OVERVIEW OF MECHANICAL DESIGN ENGINEERING

Audio: Overview of mechanical design engineering

If you have been reading my articles, you probably already noticed that I mention mechanical design engineering all the time. I am a mechanical design engineer myself, and I’ve been working in this field for quite some time. Mechanical design engineering is an extremely complex field, and it involves all the disciplines of mechanical engineering.

However, what fascinates me the most is the required depth of technical knowledge, communication, organizational, problem–solving, and decision-making skills wrapped with the creativity to become a sound mechanical design engineer. In this article, I will give you an overview of mechanical design engineering, the typical design problems, and the phases of design.

Introduction to mechanical design engineering

According to the Oxford dictionary, mechanical engineering is “the study of how machines are designed, built and repaired.” If we would expend this, engineering is the activity of applying scientific knowledge to the design. Design is a formulation of a plan to solve a particular problem or need, real or imaginary.

Combining all this together, we can say that mechanical design engineering is a process of applying scientific knowledge and methods to solve a particular problem or need in sufficient detail to permit its realization.

We mean by this that the design process starts when presented with a particular problem or need. We plan on how to solve this problem, we offer the solution, we define the steps on how to build it, and in the end, we have a physical solution to that particular problem or need in front of us. We are concerned with the actual physical artifacts that we can touch and feel.

In essence, mechanical design engineering is concerned with the cost-effective process of sizing and shaping the elements, choosing the suitable materials and manufacturing processes so that the designed machine or device performs in its intended function without failure.

Difference between the mechanical engineering and mechanical design engineering

You might wonder why I am emphasizing the word “design” like mechanical design engineering is not mechanical engineering. Mechanical design engineering is a sub-field of mechanical engineering. All the knowledge contained in a mechanical engineering field is applied in mechanical design engineering.

Mechanical engineering is a fascinatingly large field. There are literally zero industries that mechanical engineering does not have fingers in. Do you think that I am exaggerating?

Painting – equipment for cutting trees, vehicles for transporting raw materials, facilities for processing raw materials and making papers. Then think about the pens, markers, etc.
Beauty industry – I will skip a few steps and go straight to designing beauty products packaging, facilities, and machines for manufacturing these packaging, machines and raw materials for making labels for these packaging, etc.
Programming – I will let you expand on this one; I will just give you a one-word hint: keyboard.

I am challenging you to find one industry where mechanical engineering is not involved.

But why then emphasize the word “design”?

As I said, mechanical engineering is a large field with many sub-fields. Mechanical design engineering is specific in the way that it has a direct impact on the end customer. It is all about keeping your end customer at the center of the whole process.

For example, when a manufacturing engineer receives a request for a manufacturing component, he is not concerned about how this part will impact the end customer. His job is to ensure that the production runs in the requested quantities inside the defined specifications. He is concerned for you as a customer but not about the end-user of the product you are designing. Your job is to have a big picture and know how these components will impact your product that will, in the end, impact your end customer.

Type of mechanical design engineering problems

As a mechanical design engineer, you will encounter different design problems throughout your career. We can divide those into selection, configuration, parametric, original, variant design, and redesign problems. Sometimes you will have only one design problem and sometimes a mix of various types of problems.

Selection design

Today on the market, you can find a wide range of different standardized parts that have already been developed by other companies and usually they are the core competency of those companies. So that means that we should strive toward using these standardized parts because they are already mature and typically cost-effective. Choosing the right standardized component to fit your design specification is called selection design.

To solve the selection design problem, we must define a clear list of specifications (loads, environmental effects, cost restrictions, assembly procedures, etc.). Based on the specification list, we can look into the supplier’s catalog and find the appropriate standardized part.

For example, if we need M3 x 20 screws, we could, based on our specification list, choose ISO 4762 – hexagon socket head cap, M3 x 20 screws. This is a standardized part, and the manufacturing company is already producing millions of those parts. Also, using these standardized screws, we do not worry about assembling them because appropriate tools already exist.

Configuration design

In some cases, we already have all the main components are already designed, and now we must figure out how to assemble them into a complete product. This type of design problem is called a configuration design problem.

When we have a design problem, we also have a problem to solve or a specific need expressed. So, if we already have components designed, we should have the desired function and the requirements defined. The desired function of the solution will be our guide, and the requirements will be ours constraints. We will arrange the components so that all the defined requirements are met in the way that the final solution meets the desired function.

For example, we have two cameras that should be connected to one electronics module. For us, these components are “black boxes,” meaning that we are only interested in their sizes, how they are connected to each other, and if there are any features on them that are predicted for mounting. We are not interested in what is inside of them. So, the desired function is that we have a live video feed in two opposite directions. Our first assembly constraint is that the cameras must be positioned in opposite directions relative to each other. Another assembly constraint comes from a connection between the components and mounting possibilities. We could have different requirements like the position where the device should be mounted (floor, table, ceiling, etc.).

Based on this, we will move forward and try to arrange the components in a way that will fulfill our desired function.

Parametric design

Parametric design is a process of designing product features using a simple equation or a set of equations. These equations govern the design changes, i.e., the value change of one parameter influences the value of another parameter.

For example, let us assume that we are designing a simple swing construction with two swings: one for adults and one for kids. Let us assume that the maximum weight of the adult is 100 kg and the kid 50 kg. If we would implement the set of equations for the stress and the deflection calculations, we could use the same swing design with different parameters (thickness of the sitting board and the cross-section of the rope). So, the parameter “weight” would automatically change the value of the parameter “thickness of the sitting board” and parameter “cross-section of the rope.”

Original design

Each time we develop a process, assembly, or component that previously did not exist, we create an original design. Therefore, each design represents something new and unique. An example of this would be the development of the new iPhone.

Companies with a high success rate in new product development have a high-quality design process implemented. These processes are implemented in a way that the new product development is aligned with the company’s mission, vision, and values together with the business strategies. Each of these processes has a defined set of key activities to introduce the new product to the market and succeed in it.

If you want to learn more about the new product development processes, check New Product Development (NPD) processes.

Variant design

Let us assume that our company is developing 3D printers. Our customer wants that the 3D printer is in a specific color and with LED light. Furthermore, in addition to our logo, they want their logo engraved also. In this case, we would create a variant of our original product to fit the customer’s requirements. Companies can have multiple different variations of their products. The variant design is a customized product designed to satisfy specific customers’ needs.

Redesign

The redesign is a modification of the existing product to meet the new requirements. The redesign could have many subproblems: selection, configuration, and parametric problems. For example, some of the components inside your product are outdated, and you need to update your current design to reflect these changes.

Phases of design in mechanical design engineering

Whatever the design problem we encounter, consciously or subconsciously, we go through the different phases of solving the design problems. These phases of design are:

Recognition of need or a problem

Before we start to provide solutions, we must have a need to address or a problem to solve. This could be a component to redesign, a new component to select, or a new product to develop (in the case of new products, the process is slightly more complex, but it still follows the same logic behind it).

Defining the technical specifications

In order to solve the presented problem or a need, we must understand it completely. This includes understanding the inputs, constraints, and desired outputs of the system. For example, the technical specification could be defined from form, shape, and dimension to test requirements, costs, etc.

Synthesis

Now when we completely understand what is expected of us to solve, we can proceed to combine the ideas into concepts that could offer a potential solution to our problem or a need. This step is frequently called the ideation or invention phase.

Analysis

After we create a potential solution to our problem, we have to apply engineering knowledge in examining the design to get quantitative information about the “status” of our design. This could include performance requirements, manufacturing, cost or any other specified criteria. There will often be a conflict between the requirements. For example, that could be cost, aesthetic appeal, ease of use, stability, etc. All these should be considered, and the best or most acceptable compromise should be derived.

Often after analysis, we will go back to the “synthesis” step, create new concepts, and then move to the “analysis” step and repeat this process until we get to a satisfactory solution.

Testing

In this step, we have a first working design. The first fabricated design is called a prototype. The prototype can be tested in a laboratory on a set of different technical specifications, and by evaluation, we discover whether the design really satisfies them. In case our prototype does not meet the technical specification, we go back to the “analysis” and/or “synthesis” step.

Product evaluation is the final proof of a successful design, and it should satisfy all of the technical specifications.

Presentation

In this step, we finalize the engineering drawings and create BOMs, assembly instructions, or guidelines. Basically, we communicate our design intent to all stakeholders involved in this process.

Closing words on mechanical design engineering

Mechanical design engineering is a complex field that involves all mechanical engineering disciplines. As a mechanical design engineer, you will have many responsibilities that will depend on the size and the structure of the company you are working in. To become a good mechanical design engineer, one must invest a lot of time and hard work in this discipline. To become an expert… I will let you know when I become one.

What I found so fascinating about this discipline is the process of creating physical artifacts. There is a problem or a need expressed by someone, you imagine a solution in your head, put it on the paper, create a CAD model, go back to the paper, update your CAD model, and analyze it again. Then, you make the prototype, test it, go back to paper… and then, after some time and a lot of effort, you have a physical product (device, fixture, jig…) in front of you, that previously only existed in your head. For me, this is more than a rewarding process.

Now you have an excellent overview of what mechanical design engineering is all about. However, I suggest you go through the text once more and identify areas you think need more understanding and clarity. Then, once you have identified those areas, start building up your knowledge in those areas.

To make it easier for you to find related posts, check the “Further reading” chapter below. Do you have any questions or need something to be clarified better? Leave a comment below, and I will give my best to adjust the post accordingly.

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