CNC Router Electronics Upgrade

I will be testing a new electronics package for my CNC router. I’ve had these components for some time now but haven’t prioritized setting them up until now.

Back when I first designed my CNC router, Leadshine drivers were significantly more expensive than the Gecko G540 that I ended up using. They have since become an attractive option, so I have been wanting to try them out. I am also interested in testing a toroidal power supply, using the Mesa 7i76e again, and seeing how the Raspberry Pi 4 works as the control computer running Linux CNC.

The existing electronics will be left as-is except for the addition of disconnects that will allow easy swapping between the two configurations. 

The existing configuration is this:

  • 7.3A 48 vdc switching power supply
  • Gecko G540 4-axis stepper driver
  • Desktop computer running LinuxCNC
  • Parallel port interface to the G540
  • Tested a Mesa 7i76e ethernet FPGA board in place of the parallel port interface

The new configuration:

  • Toroidal 48 vdc power supply 
  • Leadshine AM882 stepper drivers
  • Raspberry Pi 4 running LinuxCNC
  • Mesa 7i76e FPGA board (with ethernet interface to PC)
  • 24 vdc switching power supply for the 7i76e board and for field power for all the I/O.

The machine itself is not changing (steppers, homing switches, etc.)

I’m also designing an electronics cabinet that will hold all the components for the new configuration.

I started this project by laying out all my components on a table and coming up with a rough layout and footprint. Next, an electronics box was mocked up with some scrap wood to better understand the sizing, layout, and wire routing. 

As a result of this mock-up, I figured out what to do differently and created a solid model of the new design. 

I will build this new design later. For now, I just want to get all of the electronics up and running and work out any other issues that may come up.

I decided to try out the Raspberry Pi 4 as the controller computer since I had one laying around and I see there is now an official LinuxCNC build for it. I also didn’t want to change the configuration of my existing CNC PC, so I can plug it right back in to the G540 if I run into issues getting this new configuration working.

I took notes on the process and documented it in this setup guide for the Raspberry Pi 4 with LinuxCNC and Mesa 7i76e.

Happy Pi Day

Since my wife is a high school math teacher, I thought it would be fun to do a little project with her for Pi Day. Using Fusion 360, we worked on the design together, and then created the CAM setups. We did a few engraving tests with various bits and depths before attempting to make the piece with a 30 degree V carving bit. It turns out a 60 degree bit would probably have been best, so we’ll have to try again once we get a 60 degree bit. It turned out pretty well though and we had a lot of fun making it!

Pi Shape Cutout on Router Table

Pi shape with engraved digits

Introduction to CNC Router Project

Intro

I have always enjoyed learning new things and thinking about innovative solutions to a wide array of problems I encounter in life.  Many of the ideas and subsequent solutions have seemed viable, but would require resources that were not available to me to implement the idea.

In the back of my mind, I’ve always been intrigued by the thought of having a CNC machine at my disposal. This would help me to bring my ideas to life.  Seeing stories of other people building their own low-cost machines tempted me over the years to do the same.

After years of reading/dreaming about it and gradually learning, one day I decided to seriously research the options.  I looked at buying one of the hobby machines that have been popping up on the market in recent years, buying a diy kit, buying plans, or following one of the free open source projects to build my own CNC router.

In usual fashion, I spent a few months studying all of the specs, pricing out each option, and reading hundreds of forum threads, articles, and reviews.  It was quickly apparent that I could not afford to buy a machine, or at least a machine that had the performance I required.  Kits and open-source machines were not much better for affordability, but plans offered a lot of bang for the buck.

Researching CNC Router Plans

Quite a few plans were available, so I dug in to comparing them all.  In the process, I read many accounts of people who built machines based on the plans, those who modified the plans and those who upgraded their machines after not being satisfied with the initial results.  In addition, I happened upon people who designed their own machines altogether, which planted an idea in the back of my mind.

Once I had gained enough knowledge to evaluate different designs, features, and the resulting performance, I realized that none of the plans would satisfy my needs as-is.  However, they could probably be modified to do what I wanted at an acceptable price point.  After a lot more research (see the trend here?) I got to the point of feeling comfortable looking at any CNC machine, including the commercial models, and evaluating the design decisions and understanding their weaknesses.  It was then that I realized I could design my own machine and probably end up with a better product than anything currently available at a given price point.

A New CNC Router Design is Born

To confirm my thoughts, I made up a quick Bill of Materials and researched the prices of all the individual parts and raw materials that would be required.  This further cemented the idea that I could design and build a machine that would come in at the right cost, and likely with great performance too.

For the next 3 months, I researched CNC design, studied mechanical engineering, compared products, part manufacturers, parts suppliers, and started formulating a design.  I also knew that once I had a working CNC machine, I would have to learn CAD software to create the designs that the machine would produce.  I decided to jump in and learn solid modeling to design the CNC machine.  I compared all the CAD options and settled on Autodesk’s cloud based Fusion 360 software.  It was offered free to hobbyists and small businesses, and has comparable functionality (at least from a beginners view) to the industry standard SolidWorks, which I couldn’t afford.

In December 2015, I installed Autodesk Fusion 360.  Through reading the educational materials and following the tutorials I was able to quickly learn the software.  By the end of the month I had a rough conceptual model of a CNC machine, rendered beautifully and quickly in the cloud by Autodesk’s servers.  Over the following 6 months I went through many iterations of the design, gradually refining it and converging on an optimal solution to match my budget and performance requirements.

Once I felt the design was getting close, I learned to use the Simulation functions in Fusion 360 to perform stress analyses and deformation tests in order to find the weak points of my design.  It was a relief to see that the results of the stress analysis and cutter deflection simulations were in line with the calculations I performed during the initial design stages.  A few more tweaks to the frame components yielded a design that should meet the design goals and performance requirements.