Pultrusion machines use shaping and curing to manufacture rods, tubes and structural shapes with a specified cross-section. They force or pull raw material into alignment guides and shaped dies to produce lengths of stock forms and cross-sectional shapes.
Specifications for pultrusion machines include machine length, width, and height; profile envelope and process height; pull force, clamp force, and pull speed; and pull platen length and puller stroke. With hot pultrusion machines, the number of heat zones is also an important specification to consider. Modular pultruders with a flying cut-off saw carry parameters such as number of axes. There are many different types of pultrusion machines.
Typically, suppliers categorize products by the material extruded, application, or extrusion technology. For example, fiberglass pultrusion machine are used for making fiberglass that is suitable for advanced windows design. Pultruded fiberglass is dimensionally-stable over a wide temperature range and has low thermal conductivity. In addition, this pultruded material is moisture resistant and chemically inert. In terms of technology, pultrusion machines may use hot or cold processes. Hot pultrusion machines form plastic, rubber, metal, or composite products from raw materials that have been preheated. Cold pultrusion machines do not. Pultrusion machines use two types of pullers: reciprocating and caterpillar. Reciprocating pullers or hydraulic pullers use higher pull forces to produce parts. They are also suitable for environments in which frequent setup changes are required. Typically, reciprocating pullers use a PLC or programmable logic controller to synchronize separate clamping and pulling mechanisms. Caterpillar pullers use a continuous, electromechanical system with two rotating tracks. Pultrusion machines that use caterpillar pullers are well-suited for applications with lower pull speeds and lower pull forces. These pultruders may also be used for high volume, repetitive pulling with multiple cavities. Typically, the puller has pneumatic cylinders for clamping and pulling in the same operation. Modular pultrusion machines are available with die beds and separate puller, cut-off, and roll-off sections. Die beds are open or closed and manual or automatic. They may provide multiple tie-down point for the removal of dies, integrated heater controls, and inspection lights at the die exit. Cut-off sections are used to clamp profiles to a saw table that moves at the process speed. After the blade cuts the profile, the clamp disengages. Pultrusion machines with roll-off sections come with special tables that consist of a series of steel rollers mounted on a sturdy open frame.