Woodworking With A CNC Router: The Only Guide You Need

By Gerda Feldmeier-Bold, WikiCommons

CNC routers have become increasing popular over the past couple of decades for a number of reasons. One reason is due to the low cost to design and create one. It was not that long ago that the CNC routers were only owned by large corporations. Nowadays, it’s becoming more and more common to see weekend woodworking hobbyists build a small CNC router in their garages.

Another advantage that has caused their popularity to grow is the fact that the software needed to operate them has become increasingly easy to learn. In the past, a CNC operator would need a significant amount of training. That training is only on the operation of the machine. It does not include the training and expertise needed to actually create the computer file needed which tells the router what to cut.

In the article below, I will give cover how a CNC router works, what you can do with one, and how you can go about acquiring one!

Terminology

The first place we need to start in our quest to learn about CNC router’s is to understand some of the basic terminology that is often used with the machine. The first term we should cover is CNC. It stands for Computer Numerical Control. This is a fancy term that basically means a computer is used to tell a machine, in our case a saw, drill or router, to cut a predetermined shape, design or hole. Once the machine setup is completed by the operator, the computer takes over and performs all pre-programmed cuts.

Photo by By S zillayali, WikiCommons
Photo by By S zillayali, WikiCommons

The computer programming and design that is needed to create the files that are sent to the CNC machine is often referred to as CAD software. CAD is an acronym for Computer Aided Drawings. Up until the past 20 years or so, CAD design had been limited to those who could afford expensive software programs. In addition, the best training available was at local technical schools or community colleges which offered Associate degrees in CAD design.

Today, this has changed. You can still obtain a degree in the subject and that degree will certainly help you. However, the increase in training videos on Youtube and other platforms has made learning CAD design much easier for those not interested in obtaining a degree.

In addition to training becoming more available to the average user, the CAD software itself has become more widely available which has dropped the price of it. In fact, in the year 2000, a free CAD program that was named Sketchup was released. In 2006, Google acquired the software which quickly made the free program available to millions of users around the world. Today, the program goes by the name SketchUp Make. There’s unlimited amounts of free training online. There’s also a highly popular marketplace where users can share creations with one another.

How does a CNC work?

As you’ve probably already gathered, operating a CNC machine requires the user to be experienced with operating computers. Below is a general outline of how a CNC router works and the steps required to create something using one.

CAD Design

The first step in the process of cutting something with a CNC is creating a 3-dimensional object of the item you are wanting to cut. Your first reaction to that statement may be “That doesn’t apply to me because I’m only interested in cutting out signs with are 2D.” This is true. However, the material that you are cutting from is three dimensional. A 3D object is anything that takes of space in three directions. A flat sheet of paper takes up space in 3 directions. It stretches left to right, front to back and (although small) up and down.

Photo by By Imajin, WikiCommons
Photo by By Imajin, WikiCommons

If you are able to find a CAD file community like the one we mentioned above, it’s possible you can get by without having to actually create your piece from scratch in the software. This can be a great time saver. Using a CAD program for the first time will require some patience. It takes time getting use to seeing and moving objects around on 3 surface planes. If you are just starting out with CAD software, getting a couple files from a community can be a great place to start as it will let you manipulate the pieces using the various tools available in the program.

G-Code

Once you have created a 3D image of your item, you will need to convert it to a language that your router can understand. CNC routers operate using a language call G-Code. I like to think of G-Code like it’s latitude and longitude which you probably learned about in geography class during elementary school. It tells the router to move a certain number of steps (inches, feet, etc) in a certain direction.

To illustrate how CAD and G-Code work, imagine you are in New York City and want to go to Los Angeles.  You need to look at a map to get there. The maps represents the image that you created using the CAD software.

The directions you come up with to get you from where you are (NYC) to your end point (LA) is your G-Code. If written similar to what your computer deciphers, your directions would read, “move south 800 miles. Then move west 2800 miles.”

Fortunately, software has evolved significantly over the past couple of decades and there is software that can easily convert your image into G-Code. It’s developed so much, that this can be completed in a matter of just a few seconds. Back when CNC machines were first created, operators had to manually created the G-Code themselves. Instead of using computers, this was done using punch cards where holes were literally punched into paper and then fed through the machine. The holes told the CNC machine how it needed to move.

Depending on the size and detail of your project, it is not uncommon for a project to take 50,000 to 100,000 lines of code to perform all of the required cuts. Fortunately, the computer does all this for you. It will create quick and efficient tool paths that will ensure your cuts are completed exactly as you intended.

Machining

The last step in the CNC process is the actual cutting of material. This is the step where all your work on the computer finally comes to life and you can watch a blank piece of wood transform into the object you created. This step of the process is actually the easiest for the operator. At this point, it’s up to the computer to execute the code that the operate created. The operator will need to stay close to the machine to ensure it doesn’t encounter any problems, but for the most part, nothing should be needed outside of keeping the area around the machine clean.

Types of Machines

There are three different ways a CNC machine can operate. The first type is simply a drilling machine. Just as the description says, these machines are focused solely on making precise holes using a drill bit. These machines are common in companies that produce car parts. Using a CNC machine ensures holes are drilled in the same spots on every piece that passes through the machine.

The next type of machine is a CNC lathe. These machines work much like a regular wood turning lathe. The only difference is that a computer tells a computerized arm where to move along the piece of wood. It also tells it how much pressure to apply so it begins cutting away material. These setups can be excellent for people who create table legs or baseball bats. Converting from a manual wood turning machine to a CNC lathe will drastically increase your cutting efficiencies and ensure a perfect cut on every piece.

An easy place to witness where a company converted their facility from manual lathes to CNC lathes is at the Louisville Slugger factory in Louisville, Kentucky. They went from taking hours to cut a MLB baseball bat to a matter of minutes. In addition, they are now able to save each player’s bat specs so that they can ensure every bat they cut for a particular player is exactly the same.

The last type of CNC machine is certainly the most common one that you will see. This version is called a CNC router. The CNC router is the most versatile of the three. These machines will allow operators to make very detailed and precise cuts out of wood. In fact, even at a hobbyist level, it’s not uncommon to find topographical maps of an area cut from wood. Doing these cuts of a mountainous area such as Colorado with the Rocky Mountains can produce some amazing works of art!

CNC vs 3D Printer

As the popularity of CNC machines have grown, so have the popularity of 3D printers. Ten years ago, only a handful of people had even heard of a 3D printer. Now, it’s highly likely that everyone at least knows someone who owns one if they don’t own one themselves.

There’s often confusion between what a 3D printer does and what a CNC machine does. Here’s the easiest explanation I’ve heard. A 3D printer starts with nothing. As it runs, it begins printing and add material in precise locations. Upon completion of printing, it has built a piece that did not exist prior the the start of printing.

A CNC machine is the opposite. With a CNC machine, the user starts with a piece of material. That material can be anything such as wood, aluminum or steel. One the CNC machine begins executing a command, it begins removing material. Even if the command is as simple as drilling a hole, it’s still removing material. Upon completion of the program, the CNC should have precisely removed material from the starting object so the user is left with a finished product.

CNC Planes Explained

For me, understanding the three dimensional planes was one of the more difficult concepts when I first began working on a CNC. Personally, I think it’s easier to understand when sitting at your CNC machine. I found it more difficult to grasp once I started using CAD software which allows you to rotate and move an image into unlimited directions. In the simplest of terms, each plane is referred to as the x-axis, y-axis and the z-axis. Here’s a bit more detail on each:

  • X-axis – This axis is usually the largest of the three. If you stand in front of your machine, it will move to the left and right of your position.
  • Y-axis – Commonly the mid-sized axis. If you are standing in front of your machine, the Y movement will move your router towards and away from you.
  • Z-axis – This axis refers to the up and down movement of your router. For instance, let’s say you have a piece of wood that is 2” thick and you want to cut your name into it going a half inch deep. Your G-Code would need to tell your Z axis to move in a downward direction of half an inch.

Models Available

There is a wide range of CNC routers available for your workshop. Ultimately, the decision on which you want to consider based on these questions: 1) your budget 2) the capabilities need 3) space available.

If you are looking to acquire a CNC router to take your existing company to another level, (like the change that Louisville Slugger completed) you can easily spend anywhere from $50,000 to $250,000 or more. That price could go much higher based on what you are needing.

Photo by Tampere Hacklab
Photo by Tampere Hacklab

For this article, I’m assuming you are a weekend hobbyist looking into what a CNC machine is and deciding if it could help with some of your smaller projects. Pricing for a user of this level can start at as little as $700. Please note, that price is only for the machine. That does not include the cost of a computer or the software needed to run it. If you need a computer, that could add another $500 or more. Software needed to get you up and running can be found for around $250.

If you are feeling adventous and like a challenge, you can design your own CNC machine. Sites like Inventables.com and OpenBuilds.com have made it easy for users to create a CNC machine specific to their needs. This is a great option if you decide you want a bigger machine than what is on the market but don’t want to spend several thousands of dollars for a high end machine.

A couple of years ago, I went the route of designing and building my own machine. I was considering one of the kits that Openbuilds sells, but I was worried once I started using it, I’d want something bigger. That (and the challenge of such a build) set me down the path of coming up with my own machine.

Prior to this build, I had NEVER done anything like this in the past. It took me about a year of working on it off and on. My finished machine ended up with a cutting space of around 20″ x 42″. Going this route also allowed me to do a few one off upgrades that the kit machines didn’t have available.  I would caution you if you consider going this same route. You will be force to learn basic electrical wiring which was a bit nerve wracking for me at times. You’ll also need lots of patience! In the end, I’m glad I did it!

Upgraded Accessories

As with most machines and tools there’s always upgraded accessories available to make like easier. The CNC routers are no different.

Tool Changer

A very nice feature that can be found on a CNC router that will save a ton of time is a tool changer. If you have ever used or studied a router, you know that there are an almost endless supply of router bits available. Each of these bits create a different type of cut or design in the material. This does not change with a CNC router. It’s not uncommon to perform a cut that requires several tool changes during a project cutout. This is especially true if you are cutting a large piece of wood down into a piece that is very detailed, such as the topographical maps I mentioned earlier.

When I cut these projects, I always start with a clearing bit. These bits are designed to cut away substantial amounts of material very quickly. Then as I begin cutting more details areas, such as a valley or field, I switch to a smaller more detailed bit that removes less material at a time.

Typically, this bit change will take a couple of minutes to perform. There’s also the risk of me not aligning the bit correctly before starting the next series of cuts. Worst case scenario, this could be disastrous and ruin my piece. Best case scenario, I have to spend an extra few minutes to check everything a few times to ensure everything aligns correctly.

A tool changer would fix all these issues! A tool changer will actually change the bits for you. During the CAD and G-Code creation phases, the operator tells the program that a bit change is required at a certain step. Once the CNC reaches that particular line of code, it moves the router over to the changer. The code then tells the router which bit it needs next. The tool changer then removes the current bit and replaces it with whatever is written into the G-code.

As you can see, this can be a huge time saver and help significantly reduce the risk of errors that may result incorrect cuts. If you are interested in buying a CNC with this feature, just know that it will significantly raise the price of your equipment. Typically, this feature is only found on commercial level CNC’s. The cheapest model that I could find with a tool changer was by Shop Bot and it was priced around $15,000.

Laser Cutter

Another nice add on that you is much cheaper is a laser cutter. These can be useful when cutting thin pieces of wood. Rather than cutting with a router bit which can sometimes be too powerful, a laser is used to burn thru the material. You can also use it to draw and inscribe wording onto a piece of wood as well. Many of these units will just attach to a stationary part of your router. You can pick up a quality laser for under $500.

CNC Safety

Just like with any power tool, there are safety considerations that should be put into place to avoid injury. Too many times, a woodworking accident with a power tool leads to an emergency room visit that requires stitches and sometimes even the loss of a body part.

Kill Switch

In my opinion, the most important safety feature you can install on your CNC router is a kill switch. You can choose to hard wire a kill switch into your electrical components or purchase a basic one where your router plugs directly into it which requires not wiring. The kill switch is important because if something goes wrong while your machine is running, you are able to hit a single button that will automatically shut the power off to everything on your CNC. This simple button has saved me several times from damage caused when I’ve incorrectly setup my machine.

Limit Switches

Another safety feature that I highly recommend is the installation of limit switches. These are simple little switches that are installed on your CNC that keep the machine from running further than a set distance. For instance, I mentioned earlier that my Y axis has a cutting width of 20″. I have a limit switch in place so that if the Y axis tries to move more than 20″ it touches a button which will shut off the power to that motor and trigger an on screen error message.

Some people will argue that limit switches are not needed. This is true – IF your machine is setup correctly and your CAD drawings are done correctly. If these two pieces are correct, you should know prior to your machine beginning to cut that it is going to try to cut an area that is beyond the cutting table. If you are new to CNC machines, this will take some time to get accurate each time. In my opinion, limit switches are a quick and easy install that provide you with a bit more safety to protect both you and your machine.

Other Safety Tips

The third biggest safety feature that you can use with your CNC machine is just basic common sense. Always keep your cutting table clean and free of sawdust. You will feel like you are vacuuming all the time, but that just means that you machine is cutting a lot of material for you!

Also, as tempting as it may be, DO NOT leave your machine unattended. Once your machine starts cutting regularly, your confidence with it will increase. At some point, you are going to start a cut and your software is going to show that you 45 minutes before it’s complete. You will be tempted to leave the machine and go outside to complete some yard work or go inside the house and relax. I highly encourage you to NOT do this. It takes just a split second for a bit to break or wood to splinter.

There’s also a chance the G-Code will error at some point which could cause random cuts to take place. If you are close to your machine, you will recognize the problem quickly and can react by hitting your kill switch. If you are away from your machine it may be several minutes before you realize the problem and by that time it may be too late to fix.