CHAPTER 1
FACILITIES. LAYOUT AND MATERIALS HANDLING
1.0 Introduction
The aim should be to locate the factory optimally in an area where readily qualified labour is available and there is a ready market for the goods produced. The plan of the factory and the layout of its facilities influence its effectiveness.
1.1 Siting of a company
To obtain a feasibility study for the establishment of a manufacturing factory, the selection and cost of its location used must be assessed. The factors that affect its location are
(i) availability of land and its cost
(ii) availability of suitably qualified local labour and its likely cost
(iii) nearness to markets for the end product of the factory
(iv) pertinent government policies and degree of security that apply locally
(v) local availability of services like transportation, electricity, natural gas, or potable water.
In a developing country like Nigeria, the available land is plentiful, but is relatively more expensive in city areas like Abuja, Lagos, and Port Harcourt. Hence, to reduce cost, land outside the cities is often sought.
In Nigeria, labour is cheap per hour but it becomes more expensive as one moves towards the cities. Nevertheless to reduce overall costs, transportation costs should be reduced, so the site of the factory should be close to a large market for its products. In developed countries, government policies influence significantly the locations of factories. For instance, factories are set up in high-unemployment areas to comply with the national development policy for the country. In Nigeria, the siting of a factory is often based on political rather than management considerations. Therefore, many government-owned companies exist in economically non-viable locations, for example, the refinery and the fertiliser plant at Kaduna. However, private investors prefer to start companies in their own localities.
Reliable electricity supplies and an adequate transportation infrastructure are essential for most companies. Unfortunately, in Nigeria, companies too often have to provide standby generators, thereby increasing production costs. This is one of the reasons why made-in-Nigeria goods tend to be more expensive than the corresponding imported ones, despite far lower local labour costs.
1.2 Plant Layout
Production problems associated with poor layout can be the
* tendency of the control to be more complicated
* congestion of personnel and materials
* production-line bottlenecks
* excessive rehandling of materials
* longer transportation lines
* greater probability of accidents
* lower employee performances
Wise layout should facilitate overcoming such problems.
1.1.1 Types of plant layout
The aim should be the minimisation of production cost while simultaneously satisfying both technical and management requirements. Some of the challenges are
* producing the desired rate of output
* minimising the production of scrap
* avoiding the occurrence of accidents
* maximising equipment usage
* reducing work in progress
* reducing transportation costs incurred
* making each worker more responsible and hence productive.
Achieving these objectives may require either modifying existing plant or introducing new plant.
1.1.1.1 New layout design
A simple formula that can be used to calculate the number N of machines of the same type that may be required in the layout is N = TP/HC
where T = standard time per unit end product per machine (hours)
P = required production of end products per day
H = number of production hours per day
C = utilisation factor for the plant.
So, for example if (i) a product requires processing on a lathe for 15 minutes; (ii) the required daily production P of the product is 100 units, (iii) the company runs 2 shifts per day, of 8 hours each; and (iv) the plant utilisation factor C is 0.75, calculate the number of machines required to satisfy the daily requirement.
Solution: Standard time per unit, T = 0.25 hr
Required production per day, P = 100
Number of production hours per day, H = 8 × 2 = 16
Therefore, number of machines, N required = (0.25 × 100) / (16 × 0.75) = 2.08
In practice, it will be necessary to install 3 machines.
From the calculation of the required number of machines and ensuring ergonomic principles, the required space is calculated. As stated by Reed1 in determining the floor area required, the following factors need to be considered:
* area required for each machine and its operation
* storage volume requirement for tools, jigs, and fixtures
* each operator's space requirement
* space for incoming-material storage
* space for handling facilities
* space for machine servicing and maintenance requirements
* each plant's service requirements, such as illumination and ventilation.
Space is also required for other activities such as inventory; materials and quality control; storage; transport; reception and dispersal areas for goods; plant maintenance; canteen, washrooms and toilets; and administrative offices.
Departmental Arrangements
(I) Flow pattern of a product: This important consideration for the effective operation of a facility is affected by
* number of components in the manufactured product
* number of operations required in the manufacture of each component
* sequence of these operations
* number of sub-assemblies
* total number of units to be produced
* necessary flows of products between work areas
* amount and shape of space available
* types of processes
* types of flow patterns
* location of service areas
* location of production departments
* material storage
* flexibility desired
* the building's configuration.
Some of these factors may be difficult to quantify. An important factor influencing flow efficiency is the total distance travelled multiplied by the volume.
(II) Non-computerised methods
Three of the non-computerised quantitative methods for departmental layout arrangements are
* spiral analysis
* straight-line analysis
* travel charting
(III) Computerised methods
Several of the computerised methods commonly applied in industrial applications are
* -CRAFT (Computerised Relative Allocation of Facilities Techniques)
* CORELAP (Computerised Relationship Layout Planning)
* ALDEP (Automated Layout Design Program)
* COFAD (Computerised Facility Design)
1.1.1.2 Improved layout design
There are four possible re-layout challenges:
* new layout, no restrictions at all
* new layout within an existing building
* new replacement layout to be phased into an existing layout
* extension/reduction of an existing layout
In introducing a new manufacturing-plant layout, the principal physical constraint is that of the shape and size of each work - centre. The rearrangement of an existing layout adds a whole new dynamic character to the layout problem. The dynamic influence arises when considering withdrawing old manufacturing facilities. Also, installing improved technological facilities needs to be undertaken with the least disruption to production.
1.1.2 Factors leading to layout changes
These can result from improved manufacturing-technologies becoming available and/or changes in the market demand.
Changes in the market and products
Batch manufacture is typified by frequently changing products, on the same production line. The substitution of electronics for electromechanical controls has revolutionised plant layout in modern factories. In the developed world, there is a general tendency for manufacturing companies to move into higher added-value production. Thus more complex products, relying more frequently on advanced manufacturing technology, are appearing in the desire for higher profitabilities. As individual wages tend to be higher in developed world, more robots are used there to replace humans.
Changes in Manufacturing Technology
The problem of modifying or replacing an existing layout is more complicated when the production is carried out in batches, because it is this type of manufacturing that has seen the introduction of substantially new systems and procedures based upon the use of advanced technology. Amongst the examples of this type of change are
* the introduction of group-technology-based manufacture in the 1960s and 1970s
* the move from numerical control (NC) to computerised numerical control (CNC) and in the 1980s to direct numerical control (DNC)
* the introduction of robotics and automated guided vehicles (AGVs) as the basis of computer-controlled materials handling
* the development of flexible manufacturing-processes using DNC, AGV, and robotics technology
* the availability of more powerful interactive computers for production planning, online monitoring and control, as well for as automated quality assurance.
Batch manufacturing layouts are undergoing significant technological and managerial transformations as the move is made from traditional to advanced manufacturing systems. These changes are accompanied by modifications in the layout of facilities.
1.1.3 Classic layouts of production equipment in engineering factories
Three traditional layouts are illustrated in figures 1.1 to 1.3 are common.
One-off layout
For large one-off products, the product remains stationary, with manufacturing equipment and labour moving to and around the product, i.e. the reverse of what happens during the normal batch-production process. For the manufacture of small one-off products, the key is versatility, with general-purpose manufacturing equipment and a skilled workforce being employed to complete each unique task. After each task is completed, a new layout may be created for the next product as illustrated in figure 1.1, i.e. each work centre may be relocated within the factory to suit the product being manufactured.
Batch-Manufacturing Process Layout
The machine tools and press facilities are usually grouped according to process and used to manufacture continuously batches of products as shown in figure 1.2.
When continuous production runs for particular products can be identified, then a more specialised layout, with groups of machines serving known product ranges, can be employed as shown for example in figure 1.3.
For the layout of figure 1.3, the main advantages are
* less total materials handling required
* shorter total production time
* simplicity of production controls
The main limitations are
* less work in progress
* consistent and substantial product demand required
* duplication of work centres
In general manufacturing, machine tools and facilities should be optimally grouped and then optimally located in the factory. To ignore pre-grouping could reduce considerably manufacturing effectiveness.
Modern manufacturing systems
With the introduction of group technology, systems capable of dealing with the complexities of batch manufacture were introduced. By this process, using computer analysis, families or groups of similar components that can be produced together are first identified. Specialist product-oriented manufacturing cells are then introduced to the facility layout in order to obtain the benefits of grouped manufacture. Once again the main benefits of group technology are related to organisational and manufacturing considerations, e.g. reducing the required inventory levels, and not to potential layout criteria.
Recently, advances in computer control of manufacturing equipment, with the development from numerical control (NC) through to direct numerical control (DNC), have led to the evolvement of flexible manufacturing systems (FMS), which are highly automated, with respect to product transport, integrated product loading and manufacture under computer supervision. The introduction of FMS raises the question of integration between the FMS and conventional layout zones as they may be incompatible with respect to operational procedures.
1.2.5 Evaluation of layouts
The following costs are associated with changes of manufacturing systems:
* work-centre relocation
* materials movement
* potential production lost
* fixed costs (see below)
* site preparation
Examples of fixed manufacturing cost might include
* capital cost and its annual amortisation
* indirect labour costs
* indirect utilities (lighting, heating, etc.)
* local government taxes and building rental charges
Minimising only materials movement costs as the criterion for solving the facilities re-layout problem is unrealistic. If the best possible financial return is the main objective of an efficient layout, then the expected financial return is the function of all the layout costs. The relocation involves the design, construction, and installing of the new layout.
The design problem requires realistic layout zone and work centre physical representations. These are absent from many existing computer programs for layout for batch mode production; only limited use is made of these programs.
Installing a new layout
The transition from an existing to a new arrangement can be made
* during long breaks, when no production is required
* by stopping production to install the new layout in one intensive period
* during downtime between production periods.
Introducing a new layout during a staff vacation eliminates disruption, but may not be the most appropriate time; a major constraint on this changeover policy may be the need to wait for the annual holiday periods.
An alternative rapid changeover approach is to halt production in order to introduce the new layout. This approach avoids the need to wait for a natural break in production, but can be very expensive because of the production losses incurred.
The third approach, as the phased changeover method, involves making a series of limited changes over an extended period during production and/ or outside production time. This incurs a longer period of disruption and so delays obtaining the full benefit of the new layout. By this approach, however, production loss can be reduced and capital investment phased in over a period of time. Making changes while maintaining production requires detailed planning and, in particular, involves involving predicting the optimal non-production periods available for implementation of the relocation. It incurs several layout problems, such as
* During the transition period, a series of intermediate relocations have to be implemented.
* Some work centres may be displaced and need temporary storage for the affected plant.
* Obsolete work centres may need to be phased out.
* It may become necessary intermittently to phase in new work centres just to increase production or improve production efficiency.
1.3. Material-handling systems
1.3.1 Introduction
Materials-handling systems are usually classified according to
* equipment, such as conveyors, cranes, elevators, hoists, monorails, industrial vehicles, containers, and supports as well as auxiliary equipment
* material or load configurations for unit, bulk, or liquid handling.
* production method, using manual, mechanised, automated and/ or mass-production job shop handling-system
* function, such as transportation, elevating, conveying, transferring, or self-loading systems.
1.3.2 Principles of Material Handling
The following should be considered when designing a material-handling system:
* Plan all material handling and storage activities to try to obtain the maximum overall operating effectiveness.
* Integrate as many handling activities as is practical into a coordinated system of operations, covering the activities concerning vendor, receipt of goods, storage, production, inspection, packaging, warehousing, shipping, transportation, and eventual customer.
* Devise an operation-sequence chart and hence equipment layout in order to achieve an optimisation of material flow.
* Simplify handling by reducing, eliminating, or combining unnecessary materials movements and/or equipment.
* To reduce energy costs, utilise gravity to move material(s) in the desired direction wherever practical.
* Strive to achieve the optimal utilisation of the available building-space.
* Increase the quantity, size, or weight of unit loads or flow rate.
* Mechanise handling operations as far as feasible.
* Introduce automation for production, handling, and storage functions.
* Consider the various aspects for handling and procedures, the materials, the required movement(s), and the methods to be used.
* Standardise the handling methods chosen as well as harmonise the types and sizes of equipment used.
* Use methods and equipment that are adaptable in order to be able to perform a variety of tasks, as well as be appropriate for applications where special purpose equipment is not justified.
* Reduce the ratio of dead weight of the mobile handling-equipment to the weight of the load carried.
* Plan for the optimal utilisation of both the handling equipment and the available manpower.
* implement preventive maintenance and the optimal schedule of repairs to all the handling equipment.
* Replace obsolete handling-methods and equipment provided, thereby effectiveness of operations will be improved sufficiently as justified by overall economics.
* Use wiser material-handling activities to improve the control of production, inventory, and order handling.
* Use handling equipment to help achieve the desired production throughput.
