You can’t avoid CNC these days. I’ve managed to produce some pretty complex components with an angle grinder, welder and a spare afternoon but, if you want to produce a top quality part, you have to go CNC.
It’s been my plan to build a CNC plasma cutter for some time now but, the truth is, I don’t have any real experience with the electronics and mechanics involved; yet. There are many articles out there of people who have taken the plunge and just learnt as they went along but I have so many projects there is little time left for another big build.
As a halfway house I decided to buy and build a 3D Printer kit. The printer includes a lot of the same components the plasma cutter will need (stepper motors, drivers etc.) giving me the opportunity to learn some machine design, and I also get a 3D Printer at the end of it.
I put the machine together in my evenings over a busy October and managed to successfully print the test model. However the next big step was to design something I actually needed, build the appropriate tool chain, and successfully print it .
The Fuel Pump Bracket
I’m converting my 80’s daily wagon over to fuel injection for a bit of fun and added fuel economy. The high pressure fuel pump for the system needs to be mounted in the bay along where the ignition coil used go; this required a custom fuel pump bracket. While I would usually fold something up out of thin steel or thick aluminium, I have a 3D Printer now and I’m going to make use of it.
To begin with I took the measurements I needed from the fuel pump (60mm diameter) and the mounting holes on the car and roughly drew my plan in my notebook. Then I used <insert generic 3d CAD software> to model it. One of the many great things about 3D printing is that you can easily add the space for captive nuts and counter sunk bolts into your design, at the cost of little-to-no extra manufacturing time. My fuel pump bracket uses three M4 bolts to tighten onto the pump and these are neatly sunken into surface.
Using a “Slicer” program I turned the STL model file into G-Code for the machine to understand (Slic3r). You can set your material density, resolution and supporting material with this software, and I found it to be very flexible.
I received 100m of white filament with the machine so this is what I have been using for my prints. Black would look a bit nicer but until I have some more experience I’ll stick with the standard stuff. This turned out to be a good idea as my first try at printing failed after 10 minutes. If you look at the pictures on the left you can see that I didn’t specify enough infill density, so the internal structure was too open; this lead to warping and separation from the print bed.
For round two I went up on the internal density and used a 10mm brim on my print to make sure it would stick to the bed. This greatly improved the quality of the print and ultimately it was successful. However it was soon clear that I had gone overboard on the resolution settings, and material density, leading to a print time of over 9 hours! I left the machine working over night while I dreamt of future plastic parts.
The final component is gorgeous, but completely overkill. I could have halved the material density and removed a lot of excess material from the design. That said, I am confident it will do its job for many thousands of miles. With a splash of Matt Black paint I reckon it will look like a production part.
Next job: A 3D printed throttle cable bracket.