CNC machine: first thoughts and project overview

Posted on January 11, 2012 in CNC

Over the course of the Spring 2012 semester, I will be pursuing one of the most interesting, ambitious and useful projects I’ve had the opportunity to work on yet – a CNC machine! Initially, this CNC machine will specifically focus on applications as a tool for Printmaking. The resident master printmaker at UNK, and truly talented artist, Victoria Goro-Rapoport, has asked that it be capable of creating light, yet intricate etchings in ~8.5×11″ copper plates, with the possibility of using other materials such as wood, plastic and linoleum.

What is a CNC machine?

In the past, shop tools such as mills, routers, lathes and more were operated solely by hand. While they still can be, and are, today, the rise of the use of semiconductors for digital circuitry and advances in electromechanical technology (servos) allowed for the automation of certain actions in machines. For example, if you have ever made several copies of the same object, you may have begun to notice a pattern or ‘rhythm’ to your workflow wherein you didn’t have to think as critically about what you were doing, since you’re just re-doing something you’ve done before. At a certain point, you could even go so far as to write down a procedure for producing that object, which you could pass on to others (“Drill a hole here, then move the piece so you can drill another hole here…”).

Now if you connected each of the moving parts of your machine to powerful motors, you could write a computer program to tell these motors those instructions, and watch as it creates the object you told it to. This is really the essence of what CNC is all about: adding motors to existing machines so that you can make them perform actions for you.

Types of CNC machines
The term “CNC” can be applied as an adjective to nearly any kind of machine used in workshops. The trick is to use the correct term to describe your machine, which is something I am still learning. There are several different kinds of CNC machines that I am specifically interested in researching for this project, not all of which are mutually exclusive. In other words, the machine I end up building may be capable of performing several of these actions to various degrees.

  • router: creates deep cuts in, or through, materials like wood and plastic. More information.
  • mill: cuts away material from solid blocks of metal, much the way a stone sculpture cuts or chips away stone from a single piece (subtractive process). More information.
  • plotter: a moving gantry that carries an implement, sometimes a pen or a rotary tool, across a flat surface. More information.
  • 3D printer: essentially a plotter with an exaggerated Z-axis (up-down motion), and with a heated extruder instead of router bit or cutting implement. More information.

Example machines:

Why build a CNC machine?

Beyond simply the ability to accurately reproduce your work, CNC machines also enable you to exceed human abilities in some areas. For example, one could use CNC technology to construct their own 3D printer, which would be capable of building plastic forms that are too intricate or precise to produce by hand. Master craftspeople and shop technique purists may balk at such a suggestion, but I’m specifically thinking about hobbyists and DIY contexts, where many years of finely honed skill may be extraneous or otherwise out of the reach of the operator. I’m interested in using CNC technology to enable novel experimentation, rather than substitute for skill.

The particular CNC machine I am looking to build will be initially used for Printmaking applications, such as etching designs in copper plates and routing/milling designs in MDF, acrylic and possibly other materials. The act of doing so should also result in a CNC machine that can reasonably perform other applications, beyond Printmaking, such as cutting custom gears, flat-pack object design and much more.

Much more information will come over the next few months, but I wanted to get the initial picture in your head about what CNC is, and why I’m pursuing it.

Relevant resources

Related projects

Luckily, I don’t have to dream up this entire project myself, but can instead make my own interpretation based on existing open-source projects! Here are a few related projects I’ve found across the web in the last couple months, each of which offer plans or help in some way:

Project phases overview

Research
Acquire information and gain insight about the general mechanics and operational theory of CNC machines in general, as well as basic introductory information about traditional printmaking processes and techniques. I’ll publish as much of this information as I can to this blog, in the form of a series of informational articles like this one.

Design
Work with Printmaking to define a set of requirements that the CNC machine should be capable of, including physical parameters such as required accuracy, work area size, target materials and so on. At the end of this phase, I should be able to work up a tentative bill of materials (BOM) with part names, quantities, prices and sources to get the project started.

Acquisition of funding
Do whatever I can to acquire funding using any means available. This phase may be more difficult than it should be, as there is very little financial support for student work, especially in the technology fields, at my university. I have a hunch that it may ultimately take more than a few months to acquire necessary funding, but I’m still going to get it a shot, and document the process.

If adequate money cannot be secured in this phase, the project will either focus on scavenged materials and documentation, or on just partially completing the project, which should make it easier to get more funding.

Construction
Once the design phase has been complete and at least partial funding has been secured, I can begin building the CNC machine as per the design I generate earlier in the semester. I will most likely be following a careful, iterative process for construction, whereby small sub-systems are independently developed, then synthesized over time, with tightly integrated testing and quality assurance as I go.

By following an iterative process, I should be able to have reasonable progress to show regardless of the amount of funding ultimately secured for the project. For example, I may start with acquiring decent stepper motors, drivers and electronics, then figuring out how to couple the threaded rods to the shafts of the motors and getting reliable motion to occur. Then I can construct a simple gantry and attach it to the threaded rods, and try to get it to move reliably, and keep adding bits and pieces from there.

Testing
Obviously it is in my best interest to test each and every sub-system as I go, but eventually there will be times where entire systems can be tested together. For example, just because I’ve shown that the X axis and the Y axis work well independently doesn’t mean that mechanical noise or issues won’t occur when they are used together. For this reason, I will execute ‘high-level’ tests each time sub-systems are added together.

Documentation of example uses
Of course, just constructing a CNC machine isn’t enough for me, I want to also get real use out of it. Furthermore, just delivering a working, or partially working, prototype to professional and student artists and saying, “Well, there you go!” is not particularly helpful or ethical. Therefore, I plan to use the CNC machine to execute at least one series of successful prints using whichever process it ends up being best at, and use that process as an opportunity to document everything I can think of. This way, future students and faculty can reference my work and learn the basics of how to use the CNC machine without having to reverse engineer anything. Furthermore, if time permits I would really like to develop a series of workshops, lessons and/or demonstrations that explain the CNC machine and how it can be used by students and faculty.