Good product design is far from easy. But by following 7 mechanical engineering design tips, you can simplify the process.
To point out, I’m not a mechanical engineer by degree. Formally, I’m an electrical engineer if it even matters. I’ve just gotten my hands dirty in a lot of mechanical-type work. Also, I’ve worked with many uber-talented mechanical engineers. So, I have a good amount of valuable hard-earned lessons to share.
Hopefully, you find my 7 tips useful. Because every small improvement will make you a better designer. In return, you can level up faster and work on more awesome projects.
#1 Considerations of bringing designs to life in the real world
On paper or CAD, EVERYTHING looks perfect. But when you want to bring a design to life, it’s a different story. Almost every mistake rises to the surface.
Say you’re designing a widget made of a bunch of electronic components. If you forget a component, you’ll quickly realize something is wrong. Because the widget simply won’t work.
The point is, there aren’t any shortcuts to good design. A designer needs to always think about how their work will translate over to the real world. When I design on paper, I always put myself in a contractor’s or manufacturer’s shoes. So, pay close attention to the following in your design work:
- Real-world practicality
- Math errors
- Safety factors
- Real-world variables
- Accuracy of collected information
- Challenges of construction and manufacturing execution
The following can happen with poor designs:
- Single sub-component failures cascade through a design. The entire design then fails.
- Costly change orders lead to a project going over budget.
- Large project delays, lead to an increase in financing costs.
- A mistake goes undiscovered and later leads to injuries and/or deaths.
I’ve seen single rushed assumptions derail entire projects. The assumptions seem innocent enough, but they later violently ripple through the projects.
For example, I’ve seen a pipe incorrectly sized and installed under a body of water. The pipe was 50-feet below grade and spanned a little over a mile. This mistake then immediately froze the project and caused a couple of years of mayhem. If this wasn’t enough, a couple of engineers lost their jobs. Not fun!
#2 Occam’s razor
If two answers are equally likely to be true, the answer making fewer assumptions is probably true. This is Occam’s razor in a nutshell.
In other words, simple answers are always best. So in your designs, keep your work as simple as possible. Then, add greater details and complexity, only when necessary.
To pull this off, first, define your problem in its most simple terms. Then, find the most simple theory or framework fitting your problem, and use it. Your choice will set the foundation for how simple or complex your design will become. I suggest focusing on simplicity in the following design areas:
- Design approach
- Design concept
- Selection of design components
For example, with the SpaceX Raptor engine, Elon Musk didn’t reinvent the wheel. He iterated over past full-flow staged combustion engines. He wanted to makes these engines better and simpler. Because the simpler engines are, the more reusable rockets become. And on Mars, you want to do as little rocket refurbishment as possible.
Important Note: the goal of good design is to minimize the number of components. This may in return lead to using several highly complex components. But in return, the number of manufacturing processes reduces.
It’s a fine balance between component complexity and the number of manufacturing processes.
#3 Focus on simplicity
Why am I jumping back into more “simplicity” talk? Because the common theme with any good design is simplicity. And sure, a design needs to function. This is a given. But still, we ALL want more and more simplicity in engineering.
Now, the big question is, what does simplicity even look like? In short, the easier it is to understand a design, the simpler it probably is. Duh, right?!
For example, a given widget may need 10 distinct parts to operate. So, to fully understand the design, you need to know how all the 10 parts work together. Now, imagine if there were only three parts…
To point out, it takes A LOT of creativity and knowledge to reduce the part count. It’s no cakewalk. But this is what makes good designs difficult.
What’s more, many complexities remain hidden within a space unseen to the end-user. To better explain, think of a simple piece of PVC conduit you’d find in your local Home Depot. This conduit is inherently complex both scientifically and in manufacturing. BUT, the conduit is field-proven to work per a set of parameters. In other words, if you use the conduit per its specs, it won’t let you down.
In short, the PVC conduit’s complexity is invisible to a design engineer. The designer simply calls out a 3-inch conduit on a site plan without much-added thought. This is why it’s important to understand the source of the complexities in your design. Not all complexities are inherently bad.
Now, check out this edge case. What if the designer adds a bunch of unnecessary conduit bends and pulls boxes to the design? The design will THEN undoubtedly become complex. The construction and maintenance effort will shoot up considerably.
Important Note: four techniques work well in all industries to create simple designs. These techniques are the following:
- Add symmetry to designs
- Purchase third party parts versus making components from scratch
- Specify parts using industry standards
- Use proven dependable designs as templates to iterate off from
#4 Understand the laws of nature
It seems like with every passing year, we’re diving deeper into the digital world. But, we can’t forget we still live in the physical world.
So not surprisingly, most design engineers need to understand the physical world. For example, you can’t design a bridge, if you don’t understand how wind affects your design. And this is where making small-scale physical models of your design comes into play. You can test against the laws of nature before you go too deep down a design direction.
But more often, engineers create models using simulation software. The software has all the mathematical models of what we understand from the laws of nature baked in. Without this analysis, design failures would be MUCH more common.
Now, what are the laws of nature we’ve defined and use? Some of the most common you’re probably familiar with are the following:
- Newton’s laws
- Maxwell relations
- Boltzmann equation
- Bernoulli’s principle
- Hooke’s law
- Lenz’s law
- Ohm’s law
Important Note: a designer needs to understand our laws of nature. Otherwise, you’ll never spot the “gotcha” moments in your design. This includes incorrect outputs from software simulations.
The ability to catch such mistakes is where theory and real-world experience intersect. And if you ever want to become a 10x engineer, you need both to succeed.
#5 Abbe’s principle
Abbe’s principle states,
“Maximum accuracy is obtained when the scale and the measurement axes are common.”
What does this mean? Abbe’s principle comes down to the following three simple rules:
#1 For best results, make a linear measurement inline or sideways of a process. In other words, try to make your measurement as close to your process as possible. For example, measure a pot of water by placing your measuring device in the pot. Don’t place the measuring device 1-foot away from the pot.
#2 If a linear measurement isn’t possible, make a measurement at a distance parallel to your measured line.
#3 If parallelism between a part and measurement isn’t possible, you’ll have an error. The error will be a function of the angle the measurement makes with your part. But also, the error will increase the farther you move your part from your scale. This is Abbe’s error.
So in your design, place your parts as close to your process as possible. The farther the parts are from the measured process, the greater measurement errors you’ll create. This applies to the measured temperature, pressure, voltage, current, flow, and so on.
A great example of not maintaining parallelism is with spinning tops. If you bend the axis a bit, the top will slightly wobble as it spins. Then bend the axis even more, and the wobble increases. This is Abbe’s error and is also called the sine or cosine error.
Important Note: build manufacturing machines as accurately as possible. For example, in an assembly line, the guideways and beds should be as uniform as possible. This includes maintaining machine temperature throughout. Otherwise, measurements will be off affecting tolerances.
#6 Maintain independent functions
Keep the functions of your design independent from one another the best you can. In other words, break a design down into separate simple functions. For example, with an airplane, you’d break the plane design into the following parts:
- Power plant
- Landing gear
Then, we can further drill into each of these 5 parts. For instance, with the power plant, we can break it down into the following parts:
- Electrical infrastructure
- Control and instrumentation
- Fuel system
I know, it sounds easier said than done. The challenge is with how interdependent all these parts are together. For example, the engine and all electronics rely on the fuel system.
But in the beginning, design phase, you can better separate out each part. You can focus on designing the best fuel system rather than the entire plane. This is a bit less intimidating. And frankly, it’s the logical approach when each part requires a specialty skill.
#7 Identify sensitive directions and reference features
With every design, there’s a direction where accuracy and repeatability are most critical.
For example, think of a SpaceX rocket landing on a floating drone ship. The rocket needs the utmost accuracy as it descends for landing. This means the constant collection of a full spectrum of data in the entire descent. So the critical direction, or component, would be the sensors mounted on the rocket.
If there’s a hiccup in data collection in the descent, the rocket may not have time to adjust. As a result, its path may fall off course and it’ll splash into the ocean.
This is why you always need to identify the sensitive directions in your machines. Then, put in extra engineering effort into the accuracy for directions you deeply rely on. Also, make sure you maintain precision where you need it the most.
What’s more, identify key features remaining fixed in your design. These are key features you can’t remove no matter what. You need to always design around these key features.
Mechanical engineering design tips wrap up
A LOT of effort goes into design work, but even more effort goes into great design work. Because all great designs look simple on the surface. But as with everything, the devil is in the details.
So use these mechanical engineering design tips to improve your work. You’ll then be able to create more functional and cost-effective designs. This is what separates great engineers from average engineers.
What mechanical engineering design tips do you find the most helpful? What do you find the most difficult about design work?
SUBSCRIBE TO ENGINEER CALCS NEWSLETTER
Koosha started Engineer Calcs in 2020 to help people better understand the engineering and construction industry, and to discuss various science and engineering-related topics to make people think. He has been working in the engineering and tech industry in California for over 15 years now and is a licensed professional electrical engineer, and also has various entrepreneurial pursuits.
Koosha has an extensive background in the design and specification of electrical systems with areas of expertise including power generation, transmission, distribution, instrumentation and controls, and water distribution and pumping as well as alternative energy (wind, solar, geothermal, and storage).
Koosha is most interested in engineering innovations, the cosmos, our history and future, sports, and fitness.