ESD Control for AMR in Electronics and Semiconductor Factories: Tires, Grounding, Surfaces, and Verification

In electronics and semiconductor manufacturing, electrostatic discharge (ESD) can damage sensitive components. When mobile robots operate in these environments, they do not just “pass through” — they can become static generators, accumulators, and discharge paths.

Three roles AMRs play in the ESD path:

1. Static generator: Tire-to-floor friction generates static — the more the robot moves, the more accumulates.
2. Static carrier: Without an effective grounding path, static accumulates on the robot body.
3. Discharge path: When the robot contacts the payload (electronic components, wafer carriers), accumulated static may discharge through the payload — damaging components.

ESD control is not “does the robot have ESD certification?” — it is “under your floor, your payload, and your ESD control plan, can static be effectively dissipated?”

Conductive and Dissipative Tires

Tire role in ESD control: Tires are the primary contact between robot and floor — if tires are conductive or dissipative, static can dissipate through the tire-to-floor path.

Tire types:

Specific resistance ranges for each category are defined by IEC 61340 and ANSI/ESD S20.20. The acceptable range for your application depends on your ESD control plan — do not assume a universal value.

Confirm AMR tire surface resistance matches your ESD control plan. If the supplier uses standard industrial tires (typically insulative), they need replacement with ESD-compatible tires.

Impact of tire replacement: ESD tires may have different load capacity, wear resistance, and floor friendliness — confirm that ESD tire replacement does not affect payload and motion performance.

Chassis Grounding and Equipotential Bonding

Grounding path: Static flows from the generation point (tire-floor friction) → wheel hub → bearing → chassis frame → payload contact surface → payload. Any break in this path causes static accumulation.

Equipotential bonding: Ensure electrical continuity between robot metal parts — if the chassis frame and payload contact surface are not connected, static cannot flow from the generation point to the dissipation point.

Verification methods:

• Measure tire surface to chassis frame resistance — confirm path continuity.
• Measure chassis frame to payload contact surface resistance — confirm path continuity.
• Measure payload contact surface to payload resistance — confirm effective contact.

Common breaks:

• Bearings using insulating material → tire-to-chassis break.
• Insulating layer between module and chassis mounting surface → chassis-to-payload break.
• Coating or paint forming an insulating layer between metal contact surfaces.

Ask the supplier for an ESD grounding path diagram — the complete path from tire to payload contact surface. If there are breaks, confirm whether bonding jumpers are used.

Top Modules, Pallets, and Payload Contact Materials

The robot surface contacting the payload is the last link in the ESD path — if the contact surface is insulative, even with good chassis grounding, the payload may still be charged.

Payload contact surface requirements:

• Contact surface material needs to be dissipative — per your ESD control plan’s specified resistance range.
• Contact surface needs equipotential bonding with the chassis — otherwise static cannot dissipate from payload to floor.
• Pallets and totes contacting the robot also need ESD compatibility.

Common problems:

• Standard deck uses insulative plastic → contact surface break.
• Pallets use standard plastic → payload-to-pallet insulation.
• Top module mounting surface has insulating pad → module-to-chassis break.

Confirm ESD properties of all payload-contacting surface materials. If using third-party pallets or totes, confirm their ESD compatibility.

Floor Resistance and Route Continuity

Floor role in the ESD path: If tires are ESD-compatible but the floor is insulative (e.g., standard epoxy), static cannot dissipate through the tire-floor path.

Floor resistance requirements: ESD control floors require specific resistance ranges per your ESD control plan. Standard industrial floors may have resistance far exceeding the dissipative range. The acceptable resistance and charge-control behavior must be defined by the site ESD control program and verified as a complete system; do not infer a universal safe range from the AMR alone.

Route continuity: If the route passes through different floor types (e.g., ESD floor and standard floor boundary), the ESD path breaks at the standard floor section — static dissipates on ESD floor sections but accumulates on standard floor sections.

Measure floor resistance along the entire AMR route. If the route has resistance discontinuities, route discontinuity requires ESD-engineer assessment and an approved control measure.

Sensors, Electronics, and ESD Maintenance After Wheel Replacement

Sensor windows: If sensor windows are insulative material (glass/plastic), they may accumulate static. In ESD-sensitive environments, confirm whether sensor window ESD properties require specific treatment — this must be assessed per the site ESD control program and the specific device evidence, not assumed.

Wheel replacement: After replacing tires, new tires’ ESD properties may differ — verify new tire surface resistance and grounding path continuity.

Post-maintenance ESD verification: Any maintenance involving wheels, chassis, modules, or payload contact surfaces requires re-verification of the ESD path.

How to Verify ESD Performance on Real Routes

Verification methods:

1. Use an electrostatic voltmeter to measure robot surface voltage before and after operation — confirm static is not excessively accumulating.
2. Measure tire → chassis → payload contact surface resistance — confirm path continuity.
3. Measure floor resistance — confirm floor ESD properties.
4. Run under actual payload conditions — measure payload contact surface static voltage.
5. Test at different speeds and loads — higher speed means more friction and more static.

Verification frequency:

• Full verification at initial deployment.
• Re-verify after wheel replacement.
• Re-verify after floor maintenance.
• Periodic review per your ESD control plan.

ESD Acceptance Checklist

ESD Path Verification Inputs

1. AMR is part of the ESD path — not just “passing through” but potentially a static generator and discharge path.
2. Tires are the first link in the ESD path — confirm conductive or dissipative tires matching your ESD control plan.
3. The grounding path needs end-to-end continuity — tire → chassis → payload contact surface → payload; any break causes accumulation.
4. Payload contact surface material is easily overlooked — standard decks and pallets may be insulative; ESD-compatible materials are needed.
5. Floor resistance determines whether the ESD path is effective — ESD-compatible tires but insulative floor means static still cannot dissipate.
6. Re-verify the ESD path after maintenance — tire or module changes may break the grounding path.
7. Specific resistance requirements come from your ESD control plan — do not assume universal values.