Hello experts,
I need some clarification regarding grounding for machine mechanisms. Based on my understanding, the requirement for Grounding/Equipotential Bonding per ANSI/ESD S6.1 is < 1.0 Ω AC impedance. In my case, the machine’s main grounding points meet this specification. However, I’ve noticed that several moving or dynamic components cannot achieve <1 Ω. Their readings are typically below 20 Ω. Some parts can be improved by adding auxiliary grounding cables to internal ground points, but others—such as rotating chuck tables or high-speed sawing blades—are difficult to ground effectively due to their motion.
My question is: Is there any ESD risk if moving mechanisms remain >1 Ω but <20 Ω, assuming these components are conductive? Do these moving parts also need to meet the <1 Ω requirement, especially components that make contact with the product—such as porous chuck tables during cutting?
In our process, PCBs may carry residual charge from previous steps. We reduce this by using ionizers before the next process, but is there still a risk if a PCB contacts machine parts that have >1 Ω grounding? To evaluate this, I performed tests for ESD events during PCB placement and removal on the chuck table, and the results showed no events.