GLOSSARY OF TERMS
|Cantilevered Shafts||A cantilevered shaft is permanently connected to only one side of the machine. In the case of slitters this is commonly seen in so called "doctor machines", providing easy access to the web. Rewinds are sometimes cantilevered, usually with a temporary devise to hold up the end of the shaft as it is rewinding. When the rolls are rewound the rewind shafts either swing out or the device holding them up on the end swing away. This allows for an easy way to unload the rewound rolls from the shaft.|
|Lock Core||When a slitter, typically duplex is rewinding a roll in a configuration where the core or cores are fixed to the rewind shaft. They are usually held in place by expanding the rewind shaft with air to grab the cores. Unlike the slip differential mode where each core slips on the rewind shaft there is no slip in the lock core mode. Other winders, such as most simplex machines operate in this mode as well|
The key advantage of razor slitting is the low cost and ease of setup. A razor blade is inserted through the material in one of several ways. The material may pass over two small idler rolls creating a space where the razor can be inserted; called razor in air. Or the material can wrap around a special roller with groves cut into it and the razor can pass through the material into these grooves. Finally the material may pass over a hardened roller and the razor blade may pass through the material and cut against the roller. The razors are affixed in a variety of ways and slit width changes are simple. However this slitting method is limited mostly to thin films and is not as accurate as shear and does not produce as good an edge quality.
|Score Slitting||A slitting method whereby a rotating knife which can be sharpened to various angles is pressed against a hardened roller. As the web passes through this intersection it is slit. This method is commonly used for paper slitting and has the advantage of allowing for quick size changes. In many cases shear slitting is preferred because it can give a better slit edge and can cause less dusting.|
A slitting method commonly considered preferable both for the quality of the cut edge and the accuracy of the cut. A round male knife intersects with a round female knife with varying degrees of depth of intersection and side loading force. Both the depth and the amount of side or shear force will vary depending of the substrate being slit. In addition key variables to consider are the diameter of the knife, the type of material it is made from, the angles the cutting edge are ground to, and the cutting profile of the male knife. The disadvantages of shear slitting are the initial cost of tooling and the time it takes to perform a set up.
|This method of rewinding material is used in various types of Duplex rewinding applications. This method was designed to help wind materials with irregularities such as gauge variation commonly found in webs of film where slitting and winding on one shaft is not possible. In the method the cores are alternated between the two rewind shafts using spacers to separate the cuts. The spacers are locked to a keyway on the rewind shaft so that they spin at the same rate as the rewind shaft. The keyed spacers are side loaded with air causing them to rub against the cores on the shaft. This created a clutching action allowing the operator to define how much tension is built into the rewinding roll. This tension can also be profiled in certain ways called taper tension.|
slitting method material is slit and wound on two rewind shafts with the
cuts alternating. This method gives the ultimate capacity for controlling
rewind tension and cut separation. Typically this method only allows for a
rewind diameter of 24” to 30”. For larger diameters we usually recommend “duplex
center surface” slitters.
|Duplex Center Surface||
Like the duplex center slitters these machines rewind slit rolls on two shafts and provide excellent tension control for the widest variety of materials. However, these machines rewind the material both using the rewind shafts and assisting with a driven roll driving the surface as well. This allows for building larger diameter rolls than the “duplex center” slitter can, often from a 40” to 50” diameter.
The roll of material is created by driving the surface of the roll typically using two “bed rollers” in which the rewinding material sits. In this application the rewind shaft is used only to hold the cores and is not driven. Driving the surface of the roll allows for creating larger diameters than winding from the center.