Part families and cellular manufacturing.
GT exploits the part similarities by utilising similar processes and tooling to produce them. This results in parts being grouped into families and machines being grouped into cells
• Each cell specialises in the production of a part family and this is termed Cellular Manufacturing
• Cellular manufacturing can be implemented by manual or automated methods but when automation is the prevalent control method then the term Flexible Manufacturing system (FMS) is used
When to use GT and Celluar Manufacturing
1. The plant currently uses traditional batch production and a process type layout.
2. The parts can be grouped into part families
Foressable problems in implementing GT
1. Identifying the part families
2. Rearranging production machines into GT cells
3. Managing the change and systemising the rest of the enterprise
4. Implementing computerised systems for management
5. Changing design methods from “from scratch design” to methodologies that work alongside Group Technology for example using part libraries and parameterised modelling.
Ways to identify part families.
1. Visual inspection Using best judgment to group parts into appropriate families, based on the parts or photos of the parts
2. Parts classification and coding Identifying similarities and differences among parts and relating them by means of a coding scheme
3. Production flow analysis Using information contained on route sheets to classify parts
Reasons to use a coding system to classify components into families.
- Design retrieval
- Automated process planning
- Machine cell design
What attributes are coding systems normally based on?
- Design attributes
- Part manufacturing attributes
- Both manufacturing and part design attributes
List some part design attributes.
- Major dimensions
- Basic external shape
- Basic internal shape
- Length/diameter ratio
- Material type
- Part function
- Surface finish
List some part manufacturing attributes.
- Major process
- Operation sequence
- Batch size
- Annual production
- Machine tools
- Cutting tools
- Material type
What is the Opitz part classification system?
A quantitive part classification system used to devide parts into families. It utilizes a coding system.
Digits 1 through 5 = form code – primary shape and design attributes (hierarchical structure)
Digits 6 through 9 = supplementary code – attributes that are useful in manufacturing (e.g., dimensions, starting material)
Digits 10 through 13 = secondary code – production operation type and sequence
What are the typical objectives of cellular manufacturing?
To shorten manufacturing lead times
• To reduce WIP
• To improve quality
• To simplify production scheduling
• To reduce setup times
What is the composite part concept?
A composite part for a given family is a hypothetical part that includes all of the design and manufacturing attributes of the family
In general, an individual part in the family will have some of the features of the family, but not all of them
A production cell for the part family would consist of those machines required to make the composite part
Such a cell would be able to produce any family member, by omitting operations corresponding to features not possessed by that part
What are the 4 steps of cluster flow analysis?
1. Data collection – operation sequence and machine routing for each part
2. Sortation of process routings – parts with same sequences and routings are arranged into “packs”
3. PFA chart – each pack is displayed on a PFA chart Also called a part-machine incidence matrix
4. Cluster analysis – purpose is to collect packs with similar routings into groups Each machine group = a machine cell
What are the 4 main manufacturing cell designs?
1. Single machine
2. Multiple machines with manual handling Often organized into U-shaped layout
3. Multiple machines with semi-integrated handling
4. Automated cell – automated processing and integrated handling Flexible manufacturing cell Flexible manufacturing system
Draw a U-Shaped machine cell.
Draw a Loop-Layout
Draw a rectangular-layout
Draw a diagram of the 4 types of moves in a mixed model production system.
What are the different ways of forming a machine cell?
- Informal scheduling and routing of similar parts through selected machines to minimize setups •
- Virtual machine cells – dedication of certain machines in the factory to produce part families, but no physical relocation of machines
- Formal machine cells – machines are physically relocated to form the cells
What are the benefits of Group Technology?
Standardization of tooling, fixtures, and setups is encouraged
Material handling is reduced- parts are moved within a machine cell rather than the entire factory
Process planning and production scheduling are simplified
Work-in-process and manufacturing lead time are reduced
Improved worker satisfaction in a GT cell
Higher quality work