Segment
Robot mechanics: what makes a joint move accurately
A robot arm is a chain of joints, and each joint is a motor, a gear reduction, a brake and a position sensor. The quality of those four determines how heavy a load the arm can carry, how precisely it can place it, and how long it lasts — and two of them come from a very small number of suppliers.
In one sentence
Robot mechanics are the physical components of a manipulator — the actuators and precision reducers at each joint, the sensors that measure position and force, and the tooling at the end of the arm.
A servo motor spins fast with modest torque; a robot joint needs the opposite. A precision reducer converts one into the other with very little backlash — the lost motion when a gear train reverses direction — because backlash at a joint multiplies into position error at the end of the arm, and an arm with a metre of reach amplifies a fraction of a degree into millimetres.
That is why reducers matter more than their share of the bill of materials suggests. They are the component with the highest technical barrier, the longest supplier relationships, and the most concentrated market in the whole machine. Motors and drives are competitive; precision reducers, historically, have not been.
At the other end of the arm sits the gripper or tool, which is where a general-purpose machine becomes a specific application. It is also where most integration effort actually goes, and where a great deal of the automation that does not happen fails to happen.
How this breaks down
Split by what each component contributes: the tolerance underneath everything, the torque, the measurement, and the contact with the work.
- Bearings and precision machiningCrossed-roller bearings, hardened gear steel and the machines that cut them to microns.Definition page
- Actuators and reducersHarmonic and cycloidal gearing, why backlash is the enemy, and the most concentrated market in robotics.Breaks down into: Servo motors · Strain-wave reducers · Cycloidal reducers · Roller screws4 pages belowChokepoint
- Sensors and encodersPosition feedback, absolute versus incremental, and the force sensing that lets a machine touch things.Breaks down into: Position encoders · Force and tactile sensing2 pages below
- End effectorsGrippers, vacuum, tool changers — the cheap part that most integration effort goes into.Definition page
What this depends on
1 of these is marked as a chokepoint: a handful of qualified suppliers, a multi-year lead time, or a single geography.
- Supply chainChokepoint
Rare-earth magnets
Servo motors use permanent magnets from the same constrained supply chain as vehicle traction motors.
Rare-earth magnets - Supply chain
Position feedback devices
A joint that cannot measure its own angle cannot be controlled, and an arm that loses position on power failure cannot be restarted safely.
Position encoders
What depends on this
Other pages in this map that name Mechanics as something they cannot do without.
Companies across Mechanics
Every company named on a step below this page, ordered by how many of those steps it appears at. Compiled from the pages themselves rather than written separately, so the two cannot disagree. Not a ranking and not a recommendation.
- HeidenhainPrivate2 steps
- RenishawLondon2 steps
- SchaefflerGermany2 steps
- SchunkPrivate2 steps
38 more companies appear at a single step each; they are named on the pages for those steps.
How these pages are written
Each page explains one technology in plain language, states what it depends on, and names companies by what they supply at that step. Company roles are described qualitatively and deliberately carry no market shares, revenue figures or rankings — those change faster than an explainer can, and a stale number is worse than none. Ticker links point at company pages on this site and are provided for reference only.
Nothing here is investment advice, a recommendation, or a forecast. A company named on a page about a technology is not thereby a good investment, and the chokepoints described are structural facts about supply chains rather than predictions about prices. Technology moves; where a page describes something as unresolved or in development, that was true when it was written.
Plutux is not an investment adviser. Market data and AI-generated analysis are for information and education only, not investment advice. Disclaimer