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MAIN STAGES AND TECHNOLOGY OF DECORATING

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MAIN STAGES AND TECHNOLOGY OF DECORATING

Starting with fundamental principles of sublimation thermal transfer process, it can be divided into the following stages:

  • creation of polymer coating on product surface;
  • image formation on the intermediate surface;
  • positioning of intermediate surface relative to the decorated surface;
  • ensuring of even and maximum clamp of intermediate surface and printing surface;
  • thermal exposure with maintenance of set temperature and pressure across all contact surface of intermediate surface and surface of the product;
  • removal of intermediate surface;
  • evaluation of image quality.

Now let’s briefly consider all stages.

The polymer coating on the surface of product is created by the standard technology of powder coating (see «Powder coating»).

The image on the intermediate surface (transfer paper or special polymer paper) is formed by one of the following methods: ink jet printing, screen printing, offset printing.

Major world manufacturer and leader in innovative development of transfer paper is an Italian company «Miroglio S. p.A.»

Positioning of intermediate surface and clamp are provided by wrapping and fixing of details by transfer paper (method of “stocking”). Then evacuation of interior space between paper and part is followed.

Method of “suitcase” is used for flat products, when maximum contact of transfer paper and surface is achieved by creating a vacuum inside a closed “suitcase”, top cap of which is made of the finest silicone membrane.

The evacuation takes place during the whole technological cycle before the product is out of the curing oven.

The final stage of decorating is actually the image transfer. For this purpose, the curing ovens are used. They provide a temperature range from 150 °C to 220 °C.

The duration of exposure is from 1 to 10 minutes.

Specifications and features of our equipment are described in the section «Equipment».

And the last: evaluation of decoration quality.

Since there are no quantitative criteria, we use only visual analysis of formed image according to the following parameters:

  • the deviation in color;
  • blurred of contours;
  • uneven of layer;
  • not complete dye transfer from the intermediate surface.

The practical side of equipment and conditions of decorating optimization, aimed at improving of its quality, assumes that all components’ parameters of technological cycle are known with great accuracy.

Belmar Ltd conducts experimental research on the measurement of threshold characteristics of transfer paper. The continuation of this works, apparently, will allow to define more detailed practical advice on decoration techniques which will be based on the selected criterion of quality of output image.