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What do you need to know to CNC something?

Posted by Brandon Satterfield on

Running a CNC can seem complicated, let us demystify. 

You most likely see advertisements or social media post of CNC made stuff or the machines themselves. Maybe you work somewhere that has a machine shop, this does not necessarily mean they are CNC machines, but you are familiar with the fact they remove material to make something to drawing. 

CNC machines are often related to those big noisy knee mills or those oil covered machines to a person that has never been around the CNC world.                                                 


Did you know your paper printer could be related to a CNC? While not numerically controlled the principle is about the same. A program tells it where to go and it goes there. You get those pieces of paper out with what you ask it to put on there. 

CNCs are considerably more fun though.

How about the vastness of 3D printers that seem to be everywhere now? These machines are a CNC as well. 


So what exactly is a CNC machine? 

The official answer a computer numerically controlled machine

Unofficial, well a machine that you send a particular type of file to (Gcode) and get something you want.. or sometimes.... something you don't. 

OK - so to the heading what do YOU need to know to operate a CNC?

Amazingly this all broken down very easily. 

3 things you need to understand to "CNC"

1. You need a drawing, an idea, a model... basically something to CNC in an electronic format. 

How does one do this if you have never drafted before? 

Well this can be had pretty easily, but to truly get exactly what you want you will need to know how to CAD (computer aided drafting). Let us breach this topic and then move on to what to do if you simply do not want to learn how to be a drafter. 

I always tell people this can be the most frustrating part to newcomers. I have customers who buy our machines that are in their 90s. I find these guys the most interesting.. I hope I still have go juice in me at that age enough to learn new tricks!

If you are still able and wanting to take on a new challenge this is a great time to learn how to draft. I personally got my feet wet in AutoCAD. The program can be about as intensive as you could possibly want, but I have found as of recent it has really lost its luster of the olden days for a what a CNCr really needs. Although, if you are fluent in it and have a license this could be your gateway, move right on to part two.  

The new hot thing in drafting comes from the same company, autodesk. A cloud based software called Fusion360. There are several reasons a newcomer should start here, the main one is it is free to hobbyist. The software is not fly by night or stripped of all the goodies one needs, it is a very powerful tool that has unforeseen limits when one is starting out. That said, understand there is a steep learning curve, but there are libraries of YouTube videos out there of people simply out to help others!

On top of these things there is a CAM section attached (more on this in step two)

Another option for drafting is all the various freeware out there like google sketchup. While not the most powerful tool it is crazy simple to use. 

Last option is the one I personally use, this is not to say this is the best. Drafting can be liked to writing with your right hand. If you have wrote with your right hand most your life and switch to your left you can make letters but they look like crap and there will be a longing to grab the writing utensil with your right hand for the rest of your life. I am native in Solidworks. I cannot use Fusion360 for free as I am commercially tied to this stuff. Beyond that it simply feels wrong to me. My son is learning 360 and is getting pretty good in it, every time I grab his mouse to move an image things go the wrong way and I get frustrated. Like trying to write with my left hand. 

Now if you simply cannot CAD, does that mean you will never be a CNCr? NOPE, check out yeggi I can drop any model (for free) into the next operation (CAM). If I wanted to run a 3D printer this is a place I could go for ready made models as well. 

That is not all, if I am looking for simple 2D files to drop right into the next operation (again CAM, we will get there), I can just do a search for free DXF files. Again, I am not going to get exactly what I want but I can quickly be printing, laser cutting, plasma cutting, milling or routing without ever opening my drafting software.

2. CAM, changing your drawing into tool paths. 

CAM computer aided manufacturing, sounds much worse than it is. All we are doing here is setting tools to the drawing. There are no real short cuts here. Once you are accustomed to your CAM though this process literally takes longer to fire up the software than it does to spit out Gcode. 

We have a box we drew for example. 

Awesome and extensive I know! Let us say we want this rectangular shape out of 1/2" wood. We made our rectangle 1/2" tall and 2" x 3". How do we get that to the machine? Enter CAM.

First we need to save our drawing as a DXF or maybe as a 3D file such as an STL. DXF files are 2D shapes, here is our box in DXF and entered into our CAM program. Here I am using CamBam

In the CAM program we say that we want to use a 1/8" tool, go 1/2" down and how fast we want to go. Additionally, if we want the profile cut on the inside or outside. 

That is pretty much it. That is what CAM does. 

I mentioned Fusion360 had a nice CAM add on. I had to leave SolidWorks with my model (I do not like the plug in available for it personally) and go to another program, Fusion guys do not have to do this. 

There are multiple freeware CAM programs out there as well. My experience, you get what you pay for. 

So you created a drawing, and you added toolpaths, you will export the file from the CAM as Gcode which leads us to the third thing you need to understand. 

3. Machine and Gcode senders.

I get asked all the time if someone's machine (or even my machines) will do some task. 

Can a machine auto level my bed?

Does this machine do mesh 3D modelling?

Can the machine do automatic tool changes?

YES the machine a can do just about anything! Can the Gcode sender...?

I put the machine and Gcode sender together for things one should understand. This was on purpose, a Gcode sender is nothing without a machine, a machine is nothing without a Gcode sender. 

My R7 is probably the most bad apples hobby-grade machine on the market (I am a little bias) add all the electronics a great controller, super powerful spindle, all the limits and probing hardware, heck even add an auto tool changing head, then plug it up to a Gcode sender like CNC.js (great program, not banging it, it is simple and straight forward not to mention free) and my R7 is now a simple cnc router. 

Take this same R7 and hook it up to an extensive Gcode sender with crazy custom macros and the two look and act like different machines. 

Understanding a CNC is easy X,Y,Z, spindle or print head or laser.. well that is about it. Understanding your Gcode sender in combination with your machine.... now you have a tool. 

Gcode senders are normally tied to certain controllers. Want to use MACH, you have a certain set controllers you can use. Want to use LinuxCNC, same applies, like something like bCNC, you need a GRBL controller.. 

The Gcode sender will support a controller. The machine has motors, as long as your stepper drivers get the right signal, they do not care what is on the other side. I can drive my R7 with any controller, it just matters what Gcode sender I want to use. 

In my opinion these are the three things you need to understand about CNCs. CAD, CAM, and Gcode sender. 

I do not often suggest people go all out on the first CNC experience, go after combinations that you can easily understand. Try a few drafting softwares, try a few CAMs, most have free trials. Grab a machine that meets your needs, not that is the least expensive. Then, and only then can you grow and become a CNCing master!

  • CAD
  • CAM
  • Gcode Sender
  • 3 things to know about CNC
  • How to CNC
  • What is Fusion360
  • What is CAM
  • WHat is a Gcode sender