Tunnel Type Electrostatic Powder Coating System

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Tunnel Type Electrostatic Powder Coating System

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How the line works

In a tunnel type plant the part is hung on the conveyor and passes without stopping through pretreatment, drying, the coating booth and the curing oven. The operator stands only at the loading and unloading point; every step in between moves at line speed. Conveyor speed is adjustable between 1 and 6 m/min and that speed sets capacity directly. The plant is configured for 500–5,000 parts per hour; where you land in that band depends on part size and hanger spacing.

Pretreatment is part of the line

Powder will not adhere to a surface left with oil or rust; the defect appears after the oven and the part is reworked at that point. Pretreatment is therefore an inseparable part of the line and is built with 3 to 7 stages, using phosphate or chrome based chemistry. Two things set the stage count: how contaminated the parts are and the corrosion resistance required. If you export, the chemical regulations of your target market also influence the choice; this is why chrome-free systems are often preferred.

Booth and recovery

The booth can be built as a filter or cyclone type. Coating efficiency is 98.5% and above; powder that the booth fails to retain is a direct cost, because unrecovered material goes to waste. Cyclone systems are preferred where colour changes are frequent, because colour change time is capacity itself: every minute the line stops is a minute not producing. Booth size and gun count are calculated together with part surface area and the target line speed.

Energy choice and commissioning

The oven is manufactured in a gas or electric version. The choice follows the infrastructure at the installation site and local energy prices; the longer the daily running hours, the greater the gas advantage. Because the plant is custom built, the schedule depends on the project and the exact date is stated in the quotation. In practice the critical path is usually not machine manufacturing but infrastructure processes such as the gas subscription and the electrical capacity upgrade. The product carries a 2-year manufacturer warranty.

Theoretical capacity versus real capacity

The capacity on paper and your actual monthly output are not the same. Subtract colour changes, shift-start heat-up, breakdowns and maintenance stops and real output is lower. A plant that bases its investment case on theoretical capacity overestimates monthly revenue and miscalculates payback. This is why we ask for your daily target in m² or parts when designing: the line is sized to that target with a realistic allowance.

Technical Specifications

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