There are certain basic functions that must be carried out to convert raw materials into finished product. For a firm engaged in making discrete products, the functions are:1. Processing 2. Assembly 3. Material handling and storage 4. Inspection and test 5. Control
The first four of these functions are the physical activities mentioned in unit 1 that touch the product as it is being made. processing and assembly are operations that add value to the product.
the third and fourth functions must be performed in a manufacturing plant. but they do not add value to the product. As shown in fig. 2.1, these four functions occur inside the factory directly on the product. the fifth function, control is required to coordinate and regulate the physical activities. The following subsections describe the five functions.
Processing operations transform the product from one state of completion into a more advanced state of completion. No materials or components are assembled or added to accomplish the transformation. Instead, energy (i.e., mechanical, heat, electrical, chemical, etc.)is added to change the shape of the part remove material from it, alter its physical properties, or accomplish other forms of work to change it. Processing operations can be classified into one of the following four categories:
1. Basic processes
2. Secondary processes
3. Operation to enhance physical properties
4. Finishing operations
Basic processes are those, which give the work material its initial form. Metal casting and plastic molding are examples. In both cases, the raw materials are converted into the basic geometry of the desired product. It is common for additional processing to be required to achieve the final shape and size of the workpart.
Secondary processes follow the basic process and are performed to give the workpart its final desired geometry. Examples in this category include machining (turning, drilling, milling, etc.) and press-working operations (blanking, forming, drawing, etc.).
Operations to enhance physical properties do not perceptibly change the physical geometry of the workpart. Instead, the physical properties of the material are improved in some way. Heat-treating operations to strengthen metal parts and preshrinking used in the garment industry are examples in this category.
Finishing operations are the final processes performed on the workpart. Their purpose is for example, to improve the appearance, or to provide a protective coating on the part. Examples in this fourth category include polishing, painting, and chrome plating.
Figure 2.2 presents an input/output model of a typical processing operation in manufacturing. Most manufacturing processes require five inputs:
1. Raw materials
2. Equipment ( machine tools)
3. Tooling and fixtures
4. Energy (electrical energy)
The manufacturing process adds value to the raw materials (or work-in-progress) by transforming them into a more desirable state. The process is usually carried out on production equipment that reflects a capital investment by the firm. The equipment is adapted to the particular workpart by the use for tools, fixtures, molds, die sets and so on. This tooling must often be designed specifically for the given workpart. Electrical energy is required to operate the production equipment. Finally, labor is required to operate the equipment, load the raw workpart, unload the piece when the process is completed, check for malfunction of the machine, and so on.
The manufacturing process products two outputs:
1. The completed work-piece
2. Scrap and waste
The term completed workpiece refers to the desired output of the particular manufacturing process. Since the workpart must be routed through several operations, only the last operation yields the finished part. The other operations produce work-in-progress for succeeding processes. As a by-product of all manufacturing processes, some scrap material and waste results. The scrap is in the form of metal chips (machining operations), skeleton (sheet metal press-working operations), sprue and runner (plastic molding), and so on. The waste is represented by tools consumed in the operation, the mechanical inefficiency of the machine tool, and heat losses.
Assembly and joining processes constitute the second major type of manufacturing operation. In assembly, the distinguishing feature is that two or more separate components are joined together. Include in this category are mechanical fastening operations, which make use of screws, nuts, rivets, and so on, and joining processes, such as welding, brazing, and soldering. In the fabrication of a product, the assembly operations follow the processing operations.
Material handling ans storage
A means of moving and storing materials between the processing and assembly operations must be provided. In most manufacturing plants, materials spend more item being moved and stored than being processed. In some cases, the majority of the labor cost in the factory is consumed in handling, moving, and storing materials. It is important that this function be carried out as efficiency as possible. In modern industries automated materials handling and storage functions are already being used.
Inspection and testing
inspection and testing are generally considered part of quality control. The purpose of inspection is to determine whether the manufactured product meets the established design standards and specifications. For example, inspection examines whether the actual dimensions of a mechanical part are withing the tolerances indicated on the engineering drawing for the part.
Testing is generally concerned with the functional specifications of the final product rather than the individual parts that go into the product. For example, final testing of the product ensues that it functions and operates in the manner specified by the product designer.
The control function in manufacturing includes both the regulation of individual processing and assembly operations, and the management of plant-level activities. Control at eh process level involves the achievement of certain performance objectives by proper manipulation of the inputs to the process.
Control at eh plant level includes effective use of labor, maintenance of the equipment, moving materials int eh factory, shipping products of good quality on schedule, and keeping plant operating costs at the minimum level possible. The manufacturing control function at the plant level represents the major point of intersection between the physical operations in the factory and the information-processing activities that occur production. Let us examine the complete cycle of information processing that takes place in a manufacturing firm.