Roller coating machine for UV coating.

Roller coating machine is the most appropriate machine for the application of UV coatings. Although theoretically the UV coating can be applied by spray, but until now it is always applied by roller coating machine. The curing of the UV coating that requires UV lamp with certain intensity make the  spray applications becomes very difficult. The low efficiency  of the spray application (30%-60%) which is much lower compared with the roller application (about 90 %) has made the roller application is the only choice for the UV coating. Since it cannot to be used for the shape form, then the UV coating is limited to be used for the flat panels. The shaped, curved and complicated objects which only can be finish by spray, are finished with other finishing material. The PU or AC or NC can be used to finishing on the curved part, while the flat surfaces such as top panel, side wall panel can be finished by UV coating.
The roller machine now also has been improved lot. There are many models and variation of the machine has been developed to meet the current needs from the finishing process. There two important  tool in the roller coating machine, the roller and the oven. In the flat finishing line the UV oven lamp are always installed after the roller. The UV oven lamp is used to cure the UV coating that was applied by the roller. In the UV coating finishing process, the water based stain is mostly used as the first step. The water based stain need heat oven to facilitate its drying. So in the first  roller, the sponge roller is used to apply the stain then followed with the heat oven. Then at the next step the rubber roller and the UV lamp oven is used to apply the UV finishing material (UV filler, UV sealer or UV top coat ). In the line there could be some brush sander or wide belt sander are mounted to do the sanding process if necessary.

Roller coater
 

Roller coater is the device used to coat and layer the UV coating to the surface. It works with the same principe with the roller to apply the wall paint, but it work automatically to do the finishing process for wood panel.The roller is wet with the paint and rotating automatically with constant speed, while the wood panel are inserted to be layered with the paint. It is very similar with the roller coater for water based coating, but with different type of roller and oven are used.

There are several types of rollers that can be used in a roller coater machine; sponge roller, rubber roller, steel roller and laser roller.

•  Sponge roller

The sponge roller is the roller with the highest flexibility. Sponge roller is widely used to apply the water based coating. In the UV finish, the sponge roller is used to apply the water based stain at the first step in UV finishing system. Sponge roller is also used to layer the UV sealer on the uneven surface panels such as the hand scraped (distressed) wood flooring panels. The sponge roller has high flexibility so it can accept the slightly bumpy and the uneven surface. But for the flat surface it will produce coating layer with more roller mark.

• Rubber roller

Rubber roller is the most widely roller to apply the UV coating. UV sealer, UV filler, putty and UV top coat are usually applied with rubber roller. Rubber rollers has some hardness sizes that is described with the rubber shore. The application of UV sealer, UV filler and UV putty are usually done by the softer rubber roller (20-40 shore). While the UV top coat is applied with the harder rubber roller (40-50 shore).

• UV laser roller

It  is a special roller for application the UV laser coat. The UV laser roller may superimposing the finishing materials with higher thickness in one application. UV laser coating is designed to produce better flow coating layer better then the conventional UV coating. The UV laser coater is needed at the final coat to apply the UV laser coat to produce more flat and smooth coating film.

• Steel roller.

The steel roller is only used in the application of filler and putty. Steel roller is mounted after the rubber roller or sponge rollers before the UV lamp oven. Steel roller serves to press the filler or putty  into the pores and grain and simultaneously reducing the excess wood filler on the surface.

• Wide belt sander or brush sander

Wide belt sander is usually installed in a series of flat line roller machine to do the sanding process. The UV sealer some time need to be sanded and it should be done automatically by the wide belt sander in the machine line. Sometimes the  wide belt sander is replaced with the brush sander. The brush sander is required to do the scuff sanding. Brush sander is used when the uneven flat surface is finished such as in the hands scrapped (distressed finish).

• UV curing lamp

The UV curing lamp is the device to provide UV light in some intensity.  The UV light radiation is danger, it  causes cancer if irradiate the human skin. The UV oven lamp is always placed in the close box. Since that the UV oven lamp only accept the flat panel form, the UV oven  to the big and curved form stuff will be very expensive. It is the main reason why the UV coating is only used for the flat panel. 

UV roller coating roller machine

There are 2 type of UV cured lamp. The Hg lamp and the Ga lamp. The Hg lamp is the most used, it is relatively less expensive and work for most UV coating. The Ga lamp is used when the coating layer is thick or need the better UV radiation light. It will help to better curing since it can deep penetrate into the coating better than the Hg lamp. It is used for some cases when the UV coating need better curing, for example the UV white base coat, or UV coating with thick film coating.