More About Composites (2) Production Method – Hand Layup
Hand lay-up is also called contact molding. It is a process in which fiber-reinforced materials and resin are spread on a mold, cured at room temperature or under heating without pressure (or low pressure), and demolded into products.
Process characteristics:
The hand lay-up process is the earliest used and widely used molding method in the production of resin-based composite materials. The hand lay-up process is mainly manual operation, and less mechanical equipment is used. It uses unsaturated polyester resin or epoxy resin as the matrix material to bond the reinforcing materials together.
Although the operation of hand lay-up is simple, it requires higher operating skills for operators. It requires the operator to have proficient operating skills and rich practical experience. It is necessary to have a more comprehensive understanding of product structure, material properties, mold surface treatment, gel coat quality, glue content control, cutting and laying of reinforcing materials, uniformity of product thickness and various factors affecting product quality.
Advantages of hand lay-up process
(1) The mold cost is low, easy to maintain, less equipment investment, and quick to start;
(2) Short production preparation time, simple operation, easy to understand and learn;
(2) It is not limited by the size and shape of the product, and is suitable for products with small quantities, many varieties, and simple shapes or large-scale products;
(3) According to the design requirements of the product, it can be arbitrarily reinforced in different parts, with great flexibility;
(4) Resin matrix and reinforcement materials can be optimized and combined with other materials (such as foam, balsa wood, honeycomb, metal, etc.) into products.
(5) Curing at room temperature and molding under normal pressure.
(6) Color gel coat layer can be added to obtain colorful and smooth surface effect.
The disadvantages of hand lay-up are:
(1) Low production efficiency, high labor intensity, and poor production environment conditions;
(2) The stability of product quality is poor, which is greatly affected by human factors;
(3) The workshop covers a large area and requires good ventilation equipment.
Product demoulding
Generally, it can be cured naturally at room temperature for more than 24 hours and the products can be demolded according to the selected resin curing system. If you use manual demolding, you can demold with wooden wedges and other materials with less hardness than composites materials. Take care not to damage the mold and the product when demolding, and it is forbidden to hit or drop the mold.
Demoulding is a key process in the process of hand lay-up composite products. The quality of demolding is directly related to the quality of the product and the effectiveness of the mold. Of course, the quality of demolding also depends on the design of the mold, the surface finishing of the mold, the effectiveness of the release agent and brushing and the most important, the demold technology.
