Pultrusion process

Pultrusion is a continuous process for manufacture of composite materials with constant cross-section.
It is more widely used in industries where there is a continuous demand of the product

1. PULTRUSION Presented by, ROLWYN MARIAN CARDOZA 1RV18MMD15 MTech MACHINE DESIGN RV COLLEGE OF ENGINEERING.

2. What is ‘PULTRUSION’ ? Pultrusion is a continuous process for manufacture of composite materials with constant cross-section. PULTRUSION = PULL + EXTRUSION

3. IMPORTANT COMPONENTS OF PULTRUSION PROCESS 1. Fiber Creels 2. Resin impregnation systems 3. Preformer 4. Hot dies 5. Pulling mechanism 6. Cut off saws

4. CREEL A rack holding cylinder or cone holding threads or spools when spinning.

5. RESIN IMPREGNATION SYSTEM It allows the reinforcement travelling from the creels down into the bath and the resin coated fibers comes out through a guided bar.

6. PREFORMER Preform plates are critical component of pultrusion system as it properly aligns and feeds the reinforcement to the heated die.

7. HEATING DIES The main component of any pultrusion system where part to be produced is given shape and is cured. Heated dies are often about 1 m long, there is sufficient time to fully cure the resin.

8. PULLING MECHANISM Pulling system pulls the product from the heated dies on a continuous basis. Generally, a caterpillar belt is used in the pulling system.

9. CUT OFF SAW The last unit of pultrusion system is cut off saw which cuts the pultruded product in desired size. Flying type of cut off saws commonly used.

10. RAW MATERIALS USED IN THE PULTRUSION SYSTEM Reinforcing materials : Glass (E-glass and S-glass), Carbon , Aramid fibers in the form of roving strands, mat (continuous filament mat, chopped strand mat) and fabrics. Veils Matrix materials: Unsaturated polyester, epoxy, vinyl ester resin and phenolic resins are used.

11. CHARACTERISTICS OF PULTRUSIONS Volumes of production : Depends on the size and complexity of the shape. 500 metres is a typical minimum run.   Unit price vs capital investment : The cost is lower than that for some moulding processes such as injection and compression, but higher than for, hand lay-up moulding.   Speed : Depends on size, but as a rule of thumb it is possible to achieve 0.5 metre per minute for a profile measuring 50 by 50 millimetres, 0.1 metre per minute for chunky shapes and 1 metre per minute for narrower sections.   Surface : The surface finish can be controlled to a degree, depending on the reinforcement and polymer.  

12.   Types/complexity of shape There are no problems with undercuts in pultrusion. Virtually any type of shape that can be squeezed through the die can be made, bearing in mind that the shape must have a constant thickness.   Scale The maximum size for profiles is typically 1.2 metres wide, although there are specialist machines that make larger components. Minimum wall thickness is approximately 2.3 millimetres. The size of the manufacturing plant dictates the limit to the length of the pultrusion.   Tolerances Vary depending on the profile, but on a standard box-section, with a wall thickness of 4.99 millimetres, the tolerance is ±0.35 millimetre.

13. DISADVANTAGES OF PULTRUSION SYSTEM: The process is mainly suitable for constant cross sectional areas. Tapered and complex shapes cannot be produced with this method. Control of fiber orientation is not possible in the pultrusion system. Quick curing resin systems typically have lower mechanical properties. Voids may result in parts if excessive opening given at die entrance. High initial investments.

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