Product deployment focuses attention on the easier production cycle. When the demand for the product is large enough and lasts for a relatively long time, it is usually appropriate to arrange the resources closer to each other in the sequence imposed by the product itself.
Kaizen, Kanban, Scrum, and other popular Agile methodologies
The following article presents classic information that is a base of all modern Kaizen, Kanban, Scrum, and other popular Agile methodologies and approaches to product development. Still, we present the knowledge not in the context of software development but in manufacture.
This is often referred to as an assembly line, although the ratio of direct manual labor to machining can vary greatly. Assembly lines can range from 100 percent assembled parts of workers to the other extreme, a transfer line where all the work is done by machines. Among them are all other variations – car lines have tools ranging from ordinary hammers and switches to automatic welding and painting. Assembly lines in electronics can also vary greatly from manual mounting to auto-fitting, auto-soldering, and auto-testing equipment.
Set Up a Production Line
Setting up Production lines are a special type of product deployment. In the general sense, the term assembly line refers to the step-by-step installation associated with a material movement device. It is generally assumed that there are some changes and allowable process time that is the same for all work sites. Within this broad definition, there are important differences between linear types of movement. Some of these are material handling devices, line configuration, U-shape, straight, branching, relocation (mechanical), human intervention, product mix / single product or multiple products, worksite/worker characteristics may be sitting, standing, moving along the line, being on the line (and the length of the line) by several or more workers.
The range of products, partially or fully assembled on lines, includes products, household appliances, cars, airplanes, vending machines, garden tools, clothing and a wide variety of electronic components. It is possible to say that every product made up of many parts and produced in large quantities uses the assembly line to a certain extent. Lines are an important technology, and to understand the requirements for managing them, we need to understand how to balance them.
Balancing the assembly line
The most common assembly line is a moving conveyor that passes through a set of jobs at a uniform time interval called the cycle time (which is also the time between the consecutive arrival of products at the end of the line). At each job, work is performed on the product either by mounting parts or by performing assembly operations. The activity performed at each workplace consists of many separate activities, called tasks, elements, and work units. In general, these are grouped actions that cannot be separated on the assembly line without paying extra for additional movement.
The total work to be done in one workplace is equal to the sum of the tasks assigned to that workplace. The problem with the assembly line balancing is that it assigns all tasks to a group of jobs so that each workplace does not have more tasks than what can be accomplished in cyclical times, and thus reduces the number of idle units. The problem is compounded by the interrelationships between the tasks imposed by product design and process technology. These are the so-called primary connections that determine the order in which the tasks are to be performed during the assembly process.
Consistency in balancing the assembly line. The steps in balancing the assembly line are as follows:
Determine the sequence of interrelations between tasks using a diagram. The diagram consists of cycles and arrows. The cycles represent the individual tasks, the insoles indicate the sequence of the tasks.
Determining the required cycle time using the following formula:
Cycle = Production time per day / Production quantity per day (in units)
Determination of the theoretical minimum number of jobs (N) required to satisfy a single time cycle using the following formula:
N = Sum of time for all tasks / Time for one cycle
Defining a basic rule by which jobs will be assigned to jobs, and a second rule for disconnecting
Assigning assignments individually to the first job until the sum of all the tasks is equal to the cycle time, or a state in which no other task is possible due to time constraints or the sequence of activities. Repeat process for 2nd, 3rd, etc. jobs until all tasks are allocated.
Evaluation of the effectiveness of the balance thus created using the formula:
Effectiveness = Sum of all tasks (T) / Actual number of jobs (Na) x Cycle time (C)
If performance is unsatisfactory, rebalance using other task allocation rules
Find a balance that minimizes the number of jobs that corresponds to cycle times and sequence constraints.
Create a flowchart.
Determination of cycle time. They should be converted here in seconds since task times are in seconds.
C = Production time per day / Productivity per day = 60 sec. x 420 min / 500 frames = 25200/500 = 50.4 sec.
The theoretical minimum number of jobs required / the actual number may be greater /:
Nt = T / C = 195 seconds / 50.4 seconds = 3.86 seconds
Choosing rules for defining tasks.
Research has shown that some rules are better than others for certain problem structures. In general, the strategy will be to use a rule for assigning tasks that has either the most supporters or the longest duration, as they effectively limit the allowable balance. Reference: Definition and tasks of production management
In this case, we will use as our basic rule:
Assign tasks in the order of the largest number of subsequent tasks. Our secondary rule is to look for where there are links from the primary rule, ie.
Set tasks in the order of the longest operating time.
Efficiency = T / NC = 195 / 5×50.4 = 0.77 or 77%
Evaluation of the decision. A 77 percent efficiency indicates an unused 23 percent unbalance along the entire assembly line.
Is there a better balance? In this case, yes. Try balancing the line with rule b and breaking the rule’s links.
Division of tasks
Often, the longest task determines the shortest cycle time for the production line. This task time is the lowest time limit unless it is not possible to divide tasks between two or more jobs.
Let’s consider the following variant: Assume that an assembly line contains the following task times in seconds as follows: 40,30,15,25,20,18, 15. The line runs 7.5 hours a day and requires productivity of 750 units. daily.
The cycle time required to produce 750 units per day is 36 seconds / 7.5 hours x 60 minutes x 60 seconds / 750 /. How to handle a task that is 40 seconds?
There are several ways we can complete a 40-second task in a 36-second cycle. The options are:
Dividing the task. Can we divide the task so that we can produce parts that are produced in two jobs?
Sharing the task. Can the task be somehow distributed so that neighboring jobs fulfill part of the task? The difference with task division is that neighboring jobs work to help, not create details that consist of the entire task.
Using a Better Worker. Because the task exceeds cycle time by only 11 percent, a faster worker can manage a time of 36 seconds.
Overtime. Manufacturing at the rate of one piece every 40 seconds will result in the production of 675 parts per day, with 75 parts less than the 750 required. The amount of overtime required to achieve the additional 75 parts is 50 minutes / 75 x 40 seconds / 60 seconds.
Redesign. It is possible to redesign the product to reduce in a little time for the longest task. All Agile, Kaizen, and Kanban approach to product and project management suggest a redesign of the product to achieve perfection.
Other options for reducing task time include improving equipment, additional line support workers, changing materials, and heterogeneously skilled workers to work on the line as a team.
Flexible installation of the assembly line
As we saw in the example, balancing the assembly line often leads to uneven workplace tasks. Flexible assembly lines are a common way of dealing with this problem.
In the example of our example product company, the U-shaped line-sharing of the work at the base of the figure can help address this imbalance.
Computerized assembly line balancing
Companies that use the assembly line method often use computers to balance the lines. Most develop their computer programs, but commercial software packages are also common. One of these programs is the General Electric Line Assembly Configurator, which uses the stacked position weight rule when selecting jobs for jobs. In particular, this rule determines such a distribution of tasks according to their positional weight, which is the time for a task plus the times of the tasks that follow it. In this way, the highest positional task will be assigned to the first job. As is customary for software, the user has several options for how to solve a given problem.
Mixed assembly line balancing
To meet the needs for product diversity and prevent large inventory of a single product, many manufacturers plan several different production models in one day or week on the same assembly line. To indicate how this is done, let us assume that our production factory has a production line for drilling holes in the frame of a Model J trolley and a model K. The time required for drilling holes is different for each different product model. Modern management approaches are using the same assembly balancing management principles in the context of project management and product management.
Assume that the final assembly line requires the same number of models J and K. Assume also that we would like to develop a cycle time for a production line that is balanced for the production of equal quantities of frames J and K. Of course, we could produce a Model J frame for several days and then produce a Model K frame until equal quantities are produced. However, this would lead to unnecessary work in inventory handling. The development of management approaches in the USA clearly describe these requirements as “necessary and vital” for the whole production activities.
If we want to reduce the level of in-process inventory, we can create a cycle mix that reduces the level of inventory while maintaining the production of the same number of frames from both models.
Production time: 6 minutes for J and 4 minutes for K.
The day consists of 480 minutes (8 hours of 60 minutes).
6J + 4K = 480
Since the same number of both models should be produced, we produce 48J and 48K per day, or 6J and 6K per hour.
We can point out the following balanced model for our task
This line is balanced for 6 frames of each type per hour, with a miniclip of 12 minutes.
Another balance is J K K J K K J, with a time of 6,4,4,6,4,6. This balance produces three J’s and three K’s every 30 minutes with a 10-minute min/cycle (JK, KJ, KJ).
The simplicity of mixed balancing can be seen in Yasuhiro Mondon’s description of operations at Toyota plants:
Toyota’s end assembly lines are mixed product lines. Production in one day is determined by taking the number of cars in the monthly production plan, classified by specifications, and dividing by the number of working days in the month. Reference: Emergence and development of Industrial and Production management
Because of the production sequence for each day, the cycle time of each different car specification is calculated, and to have all the car specifications available, it appears in its own cycle time.
A technique for ensuring optimal allocation of workplace tasks
As we indicated and analyzed, the mixed line model seems relatively straightforward to use. This is because, in our example, the two models coincide in a common period, which in turn coincides with demand. From a mathematical point of view, designing a mixed line is very difficult and there is no technique to ensure optimal job scheduling. This is because the mixed model includes different batches, sequencing, preparation time for each batch, different workloads from line jobs, and differences in tasks. The problem is to design the assembly line and jobs and determine which tasks to perform in each.
The objectives of the mixed model line are to minimize inactivity and minimize the inefficiencies caused by changing models. Researchers have used integrated programming and simulations to solve these problems. They still cannot find the optimal solution to the real problems of production.
According to some authors, the best methods for finding good balances are heuristic-based programs. Heuristic programs use common rules, most of which seem logical. Examples of heuristic automotive assembly line rules would be to impose additional tasks on jobs that use the same tools as in the previous task.
Contemporary views on the assembly line
Indeed, the widespread use of the assembly line method in production has significantly increased production standards. Historically, the focus has always been on the full use of human labor, ie. assembly lines with minimal human factor inactivity should be designed. The use of equipment and facilities stood in the background as unimportant.
New perspectives on the assembly line have a broader perspective. The intention is to introduce more flexibility in on-line products, more variability in jobs (such as size, number of workers), and higher output quality through improved skills and equipment. The following chart shows the relationship between old and new production line ideas.