The basis of a group technology manufacturing system is the location, identification and nomination of part families within the universe of products handled by the organization and their subsequent assignment to a given group of equipment or machines for processing.
The main objective of group technology is to optimally exploit the characteristics that the grouped parts have in common: design, manufacturing methods and processes to create sets of machines called manufacturing cells, thereby improving the movement of parts within the plant during processing.
The concepts of group technology can be applied in different industrial areas, such as design and manufacturing. In the design of the parts, the grouping of form factors and other similar design elements is used to facilitate the creation of new parts, since it is only necessary to modify an existing part in the family to which it will belong, or to use the characteristics of some parts that also already exist in the family. In the manufacturing part it is possible to group the parts, according to the processes and operations that are required for their manufacture, creating production families.
In this topic you will address the background, advantages and disadvantages of group technology. By delving deeper into the family of parts concept, you will identify its positive impact on production economics when running medium volumes and with a wide variety of models, which contrasts with the time and effort required to classify and code the parts produced by an organization into families.5.1 Group technology background
Group technology is a production methodology for medium-volume parts. In the medium volume range, the production of pieces and parts is carried out in batches; this type of production, in batches, requires downtime to make adjustments for the change of the type of pieces in production and has high costs for the maintenance of the necessary inventories.
Group technology helps to reduce these disadvantages, knowing that, although the parties are different from each other, they also have points in common. Group technology takes advantage of the common and similar points in the design and manufacturing processes of parts, precisely using similar processes and tool settings to carry out their production.
Group technology implementation is feasible in the industrial organization using manual or automated techniques (Figure 1). The use of automation in a manufacturing system is also known as flexible manufacturing system.
Figure 1. Types of group technologies.
Group technology is a manufacturing system that identifies and groups parts with similarities in their design and manufacturing processes. The similarities of the parts make it possible to classify them into production families. By grouping the parts into families, a ratio between the number of parts and the number of families of the order of 500 can be achieved, for example, in some cases 1000 parts could be grouped into only two families. The idea is that in each family the processing route is similar.
By taking advantage of this similarity in the processes, significant improvements in the operation of the system are achieved. To make such improvements possible, the arrangement of equipment, machines and processes is carried out in the form of manufacturing cells within the plant, where each cell is designed to manufacture a family of parts, which means that the principle of specialization of operations is used.
Each manufacturing cell should include the machinery, tools and personnel necessary to optimally perform the production of parts in that cell, to the point of having the concept that each cell is a small factory within the factory. Figure 2 shows how cellular manufacturing and group technology have been adapted, together with the evolution of the assembly process on a production line.
Figure 2. Evolution of the assembly process in a production line.
Concept of family
The family of parts it is defined as a group of parts that have similar geometric characteristics or that have similar operations in the manufacturing process.
However, the above is not enough to include parts in the same family, the fact that two parts do not belong to the same family may be established by tolerances, the volume of production and the materials that make them up.
For example, two parts that are geometrically identical do not necessarily belong to the same family, since one of them may be made of plastic, manufactured in high quantities and with very wide tolerances; while the other may be made of iron, with low production and very close tolerances.
This can be clearly seen by imagining the machines that would manufacture these parts, although they are the same in shape, the machinery for processing plastic will not be the same as that for processing iron, and the tighter the tolerances accepted, the more expensive and complex the machinery will be.
5.2 Advantages and disadvantages of group technology
Figure 3 shows the set of advantages that the application of group technology brings in a manufacturing system:
Figure 3. Advantages of Group technology.
The application of group technology makes it possible to standardize the design of the parts, thus preventing the designs from being duplicated. It is possible to develop new designs of parts using designs already made of similar or similar parts as a basis, taking design features of parts that have already disappeared from production.
This can translate into saving a lot of time and labor. When you have a digital database, it is possible to quickly determine if you have similar parts from which to reuse their design features.
The part designer experience and the process planner can be stored in the database. Therefore, the experience information possessed is easily retrievable and made available to personnel new to the organization in the form of past process designs and plans.
Once a database is available, it is very easy to make cost calculations and obtain statistical information about material usage, processes, production volumes, among others. It is also possible to achieve standardization and scheduling of process plans, production orders can be organized by groups for efficient manufacturing and equipment utilization is increased.
Preparation times can be drastically reduced by better planning; in addition, the quality and consistency of the products is improved. By using the part families, the tools and machines necessary for their manufacture can be shared and the programming can be designed to automate the process in greater depth.
Combining manufacturing by production families, also known as highly repetitive manufacturing, with other technologies (such as CAD/CAM and computer integrated systems) offers the great opportunity to greatly improve productivity and reduce the costs involved in batch production, bringing them to levels similar to those of mass production. The potential savings from implementing this type of systems can reach up to 75% of the original costs (Groover, 2018).
Although several advantages of group technology have been mentioned, it is important to consider some key elements that must be solved to achieve its implementation in industrial organizations:
The identification and coding of part families: there is a large number of parts that are manufactured in the plant, so achieving their identification and coding involves a great effort of the personnel in charge of it. |
The task can take considerable time. |
A cost of proportional magnitude associated with such an effort. |
Reorganization of physical arrangement of machines: it poses another drawback on the production floor, since, depending on the type of equipment used, it will also have a cost associated with such a reorganization, which can sometimes be very high. |
Scheduling the movement and relocation of machines: it is important to carry out this planning in such a way that it does not disrupt current production. |
Below is the process of generating a part family with Siemens NX 12.0 software:
Click each step for more information.
Have a part model:
This screen was obtained directly from the software that is being explained on the computer, for educational purposes.
Click on the Part Family Tool.
This screen was obtained directly from the software that is being explained on the computer, for educational purposes.
Select with a double click the dimensions that will help you to form the family of parts. Also choose the folder where these components will be saved. Then click on Create a spreadsheet.
This screen was obtained directly from the software that is being explained on the computer, for educational purposes.
In the spreadsheet you add the data that the variation of dimensions needs.
This screen was obtained directly from the software that is being explained on the computer, for educational purposes.
Once the new dimensions have been added, click on ADD-ONS-PartFamily-Save Family. And now you already have a family of parts.
This screen was obtained directly from the software that is being explained on the computer, for educational purposes.
Now you know the necessary premises for the establishment of group technology in a manufacturing system, the identification of families of parts among all the products of the organization, in order to group them in such a way that a family can be manufactured in a manufacturing cell, which is nothing more than a physical grouping of machines, equipment and processes that are capable of producing from start to finish the parts grouped in the family that has been assigned.
When group technology is unified with supporting technologies (such as CAD/CAM and computer integrated systems), the manufacturing system can reach very high productivity levels, improving system operability, shortening design times and simplifying this task, increasing product quality, decreasing delivery times and improving workers' job satisfaction levels.
To start the implementation of group technology, the classification and coding of the parts to group them into families should go first. You will study this topic in the next sessions, and then move on to training inside the manufacturing cell plant. In summary, companies that have the discipline and perseverance to implement group technology in their manufacturing systems can obtain great tangible and intangible benefits, and those who delay in accessing this type of manufacturing will be seriously surpassed by competitors who do.
In the next topic you will review the methods used for the development of part families.
Make sure that you:
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To learn about group technology, check out the following video:
To learn about part family, check out the following video:
To learn more about cellular manufacturing, we recommend reading:
To learn more about group technology, we recommend reading:
The student will simulate a manufacturing system that includes the principles of group technology, starting from the modeling of a product and the generation of a family of parts.
To apply the fundamentals of group technology in the design and simulation of simple manufacturing systems.
