The Merits of a Repurposed Slitter Rewinder
- Published: February 19, 2024
By Alan Fayerman, Product Manager and Bill Strake, Sales Manager, Valmet
When a converter approaches an OEM supplier with a need for a slitter rewinder, project goals and scope must be conveyed precisely and clearly. Project intents typically fall in one of the following four areas: Increased production, improved finished roll quality, increased reliability and improved machine safety. With these goals in mind, consideration should be given to the possibility of rebuilding the existing equipment.
Existing equipment may need to be repurposed for running new products. For example, a slitter rewinder may have been originally designed for running a nonwoven product and now needs to be reconfigured to run a lightweight grade paper. This conversion may require alternate slitting modes where the score slit system is replaced with a shear system (be it tangential or wrap shear) or remain in place where both systems are needed.
Increased Production Needs
If the project goal is increased production, beyond faster winder speeds, material handling efficiency should be examined to find ways to reduce the machine downtime during roll set changes and decrease slitter set up times. Increased production can often be achieved by providing a pickup unwind (either shafted or shaftless) that will replace an old style shafted backstand. Conversely, shaftless rewinding, or cantilever rewind shafts, can eliminate the need for rewind shaft handling.
Winder downtime can be decreased by adding roll cut-off knives, finished roll discharge devices and core insertion mechanisms. These items include roll cradles, ejectors, pushers and roll manipulators, all of which must be customized to the downstream finishing process.
Core and finished roll taping, and if required for the product, tabbing insertion, are also available to increase winder throughput.
Replacing older drum and water-cooled brakes with modern braking systems will reduce operating cost and usually supply a greater range of tension control.
At the same time, rewind shaft handling equipment along with automated hoist systems will reduce winder downtime.
If the product maker line can supply larger finished rolls that will be sent to the slitter, manufacturers can realize reduced change over time by making multiple finished sets from a single master roll.
Quality Improvements
Finished roll quality improvements can often be addressed by automatically controlling web tension, nip load and the torque output of the winder drive system. Higher winder speeds often require faster control reaction times where an electronic tension control system might replace an older mechanical dancer roll.
Replacing worn components is a typical way to bring a slitter rewinder back to peak operating condition. For example, worn winding drums can contribute to several winding defects including dishing, interweaving, loose starts, telescoping and inconsistent roll density.
Converters can attain improvements in slit web separation by replacing bow spreader bars with bowed rolls. While spreader bars still have a place in the converting industry, modern web coatings may be susceptible to picking and surface scratching. These web defects can sometimes be eliminated with the use of a bow spreader roll.
Improved Reliability
Historically, converting winders have been driven by variable speed DC drives and motors. However, in recent years, DC motors and drives have been replaced by AC vector drives and motors. The reason being, AC motors tend to require less maintenance, and are less costly to purchase and operate.
Improved Safety
Machine guarding has become an area of concern for the converting industry. When safety is a project driver, the overall mechanical condition and configuration of the machine must be reviewed to ensure that the required safety equipment can be physically added. These devices might include safety latches that retain roll cradles or other moving equipment. Additional components, such as safety mats and fencing, photo eyes and appropriately placed emergency stop devices may be required as well.
Often, spacing between driven and non-driven rolls, as well as stationary machine structures, may not provide the proper safe clearance distances. Adapting physical guarding and safety upgrades to an older winder may sometimes impact winder capacity. These losses are often offset with additional automation upgrades.
Another pain point converters often have is the need for an existing piece of equipment to operate with speeds exceeding the original design parameters. Increasing operating speeds, as well as the winder’s level of safety, may require components which may not physically fit within the confines of the existing winder or be cost prohibitive. When faced with this scenario, the only real solution is to build a new winder where all the functionality, production needs and current safety requirements are provided as a standard.
Partnering with the Right Supplier
When looking to upgrade a machine, whether the goal is improved quality, reliability, safety or production levels, it is important to partner with a supplier that can help identify the existing equipment that can be remanufactured and repurposed for a current need. Some suppliers can offer rebuilds with minimal downtime, and depending on the scope of the rebuild, provide a new machine warranty.
About the Authors
Bill Strake has been associated with the Cameron product line since 1983 as Business Development and Regional Sales Manager. When the Cameron and GLV brands were acquired by Valmet in 2019, Bill became a Cameron consultant for Valmet. Bill holds a Bachelor of Science degree from Roger Williams University in Bristol, RI and is an active member of the Technical Association of the Pulp & Paper Industry.
Alan Fayerman has over 40 years experience in the paper and converting industry, beginning his career with the Cameron product line in 1983. He has held various roles including Applications Engineer, Mechanical Engineering Manager, VP of Engineering and President at Cameron in the U.S. When the Cameron and GLV brands were acquired by Valmet in 2019, Alan became Product Manager for Specialty Winders. He has a Bachelor of Science in Mechanical Engineering from the New Jersey Institute of Technology and a Master of Business Administration from Seton Hall University.