CNC Basics: What Is CNC and Where Do I Start?

Posted On Mar 09, 2013 By Nate Lowrie

At Fine Line Automation, we're very enthusiastic about CNC tools and automation.  Our parts and kits make the things people dream up everyday a reality.  They will help you produce more projects in less time with better results; in a production setup, CNC tools will pay for themselves many times over by increasing the efficiency and quality of the operation. Before you set off on the wonderful journey that is CNC, we would like you to consider the rest of this article.  We want you to be satisfied with your purchase and the results it gives to you.  Our goal is for our tools to be easy for to use and for you to be excited to with CNC.  The best way to achieve that is to give you the knowledge you need to select, build, run, and troubleshoot a machine. Let's learn a little bit about how CNC can help you take your projects to the next level.

What is CNC?

At it's core, the CNC router is basically a robot controlled by a computer.  The computer tells the router to move a cut bit through a material in a precise pattern, cutting out whatever you designed.  CNC routers take material away with a cutting bit to create the final product, like a saw or a drill press.  Because the router is moved in a precise manner, it can create things like lettering or carving that very few people can do by hand.

Most of us, myself included, are not well gifted for creation. Many times, I go to a show like the Maker Faire or look online and see a gorgeous or technically amazing piece of work that just drops my jaw, especially when it is done with hand tools. I started really making things in college. Pursuing an engineering degree makes you dream up all sorts of items you want to make. I had wanted to make robotics. I had the aptitude and tools to do the electronic portion, which is what I pursued in school. However, most of my projects failed because I didn't have the knowledge and tools to make the mechanical portions like the chassis and drivetrain (this was before pre-assembled drivetrains were readily available). I had tried to fabricate parts and came up with ugly, non-fitting parts and couldn't make it work. Same thing with woodworking and furniture. I would dream up projects all the time that I want to make, but couldn't make them because I didn't have the skills necessary to do so with the tools I had.

All that changed with the CNC router. Now, I just design the parts on the computer, something I was already doing anyway, and then after some brief setup I press go on the machine and it cuts out the parts. I am now able to focus on the parts of the projects that I like the most (the electronics and software) while making sure the mechanical pieces turned out fantastic. My skills were no longer the limitation because the computer controller router was 100 times more precise than I could ever hope to be. I just had to tell it what to do and where to go.

To Build or Buy?

In 2008, I decided to pull the trigger and build a CNC router, the very first FLA100 prototype. I had considered buying one but at $5,000+ for an entry level router I just didn't have the cash to spend as a hobbyist. Back then, building a CNC was a real exercise in engineering. The current components, plans, and kits available from companies today were in their infancy back then. Most of the successful builds involved creating many custom parts with non-metallic materials like plastic and wood.

Nowadays, building a machine is as easy as buying a kit. We have largely taken the hard parts, the engineering and part fabrication, and offered them in ready to by packages. No longer do you need to worry about designing every part to line up properly, sourcing parts like bearings and fasteners from multiple sources, and fabricating pieces. It's as easy as taking parts have been tried and tested in hundreds of machines and bolting them together to get a precision high performance machine.

How can a CNC help me to create the projects I want to build?

Let's look at the first project I built with the CNC as an example to how a CNC Router can help you build your projects. My first project just happened to be a small chassis for robot.  I had a couple of requirements:

  • Have mounting holes for a small powertrain and for a front axel/wheels.
  • Have mounting hole for an electronics board that would control the robot.
  • Have mounting holes for 2 sonar probes that would point them at precise angles.

The first thing I always did was start designing the part in a CAD program. I knew the mounting hole dimensions/locations and was able to put those onto my chassis plate and then move the pieces around until the layout worked. If I didn't design in CAD first, there is a good chance I would have drilled the holes and had to move the mounts later on. Things like rotating the mounting holes for the sonar probes to a precise angle are trivial with CAD and the CNC. I realized I would also have to deal with the wheels. The electronics board footprint was wider than the wheel base so I couldn't hang the wheels over the edge. I ended up adding some pockets in the chassis that the wheels would sit in. Total time layout everything out: 20 minutes. I put a piece of plywood on the machine and 15 minutes later I had a fully functional chassis.  With one bit, I had bored 4 different sizes of holes, cut square pockets, and cut out the chassis profile. I will also add the quality was much, much better than anything I could have created by hand (I had tried this particular project before with dismal results).

Now, if I was building this chassis manually, I would have marked all of the different mounting hole groups on the computer and printed them out on a piece of paper.  Then, I would have taken my piece of wood and papers and arranged them till I had a satisfactory arrangement. Oddball alignments like the precise angle of the sonar blocks are hard to get right and need to be double checked with a protractor. After double checking the alignment was straight, I would drill the holes on the drill press, aligning the holes on the center points of the circles on paper.  The holes were 4 different sizes so I needed to change the bit in the drill press 4 times. Then, I would need to setup the router to create a slot or a pocket for the wheels. The first attempt at the chassis took me about an hour and a half to fabricate.  During the drilling, one the papers shifted an I spent another 20 minutes repairing the hole that was off.
 

As you can see from above, CNC offers a significant time savings, which only increases as the number of parts in a project increases. You can generally eliminate errors and have most parts fit correctly and snug the first time. The accuracy of the part also significantly increases. The accuracy was extremely important for some components. With manually built chassis, the sonar probes were always off slightly, maybe 1/2 degree.  This is significant enough that I needed to build some error correction into the code. The chassis created with the CNC had no such issue.

If I am a woodworker with traditional tools, how can a CNC improve my workflow?

A seasoned woodworker will already have a variety of tools at their disposal. A decent shop will most likely have a tablesaw with a variety of sleds and jigs, a router table, a drill press with a table, and a jointer. All of this equipment comes into play when creating something like a drawer.  For a drawer, you have a bottom, 4 sides, and a front face. Let's assume that we are creating a typical rabbit and dado drawer. The order of operations would be something like this:

  1. Run the boards on a jointer to get an flat edge to run against the table saw.  
  2. For each of the 6 parts, cut them to size on the table saw with a minimum of 2 cuts per piece (rip and cross cuts).
  3. Create the dado for the drawer bottom on each of the side pieces. This involves setting up a dado blade or using a router table to create the dado.
  4. Do the rabbits on the side pieces with the same equipment used in step 3.
  5. Do a round over on the front face with the router.
  6. Drill some holes for the handle on the drill press.

This is a pretty standard set of operations. Now compare that to using a CNC machine. We will use a bigger board and have the machine cut all of the pieces from the board all in one go.  In cutting the outside profiles, we have eliminated the joint and the table saw operations.  We will also cut all of the rabbits and dados on the machine, eliminating a good chunk of the router table operations.  We could do the round over on the machine, but without an automatic tool changer it's quicker to just do that portion with the router table or a hand router.  We can however drill the handle holes and eliminate the drill press operations. So, the CNC operation boils down to:

  1. Load part onto the machine.  Define work zero.  Load G-Code file. Press Cycle Start.
  2. Unload parts. Lightly sand edges and clean up tabs.
  3. Roundover drawer front with a hand held router.

For a normal sized CNC drawer like this, it takes about 30 minutes to setup the machine and cut out the parts.  How long would an operation like this take you?  Now multiply that by the amount of drawers you have in that project.  Now factor in the time savings you will receive by starting the assembly of the first drawer while the machine cuts the second drawer.  You can see how quickly the time savings start to add up.

In addition, a CNC also allows you to get rid of a few machines. Traditionally, the bulk of the work I did was on the drill press, table saw, and router table and as such those were shop centerpieces with fairly big bases. I no longer use and got rid of my floor standing drill press, replaced the cabinet saw with the big permanent outfeed tables with a small contractors saw that is put onto a shelf, and replaced the router big cabinet with a portable bench top version. If you are just starting out in woodworking, the cost of these machines plus all of the accessories like dado blades and jigs is better than half the cost of one of our router kits. For a few hundred more, you can have CNC machine and still be able to build all of the projects a traditional woodworker could.

How can a CNC enhance my projects?

Unless your a master craftsman, a CNC should make the part better than you otherwise could yourself. Besides the time savings and increased quality, the CNC can greatly expand the number of operations that you can actually do.  Let take a look at the drawer project and see what we can do to enhance the project.

One of the operations the CNC does really well that is really hard to do with traditional power tools is carving.  Whether it's carving floral accents on the drawer face, a name to personalize something, or letters to identify the contents of the drawer, the CNC does it just as well as operations like drilling.  You can get 3D carving model that incorporate into you projects with just a click or you can create your own. Imagine how easy it would be creating a sign for your child's room or a plaque for a retiring co-worker.

The other operation the CNC does really well that is really hard to do with power tools is cutting odd profiles and shapes.  Suppose you want to put a round semi-circle at the top of the drawer face.  With traditional power tools, this requires special jigs or great skill with a bandsaw or scrollsaw. With a CNC, it's as easy to cut this profile as it is to cut a square. Imagine how easy it would be create a cutting board in the shape of Texas or a decorative wine rack that looks like a cactus.

A CNC also makes decorative joints like box joints and dovetail joints possible without specialized equpiment.  We used the rabbit and dado drawer as an example because it's easier to create by hand.  If you want to do dovetails by hand, you need a templating system or great patience with a ruler, pencil and chisel. With the proper setup you can do these joints directly on the router just as easily as rabbits and dados.

This sounds good, I really want a machine, but I have no experience and am new.  How hard is it to get started?  Where can I get more info?

First, the obligatory warning.  Like any machine, a CNC router is inherently dangerous, especially when misused.  Please wear proper protection and use common sense. Please make sure that you familiarize yourself with the machine and that you do not leave it running unattended, especially if this is the first time you are running a particular G-Code file. Likewise, we are not responsible for a sour relationship with a significant other as the result of an obsession with CNC.

To start utilizing CNC, you don't really need much experience.  If you can put together furniture, you can build our kits and have arguably the most useful tool you will ever own.  There are instructions for assembling our kits and using them to create your first part.  If you have no clue what I mean if I were to mention G-Code, work offsets, and feedrates, then you can find more info on these CNC basics at our ever increasing library of CNC basics articles.  Even if you have used a CNC before, some of the more advanced topics we cover like calculating proper chip loading and electronic probing might be of interest. If you want a more technical and historical perspective, wikipedia has a wonderful write-up. If you still have questions that are not answered, feel free to contact us and we can provide you additional information.

The more familiar you are with these concepts before you start your projects, the better your projects will be. In addition to the info, you can familiarize yourself with the machine with one of our featured projects. The toolpaths are already generated and the projects are as ready to cut as possible. These projects will walk you through every step, include verifying the toolpaths and feedrates, selecting bits and material, work hold-down and machine setup, cleaning the parts, and final project assembly and finish. Making one is a good way to gain valuable tips and experience to take your own projects to the next level.



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