Picking a Winner
Do you take your shafts and chucks for granted? It’s probably easy to do, because although they are important components in any web handling or printing operation, they don't tend to elicit much excitement.
For those companies that supply these components, however, shafts and chucks are exciting and require the high level of attention that is afforded any device that carries heavy weights at high speeds around operating personnel.
Mark Fortin, president of Double E Company, points out that the first considerations when specifying shafts has to be structural safety. “That means that the shaft, as a beam, has to be capable of safely supporting the intended roll weight at the design speed of the machine,” he says. “For this, it is important to know the operating conditions that will result in the highest stress and deflection of the shaft. When a machine user plans on running multiple web widths, the heaviest roll will very often not represent the worst shaft bending case.”
Once the shaft strength and deflection are addressed, the next area to consider is to make sure the shaft will be running below its critical speed, especially in high-speed applications. “Today’s higher web speeds and wider web widths can result in vibration that necessitate machine slow downs at minimum roll diameters,” says Fortin.”
One important factor in dealing with the issues of stress, deflection, and critical speeds is the shaft material being used. In addition to high-strength steel and aluminum shaft materials, Fortin points to the variety of high-strength carbon fiber options that can be used to address these issues.
Specifying core chucks
With core chucks, Fortin notes the importance of differentiating between simple unwinding with brakes and regenerative unwinding in which the drive motor also provides the braking action. “The first case is best served with automatic torque-type chucks, while the latter requires pneumatic/mechanical chucks that are controlled to be either on or off,” he states.
Another area that must be considered is to make sure that the torque per chuck is within allowable limits for the chucks, as well as the core itself. To check this, the total operating torque is divided by the number of chucks/brakes being used. “Larger rolls and higher speeds demand heavier, harder, and stronger cores and care must be taken to account for dynamic torque loading that can result from emergency stopping at higher operating speeds,” says Fortin.
With these basic design factors addressed, on-going maintenance has to take center stage. This is a critical factor, according to Bob Banks, Jr., manager for Boschert, LLC.
“It has been my experience that most applications start out well enough and last for a relatively long time. But the customer forgets there is wear between the seat of the safety chuck and the journal of the roll shaft. At some point this wear begins to affect the performance of the safety chuck and [it] begins to wear out.”
A preventative maintenance program that inspects the dimensional integrity of the safety chucks and the shaft journal will protect a converter’s investment in these components. “If [the converter] will adhere to the tolerances of the roll shaft journal specification and the tolerance of the specifications for the seat of the safety chuck, he can have trouble free service for many years,” notes Banks.
On the other hand, “customers that forget about their safety chucks until there is a problem are burdened with having to make significant repairs to their safety chucks and roll shaft journals. In some cases the safety chuck is worn out and has to be replaced. These are expenses that can be minimized with a good PM program.”
To meet your requirements for shafts and chucks, take look at the following products.
Improved roll quality
Tidland Corporation has introduced its D4 differential shaft to provide improved finished roll quality, along with enhancements to its existing D2 and D3 models to reduce set-up time. The Equalizer - Model D4 Differential Shaft represents the latest technology for converting dust-free rolls. Precise control of tension as low as 0.15 PLI allows converters to run ultra-thin films common in today’s converting operations. A unique, two-row, 12-ball, torque-activated core-lock design insures equalized tension across any combination of roll widths.
Tidland has also enhanced its existing line of core-slip differential air shafts to provide tension equalization across any combination of roll widths. The Equalizer - Model D2 is ideal for repeated slit-width runs with operator-positioned, tool-less core stops that can be set and retained through multiple runs. The Model D3 is ideal for repeated or varying slit width runs with automatically positioned core stops.—Tidland Corp., www.tidland.com
Ergonomic shafts and chucks
Tidland’s latest lightweight air shafts are designed to improve overall roll quality, increase operator job satisfaction, and reduce workers’ compensation claims. The newest 4˝ and 5˝ GX shafts round out Tidland’s full-line of ergonomic solutions, which now includes aluminum extrusion and carbon fiber shafts in 3˝, 4˝, 5˝, and 6˝ sizes, along with the 6" Force5 air chuck. The combination of heavy load carrying capacities and low overall shaft weight help customers to implement an ergonomic, affordable shaft solution for eliminating lifting hazards.—Tidland Corporation, www.tidland.com
Air-roll-lock differential shaft
Convertech, Inc. has introduced a new differential shaft design to reduce shaft changes and simplify the converting process. With the addition of GlideLock rollers to the differential shaft, converters can easily run multiple width cores on the same shaft while ensuring proper tension. Instead of being forced to change shafts for different jobs, the new differential shaft allows converters to use the same shaft for many different jobs, reducing downtime dramatically.—Convertech, Inc., www.convertech.com
Core shafts for simplified loading/unloading
The newest member of Double E’s family of core shafts is the DRS-4000 Differential Rewind Shaft. This shaft simplifies loading and unloading, and accommodates narrow slit widths down to a half inch. Various ring widths are available to suit every application. The DRS-4000 overcomes load capacity issues common with other differential shafts, and offers better core gripping performance.—Double E Company, www.doubleeusa.com
Pinch-point free shaft locking
Converter Accessory Corporation (CAC) has introduced a heavier duty ShaftLock™ safe operation shaft holder for unwind and rewind rolls. Unlike conventional safety chucks, ShaftLock is a safety chuck with no pinch points, providing enhanced operator safety. It opens only in the up position to allow an easy unload operation. ShaftLock is available in several models able to handle loads and roll weights up to 5,000 lbs. and operate effectively at low to high speeds. It features replaceable cradles and inserts which are available for square, diamond, triangle, half round, and custom-shaped shafts and shaft ends.—Converter Accessory Corporation, www.handleyourweb.com
Replaceable insert
Boschert’s VT Style VT-7 replaceable insert design allows the concentricity between the safety chuck and roll shaft to remain almost as precise as new throughout the life of the VT-7. It features a roll shaft journal made of a round part with a square part, where the round part accepts the load-bearing footprint of the roll shaft, and the square part transmits torque through the safety chuck to the roll shaft. Thus, the torque of the operation is separated from the load-bearing footprint of the roll shaft. The result is longer life between roll shaft journal changes and replaceable insert changes, along with improved quality.—Boschert, LLC, www.boschertllc.com
Lateral positioning
Goldenrod’s Manual Sidelay Safety Chucks allow lateral positioning of the core shaft and material roll up to ±1˝. The chucks can be produced so the shaft extension remains in a stationary position making it practical for mounting drive belts or couplings. Models are available with ratings of 2200 lb. load per chuck at 600 rpm or 4000 lb. load per chuck at 1500 rpm.—Goldenrod Corp., www.goldrod.com n