Challenge
An MRO moves sensitive avionics on tool carts between ESD-controlled bays and ordinary floor zones. Standard polyurethane casters let the cart build up static in transit, and the QA team is chasing intermittent component damage it cannot tie to a handling error.
Solution
Trace the path the components travel through the facility, then specify conductive casters (tread, bearing and housing) so the cart has a path to ground, with one part number across the whole cart fleet.
What typically changes
What typically changes — the cart stops being the weak link between ESD-controlled areas, and one conductive caster SKU replaces a mix of lookalikes. The resistance rating comes from the manufacturer for each SKU; results vary by facility.
Illustrative scenario. This page describes a typical situation and the way Douglas specifies for it. It is not an account of a specific customer, and it contains no customer figures or quotes.
Background
Miami’s aerospace cluster — MIA-adjacent MRO facilities, avionics shops and supply-chain operations — maintains commercial and business aircraft from across the Americas. In a typical avionics MRO, tool carts move between component benches, ESD-controlled bays and shipping/receiving, carrying expensive, static-sensitive components on every trip.
The Specification Problem
The pattern QA teams describe: components that arrive working read as damaged at the test bench, and the failure mode does not match the original removal. Handling errors get blamed first. When the failures cluster in dry months and along certain transport routes, the investigation usually finds:
- Standard polyurethane casters let the cart build up static as it rolls across non-ESD floor zones
- The cart discharges through the components or the frame as it crosses between bays
- The charge transfer happens before the parts reach the ESD-controlled work area
- Bench mats cannot protect parts in transit
What Douglas Specs
Working from the facility’s own ESD control program (which sets the resistance requirement), Douglas specifies:
Conductive caster construction
- Conductive polyurethane tread, with the resistance range stated by the manufacturer for the SKU
- Conductive bearing pack
- Aluminum housing instead of powder-coated steel
- A continuous path from floor through caster to cart frame
Sized for the application
- 5-inch wheel for smooth rolling over floor transitions
- Sealed precision bearings — no grease ingress, long maintenance interval
- Total-lock brake for workstation positioning
Single-spec retrofit
- The same caster on every cart (no mixed inventory)
- One part number for purchasing and for maintenance
Why This Approach Works
- Root-cause analysis. Ask about the path the components take through the facility — not just “what cart do you need?” The static problem is a movement-path problem, not a workstation problem.
- Single-spec standardization. One conductive SKU removes the risk of someone replacing a worn caster with a non-conductive lookalike.
About this page: an illustrative scenario built from the kind of application Douglas specifies for in South Florida aerospace. Conductivity and resistance ratings come from the manufacturer for each SKU; your ESD coordinator sets the requirement. Call (305) 888-3700 to talk through your carts.
Products Used
- Colson conductive swivel casters
- 5-inch conductive polyurethane tread
- Sealed precision bearings
- Aluminum housing
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