Simulator STARCELL Glossary
LOADING AND RUNNING STARCELL SIMWORK.DAT The
data file containing the simulation runs conditions and the cell configuration/operator assignments. The file contains the information entered using option F3 and F4 in the MAIN MENU and is always named SIMWORK.DAT. The data file containing the job routing and workstation information. This `routing file' contains the information entered using options F1, F2, and F5 in the MAIN MENU. Also you may select any other file name for the routing data, instead of SIMPRO.DAT
SIMPRO.DAT
DEFINE A MANUFACTURING WORKCELL
JOB NO.
Is a simple incremental numbering of the part routing in the order that they are entered Defines the parts to be run through the cell into family types or subgroups. The family groups will be denoted as Family Type A, Family Type B, up through Family Type T. Up to 20 Family Types are allowed.
FAMILY TYPE
ANNUAL DEMAND Is the total number of pieces of that part (i.e. routing) the cell is expected to produce in one year's time. BATCH SIZE Is the number of pieces that will be processed through the cell each time a job lot is run. SETUP TIME Is the time (in minutes) required on each machine (or process) in the workstation to change over from one job to the next job. Is the time (in minutes) required to process an individual work piece on any machine in the specified workstation. Cycle times may be entered with a maximum accuracy of three places to the right of the decimal point. the output side of a workstation before transport to the next operation. (1 < Transfer Batch < Batch Size) The Transfer Batch also must be smaller than the buffer size at the next workstation.
CYCLE TIME
TRANSFER BATCH Is the number of pieces to be accumulated as a `unit load' at
LOAD TIME Is the time (in minutes) required to load a piece into a machine (or process) for processing. STARCELL assumes that the operator will perform this loading task. If part loading is accomplished by using automated equipment without operator invention, then it is recommended that a load time of zero be entered, and the corresponding (automated) loading time (if any) be added to the cycle time for the operation. UNLOAD TIME Is the time (in minutes) required to unload a finished work piece from a machine to some predefined out going location.
EFFICIENCYIs the ratio of standard time for a given operation compared to the actual time required to complete the operation, expressed as percentage. SCRAP RATE Is the percentage of bad parts produced for every 100 good parts entering into the designated workstation.
DOWNTIME FACTOR Is the percentage of time that the machine or machines comprising the workstation are unavailable for processing due to breakdowns. For example, if a machine lost 100 hours a year on a one-shift basis (2000 hrs/yr) due to machine breakdown, then a down time factor of 5% should be entered. Note that machines only breakdown when they are in operation; idle machines do not breakdown. NOTE: If you enter a downtime factor value other than zero, be sure to enter a corresponding repair time greater than zero. Otherwise, an illogical situation will occur, causing STARCELL to stop SETUP TIME REDUCTIONis a factor used to evaluate the JIT effects of reducing the setup times on all machines in the workstation. STARCELL will decrease the setup time specified in the job routing by percentage factor entered for setup time reduction. The setup time reduction factor is useful for sensitivity analysis once a cell configuration has been designed. For this reason, it is recommended that the setup time reduction factor be specified as zero for the initial design evaluation of a cell. REPAIR TIME is the average time (in minutes) required to repair a machine and return it to a state of operation once a machine breakdown has occurred.
DEFINING SIMULATION RUN CONDITIONS
SEED NUMBER FOR JOB SELECTION Is an arbitrary user-selected number to prime the random number generator, which is used to randomly select jobs from the routing file for processing through the ct the same sequence of jobs. The purpose of the seed number is to allow you to replicate the simulated performance of the cell under identical design configurations but with a different job stream of work to be processed. The use of replication is very important to test the sensitivity and variability of the cell under different conditions, which will occur in the actual environment It is recommended that you choose a given seed number in a consistent manner to represent a give stream of jobs. You can then have a set of seeds for replication of the cell under identical design considerations, the only difference being the stream of jobs going through the work cell. For example, seen number 100 may represent job stream 1, seed number 200 may represent job stream 2, and so forth. If you do not want STARCELL to randomly select the jobs to be processed, then select the Y (yes) option to parameter #13. SEED NUMBER FOR JOB ARRIVAL TIME is an arbitrary user-selected number to prime the random number generator, which is used to assign a time between jobs entering the cell. You may select any number between 1 and 1000. The inter-arrival time between jobs is negative exponentially distributed with truncation. It is well known that the exponential distribution for inter-arrival time may often evoke unreasonable inter-arrival times such as very long or short times. Thus, STARCELL uses a truncated range of [0.1,0.9] for the random number generated. STARCELL assumes that jobs arrive at random according to a Poisson process. It can be shown mathematically that Poisson arrivals have inter-arrival times which are distributed as a negative exponential distribution. OUTPUT FILE NAME is the name of the file in which the performance reports of the simulated results will be stored for later printing or listing. The default file name is REPORT. You
may wish to specify different file names to store the results of the different simulation runs. INPUT ROUTING FILE NAME is the name of file containing the routing and workstation data for which a simulation analysis is desired. This file was created using MAIN MENU option F1: Input routing information. SCREEN ANIMATION REFRESH TIME (HRS) is the time interval for displaying the state of the simulation run in the cell animation or histogram modes. For example, if the refresh time is specified as one hour, the screen during animation will display the current state in the cell every hour of simulated time. If you wish to see the effect of every change of state in the cell, then enter a value of 0.00 for the refresh time. SALES ANNUAL GROWTH FACTOR PERCENT is a parameter to evaluate the effect of growth (or decline) in the annual sales of all parts processed by the cell. For initial runs in designing and evaluating the cell, an annual growth factor of zero is recommended. This particular feature of STARCELL is more appropriate for doing sensitivity analysis once a cell configuration has been determined. For example, if you wanted to estimate the effect on cell performance of a 15% increase in the sales of all the parts processed by the cell, then enter a value of 15.0 and run STARCELL. The effect specifying an annual sales growth factor is to increase (or decrease if the percentage is negative) the annual usage values for all the parts. REDUCTION FACTOR PERCENTAGE FOR ORDER QUANTITIES is a parameter to evaluate the JIT affects of reducing order quantities. The reduction factor specified is multiplied by the order quantity values given in the routing file. For example, specifying a reduction factor of 50% for order quantities would show the effect of increasing the order frequency by two and reducing the batch size by exactly of the value initially specified in the routing file. This factor is normally set to zero for initial design and evaluation of the cell, and is used primarily for sensitivity analysis of a given a cell design. NUMBER OF DAYS TO SIMULATE is the number of simulated days of activity for the simulation run. For example, if you wish to simulate one week of activity, then 5 (days) should be entered. The days to simulate are calendar days and are
independent of the number of hours (or shifts) that the cell will be operated per day. The value specified for the number of days to simulate must be equal or greater than the value specified for parameter 10 "frequency of summary reports". NUMBER OF JOBS TO PROCESS is the number of jobs to be processed before the simulation is terminated. This is an alternative way of specifying a length of simulated run, as opposed to the number of days to simulate. For example, if you specified 5 days (item 8) and 60 jobs for the simulation run, STARCELL would terminate processing at the minimum of these two values. FREQUENCY OF SUMMARY REPORTS IN DAYS specifies the frequency at which summary data from the simulation run will be accumulated and written to the output file for subsequent printing of simulated cell performance. MACHINE SETUP POLICY specifies one of two policies for controlling how machines in a multiple machine workstation will be setup. If all machines in a workstation should be setup to process a job, then enter a value of 1. If only one machine in a workstation should be setup for a job, then enter a value of 2. JIT RUN LENGTH (days) USING SPECIFIED JOB SEQUENCE allows you to select a special JIT operating policy whereby exactly one batch size of a specified set of jobs will be processed during each Run Length (in days). This mode, the number of hours of operation per Run Length will vary depending on the length of time required to process each batch of jobs. Once the required number of pieces for each specified set of jobs has been processed, the simulation clock will advance to the next period until one of the simulation-terminating conditions (specified in item 8 and 9) If you select the "JIT RUN OPTION" (by entering Y), then you must also select the "USER SPECIFIED JOB RUN SEQUENCE" option described in item 13. The most common JIT Run Lengths would be either 1 days or 5 days (one week). For example, if you specified one day, STARCELL would run until the required number of pieces (for the specified jobs) were completed. It might take 16.7 hours one
day, 15.3 hours the next day, etc. once the required number pieces is made, processing will terminate, and STARCELL's clock will advance to the start of the next JIT Run Length time interval and continue simulating until one of the simulation terminating conditions is reached. USER SPECIFIED JOB RUN SEQUENCE allows you to specify the sequence of jobs to be run. A sequence of up to 45 jobs (i.e. part numbers) can be specified. A given job sequence will cycle until the minimum condition specified in items 8 and 9 above is reached. If the run sequence is specified, the jobs are released into the cell one immediately after the other from the external FCFS arrival queue. If you do not wish to specify job run sequence, enter N [no] and STARCELL will automatically and randomly determine job sequence based upon item 1. If you wish to specify a job run sequence, enter Y [yes] and then use the down arrow key to move the cursor to the next line for entering the job sequence. Key in the part number of the first job in the sequence and then use the right arrow key to advance to job sequence #2, and so on as desired.
DEFINING WORKSTATION CONFIGURATIONS, ASSIGNMENTS BUFFERS, AND OPERATOR
WORKSTATION [A/M] TYPE specifies the type of processing (either automatic operation or manual operation) for each machine in the workstation. In automatic operation, once the part is loaded and the cycle start button is hit, the machine can run automatically without the need for an attendant operator. Machines specified as manual operation require the attention of an operator throughout the processing cycle; setup, load, cycle, and unload. MACHINES (M/C's) IN A WORKSTATION (W/S) specifies the number of identical machines in each workstation. WORKSTATION WORK TIME shows the number of hour per shift that each workstation and its member machines are available for processing work. Any time value between zero and the number of working hours per shift can be specified for each workstation. BUFFER SIZE MAXIMUM AND RESTART LEVELS specifies the size of the inter-workstation buffers or queues. Two values are
specified; the maximum level at which a buffer can be filled to and the restart level. The restart level is defined as the queue level at which the machine directly upstream from the capacitated buffer is allowed to restart processing. OPERATOR ASSIGNMENT specifies those workstations at which an operator can perform setup, part handling, and processing operations for the specified shift. Once the number of cell operators is specified, the screen shows a matrix of each workstation versus each operator. An operator is assigned to workstation by placing an X in the appropriate location or element of the workstation/operator matrix. The letter O is entered if the operator is not assigned or allowed to work at a given station. Reference: User's Guide to STARCELL : A Simulator for Manufacturing Cell Design and Evaluation, Madison, WI. : H.J. Steudel, 1989.