Some degree of vibration is inherent to any industrial robot: moving articulated masses always produce residual oscillation. The issue arises when that vibration changes in character — it grows in amplitude, appears on paths where it previously did not exist, produces new audible noise, or causes visible tool oscillation. Any such change is a symptom that deserves prompt attention.
Why early detection matters
A robot vibrating excessively does not only affect process quality (welding, dispensing, machining). It also accelerates wear on the very components generating the vibration, creating a vicious cycle. What is an annoying noise today can become a seized gearbox or a damaged encoder within weeks. Early diagnosis dramatically reduces repair cost and downtime.
Mechanical vs. electrical origin: the first distinction
Before looking for a specific cause, it helps to determine whether the vibration is mechanical (transmission, gearboxes, bearings, tool flange) or electrical/control-related (servo PID tuning, encoder, motor cabling). A practical way to orient yourself:
- Mechanical vibration: tends to be coarser (low frequency), persistent during movement, and audible even at low speeds. Often accompanied by perceptible backlash when manually moving the affected axis.
- Electrical/servo vibration: tends to appear as a fine, rapid tremor, especially when holding position, or as oscillation during deceleration. It may diminish when the regulator gain is reduced.
This initial distinction guides whether the problem lies in mechanical components or controller configuration, and avoids unnecessary part replacements.
Most common mechanical causes
Worn or damaged gearboxes
Precision reducers (cycloidal or harmonic drive) are the components most exposed to progressive wear. As internal backlash increases, the robot not only vibrates but also loses repeatability. A classic sign is vibration that only appears within certain speed or position ranges, because backlash varies with load and angle.
Degraded bearings
A bearing with a damaged race generates a characteristic vibration at a frequency proportional to the rotation speed. If the noise resembles a periodic crunch or click that changes with axis speed, bearings are the primary suspects. Contaminated oil or grease accelerates this degradation, which is why following a proper lubrication programme is so important.
Play in the tool flange or tooling
Not all vibration originates inside the robot. A poorly secured tool, a badly routed dress pack, or an additional mass installed without recalculating the dynamic load can produce oscillations that appear to come from within. Before any disassembly, physically check the tool-wrist assembly.
Electrical and control causes
Encoders with degraded signal
An encoder returning an intermittent or noisy signal causes the servo regulator to continuously attempt to correct what it perceives as a position error. The visible result is a tremor on the affected axis, even at rest. In ABB, KUKA and FANUC robots, the controller's diagnostic logs can reveal encoder signal irregularities before a hard stop alarm is triggered.
Mistuned servo gains
After a repair, a gearbox replacement or even a software update, the servo PID parameters may not be optimal for the actual load conditions. An excessively high proportional gain produces sustained oscillation; an excessive integral term causes overshoot on deceleration. Gain tuning is specialist work, but identifying the symptom — vibration that worsens with load or during braking — points the diagnosis in the right direction.
Deteriorated motor cabling
Cables running through the robot arm undergo continuous flexing. A partial break in a power conductor or feedback wire can cause disturbances that the servo interprets as position error. Inspecting the condition of the internal cabling is a diagnostic step to complete before replacing more expensive components.
Practical steps before calling the technician
- Isolate the axis: move each axis separately in manual mode (T1/T2) at reduced speed to identify which one vibrates.
- Vary the speed: check whether vibration is constant or only appears at certain speed percentages (mechanical indicator) or only when stationary (servo indicator).
- Check the load: remove the tool if possible. If the vibration disappears, the problem is in the tooling or the load configuration in the program.
- Review the controller logs: look for warnings or minor errors that have been recorded even if they did not stop the robot.
- Note when it started: after a collision? After a program change? Progressively? This information speeds up the technical diagnosis.
If the diagnosis points to internal components, our corrective maintenance team can intervene with ABB, KUKA and FANUC spare parts in stock, minimising downtime.
When to act immediately
Some situations require an immediate stop rather than waiting for the next planned maintenance window: when the vibration is accompanied by metallic knocking, when the robot loses repeatability noticeably, when path-following alarms appear, or when vibration has grown progressively worse over days. Continuing production under those conditions risks far more costly secondary damage.
For ABB robots, specialist diagnosis is available through our ABB maintenance service. For KUKA and FANUC fleets, see our KUKA maintenance and FANUC maintenance pages.