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