch have a strong flavor of showing off their skills, you have to admit that this is an almost luxurious investment by a team regardless of cost, and the focus is no longer just on the supply chain.
It is still difficult to predict how much gold and stainless steel Apple will purchase for Apple Watch, and it is also difficult to predict whether it will have a profound impact on the price of corresponding materials, processing technology and even the entire industry like the large-scale use of aluminum alloys a few years ago.
It has to be said that Apple’s pursuit of craftsmanship gives people a sense of ritual. It is trying its best to raise production standards to a new level. Perhaps it is because it knows that it is facing a company with hundreds of years of history. The watchmaking industry is home to dozens of well-known watch manufacturers.
Apple Watch Sport – Aluminum
To say that Apple is the most proficient in aluminum product processing in the world, few people would deny that aluminum alloys have appeared in all of Apple’s product lines, from the early iPod Classic to the later MacBook Air and the latest iPhone 6. More importantly, Apple has established a global aluminum alloy supply chain, which has a profound influence on the entire industry and has attracted many competitors to imitate. Therefore, it is reasonable for Apple to use aluminum alloy, which it is most familiar with, to produce a “cheap version” of Apple Watch Sport.
On the Apple Watch Sport, Apple abandoned the previously commonly used aluminum alloy 6000 series (the main components are aluminum, magnesium and silicon), and instead developed a new 7000 series aluminum alloy, adding metal magnesium and zinc. Jony Ive said in the video that the newly developed aluminum alloy has increased its strength by 60% while maintaining the same weight. According to analysis by AtomicDelights, the two existing commercial aluminum alloys closest to the description are 6061 and 7075.
Apple Watch – Stainless Steel
Stainless steel is a commonly used material for making high-end watches. The materials used by Apple on the Apple Watch are relatively conservative. They use 316L stainless steel instead of liquid metal, and they do not use very complicated cutting processes. 316L stainless steel is also often called medical stainless steel. This material is mostly used in medical devices and food processing equipment for a simple reason: to prevent the penetration of metal atoms in internal components. It is for the same reason that 316L stainless steel has become the most widely used alloy material in watches. Watch manufacturers have been working hard for decades to reduce the effects of nickel allergy, with Rolex and Omega having reduced nickel allergy to an almost imperceptible state. Therefore, AtomicDelights speculates that Apple has been trying its best to avoid nickel allergies during metal smelting and processing.
Apple Watch Edition – Gold
The gold used on the Apple Watch Edition comes in two colors, one is yellow that is close to the original color of gold, and the other is rose gold. The materials of both styles are alloys. Silver, copper, and palladium are mixed in 18k gold in a certain proportion, and the corresponding colors are adjusted.
There have been many rumors about the material of the gold version of Apple Watch. It is not made of ordinary 18k gold, but has been treated with special processing technology. JonyIve also confirmed the news in a follow-up interview with foreign media, saying that the special CNC processing technology makes the gold atoms aggregate more closely, making the gold shell of the Apple Wacth Edition harder and more wear-resistant. And this is just a microcosm of the material and production processing technology of Apple Watch.
Apple uses a surface milling cutter to CNC cut the gold ingot, controlling the ingot to a specific thickness with an accuracy of 0.01mm. The reason for ensuring such accuracy is that unevenness on the surface of the ingot will directly affect the final hardness of the machined parts.
Next comes the true compression work-hardening process, in which the metal ingot passes several times under a roller, compressing the overall thickness by a few microns each time. At the end of the entire process, what remains is a flat, high-density alloy billet with target hardness and thickness.
After that, Apple omitted a lot of processes in the video and directly showed a billet that was close to the outline of Apple Watch. In the picture above, the cast billet still has traces of processing, and the corners are tougher. In the picture below, when using an ultrasonic density detector to detect defects, the inner corners of the billet have been polished with bevel chamfers. In other words, Apple moved the billet from one CNC milling machine (CNC) to another just to cut chamfers on the billet? This is a question found in the video, and it does not rule out that Apple has made some adjustments to the process just for video shooting.
The next part is to use an ultrasonic detector to detect the density of the slab to eliminate unqualified products. Strictly speaking, this should be called ultrasonic immersion flaw detection technology. For a consumer-grade product, this step often is omitted, and many high-end watches are no exception. Because consumer-grade products often do not require such high precision, only medical implantable devices that work continuously with high intensity and rotating parts in aircraft engines require strict flaw detection. This process is not only time-consuming, but also requires specially customized equipment and costs a lot of money. Apple’s demanding attention to detail is evident here.
The screenshot above shows the casting being held in place with a small hole in the middle, and then a full-radius edge cut out of the billet using a custom-built CNC mill. In addition, it can be clearly seen from the picture that Apple uses a relatively tall cylindrical workpiece fixture, so it is very likely to use a five-axis milling cutter. The right buttons, Digital Crown (digital crown), and microphone holes will also be used. During this process it is cut into shape.
In the subsequent video, Apple showed off the exquisitely designed and jagged Digital Crown, but it was a finished product without too many details. The cutter used to cut the serrations looks like it was custom-made, with the edges of the cutter shaft being softer to increase hardness and the life of the cutter.
Apple even goes through the processing process of the buckle part. AtomicDelights believes that this process may be far more interesting than the case part. Apple’s redesigned watch buckle has a more complex surface. This may also be the first time Apple uses surface profiling milling machines to process parts. Apple has always had excellent quality control in mass-produced consumer products, in part because it is good at breaking down the production process into simpler 2.5D tool paths such as extrusion or stamping, while maintaining product accuracy and precision. the complexity. If the buckle parts are also 3D milled, it will be more complicated and time-consuming.
The final polishing part, which Apple shows in the video, is done manually. Looking back at the previous video content, Apple’s automated processing technology has reached a very high level and has penetrated into almost all links and almost all components of the product. We cannot confirm whether the entire polishing process is completed by hand. The reason for this Whether it is because the human eye or human processing techniques are more precise than machines, or whether it is just to add a little hand-made nobility to the product, we don’t know.
In Apple’s video introducing the Apple Watch CNC processing technology, the first thing that appears is a molten 316L steel plate, which is the mandrel. The molten stainless steel flows from the bottom of the crucible and then goes through a series of shaping processes before finally forming a solid as the viscosity of the metal molecules increases. This process requires precise control to ensure the grain structure and hardness of the core rod. Since the product is shipped in large quantities, Apple needs to know the metal composition and proportions in the crucible, and accurately control the temper, hardness and core rod size.
In Apple’s video introducing the Apple Watch CNC processing technology, the first thing that appears is a molten 316L steel plate, which is the mandrel. The molten stainless steel flows from the bottom of the crucible and then goes through a series of shaping processes before finally forming a solid as the viscosity of the metal molecules increases. This process requires precise control to ensure the grain structure and hardness of the core rod. Since the product is shipped in large quantities, Apple needs to know the metal composition and proportions in the crucible, and accurately control the temper, hardness and core rod size.
The picture above shows the changes in the grain structure after casting (Casting, the process used by Apple Watch Edition), machined (machined) and forging (Forging).
What is obtained after forging is a net-shape component; this process cannot produce more precise structures such as holes, slots, threads, etc. At this time, it is the manufacturer’s favorite CNC machine tool’s turn to come on the scene. The biggest function of forging is to increase the strength of components. As can be seen from the comparison chart above, the forged parts have a complete crystal lattice, which is similar to a flowing state, and the direction of the crystal lattice is consistent with the shape of the parts, which ensures that the parts being processed have sufficient Strength of. The above picture also explains why the industry usually uses the forging process when processing high-strength metal parts such as tank tracks.
Then three forging blanks and a customized five-axis clamp appeared in the video. Forging is not a very precise process, so in the subsequent CNC machining process, one of the challenges is to find a datum plane and use it as a reference to accurately process other parts of the part. We can see that the top of the forging blank on the right side of the picture above is milled into a square shape. This part is probably reserved for fixing the forging blank after flipping it over.
The next step is to use a five-axis milling cutter to cut out the crown, microphone hole and other fine structures. It should be noted that when milling the buttons and crown slots, Apple does not use a milling cutter with the same width as the opening, but a smaller cutter. This can prevent the edge of the opening from becoming thinner during the processing and maintain the thickness. Surface smoothness.
Then it’s time for Apple to show its ultimate pursuit of quality and details – CMM, whose full name is Coordinate Measuring Machine, a three-dimensional coordinate measuring machine. In the motion path (X, Y, Z), CMM is similar to the CNC machine tool that was often mentioned before. The difference is that CMM usually uses a granite frame as a platform and replaces the milling cutter with a ruby probe, which can accurately measure objects. The three-dimensional coordinates of surface sample points are compared with the original CAD model. CMM can automatically generate reports to determine whether parts are qualified, and can also track and detect dimensional fluctuations of a certain batch of products. In the most sophisticated workshops, CMM data can also be directly fed back to CNC machine tools, which adjust the machining process to offset errors.
After CMM detection, the automatic polishing process comes. The difficulty with overall polishing is that Apple wants to keep the corners and sharp edges in the part, and the polishing wheel touches almost every edge and surface. Poor control will not only smooth the edges and corners, but also damage the polishing wheel. It can be seen from the video that Apple uses gray polymer to fill the bracelet slot, crown, and button interface. This ensures that the case is fully polished and preserves the edges and corners of certain locations on the case.
In the final part of the case processing, JonyIve quickly explained the coloring process of the deep space black Apple Watch in the promotional video. It is called diamond-like carbon, which is actually a tungsten carbide coating (Tungsten DLC). It is very strong and can be made very Thin. This process is often carried out in a vacuum chamber and is the coloring method for many high-end watches and knives. One of the advantages of tungsten carbide coating is its very good durability.
At the end of the video, Apple shows off the manufacturing process of chain straps and Milanese straps. The most interesting thing among them is the latter. Although it can be seen at a glance that the wire has been electroplated and polished, it is still unclear whether it has been wound before putting in the braiding tool, or whether it was put into the braiding tool first and then wound. Know.
In the final part, Apple showed the processing method of Apple Watch Sport’s Digital Crown in the video – laser. On the 18k gold Apple Watch Edition and the stainless steel Apple Watch, the serrations on the crown are carved with a milling cutter, while the serrations on the Sport are carved using a laser. Some people pointed out that the crown was sandblasted, but it is difficult to tell in the video whether the laser-engraved serrations were before or after sandblasting. The crown is fixed on a rotating indexing chuck exactly where the laser beams intersect. The reason why the gold and stainless steel crowns are CNC processed may be that the surfaces of these two materials are reflective and are not suitable for laser processing.
Comparing the processing methods of the three watches made of different materials, a very interesting discovery is that the internal structure of the Edition case has several grooves, which are not found in the standard version and the Sport version. It is difficult to tell whether these grooves are used to strengthen the case or to reduce the weight of the gold case.
Many people have discovered that there is a six-pin interface in the strap groove on one side of the Apple Watch, which may be used for system programming or testing. Since video recording may be completed several months before release, it is still unknown whether this interface will be included in the final mass-produced Apple Watch.
In the video, when talking about design and craftsmanship, JonyIve often uses the word “care” to describe it. This is actually a point worthy of scrutiny, because it neither refers to the craftsmanship of traditional hand-made products, nor the precision and meticulousness of German or Japanese cars or other mechanical products. “Elaboration” is more about the pursuit of sparing no effort in making products, no matter how huge the gap is between the raw materials and the final product. If not, I am afraid that Apple, like others, will give up the forging method to process stainless steel watch cases; the hardening process of gold alloys will probably no longer appear, because almost no one in the entire industry will try it; Apple will not try it either Carefully use a laser to polish the burrs inside the microphone opening, because few people will take apart a watch to feel that it looks exactly the same.
CNC Machining Watch Components 
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