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A cost comparison for dressing tungsten carbide rolls shows that disposable electroplated diamond grinding wheels are more cost effective than redressable matrix bonded diamond wheels when multiple profiles are to be ground by the contour method but less cost effective if few profiles are required and the plunge method is used.
Tungsten carbide (TC) is recognised by many as the most cost-effective material for bar and wire rod rolls, not only in the high-speed finishing block but also in traditional finishing and intermediate stands.
Demands on the roll shop for re-dressing TC material have thus increased due to the introduction of large composite rolls. In such rolls, TC rings are mounted on cylinders that can have an overall length of up to two meters, as well as large outside diameters. Customers usually perform roll pass grooving by grinding with diamond wheels as this is generally the most economic approach. Roll shops are thus often seeking a single groove grinding machine capable of handling the entire range of dimensions. CNC machines with a traveling wheel-head (two- axis control) are preferred since they are much more compact, rigid and are less expensive. These CNC machines have the opportunity to work with the two grinding methods suitable for pass grinding, ie contouring the groove profile with a disk wheel or entering into the groove by plunge using a shaped wheel.
This paper focuses on groove grinding and, in particular, on the regrinding process. An analysis of the main parameters will be carried out to optimise each operation and offer a guideline for the choice of the most cost effective method.
GRINDING MACHINES
Modern grinding machines are CNC with two controlled axes. The machine must be solid to avoid vibration, while maintaining high accuracies in positioning. In general, particular care must be given to the roll holder and wheel shafts. Some machines allow operation with large grinding wheels (up to 350mm -14''), assuring a longer service life and less down time for wheel changes.
If the machine is designed with a travelling wheel-head, there is no need to move the workpiece headstock along its guides. This reduces the machine's overall length, in particular for machines designed for large pieces up to 2m between centres. This is also a...