Ten points to powder coating

This article offers a brief overview of several aspects that should not be overlooked when designing and operating a powder coating plant.

  1. Item
    • The material must safely withstand the curing temperature (min. 160ºC)
    • Spatially free, not connected to the ground or to materials not complying with (a)
    • Dimensionally adequate – operating costs increase significantly with furnace size
    • Reasonable in weight, with less heat capacity, rather thin-walled
    • Form-fitting, without deep blind cavities, structurally adapted
  2. Handling
    • Manual between processes or on a handling trolley, rotating devices
    • Hand-held overhead conveyor and marshalling equipment, as a reservoir, ground special
    • On conveyor with continuous or clocked feed
    • Suspension method, hanger design, mechanical and chemical maintenance
    • Binding, masking and blanking consumables
  3. Preparation
    • It is based on the stresses of the environment for which it is adapted – indoor or outdoor
    • Mechanical – grinding, polishing, plastering, blasting (hard, soft)
    • Chemical and electrochemical, by dipping and spraying (pressure), rinsing and drying
    • Drain holes from cavities, wear and contamination of blasting materials
    • Ecology, liquidity – product degradability, cleaning, fumes, wash tables
  4. Area
    • Dedicated to splashed dust, extracted for safety and hygiene reasons
    • Booths are entered / sprayed from outside – protective equipment always
    • Splashes are captured for reuse (reclaimed), structures to waste
    • Dust separation from air on filter / dynamic separation – cyclonic
    • Handling mechanisms separately inside the paint shop / integrated into the unit
  5. Technology
    • Designed to charge (electrify) powder, transport charged particles to the object
    • According to charging: by friction – TRIBO system / high intensity field – STATIC
    • By method of spraying: by human hand – manual / clamped in holder – automatic
    • Support mechanisms: hoppers, pumps, manipulators, control cabinets
  6. Spraying
    • Start at the most difficult to reach places of the course
    • On a mechanised workstation, prespray first, then external ignition
    • Manual cross-spraying, ringing, optimum spacing, traces
    • Automatic spraying by spray wall, robot or manipulator
    • Overall efficiency, adequate pressure (power), abrasiveness (Al2O3), wear
  7. Air
    • Adjustment to be carried out just before the application area and application technique
    • Free of water (frozen), oil and mechanical impurities (oil and dust filters)
    • Stabilized in an air tank of sufficient volume, suitable compressor (screw)
    • Manifolds graded with skimmers, clearance, pressure drop, pressure required
  8. Curing
    • Furnace sufficiently rated, speed of rise of hardening temperature
    • Temperature fluctuations (leaks) and homogeneity of temperature field (structures, effects)
    • Exposure (time) of curing is calculated only after reaching the recommended temperature (more)
    • Point a) is affected by the mass of the charge, leakage from the surface (insulation), volume
    • Source: electricity, gas, oil – direct and indirect heating, air circulation
  9. Measurements
    • Coating – thickness gauges, reflective gloss gauges, comparative stencils
    • Adhesion – destructive testing by grid, tape tear, impact
    • Electrical strength – spark source HV
    • Durability – chemical tests – salt chamber
    • Powder electrification (REGTEST), leakage resistance and earthing (TESOR)
  10. Safety
    • Reduction of explosion risk by permanent cleaning of the spraying area and surroundings
    • Continuous control of grounding of goods, guns and metal within 6m of the spray
    • Lighting of spray area, shoes, clothing, no gloves, static floor
    • Spray blocking in case of insufficient suction, lights and sockets with cover
    • Control of ignition signalling device, in operation clean, blowdown
    • Check of fire extinguishing equipment, extinguishing media cartridges
    • No smoking and handling of open flames, welding and cutting.

Ing. Josef Ježek
The text was compiled for the training organized in cooperation with ČVUT: 2012/04