Euroimpianti

It is well known that the coating of a product is normally vital and that a good product con be depreciated by a bad finish, just as a poor product can be improved, at least on the surface, by a good coating.

Much attention should be given to the properties required form a coating, such as adhesion to the substrate and resistance to abrasion, corrosion and moisture. The mechanical properties, such as the scratch and impact resistance, as well as the resistance to chemicals, (solvents, oils, hydraulic fluids, etc.) are important too.

Ultimately, the coating enables a product to perform the function for which it was designed. Sometimes, the industry tends not to take this into due consideration, while, on the contrary, it should be seen as a determining factor. And choosing the right coating technique is even more important.

On the one hand, the attention to the ecological impact and the laws on the disposal of toxic substances and the water treatment are becoming increasingly severe, on the other hand the market requires short production and delivery times.

One of the most commonly used coating techniques, particularly in industry, is the powder coating: the workpieces are painted with a powder coating based on synthetic resins, which adheres due to electrostatic effect, and then placed into an oven where the coating, due to the temperature, first melts and then polymerises, thus resulting in an adherent layer.

 

As with other types of coating, the result in terms of adhesion, durability and corrosion resistance is heavily influenced by the preparation of the surface pre-painting stage. In fact, the coating thickness achievable with this technology is significantly higher than that obtained with liquid coatings (100 micrometres are easily exceeded), while the mechanical characteristics (hardness, elasticity) can be very high.

With a powder coating, it is still possible to achieve a great performance in terms of both finishing, even though the gloss will not be comparable to that obtained with liquid coatings, and of mechanical seal. On eof the problems that the operators of this sector face is the relatively high operating temperature of the furnace and the fact that some components, such as some types of electric motors or other delicate components, do not withstand the high polymerization temperatures. In the past, it was actually impossible to coat these assembled components, which forced the operators to paint only the unassembled components, with all the consequent operational issues, or to implement  other coating techniques.

 

A new polymer power coating technique is being developed in this field. It combines most of the advantages of the traditional powders with the advantages of the liquid polymer coatings. The result is a painting process with a very low environmental impact, which can be used on products with temperature-sensitive internal components. For many manufacturers, this results in the possibility to coat pre-assembled products, directly on the production site. This technology allows to utilize the powder coatings with the supply of UV or IR rays. Although this technique was already widely used for the linear surface treatment, the development of a system that allows to polymerise three-dimensional surfaces and especially three-dimensional surfaces with undercuts is a real innovation.

 

The UV system (patent no. VR2011A38) allows to carry out the polymer powder coating also on three-dimensional objects.

In the first stages, the coating cycle coincides with a traditional cycle of powder pre-treatment and coating. The part to be painted, once washed and prepared, is placed on a conveyor belt and the powder coating is applied electrostatically, so as to provide sufficient coverage in a single step (in manual or automatic mode).

At this point, the product leaves the spray chamber and enters the UV-IR oven. The casting and crosslinking process occurs in two different steps. At first, the IR treatment of the product begins: the temperature of the infrared rays must bring the surface temperature to 90° maximum so the powder can melt and be distributed evenly. Depending on the mass of the workpiece to be treated, the process can last from one to five minutes. Now the product is painted, but not finished yet, as the surface still lacks the necessary characteristics of sealing and fixing. For this reason, it undergoes the treatment of polymerisation under ultraviolet rays at a temperature of about 80° for a few tens of seconds. At this point, the product is finished, but it takes a few minutes before it can be handled: during the cooling stage, the polymerisation continues and the coating is fixed to the substrate. The entire process, including the spraying, can last from 5 to 10 minutes.

 

The use of UV technology allows a company to coat its products with significant and undisputed industrial advantages that neither the liquid nor the powder coating had brought before.

The reduction of the coating time significantly cuts the hourly production cost and the energy consumption. The tests conducted both in the laboratory and on the operating systems show that the process is 2 times faster than the traditional coating with a ratio of 1:3, while the quality is the same.

The first and most immediate consequence is financial. Namely, despite the spread of this powder coating application technology is still low and therefore the price of this consumable material is high, the savings are significant from the point of view of energy consumption and of hours spent for the same job.

The rapid drying and cooling, possible thanks to the low temperatures required for the melting and curing, also make the storage and packaging of the finished product faster, favouring the immediate clearing of the downstream storage space. For this reason, the system is much more compact and occupies less space than a traditional coating line. The possibility to paint the product once already assembled also ensures a higher quality of finish and eliminates the risk to nick the previously treated surface during the production stage.

Compared to the liquid coating, the use of powder coating provides an almost complete reduction of the environmental impact of the production process. In this regard, it will suffice to think how much the disposal costs, be they waste related, due to an outsourced process or attributable to the treatment plant, affect the entire coating process. The UV system has been designed and engineered to eliminate all types of waste, it has no treatment plant and ensures the total reduction of CO2 emissions.

 

Excellent results were obtained on any type of metal or plastic surface. The electric motors, the hydro pneumatic pumps and all the products containing heat-sensitive components are perfectly compatible with th UV powder curing technology.

Euroimpianti is also pleased to offer customers the opportunity to run practical spray tests on items of all sizes using the new generation equipments available in the showroom located in Valeggio sul Mincio (Verona - Italy).