Chapter 3 ENGINEERING CONCEPTS IN INDUSTRIAL PRODUCT
3.1. Engineering and Industrial Product Design
3.1.3. Comparison of Industrial Product Design with Engineering
Engineering is one of these disciplines that industrial product design is tightly related.
Industrial product design benefits from engineering knowledge in constituting the design knowledge as being a field of the design discipline.
The intersecting criteria of engineering and industrial design in a product are:
• Functional Criteria o Physiological Criteria o Environmental Criteria
• Technological Criteria o Material Criteria o Production Criteria
• Economical Criteria
o At the Producers’ Level o At Macro-Level
Engineering fields such as human-factors engineering, materials engineering, mechanical engineering, industrial engineering, process engineering, manufacturing engineering, design engineering, product design engineering deal with the criteria given above (as it was mentioned in the previous chapter), and participate in design of the industrial product.
The comparison of industrial product design with some of the engineering professions, through seven measures, is shown in Figure 3.4, and the comparison with mechanical design engineering is briefly described as follows (Ullman 1992: 32):
Figure 3.4 Comparison of industrial product design with engineering professions (Ullman 1992: 32)
• Type of Objects:
Mechanical Design: Many types of components and assemblies vary widely in shape, composition, functional complexity and technologies - fluid dynamics, thermodynamics, and kinematics.
Industrial Design: Primary objects are those that affect the aesthetics or human factors of the product.
• Type of Problem:
Mechanical Design: All types discussed before Industrial Design: All types discussed before
• Form–Function Relation:
Mechanical Design: A component or assembly plays a role in many functions.
Industrial Design: Little or no functionality, form dominates function.
• Decomposition Potential:
Mechanical Design: Form-function relationship determines the potential to decompose a problem into sub problems. It is limited though, as form and function is overlapped in devices.
Industrial Design: Decomposition is in form, not in function.
• Language Complexity:
Mechanical Design: Semantic, analytical, graphical, physical.
Industrial Design: Usually graphical.
• Graphic Complexity:
Mechanical Design and Industrial Design: 3D, 2D, shaded images greatly complicate the process.
• Design Methods:
Mechanical Design: Partially developed.
Industrial Design: Many different philosophies.
3.1.3.1. Decomposition
A system is generally considered a conglomeration of objects that perform a specific function. The car is a transportation system; its function is to move goods and people.
The engine is the power subsystem; its purpose is to convert potential energy started in the fuel into kinetic energy. In the engine, the ignition is one of many subsystems. Thus, this is the decomposition of car into three system levels, while still referring to the function of objects.
Another view, the engine is an assembly of components in terms of the physical components or form of the engine. Engine assembly can be decomposed into subassemblies such as the carburetor and it can be further decomposed into smaller assemblies and, finally, into individual components. “System” and “assembly” used where the object of interest falls in the decomposition as it goes on sub…of sub… and
“sub” is used to show one level of decomposition in a specific discussion.
In Figure 3.5, the decomposition of design fields (software, mechanical and electrical) is shown, where the function of system and its decomposition are considered first, and then the subs… and the components.
Figure 3.5 Decomposition of design fields (Ullman 1992: 19)
“For example, the ignition system and the controller on carburetor are electrical. These systems provide energy transfer and control functions in the engine. Some of the control functions are filled by microprocessors. Physically, these are electric circuits, but the actual control function is provided by a software program in the processor (Ullman 1992: 19)”. It is often unclear whether the actual function should be met by mechanical assemblies, electrical circuits, software programs or a mix of these elements.
3.1.3.2. Form-Function Relation
Function= Operation= Purpose: to describe what the device does
Form: any aspect of physical shape, geometry construction, material or size.
Performance: measure of function - how well the device does what it is designed to do.
Earlier, mechanical systems are decomposed into assemblies and components physically. Functional decomposition is often much more difficult than physical decomposition, as each function may use part of many components and each component may serve many function. “For example, the handlebars of a bicycle. They are a single component that serves many functions. They allow for steering (a verb that tells what the device does), and they support upper-body weight (again, a function telling what the handlebars do). Further, they not only support the brake levers but also transform (another function) the gripping force to a pull on the brake cable. The shape of the
handlebars and their relation with other components determine how they provide all these different functions. The handlebars, however, are not the only component needed the steer the bike. Additional components necessary to perform this function are the front fork, the bearings between the fork and frame, the front wheel, and miscellaneous fasteners. Actually, it can be argued that all the components on a bike contribute to steering, since a bike without a seat or rear wheel would be hard to steer. In any case, the handlebars perform many different functions, but in fulfilling these functions, the handlebars are only a part of various assemblie (Ullman 1992: 20)”. This coupling between form and function makes mechanical devices hard to design. Performance, as measure of function, clarifies how well the steering is fulfilled with handlebars.
Figure 3.6 shows and example of physical decomposition in a safety bicycle.
Figure 3.6 Exploded safety bicycle, 1900 (Perry 1995: 44) 3.1.3.3. Languages of Design
There are four types of design languages, which are as follows (Ullman 1992: 28):
• Semantic: The verbal or textural representation of the object – for example, the word “bolt,” or the sentence “The shear stress is equal to the shear force on the bolt divided by the stress area.”
• Graphical: The drawing of the object- for example, scale representations such as orthogonal drawings, sketches, or artistic renderings.
• Analytical: The equations, rules, or procedures representing the form or function of the object –for example, τ=F/A
• Physical: The hardware or a physical model of the object.
The initial need is expressed in a semantic language as a written specification or a verbal request by a customer or supervisor. The final result of the design process is a physical product. Although the designer produces a graphical representation of the product, not the hardware itself, all the languages are used as the product is refined from its initial, abstract semantic representation to its final physical form.
The process of making an object less abstract (or more concrete) is called “refinement”.
Especially, mechanical design is a continuous process of refining the given needs to the final hardware. Figures 3.7 and 3.8 reveal the refinement of the abstract representations as follows:
Figure 3.7 Levels of abstraction in different languages (Ullman 1992: 31)