1. Start with a DYI first
If you are looking to build your own 3D printer, or you already own a cheap version and you want to improve on what you already have there are many resources available these days. However, if you are new to 3D printing I highly recommend starting with one of available sub CAD$400 kits that you have to assemble yourself instead of trying to build one from scratch. These kits are generally based on Prusa i3 and are perfect for beginners. They may not be perfect 3D printers, which is actually beneficial if you are trying to learn the basics of 3D printing and how the printers work.
Don’t start from scratch, build on other’s accomplishments. Learn from other’s experience and mistakes while questioning everything.
After using the DYI Kits you will at some point you hit the limits. There is only so many ways you can change a kit printer, and there are physical limits of how accurate, how fast, and how big these printers can print. By then you should have enough knowledge and experience to know what your needs and wants are in a 3D printer. Additionally having a working 3D printer helps to build parts for your next improved 3D printer.
2. Design and build using what you can get
There are many open-source resources and designs available that you can use for free. I have shared some of my own designs freely on the internet (via Thingiverse.com). Therefore information availability is not an issue at all.
If you live in Canada (like I do) The biggest challenge in building a 3D printer (or any machinery) from scratch is getting the hardware required for the build. There is limited availability of basic hardware such as aluminum extrudes, screws and bolts, joints, belts, bearings etc. It seems there is not much demand on such things and that lowers the availability and drives the prices up. At the time I was trying to purchase the raw material needed (back in 2016) the cost of 2020 aluminum extrude was USD$35 per meter and that was before shipping and taxes. Additionally I found it very difficult to source basic hardware such as bolts and nuts and fasteners. In fact at the time it was far less expensive to bulk order the 2020 extrudes, bolts and nuts, and all fasteners, bearings, and many other needed material from Alibaba.com to be shipped from China. Unless you have access to industrial supplies and some contacts then you should consider what material and supplies you can get your hands on before starting to design your machine.
3. Try, Fail, adjust
Once you source all your material, then the actual fun of building prototypes and trying out your design begins. If you are planning to do this, you must have a lot of patience. It does not have to cost a lot of money (although there is no limit on how much you can spend), but it costs a lot of patience and time. You have to study and learn, go online and spend countless hours learn from other people’s experience. You will learn some things the hard way and it will be frustrating at times. You will fail, but you will also learn. You have to be able to come up with innovative ways to solve problems, because not all the answers are out there yet. Eventually you will succeed and when you do it is extremely rewarding.
Improvements come gradually, and design and engineering is about managing compromise. You can never design or build something perfect on the first try, although knowledge and wisdom can help to avoid many traps and pitfalls. Start small and simple and try to keep complexity to minimum. I personally like to favour simplicity and functionality over looks and cosmetics first.