Once parts have been grouped into part families by parts classification and coding or production flow analysis, the next problem would be determining how to arrange the machines in the shop.
Facility layout, also known as plant layout, refers to the physical arrangement of production facilities. It is the configuration of departments, work centres, and equipment in the conversion process.
The objective of facility layout is to design a physical arrangement that most economically meets the required output quantity and quality.
There are three basic ways to arrange machines in a shop. They are:
1.Line (or product) layout,
2.Functional (or process) layout, and
3.Group (or combination) layout.
1. Line (or Product) Layout
In a line layout, the machines are arranged in the sequence as required by the product.If volume of production of one or more products is large, the facilities can be arranged to achieve efficient flow of materials and lower cost per unit.Figure depicts a typical line layout.
Product or line layout
Suitability: This form of layout is suitable for the continuous mass production of goods as it makes it possible for the raw material to be fed into the plant and taken out finished product on the other end.
Advantages and disadvantages of line layout
â Smooth and continuous work flow.
â Less space requirements for the same production volume.
â Automatic materials handling possible.
â Lack of flexibility. That is, product changes require major changes in layout.
â Large capital investment.
â Lesser work-in-process inventory.
â Reduced product movement and processing time.
â Simple production planning and control, better co-ordination.
â Less skilled workers can serve the purpose.
â Dedicated or special purpose machines.
â Dependence of the whole activity on each part. Breakdown of any one machine in the sequence may result in stoppage of production.
2. Functional (or Process) Layout
The functional layout is characterized by keeping similar machines/ operations at one location, i.e., all lathes at one place, all milling machines at another place. Thus in process layout machines are arranged according to their functions.
Suitability: This type of layout is suitable for job order/non-repetitive type production.
Merits and demerits: Table 3.8 summarises the advantages and disadvantages of the functional layout.
Advantages and disadvantages of process layout
â Flexibility in assigning work to equipment and workers.
â Better equipment utilisation.
â Comparatively less number of equipment needed.
â Better product quality because of specialisation.
â Variety of job makes the job challenging and interesting.
â Automatic material handling is extremely difficult.
â Difficult production planning and control.
â More space is required.
â Large work-in-process inventory.
â Higher grades of skill required.
â Lower productivity due to number of setups.
3. Group (or Combination) Layout
A group layout is a combination of the product layout and process layout. It combines the advantages of both layout systems.
In a group layout, machines are arranged into cells. Each cell is capable of performing manufacturing operations on one or more families .
Group technology layout (with two cells)
If there are m machines and n components, in a group layout, the m-machines and n -components will be divided into distinct number of machine-component cells (groups) such that all the components assigned to a cell are almost processed within that cell itself. Here, the objective is to minimize the intercell movements.
Suitability: A group layout is preferred for batch type production, where the products are made in small batches and in large variety.
Advantages and disadvantages of group layout
â Group technology layout can increase:
â This type of layout may not be feasible for all situations. If the product mix is completely dissimilar, then we may not have meaningful cell formation.
– component standardization and rationalisation
– reliability of estimates
â Comparatively high investment in equipments is required.
– effective machine operation.
– costing accuracy
â Higher grades of skill are required.
– customer service
â Groupings of machines may lead to poor utilization of some machines inthe group.
– order potential
â Group technology layout can reduce:
– planning effort
– paper work
– setting time
– down time
– work in process
– work movement
– overall production times
– finished part stock
– overall cost
Benefits of Group Technology:
Group technology, when successfully implemented, offers many benefits to industries. GT benefits can be realised in a manufacturing organisation in the following areas:
2.Tooling and setups
4.Production and inventory control
6.Management and employees.
1.Benefits in Product Design
The main advantages of GT for product design come in cost and time savings, because design engineers can quickly and easily search the database for parts that either presently exist or can be used with slight modifications, rather than issuing new part numbers.
A similar cost savings can be realised in the elimination of two or more identical parts with different part numbers.
Another advantage is the standardisation of designs. Design features such as comer radii, tolerances, chamfers, counter bores and surface finishes can be standardized with GT.
2.Benefits in Tooling and Setups
In the area of tooling, group jigs and fixtures are designed to accommodate every member of a part family. Also work holding devices are designed to use special adapters in such a way that this general fixture can accept each part family member.
Since setup times are very short between different parts in a family, a group layout can also result in dramatic reductions in setup times.
3.Benefits in Materials Handling
GT facilitates a group layout of the shop. Since machines are arranged as cells, in a group layout, the materials handling cost can be reduced by reducing travel and facilitating increased automation.
4. Benefits in Production and Inventory Control
GT simplifies production and planning control. The complexity of the problem has been reduced from a large portion of the shop to smaller groups of machines. The production scheduling is simplified to a small number of parts through the machines in that cell.
In addition, reduced setup times and effective materials handling result in shorter manufacturing lead times and smaller work-in-process inventories.
5. Benefits in Process Planning
The concept of group technologyâ”parts classification and codingâ”lead to an automated process planning system. Grouping parts allows an examination of the various planning/route sheets for all members of a particular family. Once this has been accomplished, the same basic plans can be applied to other members, thereby optimizing the shop flow for the group.
6. Benefits to Management and Employees
It is understood that GT simplifies the environment of the manufacturing firm, which provides significant benefit to management.
Simplification reduces the cumbersome paper work.
Simplification also improves the work environment.
In the GT work environment, the supervisor has in-depth knowledge of the work performed and better control.
The GT environment provides greater job satisfaction because it leads to more employee involvement in decision making, personalized work relationships, and variety in tasks.
In the GT work environment, the workers are able to realise their contributions to the cell more clearly. This realisation leads to better performance, higher morale, and better work quality.
3.6 Cellular Manufacturing
It is an application of group technology in which dissimilar machines have been aggregated into cells, each of which is dedicated to the production of a part family.
Primary advantage of CM implementation is that a large manufacturing system can be decomposed into smaller subsystems of machines called cells. Cells are dedicated to process part families based on similarities in manufacturing requirements.Parts having similar manufacturing requirements can be processed entirely in that cell.
In addition, cells represent sociological units conducive to team work which lead to higher levels of motivation for process improvements.
Benefits associated with the application of CM include improved market response, more reliable delivery promises, reduced tooling and fixtures, and simplified scheduling.
Literature surveys confirm substantial benefits from implementing cellular manufacturing in manufacturing industries.
Reasons for implementing manufacturing cells
Reduce manufacturing lead time
Improve part and/or product quality
Reduce response time for customer orders
Reduce more distances/more times
Increase manufacturing flexibility
Reduce unit costs
Simplify production planning and control
Facilitate employee involvement
Reduce set-up times
Reduce finished goods inventory
Benefits of cellular manufacturing
Design Considerations Guiding the Cell Formation
We know that cell formation is the early activity in the cell design process where part families and associated machine groups are identified. Cell formation is influenced by a variety of objectives and concerns.
The table lists the important design considerations that should be taken into account during cell formation.
Parts/products to be fully completed in the cell
Higher operator utilization
Fewer operators than equipment
Balanced equipment utilization in the cell
The number of part/product assigned to the cell
Unidirectional (linear) material flows
The number of cell operators
High utilization on expensive equipment
The number of workstations/machines in the cell
High equipment flexibility to ease new product introduction over time
High flexibility in selecting alternative routes through the cell
Design considerations guiding cell formation
3.7 Process Planning
Product design for each product has been developed in the design department. To convert the product design into a product, a manufacturing plan is required. Activity of developing such a plan is called process planning.
Process planning consists of preparing set of instructions that describe how to manufacture the product and its parts.
The task of process planning consists of determining the manufacturing operations required to transform a part from a rough (raw material) to the finished state specified on the engineering drawing.Also known as operations planning.
Is the systematic determination of the engineering processes and systems to manufacture a product competitively and economically.Is a detailed specification which lists the operations, tools, and facilities.Is usually accomplished in manufacturing department.
Process Planning Defined
It can be defined as âan act of preparing a detailed processing documentation for the manufacture of a piece part or assembly.âAccording to the American Society of Tool and Manufacturing Engineers, âProcess planning is the systematic determination of the methods by which a product is to be manufactured, economically and competitively. â
It consists of devising, selecting and specifying processes, machine tools and other equipment to transform the raw material into finished product as per the specifications called for by the drawings.
Process Planning Vs Product Planning
It is concerned with the engineering and technological issues of how to make the product and its parts.It specifies types of equipment and tooling required to fabricate the parts and assemble the product.
It is concerned with the logistics issues of making the product.
It ss concerned with ordering the materials and obtaining the resources required to make the product in sufficient quantities to satisfy demand for it.Production is done only after the process planning.
Importance of Process Planning
Process planning establishes the link between engineering design and shop floor manufacturing.
Determines how a part/product will be manufactured,the important determinant of production costs and profitability.
Production process plans should be based on in-depth knowledge of process and equipment capabilities, tooling availability, material processing characteristics, related costs, and shop practices.
Economic future of the industry demands that process plans that are developed should be feasible, low cost, and consistent with plans for similar parts.
Process planning facilitates the feedback from the shop floor to design engineering regarding the manufacturing ability of alternative.
3.7.1 Role Of Process Planning In Cad/Cam Integration
Most firms are extensively using CAD techniques to design their parts/products.
Use of CAM techniques such as computerized numerical control (CNC), and part programming to manufacture their parts/products have become common.one of the big problem in these firms (using CAD and CAM techniques) is that there is very little communication between design and manufacturing.
Emergence of CAD/CAM integration has improved communication between design engineering and manufacturing engineering .
Process planning is the link between product design and manufacturing, Plays a vital role in CAD/CAM integration.
Process planning converts the product design into the manufacturing plan required to make the product.
Automated version of process planning is âcomputer-aided process planning (CAPP)Without automated process planning, CIM would be impossible.Automated process planning provides the link between CAD and CAM.
Group technology and process planning are two essential elements in CAD/CAM integration. GT provides a basis and a methodology for design and manufacturing communications, Automated process planning provides a means to facilitate this communication and remove the âwallâ between design and engineering.
Details of a Process Plan
Detailed process plan usually contains the route, processes, process parameters, and machine and tool selections.all Information required for process planning:
To prepare a process plan (also called as route. sheet), we require the following informations:
Assembly and component drawings and bill of materials (part list):
This detail give the information regarding the general description of part to be manufactured, raw material specification, dimensions and tolerances required, the surface finish and treatment required.
2.Machine and equipment details:
(i)The various possible operations that can be performed.
(ii)The maximum and minimum dimensions that can be machined on the machines.
(iii)The accuracy of the dimensions that can be obtained.
(iv)Available feeds and speeds on the machine.
3.Standard time for each operation and details of setup time for each job.
4.Availability of machines, equipment and tools.
Overall development of processing plans