CNC machine update #1: early insights, design requirements and planning

Added on January 22, 2012

Over past couple weeks, I’ve been taking some time to pore over available resources on CNC technology and wrap my head around the basics of how these machines work. Although the world of CNCing is immensely complex, especially when the system is seem holistically with CAD and CAM software taken into account, there are nonetheless aspects of it that are accessible to hobbyists and DIYers. While my machine is still far from complete, I think I’ve made some key decisions worth documenting and discussing here.

Base plans for adaptation

In my previous post, I listed the Mantis 9.1 CNC machine as a possible source of information going forward. Since that last post, I dug into each of the resources I listed and tried to see which were the most complete and easiest to follow, and quickly realized that the Mantis 9.1 was exactly what I wanted to build.

The main advantages of the Mantis 9.1 CNC machine are that it is fairly well documented with video lessons and high-quality photos, can be built very cheaply and is simple enough that one can understand a lot about how the system works from the pictures alone. Furthermore, the Mantis 9.1 project includes a rough bill of materials, CAD files for the wood to cut, a small community and many important tips sprinkled in.

Design customizations and requirements
While the Mantis design looked like an ideal starting point for my project, a couple of changes would be required to make it perfect for my intended uses:

  • A larger workarea. Either 8.5×11″ (A4) or 11×17″ (A3), depending on price differences.
  • A more modular cutting/milling implement. I’m thinking a generic rotary tool will be good.
  • Re-design the Z axis to put the stepper motor on top of the assembly, where it can be screwed into place, rather than epoxied.

Collection of Mantis builds
The Mantis design has been used or adapted by several people all over the world, here are a few of the more fleshed-out sources I’ve found so far:

It would appear that Track Hacker has been a quality contributor to the effort, and has generated updated CAD drawings and a more up-to-date BOM for the Mantis.

Design update and construction plan

Also in my previous post, I outlined a 6 stage process for how I planned to pull off this project from start to finish. Now that I’m nearing completion of the Research phase of this build, and beginning the Design phase, I can now see the Construction phase with a little bit more clarity. Of course, I won’t be 100% sure about the construction until the design is complete, but I know enough to give a rough outline of how I plan to proceed.

Right now, I am drawing out my design, piece by piece, in my sketchbook by hand to give me a better understanding of each working system and force myself to think hard about every dimension and bit of data I can. So far, I’ve worked out basic designs for my Y axis, X axis, overall dimensions and Y axis platform. Once I’ve pored over the designs some more, I will likely transfer them to a CAD package to pretty them up a bit. Since I’m using Ubuntu 10.04 a lot these days, I will give both QCad and DraftPoint a try and see which one works the best for me. With any luck, I can take those CAD drawings and a chunk of 1/2″ MDO and get access to a CNC router in town to get the job done.

Tentative construction phase outline

  1. Acquire materials from BOM generated in Design phase.
  2. Cut the wood accurately to match the design. I’d like to use a CNC machine for this, but am not sure if I can find one in my town. This would require transferring my plans into a CAD package.
  3. Assemble and thoroughly test the Y axis by itself. If I can get the workarea platform to move smoothly and without jamming, then I know I can proceed with the X axis and, eventually, the Z axis.

Obviously, this outline will grow to include designing and constructing the X and Z axes, as well as extra features like end-stops, modular tools, homing functionality, electronics systems and software control. One step at a time!