Espacios. Vol. 35 (Nº 6) Año 2014. Pág. 11
Engineering Methods for the Elaboration of the Process Sheet in Chair Manufacturing
Métodos de engenharia para a Elaboração da Folha de Processo na cadeira Manufacturing
Recibido: 27/03/14 • Aprobado: 16/05/14
With the fierce competition from the market, companies come searching for alternatives in order to remain consolidated in the market, in front of their competitors. With this, the analysis of some important factors that support the elaboration and form of how to execute the processes is indispensible, and between them, the study of time and movement stands out.
According to Taylor (1970), when there is execution of manual work and it is necessary to find the most economic way of achieving operation, it is necessary to determine the quantity of work that should be done in a given period of time.
The study of time and movement can be applied in all processes of products, from the beginning of the manufacturing, to the transportation of the finished product. The objective is to find the best way of manufacturing a product, through permanent observations approaching the best method, searching for changes that permit the reduction of time of production and the best quality of the manufactured items, avoiding the surge of bottlenecking, variability in the execution of processes and low productivity.
The Process Sheet can be considered a support tool in the search for standardization of activities in manufacturing. Standardization is of fundamental importance for an oragnization that aims to control production processes, increase the quality of its products and services and achieve and satisfy the desires of its clients. Standardization is also important for allowing the critical analysis and the best consequence of the procedures and methods of a company because it provides a concrete perspective of what analyzing and improving is.
The work encompasses the assembly line of chairs from the furniture industry. The objective of such study was to suggest improvements in the process of analyzing finished works in the chair assembly sector, aiming at an increase in productivity, efficiency and the standardization of time. For this, a process sheet was elaborated that will help in the standardization of assembly jobs, estimation of methods of production and actions that support quality control. The techniques of the study of time and movement that allow the systematic investigation of factors that affect efficiency were utilized.
The article is structured in three sections beyond this introduction. In section two, a theoretical reference is presented that addresses the studies of time and movement, standardization and the process sheet. In section three, the case study is presented. In the fourth section, the final considerations about the work are exposed and finally, the utilized references and the process sheet in the annex are presented.
2.1. Study of time and methods
According to Furlani (2011), the study of time and methods can be defined as a study of a system that possesses identifiable ponts of entrance- transformation- exit, establishing standards that facilitate decision-making. So, the increment of productivity can be favored and it can be provided with the information of time, with the objective of analyzing and deciding, which is the best method to use in the production jobs.
According to Barnes (1997), for development of the preferred method, some steps are followed:
a) Definition and formulation of the problem: process of being studied;
b) Analysis of the problem: description of the current method with its respective specifications and restrictions;
c) Evaluation of the current method: upon finding possible solutions, an evaluation for determining a sequence of operations and procedures that achieve the ideal solution should be created;
d) Standardization of the best found method: Factors and conditions of work should be conserved, such as, the group of movements of the operator, dimensions, form and quality of the material, tools and devices, after being standardized. In order to preserve the standards, a registry of standardized methods of operations should be made, providing a detailed description of the operation that was analyzed. The determination of standard time can be used in the planning and programming of the estimation of costs of the labor, it can serve as a base for the plan of salary incentives and also for the area of planning and control of production.
e) Training of operators: For the efficiency of the method of work, it is necessary that the operator executes the operation from the pre-established way. The training is given by able people, and some tools like process sheets, graphs, models and films can help them during this process.
Feliciano and Rotondaro (2008) affirmed that management through processes results in a better development of abilities of workers, better satisfaction in their work and an increase in the autonomy of every operator.
According to Barnes (1977), the necessary equipment to the execution of the study of time consist of: a stopwatch; a video camera; a clipboard, and a sheet of observations or timing (used for the registry of times, description of operation, name of operator, specifications of materials and tools, date and place of the study.
For Culchesk et al (2012), the collection of times is essential for the analysis of the problem because the collected times are used in order to make the calculations of productivity, efficiency, so as to establish programmations and planning of work, making it possible to determine the standard costs and budgets.
A business needs to interpret the desires and necessities of its clients in order to survive in a firece market. In a process, in which the demands of the clients are in constant change, a business needs to adapt itself in order to transform such demands in goods and services that satisfy its clients. In agreement with Campos (1999), the quality of a product or service is associated with the satisfaction of the client, in other words, it is a product that attends to the needs of the clients in a reliable and safe way, of easy access and at a certain time.
The demand for products that attend to the needs of the consumers drives companies to search for more competitive results through changes in its production systems. This competition passes through the guarantee that everything is being executed is in agreement with the established standard (KISHIDA et al., 2005). However, so that it is executed as a standard, it is necessary in the first moment to establish and train the people involved for finally verifying results of conformity. According to Cerco et al (2006), this process is called standardization.
Standardization is a process that should be practiced continuously, not only used to demonstrate organzation and conformity in time of auditing in companies (LIKER; MEIER, 2007). Standardizing is "planning the standard, executing in accordance with the standard, verifying the effectiveness and efficiency of the standard, training and improving the previous steps whenever possible" (ARANTES, 1998, p. 17).
In agreement with Cerco et al (2006), it is essential that the best mode of execution of the determined work is permanently registered, so that this document can be consulted by the operator or as support to the manager and to instructor during the training of the operator. These registries contain complete details of the operation, the elements that compose the work, the tools and devices used, among other information. One time that the method has been standardized and put in execution, constant vigilance by the administration becomes necessary so that the standard is maintained (SUZAKI, 1987; SENA, 2011).
2.3. Process sheet
The process sheet can be considered a support tool in the search for the standardization of activities, which comes to supply the need of creating a formal registry of the procedures of production of a simple and easy to consult form by the users, being able to be used as a useful tool in the support through a search in the system of management of total quality. It presents the quantity of work posts that are necessary for the production of a determined product (ALMEIDA, 2009).
According to Almeida (2009), through elaboration of the process sheet, it is possible to attain the advantages of standardizing the processes from the point of view of all interested parties: the company, the manager, the employee and the client. For the company, the main benefits of standardization are: returning predictable products and services, assuring the technological domain of the organization and guaranteeing that new employees continue to produce the same good or service in the same way. Regarding the manager, standardization facilitates the training of new employees, it eliminates the effort of searching for a solution for the same problem repeatedley and it facilitates the planning and control of the daily work (GOLLAN, 2006; HAMMER, 2002).
For the employee, its advantages are: the capacity of executing jobs without the necessity of frequent orders from management, better safety in the work environment, better motivation through the participation and involvement in the elaboration of the standard and the possibility of producing the best work with less effort.
From the point of view of the client, the main benefit is the guarantee of the delivery of products or services with the same characteristics of quality.
The study was initiated with a bibliographic research in search of publications that address concepts about the study of time and methods of work, standardization and the process sheet. After comprehension of the methods through the theoretical base, a case study in the assembly line of chairs in the furniture industry was created. The procedures for the collection and analysis of those given were divided into five steps:
a) Interviews with the manager and those in charge of the assembly line and observations of the process of the assebly line of chairs;
b) Identification of all of the works that compose the process of assembly
c) Establishment of the number of cycles to be timed, collection of the times of each work, determination of the velocity (V), normal time (NT), tolerance factor (TF) and calculation of the standard time of each work (ST);
d) Analysis and diagnosis of the quantitative and qualitative data, in other words, of the standard times movements realized by the workers;
e) Elaboration of the process sheet for the assembly of chairs and suggestion of standardization of the assembly method as a proposition of improvements for the business.
3.1 Description of the assembly process of chairs
The assembly process of chairs is realized only by two employees and the completion by eight workers. Both employees that assemble the chairs execute all the jobs of the process, they work without the use of systemized methods, in other words, without a specific order of doing their jobs, alternating according to demand. As the chairs are assembled with rigid standardization of the jobs, the business assumes an elevated possible variablity in the process, and consequently, it differentiates in the times of delivery of that product. In Figure 1, it is possible to see the fluxogram of the assembly sector and the completion of the chairs.
Figura 1 – Fluxogram of the assembly process of chairs
Fitting the rear structure: The worker searches for the pack of orders and places it close to the bench, after, he arranges the orders in the bench according to the following order, from left to right: feet, rear pivot, backrest, and top. After arranging the orders, the worker arranges two feet (right and left) on the bench in the position in which he will receive the other orders with the holes facing upwards. Next, the worker fills the holes of the feet with glue in the cross bar and in the holes of the top. After, the worker fits in the feet: the backrests, the pivot and the top following this order. If necessary, a rubber mallet is used in this operation in order to facilitate the fitting. Finally, the worker places the rear structure to the right of the bench.
Pressing the rear structure: The worker picks the allocated structure to the right of the bench, he presses on the neumatic press, he removes the excess glue and he verifies the framework. Finally, the structures already placed and pressed are arranged in the vicinity of the benches.
Fitting the forward structure: The worker searches for the pack of orders and places it close to the bench, moving forward, he gets two feet (left and right) and the forward lane, he puts glue in the holes and in the pivots and he fits it with help from a rubber mallet if necessary. After, he places the forward structure to the right of the bench.
Pressing the forward structure: the worker takes the rear structure and places it to the right of the bench. He presses it in the pneumatic press and remove the excess glue. Finally, the structures that have already been placed and pressed are arranged around the stands.
Fitting the final structure: the worker organizes a packet of each structure in each side of the bench and places the packets of pins to the right and to the left of the bench as the position of assembly. Next, the worker presses a rear and forward structure e places one over another on the bench with the holes facing upwards. The worker puts glue in the holes and fits the pins, closing the two strucutres, forming a chair. Finally, the workers puts it to the right of the bench.
Pressing the final structure: the worker acquires the structure, presses it in the neumatic press, removes the excess glue, and checks and adjusts the structure in the matrix with the help of a mallet. After, the structures that have already been placed and pressed are places around the benches.
Leveling: Every two structures that have been pressed, the operator verifies if they are level, putting the chair on top of a glass table and checking the unlevelness of the feet of the chair, in case they are not level, the foot should be sanded in the sanding machine that sits to the side of the leveling table. Finally, the two leveled chairs are directed to the stock, where they will wait for the next process.
Patching: the worker searches for two chairs and brings them next to the bench. After, the worker takes a chair and verifies if any inconformities exist, such as: cracking, holes, or cracks between parts, and filling them with glue if necessary. Finally, the worker places it in the stock next the the bench for the next step.
Sanding: the worker searches for a chair and puts it on top of the bench. After he sands the chair, checking if it still has imperfections, in the case that there are, he repairs it with glue. Finally, the worker marks the chair and passes it to the next step.
Inspection: the worker searches for a chair that is near and places it on the bench. After, he checks if there are incomformities, and in the case that there are, he fixes them or he returns it to be sanded. Next, the worker places it on the transport car and finally, he brings the car to the painting station, when it has with its maximum limit.
3.2 Determination of inclusive jobs in the process and analysis of time
Initially, all the jobs were listed. The process was observed and eight jobs were found, like those included in the process. From ownerships of this list, times of every job were made.
Lidório (2011) explains that operations should be times in quanitity that oscilates between 10 and 40 observations according to the following criteria:
-10 to 20 observations for the small series production;
-20 to 30 observations for series production
-30 to 40 observations for mass production
Considering the methodology of Lidório (2011) and the production of the chairs being in small series, 20 cycles are determined to be timed.
From possession of these times, the rhythm factor (RF) was established, which according to Barnes (1977), is the the evaluation of rhythm of a worker in which the analyst of the studies of time compares the rhythm of the worker in observations with its own concept of normal rhythm.
RF= 100% normal rhythm
RF> 100% accelerated rhythm
RF< 100% slow rhythm
For the study, the RF= 100% is considered, in other words, RF= 1, as a normal rhythm of operation. After, the rhythm factor will be applied for an achievement of a standard time.
The workers that work the entire day need breaks in order to attend to their personal needs, and because of this, it is necessary to determine tolerances. The tolerances for these interruptions of production can be personal, for fatigue or waiting. In agreement with Barnes (1977), in the operations that involve heavy physical force in adverse conditions of heat, humidity, dust and danger of accidents, reserving 4% of the operator's time should be reserved, so that health problems do not occur. Fatigue results from a large number of causes, both mental and physical. The tolerance for waiting can be evitable or inevitable. The waiting done intentionally by the worker will not be considered in the determination of standard time. In reality, inevitable waiting occurs, caused my machine, by the operator or my some external force.
In agreement with the observations, it was found that workers work approximately nine hours per day, on foot and with easy jobs, however, considered repetitive and tiring. Through these motives, it was decided to establish a tolerance of 10%, that was added to the normal time during the calculation of standard time of the chair.
After these studies, the standard time for each job was determined. The calculation began with the determination of the average time of every operation (Table 1), which was obtained through the addition of times of every element divided by the number of times cycles.
Table 1- Jobs and respective average times in seconds (s)
Source: Authors (2012)
Regarding the normal time of an operation, this does not account for some tolerance, it is simply the necessary time so that a worker executes a job in a normal rhythm. Equation 1 illustrates the calculation of normal time (BARNES, 1977):
NT = AT x RF Where:
NT= Normal Time
AT= Average Time
RF= Rhythm Factor
After the calculation of normal time, it is possible to obtain the standard time (Equation 2), which should contain the duration of all elements of the operation and, furthermore, it should include the time for all necessary tolerances (BARNES, 1977).
ST= NT + (NT x Tolerance in %) Where:
ST= Standard Time
NT= Normal Time
Table 2- NT and ST of the included jobs in the assembly process of chairs
Source: Authors (2012)
With foundation in Table 2, it is observed that the total standard time of the assembly sector that includes the assembly processes and completion of the chairs is 1935.53 seconds.
The elaboration of a production goal is fundamental in order to determine the standard time of production. Being that the standard time for the assembly of a chair is 1935.53 seconds, in a normal rhythm, 1.86 chairs should be produced per hour, approximately. In agreement with the reality of the business, it is stipulated that the workers would have a tolerance of 35% for loss of time spent in the total activities, in other words, the worker will work with a productivity of 65%.
Productivity = (units produced x 100) / units that should be produced (Equation 3)
Goal = Productivity in (%) x units that should be produced (Equation 4)
Units that should be produced = 3,600/1935.53
Units that should be produced = 1.86 chairs/hour
Goal = 65% x 1.86
Goal = 1.20 chairs/hour
Therefore, 1.2 chairs should be produced per hour, approximately, in order to achieve the goal. In accord with Toledo Junior (1977), productivity is the relation between that which is produced and that which should be produced, and it is expressed as a percentage.
3.3 Process Sheet
With ownership of all jobs included in the process, as well as interviews with the workers for definition of tools, components, equipment and the main cautions for quality control. Finally, the process sheet can be visualized at the end of this article.
In small and medium businesses, it is common to verify non-standard processes, in which the way of executing them is only clear to the worker that does them and in the memory of the people. In addition, if a group of people executes the same, normally, everyone does it in a different way. Thus, it is fundamental to create a system of standardization that resolves this problem.
The process sheet is considered very important in the seach for standardization of the production system. From this way, businesses should require to see the standardization as a tool that will bring cost benefits, deadlines, satisfaction from the client and principally quality in the services and products offered.
Through the study of time and methods of the assembly process of chairs, it was possible to elaborate a process sheet, to which a business comes to attend this need of making a formal registry of the procedures of production of a simple and easy way for the users to consult. The process sheet can be used as a useful tool in the search for the management of quality control.
Quality control in every job, as the process sheet increases efficiency in standardization of the process, with this, re-processes and unnecessary costs are avoided. All those interested in the production will be benefits with the utilization of the process sheet by the workers.
For the business, standardization becomes advantageous, because it allows products and services to become predictable, it guarantees that new employees will continue to produce the same good or service in the same way and it facilitates the planning and control of daily work.
For the employee, the advantages are: the capacity to execute jobs without the need of frequent orders from the supervisor, better security in the workplace, better motivation through participation and involvement in the elaboration of the standard and the possibility of making the best product with the least effort. And the best aggregate benefit for the client is the guarantee of the delivery of products or services with the same characteristics and quality. However, even with so many advantages, people that react to the efforts of standardization still exist.
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1 Production Engineering Post Graduation Program, Federal University of Technology - Paraná (UTFPR) E-mail: firstname.lastname@example.org