Introduction: Tools and Materials for CNC
In this class, you’ll learn everything you need to know to design and create your own CNC cut projects, whether or not you’ve got access to a CNC router. We’ll learn some useful 3D modeling techniques, how to create joinery, and talk about equipment and materials.
CNC stands for Computer Numerical Control. Simply put, it is a machine with a tool-holding head whose movements are controlled by a computer. Laser cutters, water jets, and CNC routers are all CNC machines. 3D printers are technically CNC machines as well, but they have additive tool heads (adding layers of melted plastic) as opposed to subtractive ones like routers (subtracting from stock by cutting or carving into it).
CNC machines are controlled using a very simple programming language called G-Code. With a 3-axis CNC machine, the computer tells the head to "move in the X axis 2.1 inches"... "move in the Y axis 1.3 inches"... etc.
This computer control allows you to quickly and accurately cut out a wide variety of stock (wood, plastic, metal, etc.) in just about any shape you can imagine. CNC machines can carve complex 3D shapes, cut 2.5D contours out of panels, and even cut out fabric or leather with a drag-knife setup.
CNC allows you to create a design in your CAD software, create a CAM setup (Computer Aided Manufacturing), and produce a physical copy of your design very quickly. One of the added benefits is that you can change your design and update your CAM setup to improve on it. You can also produce multiple exact copies of the same object.
I think the CNC router is the most powerful DIY tool in the world. Although 3D printers and laser cutters are great for making all kinds of things, they're very limited when it comes to size and structure. With a CNC router and enough plywood, you can literally make a house. I made this 9' tall semi-permanent shelter for two campers using $250 worth of MDF, some flexible metal flaps, wood screws, and a CNC router...
PROJECT 2: Dining Table + Chairs
To learn the subject, we'll focus on flat-pack design by making a full-sized dining table. We'll design it in Fusion 360, a free CAD modeling suite complete with a sophisticated CAM environment. We'll make this project on the Shopbot CNC Router, a machine shop tool that can be found in maker spaces worldwide.
Finally, we'll get some practice with more complex geometry by designing a flat-packed dining chair to go with the table. Since we're using CNC, we can make as many copies as we want in no time!
Autodesk Fusion 360 (Free)
This is a powerful 3D modeling platform that's easy to learn but has endless potential. With it, you can design complex 3D objects for practically any kind of fabrication, digital or otherwise.
- Follow one of the links above to download the app (don't use the App Store on Mac).
- Enter your email and download the free trial.
- Install and setup a free Autodesk ID account.
- When you open Fusion, select the Trial Counter in the upper toolbar (it tells you how many days are left on your trial).
- In the next dialog box, select "Register for Free Use".
- Sign up as a Start-Up or Enthusiast (Free). You can also Sign up as a Student or Educator (Free) if you're a student or educator at a registered institution.
- Select the "I accept Terms and Conditions" checkbox and click Submit.
CNC Design & Fabrication Process
1. Design + Model
The first step is to create and model your design in CAD (Computer Aided Design). We'll do this in Fusion 360, which we'll introduce you to and provide download links for in the next lesson.
When you're designing an object that you intend to cut out with a CNC machine, it's very important to first know the following:
- What's the size of your CNC machine's table? The size of the table will limit the size of the stock you can cut.
- What's the size and thickness of your material? You will always need to know this, but it's particularly important when you're designing parts with joints that fit together.
- What's the length and diameter of your end mill? An end mill is a cutting tool kind of like a drill bit or router bit that's specifically designed for clean, precise cutting of specific materials.
When you start your design knowing these three things, you'll be able to make smart choices about how to design the object.
We'll also get into parameters in the Fusion 360 design. Parameters are just variables you can apply to any part of a model. In our case, we'll use them to establish the thickness of the stock for the table and chair projects.
2. CAM Setup
CAM (Computer Aided Manufacturing) involves taking one or more 3D objects and creating a G-Code tool path that will cut out or mill the parts as desired. Another reason we're using Fusion 360 is that CAM is built into the software, so all you have to do is switch from one workspace to another to work on the CAM setup.
You'll also be able to change a design, then update the CAM setup to work with the changes you've made. This makes it easy to experiment and improve your designs as you cut out parts.
3. CNC Machine Setup + Operation
With your tool paths finished, you'll learn how to safely operate both a desktop and full-size CNC machine for the best results in 2.5D cutting and 3D carving.
Other Machine Co. Othermill
Other Machine Co. makes a small, desktop CNC machine that I'll use in Lesson 5. It's made for PCB boards specifically, but it's a fully functioning CNC mill with a 2" maximum depth. It's great for small parts and a good option if you've got limited space.
Carbide 3D Shapeoko
Carbide 3D makes the "most powerful, most hackable, most complete" CNC machine in its class. This is a simple kit which you assemble yourself in about an hour. The machine must be plugged into a Mac or PC in order to run. All versions come with either a 1.25 HP Dewalt spindle or a Makita spindle. Fusion 360 includes a post-processor for these machines, so it's easy to make toolpaths and run them on the machine with good results. It's got a 3" Z travel, which is respectable for a machine of this size.
It comes in 3 versions:
- Cutting area: 16"x16”
- Footprint: 28-1/2”W x 24”L x 16”H
- Weight: 70 lbs
- Price: Starting at $1099
- Cutting area: 16x33”
- Footprint: 45”W x 24”L x 16”H
- Weight: 100 lbs
- Price: Starting at $1499
- Cutting area: 33x33”
- Footprint: 45”W x 40-1/2”L x 16”H
- Weight: 145 lbs
- Price: Starting at $1699
The Inventables X-Carve is a great choice for makers with limited space and a limited budget. It comes in 500 X 500 mm (19.5 X 19.5 in), 750 X 750 mm (29.5 X 29.5 in), and 1000 X 1000 mm (39 X 39 in) for $1,200, $1,350, and $1,460 respectively.
All models use a Dewalt router (which is easy replaceable) as the spindle and have a 65 mm (2.5 in) Z depth which is more than enough for flat pack projects and relief sculptures.
The company claims a .075mm - .13mm accuracy resolution, which is really impressive considering the price.
In short, if I were to own my own machine I would get the 1000 X 1000 version. You can do a lot with 39" of width, and you can cut longer sheets if you properly index and move the panels as demonstrated in this video.
For this class, I'll be using the ShopBot Alpha to demonstrate the work in the lessons. The ShopBot is a Computer Numerical Control router capable of cutting 2D and 3D shapes in wood, foam, plastic, some non-ferrous metals, and a variety of other materials. The ShopBot CNC machine I'm using in the lesson is considered full-size and can handle 4’x8’ sheet goods. It is a PRSAlpha 96 48 equipped with Z-axis travel of 12” and a 24,000 RPM, 3 horsepower Colombo spindle.
This machine can be found in maker-spaces worldwide such as Techshop.
You don't need a CNC machine to take this class or even to make CNC fabricated parts. Service bureaus are a great option if you don't have access to a machine. Here are a few to choose from.
Opendesk is similar in that it connects you with designers and makers, but they've also got a "Studio" section where you can post your design and have people vote on it. If your design gets enough votes, they'll fabricated and sell it and pay you commission!
End Mill for Small-Scale Carving
For the desktop CNC carving project, a ball-nose 1/8" end mill is a good choice. This type of end mill lets you get a smooth finish on a carving project because the round shape helps you avoid the stepping effect you'd get from a flat profile tool.
Amazon: 1/8" Ball Nose End Mill
End Mill for Plywood Cutting
To make a tool path, you have to know which end mill you're going to use. An end mill is a kind of router bit with properties that make it better at cutting for specific applications.
In my experience, the downcut spiral endmill is the best choice for flat-packed plywood furniture. The flute orientation gives you a clean top surface, and the bottom surface is compressed against the bed. This gives you clean cuts on both sides. The kerf does tend to get a bit gummed up, but you can always pause the job and clean out the chips and sawdust.
Onsrud is a great resource for endmills, but you can buy common ones on Amazon.
Amazon: 1/4" Downcut Spiral End Mill
Clamps for Work-holding and Assembly
I like the Irwin Quick Grip- it's very sturdy and easy to use. These are great for holding material if you don't have another hold-down system and they're crucial for sanding and assembly.
$17 Amazon: Irwin Quick Grip
These are an absolute must. You have to know the exact thickness of your material for any CNC project.
$17 Amazon: Electronic Digital Caliper
You'll need these for assembling flat-pack parts and for nudging large sheets into place on a full-size machine.
$16 Amazon: Dead-Blow Hammer
I've seen parts get jammed in the tool and fly across the room. ALWAYS WEAR SAFETY GLASSES.
$11 Amazon: Safety Glasses
Wood and Plywood
My advice is to locally source your wood- it tends to be cheaper than ordering online and you've probably got a mom-and-pop lumber yard you can support no matter where you are.
I'm using 3/4" A-grade maple veneer plywood for the flat-pack project. You can use CDX if you want, but the A-grade stuff is much nicer to work with and requires less finishing work.
I'm using Poplar for the carving project, but solid wood or plywood will work for this one as well.