INTRODUCTION

In December 2019, domestic and global businesses were hit by the COVID-19 pandemic, which caused reductions in both perceived sales and resources for large organizations. Losses were heavy and caused the closure of many of these companies, with Small and Medium Enterprises (SMEs) accounting for the largest percentage of those declared bankrupt.

In March 2020, the President of Peru announced the beginning of a state of sanitary emergency, which was the nationwide standstill of all non-essential economic activities and the closing of borders. In this context, the metalworking sector closed all types of activities for a period of 60 days.

The metalworking sector was included in the first reactivation phase, with the International Standard Industrial Classification (ISIC) code 2511. During the initial phase, problems arose in terms of material costs, low operating resources and delays in order delivery, which generated an increase in product prices and a growing concern for improving the efficiency and productivity of operations.

This study aims to improve productivity in a metalworking company by applying three Lean Manufacturing tools: 5S, Andon and Standard Time. The study focuses on the production area and begins with an initial diagnosis through the Value Stream Mapping, followed by the implementation of the Lean Manufacturing tools and, finally, the evaluation of the results obtained.

The study seeks to demonstrate the hypothesis “the implementation of Lean Manufacturing tools (5S, Andon and Standard Time) improves productivity in a metalworking company” through statistical analyses that serve to contrast the hypothesis of the study.

Likewise, this article seeks to serve as an example of the impact produced by the implementation of Lean Manufacturing tools in the metalworking sector, taking as a reference the company under study and resulting in the increase of productivity.

This research work highlights the main problems faced by companies in this sector: the lack of order and cleanliness in the work area, the slow response to failures or abnormal events in the processes, and the lack of clarity in the times used for production scheduling. Emphasis is also placed on how the application of a Lean approach can help mitigate these problems.

Regarding the limitations of the research, this work is focused on companies in the metalworking sector, on the application of some Lean tools that mitigate specific problems in the company (5S, Andon and Standard Time) and on how these have an impact on the company’s productivity.

METHODOLOGY

In this study, a quantitative approach was taken. According to ^{Hernández et al. (2014}), a quantitative approach to research refers to a set of sequential and veridical processes, where researchers are concise, given that they conduct organized studies based on numerical and statistical measurements.

The hypotheses formulated are tested to achieve the objective sought through an explanatory level of research. The design followed by the work was pre-experimental. According to ^{Hernández et al. (2014}), the pre-experimental design is a study in which one or more independent variables are handled to analyze the consequences they cause on the dependent variables.

The unit of analysis was the production area of the metalworking company under study, where the relevant information for the research was obtained. The processes, causes and defects existing in the main processes of the area were analyzed.

The study population consisted of the different causes identified in the area in a period of 30 days. For the analysis and the taking of indicators over a period of seven months, 100% of the production of the chosen product family was considered. The steps followed in the research are sequenced as follows:

RESULTS

Productivity

The following formula was used to determine the company’s productivity:

For the initial evaluation of productivity, records were taken from April to September 2021 (Table 1), which resulted in an average productivity of 0.26 tons/soles, which is a result below the company’s expectations.

Value Stream Mapping

The VSM is used to construct the initial state of the processes and the lead time of the production system considering the product family identified in Table 2 and the cutting, welding, shot blasting, painting, and packing processes.

Figure 1 shows that the painting process is critical since the cycle time required is 1.53 hours per ton and this activity exceeds it by taking up to 1.70 hours. The second critical process is shot blasting, followed by cutting.

The results of lead time and time that adds value are 19 days and 0.7 days respectively, resulting in only 3.6% of the total time corresponding to activities that do add value.

Cause Analysis

A cause-effect diagram was constructed to analyze the identified causes (Figure 2). It sought to relate the causes to each factor that caused the problem. A Pareto chart was then constructed (Figure 3). A 30-day period was taken to determine the frequency of occurrence of each identified cause in order to determine the most relevant causes for mitigation or improvement.

5S Diagnostic

The cutting process is taken to evaluate the initial results of 5S compliance in the work area (Figure 4) and the images of situation in the workplace (Figure 5).

Implementation of the 5S

The insertion of the tool follows the steps described by ^{Madariaga (2013}): separate, sort, clean, standardize and discipline. This was done in the following manner:

Implementation of Andon

Andon is implemented in the shot blasting process to eliminate the high defect rates generated in the area. The stages that were followed are according to ^{Córdova (2012}).

Standard Time

The painting process is used to measure the work time. It should be noted that a timing measurement is used using a technique that sets the time back to zero and that the product taken as a reference for the measurement is the standard field tent.

To determine the elements that are part of the process, the process analysis diagram is applied. Fifteen measurements are taken for each element and the average time is calculated, and with the help of the Westinghouse method, the normal time is calculated. After that, the allowances within the process are identified for the calculation of the standard time of each element and of the process (Table 4).

5S Results

Three evaluations were carried out using the audit format. The periods evaluated were April, June and September 2022 (Table 5). The results of the final audit (Figure 7) and the effect of the 5S in the workspace (Figure 8) are shown.

Andon Application Results

The results obtained correspond to the periods of April, June, and September 2022, which show how the visual indicators had an impact on stopping abnormal situations in the work execution (Table 6).

Productivity Result

Measurements are taken for a period of 6 months after the implementation of the tools and divided into weeks, resulting in a take of 25 weeks (Figure 9).

Value Stream Mapping Results

The future VSM, after the implementation of 5S, Andon and standard time in the cutting, shot blasting and painting processes respectively, is observed (Figure 10).

Hypothesis Test

Productivity data for the period 2021 and 2022 are recorded and analyzed for normality with a significance level of α = 0.05 when applying the Anderson-Darling test (Figure 11 and 12). The data are accepted as having a p-value > 0.05 at 95% confidence.

H₀: The implementation of Lean Manufacturing tools (5S, Andon and Standard Time) does not improve productivity in a metalworking company.

H₁: The implementation of Lean Manufacturing tools (5S, Andon and Standard Time) does improve productivity in a metalworking company.

The results obtained after performing the Student’s t-test is that the p-values are less than the significance level (p-value < α) (Table 7), which results in the rejection of the null hypothesis and the acceptance of the alternative (Table 8), which means that the implementation of Lean Manufacturing tools does improve the productivity of the company under study.

In the box plot performed (Figure 13), an increase in productivity can be observed in 2022 with respect to 2021, which shows an improvement due to the impact of the implementation of Lean tools.

DISCUSSION

By applying 5S, an improvement is achieved in terms of organization, order and cleanliness in the cutting area, with a 20% improvement after implementation. Likewise, as with the application of Andon, a reduction of up to 19% in the stoppage time for abnormal events was achieved. By determining the standard time of the painting process, it is possible to determine the standard time of the elements and process, giving a total of 1.50 hours per process.

The results show improvement and have an impact on a 27% increase in productivity compared to 2021. These results are similar to those obtained by ^{Vargas (2022}), who states that the implementation of Lean tools, such as 5S, impacted productivity, as it increased by 30%. Likewise, ^{Bermejo (2019}) mentions that the application of these tools improved productive times and increased the units produced, which also impacted on the 25% increase in their productivity.

According to the results obtained in the research, the use of Lean Manufacturing tools (5 S, Andon, standard time) manages to impact the productivity of any organization that presents problems of efficiency and effectiveness in its operations, which serves as a starting point to analyze the other tools that are part of the Lean Manufacturing system and how they impact productivity.

CONCLUSIONS