Shojinka - line balancing

As always, today too we will take up a practice-oriented topic. Someone has surely come to you wanting to set up an assembly line. What must be paid attention to in that situation is our topic today. Let us start by establishing the current state. Look over what you have done, and see whether you too are making the mistakes we list below.

The most common mistakes;

. Choosing a time that is too short or too long for workstations

. Giving the information flow little thought, or none at all

. Not taking the material flow into account

. Applying 5S, or the placement of materials and tools, incorrectly

. Using the concept of "comfortable working" incorrectly

. Distributing the workload incorrectly .Incorrect work sequence

They sound familiar, don't they? We make these mistakes quite often. As a result of these mistakes, defective production increases, operations that create no added value increase, and motion and inventory increase, while productivity falls. Let us now examine these mistakes in a little more detail.

1. Choosing a time that is too short or too long for workstations: The workstation cycle time is chosen far too short, without taking Takt Time into account and out of various concerns, and production quantity, and therefore productivity, is expected to be high. In general, because of pressure from management, pressure on cost, or a concentration of orders, cycle times fall to as low as 5-7 seconds. Yet the employee on the line, continuously repeating the work they must do in that time, becomes exhausted, and in the end their productivity drops rapidly. Indeed, it is impossible to work for 440 minutes with a 7-second cycle time. Only a productivity of around 30% can be achieved.

   
   When the cycle time is 10 minutes or longer, it becomes difficult for the employee to keep repeating the work in the same way. Especially in assemblies with many parts, or in work with many operations, the employee forgets the work steps, forgets the materials, or does them incorrectly. In this way the productivity of the whole line falls again, and its cost rises.

    

2. Giving the information flow little thought, or none: Information is one of the resources an employee needs in order for a job to be possible. When information is missing, the employee waits for the information to arrive, or the product is taken off the line. Losses therefore increase again. Work standards, information about the product, information about the materials, and the flow of these should be planned in advance.
3. Not taking the material flow into account: A productivity loss of 20-30% comes from the material flow. If you look at the line carefully, you will see that employees spend part of their effort dealing directly with supplying material. In particular, because the employee is filled with a sense of intense and successful work by making movements related to material, they are unlikely to see these wasted movements. In very active and fast-paced jobs, an examination will certainly be required. Yamazumi analysis is a technique I would recommend for that examination.
4. Applying 5S, or the placement of materials and tools, incorrectly: This item, which is also linked to the line layout, at the same time ensures that the material flow is correct. How the line's need for material will be met is in fact already clear. The water spider technique should be used. With this technique, all that remains for the employee is to use the material. Material should be placed closest to the employee, and only in the amount needed at that moment. In this way the employee becomes completely independent of going to get material.

   Tools and equipment should likewise be placed so that they do not increase the employee's lost time. The aim is for the employee to be very comfortable. Every condition that tires the employee will affect losses directly. In this sense, 5S affects productivity directly. Many employees, managers, and engineers may have trouble understanding this. They may even show, and prove, that they work more productively with extra materials and tools. Your part is to make no concession on these principles, whatever happens.

5. Misunderstanding the concept of "comfortable working": Comfortable working is often confused with the area being large. Because a large area lengthens the times for motion and transport, comfortable working does not mean that the area is large.
6. Distributing the workload incorrectly: The workload is distributed incorrectly among employees, with various reasons put forward. If we give a few examples of these reasons: being the person who knows the job best, the job depending on the machine, and so on. Yet behind these reasons there is always the fear of losing the job.
7. Incorrect work sequence: Because work standards are often not established, creating the work sequence is left directly to the employee. For this reason an incorrect work sequence is used, and losses from transport, waiting, and extra processing increase.