THE NEW TECHNOLOGIES TO PROTECT
LIFE AND OCCUPATION
Progetto approvato
con D.D.R.T. 7772/2000
all'interno del
POR R.T. Ob.3 FSE

 

SHIPBUILDING INDEX

1 MANUFACTURING PROCESS
   1.3    Composite materials
  1.3.1 The manufacturing process
  1.3.2 Materials
  1.3.3 Cutting
  1.3.4 Joining
  1.3.5 Bonding
  1.3.6 Quality control

 

 

1 MANUFACTURING PROCESS

1.3 Composite materials

1.3.1 The manufacturing process

The construction of rafts and boats in composite materials has a less complex manufacturing cycle than those described above. This is due to the smaller dimensions of the vessels in comparison with steel ships, and the smaller number of operations required to produce the vessel. The main operations in producing composite material boats, commonly referred to as inflatable boats, are cutting, welding, bonding and cleaning.

Figure 3 shows the manufacturing cycle. 

 

Figure 3 - Manufacturing cycle in shipyards building vessels in composite materials

1.3.2 Materials

Inflatable vessels are built using a composite material made up of cloth covered in resin. The strength and thickness of the sheets is increased by using more layers, so that the end-material used is multi-layer.

The cloth is made from fibres which have sufficient resistance and flexibility; polyester and polyamide are among the most commonly used artificial fibres. The resin must be capable of producing flexible sheets, which are completely impermeable and easily welded together. Polyvinyl (PVC) and polyurethane are the most commonly used types of polymer.

On arrival materials are off-loaded and stored in a warehouse. The materials are chiefly PVC and polyurethane, equipment and fitting-out material (handles, hooks etc).

The material is then divided between the departments in accordance with the manufacturing cycle.

1.3.3 Cutting

The material is firstly delivered to the cutting department. The main operations here are the same as in an industrial tailors: models are drawn onto the material, showing fixing points for later joining operations. The material is then cut.

The sheet is taken to a table, where it is cut by hand or machine following a model. Simple scissors or similar tools may be used by the skilled operative. The process is not automated as the model of the pieces of material often varies according to the product to be made.

1.3.4 Joining

After cutting the various pieces are delivered to the appropriate joining department. Each department specialises in a particular joining technique:

·          High frequency joining, which exploits the dielectric properties of the material;

·          Hot air or wedge joining which causes controlled fusion of the material.

In the high frequency joining department small standardised pieces with particular shapes are joined, such as handles, hooks and blocks. To make the joins, moulds made out of good conductors such as brass are required, so that they can adapt to variations in the size or shape of the piece. In practice the moulds have the same shape and size as the joins.

The operation consists of several simple phases: first the two different pieces are put together on the mould and pressing begins while charging the two pieces oppositely causes the molecules in the two pieces to move in such a way that they effectively become one piece.

Small sized pieces in difficult shapes are often fixed to a small cloth backing which is in turn joined to the vessel. This technique allows any material of small dimensions to be fixed to the boat.

Fully-equipped individual parts can be produced in the high frequency joining department.

Non-standard sections are made in the hot joining department, using the hot air technique and straight-line joining with hot wedges. These lead to the assembly of ready-equipped pieces produced by the high frequency joining department. Joining departments normally work in series, but some operations are carried out in parallel.

1.3.5 Bonding

Certain types of vessel, which have structures in fibreglass and material, such as keeled hulls or driving consoles, must be bonded together. The fibreglass piece, built as described above for material pieces, is bonded and the quality of the operation immediately tested.

Surfaces to be bonded are prepared by cleaning with solvents.

1.3.6 Quality control

The product is then checked for quality. These checks are non-destructive:

·          That the vessel is fully equipped

·          Pressure holding

·          Equipment installation

The final stage of the manufacturing cycle is the loading of equipment and packing. These final operations are strictly dependent on the type of product.