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- July 01, 2010, By Timothy J. Walker Contributing Editor
Getting the shaft may sound bad in street lingo, but in winding there are good and bad aspects of whether you want to get the shaft (wind with a shaft inside your core) or not (wind with a core supported by end chucks or other no-shaft options). To clarify:
- Shafted Winding | Converting equipment used to accumulate the web, starting with a core supported by a full-width shaft inside the core, to form a wound roll.
- Shaftless Winding | Converting equipment used to accumulate the web from an upstream process but without a continuous full-width shaft inserted through the core. There are two common designs for shaftless rewinds or winders: two drum surface winding and end-chucked center winding. Shaftless rewinds eliminate the need to handle the shaft between the finished and new core, improving productivity, safety, and ergonomics.
Why You Want To Get the Shaft
These are the advantages of shafted winding and the disadvantages of shaftless winding.
Due to the structural support of the shaft, shafted rewinds can use thinner, less expensive cores and will have less deflection than a shaftless rewind. Due to the lack of structural support of the shaft, shaftless rewinds need to use cores with a stronger structure, unless the winding roll is supported from below by a non-deflecting support roller or rollers, such as two-drum surface winders.
Since the shaft can support rolls of various widths, the rewind arms do not need to be laterally adjustable, simplifying the rewind design and lowering equipment costs. If the shaftless rewind uses two chucks to support the roll, the arms must have a mechanism to engage and retract laterally, requiring a more complicated machine design.
Shafted rewinds have more contact area with the core, transmitting more torque without slippage. Shaftless rewinds have less contact area with the core than shafted rewinds, so they have less capacity to transmit torque to a winding roll without slippage (though a keyway on a core can greatly improve chuck torque transmission capacity).
Since the shafted rewind has a temporary shaft extending out both sides of the wound roll, the roll can be removed from the machine without contacting the roll of material or using a core wider than the web.
Why You Don't Want To Get the Shaft
These are the advantages of shaftless winding and the disadvantages of shafted winding.
Manual shaft handling is an ergonomic challenge and safety hazard. Automatic or semi-automatic shaft handling may eliminate the ergonomic and safety problems but requires added equipment costs, maintenance, and space.
Shaft handling greatly increases the time required between finishing a roll and starting a new one. The added mass of a full-width shaft adds to the weight needed to be lifted to remove a roll and increases the inertial torque needed to accelerate or decelerate the winding roll, increasing motor and energy costs.
Shafted rewinding usually requires an operator to manually inflate a pneumatic bladder and, if forgotten, leads to waste from slippage-related contamination and lateral shifting. Since shaftless chucks are fixed to the winding equipment, any pneumatic inflation of bladders can be automatically engaged and detected to prevent slippage-related contamination and lateral shifting.
Of all these issues, ergonomics and productivity are the top reasons many folks try to avoid the shaft. Lightweight shafts can greatly reduce ergonomic concerns and help with productivity.
In most winding, getting the shaft is the preferred option to create the best roll quality. If core deflection, handling damage, and torque transmission problems kill your yields, you can win by improved ergonomics and productivity.
Web handling expert Tim Walker, president of TJWalker+Assoc., has 25 years of experience in web processes, education, development, and production problem solving. Contact him at 651-686-5400; firstname.lastname@example.org; www.webhandling.com.