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Reverse Pyramid Winder Mandrels

The Reverse Pyramid winder mandrel is a unique design developed by T. Sendzimir Inc., and has been extremely successful in the years since it was introduced to the rolling mill industry.

What Sets Winder Mandrels Apart From The Rest

Sendzimir’s reverse pyramid winder mandrels are designed and built for up to 132,000 lbs. maximum tension. We have designed over 120 pairs of controlled collapse winder mandrels. The Sendzimir winder mandrel design evolved through 3 successive stages:

Forced Collapse design, then Original Controlled Collapse Design Mandrel, until finally we landed on our final stage: Reverse Pyramid Mandrel. Orientation of the pyramids was reversed to enable a vastly superior mandrel design and reduced maintenance due to stronger construction, which is why it was the design Sendzimir still uses.

Standard Winder Mandrel Features

Outboard Bearing Gates

Sendzimir designed sliding sleeves that engage after the gate is fully closed. This design is superior to the tapered cone bearing design that allows the outboard bearing gate to partially open or move under winding tension loads which may force a bend in the mandrels.

Easily Adjusted Gate alignment

Using the built-in adjusting wedges, our design is easier to implement in comparison to the shimmed method design.

Quick Removal

Our cylinder uses a hollow shaft design, and is mounted on a stand-off that extends out from the back of the gear shaft. This design enables the cylinder to be installed and removed as a unit, without disturbing the mandrel.

Integral Splines on the ID

Direct spline connection for the gear shaft to the pyramid shaft enables an increased pyramid shaft diameter (2″ to 3″ greater on a 24″ [610mm] diameter by 50″ [1270mm] wide mandrel than competing designs) at the front bushing, providing more strength and rigidity by eliminating the spline adapter previously used. The integral spline design is especially valuable for 20″ (508mm) diameter mandrels with inherently high internal stresses.

No coil breaks at the segment corners and minimal at the gripper slot area

Coil breaks have been minimized at thin gauges and eliminated for the majority of rolling due to a redesign effort to reduce the distance between the segments.

Optimized Heat Treatment

Winder Mandrel components have been optimized for maximum strength and designed for minimal stress concentrations. This concentration on strength and reliability ensures a long service life for these mill components.

Shear Rings

A shear ring mounts the pyramid shaft on a rotating cylinder piston and the piston itself. This ring will break to protect the pyramid shaft against overloading which could occur, for example, if the coil was wound on a collapsed mandrel.

Mounted Screws

Segment retainers are mounted with screws that are designed to break if an attempt is made to collapse an un-greased mandrel. When these screws break, it provides a safe warning that greasing must be performed.

All the above features increase the initial cost of our winder mandrels, but ultimately result in a safer operation, greater ruggedness, easier maintenance, and lower overall service costs.

Typical Mandrel Description & Scope of Supply

Reverse Pyramid winder mandrels are designed for 20” (508 mm), 24” (610 mm), and 30” (762 mm) diameters.

These mandrels are typically designed for under-winding. Each assembly consists of a mandrel, low-speed gear shaft, rotating cylinder, outboard gearing gate, and upward bearing gate with sliding sleeve.

  • Expand-Collapse of a winder mandrel works due to a rotating hydraulic cylinder that is mounted on the back end of the output shaft. It can be removed without disturbing the shaft or segments. The connection of the pyramid shaft to the rotating cylinder is provided by a threaded nut with integral shear ring.