Grinding Rolls for SENDZIMIR Mills - THE ELECTROCROWN ^tm WAY

Steel strip entering a Sendzimir Mill is thicker in the middle than at the edges, and must exit the mill with a uniform thickness across its whole width.  This is achieved by the "bending" of the small diameter work rolls so they match the profile of the incoming band.  This 'bending" is achieved by the ground shape of the larger first intermediate rolls in contact with the work rolls.  Shaping these rolls is the job of skilled operators using a special cylindrical grinder with a sine bar attachment.  The grinder supports the roll to be ground on conical points, or "centers" at both ends of the table. The table is supported on a carriage which traverses the rotating roll past the grinding wheel, producing a new cylindrical surface on the roll. This table is fixed to the carriage by a pivot bearing in its center. By continually swiveling the table about its pivot, as the carriage traverses past the grinding wheel, a predetermined shape is produced.  This shape is often called a "taper" in the steel mills.

Prior to the development of the ELECTROCROWN system, this swiveling had been achieved mechanically, requiring a detailed and conscientious setup by the grinding machine operator. The ELECTROCROWN system consists of a precision screw jack operated by a servo motor which swivels the table in extremely fine increments. The servo motor is computer controlled, in a way to cause the roll to be ground to an exact shape programmed in the motion controller.  Up to 25 different shapes can be stored and selected.  Shapes can be added to the list at the grinder. If the program for a new shape is not within the parameters of the grinder, then the program will not be accepted.
 

The requirement is to grind two bottom and two top rolls to the same diameter and shape.  Using the conventional sine bar method, it is the practice to grind the two bottom rolls straight, allowing enough stock removal to ensure that the taper cleans up. The sine bar is then set to the required angle to allow the taper to be ground on each roll.

Using the ELECTROCROWN method, the straight part and the taper are ground simultaneously, which gives the following advantages over the sine bar method:

1. The operator only has to decide which of two is the most badly worn. There is no guesswork as to how much extra stock will have to be removed to cleanup the taper.

2. Minimum skills are required to obtain the roll shape selection, ensuring consistent roll shapes independent of the operators setup skills.

3. The roll shape will be relative to the end of the roll, independent of the depth of the center hole in each roll. This is not true with the sine bar method.

4. The marks caused by the work rest shoes rubbing on the straight diameter while the taper is being ground are no longer a problem.

5. The ground finish of the very important intersection of the taper and the straight diameters will be identical, as roll speed, traverse speed, grinding wheel speed and wheel condition will be identical.

6. The rolls only have to be lifted in and out of the machine once instead of twice which reduces the fatigue on the operator.

7. The substantial time required to look up the sine bar setting for a particular taper, loosen the sine bar clamp screws, swivel the sine bar to its required position, clamp the sine bar in its new position, and disengage the manual table alignment mechanism, is not required with the ELECTROCROWN system.

8. The ELECTROCROWN system makes it practical to grind shapes not possible with the sine bar method.

9. A relatively inexpensive modification to a standard universal grinder makes it unnecessary to have an expensive sine bar grinder to obtain the benefits of the ELECTROCROWN system.

Electrocrown 2001 offers the latest motion control technology for replacing mechanical roll grinder systems or upgrading Electrocrown systems of 1991 vintage. The system is comprised of a high precision mechanical screw-jack that swivels the table, an encoder that measures the carriage position and an electronic control.  The result is Tighter Tolerance Rolls in Less Time:

An operator interface terminal, OIT, allows instant selection of the roll-to-be-ground, by selecting a function key then the number of the roll.  For instance, #1 might be a 7 bottom; #2 a 7 top; #3 a 13 bottom, etc.  When the roll number is selected, the OIT enunciates the roll in simple English, i.e., 0.007 TAPER - BOTTOM.  Twenty-five profiles are available; however, more can be added.

A programming mode is available to allow introduction of parameters for each individual type of roll. A password is required to access this mode.  We furnish the systems "loaded" with current programs to suit the application.

The control is in it’s own small NEMA 12 enclosure, mounted on the carriage.  It connects to the mechanical assembly via connectors, thus easily exchanged for a full spare.  In the rare event that a problem occurs, it could be returned to us for a fix, or connected up to the spare encoder and servomotor/resolver and troubleshot at your facility.  A users manual is provided containing elementary electrical drawings, motion control and OIT programs, on paper as well as floppy disk for archival use.  We can install the motion control, and OIT software on a notebook computer of your choice, for maintenance purposes, as well as providing the software on CD ROM or floppy disk format.  Both will run on Windows 95, 98 or an NT operating system.