What Tesla's Optimus is made of, and who supplies the parts

Tesla is getting ready to build Optimus, its humanoid robot, on converted car lines in Fremont, California. The parts going into it come from a supply chain that barely existed a few years ago. Elon Musk put it bluntly on the company's July earnings call: "With Optimus, there is no supply chain." He said Tesla has had to assemble one from scratch or make the parts itself.

That matters now because the timeline is getting close. Tesla says it has removed the Model S and X lines at Fremont and is installing the first Optimus lines, "with anticipated production later this year". In mid-September, Tesla teams began auditing parts suppliers in eastern China, according to Chinese media reports summarized by CnEVPost. The questions are no longer about demos. They're about who makes the motors, screws, gears, sensors and chips, and how many of them can be made.

What follows is a parts list in plain language, built from Tesla's own disclosures where they exist. Where the information comes from analysts or Chinese media reports and Tesla hasn't confirmed it, we say so.

The skeleton: 28 actuators doing the work of muscles

An actuator is the part that moves a joint. It's a motor paired with a gearbox or screw, plus sensors that report position and force. When Tesla first showed Optimus at AI Day in September 2022, it said the body used 28 structural actuators that Tesla designs itself, narrowed down to six types to keep manufacturing simple.

There are two main kinds, according to supply chain trackers working from Tesla's AI Day presentation. About 14 are rotary actuators, which twist a joint such as a shoulder or hip and use a harmonic reducer. The other 14 to 16 are linear actuators, which push and pull like a piston in the knees, elbows and wrists and use planetary roller screws.

A harmonic reducer (also called a strain wave gear) uses a flexible toothed ring to turn a fast, weak motor into a slow, strong joint with almost no slack. A planetary roller screw changes spinning motion into straight-line motion. Its threaded rollers spread the load across many contact points, so it can take the jolts of walking better than a ball screw.

Both parts are machined to fine tolerances, and only a handful of factories make them in volume. That's the first bottleneck.

Who makes the gears and screws

On harmonic reducers, the established leader is Japan's Harmonic Drive Systems (6324.T). Industry tracker Humanoid.guide reports that Tesla's reducers are split between Harmonic Drive Systems and China's Leaderdrive (688017.SS), which sells under the name Green Harmonic. Neither Tesla nor the companies has publicly confirmed that split.

Humanoid demand is starting to show up in Harmonic Drive's numbers. In August the company said first-quarter orders jumped 56% from a year earlier to ¥24.1 billion (around US$162.8 million). Orders it files under AI robotics came to ¥1.25 billion (roughly US$8.4 million), more than double what analysts expected, and it raised its full-year operating profit forecast to ¥8.5 billion (US$57.4 million). That robotics figure is still small next to its industrial robot and chip equipment business. It's an early signal, not a new core business.

Planetary roller screws are a tighter squeeze. Humanoid.guide reports that Tesla's first screws came from GSA, the Swiss company behind the Rollvis brand. It says Chinese makers including Xinjian Transmission, Beite Technology and Wuzhou Xinchun (603667.SS) are qualifying as alternatives. Tesla has confirmed none of these names.

Price is why the shift matters. The same tracker says Chinese reducers sell for 40% to 60% of Japanese prices and Chinese roller screws for roughly half of Swiss ones. It also cites analysts quoted by Chinese outlet 36Kr who estimate that Optimus would cost about $131,000 to build without Chinese suppliers, compared with $46,000 with them. Treat that as an analyst estimate. Tesla hasn't published a bill of materials.

Who builds the finished joints

Tesla designs the actuators itself, but Chinese press reports say it's turning to auto suppliers it already knows well to produce them. The names that come up most often are Sanhua Intelligent Controls (002050.SZ, 2050.HK), Tuopu Group (601689.SS) and Joyson Electronics (600699.SS).

The September audits are the clearest sign yet. According to Chinese outlets The Paper and 21jingji, as summarized by CnEVPost, a Tesla team arrived in Ningbo on September 16 and began mass-production audits the next day. The reports name Tuopu, Sanhua and Joyson as suppliers of joint modules, actuators and precision structural parts. Those are press reports citing unnamed sources, not company statements.

This part of the market has a record of getting ahead of itself, so read the reports with care. In October 2025, an unconfirmed Chinese report said Tesla had ordered 5 billion yuan (approx. US$685 million) of linear actuators from Sanhua. Sanhua's shares jumped 10% in Shenzhen and 13% in Hong Kong. The next day the company said it had "no material information that warrants disclosure," and the Hong Kong shares fell about 5% that morning.

The hands are the hardest part

If the joints are the bottleneck, the hands are the hardest engineering problem. Musk told investors in January 2025 that Tesla had tried off-the-shelf motors, actuators and sensors, and that "nothing worked for a human robot hand at any price".

The hands have changed a lot. Tesla's Gen 2 robot, shown in December 2023, had 11 degrees of freedom per hand (11 separate ways the fingers can move) and touch sensors on every finger. Its demo showed the robot picking up an egg without crushing it. Tesla described those sensors and actuators as its own designs and named no supplier.

Tesla hasn't published specs for the next hand. On the July call, Musk said the goal is a hand at least as dexterous as a person's. Third-party reports describe a 22-degree-of-freedom hand with its motors moved into the forearm and tendons pulling the fingers. Tesla hasn't formally unveiled it, so we're treating those details as unconfirmed.

The tactile sensors in the fingertips are the least visible part of the chain. Several supplier names circulate in Chinese industry listings, but we could not confirm any with Tesla or the companies.

The magnet problem

Every one of those actuators needs a motor, and the motors use permanent magnets. The strongest ones are neodymium-iron-boron magnets, often with dysprosium or terbium added so they hold up under heat.

That's where China has the upper hand. Mining Technology reports that China produced about 69% of the world's mined rare earths in 2025 and does up to 90% of the refining. In April 2025, Beijing began requiring export licenses for seven medium and heavy rare earths, including dysprosium and terbium.

Optimus felt it right away. On Tesla's April 2025 earnings call, Musk said "Optimus was affected," explaining that the robot's arm actuators rely on permanent magnets. Reuters reported that Tesla was seeking a Chinese export license and that Musk said Beijing wanted assurances the magnets wouldn't go to military use. "They're just going into a humanoid robot," he said.

The next date to watch is November 10. A broader set of controls China announced in October 2025 was suspended for a year after a U.S.-China truce, and that suspension expires then. The April 2025 licensing rules were never suspended. Beijing could extend the pause, bring back some of the controls or reinstate all of them.

For a product Tesla wants to build by the million, that makes the magnet supply a political risk as much as a manufacturing one.

Battery and brain: the parts Tesla already knows

The two parts Tesla is most at home with are the battery and the computer. At AI Day, Tesla described a 2.3 kWh pack in the torso, sized for a full day's work. It said the robot draws about 100 watts at rest and about 500 watts walking briskly. Tesla hasn't said which cells the current robot uses or who supplies them.

The brain is a Tesla chip, the same family that runs Full Self-Driving in its cars. That puts Optimus in line for the same foundries as Tesla's vehicles. Musk said in July that AI5, the next chip, should reach volume production around the middle of next year and will go into Optimus first.

AI5 is being made by both TSMC (TSM) and Samsung Electronics (005930.KS). Musk has said only samples and small runs would come in 2026, with high volume in 2027. Samsung also has a $16.5 billion contract, signed in July 2025 and running through 2033, to make the following chip, AI6, at its plant in Taylor, Texas. Musk called that figure "just the bare minimum". Tesla also says it's building its own semiconductor fab in Austin.

What to watch, and what has slipped before

Tesla's timelines for this robot have moved before. In 2022 Musk put the price at under $20,000. Tesla's July update made the Fremont start date less precise, saying only "later this year". Musk has also warned that Optimus will be the hardest product Tesla has ever had to scale, since every part of it is new. He said a later Optimus 4, built in Austin, would use a "much more vertically integrated supply system". That suggests Tesla wants to bring more of these parts in-house over time.

Three dates to watch:

• Late October: Tesla's third-quarter results, the next chance for an update on Fremont production and any reveal of the next robot.
• November 5: Harmonic Drive Systems reports earnings, a read on whether humanoid orders are still growing.
• November 10: China's suspension of its October 2025 rare earth controls expires unless Beijing extends it.

The robot will be judged on what it can do. Whether Tesla can build many of them will depend on gear factories in Japan, screw makers in Zhejiang and magnet export licenses in Beijing.

If you were running Tesla's supply chain, which part would worry you most: the magnets, the screws or the hands?