Reverse engineering (or back engineering) is a method used to understand an item and its interaction with various components. This can be quite helpful when you want to create your own version or copy of a common product with a 3D printer.
We are going to look at some things to consider when reverse engineering. Our primary focus of this article will be an automotive brake caliper and the processes we used to reverse engineer it into a 3D printable model for educational purposes.
1) Get Your Tools Ready
There are a lot of tools that can be helpful when reverse engineering. Tools can range from Vernier calipers (aka. Digital Dial Calipers), rulers & 3D scanners to alternative measurement tools such as micrometers for inner & outer measurements. Another simple tool would be a pencil and notepad. You may want to keep notes on where the parts go, or to note some specific areas that you may want to look at later.
In our initial design plans for reverse engineering the brake caliper, exact dimensions were not necessary and so we selected a pair of Vernier calipers as our tool of choice for this project. A good CAD program is also going to be very helpful. An excellent list of the top free CAD programs can be found on the Pinshape blog here.
A pair of calipers can start around $10+, but they should be a standard tool for all makers. Not only do they work well to measure your prints for reverse engineering, but they also serve to measure your filament to test for accurate and consistent prints.
2) Plan For Your Design & Print
It’s time to start planning out your design for 3D printing. Here are some key points to keep in mind:
- What features of the product do you want to carry over to your design & print?
- Some products have complex shapes, is this something you can orientate & print properly? You may need to make a slight design change to allow for a better print.
- What areas will you need to create a tolerance in your design that’s acceptable to your printer?
- When working with a metal part, tolerances are going to be significantly smaller than what you can achieve with a desktop 3D printer. You will need to keep this in mind and adjust your design accordingly. Another community member, MakerClub goes into detail on tolerances in his article on Snap Fit Parts.
- Will you design your model to scale? If you need to scale your design up or down, check out this excellent scale calculator.
- Because the brake caliper is small enough to print, we were able to keep a 1:1 build scale.
Once you have your design planned out, it’s a good time to start taking measurements & notes. For the brake caliper we reverse engineered, we needed to start measuring seals, pistons and the bodies themselves. While taking notes during this step is important for consistency between your parts as some parts are quite complex and it may be tough to properly document your measurements. In this case, working in your CAD program while taking measurements may be a superior alternative.
3) Disassemble and Study – Understanding
The most important starting point of reverse engineering is understanding the product you have in your hands. Since there is a number of interworking parts, you will want to check the interrelationships between the various parts. When disassembling the caliper, be sure to keep an eye on fit and feel of the parts. Tolerances will be a big factor in the print and design process. We will talk about that a little later in the article. Ensure that you have taken the time to fully understand the original Caliper, so you can cut down on any errors that may arise later in the design and printing process.
Having a strong understanding at the start will make the planning and design of your product much easier. As you can see, I started with a caliper that was already taken completely apart.
In most cases the product you have will probably be pre-assembled. Your first step will be to start the disassembly process. Inspect each part and if there are moveable parts, move them until you have an understanding of how it works. In the above photo, the brake caliper has been disassembled and a note was made to where each part goes and how they work with each other. As you can see there are quite a few points of interest with the brake caliper that will need to be carried over to the computer design.
4) Start Your CAD Work
Our choice for designing the brake caliper was to start out with a simple sketch. We designed the features of each brake caliper body within the initial 2D sketch. We were also able to cut the workload in half by only designing 1 half of each caliper body and mirroring the 2nd side. This is important if your design is exactly the same on each side. Mirroring the 2nd side is going to save you a lot of time and will ensure that everything lines up perfectly.
The next step was to create offset planes at each key feature of the Caliper body. The original design sketches were then projected to their respective planes to create the thickness required.
Once completed, all the other necessary design features that could not be done from the initial sketch can be added. For the brake caliper this would include the brake bleeder fittings and all the other parts to the caliper. After you begin 3D printing, you will start to see your 2D design transform into 3D. This is where you can see if there are any problems with the design.
Here’s a good example of how to project to surface on Fusion 360:
Starting at the 6 minute mark
5) Choose Your Filament
Often when you replicate an item with a 3D printer, you are not going to be able to print it in the same material as the original object. Another decision to keep in mind when designing your model is which filament you’re going to use. Of course, this depends on what you will use your model for. Will it be a display unit where nearly any filament will do or is your model going to be used daily and under various forces? This may require you to use a more robust filament that can withstand the wear and tear.
We designed this Brake Caliper model as an display piece that can be taken apart and re-assembled. We chose to print it with PLA and ABS. Parts that require a little flex were done with ABS. The rigid parts that won’t need flex were done in PLA.
Here is a comparison of 4 popular filaments that can help you choose the right material for your project.
When reverse engineering an item for 3D printing, it’s important to have the appropriate tools along with a good CAD program and proper planning. One thing to always consider is the interaction between various parts as it will effect the final outcome of your 3D printed model. Orientation and filament selection are also important factors for the end product. With proper planning, you will be able to satisfy your curiosity and begin to take your ideas even further!
You guys asked for more, so Chris answered a bunch of your questions to help you on your journey to reverse engineering!
1. How do you take the measurements of the curved parts of the product with the calipers?
About the Authors
Brad & Chris Halliday
Born and raised on Vancouver Island, British Columbia, and yes, it really does rain alot!!!! Chris(left) got into 3D printing after the RepRap machines blew up the internet and the technology became accessible for hobbyists. Brad (right) quickly followed after getting his hands on a printer. Their natural curiosity got the best of them and they expanded into CAD design to start creating their own models. When Chris isn’t out rummaging through the woods playing photographer and historian, he can be found in front of Autodesk Fusion 360 designing the next print to come off of one of his Lulzbot 3D printers. Brad decided to make the trek out to Red Deer, Alberta 2 years ago and realized the potential of 3D printing. Having such common interests, they joined force. With their ideas and 3D printing tech, H2 Fabrications was created.