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PAINTING PLANTS

VERTICAL FOR ALUMINIUM PROFILES WITH OFB DISK

The vertical painting systems for aluminium profiles using the OFB5 disk represent the most advanced evolution of Trasmetal electrostatic technology. It is based on and further improves the general architecture of the previous versions, with more high-voltage generators, each of which manages a series of electrodes that cover the entire disk circumference.

 

OFB5 is equipped with two separate air circuits, one for feeding the fluidised bed, while the other is an auxiliary circuit for continuous electrode cleansing and for supporting air/ powder mixture emission. The most important innovation, subject of a new patent request dated 2005, consists of the new solution adopted for the ionisation systems which, thanks to the particular geometry of the electrodes, allows the homogenization and maximising of the powder’s charge effect an instant before it is sent through the slots of the disk.

 

An extremely high electrostatic efficiency is reached, maximising the consistency of the layer already obtained with the previous generation of disks, while also improving extension and penetration. What is more, the most important practical result of the new OFB5 technology consists of the possibility of the new disk to use not only standard RAL powders (already achieved), but also special powders (metallised, veined, embossed, marbled, etc) without the need of selected granulometry, with advantages (both for powder producers and for users) for small lots of colour.

OTHER ELECTROSTATIC EQUIPMENT

The methods for applying powder enamels are based on different principles, and the choice must be made depending on the single needs of each Customer, which may include:

 

  • The characteristics of the finished products;

  • The type of powder used;

  • The thickness of the film;

  • The amount of finished product to produce;

  • The number of colours to apply;

  • The type of application (manual or automatic);

  • The space available

  • The ability of the devices to respond to immediate and future needs

 

Trasmetal, in addition to having developed and patented its own powder enamel application system destined to aluminium profile painting (OFB), is also able to supply systems with any method of application:

 

  • by fluidised bed (the first method used industrially)

  • by electrostatic fluidised bed

  • by electrostatic spray guns

BY SPRYING

The main elements of a painting system are the paint application booths. Besides being designed to allow optimum painting, they must also guarantee a healthy working environment, both in the painting area as well as in the departments nearby.In addition to guaranteeing internal safety, the booth must be built so to minimise outgoing pollution, while at the same time maintaining adequate working parameters (temperature, humidity, etc) and filtering external air as well. It must also allow simple maintenance, fundamental for guaranteeing efficiency.

 

On the basis of this philosophy, Trasmetal is able to supply:

 

1 - Depending on the dimensions and weight of the workpieces to be painted:

 

  • Open painting booths

 

  • Closed painting booths (pressurised or compensated)

 

  • Large painting booths (for workpieces with large overall dimensions, ex. aeronautical sector)

 

  • Painting booths with electrostatic disk (in which the painting substance, electrostatically charged, is projected on the workpieces to be painted by means of a high speed disk rotating around its vertical axis. The system is particularly fit for cylindrical bodies or for workpieces with similar plan dimensions).

 

2 - Depending on the type of overspray filtering:

 

  • Painting booths equipped with dry abatement;

 

  • Painting booths equipped with water film or with “venturi” abatement.

BY ELECTRODEPOSITION

Particularly important for Trasmetal was the development of electrophoresis technologies (“anaphoresis”, in which the workpiece represents the negative pole and “cataphoresis” in which the workpiece represents the positive pole).

Similarly to immersion tanks, the parts are completely immersed in a tank containing paint diluted with water. Continuous electrical current is sent to the tank. The painting product deposits on the workpiece, which acts as one of the two electrodes, while the water soluble-resin is discharged on the other electrode and eliminated. Upon exiting the tank, the substance deposited on the workpiece is already insoluble; it therefore undergoes washing (inside a post-electrophoresis tunnel in order to remove and recover the small amounts of substances that are dragged mechanically. As with the immersion tanks, the workpiece enters a furnace where the painting product reticulates.

Differently from immersion tanks where the workpieces on the same line may have different dimensions and shapes, during electrophoresis is preferable that the workpieces to be painted has the same or only slightly different shapes and dimensions in order to avoid distortions in the electrical field.
Electrodeposition allows a uniform coating with a thin film and excellent resistance to corrosion. Though frequently used as a substrate on many products (automotive industry, auto components, household appliances, agricultural machinery and more besides), it can be increasingly often applied as the single finishing coat (pumps, lighting bodies)

BY IMMERSION

Immersion painting usually makes use of resins dissolved in water.

During immersion painting workpieces are completely immersed in a tank containing the product to be applied. When exiting the tank the dripping workpiece is still flowing, and it is re-immersed into the tank. The workpieces then enter a furnace where the painting product reticulates.

This system is used almost exclusively for assembly-line industrial painting, and can be used even when the workpieces on the same line have different shapes or dimensions. The workpiece, without air bells, is painted on internal parts as well, as in the case of pipes or radiators

FLOW COATING

In this technique, application is done by going through a calibrated cascade of paint that flows over the workpieces.

The thickness of the film depends on the inclination angle of the workpiece, on the viscosity of the paint and on the amount of evaporating solvent.
The excess paint is recovered in a collection tank and put back into circulation.

In some cases, flow coating avoids the air bells problem.

Trasmetal has applied the flow coating technology to the automotive sector (on lenses and parabolic reflectors for headlights), where paint is applied in a cleanroom and then polymerised with UV radiation and, and to the enamelling sector, in the flue and washing fields

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