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INTRODUCTION
MAIN OBJECTIVE OTHER
FEATURES
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Sendzimir Mill Management SystemsIntroductionThe Mill Management System (MMS) is a set of computer programs which is designed for use by the operator of a reversing type rolling mill, using a computer located at the operator's desk, or nearby. The main program of the set utilizes a mathematical model of the rolling process to generate optimum pass schedules for the mill, and to set up the mill accordingly. Any suitable computer using IBM PC-DOS or MS-DOS operating system can be used, although, for the mill environment we recommend a "ruggedized" machine such as the IBM Industrial PC. Versions of the software are available for operation under DOS, Windows 95 or NT environments. Almost all new installations are Windows based solutions. A printer can be used to record the results of the computation, if desired. Since the program incorporates mill variables (such as Mill Power, Winder Tension, Mill Speed) which only apply to one particular rolling mill, it cannot be transferred to another rolling mill in your plant. We can also supply additional programs for other mills in your plant. Programs are available to work in inch units or metric units. Versions of the software are available for Sendzimir 20-High mills, and also for 6-high, 4-high and 2-high cold rolling mills. We want you to be happy with the software, and, included in our price is a service to make a reasonable number of modifications and refinements during the first year of use, in order to tailor the program to your liking. Speed of Computation - Multiple pass schedules are optimized and displayed within one second normally. The MMS is covered by US Patent no. 4,745,556 and corresponding patents in other countries. Main Pass Schedule Objective
The program has three main routines summarized below: The Optimizing RoutineThe optimizing phase establishes the minimum number of passes needed by the mill to achieve the desired final gauge. A complete optimized pass schedule is computed, where maximum reductions are taken on every pass except the last. The last pass is merely a "fill-in" pass which gets the gauge down to the final gauge from the last optimized pass.
The (iterating) optimizing routine compares Roll Separating Force with the rated Roll Separating Force for the mill, and adjusts the pass reduction to achieve rated Roll Separating Force (using the Roll Pass Schedule routine for each iteration). It then compares the mill power with the rated mill power and adjusts the pass reduction or the rolling speed to use up all the mill power, while not exceeding the rated Roll Separating Force. This routine also limits the pass reduction as required to avoid skidding or chatter, and to keep the reduction within limits imposed by the Production Department (usually determined by considerations for strip flatness or surface qualities). The Rationalizing RoutineTo obtain a balanced rational pass reduction schedule, which is necessary in a practical rolling situation, the program repeats the last four passes of the above optimized phase, but with pass reductions adjusted to equalize (substantially) the Roll Separating Force on these passes. This not only helps to produce a flat product, but will also result in a slight increase in rate of production.
The rationalizing phase thus establishes a new schedule using the same minimum number of passes established in the optimizing phase, but with the last four passes balanced for Roll Separating Force. The Upgrading RoutineAfter any pass has been taken on the rolling mill, if, for any reason, the operator does not achieve the exit gauge specified by the computer, and achieves either a greater or lesser gauge, the computer generates a new optimized schedule for the remaining passes, by running the optimizing and rationalizing phases again when the pass is advanced.
The upgrading routine is of vital importance in any mill management program, since there are valid reasons why the computed schedule cannot be achieved in some instances. Possible reasons are:
Running the ProgramAll the programs can be selected from the menu (DOS system) or the application can be started automatically when the computer is switched on (Windows systems). In DOS systems, selection of pass schedule program will bring up a data entry screen. After the data is edited, the pass schedule is computed and displayed. In Windows systems, a list of available coils is presented. Selection of the next coil from this list causes the pass schedule for the next coil to be computed when the current coil is completed. If the exit gauge is altered by the operator at any time during the pass, then, when the pass is advanced (by changing the mill direction), the computer prepares and displays a new rationalized schedule from that point on, highlights the next pass and sends the new exit gauge value for the pass to the exit thickness gauge, and the new tensions and speed to the drive system. If the exit gauge is not altered during the pass, re-scheduling is not required, and the computer simply highlights the next pass and sends the new gauge and tension values as before. On the final pass, it is still possible for the operator to change the target gauge. This may be required, for example, when the strip thickness on the final pass is being checked and it is found that there is a gauge calibration error. In this case the target gauge can be offset to eliminate the error. Note that the operator never has to guess intermediate gauges - they are always given by the computer to ensure maximum reductions the mill is capable of, together with balanced reductions on the last several passes. The computer will generate a gauge deviation chart on the screen, so the operator and management have an immediate visual picture of the gauge performance during rolling. This is usually done on all passes. The computer stores all the gauge data on the final pass (usually 1 value per ft. or 1 value per meter of strip) for subsequent analysis and printing of coil reports. The operator can select gauge chart screen or schedule screen at any time (function key selection). If desired, the incoming gauge data for the first pass can be displayed and stored, enabling reports on the quality of the incoming coil to be generated. Other Features of the Mill Pass Schedule Program
Roll Utilization ChecksOn Sendzimir ZR mills this program remembers roll and bearing sizes currently in the mill, gives operator allowable roll size ranges, checks that current roll sizes are safe, and gives operator correct side eccentric and lower screwdown settings. On Z-High mills the program checks all clearances in the cluster and determines the correct side support spacer set or setting to be used, based upon current roll sizes in the mill. The program also gives correct passline settings for Z-High mills and for 4-High and 2-High mills Gauge Charts & Statistical Gauge AnalysisUsing an interface (such as an RS-232C link) between mill management computer and AGC system or thickness gauges, successive gauge values during a pass are transmitted to the Mill Management computer and stored on the computer's hard disc, in the form of coil report files. After rolling of the coil, SPC (Statistical Process Control) analysis can then be done if desired either by operator selection using the above menu, or automatically. This analysis is done by the Mill Management software and printed out as a coil report. The exact SPC analysis method can be customized to your requirements, or a standardized program supplied. SPC analysis can also be done on incoming coils. If desired, the coil report files can be transferred to a remote computer using an ethernet connection and the SPC analysis and print out of coil reports done on this machine rather than on the Mill Management Computer. Viewing & Storage of SchedulesThe operator is given the option of storing schedules during operation of the mill management program so that he can subsequently recall any schedule he needs to use. The number of schedules that can be stored is virtually unlimited (over 1000). In general, schedule storage is only needed in the first few weeks after startup of the MMS. Once the operating parameters have been defined correctly, it should no longer be necessary to store & recall schedules. To check if any particular schedule has been rolled before the operator selects "viewing of stored schedules" while the menu is displayed, and the schedules can then be viewed according to the material, and the desired schedule selected when running the Mill Management program. Note that if a schedule is recalled and displayed, and the operator misses a gauge on any pass, the Mill Management computer will reschedule the remaining passes as required. The Windows version provides for automatic sorting of stored schedules. On Line Operation - Integration with Other SystemsWithout the interfaces, although the MMS Computer display informs the operator the correct settings, he has to set the values manually on the respective system. This makes more work for the operator, so is not too effective. For this reason, nearly all systems today are "on-line". For on-line operation interfaces are provided (such as RS 232C links) between the MMS computer and the AGC system and mill drive system, the MMS computer operates "on-line" and can provide the function of supervising the entire mill operation. It will then send command signals:
It will also plot gauge deviation charts and store raw gauge data in the form of coil report files. It is also possible for the system to adapt itself to the characteristics of the material being rolled in order to refine the optimization. If mill power, RSF, speed and tension values can be obtained by the system (for example via analog or serial interface from the mill drive system) the system will compare these with theoretical values and update the resistance to deformation curve for the material being rolled accordingly. Such adaptation, in order to avoid the effects of short term scatter, is performed slowly, with measurements averaged over a large number of coils. It is also possible to provide for supervision by not updating the curve until the MMS supervisor approves. The MMS computer would also normally sense when the operator changes mill direction on the mill desk, and will advance the pass accordingly (i.e. set thickness gauges, and send new speed and tension values to the mill drive system). For digital drive systems serial links are usually provided between the MMS computer and the drive. For analog drive systems the MMS computer incorporates analog I/O boards, and can send the necessary reference voltages to the drive to set speed and tensions. Network OperationSystems have been supplied which operate on networks - this enables uploading and downloading of data to the MMS computer. For example coil data can be entered on the production control department computer and the operator's selection of a coil number at the mill will automatically load the required data (such as material, width & gauges) into the MMS program. Furthermore, the coil report files generated by the MMS can be immediately accessed on the quality control department computer. Because the raw gauge data (for example one value of strip thickness per meter for the entire length of the finished coil) is stored in the coil report, the optimum end trim length can be determined by quality control dept. using our SPC software. This software allows the coil ends to be "trimmed" and the gauge chart and SPC analysis to be displayed (or printed) for the "trimmed" coil. The MMS computer can either be located on a PC network, or on a VAX network, using standard hardware and software (Pathworks) supplied by DEC. The normal arrangement is to have a keyboard and monitor for the MMS computer located at the rolling mill. However, the keyboard and monitor can be completely eliminated in cases where the mill operator uses a single VAX terminal at the mill. In these cases, the supplier of the software for the VAX system would have to supply the software for data entry and pass schedule display (we would provide PC source code to this supplier). Another approach is to use a PC running "WINDOWS" or "OS/2" as the operator interface for AGC or drive system, and to run the MMS software on this PC. |