7 October 2003

P.Comand; F.Martecchini; Luca Zorzi

Published on MPT International 2/2003

INTRODUCTION

A streamlined roll shop is of strategic importance for the overall efficiency of a bar mill. Roll shop management affects roll inventory level, plant downtime and man hour requirement. Often the entire production planning depends on the roll shop results. Optimization in this area includes:

1. Efficient inventory control.
   
   
2. Minimization of time requested for each operation of roll redressing.
   
   
3. Easy and controlled data processing.
   
   
4. Easy, reliable and recordable quality checks.
   

The new ROLLWORK software for Atomat CNC machine, is based on a revolutionary concept it integrates the programming of the roll maintenance machines, with a software designed to manage the roll shop inventory.

Intended to simplify the programming of CNC grinding machines and assure an error-free processing of roll redressing operations, the new software includes a database for the roll stock which automatically updates the roll data after each operation.

The software is able to handle a network of machines to include all the maintenance operations on the rolls. The same software runs an automatic control tool for profile checking after roll grinding with data storage and processing for quality control purposes. The software is a simple, easy-to-use tool for managing a powerful roll database and running all the three basic operations of a roll shop, i.e. Turning, Grinding and Notching. This paper analyses the application of the new ROLLWORK software in connection with AT 700 series grinding machines.

AT 700 E CNC GRINDING MACHINES

The AT 700 E CNC series grinding machines (Fig.1) are specially designed for tool shops in the modern rolling mills. These specialized machine are designed for a wide range of applications, from the grinding of Tungsten Carbide rolls of no twist finishing blocks through to large composite cylinders.

All machines are equipped with SIEMENS 840 D control and a modem for remote assistance. Rolls to be ground are fixed in a main shaft running on ball bearings, designed to offer the maximum rigidity. Thanks to the hydraulic clamping device the small 6" and 8" rolls can be changed very quickly to reduce machine down time.

Rotation of the workpiece is assured by a SIEMENS brushless Digitally Controlled motor with infinitely variable speed. Headstock is fixed to the bed through strong prismatic guides. This to assure that even operating with maximum load, no deformations will occur to jeopardize the consistent accuracy guaranteed by the machine. Since the wheel can move on two axes, there is no need to move the work piece headstock along its guides. This is a further element of stability and rigidity of this machine.

The grinding wheel head moves on two axis with two brushless SIEMENS digitally controlled motors. Machines can then operate both in contour and plunge grinding modes (fig.2). When operated in the contour mode the machine can perform all possible profiles basically with the same grinding wheel. In order to achieve maximum flexibility, and a maximum degree of automation, as well as minimize the stock of diamond wheels, contour grinding is normally used by almost all the customers.

The strong grinding shaft enables operation with 350mm wheels ensuring a longer service life and less down time for wheel changes. The AC 15kW motor with variable speed ( to give the optimal speed for every application), can grant plentiful power both for Contour or Plunge grinding (Fig.2) and in general machine operates at a very small percentage of this power .

The Computer Controlled movements of the grinding wheel head provide maximum flexibility in the profile grinding. In contour grinding all profile types, including a joining radius, can be achieved by the CNC machine and basically with the same disk wheel.

1.1 APPROACH WITH OPERATOR FOCOUS

In general the majority of problems that confront CNC machine users (operators or maintenance personnel) can be solved by applying the appropriate operational techniques, this means that the first step to reduce the problems associates with the use of these machines is to have an operating software capable of quickly performing self checks for mistakes. Also the possibility of fast assistance and "technical" communication facilities smooth operation.

The assistance and technical communication system, is now an integral part of all Atomat's CNC machines: from all countries customers can at any time obtain assistance in solving operating problems from ATOMAT specialists through the proven teleservice system.

The new ROLLWORK software is an easy-to-use operating software for all operators of AT700 E CNC machines. It is capable of reducing sources for mistakes and inefficiencies due to the use of complicated programming routines in particular when carried out by personnel not trained for this purpose.

2.0 THE ROLLWORK SOFTWARE

ROLLWORK software was developed by Atomat to provide customers a simple, easy-to-use device ready to be used by any operator, even if unskilled in CNC programming or without machine tool experience. Due to the Windows-based environment, using standard dialogs, users easily familiarize with the software. Designed to work on computers with MMC 103 Pentium 64 MByte RAM, the software includes:

1. a database to manage all information of rolls in stock and rolls to be included in stock;
   
   
2. an easy visual editor for groove profiles;
   
   
3. an interface for machine programming;
   
   
4. an interface for automatic profile checking.
   

2.1 A POWERFUL DATABASE

The ROLLWORK database is specifically designed to handle information of physical roll stock.
Information are organized in a hierarchical structure (Fig.3) in order to minimize the data required to be stored when new rolls are stocked. The lowest level of contains the roll grooves units where the geometrical data of all the grooves are recorded. This information is stored only once, at the beginning. A simple editor enables modification of the groove data input of new grooves to be performed at any time. If a parameter of a groove is modified the parameters of all the rolls with the same groove are automatically updated. The intermediate level contains the roll design units, where the roll is defined with by all its grooves as well as the main general data, such as original outside diameter, discharge outside diameter etc. Also the data of these information units are stored only once at the beginning, at the same time enabling easy handling by a simple editor.

At the top level the rolls physically stocked in the plant are unmistakably defined by an identification code. When a new roll is stocked, it can be simply defined by a new code and by the relevant "roll design" that already has all the necessary geometrical info. Date of stocking and other statistical information are recorded automatically. When the roll is ground for the first time, the database automatically chooses the right program, recalls the data of the final diameter to be achieved and selects the working cycles for the opening of new grooves with the correct number of removing passes. At the end of the grinding operation the database is automatically updated with the date and the new final roll diameter.

When the roll has to be ground again, it will only be necessary to indicate its code and the depth of the layer to be removed. The machine will operate fully automatically without any further operator intervention, unless the settings given by the machine are to be changed. Even in this case the data are recorded enabling automatic operation of the machine in the next grinding operations.

The machine automatically indicates when the roll reaches its scrap diameter. When the life cycle of a roll ends, the following information can be retrieved:

1. Date of start up;
   
   
2. Number of regrinding operations;
   
   
3. Average depth of removal for each operation;
   
   
4. Average time for each grinding operation;
   
   
5. Total grinding time (for all the operations).
   

Through the network interface the data can also be utilized by and external PC for statistic purposes or daily data storage.

2.2 AN EASY INTERFACE

ROLLWORK was specifically designed for quick and easy implementation of any operation related to machine and roll management.

To define a new groove, the operator only has to select the groove type. A detailed design indicating all necessary parameters (maximum 4-5) will appear on the screen, and the operator inputs the value for each highlighted parameter (Fig.4). Each input is checked for consistency for the other data, and in the case of wrong inputs an alarm is triggered. At this point the new groove can be codified for any further reference.

A groove already stored can be modified by a simple visual editor. Any change to the groove design will automatically update all the rolls with this code of groove. A new roll design can be defined by a few simple operations: input the roll geometry data, selection of the relevant groove profiles, positioning of the profiles over the roll surface. An existing roll design can be modified in each component by a simple editor (Fig.5) .

Measuring the roll grooves on the machine eliminates the need to move the roll to another device, provides instant feedback of process problems, ensures and certifies that grooves are in accordance with the drawings. An electronic probe, handled by the central control of the machine, automatically and quickly checks the groove profile during the grinding process. The collected data are processed by the machine computer, to determine the groove positions, and to check the groove profile. The screen output is immediately available to the operator. The output can be printed or the data can be stored in files for quality control procedures. The profile check is carried out by spot testing. The number of points to be tested is determined by the operator and is related to the required accuracy. The screen output will show the original groove profile, its tolerance and the positions of the checks points for immediate and intuitive analysis of the results. The same output can be printed to integrate the quality control certification.

3.4 ROLL SHOP NETWORK

The ROLLWORK software is designed to offer the possibility to link all ATOMAT machines installed in the roll shop in a network. Since the ROLLWORK software can handle all the roll shop operations (turning, grinding, notching and marking), performed by Atomat machines, these machines share one database and exchange roll information via a network interface. This ensures that the roll data are always updated no matter what operation is carried out on the roll.

4.0 CONCLUSIONS

ROLLWORK represents a new approach in CNC operation software. In fact it is not only an easy interface enabling simple and reliable programming of roll shop machines and ensuring the automatic profile control. This software for the first time integrates all the roll shop machines with the physical stock of the rolls. A powerful database handles and automatically keeps updated the roll stock and the status of the rolls in stock. At the same time it records and stores a large volume of essential data for statistics on roll life and mill costs.