Rotational molding process is also known as rotary molding, rotary casting molding. It is a hollow molding method of thermoplastic.
Rotational molding is a multi-purpose process for manufacturing various hollow plastic parts. Rotational molding process uses heating and rotation along two axes to produce hollow single parts. The molten plastic is injected into the rotating mold, and the centrifugal force forces the molten plastic to stick to the inner wall of the mold.
That is to say, the powder or paste material is injected into the mold first, and the material is evenly covered with the mold cavity and melted by its own gravity and centrifugal force through heating the mold and rolling and rotating in the vertical and horizontal directions, and then demoulded to get hollow products after cooling. Because the rotational speed of rotational molding is not high, the equipment is relatively simple, the product has almost no internal stress, and is not easy to deform and sag. Initially, it was mainly used for PVC paste plastic production of toys, rubber balls, bottles and other small products. Recently, it is also widely used in large products. The resins used include polyamide, polyethylene, modified polystyrene polycarbonate, etc.
It is similar to rotary casting, but the material used is not liquid, but sintered dry powder. The process is to put the powder into the mold and make it rotate around two mutually perpendicular axes. The hollow product can be obtained from the mould by heating and uniformly fusing on the inner wall of the mould, and then cooling.
Also known as rotary molding or rotary molding. Powder plastic (such as LLDPE) is added to the closed mold. The mold is heated while rotating. The plastic melts and adheres to the surface of the mold cavity evenly. After the mold is cooled, hollow plastic products with the same shape as the mold cavity can be obtained, such as boats, boxes, barrels, basins, cans, etc. It usually consists of feeding, mold sealing, heating, cooling, demoulding, mold cleaning and other basic steps. This method has the advantages of small shrinkage, easy control of wall thickness and low cost of mould, but low production efficiency.
The main features of rotational molding process are as follows:
1.The cost of rotational mold is low – for products of the same size, the cost of rotational mold is about 1 / 3 to 1 / 4 of that of blow molding and injection molding, which is suitable for molding large plastic products.
2.Rotational molding product edge strength is good – rotational molding can achieve product edge thickness of more than 5 mm, completely solve the problem of hollow product edge thin.
3.Rotational molding can place various inlays.
4.The shape of rotational molding products can be very complex, and the thickness can be more than 5 mm.
5.Rotational molding can produce totally closed products.
6.Rotational molding products can be filled with foaming materials to achieve thermal insulation.
7.The wall thickness of rotational molding products can be adjusted freely (more than 2mm) without adjusting the mold.
Post time: Jul-14-2021