Recent Researches in Manufacturing Engineering

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1 QUALITY CONTROL ANALYSIS IN THE PACKING AREA OF A FOOD COMPANY PLANT YESICA ROJAS RODRÍGUEZ, ANNA GABRIELA PÉREZ, FRANCKLIN RIVAS-ECHEVERRÍA* Universidad de Los Andes Facultad de Ciencias Económicas y Sociales Escuela de Estadística Mérida VENEZUELA ycikrr@hotmail.com, gabipm@ula.ve *Universidad de Los Andes Facultad de Ingeniería Laboratorio de Sistemas Inteligentes (LabSIULA) Mérida Venezuela rivas@ula.ve Abstract: This paper presents an application of statistical quality control in the packing area of a food company plant. This study focused on the nonconforming fraction estimation and the construction of control charts using 3σ philosophy, and also it is analyzed the defect in the final product packaging. It was controlled other sources of variation as machines, working turns and operators groups and subsequently it was verified the interaction of these sources of variation on the amount of waste by a factorial analysis. It was found that the significant interaction is produced between the machine and working turns variables. Keywords: quality, statistical quality control, non-conforming fraction, factorial model 1. Introduction The quality concept has acquired in recent years, as an economic and business strategy, and as a determining factor in consumer choice a prominent role. The quality definition depends upon the environment or scope, being defined as compliance or conformity with the specifications in the field of production, trade and sale. However, another definition refers to the set of properties and characteristics of a product or service that gives an ability to meet explicitly or implicitly expressed needs [8]. In the food sector, the term quality is defined as the set of physical, chemical and biological proprieties, and no presence of contaminants, and to give the product the ability to meet the consumer s needs. In the context of the food industry there are several types of quality, among them: health and hygiene quality, food science (nutrition and composition), the sensory or organoleptic, technological, ethical (or emotional), quality of use and related health issues. World Health Organization (WHO) has argued that the safety of food products is a shared responsibility. The food industry should not bear full responsibility for the quality and hygiene of foodstuffs. Each of the participants in the complex food chain performs its function: responsible for the production, processing, transportation and distribution, but also consumers. To ensure that food reaches the consumer in good condition and fresh, it is necessary to go through many stages. The main reason for the food processing is the elimination of microorganisms, to prevent them from multiplying and spoiling food, thus eliminating any risk of poisoning. Likewise, the industrial preparation prevents putrefaction of food deactivating enzymes and preventing oxidation. The quality meets technical guidelines covering the management at all stages of the food chain (from obtaining the raw materials to final product). On the legal aspects, health and safety norms are mandatory public provision, subject to supervision and punishment for violations. Moreover, the norms and quality systems are voluntary adoption, and establish guidelines for the identification and differentiation of a product or service in the consumer food market

2 2. Control and Quality Management in Food Industry Early attempts for establishing quality systems in industry, have been characterized by the establishment of mechanisms for checking or controlling, through certain technical and operational activities, aimed to verify the quality requirements of the product or service. Among these quality control techniques it can be found the statistical process control [2], especially the use of control charts that based on statistical techniques are useful tools in online monitoring for determining important changes or significant events in the production process, help to detect and/or prevent just in time problems and inconvenience that in the inspection process would be too late. For the construction of these charts, there are used random sampling procedures and it can be evaluated the performance of the process and its variation. The concepts of Quality Assurance, Quality Management and Total Quality have gradually been replacing quality control, focusing more on product safety for the consumer, not only quality control, quality is obtained or is incorporated to the product at each stage of development, requiring management and certification. The food industry has implemented comprehensive security and quality management schemes as the Hazard Analysis and Critical Control Points (HACCP), Good Manufacturing Practices (GMP) or have adapted the model originally developed for other industrial sectors (ISO norms), there is already a specific standard (ISO 22000:2005) for managing food safety in the industry; there are also private food safety standards. All these systems seek to give confidence to the consumer and enabled the food company to assume responsibility for controlling health risks [4.5]. In the food industry the application of a quality program is given in three levels: - Product Quality Control: Requires the control of raw materials, production processes and finished products. Chemical, physical and biological tests are conducted in laboratory. Has the disadvantage that the defects are discovered after the material has been received, or at the end of the production process. - Product Quality Assurance: prevention planning system, its function is to reduce errors to acceptable levels and to ensure a high probability for the obtained data representation. - Quality Management: This means that quality has to be applied to all activities of the company, not just the final product, and that all staff has to be involved. Another key aspect related to the complexity of the food chain has to do with the need to implement integrated management tools for systems traceability which show the steps followed by raw materials from production or harvesting and the final destination of the products. Traceability is also used for identifying and removing non-compliant products, as well as group procedures for the history, location and path of a product along the supply chain. The food products quality also depends on the raw materials, transport, storage, packaging and point of sale facilities. Therefore, manufacturers should work closely with suppliers, manufacturers, wholesalers, transporters and distributors to fully comply with the standards of quality. Packaging is also important for making that the product reaches the consumer in perfect condition; packaging provides information to help consumers for preparing and preserving food and for knowing their nutritional value, ingredients and expiration dates. 3. Case Study The plant is located at the west of the Bolivarian Republic of Venezuela. The plant has seven production lines where can be obtained 14 different products, and is staffed 24 hours a day, seven days a week for 507 people, divided into 4 production groups which rotate as follows: 3 of them are working while one of these groups is resting. Production hours are: 7:00 AM to 3:00 PM, 3:00 PM to 11:00 PM and 11:00 PM to 7:00 AM. The plant's current capacity is 900 tons of products per month. Quality checks carried

3 out on the plant are classified into five groups: 1. Quality programs, focused on the consumer. 2. Food safety programs. 3. Flavor, texture and appearance Programs. 4. Continuous improvement programs. 5. Packaging quality programs. In the area there are three sub-programs Sanitation Comprehensive Security Solid waste The line on which this research is conducted is line 3, specifically in the packing area in order to estimate the nonconforming fraction, considering that all packaging machines are working on the same terms and under the same process and product specifications. In the calculation of the nonconforming fraction there are considered all possible defects that have finished product bags, i.e. all the quality product characteristics that are out of specification at the end in order to determine the impact on productivity and product profitability. It is important to mention that the plant claims the zero waste approach, however, has not applied any methodology to avoid or reduce waste. The plant has introduced high levels of packaging waste bags or film on different turns and working groups, so there is a need to identify the causes that are leading waste. To do this, it is observed and collected data from August to October This area has 5 machines, and the first point of interest is to know the situation of waste in the line, checking the following sources of variation: - Packing machines (1, 2, 3, 4 and 5). The machine 1 only packs family size product, while the other 4 pack regular size product. - Working turns (I, II, III). - Groups of operators (A, B, C, D) Descriptive statistics were calculated for the number of defective bags or packages per turn. Table 1 shows that working turn 2 is the one with a higher mean number of defective packages and also presents a greater dispersion around this value than the other two turns. Table 1. Descriptive Statistics: Packaging defective per turn Turn Mean n Standard Deviation Table 2 gives the number of defective packages per machine, specifying the type of defect. Product packages have the following defects: gag, loss of registration and air leakage, which are serious in the sense that a defective product package does not guarantee the food freshness, or the preservation of it until the expiration date. On the other hand, defective packages can not be reused or recycled resulting in losses for the company. Table 2. Total defective packages per machine and type of defect Machine Defect Total gag loss of registration air leakage Total For each machine there were made three sigma (3σ) control charts for the nonconforming fraction and all of them show points are out of control, indicating that the nonconforming fraction of the process is out of control and exceeds the allowable limit. It should be looked for reasons attributable to this fact. Figures 1, 2 and 3 depicts the situation described above. Figure 1. Control chart for nonconforming fraction - Machine

4 [11], whose results show that the model is significant, however the only significant interaction is the double interaction machine*turn (with a level α = 0.05), which can be interpreted as: turn or work schedule in conjunction with the machine produce a joint effect on the waste. The group of operators is not significant in this study. Figure 2. Control chart for nonconforming fraction - Machine 2 Table 4. Factorial ANOVA Source DF SS MS F p Model Error Total Table 5. Factorial - interactions ANOVA model Source DF SS MS F p turn Mach*turn Figure 3. Control chart for nonconforming fraction - Machine 4 The analysis of product defective packaging is also done taking into account the turns and the group of operators. As presented in Tables 3 and 4, the turn II and group B gives operators more defective in product packaging. Table 3. Percentage of defective packages per turn Turn % Defects I II III Table 4. Percentage of defective packaging per group of operators Group of Operators % Defects A B C D Subsequently, through a general factor model it was investigated the combined effect of machines, operators, and turns on the amount of defective packages. It was used the statistical system SAS systems 4. Conclusions The statistical quality control analysis yields the following conclusions and recommendations for reducing packaging waste on the plant: - Statistical quality control is an essential tool for monitoring the production process of packaging; in this research were used control charts for the nonconforming fraction and the study was conducted by type of defect. - It is contradictory that a producing foods plant that have within their operating schedule an important structure of quality plans, present such high levels of waste in packages. Certainly, it is important to reach the production volume and achieve the annually goals, but would be more efficient reducing the amount of waste because it yields savings in packaging, considering that they are not reusable or recyclable. - Machine 1 is of special interest, because it only package family size products, produced in smaller quantities than the regular size product packaged on other machines, the nonconforming fraction for machine 1 is very high, adding that the cost of family size packaging is considerably more expensive, so the waste of this

5 machine produces a considerable impact on the company. - All machines have the same defects, but machine 5 present the largest amount of waste generated; turn II and group of operators B are those with largest number of defective packages. The defect with the highest percentage is given by gag problems due to sudden temperature changes experienced by machines. The temperature changes in plates are very abrupt, generating seal failure and leakage of air in the packages or product containers. - The factor analysis shows that there is a joint effect between working turn and failures that have the machines on the amount of generated waste. Therefore, supervision should be strengthened at different times, as well as proper training of operators to reduce errors in handling the machines and in order to detect any possible fault. - In one month, the amount of defective bags is kg, which represents BsF ,00 (near US$ 24,000) of average waste; an amount that significantly affects the production cost. - Training of the operators is very important, because this could affect the efficiency and time, elimination of waste material, and the quality of the final product itself. References [1] Littell, R. Stroup, W. Freund, R. (2002). SAS for Linear Models. Forth Edition. SAS Publishing. [2] Montgomery, D. (2004). Control Estadístico de Calidad. Tercera Edición. Editorial Limusa Willey. México. [3] Montgomery, D. (2002). Diseño y Análisis de Experimentos. Segunda Edición. Editorial Limusa Willey. México. [4] Oyarzún, M. (2001). Sellos de Calidad en Alimentos. El caso de la Unión Europea y Francia. Organización de las Naciones Unidas para la Agricultura y la Alimentación. Chile. [5] Oyarzún, M. Tartanac, F. (2002) Estudio sobre los Principales Tipos de Sellos de Calidad en Alimentos a Nivel Mundial. Estado Actual y Perspectivas de los Sellos de Calidad de los Productos Alimenticios de la Agroindustria en América Latina. Santiago de Chile. [6] Paz, E. (2009). La Metrología. Su impacto en el comercio, la industria y la salud. Centro Hondureño de Ciencia y Tecnología. Honduras. [7] Pérez, C. (2009) Técnicas de Análisis de Datos con SPSS 15. Primera Edición. Prentice Hall. Madrid España. [8] Prieto, M. Mouwen, M. López, S. Cerdeño, A. (2008). Concepto de Calidad en la Industria Agroalimentaria. Interciencia 33:4: Caracas, Venezuela. [9] Rangel, G. (2009) Certificación de Calidad NORMEX. México. [10] Rojas, E. (2009). Control de calidad en productos alimenticios y laboratorios de ensayo según norma ISO Laboratorio de Salus Pública. Instituto de Salud Pública. Madrid - España. [11] SAS/STAT 9.2 User s Guide. (2008) SAS Insitute INC. Cary, NC, USA