Electrostatic coating needs the part held at earth potential, and the usual safety requirement is 1 megohm or less from part to ground. Cured powder on hooks and racks is an insulator, so contact points build up resistance with every pass. Poor ground lowers transfer efficiency, causes uneven film, increases back ionization and can let a part hold a charge that sparks and ignites a powder cloud.
Meg the hooks before we start, ground has been sketchy all week on line two.
A cheap ohmmeter check on a few hooks at shift start finds more coating problems than any gun adjustment.
Also heard as
- grounding
- earth
Related terms
Bad ground
A hook or rack contact too crusted with cured powder to carry charge away, so powder will not stick properly.
Hooks
The wire hangers that hold parts on the conveyor and carry the ground connection.
Transfer efficiency
The share of sprayed powder that ends up on the part rather than in the booth.
Burn-off oven
A high-temperature oven that burns cured powder off racks, hooks and rejected parts.