Shop floor performance management is a method to ensure the effective utilization of people, processes, and equipment. Changes in the shop floor might have a positive or negative effect on production performance. Therefore, optimal shop floor operation is required to enhance shop floor performance and to ensure the longterm efficiency of the production process. This work presents a case study of a semiconductor industry. The punching department is modeled to investigate the effect of changes in the shop floor on production performance through discrete event simulation. The effects on the throughput rate, machine utilization, and labor utilization are studied by adjusting the volume of parts, number of operators, and flow pattern of parts in a series of models. Simulation results are tested and analyzed by using analysis of variance (ANOVA). The best model under changes in the shop floor is identified during the exploration of alternative scenarios.
The fierce competition in the manufacturing industry has become an important issue in developing an effective and efficient shop floor. However, most companies in this industry are challenged by shop floor changes, such as unstable customer demand, alteration of part flow routing, and different numbers of operators assigned. Soh et al. [
To investigate the positive or negative effect of changes in the shop floor, a company has to assess shop floor performance. As reported by Panjehfouladgaran et al. [
Simulation is defined as the emulation of realworld processes or system operations over time [
Shop floor changes are unavoidable in the manufacturing industry. Thus, the effect of these changes on shop floor performance should be studied before implementing any appropriate solution. DES can be used to measure shop floor performance. In most studies, DES outperforms continuous simulation [
Owing to the limited use of DES in shop floor performance measurement [
A systematic procedure will be used to study the effect of changes in the shop floor on performance measurement through the application of DES. Figure
Systematic procedure for DES model development.
Shop floor analysis is the primary and essential step in the whole DES procedure. A detailed shop analysis has to be completed to gain a better understanding of the working environment before developing the simulation model. The collected data will be applied in the simulation to emulate realworld operation processes without disrupting the system. Thus, the required data that should be collected from the shop floor include machine cycle time, setup time, customer demand, types of parts, and part routing.
A model is developed by using WITNESS simulation software. It is a computerized simulation system designed for modelling manufacturing operations [
Before proceeding to the experimental design phase, an accurate model that emulates the realworld system is crucial because the results obtained from the simulation should represent realworld scenarios. Therefore, experimental runs are systematically designed to study the effects of changes in the shop floor on the identified performance measures. By incorporating various experimental parameters, simulation runs can be conducted to emulate realworld operations. Performance measurement is a quantifiable indicator used to assess system performance, whereby the measurement criteria can be obtained from the statistical report generated from the simulation. The shop floor performance results obtained from the simulation are tested and analyzed through oneway ANOVA. ANOVA is applied in this study to test and analyze the effect of changes in the shop floor on its performance by rejecting the null hypothesis (H_{0}) or accepting the alternative hypothesis (H_{1}). A graph can be plotted to verify whether the sampledata relationship is significant. The base model can be compared with the alternative models on the basis of the graph. Managers can decide on the best solution from the experiment in accordance with the different measurement criteria.
The case study is mainly focused on the punching department of a circuit board manufacturing company that produces singlesided and doublesided printed circuit boards. The machines are divided into processbased groups, namely, the incoming and looping section groups. Given the complexity of the flow of operator, materials, and parts, the performance of these identified variables should be assessed regularly. Changes in the shop floor might affect production performance positively or negatively. Thus, the optimality of shop floor performance should be aligned with dynamic daytoday changes. In this case study, DES is used to measure the effect of the changes in the shop floor on shop performance. Upon completion of DES, the previously discussed systematic procedure for DES model development will be adopted and further elaborated in the subsequent sections.
Understanding the shop floor is important, especially during data collection. As previously stated, the machines in the punching department are classified according to the process grouping structure. The proposed shop floor has 17 machines, which are divided into the incoming and looping sections. Each machine is manned by an operator. The incoming section is referred to as the process flow, in which a part enters the department in “one time” to undergo the punching process. The part then proceeds to the adjacent department for further processing or is sent to the customer as a completed part. For the looping section, the part will be sent to the testing department. Once testing is completed, the part will again enter the punching department. The remaining processes will be completed. Similar to the incoming, completed looping is sent to the adjacent department for further processing or to the customer as a complete part. Figure
Process flow of the incoming and looping sections.
During the shop floor operation, the part will either pass through the machine in the incoming section and then proceed to the looping section or will pass through the incoming section only. This indication implies that all parts will go through the incoming section, but not all parts will go through the looping section. All parts will arrive at the storage area of the punching department simultaneously. Subsequently, the parts will be distributed to the available machines in the incoming section according to the process and type of machine used. The part will flow from right to left; for instance, the parts that have undergone Line 1 in the incoming section will pass from E1 to E2. In addition to conducting the flow analysis, data will be collected to obtain such information as machine cycle time, setup time, customer demand, type of part, part routing, and working time per shift. The collected data will be used for developing simulation models and manual computation. Working time per shift, demand ratio, and output per shift are manually computed. This manual computation aims to ensure that the output reflects the outcome for the daily basis of running the shop floor.
Once all the required data and the shop floor are identified, the details are entered into WITNESS simulation software. A number of assumptions are made during the development of the simulation model.
The process flow for the simulation is continuous.
Production is in an ideal situation, in which no breakdown occurs and no product quality problem exists.
An equal ratio of volume exists for each part.
All the parts arrive randomly, and the parts will go into a certain machine when available.
The operator moving time between workstations is assumed to be constant.
The machine cycle times are assumed to be the same for both singlesided and doublesided parts.
The production plant runs six days a week with two shifts per day.
After simulation model development, verification is conducted to determine whether the developed shop floor reflects the realworld scenario. The model is verified by evaluating whether the simulated output is within the acceptable range of the calculated output. The changes in the shop floor included alterations in the volume of parts, number of operators, and flow pattern of parts. The volume of parts is based on the customer demand. The purpose of different flows is to examine whether the flow patterns behave in a manner similar to those in the real world. In addition, the effect of the reduction in the number of operators on shop floor performance is also considered as a parameter to verify the developed simulation model. Once verification is completed, the number of performance criteria and experimental parameters will be identified. The measurements for the performance criteria and experimental parameters selected in this study are used as the gauging mechanisms during the experimental setup. The experimental parameters used in this study include the volume of parts, number of operators, and flow pattern of parts. Three measurement criteria were considered: throughput rate, machine utilization, and operator utilization. The three performance measurement criteria are discussed in detail in the following sections.
Experiments were conducted to study the effect of changes in the shop floor on the shop floor performance. Seven models were developed by considering different conditions, as indicated in the Simulation Model Development section. All models have the same number of machines with a base model set as a benchmark for comparison. The differences of the models were based on the volume of parts, number of operators, and types of flow pattern. Table
Information on the different models used in the experiment.
Model  Parameters  Remark  With respect to  

Flow pattern  Number of operators  Volume of parts  
Base model  F1  17  Low  Benchmark  


Model 1  F2  17  Low  Experiment 1  Flow pattern 
Model 2  F3  17  Low  


Model 3  F1  10  Low  Experiment 2  Number of operators 
Model 4  F1  9  Low  


Model 5  F1  17  Medium  Experiment 3  Volume of parts 
Model 6  F1  17  High 
As shown in Table
Flow 1.
Flow 2.
Flow 3.
Shop floor performance is also affected by the number of operators. In this case study, the ratios of the number of operators to the machine are set as 1 : 1 and 1 : 2. A total of 17, 10, and 9 operators are tested to examine the effect of the reduction in the number of operators on the production performance. In the case of an operatortomachine ratio of 1 : 2, 10 and 9 operators are used. The allocation of 10 operators is based on the line, whereas the assignment of the 9 operators is based on the nearest machine. This experiment describes the significance of reducing the number of operators relative to production performance by using the base model, Model 3, and Model 4, where the ratios of the number of operators to the machine are 1 : 1 and 1 : 2. In Model 3, the number of operators is reduced to 10, and operator allocation is based on the line. For example, an operator is assigned to Line E, which consists of two machines in the incoming section. By contrast, the operators in Model 4 are allocated to the nearest machine, which means that the two nearest machines are operated by only one operator. Model 4 has nine operators with an operatorstomachine ratio of 1 : 2 (the same as Model 3). For the base model, one operator is assigned to one machine, as proposed.
The preceding experiment considered the volume of parts on the basis of customer demand. The demands are categorized as low, medium, and high. Each demand represents the different volume of parts on the shop floor. The ratio of the volume of parts under low demand with respect to medium and high demands is 1 : 4 : 7. The effect of different volumes of parts on production performance is demonstrated in Experiment 3. Three types of customer demand are given: low, medium, and high. The demands for the base model, Model 5, and Model 6 are low, medium, and high, respectively. The flow pattern of parts and the number of operators remained the same as in the case of the base model. The ranges of the low, medium, and high demands are defined in Table
Volume of parts for each demand.
Demand  Volume of parts (lots) 

Low  1050 
Medium  4200 
High  7350 
The simulation runs started subsequent to the determination of experiment parameters. The data and information required for the simulation are the machine cycle time and setup time, volume of parts, type of process and machine involved, number of operators, working time per shift, and part routing. To reduce the gap between the virtual simulation and the actual scenario in the industry, a warmup period plays an important role. In actual scenarios, factories do not start without initially being a work in progress (WIP). A warmup period is needed to achieve a steady state condition in the simulation. A warmup period is the amount of time that a model runs before any results are recorded. The results of the model are unlikely to be typical until the model has warmed up. In this case, the warmup period is set to 2 shifts (12 hours per shift). The results obtained from the simulation underwent a statistical analysis to determine the relationship between the experiment parameters and the performance measurement.
The results of the simulation runs are analyzed in this section. As mentioned, three experiments were conducted to investigate the significance of the changes in the shop floor. Under each experiment, two alternative models and a base model were compared in terms of the throughput rate, machine utilization, and operator utilization. The model that obtains the best performance is chosen from each experiment for further analysis. The results of each experimental run are discussed and tabulated in Tables
Results of Experiment 1.
Throughput rate 
Machine utilization 
Operator utilization  

Base model  0.0234  44.53  44.63 
Model 1  0.0234  44.61  44.63 
Model 2  0.0234  44.52  44.63 
Results of Experiment 2.
Throughput rate 
Machine utilization 
Operator utilization  

Base model  0.0234  44.53  44.63 
Model 3  0.0184  34.77  59.34 
Model 4  0.0186  35.08  66.43 
Results of Experiment 3.
Throughput rate 
Machine utilization 
Operator utilization  

Base model  0.0234  44.53  44.63 
Model 5  0.0298  70.59  70.64 
Model 6  0.0251  69.86  70.03 
This experiment is to test the significance of the different part flow patterns on production performance. Three types of flow pattern are presented: flow 1, flow 2, and flow 3. Table
The results demonstrate that the base model, Model 1, and Model 2 have equal throughput rates and labor utilizations, while the machine utilizations of the three models are almost comparable. The differences in the machine utilizations of Models 1 and 2 compared to that of the base model are 0.08% and 0.01%, respectively. Thus, differences in the flow pattern of parts do not affect the shop floor performance because all the models have equal throughput rates and operator utilizations, and the differences in the percentages of machine utilization are negligible. The three models have the same performance in terms of the throughput rate, machine utilization, and operator utilization. However, the results show that the machine utilization of Model 1 is slightly better than that of the base model and Model 2, which means that flow 2 performed better in terms of machine utilization. Thus, Model 1 was chosen for further ANOVA based on the results.
Experiment 2 is conducted to determine the effect of a reduction in the number of operators on the production performance. The number of operators varies in each model and is determined by the ratio of the number of operators to machines, which is 1 : 1 and 1 : 2. This experiment used 17, 10, and 9 operators to examine the effect of the operator numbers on the production performance. The results of Experiment 2 are tabulated in Table
The results reveal that the performances of Models 3 and 4 are inferior to that of the base model. The throughput rate and the machine utilization of Models 3 and 4 decreased drastically because of the reduction in the number of operators. However, the operator utilization increases because the operators are busy coping with the impending parts. The obtained data show that if the number of operators is reduced to nine, the throughput rate and machine utilization are reduced to 0.019 lot/min and 35.08%, respectively. By contrast, the operator utilization increased to 66.43%. However, Model 4 is selected for ANOVA because the performance of this model is slightly better than that of Model 3 in terms of the throughput rate and machine utilization. As regards the reduction in the number of operators, the ratio of one operator to one machine possesses the highest throughput rate, which indicates that 17 operators in the shop floor are able to produce a higher throughput rate compared with 10 and 9 operators.
The significance of different volume of parts on production performance was studied in Experiment 3. The volume of parts applied is based on the customer demand, which can be divided into low, medium, and high. Different volume of parts might have either a positive or a negative effect on the production performance. Table
The results indicate that Model 5 has the best performance compared with the base model and Model 6. Model 5, with a medium demand, has the highest throughput rate of 0.0298 lot/min, and the machine and operator utilizations have increased by approximately 26.06% and 26.01%, respectively. For Model 6, the throughput rate increased to 0.0251 lot/min, and the machine utilization apparently increased by 69.86% compared with that of the base model at 44.53%. There is not much difference between Models 5 and 6 in terms of the 3 measurement criteria. The machine and operator utilizations of Model 6, with a high demand, have differences of only 0.73% and 0.61%, respectively, compared with Model 5. This observation implies that the performances of both medium and high demands show not much effect. Nevertheless, the difference between the low demand and the medium and high demands is remarkable, which is roughly 26%. Hence, the shop floor performs best with medium demand. Therefore, Model 5 is selected for further ANOVA.
Once the three models are resolved, ANOVA is applied to study the sampledata relationship of the selected models. ANOVA is a statistical method used to test the significant difference among means. ANOVA is also a hypothesis test that consists of a null hypothesis (H_{0}) and an alternative hypothesis (H_{1}). If the calculated
ANOVA is employed to test the following hypotheses:
H_{0}: different shop floors have no significant effect on throughput rate;
H_{1}: different shop floors significantly affect throughput rate.
The critical
ANOVA for throughput rate.
Source of variance  SS  df  MS 


Between groups  0.003784  3  0.000273  6.582222 
Within groups  0.045225  236  0.000192  


Total  0.049009  239 
For machine utilization, ANOVA is used to test the following hypotheses:
H_{0}: different shop floors have no significant effect on machine utilization;
H_{1}: different shop floors have a significant effect on machine utilization.
The results in Table
ANOVA for machine utilization.
Source of variance  SS  df  MS 


Between groups  41929.05  3  13976.35  35.65273 
Within groups  92515.18  236  392.0135  


Total  134444.2  239 
ANOVA is used to test the following hypotheses:
H_{0}: different shop floors have no significant effect on operator utilization;
H_{1}: different shop floors have a significant effect on operator utilization.
From the results shown in Table
ANOVA for operator utilization.
Source of variance  SS  df  MS 


Between groups  34825.3  3  11608.43  24.02253 
Within groups  114042.6  236  483.2312  


Total  148867.9  239 
The base model and the three alternative models are compared with regard to the performance measurement considered to have a better view of the effect of a different shop floor on the performance measurement. The results of the comparison will aid in making an informed decision on the best models to be adopted by the case study company. The comparisons will be based on the three performance criteria, which are the throughput rate, machine utilization, and operator utilization.
Figure
Throughput rate of the four models.
Figure
Machine utilization of the four models.
Figure
Operator utilization of the four models.
Table
Summary of the four models.
Throughput rate 
Machine utilization 
Operator utilization  

Base model  0.0234  44.53  44.63 
Model 1  0.0234  44.61  44.63 
Model 4  0.0186  35.08  66.43 
Model 5  0.0298  70.59  70.64 
Each model has a different performance in terms of throughput rate, machine utilization, and operator utilization under distinct variables on the shop floor. The base model, which is also the proposed model, is performing normally compared with Model 5, which has an overall significant performance. All the models, except for Model 4, are obviously able to produce more output in a period of time with high machine utilizations. Model 4, which is comprised of nine operators and with flow 1 under a low demand condition, had the poorest overall performance. This poor performance can be attributed to the reduction in the number of operators resulting from the decrease in the machine utilization, thus lowering the throughput rate. Regarding the throughput rate and machine utilization, the higher the percentage of machine utilization is, the higher the throughput rate will be. Model 5, which has the highest machine utilization, evidently has the highest throughput rate among the models as well. Model 5 is the model that operated in flow 1 with 17 operators (one operator to one machine) under medium customer demand. Therefore, the throughput rate is directly proportional to the machine utilization as an increase of 26% in the machine utilization raised approximately 27% in the throughput rate of Model 5 compared to that of the base model. However, high operator utilization does not necessarily mean a high throughput rate, as proven by Model 4. Model 4 is the model that has nine operators (one operator to two machines) and works in flow 1 under low customer demand. The results showed that even Model 4 has high operator utilization, but the throughput rate is the lowest among all models. This finding might be attributed to the fact that one operator is busy handling two machines simultaneously. Hence, a high operator utilization may not lead to a high throughput rate as well. In terms of the three measurement criteria, Model 5 performed well compared with the other models. In the midst of the intensive analysis, the simulation outcome allows the case study company to make an informed decision on the best alternative available when the company is required to make a crucial decision. The DES enables the applicability and performance of various variables to be examined and tested before these variables are changed and implemented in the production. As discussed earlier, the changes in the shop floor can cause a positive or negative effect on the shop floor performance. Examining the changes in the shop floor is important to prevent adverse effects. Choosing the suitable solution makes a difference in the shop floor performance because a bad decision on this matter can be disastrous, and a suitable solution can lead to an optimal production operation. From the managerial perspective, finding the optimal operating shop floor is important for the case study company. Throughout this study, the primary benefit to the company is that changes in production operation can be made at the lowest cost and without interruption through simulation. In this way, the management team is able to choose the appropriate and optimal operating shop floor through proper analysis and planning.
This study investigated the application of DES in identifying the effect of different number of operators, volume of parts, and different types of flow pattern of parts on the shop floor performance through the case study company. DES is able to measure the performance, and the simulation results can be used to examine the shop floor performance via statistical analysis. The results obtained from ANOVA proved that the shop floor performance is significantly affected by the three measurement criteria: throughput rate, machine utilization, and operator utilization. The best model is demonstrated under each alteration in the shop floor. Aside from the optimal operating shop floor determined from this study, the manager is also able to choose the appropriate models to be implemented in the shop floor based on different performance measurements. The performance measures that are selected can be used to assess the efficiency of the organization, and the data can be a benchmark for future planning to find ways of improving productivity. In actual scenarios, changes in operating conditions can vary the results obtained. For example, an alteration in the level of buffer capacities, part interarrival time, variety of products, and machine failure rate can cause different outcomes and have different effects. System disruptions, such as material handling system breakdowns and absence of operators, can be included in future studies so that the details considered will be closer to the realworld scenario of the shop floor.
The authors declare that there is no conflict of interests regarding the publication of this paper.
The authors wish to acknowledge the support of the CREST grant scheme from the Government of Malaysia for funding this research.