Different Shafts And Their Applications

Coreshaft nomenclature differs from manufacturer to manufacturer, but the various designs and traits are always recognizable. Here are some of the common types of coreshaft design:

Air Shafts

An air shaft concentrically expands when air pressure increases. The pressurized air is held in a bladder. Often, the shaft features an internal bladder or tube made with a puncture- and abrasion-resistant material.

Multiple-bladder shafts (aka multi-tube shafts) have all their expanding components on the outside of the shaft, enabling easier maintenance. They eliminate the need to remove the journal in order to replace a damaged bladder.

Mechanical Shafts

As their name suggests, mechanical core shafts do not use bladders for expansion but are mechanically expanded instead. They are simper in design and hence easier to maintain.

A fully mechanical shaft typically has an internal cam with a spring system that is attached to expanding lugs. It delivers an optimum centering performance because of its perfect synchronicity in lug movement. Mechanical coreshafts are made from aluminum, steel or lightweight carbon.

Some coreshafts combine mechanical functionality with the possibility of expansion and/or contraction by compressed air. In some pneumatic/mechanical shafts, the initial core-holding operation by expansion is conducted manually, while air retraction offers extra speed and convenience at the end of the process.

Gripping Methods

Both air shafts and mechanical shafts have various ways to grip the core material of the roll. This is an important factor in choosing a core shaft, since grip prevents core slippage. Core shafts include the following types of design: leaf-style, button-style and lug-style. The leaf shaft is useful for 360-degree support in coreless or thin-core winding. Button shafts are economical and used in light-duty to medium-duty applications. Lug shafts are known for their strength of grip and help eliminate core slippage.

Other Shafts

Aside from the fundamental mechanical and air shaft types, there are other specific core shaft designs for various purposes.

Differential Shafts

Differential shafts allow the winding or rewinding machine to run multiple rolls on the same core shaft. The rolls can have different core sizes and the shaft maintains equal tension on all rolls, which can be placed anywhere along the shaft.

Reel/Mill Spool Shafts

Reel spool shafts are normally used in tissue mills to wind tissue paper directly onto cores at the source machine, thus eliminating the cost of rewinding. The shaft may also be used to store the tissue. Lightweight materials such as carbon are sometimes used in manufacturing the shafts, which enables heavier rolls to be produced without changing the overall weight for hoisting.

Slitter Shafts

The purpose of slitter shafts is to hold special anvil blades in place for cutting applications. These blades cut rolls of material (e.g. film, foil, paper, label stock, and laminate) as they are rewound. Slitter shafts fit into dedicated slitter rewinder machines. Naturally, an emphasis is placed on safety when using a slitter shaft, so optimum air pressure has to be carefully maintained.

Choosing the Right Shaft

Choosing the right shaft for the right core is one of the complexities of winding, unwinding or rewinding. The material used in the shaft must be able to grip the core material. Cores are generally made of reinforced or regular plastic, fiber, or metal. These materials can naturally be further divided into specific types (e.g. steel or aluminum in the case of metal).

Fiber cores (aka cardboard) also present a problem in that they need to be able to withstand torque applied by the shaft without damage and loss of tension. To help make these decisions, coreshaft manufacturers offer advice or literature that makes compatibility and various torque capacities clearer.

Another aspect to consider with core shafts is the ability of machine operators to lift them. Heavy shafts can lead to back problems. Carbon composite shafts are substantially lighter than steel or aluminum shafts.