Circular knives and case cut-off knives
We are happy to offer you individual dimensions in addition to the standard ones.
|Areas of application||Paper, cardboard, labels, adhesive tape / film, foil, plastic / nonwoven, textile, special materials|
Circular knives and case cut-off knives from DIENES
Dust accumulation, short service life, unclean cut edges, uneven roll surface, adhering adhesive and dimensional stability of the cut rolls are all issues we have dealt with extensively for decades. Circular knives and core cut-off knives with bevels on both sides are usually used to cut cores.
DIENES offers innovative solutions for all aspects of case cutting, using the following cutting methods:
- fixed circular knives that cut into the rotating sleeve
- driven circular knives that cut into the rotating sleeve
We have dealt in depth with the optimization of tool life through improved knife materials and surface quality. In addition, we are happy to help you improve manufacturing tolerances and optimally adjust the cutting geometry and knife hardness.
Using circular knives and case cut-off knives
During winding the following happens; on the winding shaft the cores are fixed to receive cut tapes, while the spaces between them are filled with loose cores as spacers. After production start of the slitter rewinder, the adjacent cores, i.e. both fixed and loose cores, rub against each other, creating a certain gap. The result is slight telescoping of the cores. This causes the so-called “gramophone effect” to appear on the wound roll.
Therefore, depending on the cardboard core outside diameter and core thickness, the chamfer geometry must be adapted to the requirements. To avoid chipping, the cutting edge on both sides is often not ground completely sharp.
In addition, the centricity of the knife edges is an essential factor for the quality of the knife and the edge is often visually checked. If core-cutting knives are used in pairs or in larger numbers, the knife edges must be ground absolutely symmetrically so that no misalignment occurs on the cut cores.
Nowadays, high-speed steel knives have almost completely replaced the usual cold-work steels due to their longer service lives. In the case of fixed circular knives, these are pressed against the rotating cardboard sleeve by hand or by machine. A plastic tube or an induction- or nitride-hardened shaft serves as a mandrel for the cardboard sleeve and at the same time as a knife stop. Depending on the thickness and diameter of the cardboard sleeve, it makes sense to lubricate the knives with silicone via a drip oiler.
Fixed case cut-off knives are turned further in cycles, if necessary, in order to transfer the knife wear to the entire circumference. Signs that the knives are becoming blunt are the rounded cutting edges that are pressed downwards due to the cutting pressure.
Sleeve tapping stations from DIENES
In slitting, the cut individual webs are usually fed either to a common winding shaft or to two winding shafts. The length of the cardboard tubes to whose circumference the individual webs are glued and wound corresponds to the cutting width set at the slitting station.
The core cutting station consists of a crossbeam on which one or more knife holders are located on linear guides. The knife holders are moved into the respective cutting position by a servo motor located on the linear module. The core cutting station is electrically connected to the fully automatic knife adjustment system of the slitter, so that the core lengths correspond exactly to the set cutting width. By means of freely selectable correction dimensions, the lengths of the cores can be designed so that they vary by a certain amount compared to the cutting widths.
Pneumatically operated knife holders for the sleeve piercing station are equipped with sharpened knives on both sides, which are set in rotation by the driven cardboard sleeve.
The scaled depth adjustment allows the vertical stroke of the knife holder to be set precisely. When using two or more knife holders, it is ensured that the repositioning for the longitudinal cuts and the sleeve separation are completed at approximately the same time.
- Precise cutting with excellent cutting edge
- Improved manufacturing tolerances
- optimised blade life
- Turning by cycle possible if required