Designing is a creative and highly iterative process. It is also a decision-making process, and most of the time decisions have to be made with very little information or inaccurate data. Scientists still haven’t figured everything to know about fluid dynamics and yet engineers have designed many planes that are flying today. There will never be enough information, the point of engineering is not to design perfect products (or systems), it is to design products as safe, reliable and efficient as we can be based on the limited information we currently have.
At this stage, you should already know what the functions of the product should be and the target specifications it should meet, detail design, therefore, is about designing the form and size of your product. Products generally have 3 main design components (excluding food, clothes, chemicals): Mechanical Design, Electronics, and Software. It can be either one of those disciplines or a combination of them but with the rise of IoT most products today try to incorporate all three. As an entrepreneur looking to design a product you don’t necessarily have to be an engineer to create a prototype, but you do need to have a basic understanding of the fundamental principles of the disciplines.
The scope of knowledge for each discipline is too wide to be covered in one article, it requires years of studying however the objective of this article is cover the gap of “ I don’t know what I don’t know” to get the entrepreneur to the point of “I know what I don’t know”. We will discuss what you need to know to build your first prototype, where to start learning the skills and who to ask if you need help.
Mechanical design is concerned with the strength of the physical structure of the product; it can be dynamic or static. A bolt is static and gear is a dynamic device because it moves in the product. For both devices we are concerned about their strength; how do we design them in such a way that it will not fail under intended use? A product fails when it doesn’t achieve it’s intended purpose. Imagine sitting on a chair and it falls? That means the chair has failed its’ intended purpose. In mechanical design the failure is usually attributed to structure and material; structure has to do with the arrangement of the components and materials has to do with the strength of the material. It’s possible that the chair is made of steel, which is very strong for a chair, but the chair has two legs, which create a moment when you sit thus falling down. So a good mechanical design uses strong enough materials for the components and they are assembled in such a way that the product will not fail. So to understand the basics of mechanical design, we need to have a good grasp of the strength of materials and how to assemble components such that they don’t fail.
Strength of materials
To understand the strength of materials we first have to understand the concept of stress because it is the primary metric for measuring the strength of materials. When a load (force) is applied to an area of an object the object experiences stress. Stress, therefore, is the intensity of the applied load. The most common load is the force of gravity, if you take a large block of steel and place it on a table, the force experienced by the table is the gravity force of the steel which is given by the mass of the steel block multiplied by gravity constant 9.81 m/s^2. If you take the force and divide by the area where the steel block is placed, they will get the stress experienced by the table. If the table is made out of materials that are stronger than the stress experienced the table will not fail.
However the table is not just one material, it’s made up of different parts made of different materials. In order for the table not to fail, the entire assembly must be able to withstand the applied load. To determine if the table will be able to stand the load is more complicated than it seems, it depends on how the table is shaped, where the load is applied, the strength of the joints, and the materials of all the components. Below is a chart of different materials and their uses, then there is a chart comparing different materials and their strength, and lastly, there is a chart of materials and their costs. This helps in understanding which material is stronger than which, to get more information on strength of materials visits this page.
To learn more about the mechanical design you can read this textbook.
The electronic design has to do with the design of electrical circuits using active and passive components such as diodes, transistors, batteries, resistors to build devices for processing information, signal processing, communication, and controlling systems. To start building circuits in electronics you will need a basic understanding of the physics of electricity and mathematics. It used to be very difficult to get started with electronics, however, today there are many electronics kits available that can teach you everything you need to know about electronics such as the Arduino kit, Raspberry Pi.
Electricity is energy and the flow of charge. The flow of charge is called current and is measured in amperes with symbol A. There are two types of electrical signals, that is AC for alternating current and DC for direct current. For DC current, electricity flows in one direction from Power to Ground so, in other words, we need power or energy for charges to flow or to have current. We get power or energy from many sources usually from batteries, especially for DC current. When the energy is stored in the battery we call it volts. Therefore, volts are a measure of how much energy is in our power source or battery it has a symbol capital V.
Now that we know what electricity is, we need a way to control it to perform specific tasks like tv, computer, washing machine, lights, etc. We do this by designing something called a circuit. A circuit is simply a connection of electronic components that allow current to flow in a closed path and they are connected using conductors. Conductors are materials that allow current to flow past them for example wires. All electrical components have a quantity called resistance, some more than others and others it’s insignificant. Resistance is there to reduce the flowing current, we use resistors to limit current because not all electrical components use the same current. Once again in order to have current, we need a power source, so a circuit cannot work without a power source.
Embedded electronic systems
Often times electronic devices require some advanced control, to do that we have to instruct the circuit what to do given certain condition. If you are building a product that requires you to switch a light on, you will only need a switch, a wire, a light, and a power source. The only control you will need is just to switch on/off the switch. If however, you need the light to switch when it senses the environment is dark, and it must adjust the brightness it produces then you might need more than a switch to do that. Fortunately, for most electronic applications there are circuits that have already been built that can be bought of the shelf and can be integrated into your product, these circuits are called integrated circuits and microcontrollers. You can embed small circuits into your product to achieve some specific tasks such as increasing the speed of a motor or control the brightness of a light source. If you want more control, you can use micro-controllers to design advanced electronic embedded systems that can be programmed.
Micro-controllers are microcomputers in the form of Integrated Circuits (IC’s) chips used in embedded systems. They usually consist of memory, processing, and peripheral units and are responsible for controlling electro-mechanical systems. These small computers are so powerful and convenient to use in many applications like consumer goods, robotic systems, medical devices, automobiles, mechanical machines and other products that need electronic control.
Micro-controllers need to be programmed before they can be used, they are programmed using various computer languages (C/C++, assembler) then the code is compiled (using compilers) and sent to the micro-controller in machine code (binary). The information programmed is usually called ‘instructions’ as it tells the microcontroller what to do. The micro-controller then saves the instructions and when it is powered it performs all the tasks automatically. Below is an image of the basic features found commonly in micro-controllers.
In the past, a challenge with micro-controllers was that often they were difficult to program and required specialized engineering skills to design them for embedded systems, as a result, they were often designed by manufacturers already embedded. Over the past few years, micro-controllers and embedded systems technology have evolved, micro-controllers chips are now sold separately and can be programmed with relative ease by engineers with the introduction of new higher programming languages like Python.
Embed systems have become so accessible that even without engineering knowledge you might be able to prototype electronic products using micro-controllers through development platforms like Arduino, Raspberry Pi, and PIC micro-controllers. Development platforms have made it easy to work with micro-controllers especially for educational purposes and prototyping of electronic products. To learn more about getting started in electronics read this article.
Drafting and CAD modeling
Once you have an idea of a product it is not enough to write out what it must do, you must create a CAD model of what it should look like. The model communicates how the final product should look, how many parts it consists of, and how should the product be assembled or manufactured. Without the CAD model, it would be impossible for manufacturers to know how the product should be fabricated or how to assemble the product. Creating a model also helps all stakeholders such as potential investors and design team better understand your product. Read about different CAD software here.
CAD software available
Usually, before draughting and modeling you start by creating sketches of the product, these do not necessarily have to be of high quality, they should just capture the form of your product and the dimensions. After you have done the sketches, you can then start modeling on a CAD (Computer Aided Design) software. Modeling transforms your sketches into a digital 3D model and also helps you understand better how each component of the product fits.
Where to learn CAD modeling?
Learn online for free
On-site training (South Africa)
On-site training usually takes 3 full days and in South Africa, it cost around (R4 500.00) for a basic course.
After modeling your product, you will then proceed to make 2D part and assembly drawings that can be sent for manufacturing. The part and assembly drawings are usually drawn from the same CAD software however not all CAD software support 2D drawing capabilities. The part drawings should contain all the necessary information required to create the part, such as; material to be used, fabrication process, total square length of the part, the thickness of the part, bill of materials, and joining processes to be used. Fabrication refers to processes such as drilling, machining, bending, cutting, and chamfering. Once you have the drawings of your product you can then send it to manufactures or fabricators.
- 2D Part and Assembly drawings
- A CAD model of parts and assembly
- Bill of Materials-this indicates the materials to be used is assembly and the number of parts required
- Packaging instructions-this gives the manufacture instructions on how they should package your part once it has been built, it should also indicate how it should be transported
If you would like to hire someone to do design your product and engineering services have a look at these companies below.
Industrial design and electronic design firms in South Africa
If you have already made your design and need someone to fabricate or construct it.
Fabricators in Joburg
However when building your first prototype this might be a very long way to go about it, with the rising popularity of 3D printers, it is possible now to go from your 3D CAD model to a physical form in less than an hour. This means you don’t have to invest time and effort to prepare your model to be sent for fabrication and wait for them to finish. This is why 3D printing is very useful for rapid prototyping for small products just to get the shape of the final product. However 3D printing is limited on the materials you can use, quality and the size you can print in. Below are some useful resources if you are interested in learning about CAD modeling, draughting, and 3D printing. You don’t need a 3D printer in order to create a prototype, the point for creating is to verify if your product will work before investing a lot money in a production version. The prototype should be small, inexpensive and should be quick to build. To learn more about prototyping read this article.
3D printing services in South Africa