Machine design

Machine design is a particular aspect within engineering design, machine design takes care of creating machinery to work safely and reliably well.

Machine: “Device formed of interrelated units, device that modifies a force or a movement.”

Within the operation of a machine it is very important to be clear about the concept of “useful work” since there will almost always be some energy transfer. Other concepts to keep in mind are “strength and movement” because by converting energy from one form to another the machines create movement and generate strength.

Mechanical engineers are related to energy production and processing and to the supply of means of production, transport tools and automation techniques. The foundations of their ability and knowledge are extensive. Disciplinary bases include solids mechanics, fluids, mass and moment transfer, manufacturing processes, and electrical and information theory. Design in mechanical engineering involves all the areas that make up this discipline.

Real problems resist specialization. A simple stump and bearing involve fluid flow, heat transfer, friction, energy transport, material selection, thermal mechanical treatments, statistical descriptions, etc. Construction must respect the environment. Heating, ventilation and air conditioning considerations are sufficiently specialized that some speak of heating, ventilation and air conditioning design as if they were separated and distinct from the design in mechanical engineering.

Similarly, the design of internal combustion engines, turbo-machinery and jet engines are sometimes considered discrete entities. The series of adjectives that follow the word design is only a help in describing the product. Similarly, there are phrases such as machine design, machine element design, machine component design, system design, and hydraulic power design. All of them are slightly more design-focused examples in mechanical engineering. They are based on the same sources of knowledge, organized in a similar way, and require similar skills.

The complexity of the topic requires a sequence in which ideas are presented and reviewed, in this way better proposals appear or details are found that could influence or compromise the results, so that the optimal resolution can be ensured.

Design is an iterative process with many interactive phases, it is never enough there will always be a way to improve the design but it is important to understand when the problem has been resolved to understand when the design is efficient.

There are many resources to support the designer, including many sources of information and a wealth of computer design tools. The design engineer not only needs to develop competence in his field, but also must cultivate a strong sense of responsibility and professional work ethic.

There are functions that must be performed by codes and standards, for the current economy, for safety and for considerations of legal liability of the product. Survival of a mechanical component is often related to stress and endurance. Uncertainty aspects have always been present in engineering design and are approached in a typical way by the design factor and the factor of safety, either in the deterministic (absolute) form or in a statistical sense. The statistical approach refers to design reliability and needs good statistical data.

There are other considerations in mechanical design that include dimensions and tolerances, units, and calculations.

We’ll focus on 4 parts:

Part 1, Basics, begins with explaining some of the differences between design and analysis, and presents various fundamental notions and approaches to design. It continues with three chapters where material properties, stress analysis and stiffness and deflection analysis are reviewed.

Part 2, Fault Prevention, consists of two chapters on the prevention of faults in mechanical parts. Why machines fail and how they can be designed to prevent failure are difficult questions and therefore two chapters are required to answer them; one about preventing failure due to static loads, and the other about preventing fatigue failure caused by cyclic loads that vary over time.

In Part 3, Mechanical Element Design, Part 1 and 2 material applies to the analysis, selection and design of specific mechanical elements, such as shafts, fasteners, welded parts, springs, ball contact bearings, film bearings, gears, belts, chains, and cables.

Part 4, Analysis Tools, provides introductions to two important methods used in mechanical design: finite element analysis and statistical analysis. This is optional study material, but some sections and examples of parts 1, 2, and 3 demonstrate the use of these tools.

Within these 4 main points we can make a breakdown of the design process as follows:

  • 1. Identifying the need
  • 2. Background research
  • 3. Statement of the objective
  • 4. Task specifications
  • 5. Synthesis
  • 6. Analysis
  • 7. Selection
  • 8. Detailed design
  • 9. Prototypes and tests
  • 10. Production
Machine design
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