Mandrels different components

Peters et al described how, for huge winding applications, the usage of one complete (fully) mandrel is not useful, based on the weight and costs. The mandrel for winding applications with large diameters consists of different components. The inner part is a hollow framework construction and only the surface of the mandrel is closed with wood, aluminum alloys, steel or a similar material (Fig. 7.8). 

An advantage of the autoclave for smaller components, is that a large volume of the same or different products can be vulcanised at the same time, provided that the curative systems in use do not interact between the different compounds. It is usual to support extrusions and low hardness products in talc. Products formed on mandrels and sheeting, for example, are cloth wrapped to prevent distortion. 

Many rubber products require uncured components which are not rectangular in cross-section. In such cases, at least one calender bowl may have a peripheral design cut into its surface to produce the desired cross section. This method is particularly useful for long production runs, but becomes expensive in terms of bowl change and bowl inventory necessary when many different sections are required. For shorter run working, the calender bowl may consist of a heavy basic mandrel onto which may be clamped solid cylindrical or split cylindrical steel shells into which the appropriate profile design has been cut. Such calenders often have the bowls outside the frames to improve access and facilitate bowl changing. Consequently the bowls are comparatively short. 

For an optimal consolidation it is necessary to apply a consolidation pressure in the winding process. After the polymer is molten the rovings/tapes are wound (with consolidation pressure) on the mandrel. Generally, there are two different ways to apply the required consolidation pressure. In the first system the consolidation force is applied only with the tape tension as a result of the break system used (Fig. 7.6). The acting consolidation pressure depends on several factors, besides the acting tension, for example material temperature and viscosity, and the consolidation zone is not well defined. Furthermore, the applied tape tension can induce significant residual stresses in the component. The consohdation roller of the second system apphes... 

The shape of the component must permit mandrel removal. Long, tubular shapes will generally have a taper. Different mandrel materials, because of differing thermal expansion and differing laminate layup percentages of hoops versus heUcal pUes, will demonstrate varying amounts of difficulty in removal of the part from the mandrel. 

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