Roll Grinders - Traversing Grinding Saddle

Distinct features of the upper and the lower carriage are thermostable and wear-resistant double V-guideways. They have a self-centering effect on the grinding head and absorb torsional forces during grinding particularly well. The grinding head is always ideally guided when machining big rolls (grinding head retracted) and smaller ones (grinding head extended). That results in consistently high grinding quality on the roll. Thanks to the combination of hydrodynamic and hydrostatic spindle lubrication, Herkules achieves a minimal bearing play for both very high and very low revolutions per minute and thus a precise positioning of the wheel under changing load conditions.

The combination of hydrodynamic and hydrostatic spindle lubrication means that the machine benefits from the advantages of both lubrication systems. The advantage of the hydrostatic part is that it prevents metallic friction, especially during the initial and final stage of the grinding spindle operation. The hydrodynamic lubrication produces an oil pressure of 750 bars, which would be impossible to reach with hydrostatic lubrication. This ensures that the grinding spindle is always positioned right in the centre of the rotation axis/bearing axis, regardless of load conditions.

The Z-axis has a backlash-free master/slave drive. For fine feeding, the C-axis is designed as a tilting axis. In the curve grinding mode in particular, the tilting axis refines the wheel feed in the direction of the X-axis by a factor of 40 to the fraction of a µm. Typical mechanical disruptions such as the stick-slip-effect as well as any kind of reverse backlash are ruled out.

The headstock is designed as an iron-cast housing in one single piece that remains torsion-resistant and dimensionally stable even under highest load.

The tailstock is also made of high-quality cast iron. It ensures the precise positioning of the roll in Z direction. The tailstock can be equipped with a fully automatic dresser and a device for gauging measuring devices. Further equipment options are a motor-driven longitudinal motion, motor-hydraulic motion of the quill or a chock turning device.

For a stable and vibration-free roll support Herkules offers a wide selection of steady rests which can be customized to your specific roll range, particularly with regard to the steady pad design and lubrication system. The product range includes hydrostatic, hydrodynamic and combined hydrostatic-hydrodynamic steady rests as well as special solutions for grinding with or in chocks.

All grinding machines are also available with a patented Monolith^TM machine bed. The machine bed is torsionally rigid and thermostable. Its sandwich construction consists of an iron-cast, ribbed upper section, fiber-reinforced high-performance concrete and a steel floor panel with special damping elements. As there is no metal connection between the upper and lower section, vibrations are effectively damped. The integration of the workpiece bed and grinding bed into a joint machine bed guarantees permanently precise alignment even after many years of operation.

Monolith^TM machine beds do not require a foundation. Thus, installation costs and set-up space are minimized.

In order to reduce wear to a minimum, the lubrication system of the grinder guideways combines a hydrodynamic and a hydrostatic part. The lubrication of the linear axes and at the grinding spindle bearing is hydrodynamic. Even if machines are used intensively, the running surface needs to be rescraped after 15 years of operation at the earliest. The particularly high pressures of the grinding spindle bearing produce a reliable lubricating film and a permanently wear-free operation. At speeds close to a halt, the hydrostatic lubrication makes sure that there is no contact between the running surfaces.

All control functions are integrated in the HCC/KPM 10 control, which has been developed by HCC/KPM specifically for Herkules grinding machines.

Geometry measuring devices are directly connected to the control without any additional interfaces. The measuring data is therefore transferred very quickly. For operating the sophisticated control functions, the operating system is equipped with real-time data processing (TwinCat). This combination allows for the correction of the grinding operation while the grinding wheel is still engaged – correction on the fly.

High-quality measuring technology is the prerequisite for a precise control of the grinding process and key to achieving perfect grinding results. Herkules offers measuring and inspection systems which are developed and manufactured within the company group:

The C-frame measuring gauge measures the roll geometry at a frequency of one µsec. Per second, 1,000 measured values are registered, processed and evaluated. The measuring probes are placed opposite the center of the grinding wheel so that an absolutely exact image of the current grinding status of the workpiece can be displayed.

The Eddy Current measurement reliably recognizes and locates cracks on the roll surface. Changes in the roll texture and subsequent hardening are detected during the measuring process as well. Since the Eddy Current measuring sensor is integrated in the roll measuring system, measurements are carried out during grinding and therefore without delay.

Manufacturing defects within the roll as well as fatigue from operation in the mill can be detected during a separately running ultrasonic inspection. The ultrasonic inspection detects possible cracks below the roll surface/in the barrel up to a depth of 250 mm. A typical application of ultrasonic technology is the inspection of compound cast rolls where the critical transition lies between the shell and the core of the roll.

The Roll Surface Inspection System registers and records the reflexion of a laser beam on the roll surface. Special image evaluation software detects and displays roll surface defects such as chatter marks and feed lines, commas or combinations of these and defines their location. The system also detects defects occuring only once.

Areas of application of Herkules roll grinders can be expanded by a turning device. Again, Herkules offers a variety of different options:

• Basic turning device
  The turning device is mounted on the grinding head, not the grinding spindle. It is particularly suitable for machining coated paper rolls. In hot rolling mills, it proves excellently suited for turning edger rolls in roughing stands.
• Special turning device
  The machine is equipped with a turning saddle that is mounted separately on the grinding table. This turning saddle was especially developed as an additional device for heavy-duty roll grinders used for turning paper rolls.
• Turning device for heavy-duty machining
  In order to achieve a more substantial stock removal, the grinders can be equipped with a special turning saddle that is mounted on the backside of the machine.

Herkules has successfully developed a grinding technology that uses CBN wheels in cooperation with the Austrian grinding wheel producer Mach Rotec. The combination of Herkules grinders, HCC/KPM controls and measuring devices and Mach Rotec grinding wheels ensures reliable and repeatable grinding results.

By achieving greater stock removal in shorter grinding times, Herkules MACHtechnology saves substantial time. Optimizing stock removal significantly extends roll service life. Further advantages are absolutely homogeneous, flawless surfaces along the entire roll as well as high energy efficiency.

On request Herkules roll grinders are delivered with automation systems. The machines must be equipped with the latest version of our CNC control for that. All conceivable automation features can be combined – from measuring and inspection systems to fully automated roll loading systems. Such tailored solutions make each Herkules grinder unique.