Ford pioneered the concept of assembly line used for mass production. Mass production is wrongly equated with heavy production meant for teeming millions. However, mass production is a concept. It believes in break-up of a task into its simplest possible elements. These elements are then grouped as per production norms. Assembly line consists of work stations in sequence. At each work station, a carefully designed portion of work is done (in a soft drink plant, for examples, filling of bottles). In this system, similar parts on assembly line are interchangeable and replaceable. This enables a production of a large quantity and maintenance too of large quantities.
On assembly line, the material moves continuously at a uniform average rate. It reaches the various work stations, where a portion of work is done. To illustrate, we have products like Automobile assembly, TV assembly, computers assembly, toys assembly etc.
Assembly line operations of materials can be manual or can be conveyor belts carrying the part at pre-decided speed so that there is sufficient time at each Work Station to perform the allotted task. The conveyor belts are of belt type, chain type, overhead type, pneumatic type or screw type. Assembly lines on one hand can be 100% manual or on the other hand 100% automatic, with many different semi-automatic possibilities between these two extremes. The same principle however is at work in an automatic or non-automatic or semi-automatic process, changing only the labor content of the task.
Mass Production: Suitability
Mass production refers to a large quantity of production with standardized products having less variety. Ideally, it should be a single standard product (no changes in design) manufactured on a continuous basis over a period of time. So the determining factor is the demand which makes us opt either for continuous or batch type production .If there is a larger demand than the production rate, mass production can be sustained. But with a rate of demand lesser than the rate of production, batch production is called for. It gives us an inventory build-up.
Besides this, the economics of the assembly line must be attended to. When annual requirements are comparatively small, it is better to buy from outside. When they are moderate, it is better to produce on individual stations. For a higher demand, an assembly line is justified.
Characteristics of a Mass Production System
1. There is a smooth flow of material (from one Work Station to another Work Station which is straight line, or L-type or U-type, or circular or S-type.
2. There are small WIP (work-in-process) inventories because output of one becomes input of the other process.
3. Production time/unit as a whole is short.
4. Closely spaced Work Stations reduce material handling.
5. No expertise is necessary to operate the system. Less training costs.
6. PPC (production planning and control) is simple.
7. Less storage space for temporary storage and WIP.
1. One machine failure results in a stoppage of the whole line following it. Maintenance is therefore challenging.
2. Assembly lines are not flexible. Great changes in layout are necessary when product design is charged.
3. Production speed is determined by the slowest machine. Line balancing is difficult.
4. It requires general rather than specific supervision.
5. Capital intensive owing to installation of special type of machines and their possible duplication along the line.