Group technology (GT) is a manufacturing technique in which similar parts are identified and grouped together to take advantage of their similarities in design and production. The goal of group technology is to improve productivity and efficiency in batch production.

Identifying Part Families

The first step in implementing group technology is to analyze the design and manufacturing characteristics of all the parts produced by a company. Parts with similar shapes, sizes, raw materials, production processes, and tooling requirements are identified and classified into part families.

Each part family represents a group of interchangeable parts that can be efficiently manufactured together. Some common methods for analyzing parts and identifying part families include:

• Visual inspection of part designs and blueprints
• Coding and classification systems such as Opitz coding, DCODE, and production flow analysis
• Computer-aided techniques like cluster analysis, correlation analysis, and heuristics

The optimal number of part families is determined based on the production volume and variety of parts produced. Companies usually identify between 100 to 500 part families.

Advantages of Part Families

Classifying parts into families offers several advantages:

• Parts can be grouped together based on their production sequence, reducing material handling and work-in-process
• Families can be assigned to work centers with appropriate processes, machinery, tooling, and skills
• Setup times can be reduced for producing similar components consecutively
• Inventory costs decrease as similar parts share raw materials, tools, and handling equipment
• Specialized work centers and workers develop expertise for part families over time
• Balancing production lines for families is easier compared to individual parts

Cellular Manufacturing

Once part families are identified, dedicated machine cells can be created for producing each part family. This is known as cellular manufacturing. It involves grouping all the materials, machinery, and tooling required for a particular part family into a cell.

Cells are designed to facilitate an efficient production sequence. They enable single-piece workflow where a part moves through successive operations within the cell. Common steps in designing machine cells include:

• Selecting machines required for a family based on processing requirements
• Arranging machines in a sequence or layout for optimized workflow
• Incorporating buffers, storage, and handling equipment
• Training workers for multiple machines and cross-functions in the cell

Some key benefits of cellular manufacturing include:

• Smoother flow of materials and components through the system
• Faster throughput and reduced lead times
• Lower work-in-process since batches are smaller
• Less material handling between work centers
• Greater flexibility in production scheduling

Design and Tooling Strategies

Group technology drives several tooling and design strategies for economic production in mid to high-volume batch manufacturing:

Standardization

Parts are designed with standard sizes and features to enable use of common tooling. Standardization also allows design modularization for creating product variants rapidly.

Simplification

Part features are simplified by eliminating unnecessary variations. This reduces tool complexity and allows quick tool setup changes.

Rationalization

The variety of raw materials, purchased parts, and tooling is rationalized by restricting them to the minimum levels needed. Excess variety increases production costs.

Special Tools and Handling Fixtures

Custom tools and fixtures suited to a part family are developed for specialized machine cells. They enable efficient machining, handling and quality control.

Implementation Challenges

While group technology provides many benefits, it also poses some implementation challenges:

• High investment needed for process re-engineering and cellular layouts
• Extensive analysis required for part coding and family identification
• Difficulty in accommodating product mix changes and new products
• Loss of flexibility since workers and machines become highly specialized
• Isolated cells prevent load sharing between different products

Careful change management and training is required to transition from traditional batch production to a cellular layout. Ongoing analysis of production data is also needed to continually improve cell performance.

Conclusion

Group technology is an essential lean manufacturing technique for mid to high-volume production. Classifying components into part families and manufacturing them in product-focused cells improves productivity, reduces costs, and speeds up delivery. However, successful implementation requires careful planning and transition. Companies must invest in GT as a long-term strategy to remain competitive.