Engineering

Group technology: Production efficiency in the Industry 4.0 era

From the time before the industrial revolution, to the present day, manufacturers have common goals: the production of a certain number of parts at a certain time on a certain cost.
31 march 2019

Production processes made progress from the use of single-piece handicraft production methods to mass production and the release of an increasing number of identical parts, that is, the manufacture of large consignment of a narrow nomenclature (HVLM). Recently, digital technologies used in programming, machine control and billet transportation systems have created a production environment known as Industry 4.0 that enables cost-effective production of a variety of parts in small quantities: small-scale production of a wide range (HMLV).

In the era of Industry 4.0, there is a tendency to focus on the latest production methods and digital technologies. However, the basis for maximum productivity and efficiency is still production efficiency. As a rule, in the current economic situation, manufacturers consider speed as a key indicator of production efficiency. The company receives a drawing, and the output appears processed billet. Manufacturers try to reduce the time between these two events. Efforts to improve speed are generally focused on the application of strategies – such as the principles of cost-effective production or the Six Sigma concept.

However, these strategies, which are successfully used in HVLM production, are not always effective in HMLV`s conditions. An important contribution to the optimization of the production of parts in the production of HMLV makes the method of group technology, in which the classification and distribution of parts into groups for processing allow to achieve the maximum of production efficiency.

Group technology

Group technology is a production strategy in which parts with similar characteristics, such as geometry, material, process, or quality standards, are classified into groups and processed in a common manner. Operations are planned for groups of parts, not for single billet.

Such an organization of production for processing groups of parts is often called a flexible production system. It became widespread in the 1980s, around the time when the era of HMLV production began. Manufacturers realized that the volume of consignments was decreasing, while the variety of parts and new materials was increasing. Enterprises faced with the need to produce various parts in relatively small consignments. The time spent on pre-production increased exponentially, and manufacturers aspired to take it under control.

Selection of groups of parts in the application of group technology is based on the standardization and classification of parts. Each of them is assigned a code of letters, numbers or combinations thereof, and each individual letter or number indicates a specific characteristic of the part or the method of production required for its manufacture. In figure 1, the 6th symbol of the code indicates the dimensions of the part, the 7th — the raw material, the 8th — the initial shape of the billet`s material, the 9th — the required level of quality. Symbols 3-5 describe the operations required to process the billet.

Figure 1 Parts` codes are used for production planning and cost assignment by comparison with a conventional, non-existent, so-called complex billet, as shown in the second line of figure 2 "Complex" in this case does not mean "difficult". This is a generalized billet, which presents all the possible characteristics, for example, high and low precision holes, pockets of large and small depth, side milled elements, etc. The parts in the first row of the figure are those that can be produced using the operations represented by the complex part in the second row. Summing up the necessary characteristics costs gives an idea of the total cost. This allows you to abandon the calculation of costs for the production of single parts.

Figure 2 Specialists of the planning and production Department and evaluation experts work with the drawing and set the cost by checking the characteristics of the billet with the properties of the complex billet. They also define other aspects of production, including the tool machine, the need to use cutting fluid, etc. In addition, the application of group technology by means of a complex CAM system allows you to further reduce the pre-treatment time of the billet. An additional advantage is the improved interaction of the departments of the enterprise, as they all work with one model of a complex billet.

The group technology method was originally based on experience: its developers consulted with technologists, programmers and designers to gather information about the cost of various production operations. While the method went into production in the 1980s, the comparison and systematization of personal experience and data was a process that resembles modern initiatives to create artificial intelligence.

In some cases, group technology requires shop area reorganization. The left side of figure 3 shows the traditional route of parts inside the shop, organized according to the machine functions, including turning, milling and grinding. However, if parts are grouped and processed in large groups using a flexible manufacturing system, as shown in figure 2, tools can be configured to optimize production flow and minimize movement of parts within the shop area. Each of the groups of parts is processed in the most efficient way without unnecessary transportation on the shop area. As a result, the manufacturing time of parts is significantly reduced.

Figure 3 As usual, the introduction of new concepts entails both advantages and difficulties. Group technology offers advantages in design, process planning and production time savings, but a number of complexities are also possible. First, the group technology method reduces flexibility to some extent. The traditional organization of the shop is more flexible with a significant increase in demand for a certain configuration of the billet, which creates difficulties for production. In the traditional organization for the manufacture of parts can be used other machines. Second, managing machine downtime can also be challenging. If part of the family of parts demand temporarily falls, machines will be idle with a flexible system of production.

Another possible difficulty arises from the implementation of group technology – the tendency to spend excessive time comparing coding systems. However, it is much more important than a specific coding system as such the company's ability to handle equipment and resources and clearly understand the required results. In this case, a simple and effective approach can be your own coding system created within the company. It is possible that the decision to reorganize the shop for machining families of parts will provide an additional increase in efficiency. Probably, it is easier for large companies to reconfigure the equipment, but small companies may face with economic constraints and other factors.

Faster and more accurate pricing

The group technology method in creating business proposals can increase revenue and profitability. An example of this is the manufacturer of parts for the aerospace industry in an HTML production environment with batch sizes from one to five blanks, which receives about 4,000 requests per year. The lack of time to analyze and calculate the cost of each part slowed down the pricing process, and the shop could create commercial offers for only 1500 out of 4000 possible requests. About 2600 orders were received. Using the analysis with application of group technology and the pricing for parts with complex procurement it became clear that the subcontractor could receive 3000 price proposals per year. More serious price offers attracted more orders, up to 3,200 annually. More importantly, the price calculated as cost plus profit was more than 30% lower than before the group technology concept`s application.

A faster and more accurate pricing process revealed two advantages. There have been fewer instances of erroneous price declines that have had a negative impact on profits, as well as erroneous overstatement that have led to customer dissatisfaction. The introduction of the group technology concept gave the manufacturer greater control over production results and prices and reduced the possibility of incorrect price offers.

According to the group technology, it is not necessary to consider the processing parameters of each billet: parts with similar characteristics are grouped and processed together. A good example of this approach: the shop produces pulleys for belt transmission. The diameters, width, profiles and grooves of the pulleys differed depending on the belt size. The changeover time for processing various configurations was about one and a half hours. Analysis of the process showed that for each changeover the machine was completely disassembled, all tools were removed, cleaned and stored. To process the next pulley, most of the same tools were re-installed in the machine. Using group technology, similar but not identical wheels were grouped together. Readjustment in this case included reconfiguring the CNC program, changing some processing parameters, and sometimes replacing the tool processing the profile of the grooves. Depending on the billet, the changeover time was reduced from an hour and a half to ten minutes. The main task was to convince the shop staff that the parts they produced belonged to the same group, and that they could be processed much faster. Figure 4

Conclusion

The organizational strategy of the group technology method (a major contribution to the development of which was made by Dave Morr from SECO branch in Australia) helps manufacturers to effectively solve the problems of HMLV production. Traditional productivity strategies – the principles of cost-effective production and the Six Sigma concept-provide proven benefits, especially for HVLM production, where operations can be fine-tuned to handle a large batch of identical parts. However, the production of small batches of a wide range continues to gain popularity due to advances in processing technology, as well as the development of design and management of digital products. The distribution of parts in groups and pooling operations pricing and processing method of group technology allows manufacturers to effectively cope with the challenges in an era of Industry 4.0. Figure 5

Group technology and Seco`s Consulting Services

The organizational strategy of the group technology method is an important element for achieving production efficiency and can provide significant assistance to manufacturers. However, competitiveness forces many manufacturers to focus exclusively on the timely production of a certain number of parts at a certain cost, and the time or competence for careful analysis and optimization of activities and production operations is not enough.

SECO has developed a new branch-level operation that is designed to help small companies that have the resources to develop production, but do not have sufficient funds to cover the high cost of manufacturing engineers or a large consulting company. Seco's Consulting Services help manufacturers to find a balance between the manufacturing process and business objectives on the one hand, and improving processing productivity and efficiency on the other. SCS are universal and work with tools of any manufacturers.

The first step in using SCS is to improve manufacturing efficiency (MEE), which includes process analysis, production system and production management.

SCS analyzes the capabilities of the company and identifies preparation tasks, processing and operation of equipment; identifies the main causes of problems associated with capabilities and assets, as well as the lack of knowledge of employees. Preliminary analysis includes software and standardization of methods and details. Problems in the field of processing are identified and solved by optimizing methods and fault repair. An understanding of the available funds and costs, as well as the software management of the tool, allows you to solve problems related to the operation of the equipment.

Within the SCS program educational services of Seco company (seminars and STEP courses) offer assistance in training of employees of the manufacturer. The main aspect of the service is to convince the employees of the shop to implement new strategies. A poster on the wall with a description of new approaches will have a minimal result, because most of the problems are not in the lack of knowledge of employees, but in their conviction that the traditional approach is the best. The key to success is to help employees to understand the benefits of new strategies and be disciplined while implementing them.