Lamination process is an important process in lamination molding. The lamination process is that the impregnated adhesive tape is laminated into slabs according to the pressing thickness requirements, placed in two polished metal templates, placed on the hot press, heated and pressurized between the two layers of templates, and then cooled and demoulded after hot pressing and curing.

1、 Laminating equipment

The main equipment is hot pressing unit. The auxiliary equipment includes loading and unloading machine, template rotary machine, template cleaning machine, laying mold cleaning machine (stacking machine) and other equipment. From the production combination, it is divided into single hot pressing and cooling machine and two hot pressing and cooling machines.

At present, there are two kinds of hot presses used at home and abroad: open hot press and closed vacuum hot press. Compared with the open hot press, the vacuum hot press has two outstanding advantages: 1) the molding unit pressure is 1 / 2-1 / 3 lower, that is to reduce the flow of glue, reduce the warp and weft line movement of cloth, reduce the internal stress of laminate, and achieve the purpose of reducing warpage; 2) it can avoid gas bubbles in the plate and corner, and the product quality is higher; vacuum hot pressing is more and more widely used in composite molding.

The performance and control level of hot press directly affect the quality of products, and have a direct relationship with the molding process. The hot press mainly controls the temperature field and pressure of the heating plate.

Heating plate

The structure of the heating plate and the hot medium used directly affect the uniformity of the temperature field of the heating plate, the uniformity of the temperature field on the plate surface, the uniformity of the melting of the adhesive tape, and the discharge of the gas produced after gelation and the air between the adhesive layers. Therefore, the heating rate of heating plate should be fast and uniform, and the temperature difference of plate surface should be less than 3 ℃.

There are two kinds of heating plate channels: single in and single out and double in and double out. The latter is complex in manufacture, complicated in piping and high in cost, so it is seldom used. The former uses steam heating, and the temperature difference of the plate surface is large (about 5 ℃); when hot water or heat transfer oil is used, the temperature difference of the plate surface is lower than 3 ℃; the effect of using heat transfer oil is better, because the pressure of heat transfer oil is low (less than 0.5MPa) and the temperature is high (about 300 ℃).

For the temperature control of the whole machine, there are 12-20 openings in the hot press, so that the heating plate presents a temperature gradient from the bottom to the top. The results show that there are more single point total control for steam heating, and the gradient is about 5 ℃. Hot water or heat transfer oil is generally controlled by zones (generally divided into 2-3 zones). The temperature gradient is only controlled below 3 ℃, which is conducive to the same curing speed of upper, middle and lower parts under the same pressure, which is conducive to improving the product quality.

pressure

At present, hydraulic press is mostly used for hot pressing, which can meet the unit pressure required for product forming, up to 12.5mpa, and the pressure stability is less than ± 500kPa, which can be set according to the process requirements. The tonnage of multi-layer press is generally large, usually 2000-3000t.