Shear Knife Grinder

Precise grinding of long knives in hot and cold rolling mills

Besides single roll machining machines, Herkules also offers complete roll shops as a tailor-made solution from one single source. The development of a shear knife grinder by Herkules is a further expansion of the product range in this field.

When designing and producing the new machine type, Herkules Meuselwitz benefits from decades of knowhow with nearly 2,000 flat grinding machines built here. A high degree of automation, precision, flexibility, reliability and intuitive operation are the most important characteristics of this grinder. Both straight and curved knives can be ground with high precision thanks to flexible programming functions.

An optional rotary table allows for the machining of trimming shears. In addition, the shear knife grinder also grinds all other workpieces, such as adapter disks, rings or spacers.

Pioneering machine technology

+ Machine bed

The double-walled, strongly ribbed welded sandwich construction results in extraordinary rigidity of the machine bed.

The extended side walls carry the rails of the roller guides for the grinding saddle in longitudinal direction. At the same time, the side walls function as a splash protection.

+ Magnetic set-up plate

The table on which the shear blades are mounted is designed as a magnetic clamping plate that can be swiveled by up to +/- 90 degrees. Thus, all shear blades can be machined with the appropriate clearance angles.

The swivelling angle is set either manually or motorically via a worm gearbox. The angle can be preset in the CNC control. The angle setting of the clamping table is controlled directly at the rotation axis via an absolute encoder. After the angle has been positioned, the table is clamped.

The machined workpieces can be easily dismounted thanks to automatic demagnetizing.

The magnetized clamping plate is composed of several segments, depending on the size of the table. Support bearings between the separate segments prevent deflection.

+ Carriage (longitudinal motion)

The carriage is made of high-quality gray cast iron. The linear ball bearing units that are installed at the bottom, combined with the guideways installed on top of the machine bed, guarantee a consistent, backlashfree and smooth longitudinal motion of the grinding saddle.

A three-phase servo motor is used for the longitudinal motion. Transmission takes place via rack and pinion. The traversing speed is infinitely variable. The position of the grinding saddle is automatically identified with the help of a measuring system. A central oil lubrication system supplies all moveable points of contact of the carriage, the cross slide and the grinding saddle.

+ Cross slide (transverse movement)

The cross slide is made of high-quality gray cast iron, as well, and functions as a carrier element of the grinding saddle. The guidance system comprises well-proven guide rails and linear ball bearing units. The transverse movement of the grinding wheel is performed by a three-phase servo motor and a backlash- free, preloaded ball screw. The axis position is constantly determined via an absolute encoder on the motor shaft.

The CNC control allows for programming of intermittent as well as infinitely variable transverse movement of the grinding wheel.

+ Headstock and grinding spindle

The vertical movement of the headstock is performed with the help of a backlash-free, preloaded ball screw and a three-phase servo motor. Emergency retraction is initiated immediately in the case of a power failure, preventing dangerous ejection of tools. A hydraulic system supports the accuracy of the machine during grinding (precision in μ range).

The position of the axis is determined by an absolute encoder on the motor shaft. Vertical infeed of the grinding wheel takes place intermittently.

The CNC control presets both the overall stock removal and the division into rough machining, finishing and sparking out. The entire grinding process is automatically controlled.

The grinding spindle is installed in a housing in precision bearings. A lubrication system that combines special high-performance lubricating grease with a sophisticated sealing air system guarantees lubrication for the entire service life.

A frequency-controlled three-phase motor is in charge of the grinding wheel drive. It is mounted axially parallel to the grinding spindle and drives it via a flat toothed belt.

Before being put into operation, the grinding wheels are statically balanced on a balancing device. The balancing device is integrated in the machine bed and allows for balancing of the grinding wheel according to the diameter, as well as the width.

+ CNC control

The shear knife grinder is controlled by a CNC control of the type HCC/KPM 50. The control has been developed within the HerkulesGroup especially for this application. It seamlessly blends into the range of other machine controls by HCC/KPM. The user benefits from a consistent operating philosophy and the perfect integration of the machines in the roll shop and the optional Roll Shop Management System. The control allows for both manual and fully automatic control of the shear knife grinder.

Rotary table

In addition to the magnetic clamping plate, shear knife grinders made by Herkules can optionally be equipped with a magnetic rotary table for the machining of cutter disks with diameters of up to 500 mm. The speed of the rotary table is infinitely variable.

The shear knife grinders have the following technical data:

  • Grinding length: 1,000 - 5,000 mm
  • Grinding height, max.: 250 mm
  • Grinding table set-up width, max.: 250 mm
  • Swivel range of the grinding table from the horizontal plane: +/- 90 degrees

Accuracies:

Evenness of the ground surface:

  • in longitudinal direction: 0.01 mm/m
  • in transverse direction: 0.005 mm/250 mm
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