Steel Cylindrical Winding Mandrel

Steel cylindrical winding mandrel is the removable steel core around which FRP tanks and pipes are filament-wound. After the composite cures, the mandrel is removed (collapsed or extracted), leaving a finished hollow FRP product.

Mandrel Construction

The mandrel is a precision steel tube or welded cylinder machined to the exact inner diameter of the finished product. It includes end fixtures for mounting on the winding machine headstock and tailstock. The outer surface is coated with a release agent so that the cured FRP does not stick.

Types of Mandrels

• Solid steel mandrels: removed by hydraulic extraction for small-diameter pipes.

• Collapsible mandrels: segmented steel cores that collapse inward for removal from large tanks.

• Water-soluble or plaster mandrels: dissolved or broken out for complex shapes.

• Disposable mandrels: left inside the product (rare for FRP).

Features

Mandrels must be straight, rigid, and dimensionally accurate. They are often heated internally to assist resin cure. The surface must be smooth to produce a good inner finish on the FRP product. End fixtures must support the weight of the wet composite during winding.

Applications

Winding mandrels are used to produce FRP tanks, pipes, pressure vessels, chimney liners, and ductwork. The mandrel directly determines the inner diameter and inner surface quality of the finished composite product.

Conclusion

The steel cylindrical winding mandrel is a critical tool in filament winding. Its accuracy and surface finish directly determine the dimensional quality of the finished FRP pipe or tank.