**2. Production processes**

As shown in **Figure 1**, production engineering is broadly covering production processes and production systems, and each of these includes various operations. Production processes alter the shape, geometry, and properties of the workpiece enabling it to perform its function. Processing operations may include the enhancement of properties of the workpiece by means of heat treatment operations and improving the quality of the workpiece surfaces using surface processing operations. There is a variety of manufacturing operations including conventional and nonconventional methods. Generally, conventional manufacturing processes are preferred as these are often more economical and the equipment needed is readily available. However, in some cases, the use of nonconventional manufacturing processes is inevitable despite imposing higher costs. For example, **Figure 2** shows a flat metal part with a complex external shape and many internal cut geometries. This part is cut from an 8 mm thickness AISI 304 L stainless steel plate. It is a relatively thick plate of hard-to-machine stainless steel material, making its production problematic using conventional methods. The use of a nonconventional method such as Abrasive Water Jet Machining (AWJM) makes this a relatively easy operation. This part is taken from a research work studying the optimization of AWJM process parameters for improving

### **Figure 1.**

*Classification of activities in production engineering.*

### **Figure 2.**

*Map of Australia with embedded geometrical shapes cut from an 8 mm thickness AISI 304 L stainless steel plate using abrasive water jet machining (AWJM). (a) Side view. (b) Top view.*

productivity [24]. Another example is shown in **Figure 3** where a complex lattice structure is formed by connecting multiple curved surfaces with thin wall thicknesses. The material of this part is 316 stainless steel which is hard to machine, and

its complex geometry and small wall thickness make its production impossible with conventional methods. It is produced by additive manufacturing (AM) also known as 3D printing from a powder-like material. This part is printed layer by layer using a layer thickness of 25 micrometers where powder-like metal particles are melted using a powerful laser beam in a process known as selective laser melting (SLM). The process is costly, and the rate of production is low; however, making it possible to produce some complex geometries that would have not been impossible otherwise.

Cutlery items such as spoons and forks are examples of single-part products where no joining or assembly operations are needed after the single-part product is manufactured. However, most products consist of more than one part and there is a need for joining or assembling of these parts. The number of parts in a product where assembly or joining processes are needed can go from two to millions. A screwdriver has 2, a typical car has about 20,000, and the largest passenger aircraft has over 4 million parts that are individually manufactured and assembled to form a complex product with many assemblies and subassemblies. Many types of joining, and assembly operations are used in production plants. Some are permanent joining methods such as welding, brazing, soldering, riveting, and adhesives; and some provide the possibility of disassembly where mechanical fasters such as bolts and nuts or screws are used.

Quality control is often considered the last step of the production cycle although modern manufacturing strategies state that quality must be built into the product and must be incorporated during manufacturing and assembly operations. In either case, the quality of the product must be tested and verified before it leaves the production plant.
